The initial symptoms of ARS usually include feelings of nausea and the urge to vomit. During the prodromal stage, individuals may also experience a loss of appetite and, in some cases, diarrhea, which can vary depending on the amount of exposure. These symptoms can manifest within minutes to days after being exposed to ARS.

Further Reading:

Radiation exposure refers to the emission or transmission of energy in the form of waves or particles through space or a material medium. There are two types of radiation: ionizing and non-ionizing. Non-ionizing radiation, such as radio waves and visible light, has enough energy to move atoms within a molecule but not enough to remove electrons from atoms. Ionizing radiation, on the other hand, has enough energy to ionize atoms or molecules by detaching electrons from them.

There are different types of ionizing radiation, including alpha particles, beta particles, gamma rays, and X-rays. Alpha particles are positively charged and consist of 2 protons and 2 neutrons from the atom’s nucleus. They are emitted from the decay of heavy radioactive elements and do not travel far from the source atom. Beta particles are small, fast-moving particles with a negative electrical charge that are emitted from an atom’s nucleus during radioactive decay. They are more penetrating than alpha particles but less damaging to living tissue. Gamma rays and X-rays are weightless packets of energy called photons. Gamma rays are often emitted along with alpha or beta particles during radioactive decay and can easily penetrate barriers. X-rays, on the other hand, are generally lower in energy and less penetrating than gamma rays.

Exposure to ionizing radiation can damage tissue cells by dislodging orbital electrons, leading to the generation of highly reactive ion pairs. This can result in DNA damage and an increased risk of future malignant change. The extent of cell damage depends on factors such as the type of radiation, time duration of exposure, distance from the source, and extent of shielding.

The absorbed dose of radiation is directly proportional to time, so it is important to minimize the amount of time spent in the vicinity of a radioactive source. A lethal dose of radiation without medical management is 4.5 sieverts (Sv) to kill 50% of the population at 60 days. With medical management, the lethal dose is 5-6 Sv. The immediate effects of ionizing radiation can range from radiation burns to radiation sickness, which is divided into three main syndromes: hematopoietic, gastrointestinal, and neurovascular. Long-term effects can include hematopoietic cancers and solid tumor formation.

In terms of management, support is mainly supportive and includes IV fluids, antiemetics, analgesia, nutritional support, antibiotics, blood component substitution, and reduction of brain edema.

When patients are exposed to the inhalation of combustion byproducts, they face the danger of being poisoned by carbon monoxide and cyanide. In situations where hydrocarbons and substances containing carbon and nitrogen are incompletely burned, the formation of both carbon monoxide and cyanide gas can occur. Individuals who inhale smoke are particularly vulnerable to this type of poisoning.

Further Reading:

Burn injuries can be classified based on their type (degree, partial thickness or full thickness), extent as a percentage of total body surface area (TBSA), and severity (minor, moderate, major/severe). Severe burns are defined as a >10% TBSA in a child and >15% TBSA in an adult.

When assessing a burn, it is important to consider airway injury, carbon monoxide poisoning, type of burn, extent of burn, special considerations, and fluid status. Special considerations may include head and neck burns, circumferential burns, thorax burns, electrical burns, hand burns, and burns to the genitalia.

Airway management is a priority in burn injuries. Inhalation of hot particles can cause damage to the respiratory epithelium and lead to airway compromise. Signs of inhalation injury include visible burns or erythema to the face, soot around the nostrils and mouth, burnt/singed nasal hairs, hoarse voice, wheeze or stridor, swollen tissues in the mouth or nostrils, and tachypnea and tachycardia. Supplemental oxygen should be provided, and endotracheal intubation may be necessary if there is airway obstruction or impending obstruction.

The initial management of a patient with burn injuries involves conserving body heat, covering burns with clean or sterile coverings, establishing IV access, providing pain relief, initiating fluid resuscitation, measuring urinary output with a catheter, maintaining nil by mouth status, closely monitoring vital signs and urine output, monitoring the airway, preparing for surgery if necessary, and administering medications.

Burns can be classified based on the depth of injury, ranging from simple erythema to full thickness burns that penetrate into subcutaneous tissue. The extent of a burn can be estimated using methods such as the rule of nines or the Lund and Browder chart, which takes into account age-specific body proportions.

Fluid management is crucial in burn injuries due to significant fluid losses. Evaporative fluid loss from burnt skin and increased permeability of blood vessels can lead to reduced intravascular volume and tissue perfusion. Fluid resuscitation should be aggressive in severe burns, while burns <15% in adults and <10% in children may not require immediate fluid resuscitation. The Parkland formula can be used to calculate the intravenous fluid requirements for someone with a significant burn injury.

Altitude sickness is usually experienced at altitudes above 2,500 meters (8,000 ft), although some individuals may be affected at lower altitudes. It is important to note that climbers in the UK, where the highest peak is Ben Nevis at 1,345 meters, do not need to worry about altitude sickness.

Further Reading:

High Altitude Illnesses

Altitude & Hypoxia:
– As altitude increases, atmospheric pressure decreases and inspired oxygen pressure falls.
– Hypoxia occurs at altitude due to decreased inspired oxygen.
– At 5500m, inspired oxygen is approximately half that at sea level, and at 8900m, it is less than a third.

Acute Mountain Sickness (AMS):
– AMS is a clinical syndrome caused by hypoxia at altitude.
– Symptoms include headache, anorexia, sleep disturbance, nausea, dizziness, fatigue, malaise, and shortness of breath.
– Symptoms usually occur after 6-12 hours above 2500m.
– Risk factors for AMS include previous AMS, fast ascent, sleeping at altitude, and age <50 years old.
– The Lake Louise AMS score is used to assess the severity of AMS.
– Treatment involves stopping ascent, maintaining hydration, and using medication for symptom relief.
– Medications for moderate to severe symptoms include dexamethasone and acetazolamide.
– Gradual ascent, hydration, and avoiding alcohol can help prevent AMS.

High Altitude Pulmonary Edema (HAPE):
– HAPE is a progression of AMS but can occur without AMS symptoms.
– It is the leading cause of death related to altitude illness.
– Risk factors for HAPE include rate of ascent, intensity of exercise, absolute altitude, and individual susceptibility.
– Symptoms include dyspnea, cough, chest tightness, poor exercise tolerance, cyanosis, low oxygen saturations, tachycardia, tachypnea, crepitations, and orthopnea.
– Management involves immediate descent, supplemental oxygen, keeping warm, and medication such as nifedipine.

High Altitude Cerebral Edema (HACE):
– HACE is thought to result from vasogenic edema and increased vascular pressure.
– It occurs 2-4 days after ascent and is associated with moderate to severe AMS symptoms.
– Symptoms include headache, hallucinations, disorientation, confusion, ataxia, drowsiness, seizures, and manifestations of raised intracranial pressure.
– Immediate descent is crucial for management, and portable hyperbaric therapy may be used if descent is not possible.
– Medication for treatment includes dexamethasone and supplemental oxygen. Acetazolamide is typically used for prophylaxis.

The desired core body temperature when cooling a patient with heat stroke is

Heat Stroke:
– Core temperature >40°C with central nervous system dysfunction
– Classified into classic/non-exertional heat stroke and exertional heat stroke
– Classic heat stroke due to passive exposure to severe environmental heat
– Exertional heat stroke due to strenuous physical activity in combination with excessive environmental heat
– Mechanisms to reduce core temperature overwhelmed, leading to tissue damage
– Symptoms include high body temperature, vascular endothelial surface damage, inflammation, dehydration, and renal failure
– Management includes cooling methods and supportive care
– Target core temperature for cooling is 38.5°C

Heat Exhaustion:
– Mild to moderate heat illness that can progress to heat stroke if untreated
– Core temperature elevated but <40°C
– Symptoms include nausea, vomiting, dizziness, and mild neurological symptoms
– Normal thermoregulation is disrupted
– Management includes moving patient to a cooler environment, rehydration, and rest

Other Heat-Related Illnesses:
– Heat oedema: transitory swelling of hands and feet, resolves spontaneously
– Heat syncope: results from volume depletion and peripheral vasodilatation, managed by moving patient to a cooler environment and rehydration
– Heat cramps: painful muscle contractions associated with exertion, managed with cooling, rest, analgesia, and rehydration

Risk Factors for Severe Heat-Related Illness:
– Old age, very young age, chronic disease and debility, mental illness, certain medications, housing issues, occupational factors

Management:
– Cooling methods include spraying with tepid water, fanning, administering cooled IV fluids, cold or ice water immersion, and ice packs
– Benzodiazepines may be used to control shivering
– Rapid cooling to achieve rapid normothermia should be avoided to prevent overcooling and hypothermia
– Supportive care includes intravenous fluid replacement, seizure treatment if required, and consideration of haemofiltration
– Some patients may require liver transplant due to significant liver damage
– Patients with heat stroke should ideally be managed in a HDU/ICU setting with CVP and urinary catheter output measurements

Hypothermia occurs when the core body temperature drops below 35°C. It is categorized as mild (32-35°C), moderate (28-32°C), or severe (<28°C). Rescuers at the scene can use the Swiss staging system to describe the condition of victims. The stages range from clearly conscious and shivering to unconscious and not breathing, with death due to irreversible hypothermia being the most severe stage. There are several risk factors for hypothermia, including environmental exposure, unsatisfactory housing, poverty, lack of cold awareness, drugs, alcohol, acute confusion, hypothyroidism, and sepsis. The clinical features of hypothermia vary depending on the severity. At 32-35°C, symptoms may include apathy, amnesia, ataxia, and dysarthria. At 30-32°C, there may be a decreased level of consciousness, hypotension, arrhythmias, respiratory depression, and muscular rigidity. Below 30°C, ventricular fibrillation may occur, especially with excessive movement or invasive procedures. Diagnosing hypothermia involves checking the core temperature using an oesophageal, rectal, or tympanic probe with a low reading thermometer. Rectal and tympanic temperatures may lag behind core temperature and are unreliable in hypothermia. Various investigations should be carried out, including blood tests, blood glucose, amylase, blood cultures, arterial blood gas, ECG, chest X-ray, and CT head if there is suspicion of head injury or CVA. The management of hypothermia involves supporting the ABCs, treating the patient in a warm room, removing wet clothes and drying the skin, monitoring the ECG, providing warmed, humidified oxygen, correcting hypoglycemia with IV glucose, and handling the patient gently to avoid VF arrest. Rewarming methods include passive Rewarming with warm blankets or Bair hugger/polythene sheets, surface Rewarming with a water bath, core Rewarming with heated, humidified oxygen or peritoneal lavage, and extracorporeal Rewarming via cardiopulmonary bypass for severe hypothermia/cardiac arrest. In the case of hypothermic cardiac arrest, CPR should be performed with chest compressions and ventilations at standard rates.

In patients with hypothermia, it is important to use a low reading thermometer such as an oesophageal temperature probe or vascular temperature probe. Skin surface thermometers are not effective in hypothermia cases, and rectal and tympanic thermometers may not provide accurate readings. Therefore, it is recommended to use oesophageal temperature or vascular temperature probes. However, it is worth noting that oesophageal probes may not be accurate if the patient is receiving warmed inhaled air.

Further Reading:

Hypothermic cardiac arrest is a rare situation that requires a tailored approach. Resuscitation is typically prolonged, but the prognosis for young, previously healthy individuals can be good. Hypothermic cardiac arrest may be associated with drowning. Hypothermia is defined as a core temperature below 35ºC and can be graded as mild, moderate, severe, or profound based on the core temperature. When the core temperature drops, basal metabolic rate falls and cell signaling between neurons decreases, leading to reduced tissue perfusion. Signs and symptoms of hypothermia progress as the core temperature drops, initially presenting as compensatory increases in heart rate and shivering, but eventually ceasing as the temperature drops into moderate hypothermia territory.

ECG changes associated with hypothermia include bradyarrhythmias, Osborn waves, prolonged PR, QRS, and QT intervals, shivering artifact, ventricular ectopics, and cardiac arrest. When managing hypothermic cardiac arrest, ALS should be initiated as per the standard ALS algorithm, but with modifications. It is important to check for signs of life, re-warm the patient, consider mechanical ventilation due to chest wall stiffness, adjust dosing or withhold drugs due to slowed drug metabolism, and correct electrolyte disturbances. The resuscitation of hypothermic patients is often prolonged and may continue for a number of hours.

Pulse checks during CPR may be difficult due to low blood pressure, and the pulse check is prolonged to 1 minute for this reason. Drug metabolism is slowed in hypothermic patients, leading to a build-up of potentially toxic plasma concentrations of administered drugs. Current guidance advises withholding drugs if the core temperature is below 30ºC and doubling the drug interval at core temperatures between 30 and 35ºC. Electrolyte disturbances are common in hypothermic patients, and it is important to interpret results keeping the setting in mind. Hypoglycemia should be treated, hypokalemia will often correct as the patient re-warms, ABG analyzers may not reflect the reality of the hypothermic patient, and severe hyperkalemia is a poor prognostic indicator.

Different warming measures can be used to increase the core body temperature, including external passive measures such as removal of wet clothes and insulation with blankets, external active measures such as forced heated air or hot-water immersion, and internal active measures such as inhalation of warm air, warmed intravenous fluids, gastric, bladder, peritoneal and/or pleural lavage and high volume renal haemofilter.

The first step in decontaminating radioactive material from an individual is to remove their clothing carefully, without shaking it too much to avoid spreading radioactive dust. The clothing should then be placed in a plastic bag or sealable container. Next, the person should be washed down with warm water from a clean source and scrubbed with detergent using a rinse-wipe-rinse method.

Further Reading:

Radiation exposure refers to the emission or transmission of energy in the form of waves or particles through space or a material medium. There are two types of radiation: ionizing and non-ionizing. Non-ionizing radiation, such as radio waves and visible light, has enough energy to move atoms within a molecule but not enough to remove electrons from atoms. Ionizing radiation, on the other hand, has enough energy to ionize atoms or molecules by detaching electrons from them.

There are different types of ionizing radiation, including alpha particles, beta particles, gamma rays, and X-rays. Alpha particles are positively charged and consist of 2 protons and 2 neutrons from the atom’s nucleus. They are emitted from the decay of heavy radioactive elements and do not travel far from the source atom. Beta particles are small, fast-moving particles with a negative electrical charge that are emitted from an atom’s nucleus during radioactive decay. They are more penetrating than alpha particles but less damaging to living tissue. Gamma rays and X-rays are weightless packets of energy called photons. Gamma rays are often emitted along with alpha or beta particles during radioactive decay and can easily penetrate barriers. X-rays, on the other hand, are generally lower in energy and less penetrating than gamma rays.

Exposure to ionizing radiation can damage tissue cells by dislodging orbital electrons, leading to the generation of highly reactive ion pairs. This can result in DNA damage and an increased risk of future malignant change. The extent of cell damage depends on factors such as the type of radiation, time duration of exposure, distance from the source, and extent of shielding.

The absorbed dose of radiation is directly proportional to time, so it is important to minimize the amount of time spent in the vicinity of a radioactive source. A lethal dose of radiation without medical management is 4.5 sieverts (Sv) to kill 50% of the population at 60 days. With medical management, the lethal dose is 5-6 Sv. The immediate effects of ionizing radiation can range from radiation burns to radiation sickness, which is divided into three main syndromes: hematopoietic, gastrointestinal, and neurovascular. Long-term effects can include hematopoietic cancers and solid tumor formation.

In terms of management, support is mainly supportive and includes IV fluids, antiemetics, analgesia, nutritional support, antibiotics, blood component substitution, and reduction of brain edema.

Nifedipine is the preferred medication for treating high altitude pulmonary edema (HAPE). When a patient shows signs of HAPE, the best course of action is to immediately descend to a lower altitude while receiving supplemental oxygen. However, if descent is not possible, nifedipine can be used to alleviate symptoms and assist with descent. Nifedipine works by reducing the pressure in the pulmonary artery. On the other hand, dexamethasone is the preferred medication for treating acute mountain sickness and high altitude cerebral edema (HACE).

Further Reading:

High Altitude Illnesses

Altitude & Hypoxia:
– As altitude increases, atmospheric pressure decreases and inspired oxygen pressure falls.
– Hypoxia occurs at altitude due to decreased inspired oxygen.
– At 5500m, inspired oxygen is approximately half that at sea level, and at 8900m, it is less than a third.

Acute Mountain Sickness (AMS):
– AMS is a clinical syndrome caused by hypoxia at altitude.
– Symptoms include headache, anorexia, sleep disturbance, nausea, dizziness, fatigue, malaise, and shortness of breath.
– Symptoms usually occur after 6-12 hours above 2500m.
– Risk factors for AMS include previous AMS, fast ascent, sleeping at altitude, and age <50 years old.
– The Lake Louise AMS score is used to assess the severity of AMS.
– Treatment involves stopping ascent, maintaining hydration, and using medication for symptom relief.
– Medications for moderate to severe symptoms include dexamethasone and acetazolamide.
– Gradual ascent, hydration, and avoiding alcohol can help prevent AMS.

High Altitude Pulmonary Edema (HAPE):
– HAPE is a progression of AMS but can occur without AMS symptoms.
– It is the leading cause of death related to altitude illness.
– Risk factors for HAPE include rate of ascent, intensity of exercise, absolute altitude, and individual susceptibility.
– Symptoms include dyspnea, cough, chest tightness, poor exercise tolerance, cyanosis, low oxygen saturations, tachycardia, tachypnea, crepitations, and orthopnea.
– Management involves immediate descent, supplemental oxygen, keeping warm, and medication such as nifedipine.

High Altitude Cerebral Edema (HACE):
– HACE is thought to result from vasogenic edema and increased vascular pressure.
– It occurs 2-4 days after ascent and is associated with moderate to severe AMS symptoms.
– Symptoms include headache, hallucinations, disorientation, confusion, ataxia, drowsiness, seizures, and manifestations of raised intracranial pressure.
– Immediate descent is crucial for management, and portable hyperbaric therapy may be used if descent is not possible.
– Medication for treatment includes dexamethasone and supplemental oxygen. Acetazolamide is typically used for prophylaxis.

The following provides a summary of common causes for different acid-base disorders.

Respiratory alkalosis can be caused by hyperventilation, such as during periods of anxiety. It can also be a result of conditions like pulmonary embolism, CNS disorders (such as stroke or encephalitis), altitude, pregnancy, or the early stages of aspirin overdose.

Respiratory acidosis, on the other hand, is often associated with chronic obstructive pulmonary disease (COPD), life-threatening asthma, pulmonary edema, sedative drug overdose (such as opiates or benzodiazepines), neuromuscular disease, obesity, or other respiratory conditions.

Metabolic alkalosis can occur due to vomiting, potassium depletion (often caused by diuretic usage), Cushing’s syndrome, or Conn’s syndrome.

Metabolic acidosis with a raised anion gap can be caused by lactic acidosis (such as in cases of hypoxemia, shock, sepsis, or infarction), ketoacidosis (such as in diabetes, starvation, or alcohol excess), renal failure, or poisoning (such as in late stages of aspirin overdose, methanol or ethylene glycol ingestion).

Lastly, metabolic acidosis with a normal anion gap can be a result of conditions like diarrhea, ammonium chloride ingestion, or adrenal insufficiency.

Heat stroke is a condition characterized by a systemic inflammatory response, where the core body temperature exceeds 40.6°C. It is accompanied by changes in mental state and varying levels of organ dysfunction. Heat stroke occurs when the body’s ability to regulate temperature is overwhelmed by a combination of excessive environmental heat, excessive heat production from metabolic processes (usually due to exertion), and inadequate heat loss.

It is important to consider other clinical conditions that can cause an increased core temperature. Sepsis can present similarly and should be ruled out. Neuroleptic malignant syndrome should be excluded in patients taking phenothiazines or other antipsychotics. Serotonin syndrome should be excluded in patients taking serotonergic medications such as SSRIs. Malignant hyperthermia should be considered in patients with a recent history of general anesthesia. Screening for recreational drug use, particularly cocaine, amphetamines, and ecstasy, is also recommended.

In patients with agitation and/or shivering, benzodiazepines (e.g. diazepam) can be beneficial. They help reduce excessive heat production and agitation. In severe cases of agitation, paralysis may be necessary. Dantrolene is commonly used, although there is currently limited high-level evidence supporting its use. Neuroleptics, such as chlorpromazine, which were once commonly used, should be avoided due to potential adverse effects.

Various cooling techniques are recommended, but there is currently insufficient evidence to determine the best approach. Simple measures like cold drinks, fanning, ice water packs, and spraying tepid water can be effective. Cold water immersion therapy may be helpful, but it requires patient stability and cooperation and may not be practical for critically ill patients. Advanced cooling techniques, such as cold IV fluids, surface cooling devices (SCD), intravascular cooling devices (ICD), and extracorporeal circuits, may be used for sicker patients.

According to the current NICE guidance, it is not recommended to diagnose Lyme disease in individuals who do not show any symptoms, even if they have been bitten by a tick. Therefore, there is no need to conduct tests or provide treatment in such cases. It is important to reassure these patients that the majority of ticks do not transmit Lyme disease. However, it is advised that they remain vigilant for any potential symptoms and return for re-evaluation if necessary. The ‘Be Tick Aware’ campaign by Public Health England can serve as a helpful resource for further information.

Moderate hypothermia is indicated by core temperatures ranging from 28-32ºC.

Further Reading:

Hypothermia is defined as a core temperature below 35ºC and can be graded as mild, moderate, severe, or profound based on the core temperature. When the core temperature drops, the basal metabolic rate decreases and cell signaling between neurons decreases, leading to reduced tissue perfusion. This can result in depressed myocardial contractility, vasoconstriction, ventilation-perfusion mismatch, and increased blood viscosity. Symptoms of hypothermia progress as the core temperature drops, starting with compensatory increases in heart rate and shivering, and eventually leading to bradyarrhythmias, prolonged PR, QRS, and QT intervals, and cardiac arrest.

In the management of hypothermic cardiac arrest, ALS should be initiated with some modifications. The pulse check during CPR should be prolonged to 1 minute due to difficulty in obtaining a pulse. Rewarming the patient is important, and mechanical ventilation may be necessary due to stiffness of the chest wall. Drug metabolism is slowed in hypothermic patients, so dosing of drugs should be adjusted or withheld. Electrolyte disturbances are common in hypothermic patients and should be corrected.

Frostbite refers to a freezing injury to human tissue and occurs when tissue temperature drops below 0ºC. It can be classified as superficial or deep, with superficial frostbite affecting the skin and subcutaneous tissues, and deep frostbite affecting bones, joints, and tendons. Frostbite can be classified from 1st to 4th degree based on the severity of the injury. Risk factors for frostbite include environmental factors such as cold weather exposure and medical factors such as peripheral vascular disease and diabetes.

Signs and symptoms of frostbite include skin changes, cold sensation or firmness to the affected area, stinging, burning, or numbness, clumsiness of the affected extremity, and excessive sweating, hyperemia, and tissue gangrene. Frostbite is diagnosed clinically and imaging may be used in some cases to assess perfusion or visualize occluded vessels. Management involves moving the patient to a warm environment, removing wet clothing, and rapidly rewarming the affected tissue. Analgesia should be given as reperfusion is painful, and blisters should be de-roofed and aloe vera applied. Compartment syndrome is a risk and should be monitored for. Severe cases may require surgical debridement of amputation.

When performing CPR on patients with a core temperature of 30-35°C, it is recommended to double the interval between IV drug doses compared to what is used for normothermic patients. However, if the core temperature is above 35°C, standard drug protocols should be followed.

Further Reading:

Cardiopulmonary arrest is a serious event with low survival rates. In non-traumatic cardiac arrest, only about 20% of patients who arrest as an in-patient survive to hospital discharge, while the survival rate for out-of-hospital cardiac arrest is approximately 8%. The Resus Council BLS/AED Algorithm for 2015 recommends chest compressions at a rate of 100-120 per minute with a compression depth of 5-6 cm. The ratio of chest compressions to rescue breaths is 30:2.

After a cardiac arrest, the goal of patient care is to minimize the impact of post cardiac arrest syndrome, which includes brain injury, myocardial dysfunction, the ischaemic/reperfusion response, and the underlying pathology that caused the arrest. The ABCDE approach is used for clinical assessment and general management. Intubation may be necessary if the airway cannot be maintained by simple measures or if it is immediately threatened. Controlled ventilation is aimed at maintaining oxygen saturation levels between 94-98% and normocarbia. Fluid status may be difficult to judge, but a target mean arterial pressure (MAP) between 65 and 100 mmHg is recommended. Inotropes may be administered to maintain blood pressure. Sedation should be adequate to gain control of ventilation, and short-acting sedating agents like propofol are preferred. Blood glucose levels should be maintained below 8 mmol/l. Pyrexia should be avoided, and there is some evidence for controlled mild hypothermia but no consensus on this.

Post ROSC investigations may include a chest X-ray, ECG monitoring, serial potassium and lactate measurements, and other imaging modalities like ultrasonography, echocardiography, CTPA, and CT head, depending on availability and skills in the local department. Treatment should be directed towards the underlying cause, and PCI or thrombolysis may be considered for acute coronary syndrome or suspected pulmonary embolism, respectively.

Patients who are comatose after ROSC without significant pre-arrest comorbidities should be transferred to the ICU for supportive care. Neurological outcome at 72 hours is the best prognostic indicator of outcome.

Decompression sickness often presents with symptoms such as paraplegia, tetraplegia, or hemiplegia. In the emergency department, the most crucial intervention is providing high flow oxygen at a rate of 15 L/min through a non-rebreather mask. This should be administered to all patients, regardless of their oxygen saturations. The definitive treatment for decompression sickness involves recompression therapy in a hyperbaric oxygen chamber, which should be arranged promptly.

Further Reading:

Decompression illness (DCI) is a term that encompasses both decompression sickness (DCS) and arterial gas embolism (AGE). When diving underwater, the increasing pressure causes gases to become more soluble and reduces the size of gas bubbles. As a diver ascends, nitrogen can come out of solution and form gas bubbles, leading to decompression sickness or the bends. Boyle’s and Henry’s gas laws help explain the changes in gases during changing pressure.

Henry’s law states that the amount of gas that dissolves in a liquid is proportional to the partial pressure of the gas. Divers often use atmospheres (ATM) as a measure of pressure, with 1 ATM being the pressure at sea level. Boyle’s law states that the volume of gas is inversely proportional to the pressure. As pressure increases, volume decreases.

Decompression sickness occurs when nitrogen comes out of solution as a diver ascends. The evolved gas can physically damage tissue by stretching or tearing it as bubbles expand, or by provoking an inflammatory response. Joints and spinal nervous tissue are commonly affected. Symptoms of primary damage usually appear immediately or soon after a dive, while secondary damage may present hours or days later.

Arterial gas embolism occurs when nitrogen bubbles escape into the arterial circulation and cause distal ischemia. The consequences depend on where the embolism lodges, ranging from tissue ischemia to stroke if it lodges in the cerebral arterial circulation. Mechanisms for distal embolism include pulmonary barotrauma, right to left shunt, and pulmonary filter overload.

Clinical features of decompression illness vary, but symptoms often appear within six hours of a dive. These can include joint pain, neurological symptoms, chest pain or breathing difficulties, rash, vestibular problems, and constitutional symptoms. Factors that increase the risk of DCI include diving at greater depth, longer duration, multiple dives close together, problems with ascent, closed rebreather circuits, flying shortly after diving, exercise shortly after diving, dehydration, and alcohol use.

Diagnosis of DCI is clinical, and investigations depend on the presentation. All patients should receive high flow oxygen, and a low threshold for ordering a chest X-ray should be maintained. Hydration is important, and IV fluids may be necessary. Definitive treatment is recompression therapy in a hyperbaric oxygen chamber, which should be arranged as soon as possible. Entonox should not be given, as it will increase the pressure effect in air spaces.

There are various cooling techniques that are recommended, but currently, there is limited conclusive evidence on which approach is the most effective. Some possible methods include simple measures such as consuming cold beverages, using fans, applying ice water packs, and spraying tepid water. Cold water immersion therapy can also be beneficial, but it requires the patient to be stable and cooperative, making it impractical for very ill individuals. For patients who are in a more critical condition, advanced cooling techniques like administering cold intravenous fluids, using surface cooling devices (SCD), employing intravascular cooling devices (ICD), or utilizing extracorporeal circuits may be utilized.

The Royal College of Emergency Medicine (RCEM) recommends asking four important questions to individuals showing signs and symptoms of carbon monoxide poisoning. These questions can be easily remembered using the acronym COMA. The questions are as follows:
1. Is anyone else in the house, including pets, experiencing similar symptoms?
2. Do the symptoms improve when you are outside of the house?
3. Are the boilers and cooking appliances in your house properly maintained?
4. Do you have a functioning carbon monoxide alarm?

Further Reading:

Carbon monoxide (CO) is a dangerous gas that is produced by the combustion of hydrocarbon fuels and can be found in certain chemicals. It is colorless and odorless, making it difficult to detect. In England and Wales, there are approximately 60 deaths each year due to accidental CO poisoning.

When inhaled, carbon monoxide binds to haemoglobin in the blood, forming carboxyhaemoglobin (COHb). It has a higher affinity for haemoglobin than oxygen, causing a left-shift in the oxygen dissociation curve and resulting in tissue hypoxia. This means that even though there may be a normal level of oxygen in the blood, it is less readily released to the tissues.

The clinical features of carbon monoxide toxicity can vary depending on the severity of the poisoning. Mild or chronic poisoning may present with symptoms such as headache, nausea, vomiting, vertigo, confusion, and weakness. More severe poisoning can lead to intoxication, personality changes, breathlessness, pink skin and mucosae, hyperpyrexia, arrhythmias, seizures, blurred vision or blindness, deafness, extrapyramidal features, coma, or even death.

To help diagnose domestic carbon monoxide poisoning, there are four key questions that can be asked using the COMA acronym. These questions include asking about co-habitees and co-occupants in the house, whether symptoms improve outside of the house, the maintenance of boilers and cooking appliances, and the presence of a functioning CO alarm.

Typical carboxyhaemoglobin levels can vary depending on whether the individual is a smoker or non-smoker. Non-smokers typically have levels below 3%, while smokers may have levels below 10%. Symptomatic individuals usually have levels between 10-30%, and severe toxicity is indicated by levels above 30%.

When managing carbon monoxide poisoning, the first step is to administer 100% oxygen. Hyperbaric oxygen therapy may be considered for individuals with a COHb concentration of over 20% and additional risk factors such as loss of consciousness, neurological signs, myocardial ischemia or arrhythmia, or pregnancy. Other management strategies may include fluid resuscitation, sodium bicarbonate for metabolic acidosis, and mannitol for cerebral edema.

Patients with decompression illness should avoid taking analgesics as they can potentially harm the patient. Instead, oxygen is the preferred method of analgesia and has been shown to improve prognosis. Symptoms of decompression illness can often be resolved by simply breathing oxygen from a cylinder. It is important to note that Entonox should never be administered to patients with suspected decompression illness as the additional inert gas load from the nitrous oxide can worsen symptoms. NSAIDs should also be avoided as they can exacerbate micro-hemorrhages caused by decompression illness. In cases of decompression illness, patients will typically be treated with recompression in a hyperbaric oxygen chamber. However, it is important to be cautious with the use of oxygen as it can cause pulmonary and neurological toxicity at certain pressures. Therefore, there is a risk of oxygen toxicity developing in patients undergoing recompression, and opioids should be avoided as they are believed to increase this risk.

Further Reading:

Decompression illness (DCI) is a term that encompasses both decompression sickness (DCS) and arterial gas embolism (AGE). When diving underwater, the increasing pressure causes gases to become more soluble and reduces the size of gas bubbles. As a diver ascends, nitrogen can come out of solution and form gas bubbles, leading to decompression sickness or the bends. Boyle’s and Henry’s gas laws help explain the changes in gases during changing pressure.

Henry’s law states that the amount of gas that dissolves in a liquid is proportional to the partial pressure of the gas. Divers often use atmospheres (ATM) as a measure of pressure, with 1 ATM being the pressure at sea level. Boyle’s law states that the volume of gas is inversely proportional to the pressure. As pressure increases, volume decreases.

Decompression sickness occurs when nitrogen comes out of solution as a diver ascends. The evolved gas can physically damage tissue by stretching or tearing it as bubbles expand, or by provoking an inflammatory response. Joints and spinal nervous tissue are commonly affected. Symptoms of primary damage usually appear immediately or soon after a dive, while secondary damage may present hours or days later.

Arterial gas embolism occurs when nitrogen bubbles escape into the arterial circulation and cause distal ischemia. The consequences depend on where the embolism lodges, ranging from tissue ischemia to stroke if it lodges in the cerebral arterial circulation. Mechanisms for distal embolism include pulmonary barotrauma, right to left shunt, and pulmonary filter overload.

Clinical features of decompression illness vary, but symptoms often appear within six hours of a dive. These can include joint pain, neurological symptoms, chest pain or breathing difficulties, rash, vestibular problems, and constitutional symptoms. Factors that increase the risk of DCI include diving at greater depth, longer duration, multiple dives close together, problems with ascent, closed rebreather circuits, flying shortly after diving, exercise shortly after diving, dehydration, and alcohol use.

Diagnosis of DCI is clinical, and investigations depend on the presentation. All patients should receive high flow oxygen, and a low threshold for ordering a chest X-ray should be maintained. Hydration is important, and IV fluids may be necessary. Definitive treatment is recompression therapy in a hyperbaric oxygen chamber, which should be arranged as soon as possible. Entonox should not be given, as it will increase the pressure effect in air spaces.

Mild hypothermia is indicated by core temperatures ranging from 32-35ºC.

Further Reading:

Hypothermia is defined as a core temperature below 35ºC and can be graded as mild, moderate, severe, or profound based on the core temperature. When the core temperature drops, the basal metabolic rate decreases and cell signaling between neurons decreases, leading to reduced tissue perfusion. This can result in decreased myocardial contractility, vasoconstriction, ventilation-perfusion mismatch, and increased blood viscosity. Symptoms of hypothermia progress as the core temperature drops, starting with compensatory increases in heart rate and shivering, and eventually leading to bradyarrhythmias, prolonged PR, QRS, and QT intervals, and cardiac arrest.

In the management of hypothermic cardiac arrest, ALS should be initiated with some modifications. The pulse check during CPR should be prolonged to 1 minute due to difficulty in obtaining a pulse. Rewarming the patient is important, and mechanical ventilation may be necessary due to stiffness of the chest wall. Drug metabolism is slowed in hypothermic patients, so dosing of drugs should be adjusted or withheld. Electrolyte disturbances are common in hypothermic patients and should be corrected.

Frostbite refers to a freezing injury to human tissue and occurs when tissue temperature drops below 0ºC. It can be classified as superficial or deep, with superficial frostbite affecting the skin and subcutaneous tissues, and deep frostbite affecting bones, joints, and tendons. Frostbite can be classified from 1st to 4th degree based on the severity of the injury. Risk factors for frostbite include environmental factors such as cold weather exposure and medical factors such as peripheral vascular disease and diabetes.

Signs and symptoms of frostbite include skin changes, cold sensation or firmness to the affected area, stinging, burning, or numbness, clumsiness of the affected extremity, and excessive sweating, hyperemia, and tissue gangrene. Frostbite is diagnosed clinically and imaging may be used in some cases to assess perfusion or visualize occluded vessels. Management involves moving the patient to a warm environment, removing wet clothing, and rapidly rewarming the affected tissue. Analgesia should be given as reperfusion is painful, and blisters should be de-roofed and aloe vera applied. Compartment syndrome is a risk and should be monitored for. Severe cases may require surgical debridement of amputation.

Hypothermia occurs when the core body temperature drops below 35°C. It is categorized as mild (32-35°C), moderate (28-32°C), or severe (<28°C). Rescuers at the scene can use the Swiss staging system to describe the condition of victims. The stages range from clearly conscious and shivering to unconscious and not breathing, with death due to irreversible hypothermia being the most severe stage. There are several risk factors for hypothermia, including environmental exposure, unsatisfactory housing, poverty, lack of cold awareness, drugs, alcohol, acute confusion, hypothyroidism, and sepsis. The clinical features of hypothermia vary depending on the severity. At 32-35°C, symptoms may include apathy, amnesia, ataxia, and dysarthria. At 30-32°C, there may be a decreased level of consciousness, hypotension, arrhythmias, respiratory depression, and muscular rigidity. Below 30°C, ventricular fibrillation may occur, especially with excessive movement or invasive procedures. Diagnosing hypothermia involves checking the core temperature using an oesophageal, rectal, or tympanic probe with a low reading thermometer. Rectal and tympanic temperatures may lag behind core temperature and are unreliable in hypothermia. Various investigations should be carried out, including blood tests, blood glucose, amylase, blood cultures, arterial blood gas, ECG, chest X-ray, and CT head if there is suspicion of head injury or CVA. The management of hypothermia involves supporting the ABCs, treating the patient in a warm room, removing wet clothes and drying the skin, monitoring the ECG, providing warmed, humidified oxygen, correcting hypoglycemia with IV glucose, and handling the patient gently to avoid VF arrest. Re-warming methods include passive re-warming with warm blankets or Bair hugger/polythene sheets, surface re-warming with a water bath, core re-warming with heated, humidified oxygen or peritoneal lavage, and extracorporeal re-warming via cardiopulmonary bypass for severe hypothermia/cardiac arrest. In the case of hypothermic cardiac arrest, CPR should be performed with chest compressions and ventilations at standard rates.

Heat stroke is a condition characterized by a systemic inflammatory response, where the core body temperature exceeds 40.6°C. It is accompanied by changes in mental state and varying levels of organ dysfunction. Heat stroke occurs when the body’s ability to regulate temperature is overwhelmed by a combination of excessive environmental heat, excessive heat production from metabolic processes (usually due to exertion), and inadequate heat loss.

It is important to consider other clinical conditions that can cause an increased core temperature. Sepsis can present similarly and should be ruled out. Neuroleptic malignant syndrome should be excluded in patients taking phenothiazines or other antipsychotics. Serotonin syndrome should be considered and excluded in patients taking serotonergic medications such as SSRIs. Malignant hyperthermia should be considered in patients with a recent history of general anesthesia. Screening for recreational drug use, particularly cocaine, amphetamines, and ecstasy, is also recommended.

Antipyretics, such as paracetamol, aspirin, and NSAIDs, do not have a role in the treatment of heat stroke. They work by interrupting the change in the hypothalamic set point caused by pyrogens, which is not the case in heat stroke where the hypothalamus is overwhelmed but functioning properly. In fact, antipyretics may be harmful in patients who develop complications in the liver, blood, and kidneys, as they can worsen bleeding tendencies.

Benzodiazepines, like diazepam, can be beneficial in patients experiencing agitation and/or shivering. They help reduce excessive heat production and agitation. In severe cases of agitation, paralysis may be necessary.

There are various cooling techniques recommended for the treatment of heat stroke, but currently, there is limited conclusive evidence on the most effective approach. Some possible methods include simple measures like consuming cold drinks, using fans, applying ice water packs, and spraying tepid water. Cold water immersion therapy can be helpful, but it requires the patient to be stable and cooperative, making it impractical for very sick patients. Advanced cooling techniques, such as cold IV fluids, surface cooling devices (SCD), intravascular cooling devices (ICD), and extracorporeal circuits, may be used for sicker patients.

Heat stroke is a condition characterized by a core temperature greater than 40.6°C, accompanied by changes in mental state and varying levels of organ dysfunction. There are two forms of heat stroke: classic non-exertional heat stroke, which occurs during high environmental temperatures and typically affects elderly patients during heat waves, and exertional heat stroke, which occurs during strenuous physical exercise in high environmental temperatures, such as endurance athletes competing in hot conditions. Heat stroke happens when the body’s thermoregulation is overwhelmed by excessive environmental heat, excessive metabolic heat production, and insufficient heat loss.

Several risk factors increase the likelihood of developing heat stroke. These include hot and humid environmental conditions, age (with the elderly and infants being particularly vulnerable), physical factors like obesity, excessive exertion, and dehydration, as well as medical comorbidities such as anorexia, cardiovascular disease, skin conditions, poorly controlled diabetes, Parkinson’s disease, and thyrotoxicosis. Certain drugs, including alcohol, amphetamines, anticholinergics, beta-blockers, cocaine, diuretics, phenothiazines, SSRIs, and sympathomimetics, can also increase the risk of heat stroke.

The typical clinical features of heat stroke include a core temperature greater than 40.6°C. Early signs may include extreme fatigue, headache, syncope, facial flushing, vomiting, and diarrhea. The skin is usually hot and dry, although sweating can occur in around 50% of cases of exertional heat stroke. The loss of the ability to sweat is a late and concerning sign. Hyperventilation is almost always present. Heat stroke can also lead to cardiovascular dysfunction, such as arrhythmias, hypotension, and shock, respiratory dysfunction including acute respiratory distress syndrome (ARDS), and central nervous system dysfunction, including seizures and coma. If the temperature rises above 41.5°C, multi-organ failure, coagulopathy, and rhabdomyolysis can occur.

Heat cramps, on the other hand, typically present with intense thirst and muscle cramps. Body temperature is often elevated but usually remains below 40°C. Sweating, heat dissipation mechanisms, and cognition are preserved, and there is no neurological impairment.

Heat exhaustion usually precedes heat stroke and, if left untreated, can progress to heat stroke. Heat dissipation is still functioning, and the body temperature is usually below 41°C.

To treat frostbite, it is important to quickly warm the affected area by immersing it in water that is consistently kept at a temperature of 40-42ºC. The Rewarming process should be continued until the affected area feels flexible and shows signs of redness, which typically takes around 15 to 30 minutes. It is recommended to provide strong pain relief medication during this process, as reperfusion can be extremely painful.

Further Reading:

Hypothermia is defined as a core temperature below 35ºC and can be graded as mild, moderate, severe, or profound based on the core temperature. When the core temperature drops, the basal metabolic rate decreases and cell signaling between neurons decreases, leading to reduced tissue perfusion. This can result in depressed myocardial contractility, vasoconstriction, ventilation-perfusion mismatch, and increased blood viscosity. Symptoms of hypothermia progress as the core temperature drops, starting with compensatory increases in heart rate and shivering, and eventually leading to bradyarrhythmias, prolonged PR, QRS, and QT intervals, and cardiac arrest.

In the management of hypothermic cardiac arrest, ALS should be initiated with some modifications. The pulse check during CPR should be prolonged to 1 minute due to difficulty in obtaining a pulse. Rewarming the patient is important, and mechanical ventilation may be necessary due to stiffness of the chest wall. Drug metabolism is slowed in hypothermic patients, so dosing of drugs should be adjusted or withheld. Electrolyte disturbances are common in hypothermic patients and should be corrected.

Frostbite refers to a freezing injury to human tissue and occurs when tissue temperature drops below 0ºC. It can be classified as superficial or deep, with superficial frostbite affecting the skin and subcutaneous tissues, and deep frostbite affecting bones, joints, and tendons. Frostbite can be classified from 1st to 4th degree based on the severity of the injury. Risk factors for frostbite include environmental factors such as cold weather exposure and medical factors such as peripheral vascular disease and diabetes.

Signs and symptoms of frostbite include skin changes, cold sensation or firmness to the affected area, stinging, burning, or numbness, clumsiness of the affected extremity, and excessive sweating, hyperemia, and tissue gangrene. Frostbite is diagnosed clinically and imaging may be used in some cases to assess perfusion or visualize occluded vessels. Management involves moving the patient to a warm environment, removing wet clothing, and rapidly rewarming the affected tissue. Analgesia should be given as reperfusion is painful, and blisters should be de-roofed and aloe vera applied. Compartment syndrome is a risk and should be monitored for. Severe cases may require surgical debridement of amputation.

Dexamethasone is the preferred medication for treating Acute Mountain Sickness (AMS) and High Altitude Cerebral Edema (HACE). In cases of mild AMS, simply halting the ascent and giving the body time to acclimatize may be sufficient. However, if mild AMS persists or worsens, or if the patient experiences moderate to severe AMS, descending to a lower altitude is the most effective treatment, preferably with the addition of supplemental oxygen. Dexamethasone is the recommended medication for managing both AMS and HACE.

Further Reading:

High Altitude Illnesses

Altitude & Hypoxia:
– As altitude increases, atmospheric pressure decreases and inspired oxygen pressure falls.
– Hypoxia occurs at altitude due to decreased inspired oxygen.
– At 5500m, inspired oxygen is approximately half that at sea level, and at 8900m, it is less than a third.

Acute Mountain Sickness (AMS):
– AMS is a clinical syndrome caused by hypoxia at altitude.
– Symptoms include headache, anorexia, sleep disturbance, nausea, dizziness, fatigue, malaise, and shortness of breath.
– Symptoms usually occur after 6-12 hours above 2500m.
– Risk factors for AMS include previous AMS, fast ascent, sleeping at altitude, and age <50 years old.
– The Lake Louise AMS score is used to assess the severity of AMS.
– Treatment involves stopping ascent, maintaining hydration, and using medication for symptom relief.
– Medications for moderate to severe symptoms include dexamethasone and acetazolamide.
– Gradual ascent, hydration, and avoiding alcohol can help prevent AMS.

High Altitude Pulmonary Edema (HAPE):
– HAPE is a progression of AMS but can occur without AMS symptoms.
– It is the leading cause of death related to altitude illness.
– Risk factors for HAPE include rate of ascent, intensity of exercise, absolute altitude, and individual susceptibility.
– Symptoms include dyspnea, cough, chest tightness, poor exercise tolerance, cyanosis, low oxygen saturations, tachycardia, tachypnea, crepitations, and orthopnea.
– Management involves immediate descent, supplemental oxygen, keeping warm, and medication such as nifedipine.

High Altitude Cerebral Edema (HACE):
– HACE is thought to result from vasogenic edema and increased vascular pressure.
– It occurs 2-4 days after ascent and is associated with moderate to severe AMS symptoms.
– Symptoms include headache, hallucinations, disorientation, confusion, ataxia, drowsiness, seizures, and manifestations of raised intracranial pressure.
– Immediate descent is crucial for management, and portable hyperbaric therapy may be used if descent is not possible.
– Medication for treatment includes dexamethasone and supplemental oxygen. Acetazolamide is typically used for prophylaxis.

When performing CPR on patients with severe hypothermia, it is recommended to limit defibrillation attempts to three. Hypothermia is characterized by a core temperature below 35ºC, with mild hypothermia ranging from 32-35ºC, moderate hypothermia from 30-32ºC, and severe hypothermia below 30ºC. This condition often occurs after drowning. If the individual’s core body temperature is below 30°C, it is advised to administer a maximum of three shocks using the highest output of the defibrillator.

Further Reading:

Cardiopulmonary arrest is a serious event with low survival rates. In non-traumatic cardiac arrest, only about 20% of patients who arrest as an in-patient survive to hospital discharge, while the survival rate for out-of-hospital cardiac arrest is approximately 8%. The Resus Council BLS/AED Algorithm for 2015 recommends chest compressions at a rate of 100-120 per minute with a compression depth of 5-6 cm. The ratio of chest compressions to rescue breaths is 30:2.

After a cardiac arrest, the goal of patient care is to minimize the impact of post cardiac arrest syndrome, which includes brain injury, myocardial dysfunction, the ischaemic/reperfusion response, and the underlying pathology that caused the arrest. The ABCDE approach is used for clinical assessment and general management. Intubation may be necessary if the airway cannot be maintained by simple measures or if it is immediately threatened. Controlled ventilation is aimed at maintaining oxygen saturation levels between 94-98% and normocarbia. Fluid status may be difficult to judge, but a target mean arterial pressure (MAP) between 65 and 100 mmHg is recommended. Inotropes may be administered to maintain blood pressure. Sedation should be adequate to gain control of ventilation, and short-acting sedating agents like propofol are preferred. Blood glucose levels should be maintained below 8 mmol/l. Pyrexia should be avoided, and there is some evidence for controlled mild hypothermia but no consensus on this.

Post ROSC investigations may include a chest X-ray, ECG monitoring, serial potassium and lactate measurements, and other imaging modalities like ultrasonography, echocardiography, CTPA, and CT head, depending on availability and skills in the local department. Treatment should be directed towards the underlying cause, and PCI or thrombolysis may be considered for acute coronary syndrome or suspected pulmonary embolism, respectively.

Patients who are comatose after ROSC without significant pre-arrest comorbidities should be transferred to the ICU for supportive care. Neurological outcome at 72 hours is the best prognostic indicator of outcome.

Heat stroke is a condition characterized by a systemic inflammatory response, where the core body temperature rises above 40.6°C. It is accompanied by alterations in mental state and varying degrees of organ dysfunction.

There are two types of heat stroke. The first is classic non-exertional heat stroke, which occurs when individuals are exposed to high environmental temperatures. This form of heat stroke is commonly seen in elderly patients during heat waves.

The second type is exertional heat stroke, which occurs during intense physical activity in hot weather conditions. This form of heat stroke is often observed in endurance athletes who participate in strenuous exercise in high temperatures.

Prussian blue is a substance that helps remove radioactive caesium from the body, a process known as decorporation. It is specifically effective for caesium exposure. When taken orally, Prussian blue binds to the radioactive caesium, forming a compound that can be excreted from the body, preventing further absorption. By using Prussian blue, the whole body radiation dose can be reduced by approximately two-thirds. Radioactive caesium is utilized in various medical, geological, and industrial applications, although incidents of environmental contamination are rare, they have been reported in Western Australia and Eastern Thailand during the first quarter of 2023.

Further Reading:

Radiation exposure refers to the emission or transmission of energy in the form of waves or particles through space or a material medium. There are two types of radiation: ionizing and non-ionizing. Non-ionizing radiation, such as radio waves and visible light, has enough energy to move atoms within a molecule but not enough to remove electrons from atoms. Ionizing radiation, on the other hand, has enough energy to ionize atoms or molecules by detaching electrons from them.

There are different types of ionizing radiation, including alpha particles, beta particles, gamma rays, and X-rays. Alpha particles are positively charged and consist of 2 protons and 2 neutrons from the atom’s nucleus. They are emitted from the decay of heavy radioactive elements and do not travel far from the source atom. Beta particles are small, fast-moving particles with a negative electrical charge that are emitted from an atom’s nucleus during radioactive decay. They are more penetrating than alpha particles but less damaging to living tissue. Gamma rays and X-rays are weightless packets of energy called photons. Gamma rays are often emitted along with alpha or beta particles during radioactive decay and can easily penetrate barriers. X-rays, on the other hand, are generally lower in energy and less penetrating than gamma rays.

Exposure to ionizing radiation can damage tissue cells by dislodging orbital electrons, leading to the generation of highly reactive ion pairs. This can result in DNA damage and an increased risk of future malignant change. The extent of cell damage depends on factors such as the type of radiation, time duration of exposure, distance from the source, and extent of shielding.

The absorbed dose of radiation is directly proportional to time, so it is important to minimize the amount of time spent in the vicinity of a radioactive source. A lethal dose of radiation without medical management is 4.5 sieverts (Sv) to kill 50% of the population at 60 days. With medical management, the lethal dose is 5-6 Sv. The immediate effects of ionizing radiation can range from radiation burns to radiation sickness, which is divided into three main syndromes: hematopoietic, gastrointestinal, and neurovascular. Long-term effects can include hematopoietic cancers and solid tumor formation.

In terms of management, support is mainly supportive and includes IV fluids, antiemetics, analgesia, nutritional support, antibiotics, blood component substitution, and reduction of brain edema.

Anhydrosis, or the inability to sweat, is frequently observed in individuals who experience heat stroke. This patient exhibits the main characteristics of heat stroke, including a core body temperature exceeding 40ºC and encephalopathy, which is evident through significant confusion. Additionally, the patient’s use of diuretics and advanced age are risk factors that increase the likelihood of developing severe heat-related illness. It is important to note that in the UK, most fatalities resulting from heat stroke occur in individuals aged 70 or older, typically within the initial days of a heat wave.

Further Reading:

Heat Stroke:
– Core temperature >40°C with central nervous system dysfunction
– Classified into classic/non-exertional heat stroke and exertional heat stroke
– Classic heat stroke due to passive exposure to severe environmental heat
– Exertional heat stroke due to strenuous physical activity in combination with excessive environmental heat
– Mechanisms to reduce core temperature overwhelmed, leading to tissue damage
– Symptoms include high body temperature, vascular endothelial surface damage, inflammation, dehydration, and renal failure
– Management includes cooling methods and supportive care
– Target core temperature for cooling is 38.5°C

Heat Exhaustion:
– Mild to moderate heat illness that can progress to heat stroke if untreated
– Core temperature elevated but <40°C
– Symptoms include nausea, vomiting, dizziness, and mild neurological symptoms
– Normal thermoregulation is disrupted
– Management includes moving patient to a cooler environment, rehydration, and rest

Other Heat-Related Illnesses:
– Heat oedema: transitory swelling of hands and feet, resolves spontaneously
– Heat syncope: results from volume depletion and peripheral vasodilatation, managed by moving patient to a cooler environment and rehydration
– Heat cramps: painful muscle contractions associated with exertion, managed with cooling, rest, analgesia, and rehydration

Risk Factors for Severe Heat-Related Illness:
– Old age, very young age, chronic disease and debility, mental illness, certain medications, housing issues, occupational factors

Management:
– Cooling methods include spraying with tepid water, fanning, administering cooled IV fluids, cold or ice water immersion, and ice packs
– Benzodiazepines may be used to control shivering
– Rapid cooling to achieve rapid normothermia should be avoided to prevent overcooling and hypothermia
– Supportive care includes intravenous fluid replacement, seizure treatment if required, and consideration of haemofiltration
– Some patients may require liver transplant due to significant liver damage
– Patients with heat stroke should ideally be managed in a HDU/ICU setting with CVP and urinary catheter output measurements

Hypothermic cardiac arrest is a rare situation that requires a tailored approach. Resuscitation is typically prolonged, but the prognosis for young, previously healthy individuals can be good. Hypothermic cardiac arrest may be associated with drowning. Hypothermia is defined as a core temperature below 35ºC and can be graded as mild, moderate, severe, or profound based on the core temperature. When the core temperature drops, basal metabolic rate falls and cell signaling between neurons decreases, leading to reduced tissue perfusion. Signs and symptoms of hypothermia progress as the core temperature drops, initially presenting as compensatory increases in heart rate and shivering, but eventually ceasing as the temperature drops into moderate hypothermia territory.

ECG changes associated with hypothermia include bradyarrhythmias, Osborn waves, prolonged PR, QRS, and QT intervals, shivering artifact, ventricular ectopics, and cardiac arrest. When managing hypothermic cardiac arrest, ALS should be initiated as per the standard ALS algorithm, but with modifications. It is important to check for signs of life, re-warm the patient, consider mechanical ventilation due to chest wall stiffness, adjust dosing or withhold drugs due to slowed drug metabolism, and correct electrolyte disturbances. The resuscitation of hypothermic patients is often prolonged and may continue for a number of hours.

Pulse checks during CPR may be difficult due to low blood pressure, and the pulse check is prolonged to 1 minute for this reason. Drug metabolism is slowed in hypothermic patients, leading to a build-up of potentially toxic plasma concentrations of administered drugs. Current guidance advises withholding drugs if the core temperature is below 30ºC and doubling the drug interval at core temperatures between 30 and 35ºC. Electrolyte disturbances are common in hypothermic patients, and it is important to interpret results keeping the setting in mind. Hypoglycemia should be treated, hypokalemia will often correct as the patient re-warms, ABG analyzers may not reflect the reality of the hypothermic patient, and severe hyperkalemia is a poor prognostic indicator.

Different warming measures can be used to increase the core body temperature, including external passive measures such as removal of wet clothes and insulation with blankets, external active measures such as forced heated air or hot-water immersion, and internal active measures such as inhalation of warm air, warmed intravenous fluids, gastric, bladder, peritoneal and/or pleural lavage and high volume renal haemofilter.

During CPR of a hypothermic patient, it is important to follow specific guidelines. If the patient’s core temperature is below 30ºC, resuscitation drugs, such as adrenaline, should be withheld. Once the core temperature rises above 30ºC, cardiac arrest drugs can be administered. However, if the patient’s temperature is between 30-35ºC, the interval for administering cardiac arrest drugs should be doubled. For example, adrenaline should be given every 6-10 minutes instead of the usual 3-5 minutes for a normothermic patient.

Further Reading:

Hypothermic cardiac arrest is a rare situation that requires a tailored approach. Resuscitation is typically prolonged, but the prognosis for young, previously healthy individuals can be good. Hypothermic cardiac arrest may be associated with drowning. Hypothermia is defined as a core temperature below 35ºC and can be graded as mild, moderate, severe, or profound based on the core temperature. When the core temperature drops, basal metabolic rate falls and cell signaling between neurons decreases, leading to reduced tissue perfusion. Signs and symptoms of hypothermia progress as the core temperature drops, initially presenting as compensatory increases in heart rate and shivering, but eventually ceasing as the temperature drops into moderate hypothermia territory.

ECG changes associated with hypothermia include bradyarrhythmias, Osborn waves, prolonged PR, QRS, and QT intervals, shivering artifact, ventricular ectopics, and cardiac arrest. When managing hypothermic cardiac arrest, ALS should be initiated as per the standard ALS algorithm, but with modifications. It is important to check for signs of life, re-warm the patient, consider mechanical ventilation due to chest wall stiffness, adjust dosing or withhold drugs due to slowed drug metabolism, and correct electrolyte disturbances. The resuscitation of hypothermic patients is often prolonged and may continue for a number of hours.

Pulse checks during CPR may be difficult due to low blood pressure, and the pulse check is prolonged to 1 minute for this reason. Drug metabolism is slowed in hypothermic patients, leading to a build-up of potentially toxic plasma concentrations of administered drugs. Current guidance advises withholding drugs if the core temperature is below 30ºC and doubling the drug interval at core temperatures between 30 and 35ºC. Electrolyte disturbances are common in hypothermic patients, and it is important to interpret results keeping the setting in mind. Hypoglycemia should be treated, hypokalemia will often correct as the patient re-warms, ABG analyzers may not reflect the reality of the hypothermic patient, and severe hyperkalemia is a poor prognostic indicator.

Different warming measures can be used to increase the core body temperature, including external passive measures such as removal of wet clothes and insulation with blankets, external active measures such as forced heated air or hot-water immersion, and internal active measures such as inhalation of warm air, warmed intravenous fluids, gastric, bladder, peritoneal and/or pleural lavage and high volume renal haemofilter.

Hypothermia can lead to various abnormalities in the electrocardiogram (ECG). These abnormalities include bradyarrhythmias, the presence of a J wave (also known as an Osborn wave), and prolonged intervals such as PR, QRS, and QT. Additionally, shivering artefact and ventricular ectopics may be observed. In severe cases, hypothermia can even result in cardiac arrest, which can manifest as ventricular tachycardia (VT), ventricular fibrillation (VF), or asystole.

One distinctive feature of hypothermia on an ECG is the appearance of a small extra wave immediately following the QRS complex. This wave, known as a J wave or Osborn wave, was named after the individual who first described it. Interestingly, this wave tends to disappear as the body temperature is warmed. Despite its recognition, the exact mechanism behind the presence of the J wave in hypothermia remains unknown.