Gentamicin is an antibiotic belonging to the aminoglycoside class. It works by binding to the 30S subunit of the ribosome in bacteria, thereby preventing the binding of aminoacyl-tRNA and ultimately inhibiting the initiation of protein synthesis.

The two most significant side effects associated with gentamicin are hearing loss and reversible nephrotoxicity. These side effects are directly related to the dosage of the medication and are more commonly observed in elderly individuals.

Hearing loss occurs due to damage to the vestibular apparatus located in the inner ear. On the other hand, nephrotoxicity is caused by the inhibition of protein synthesis in renal cells. This inhibition leads to necrosis of the cells in the proximal convoluted tubule and results in a condition known as acute tubular necrosis.

In summary, gentamicin mechanism of action and side effects, such as hearing loss and reversible nephrotoxicity, are closely linked to its interaction with the bacterial ribosome and its impact on protein synthesis. These effects are particularly prevalent in the elderly population.

Lithium is a commonly prescribed medication for bipolar disorder, as it helps stabilize mood. The recommended therapeutic range for lithium levels is typically between 0.4 and 0.8 mmol/l, although this range may vary depending on the laboratory. For maintenance therapy and treatment in older individuals, the lower end of the range is usually targeted. Toxic effects of lithium are typically observed when levels exceed 1.5 mmol/l. It is important to monitor lithium levels one week after starting therapy and after any dosage adjustments.

One potential side effect of lithium is the development of nephrogenic diabetes insipidus, a condition that affects the kidneys’ ability to concentrate urine. However, lithium does not cause diabetes mellitus. Another known side effect is hypothyroidism, which is a decrease in thyroid hormone production, but it does not lead to hyperthyroidism, an overactive thyroid.

Signs of lithium toxicity include nausea, vomiting, diarrhea, tremors, ataxia (loss of coordination), confusion, increased muscle tone, clonus (repetitive, involuntary muscle contractions), nephrogenic diabetes insipidus, convulsions, coma, and renal failure. It is crucial to be aware of these symptoms and seek medical attention if they occur.

Sodium bicarbonate is recommended as a treatment for TCA overdose according to the latest guidelines from RCEM and NPIS in 2021. Previous editions also suggested using glucagon if IV fluids and sodium bicarbonate were ineffective in treating the overdose.

Further Reading:

Tricyclic antidepressant (TCA) overdose is a common occurrence in emergency departments, with drugs like amitriptyline and dosulepin being particularly dangerous. TCAs work by inhibiting the reuptake of norepinephrine and serotonin in the central nervous system. In cases of toxicity, TCAs block various receptors, including alpha-adrenergic, histaminic, muscarinic, and serotonin receptors. This can lead to symptoms such as hypotension, altered mental state, signs of anticholinergic toxicity, and serotonin receptor effects.

TCAs primarily cause cardiac toxicity by blocking sodium and potassium channels. This can result in a slowing of the action potential, prolongation of the QRS complex, and bradycardia. However, the blockade of muscarinic receptors also leads to tachycardia in TCA overdose. QT prolongation and Torsades de Pointes can occur due to potassium channel blockade. TCAs can also have a toxic effect on the myocardium, causing decreased cardiac contractility and hypotension.

Early symptoms of TCA overdose are related to their anticholinergic properties and may include dry mouth, pyrexia, dilated pupils, agitation, sinus tachycardia, blurred vision, flushed skin, tremor, and confusion. Severe poisoning can lead to arrhythmias, seizures, metabolic acidosis, and coma. ECG changes commonly seen in TCA overdose include sinus tachycardia, widening of the QRS complex, prolongation of the QT interval, and an R/S ratio >0.7 in lead aVR.

Management of TCA overdose involves ensuring a patent airway, administering activated charcoal if ingestion occurred within 1 hour and the airway is intact, and considering gastric lavage for life-threatening cases within 1 hour of ingestion. Serial ECGs and blood gas analysis are important for monitoring. Intravenous fluids and correction of hypoxia are the first-line therapies. IV sodium bicarbonate is used to treat haemodynamic instability caused by TCA overdose, and benzodiazepines are the treatment of choice for seizure control. Other treatments that may be considered include glucagon, magnesium sulfate, and intravenous lipid emulsion.

There are certain things to avoid in TCA overdose, such as anti-arrhythmics like quinidine and flecainide, as they can prolonged depolarization.

The patient is experiencing acidosis, as indicated by the low pH. The low bicarb and base excess levels suggest that the metabolic system is contributing to or causing the acidosis. Additionally, the low pCO2 indicates that the respiratory system is attempting to compensate by driving alkalosis. However, the metabolic system is the primary factor in this case, leading to a diagnosis of metabolic acidosis with incomplete respiratory compensation.

Further Reading:

Salicylate poisoning, particularly from aspirin overdose, is a common cause of poisoning in the UK. One important concept to understand is that salicylate overdose leads to a combination of respiratory alkalosis and metabolic acidosis. Initially, the overdose stimulates the respiratory center, leading to hyperventilation and respiratory alkalosis. However, as the effects of salicylate on lactic acid production, breakdown into acidic metabolites, and acute renal injury occur, it can result in high anion gap metabolic acidosis.

The clinical features of salicylate poisoning include hyperventilation, tinnitus, lethargy, sweating, pyrexia (fever), nausea/vomiting, hyperglycemia and hypoglycemia, seizures, and coma.

When investigating salicylate poisoning, it is important to measure salicylate levels in the blood. The sample should be taken at least 2 hours after ingestion for symptomatic patients or 4 hours for asymptomatic patients. The measurement should be repeated every 2-3 hours until the levels start to decrease. Other investigations include arterial blood gas analysis, electrolyte levels (U&Es), complete blood count (FBC), coagulation studies (raised INR/PTR), urinary pH, and blood glucose levels.

To manage salicylate poisoning, an ABC approach should be followed to ensure a patent airway and adequate ventilation. Activated charcoal can be administered if the patient presents within 1 hour of ingestion. Oral or intravenous fluids should be given to optimize intravascular volume. Hypokalemia and hypoglycemia should be corrected. Urinary alkalinization with intravenous sodium bicarbonate can enhance the elimination of aspirin in the urine. In severe cases, hemodialysis may be necessary.

Urinary alkalinization involves targeting a urinary pH of 7.5-8.5 and checking it hourly. It is important to monitor for hypokalemia as alkalinization can cause potassium to shift from plasma into cells. Potassium levels should be checked every 1-2 hours.

In cases where the salicylate concentration is high (above 500 mg/L in adults or 350 mg/L in children), sodium bicarbonate can be administered intravenously. Hemodialysis is the treatment of choice for severe poisoning and may be indicated in cases of high salicylate levels, resistant metabolic acidosis, acute kidney injury, pulmonary edema, seizures and coma.

Activated charcoal is a useful treatment for many drug poisonings, but it is not effective against certain types of poisonings. To remember these exceptions, you can use the mnemonic PHAILS. This stands for Pesticides (specifically organophosphates), Hydrocarbons, Acids (strong), alkalis (strong), alcohols (such as ethanol, methanol, and ethylene glycol), Iron, Lithium, and Solvents.

Further Reading:

Poisoning in the emergency department is often caused by accidental or intentional overdose of prescribed drugs. Supportive treatment is the primary approach for managing most poisonings. This includes ensuring a clear airway, proper ventilation, maintaining normal fluid levels, temperature, and blood sugar levels, correcting any abnormal blood chemistry, controlling seizures, and assessing and treating any injuries.

In addition to supportive treatment, clinicians may need to consider strategies for decontamination, elimination, and administration of antidotes. Decontamination involves removing poisons from the skin or gastrointestinal tract. This can be done through rinsing the skin or using methods such as activated charcoal, gastric lavage, induced emesis, or whole bowel irrigation. However, induced emesis is no longer commonly used, while gastric lavage and whole bowel irrigation are rarely used.

Elimination methods include urinary alkalinization, hemodialysis, and hemoperfusion. These techniques help remove toxins from the body.

Activated charcoal is a commonly used method for decontamination. It works by binding toxins in the gastrointestinal tract, preventing their absorption. It is most effective if given within one hour of ingestion. However, it is contraindicated in patients with an insecure airway due to the risk of aspiration. Activated charcoal can be used for many drugs, but it is ineffective for certain poisonings, including pesticides (organophosphates), hydrocarbons, strong acids and alkalis, alcohols (ethanol, methanol, ethylene glycol), iron, lithium, and solvents.

Antidotes are specific treatments for poisoning caused by certain drugs or toxins. For example, cyanide poisoning can be treated with dicobalt edetate, hydroxocobalamin, or sodium nitrite and sodium thiosulphate. Benzodiazepine poisoning can be treated with flumazanil, while opiate poisoning can be treated with naloxone. Other examples include protamine for heparin poisoning, vitamin K or fresh frozen plasma for warfarin poisoning, fomepizole or ethanol for methanol poisoning, and methylene blue for methemoglobinemia caused by benzocaine or nitrates.

There are many other antidotes available for different types of poisoning, and resources such as TOXBASE and the National Poisons Information Service (NPIS) can provide valuable advice on managing poisonings.

Beta-blockers, like bisoprolol, and verapamil have a strong negative effect on the force of ventricular contraction. When these medications are taken together, they can significantly reduce ventricular contraction and lead to a slow heart rate, known as bradycardia. Additionally, the risk of developing AV block is increased. In certain situations, this combination can result in severe low blood pressure or even a complete absence of heart rhythm, known as asystole. Therefore, it is important to avoid using these medications together to prevent these potentially dangerous effects.

Urinary alkalinisation aims to achieve a urinary pH of 7.5-8.5. This process helps enhance the elimination of salicylates. It is important to regularly monitor urinary pH, ideally on an hourly basis.

Further Reading:

Salicylate poisoning, particularly from aspirin overdose, is a common cause of poisoning in the UK. One important concept to understand is that salicylate overdose leads to a combination of respiratory alkalosis and metabolic acidosis. Initially, the overdose stimulates the respiratory center, leading to hyperventilation and respiratory alkalosis. However, as the effects of salicylate on lactic acid production, breakdown into acidic metabolites, and acute renal injury occur, it can result in high anion gap metabolic acidosis.

The clinical features of salicylate poisoning include hyperventilation, tinnitus, lethargy, sweating, pyrexia (fever), nausea/vomiting, hyperglycemia and hypoglycemia, seizures, and coma.

When investigating salicylate poisoning, it is important to measure salicylate levels in the blood. The sample should be taken at least 2 hours after ingestion for symptomatic patients or 4 hours for asymptomatic patients. The measurement should be repeated every 2-3 hours until the levels start to decrease. Other investigations include arterial blood gas analysis, electrolyte levels (U&Es), complete blood count (FBC), coagulation studies (raised INR/PTR), urinary pH, and blood glucose levels.

To manage salicylate poisoning, an ABC approach should be followed to ensure a patent airway and adequate ventilation. Activated charcoal can be administered if the patient presents within 1 hour of ingestion. Oral or intravenous fluids should be given to optimize intravascular volume. Hypokalemia and hypoglycemia should be corrected. Urinary alkalinization with intravenous sodium bicarbonate can enhance the elimination of aspirin in the urine. In severe cases, hemodialysis may be necessary.

Urinary alkalinization involves targeting a urinary pH of 7.5-8.5 and checking it hourly. It is important to monitor for hypokalemia as alkalinization can cause potassium to shift from plasma into cells. Potassium levels should be checked every 1-2 hours.

In cases where the salicylate concentration is high (above 500 mg/L in adults or 350 mg/L in children), sodium bicarbonate can be administered intravenously. Hemodialysis is the treatment of choice for severe poisoning and may be indicated in cases of high salicylate levels, resistant metabolic acidosis, acute kidney injury, pulmonary edema, seizures and coma.

The clinical manifestations of theophylline toxicity are more closely associated with acute poisoning rather than chronic overexposure. The primary clinical features of theophylline toxicity include headache, dizziness, nausea and vomiting, abdominal pain, tachycardia and dysrhythmias, seizures, mild metabolic acidosis, hypokalaemia, hypomagnesaemia, hypophosphataemia, hypo- or hypercalcaemia, and hyperglycaemia. Seizures are more prevalent in cases of acute overdose compared to chronic overexposure. In contrast, chronic theophylline overdose typically presents with minimal gastrointestinal symptoms. Cardiac dysrhythmias are more frequently observed in individuals who have experienced chronic overdose rather than acute overdose.

The Royal College of Emergency Medicine (RCEM) recognizes four antidotes that can be used to treat cyanide poisoning: Hydroxycobalamin, Sodium thiosulphate, Sodium nitrite, and Dicobalt edetate. When managing cyanide toxicity, it is important to provide supportive treatment using the ABCDE approach. This includes administering supplemental high flow oxygen, providing hemodynamic support (including the use of inotropes if necessary), and administering the appropriate antidotes. In the UK, these four antidotes should be readily available in Emergency Departments according to the RCEM/NPIS guideline on antidote availability. Hydroxocobalamin followed by sodium thiosulphate is generally the preferred treatment if both options are available. Healthcare workers should be aware that patients with cyanide poisoning may expel HCN through vomit and skin, so it is crucial to use appropriate personal protective equipment when caring for these patients.

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.

Methanol poisoning is linked to an increase in anion gap acidosis.

Further Reading:

Arterial blood gases (ABG) are an important diagnostic tool used to assess a patient’s acid-base status and respiratory function. When obtaining an ABG sample, it is crucial to prioritize safety measures to minimize the risk of infection and harm to the patient. This includes performing hand hygiene before and after the procedure, wearing gloves and protective equipment, disinfecting the puncture site with alcohol, using safety needles when available, and properly disposing of equipment in sharps bins and contaminated waste bins.

To reduce the risk of harm to the patient, it is important to test for collateral circulation using the modified Allen test for radial artery puncture. Additionally, it is essential to inquire about any occlusive vascular conditions or anticoagulation therapy that may affect the procedure. The puncture site should be checked for signs of infection, injury, or previous surgery. After the test, pressure should be applied to the puncture site or the patient should be advised to apply pressure for at least 5 minutes to prevent bleeding.

Interpreting ABG results requires a systematic approach. The core set of results obtained from a blood gas analyser includes the partial pressures of oxygen and carbon dioxide, pH, bicarbonate concentration, and base excess. These values are used to assess the patient’s acid-base status.

The pH value indicates whether the patient is in acidosis, alkalosis, or within the normal range. A pH less than 7.35 indicates acidosis, while a pH greater than 7.45 indicates alkalosis.

The respiratory system is assessed by looking at the partial pressure of carbon dioxide (pCO2). An elevated pCO2 contributes to acidosis, while a low pCO2 contributes to alkalosis.

The metabolic aspect is assessed by looking at the bicarbonate (HCO3-) level and the base excess. A high bicarbonate concentration and base excess indicate alkalosis, while a low bicarbonate concentration and base excess indicate acidosis.

Analyzing the pCO2 and base excess values can help determine the primary disturbance and whether compensation is occurring. For example, a respiratory acidosis (elevated pCO2) may be accompanied by metabolic alkalosis (elevated base excess) as a compensatory response.

The anion gap is another important parameter that can help determine the cause of acidosis. It is calculated by subtracting the sum of chloride and bicarbonate from the sum of sodium and potassium.

Haemodialysis is recommended for patients with salicylate poisoning if they meet any of the following criteria: plasma salicylate level exceeding 700 mg/L, metabolic acidosis that does not improve with treatment (plasma pH below 7.2), acute kidney injury, pulmonary edema, seizures, coma, unresolved central nervous system effects despite correcting acidosis, persistently high salicylate concentrations that do not respond to urinary alkalinisation. Severe cases of salicylate poisoning, especially in patients under 10 years old or over 70 years old, may require dialysis earlier than the listed indications.

Further Reading:

Salicylate poisoning, particularly from aspirin overdose, is a common cause of poisoning in the UK. One important concept to understand is that salicylate overdose leads to a combination of respiratory alkalosis and metabolic acidosis. Initially, the overdose stimulates the respiratory center, leading to hyperventilation and respiratory alkalosis. However, as the effects of salicylate on lactic acid production, breakdown into acidic metabolites, and acute renal injury occur, it can result in high anion gap metabolic acidosis.

The clinical features of salicylate poisoning include hyperventilation, tinnitus, lethargy, sweating, pyrexia (fever), nausea/vomiting, hyperglycemia and hypoglycemia, seizures, and coma.

When investigating salicylate poisoning, it is important to measure salicylate levels in the blood. The sample should be taken at least 2 hours after ingestion for symptomatic patients or 4 hours for asymptomatic patients. The measurement should be repeated every 2-3 hours until the levels start to decrease. Other investigations include arterial blood gas analysis, electrolyte levels (U&Es), complete blood count (FBC), coagulation studies (raised INR/PTR), urinary pH, and blood glucose levels.

To manage salicylate poisoning, an ABC approach should be followed to ensure a patent airway and adequate ventilation. Activated charcoal can be administered if the patient presents within 1 hour of ingestion. Oral or intravenous fluids should be given to optimize intravascular volume. Hypokalemia and hypoglycemia should be corrected. Urinary alkalinization with intravenous sodium bicarbonate can enhance the elimination of aspirin in the urine. In severe cases, hemodialysis may be necessary.

Urinary alkalinization involves targeting a urinary pH of 7.5-8.5 and checking it hourly. It is important to monitor for hypokalemia as alkalinization can cause potassium to shift from plasma into cells. Potassium levels should be checked every 1-2 hours.

In cases where the salicylate concentration is high (above 500 mg/L in adults or 350 mg/L in children), sodium bicarbonate can be administered intravenously. Hemodialysis is the treatment of choice for severe poisoning and may be indicated in cases of high salicylate levels, resistant metabolic acidosis, acute kidney injury, pulmonary edema, seizures and coma.

Statins, although generally safe and well-tolerated, can cause myopathy and myotoxicity. This range of muscle-related side effects can vary from mild muscle pain to the most severe case of rhabdomyolysis, which can lead to kidney failure, blood clotting issues, and even death.

The different levels of myotoxicity associated with statins are as follows:
– Myalgia: muscle symptoms without an increase in creatine kinase (CK) levels.
– Asymptomatic myopathy: elevated CK levels without muscle symptoms.
– Myositis: muscle symptoms with CK levels elevated less than 10 times the upper limit of normal.
– Rhabdomyolysis: muscle symptoms with CK levels elevated more than 10 times the upper limit of normal, potentially leading to myoglobinuria (presence of myoglobin in urine) and renal failure.

Most statins are broken down by the cytochrome P450 enzyme system. When taken with drugs that strongly inhibit this system, the concentration of statins in the blood can significantly increase. This, in turn, raises the risk of myopathy. A well-known example of this is the combination of statins with macrolide antibiotics like erythromycin and clarithromycin. Co-prescribing these drugs with statins has been linked to a higher risk of myopathy, hospitalization due to rhabdomyolysis, acute kidney injury, and increased mortality rates.

The standard drug regimen for tuberculosis is generally safe to use during pregnancy, with the exception of streptomycin which should be avoided. However, the use of isoniazid during pregnancy has been associated with potential risks such as liver damage in the mother and the possibility of neuropathy and seizures in the newborn.

Here is a list outlining some commonly encountered drugs that have adverse effects during pregnancy:

ACE inhibitors (e.g. ramipril): If taken during the second and third trimesters, these medications can lead to reduced blood flow, kidney failure, and a condition called oligohydramnios.

Aminoglycosides (e.g. gentamicin): These drugs can cause ototoxicity, resulting in hearing loss in the baby.

Aspirin: High doses of aspirin can increase the risk of first trimester abortions, delayed labor, premature closure of the fetal ductus arteriosus, and a condition called fetal kernicterus. However, low doses (e.g. 75 mg) do not pose significant risks.

Benzodiazepines (e.g. diazepam): When taken late in pregnancy, these medications can cause respiratory depression in the baby and lead to a withdrawal syndrome.

Calcium-channel blockers: If taken during the first trimester, these drugs can cause abnormalities in the fingers and toes. If taken during the second and third trimesters, they may result in fetal growth retardation.

Carbamazepine: This medication can increase the risk of hemorrhagic disease in the newborn and neural tube defects.

Chloramphenicol: Use of this drug in newborns can lead to a condition known as grey baby syndrome.

Corticosteroids: If taken during the first trimester, corticosteroids may increase the risk of orofacial clefts in the baby.

Danazol: When taken during the first trimester, this medication can cause masculinization of the female fetuses genitals.

Finasteride: Pregnant women should avoid handling crushed or broken tablets of finasteride as it can be absorbed through the skin and affect the development of male sex organs in the baby.

Haloperidol: If taken during the first trimester, this medication may increase the risk of limb malformations. If taken during the third trimester, it can lead to an increased risk of extrapyramidal symptoms in the newborn.

Heparin: Use of heparin during pregnancy is associated with an acceptable bleeding rate and a low rate of thrombotic recurrence in the mother.

In cases of anaphylaxis, it is important to administer non-sedating antihistamines after adrenaline administration and initial resuscitation. Previous guidelines recommended the use of chlorpheniramine and hydrocortisone as third line treatments, but the 2021 guidelines have removed this recommendation. Corticosteroids are no longer advised. Instead, it is now recommended to use non-sedating antihistamines such as cetirizine, loratadine, and fexofenadine, as alternatives to the sedating antihistamine chlorpheniramine. The top priority treatments for anaphylaxis are adrenaline, oxygen, and fluids. The Resuscitation Council advises that administration of non-sedating antihistamines should occur after the initial resuscitation.

Further Reading:

Anaphylaxis is a severe and life-threatening hypersensitivity reaction that can have sudden onset and progression. It is characterized by skin or mucosal changes and can lead to life-threatening airway, breathing, or circulatory problems. Anaphylaxis can be allergic or non-allergic in nature.

In allergic anaphylaxis, there is an immediate hypersensitivity reaction where an antigen stimulates the production of IgE antibodies. These antibodies bind to mast cells and basophils. Upon re-exposure to the antigen, the IgE-covered cells release histamine and other inflammatory mediators, causing smooth muscle contraction and vasodilation.

Non-allergic anaphylaxis occurs when mast cells degrade due to a non-immune mediator. The clinical outcome is the same as in allergic anaphylaxis.

The management of anaphylaxis is the same regardless of the cause. Adrenaline is the most important drug and should be administered as soon as possible. The recommended doses for adrenaline vary based on age. Other treatments include high flow oxygen and an IV fluid challenge. Corticosteroids and chlorpheniramine are no longer recommended, while non-sedating antihistamines may be considered as third-line treatment after initial stabilization of airway, breathing, and circulation.

Common causes of anaphylaxis include food (such as nuts, which is the most common cause in children), drugs, and venom (such as wasp stings). Sometimes it can be challenging to determine if a patient had a true episode of anaphylaxis. In such cases, serum tryptase levels may be measured, as they remain elevated for up to 12 hours following an acute episode of anaphylaxis.

The Resuscitation Council (UK) provides guidelines for the management of anaphylaxis, including a visual algorithm that outlines the recommended steps for treatment.
https://www.resus.org.uk/sites/default/files/2021-05/Emergency%20Treatment%20of%20Anaphylaxis%20May%202021_0.pdf

An overdose of aspirin often leads to a combination of respiratory alkalosis and metabolic acidosis. Initially, the stimulation of the respiratory center causes hyperventilation and results in respiratory alkalosis. However, as the overdose progresses, the direct acidic effects of aspirin cause an increase in the anion gap and metabolic acidosis.

Here is a summary of common causes for different acid-base disorders:

Respiratory alkalosis can be caused by hyperventilation due to factors such as anxiety, pulmonary embolism, CNS disorders (such as stroke or encephalitis), altitude, pregnancy, and the early stages of aspirin overdose.

Respiratory acidosis can occur in individuals with chronic obstructive pulmonary disease (COPD), life-threatening asthma, pulmonary edema, sedative drug overdose (such as opioids or benzodiazepines), neuromuscular diseases, and obesity.

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

Metabolic acidosis with a raised anion gap can result from conditions such as lactic acidosis (caused by factors like hypoxemia, shock, sepsis, or tissue infarction), ketoacidosis (associated with diabetes, starvation, or excessive alcohol consumption), renal failure, and poisoning (including the late stages of aspirin overdose, methanol or ethylene glycol ingestion).

Metabolic acidosis with a normal anion gap can be seen in renal tubular acidosis, diarrhea, ammonium chloride ingestion, and adrenal insufficiency.

Dantrolene works by blocking the release of calcium ions from the sarcoplasmic reticulum in skeletal muscle cells. This reduces the amount of calcium available to bind to troponin on actin filaments, which in turn decreases the muscle’s ability to contract and reduces energy usage.

Further Reading:

Malignant hyperthermia is a rare and life-threatening syndrome that can be triggered by certain medications in individuals who are genetically susceptible. The most common triggers are suxamethonium and inhalational anaesthetic agents. The syndrome is caused by the release of stored calcium ions from skeletal muscle cells, leading to uncontrolled muscle contraction and excessive heat production. This results in symptoms such as high fever, sweating, flushed skin, rapid heartbeat, and muscle rigidity. It can also lead to complications such as acute kidney injury, rhabdomyolysis, and metabolic acidosis. Treatment involves discontinuing the trigger medication, administering dantrolene to inhibit calcium release and promote muscle relaxation, and managing any associated complications such as hyperkalemia and acidosis. Referral to a malignant hyperthermia center for further investigation is also recommended.

Naloxone is a specific antidote for opioid overdose. It effectively reverses respiratory depression and coma when given in sufficient dosage. The initial dose is administered intravenously at 400 micrograms, followed by 800 micrograms for up to 2 doses at 1-minute intervals if there is no response to the preceding dose. If there is still no response, the dosage is increased to 2 mg for one dose. In seriously poisoned patients, a 4 mg dose may be required. If the intravenous route is not feasible, naloxone can also be given by intramuscular injection.

Due to its shorter duration of action compared to most opioids, close monitoring and repeated injections are necessary. The frequency of doses should be based on the respiratory rate and depth of coma, with the dose generally repeated every 2-3 minutes up to a maximum of 10 mg. In cases where repeated doses are needed, naloxone can be administered through a continuous infusion, which should be adjusted according to the vital signs. Initially, the infusion rate can be set at 60% of the initial resuscitative IV dose per hour.

It is important to note that in opioid addicts, the administration of naloxone may trigger a withdrawal syndrome characterized by symptoms such as abdominal cramps, nausea, and diarrhea. However, these symptoms typically subside within 2 hours.

During the first trimester of pregnancy, the use of warfarin can lead to a condition known as fetal warfarin syndrome. This condition is characterized by nasal hypoplasia, bone stippling, bilateral optic atrophy, and intellectual disability in the baby. However, if warfarin is taken during the second or third trimester, it can cause optic atrophy, cataracts, microcephaly, microphthalmia, intellectual disability, and both fetal and maternal hemorrhage.

There are several other drugs that can have adverse effects during pregnancy. For example, ACE inhibitors like ramipril can cause hypoperfusion, renal failure, and the oligohydramnios sequence if taken during the second and third trimesters. Aminoglycosides such as gentamicin can lead to ototoxicity and deafness in the baby. High doses of aspirin can result in first trimester abortions, delayed onset labor, premature closure of the fetal ductus arteriosus, and fetal kernicterus. However, low doses of aspirin (e.g. 75 mg) do not pose significant risks.

Benzodiazepines like diazepam, when taken late in pregnancy, can cause respiratory depression and a neonatal withdrawal syndrome. Calcium-channel blockers, if taken during the first trimester, can cause phalangeal abnormalities, while their use in the second and third trimesters can lead to fetal growth retardation. Carbamazepine can result in hemorrhagic disease of the newborn and neural tube defects. Chloramphenicol can cause gray baby syndrome. Corticosteroids, if taken during the first trimester, may cause orofacial clefts.

Danazol, if taken during the first trimester, can cause masculinization of the female fetuses genitals. Finasteride should not be handled by pregnant women as crushed or broken tablets can be absorbed through the skin and affect male sex organ development. Haloperidol, if taken during the first trimester, may cause limb malformations, while its use in the third trimester increases the risk of extrapyramidal symptoms in the newborn.

Heparin can lead to maternal bleeding and thrombocytopenia. Isoniazid can cause maternal liver damage and neuropathy and seizures in the baby. Isotretinoin carries a high risk of teratogenicity, including multiple congenital malformations and spontaneous abortion.

If a person shows symptoms after ingesting salicylate, their salicylate levels should be measured 2 hours after ingestion. However, if the person does not show any symptoms, the levels should be measured 4 hours after ingestion. It is important to note that if enteric coated preparations are taken, salicylate levels may continue to increase for up to 12 hours. Therefore, it is necessary to regularly check the levels every 2-3 hours until they start to decrease.

Further Reading:

Salicylate poisoning, particularly from aspirin overdose, is a common cause of poisoning in the UK. One important concept to understand is that salicylate overdose leads to a combination of respiratory alkalosis and metabolic acidosis. Initially, the overdose stimulates the respiratory center, leading to hyperventilation and respiratory alkalosis. However, as the effects of salicylate on lactic acid production, breakdown into acidic metabolites, and acute renal injury occur, it can result in high anion gap metabolic acidosis.

The clinical features of salicylate poisoning include hyperventilation, tinnitus, lethargy, sweating, pyrexia (fever), nausea/vomiting, hyperglycemia and hypoglycemia, seizures, and coma.

When investigating salicylate poisoning, it is important to measure salicylate levels in the blood. The sample should be taken at least 2 hours after ingestion for symptomatic patients or 4 hours for asymptomatic patients. The measurement should be repeated every 2-3 hours until the levels start to decrease. Other investigations include arterial blood gas analysis, electrolyte levels (U&Es), complete blood count (FBC), coagulation studies (raised INR/PTR), urinary pH, and blood glucose levels.

To manage salicylate poisoning, an ABC approach should be followed to ensure a patent airway and adequate ventilation. Activated charcoal can be administered if the patient presents within 1 hour of ingestion. Oral or intravenous fluids should be given to optimize intravascular volume. Hypokalemia and hypoglycemia should be corrected. Urinary alkalinization with intravenous sodium bicarbonate can enhance the elimination of aspirin in the urine. In severe cases, hemodialysis may be necessary.

Urinary alkalinization involves targeting a urinary pH of 7.5-8.5 and checking it hourly. It is important to monitor for hypokalemia as alkalinization can cause potassium to shift from plasma into cells. Potassium levels should be checked every 1-2 hours.

In cases where the salicylate concentration is high (above 500 mg/L in adults or 350 mg/L in children), sodium bicarbonate can be administered intravenously. Hemodialysis is the treatment of choice for severe poisoning and may be indicated in cases of high salicylate levels, resistant metabolic acidosis, acute kidney injury, pulmonary edema, seizures and coma.

Extrapyramidal side effects are most commonly seen with the piperazine phenothiazines (fluphenazine, prochlorperazine, and trifluoperazine) and butyrophenones (benperidol and haloperidol). Among these, haloperidol is the most frequently implicated antipsychotic drug.

Tardive dyskinesia, which involves rhythmic and involuntary movements of the tongue, face, and jaw, typically develops after long-term treatment or high doses. It is the most severe manifestation of extrapyramidal symptoms, as it may become irreversible even after discontinuing the causative drug, and treatment options are generally ineffective.

Dystonia, characterized by abnormal movements of the face and body, is more commonly observed in children and young adults and tends to occur after only a few doses. Acute dystonia can be managed with intravenous administration of procyclidine (5 mg) or benzatropine (2 mg) as a bolus.

Akathisia refers to an unpleasant sensation of restlessness, while akinesia refers to an inability to initiate movement.

Elderly patients with dementia-related psychosis who are treated with haloperidol have an increased risk of mortality. This is believed to be due to a higher likelihood of experiencing cardiovascular events and infections such as pneumonia.

Liver damage occurs as a result of an overdose of paracetamol due to the formation of a toxic metabolite called N-acetyl-p-benzoquinone imine (NAPQI). When the normal pathways for metabolizing paracetamol are overwhelmed, NAPQI is produced. This toxic metabolite depletes the protective glutathione in the liver, which is usually responsible for neutralizing harmful substances. As a result, there is an insufficient amount of glutathione available to conjugate the excess NAPQI. Consequently, NAPQI binds to hepatocytes, causing their denaturation and ultimately leading to cell death.

Further Reading:

Paracetamol poisoning occurs when the liver is unable to metabolize paracetamol properly, leading to the production of a toxic metabolite called N-acetyl-p-benzoquinone imine (NAPQI). Normally, NAPQI is conjugated by glutathione into a non-toxic form. However, during an overdose, the liver’s conjugation systems become overwhelmed, resulting in increased production of NAPQI and depletion of glutathione stores. This leads to the formation of covalent bonds between NAPQI and cell proteins, causing cell death in the liver and kidneys.

Symptoms of paracetamol poisoning may not appear for the first 24 hours or may include abdominal symptoms such as nausea and vomiting. After 24 hours, hepatic necrosis may develop, leading to elevated liver enzymes, right upper quadrant pain, and jaundice. Other complications can include encephalopathy, oliguria, hypoglycemia, renal failure, and lactic acidosis.

The management of paracetamol overdose depends on the timing and amount of ingestion. Activated charcoal may be given if the patient presents within 1 hour of ingesting a significant amount of paracetamol. N-acetylcysteine (NAC) is used to increase hepatic glutathione production and is given to patients who meet specific criteria. Blood tests are taken to assess paracetamol levels, liver function, and other parameters. Referral to a medical or liver unit may be necessary, and psychiatric follow-up should be considered for deliberate overdoses.

In cases of staggered ingestion, all patients should be treated with NAC without delay. Blood tests are also taken, and if certain criteria are met, NAC can be discontinued. Adverse reactions to NAC are common and may include anaphylactoid reactions, rash, hypotension, and nausea. Treatment for adverse reactions involves medications such as chlorpheniramine and salbutamol, and the infusion may be stopped if necessary.

The prognosis for paracetamol poisoning can be poor, especially in cases of severe liver injury. Fulminant liver failure may occur, and liver transplant may be necessary. Poor prognostic indicators include low arterial pH, prolonged prothrombin time, high plasma creatinine, and hepatic encephalopathy.

This individual has developed Dupuytren’s contracture, which is a hand deformity characterized by a fixed flexion caused by palmar fibromatosis. The only anticonvulsant treatment believed to be connected to the development of Dupuytren’s contracture is phenytoin. Additionally, other conditions associated with its occurrence include liver cirrhosis, diabetes mellitus, alcoholism, and trauma.

In adults, urinary alkalinisation is initiated when the salicylate level exceeds 500 mg/L (>3.6 mmol/L). For children, the threshold is set at a salicylate concentration of > 350 mg/L (2.5 mmol/L).

Further Reading:

Salicylate poisoning, particularly from aspirin overdose, is a common cause of poisoning in the UK. One important concept to understand is that salicylate overdose leads to a combination of respiratory alkalosis and metabolic acidosis. Initially, the overdose stimulates the respiratory center, leading to hyperventilation and respiratory alkalosis. However, as the effects of salicylate on lactic acid production, breakdown into acidic metabolites, and acute renal injury occur, it can result in high anion gap metabolic acidosis.

The clinical features of salicylate poisoning include hyperventilation, tinnitus, lethargy, sweating, pyrexia (fever), nausea/vomiting, hyperglycemia and hypoglycemia, seizures, and coma.

When investigating salicylate poisoning, it is important to measure salicylate levels in the blood. The sample should be taken at least 2 hours after ingestion for symptomatic patients or 4 hours for asymptomatic patients. The measurement should be repeated every 2-3 hours until the levels start to decrease. Other investigations include arterial blood gas analysis, electrolyte levels (U&Es), complete blood count (FBC), coagulation studies (raised INR/PTR), urinary pH, and blood glucose levels.

To manage salicylate poisoning, an ABC approach should be followed to ensure a patent airway and adequate ventilation. Activated charcoal can be administered if the patient presents within 1 hour of ingestion. Oral or intravenous fluids should be given to optimize intravascular volume. Hypokalemia and hypoglycemia should be corrected. Urinary alkalinization with intravenous sodium bicarbonate can enhance the elimination of aspirin in the urine. In severe cases, hemodialysis may be necessary.

Urinary alkalinization involves targeting a urinary pH of 7.5-8.5 and checking it hourly. It is important to monitor for hypokalemia as alkalinization can cause potassium to shift from plasma into cells. Potassium levels should be checked every 1-2 hours.

In cases where the salicylate concentration is high (above 500 mg/L in adults or 350 mg/L in children), sodium bicarbonate can be administered intravenously. Hemodialysis is the treatment of choice for severe poisoning and may be indicated in cases of high salicylate levels, resistant metabolic acidosis, acute kidney injury, pulmonary edema, seizures and coma.

Thiazide diuretics, like bendroflumethiazide and hydrochlorothiazide, have the potential to raise levels of uric acid in the blood, which can worsen gout symptoms in individuals who are susceptible to the condition.

Other medications, such as diuretics, beta-blockers, ACE inhibitors, and non-losartan ARBs, are also linked to an increased risk of gout.

On the other hand, calcium-channel blockers like amlodipine and verapamil, as well as losartan, have been found to lower uric acid levels and are associated with a reduced risk of gout.

Potassium-sparing diuretics, like spironolactone and amiloride, can raise the chances of developing hyperkalemia when taken alongside ACE inhibitors, such as ramipril, and angiotensin-II receptor antagonists, like losartan.

For more information, you can refer to the BNF section on ramipril interactions.

Extrapyramidal side effects refer to drug-induced movements that encompass acute dyskinesias and dystonic reactions, tardive dyskinesia, Parkinsonism, akinesia, akathisia, and neuroleptic malignant syndrome. These side effects occur due to the blockade or depletion of dopamine in the basal ganglia, leading to a lack of dopamine that often resembles idiopathic disorders of the extrapyramidal system.

The primary culprits behind extrapyramidal side effects are the first-generation antipsychotics, which act as potent antagonists of the dopamine D2 receptor. Among these antipsychotics, haloperidol and fluphenazine are the two drugs most commonly associated with extrapyramidal side effects. On the other hand, second-generation antipsychotics like olanzapine have lower rates of adverse effects on the extrapyramidal system compared to their first-generation counterparts.

While less frequently, other medications can also contribute to extrapyramidal symptoms. These include certain antidepressants, lithium, various anticonvulsants, antiemetics, and, in rare cases, oral contraceptive agents.

There is an increased risk of neural tube defects in women with epilepsy who take carbamazepine during pregnancy, ranging from 2 to 10 times higher. Additionally, there is a risk of haemorrhagic disease of the newborn associated with this medication. It is crucial to have discussions about epilepsy treatments with women of childbearing age during the planning stages so that they can start early supplementation of folic acid.

Below is a list outlining the most commonly encountered drugs that have adverse effects during pregnancy:

ACE inhibitors (e.g. ramipril): If given in the second and third trimester, these medications can cause hypoperfusion, renal failure, and the oligohydramnios sequence.

Aminoglycosides (e.g. gentamicin): These drugs can lead to ototoxicity and deafness in the fetus.

Aspirin: High doses of aspirin can cause first-trimester abortions, delayed onset labor, premature closure of the fetal ductus arteriosus, and fetal kernicterus. However, low doses (e.g. 75 mg) do not pose significant risks.

Benzodiazepines (e.g. diazepam): When given late in pregnancy, these medications can result in respiratory depression and a neonatal withdrawal syndrome.

Calcium-channel blockers: If given in the first trimester, these drugs can cause phalangeal abnormalities. If given in the second and third trimesters, they can lead to fetal growth retardation.

Carbamazepine: This medication is associated with haemorrhagic disease of the newborn and neural tube defects.

Chloramphenicol: Use of this drug can cause grey baby syndrome in newborns.

Corticosteroids: If given in the first trimester, corticosteroids may cause orofacial clefts in the fetus.

Danazol: When administered in the first trimester, danazol can cause masculinization of the female fetuses genitals.

Finasteride: Pregnant women should avoid handling finasteride tablets. Crushed or broken tablets can be absorbed through the skin and affect male sex organ development in the fetus.

Haloperidol: If given in the first trimester, haloperidol may cause limb malformations. In the third trimester, there is an increased risk of extrapyramidal symptoms in the neonate.

Heparin: Use of heparin during pregnancy is associated with an acceptable bleeding rate and a low rate of thrombotic recurrence in the mother.

The use of low-dose aspirin during pregnancy is considered safe and can be used to manage recurrent miscarriage, clotting disorders, and pre-eclampsia. On the other hand, high-dose aspirin carries several risks, especially if used in the third trimester. These risks include delayed onset of labor, premature closure of the fetal ductus arteriosus, and fetal kernicterus (a condition that affects the brain due to high levels of bilirubin). Additionally, there is a slight increase in the risk of first-trimester abortion if high-dose aspirin is used early in pregnancy.

Below is a list outlining commonly encountered drugs that have adverse effects during pregnancy:

Drug: ACE inhibitors (e.g. ramipril)
Adverse effects: If given in the second and third trimester, ACE inhibitors can cause hypoperfusion, renal failure, and the oligohydramnios sequence.

Drug: Aminoglycosides (e.g. gentamicin)
Adverse effects: Aminoglycosides can cause ototoxicity (damage to the ear) and deafness.

Drug: Aspirin
Adverse effects: High doses of aspirin can cause first-trimester abortions, delayed onset of labor, premature closure of the fetal ductus arteriosus, and fetal kernicterus. However, low doses (e.g. 75 mg) have no significant associated risk.

Digoxin-specific antibody (DigiFab) is an antidote used to counteract digoxin overdose. It is a purified and sterile preparation of digoxin-immune ovine Fab immunoglobulin fragments. These fragments are derived from healthy sheep that have been immunized with a digoxin derivative called digoxin-dicarboxymethoxylamine (DDMA). DDMA is a digoxin analogue that contains the essential cyclopentanoperhydrophenanthrene: lactone ring moiety coupled to keyhole limpet hemocyanin (KLH).

DigiFab has a higher affinity for digoxin compared to the affinity of digoxin for its sodium pump receptor, which is believed to be the receptor responsible for its therapeutic and toxic effects. When administered to a patient who has overdosed on digoxin, DigiFab binds to digoxin molecules, reducing the levels of free digoxin in the body. This shift in equilibrium away from binding to the receptors helps to reduce the cardiotoxic effects of digoxin. The Fab-digoxin complexes are then eliminated from the body through the kidney and reticuloendothelial system.

The indications for using DigiFab in cases of acute and chronic digoxin toxicity are summarized below:

Acute digoxin toxicity:
– Cardiac arrest
– Life-threatening arrhythmia
– Potassium level >5 mmol/l
– Ingestion of >10 mg of digoxin (in adults)
– Ingestion of >4 mg of digoxin (in children)
– Digoxin level >12 ng/ml

Chronic digoxin toxicity:
– Cardiac arrest
– Life-threatening arrhythmia
– Significant gastrointestinal symptoms
– Symptoms of digoxin toxicity in the presence of renal failure

Statins, although generally safe and well-tolerated, can cause myopathy and myotoxicity. This range of muscle-related side effects can vary from mild muscle pain to the most severe case of rhabdomyolysis, which can lead to kidney failure, blood clotting issues, and even death.

The different levels of myotoxicity associated with statins are as follows:
– Myalgia: muscle symptoms without an increase in creatine kinase (CK) levels.
– Asymptomatic myopathy: elevated CK levels without muscle symptoms.
– Myositis: muscle symptoms with CK levels elevated less than 10 times the upper limit of normal.
– Rhabdomyolysis: muscle symptoms with CK levels elevated more than 10 times the upper limit of normal, potentially leading to myoglobinuria (presence of myoglobin in urine) and renal failure.

Most statins are broken down by the cytochrome P450 enzyme system. When taken with drugs that strongly inhibit this system, the concentration of statins in the blood can significantly increase. This, in turn, raises the risk of myopathy. A well-known example of this is the combination of statins with macrolide antibiotics like erythromycin and clarithromycin. Co-prescribing these drugs with statins has been linked to a higher risk of myopathy, hospitalization due to rhabdomyolysis, acute kidney injury, and increased mortality rates.