Salicylate poisoning initially leads to respiratory alkalosis, followed by metabolic acidosis. Salicylates, like aspirin, stimulate the respiratory center in the medulla, causing hyperventilation and respiratory alkalosis. This is usually the first acid-base imbalance observed in salicylate poisoning. As aspirin is metabolized, it disrupts oxidative phosphorylation in the mitochondria, leading to an increase in lactate levels due to anaerobic metabolism. The accumulation of lactic acid and acidic metabolites then causes metabolic acidosis.

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.

Calcium-channel blocker overdose is a serious condition that can be life-threatening. The most dangerous types of calcium channel blockers in overdose are verapamil and diltiazem. These medications work by binding to the alpha-1 subunit of L-type calcium channels, which prevents the entry of calcium into cells. These channels are important for the functioning of cardiac myocytes, vascular smooth muscle cells, and islet beta-cells.

When managing a patient with calcium-channel blocker overdose, it is crucial to follow the standard ABC approach for resuscitation. If there is a risk of life-threatening toxicity, early intubation and ventilation should be considered. Invasive blood pressure monitoring is also necessary if hypotension and shock are developing.

The specific treatments for calcium-channel blocker overdose primarily focus on supporting the cardiovascular system. These treatments include:

1. Fluid resuscitation: Administer up to 20 mL/kg of crystalloid solution.

2. Calcium administration: This can temporarily increase blood pressure and heart rate. Options include 10% calcium gluconate (60 mL IV) or 10% calcium chloride (20 mL IV) via central venous access. Repeat boluses can be given up to three times, and a calcium infusion may be necessary to maintain serum calcium levels above 2.0 mEq/L.

3. Atropine: Consider administering 0.6 mg every 2 minutes, up to a total of 1.8 mg. However, atropine is often ineffective in these cases.

4. High dose insulin – euglycemic therapy (HIET): The use of HIET in managing cardiovascular toxicity has evolved. It used to be a last-resort measure, but early administration is now increasingly recommended. This involves giving a bolus of short-acting insulin (1 U/kg) and 50 mL of 50% glucose IV (unless there is marked hyperglycemia). Therapy should be continued with a short-acting insulin/dextrose infusion. Glucose levels should be monitored frequently, and potassium should be replaced if levels drop below 2.5 mmol/L.

5. Vasoactive infusions: Catecholamines such as dopamine, adrenaline, and/or noradrenaline can be titrated to achieve the desired inotropic and chronotropic effects.

6. Sodium bicarbonate: Consider using sodium bicarbonate in cases where a severe metabolic acidosis develops.

Activated charcoal prevents the absorption of poisons by absorbing them onto its surface through weak electrostatic forces.

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.

Fluoroquinolones are a rare but acknowledged cause of tendinopathy and spontaneous tendon rupture. It is estimated that tendon disorders related to fluoroquinolones occur in approximately 15 to 20 out of every 100,000 patients. These issues are most commonly observed in individuals who are over the age of 60.

The Achilles tendon is the most frequently affected, although cases involving other tendons such as the quadriceps, peroneus brevis, extensor pollicis longus, the long head of biceps brachii, and rotator cuff tendons have also been reported. The exact underlying mechanism is not fully understood, but it is believed that fluoroquinolone drugs may hinder collagen function and/or disrupt blood supply to the tendon.

There are other risk factors associated with spontaneous tendon rupture, including corticosteroid therapy, hypercholesterolemia, gout, rheumatoid arthritis, long-term dialysis, and renal transplantation.

When furosemide and SSRI drugs are prescribed together, there is a higher chance of developing hyponatraemia, which is a condition characterized by low levels of sodium in the blood. Additionally, there is an increased risk of hypokalaemia, which can potentially lead to a dangerous heart rhythm disorder called torsades de pointes. It is important to note that co-prescribing furosemide with citalopram should be avoided due to these risks. For more information, you can refer to the section on furosemide interactions in the BNF.

Arterial blood gas (ABG) interpretation is essential for evaluating a patient’s respiratory gas exchange and acid-base balance. The normal values on an ABG may slightly vary between analyzers, but generally, they fall within the following ranges:

pH: 7.35 – 7.45
pO2: 10 – 14 kPa
PCO2: 4.5 – 6 kPa
HCO3-: 22 – 26 mmol/l
Base excess: -2 – 2 mmol/l

In this particular case, the patient’s history indicates an overdose. However, there is no immediate need for intubation as her Glasgow Coma Scale (GCS) score is 11/15, and she can speak, albeit with slurred speech, indicating that she can maintain her own airway.

The relevant ABG findings are as follows:

– Mild hypoxia
– Decreased pH (acidaemia)
– Low PCO2
– Normal bicarbonate
– Elevated lactate

The anion gap is a measure of the concentration of unmeasured anions in the plasma. It is calculated by subtracting the primary measured cations from the primary measured anions in the serum. The reference range for anion gap varies depending on the methodology used, but it is typically between 8 to 16 mmol/L.

In this case, the patient’s anion gap can be calculated using the formula:

Anion gap = [Na+] – [Cl-] – [HCO3-]

Using the given values:

Anion gap = [143] – [99] – [22]
Anion gap = 22

Therefore, it is evident that she has a raised anion gap metabolic acidosis. It is likely a type A lactic acidosis resulting from tissue hypoxia and hypoperfusion. Some potential causes of type A and type B lactic acidosis include:

Type A lactic acidosis:
– Shock (including septic shock)
– Left ventricular failure
– Severe anemia
– Asphyxia
– Cardiac arrest
– Carbon monoxide poisoning
– Respiratory failure
– Severe asthma and COPD
– Regional hypoperfusion

Type B lactic acidosis:
– Renal failure
– Liver failure
– Sepsis (non-hypoxic sepsis)
– Thiamine deficiency
– Al

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.

Antipsychotics and antidepressants are drugs that are known to cause QT prolongation, which is a potentially dangerous heart rhythm abnormality. Similarly, SSRIs and other antidepressants are also associated with QT prolongation. On the other hand, beta-blockers like bisoprolol are used to shorten the QT interval and are considered as a treatment option for long QT syndrome. However, it’s important to note that sotalol, although classified as a beta blocker, acts differently by blocking potassium channels. This unique mechanism of action makes sotalol a class III anti-arrhythmic agent and may result in QT interval prolongation.

Further Reading:

Long QT syndrome (LQTS) is a condition characterized by a prolonged QT interval on an electrocardiogram (ECG), which represents abnormal repolarization of the heart. LQTS can be either acquired or congenital. Congenital LQTS is typically caused by gene abnormalities that affect ion channels responsible for potassium or sodium flow in the heart. There are 15 identified genes associated with congenital LQTS, with three genes accounting for the majority of cases. Acquired LQTS can be caused by various factors such as certain medications, electrolyte imbalances, hypothermia, hypothyroidism, and bradycardia from other causes.

The normal QTc values, which represent the corrected QT interval for heart rate, are typically less than 450 ms for men and less than 460ms for women. Prolonged QTc intervals are considered to be greater than these values. It is important to be aware of drugs that can cause QT prolongation, as this can lead to potentially fatal arrhythmias. Some commonly used drugs that can cause QT prolongation include antimicrobials, antiarrhythmics, antipsychotics, antidepressants, antiemetics, and others.

Management of long QT syndrome involves addressing any underlying causes and using beta blockers. In some cases, an implantable cardiac defibrillator (ICD) may be recommended for patients who have experienced recurrent arrhythmic syncope, documented torsades de pointes, previous ventricular tachyarrhythmias or torsades de pointes, previous cardiac arrest, or persistent syncope. Permanent pacing may be used in patients with bradycardia or atrioventricular nodal block and prolonged QT. Mexiletine is a treatment option for those with LQT3. Cervicothoracic sympathetic denervation may be considered in patients with recurrent syncope despite beta-blockade or in those who are not ideal candidates for an ICD. The specific treatment options for LQTS depend on the type and severity of the condition.

Common side effects of bendroflumethiazide include postural hypotension, electrolyte disturbance (such as hypokalaemia, hyponatraemia, and hypercalcaemia), impaired glucose tolerance, gout, impotence, and fatigue. Rare side effects of bendroflumethiazide include thrombocytopenia, agranulocytosis, photosensitive rash, pancreatitis, and renal failure.

Activated charcoal is a commonly utilized substance for decontamination in cases of poisoning. Its main function is to attract and bind molecules of the ingested toxin onto its surface.

Activated charcoal is a chemically inert form of carbon. It is a fine black powder that has no odor or taste. This powder is created by subjecting carbonaceous matter to high heat, a process known as pyrolysis, and then concentrating it with a solution of zinc chloride. Through this process, the activated charcoal develops a complex network of pores, providing it with a large surface area of approximately 3,000 m2/g. This extensive surface area allows it to effectively hinder the absorption of the harmful toxin by up to 50%.

The typical dosage for adults is 50 grams, while children are usually given 1 gram per kilogram of body weight. Activated charcoal can be administered orally or through a nasogastric tube. It is crucial to administer it within one hour of ingestion, and if necessary, a second dose may be repeated after one hour.