Which ONE of the following conditions is associated with hypokalaemia?
Answer: B: Hypokalaemia is defined as a [K+ ] of <3.5 mmol/L. It is most frequently caused by intracellular shifts and increased losses of potassium. There are multiple aetiologies for hypokalaemia one of which is metabolic alkalosis. As the pH of the extracellular fluid rises, potassium shifts into the cells in exchange for hydrogen ions thereby causing hypokalaemia. Therefore, most causes of metabolic alkalosis will also cause a hypokalaemia due to redistribution. Addisonian crisis, digoxin overdose and beta-blockers all cause hyperkalaemia.
References:
A 48-year-old alcoholic man presents to the ED after an episode of syncope. An ECG is performed that shows a QTc of 523 ms.
Which ONE of the following electrolyte imbalances would LEAST likely be a cause for his prolonged QTc?
Answer: C: There are several causes of prolonged QTc:
Consequently, in alcoholics there are also multiple reasons for a prolonged QTc finding. However, hyponatraemia while common in alcoholics, does not typically cause a prolonged QTc.
Reference:
Which ONE of the following ECG findings would you LEAST expect to see in a patient with hyperkalaemia?
Answer: B: Clinical manifestations of hyperkalaemia result from changes in the transmembrane potential. Cardiac cells are particularly vulnerable and more sensitive in acute changes in potassium levels. ECG changes are characteristic (see Table below), however, an insensitive method in evaluating the degree of hyperkalaemia. In chronic hyperkalaemia, ECG changes tend to occur at higher potassium levels.
ECG CHANGES ACCORDING TO POTASSIUM LEVELS:
Which ONE of the following is NOT a potential complication in the treatment of metabolic acidosis with sodium bicarbonate?
Answer: A: The role of bicarbonate therapy in the treatment of acidosis is still controversial and is currently reserved for use primarily in severe acidosis. Bicarbonate therapy imposes a high osmotic and sodium load that may precipitate pulmonary oedema and volume overload. It also is responsible for generating large quantities of carbon dioxide that can diffuse into the CSF and into cells causing a paradoxical intracellular and CSF acidosis. The extra carbon dioxide can also cause respiratory failure. Other side effects include overshoot alkalosis, hypokalaemia and precipitation of hypocalcaemia.
Some literature reviews have focused on the use of bicarbonate therapy in cardiac arrest, DKA and lactic acidosis. Several studies have failed to show benefit or reduced complication rates with the use of bicarbonate and other studies have found that use in patients with severe cardiac disease may have deleterious effect from the therapy. In hypoxic tissues, bicarbonate therapy can further increase the production of lactate (due to removal of glycolysis inhibition from acidotic state) and impair the removal of oxygen from haemoglobin due to increased pH (left shift of the oxygen dissociation curve), thereby causing negative effects.
Which ONE of the following conditions is NOT an indication for the use of bicarbonate therapy in metabolic acidosis?
Answer: C: The treatment of metabolic acidosis should be directed at treating the primary cause and the use of intravenous bicarbonate therapy should be reserved only for a few cases. These indications include:
Clinical studies have shown that bicarbonate is not indicated in DKA because it shows no beneficial effect in outcome, and may in fact slow the clearance of ketones. Additionally, as mentioned above, lactic acidosis may actually worsen if bicarbonate is administered.
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