Regarding the treatment of hyperkalemia in patients with renal failure, which ONE of the following statements is TRUE?
Answer: D: Intravenous insulin is the most reliable agent for shifting potassium into cells and is regarded as the first-line treatment for hyperkalaemia. Its onset of action is rapid within 15–30 minutes. β-receptor agonists have a similar onset of action and their effect has been shown to be additive to insulin administration. However, the effective dose is at least 4 times higher than typically used for bronchodilation. Salbutamol at doses of 10–20 mg is recommended via a nebuliser.
NaHCO3 has been routinely used in the management of hyperkalaemia in the prior decades. However, latest evidence suggests that it has no effect to shift K+ into cells, even after several hours. This, combined with the potential complication of increased sodium concentration and volume overload, especially relevant in patients with renal compromise, has recently caused the use of HCO3 to fall out of favour. Its use is no longer routinely recommended although it may still be appropriate in patients with severe metabolic acidosis.
Cation exchange resins promote elimination of total body potassium by gastrointestinal excretion as it binds K+ in the colon in exchange for sodium.
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Regarding the aetiology of rhabdomyolysis, which ONE of the following is TRUE?
Answer: C: The most common causes of rhabdomyolysis in adults are alcohol and drugs of abuse, followed by medications, muscle disease, trauma, neuroleptic malignant syndrome, seizures, immobility, infection, strenuous physical activity and heat-related illnesses. Alcohol and drugs play a role in up to 80% of adults. In many cases the aetiology is multifactorial. The most common causes in children are trauma, viral myositis and connective tissue disease. Rhabdomyolysis is an extremely rare (<1%) but life-threatening complication of statin therapy. The incidence varies with the particular statin, is doserelated and increases with dual therapy.
Influenza viruses A and B are the most commonly cited infectious causes and Legionella is the most frequently reported bacterial cause of rhabdomyolysis. Patients will classically give a history of a viral illness 1–2 weeks prior to the onset of myalgias and myoglobinuria.
Strenuous physical activity is another common cause. High force eccentric contraction as with strength training or heavy lifting leads to a greater breakdown in muscle and higher levels of CK than concentric contractions, such as endurance-based exercise.
Regarding the diagnosis of rhabdomyolysis, which ONE of the following is TRUE?
Answer: C: The classic clinical manifestations of rhabdomyolysis include myalgia, weakness and tea-coloured urine. Acute rhabdomyolysis may present without any of these symptoms and musculoskeletal symptoms may be present in as few as half of patients. The diagnosis of rhabdomyolysis therefore requires a high index of suspicion, particularly when patients present with an altered sensorium, and is confirmed by laboratory evaluation.
Serum myoglobin is an insensitive marker for rhabdomyolysis. The half-life of myoglobin in plasma is 1–3 hours and can be cleared completely from plasma within 6 hours after injury. Urine myoglobin is also excreted rapidly and may also be an inaccurate measure. Serum and urinary myoglobin may therefore be absent in patients who present late in the course of their illness.
An elevated CK is the most sensitive and reliable indicator of muscle injury. It is present in the serum almost immediately after muscle injury, is not rapidly cleared from serum (half-life is 1.5 days) with peak levels occurring within 24–36 hours of muscle injury. Rhabdomyolysis is not defined by a specific CK level. However, in the absence of cerebral or myocardial infarction, CK levels greater than five times normal is generally thought to be diagnostic and levels above 5000 U/L indicate serious muscle injury.
The degree of CK elevation correlates with the amount of muscle injury and severity of illness but not the development of renal failure or other morbidity. Patients may have significant morbidity with only moderately elevated CK levels. There is no defined threshold value of serum CK above which the risk of acute kidney injury is markedly increased. Furthermore, only a weak correlation between peak CK levels and the incidence of acute kidney injury has been reported and it seems that the risk of acute kidney injury is low when CK levels at admission are <15,000 to 20,000 U/L. The risk of renal failure increases with comorbid conditions such as sepsis, dehydration, and acidosis and acute kidney injury may occur under these circumstances at CK levels as low as 5000 U/L.
Additionally, it seems like an initially elevated serum urea and creatinine and a large base deficit have an increased risk for developing ARF.
Regarding haemolytic uremic syndrome (HUS) in children, which ONE of the following statements is TRUE?
Answer: D: HUS is primarily a disease of infancy and early childhood, especially of those aged between 6 months and 4 years and is rare after 5 years of age. It is classically characterised by the triad of microangiopathic haemolytic anaemia, thrombocytopaenia and ARF.
Two forms of HUS exist: epidemic (typical) and sporadic (atypical). The typical form is much more common and is associated with infectious diarrhoea. The shiga toxin (also called verotoxin) producing E. coli serotype O157:H7 has been associated with more than 80% of infections leading to HUS. Other infectious causes of HUS include Shigella organisms, Streptococcus pneumoniae, Aeromonas and HIV. In contrast, the sporadic form is not associated with diarrhoea but may have a genetic link. It has been associated with non-enteric infections such as invasive S. pneumoniae as well as noninfectious causes including drugs, malignancies, transplantation, pregnancy and other underlying medical conditions such as scleroderma and antiphospholipid syndrome. HUS continues to be one of the most common causes of ARF in children.
Unnecessary use of antibiotics or antimotility agents should be avoided during diarrhoeal illness as it may increase the risk of HUS. Antimotility agents slow gut motility and therefore the gut is exposed to the toxins for a longer period of time. Antibiotic-induced injury to the bacterial membrane favours the acute release of large amounts of toxins. The use of antibiotics has been shown to increase the risk of full-blown HUS by 17-fold and, therefore, the current recommendation is to avoid its use, except in cases of sepsis.
Which ONE of the following features is MOST consistent with HUS in children?
Answer: C: HUS is primarily a clinical diagnosis coupled with consistent laboratory findings. Patients usually present with watery diarrhoea and crampy abdominal pain. Fever is only present in about 30% of cases. From 2 to 3 days after onset of symptoms, patients experience increased abdominal pain with bloody stools, the latter developing in up to 89% of patients by day 5. Central nervous system irritability may develop in about 33% of patients and may result in seizures. Anaemia can be profound due to haemolysis and it is not uncommon for the haemoglobin levels to be 50–90 g/L.
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