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MCADD Anaesthesia — FRCA Final MCQ

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HardPaediatric AnaesthesiaMCADD AnaesthesiaFRCA Final

A 4-year-old child with confirmed medium-chain acyl-CoA dehydrogenase deficiency is scheduled for elective adenotonsillectomy. They are clinically well, but a theatre delay means that the safe fasting interval specified by the metabolic team has been exceeded. Capillary blood glucose is 4.8 mmol/L. Which is the most appropriate perioperative plan?

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Correct answer: B — Start 10% glucose-containing intravenous fluid now, monitor glucose regularly and continue carbohydrate provision until oral intake is reliably re-established

MCADD impairs mitochondrial β-oxidation of medium-chain fatty acyl-CoA and therefore limits ketone production when glycogen becomes depleted. Fasting and surgical stress can consequently cause rapid metabolic decompensation with hypoketotic hypoglycaemia. Hypoglycaemia is a late finding, so the normal glucose concentration must not delay treatment once the child's safe fasting interval has been exceeded. Proactive 10% glucose-containing intravenous fluid, glucose monitoring and continuation of carbohydrate until reliable feeding resumes are therefore required; the rate should be individualised with the metabolic team and adjusted to avoid hyperglycaemia. Carnitine is not an acute substitute for glucose. Neither volatile anaesthesia nor non-depolarising neuromuscular blockade is universally contraindicated, although quantitative neuromuscular monitoring is prudent. TIVA is not specifically required and does not itself prevent catabolism.

Reference: Allen C, Perkins R, Schwahn B. A retrospective review of anesthesia and perioperative care in children with medium-chain acyl-CoA dehydrogenase deficiency. Paediatric Anaesthesia. 2017;27:60–65. Abstract and conclusions. https://pubmed.ncbi.nlm.nih.gov/27896927/