Endocrine and diabetes medicines — formative SAQs

SAQ 1 — Diabetic ketoacidosis: the insulin and fluid prescribing sequence (10 marks)

A 7-year-old with previously undiagnosed type 1 diabetes presents drowsy with deep sighing respirations. Bedside glucose is 24 mmol per L, blood ketones 6.2 mmol per L, and venous pH 7.08. She is 7 percent dehydrated but not in shock. ^{[4] [9]}

Questions

1. Outline the immediate fluid and insulin prescribing sequence for her resuscitation, including the insulin rate, the timing of insulin relative to fluids, and the rule on insulin boluses. (6 marks) ^[4]
2. Explain the pharmacological rationale for why insulin is the definitive treatment of DKA, and why a steep glucose fall is avoided. (4 marks) ^{[4] [9]}

Model answer

Fluid and insulin sequence (6). First restore intravascular volume: an isotonic saline bolus of 10 to 20 mL per kg is given only if the child is in shock; otherwise begin a calculated deficit replacement over 24 to 48 hours with isotonic saline, as she is dehydrated but not shocked. Only after intravascular volume is restored, start a continuous intravenous insulin infusion at 0.05 to 0.1 unit per kg per hour using soluble or rapid-acting insulin. Do not give an intravenous insulin bolus at any point, because a bolus drives a steep osmolar fall that contributes to cerebral oedema. Replace potassium once insulin starts and urine output is established, and add dextrose to the fluids when the glucose falls to around 11 to 14 mmol per L to keep the glucose fall gradual. Transition to subcutaneous insulin only when ketones have cleared, the pH has normalised, and the child is eating. ^{[4] [9]}

Rationale (4). DKA is an insulin-deficient state: without insulin, glucose cannot enter cells and lipolysis runs unchecked, flooding the liver with free fatty acids that it converts to ketone bodies, producing acidosis. Insulin reverses both arms at once — it restores glucose uptake, suppressing hyperglycaemia, and it switches off lipolysis, stopping ketogenesis — which is why insulin (not fluids or bicarbonate) is the definitive treatment. A steep glucose fall is avoided because it generates a rapid osmolar shift that, alongside the cerebral hypoperfusion of dehydration, contributes to cerebral oedema, the leading cause of DKA-related death in children. Gradual glucose control with dextrose support protects the brain. ^{[4] [9]}