Endocrine and diabetes medicines OSCE — DKA insulin and fluid prescribing with family counselling

Candidate brief

You have 10 minutes. [4]

1. Sequence the immediate fluid and insulin prescribing for this child's diabetic ketoacidosis, including the insulin infusion rate and the rule on insulin boluses. [4]
2. Explain to the examiner why insulin — not fluids or bicarbonate — is the definitive treatment, and why a steep glucose fall is avoided. [4] [9]
3. Outline the transition from intravenous insulin back to a subcutaneous regimen, including the insulin classes you would choose. [1]
4. Explain the pump-failure and sick-day safety plan to her mother in language she can repeat back. [1]

Scripted clinical data

• 7-year-old girl, previously well, three weeks of polyuria, polydipsia and weight loss, now vomiting and drowsy. [4]
• Weight 24 kg, heart rate 130, capillary refill 2 seconds, blood pressure normal, deep sighing Kussmaul respirations, GCS 14. [4]
• Bedside glucose 24 mmol per L, blood ketones 6.2 mmol per L, venous pH 7.08, bicarbonate 8 mmol per L. [4]
• Assessed as 7 percent dehydrated but not in shock. [4]
• The family plans to use an insulin pump after recovery; mother is anxious and a professional interpreter is available. [1]

Expected performance

Excellent — Sequences fluids before insulin correctly (isotonic saline resuscitation or calculated deficit replacement; bolus only if shocked), then states the intravenous insulin infusion at 0.05 to 0.1 unit per kg per hour after volume restoration, and explicitly rejects an insulin bolus with the cerebral-oedema rationale. [4] [9]

Explains that insulin switches off ketogenesis by restoring glucose uptake and suppressing lipolysis, and that a steep glucose fall is avoided by adding dextrose to keep the fall gradual and protect the brain. [4] [9]

Plans the transition: clear ketones and a normal pH first, then overlap the subcutaneous basal insulin before stopping the infusion, and build a basal-bolus regimen of a once-daily long-acting analogue (glargine, detemir or degludec) plus a rapid-acting analogue (lispro, aspart or glulisine) with meals. [1]

Counsels the mother that the pump uses only rapid-acting insulin with no basal reserve, so a kink or empty reservoir causes ketones and DKA within hours; gives a ketone-check and pump-failure plan with a back-up injection regimen; confirms the never-stop-insulin sick-day rule; and uses the interpreter and teach-back. [1]

Pass — States insulin after fluids at roughly the right rate and rejects a bolus, but may miss the dextrose or potassium detail, the overlap on transition, or one element of the family counselling. [4]

Borderline — Starts insulin before adequate fluid resuscitation, or accepts an insulin bolus, or cannot explain why insulin stops ketogenesis; unsafe practice requiring correction. [4] [9]

Marking domains

• Clinical reasoning (4): correct fluid-before-insulin sequence; correct infusion rate; correct no-bolus rationale; correct transition overlap.
• Pharmacological knowledge (3): insulin classes named correctly; rationale for insulin as definitive treatment; dextrose and potassium management.
• Safety and communication (2): pump-failure and sick-day plan taught with teach-back; interpreter used appropriately.
• Professionalism (1): calm, structured, family-centred; acknowledges and corrects an unsafe suggestion. [1] [4]