DKA and HHS — Written Clinical Reasoning

SAQ 1 — Severe DKA: Diagnosis, Protocol, and Complications (20 marks, 30 minutes)

Prompt: Establish the diagnosis with severity grading, calculate the anion gap and corrected sodium, construct a complete management plan following the JBDS protocol with drug doses and monitoring targets, and discuss the complications you must anticipate with their prevention and recognition. [1]

Model Answer

Diagnosis and severity (3 marks): [1]

This is severe diabetic ketoacidosis. The diagnosis is confirmed by all four criteria: glucose above 11 (31 mmol/L), ketones above 3 (beta-hydroxybutyrate 7.8), venous pH below 7.3 (6.98), and bicarbonate below 15 (6 mmol/L). The precipitant is insulin omission — he stopped his insulin two days ago. The severity grade is severe because the pH is below 7.0 and the bicarbonate is below 10. This warrants ICU admission. [1]

Anion gap and corrected sodium (2 marks): [1]

Anion gap = sodium minus chloride minus bicarbonate = 130 minus 92 minus 6 = 32 (markedly elevated; normal 8-12). This confirms a high-anion-gap metabolic acidosis, consistent with ketoacidosis. [1]

Corrected sodium = measured sodium + 0.4 x (glucose minus 5.5) = 130 + 0.4 x (31 minus 5.5) = 130 + 0.4 x 25.5 = 130 + 10.2 = about 140 mmol/L. The corrected sodium is normal, which means 0.9% saline is the appropriate fluid choice (not 0.45%, which would be used if the corrected sodium were high). [1]

Management plan — the JBDS protocol (12 marks): [1]

1. Resuscitate and monitor (2 marks): ABCDE, oxygen, two large-bore cannulae, continuous cardiac monitoring, hourly glucose and potassium, two-hourly ketones and venous gas. A urinary catheter if the patient is oliguric or unable to pass urine. Move to ICU given the severe grade. [1]

2. Fluid resuscitation (3 marks): Start 0.9% saline immediately — 1 litre in the first hour, then 1 litre over 2 hours, then 1 litre over 2 hours, then 1 litre over 4 hours, with reassessment at each stage. Fluid is the first and most important intervention; it lowers glucose by restoring perfusion and switching off the osmotic diuresis before insulin is even started. [1]

3. Fixed-rate intravenous insulin infusion (3 marks): Start after the first litre of fluid and once potassium is confirmed safe (it is 5.8, so safe to proceed). FRIII at 0.1 units/kg/hour of soluble human insulin (Actrapid). Make up 50 units in 50 mL of 0.9% saline. For a 70 kg patient, this is 7 units/hour. The goal is ketogenesis suppression — target a fall in ketones of at least 0.5 mmol/L/hour and a rise in bicarbonate of 3 mmol/L/hour. No loading bolus. [1]

4. Potassium management (2 marks): The potassium is 5.8, which is above 5.5, so no potassium is added to the first bag. However, insulin will drive potassium into cells and the level will fall rapidly — check hourly. Once the potassium drops below 5.5, switch to 0.9% saline with 40 mmol/L potassium. Target range 4-5.5 mmol/L. [1]

5. Dextrose switch (1 mark): When the glucose falls below 14 mmol/L, switch the fluid to 10% dextrose at 125 mL/hour while continuing the FRIII unchanged. Consider reducing the FRIII to 0.05 units/kg/hour if the glucose is falling faster than 3 mmol/L/hour. [1]

6. Investigate and treat the precipitant (1 mark): Insulin omission is the precipitant here, but I would still screen for an intercurrent infection (blood cultures, urine culture, chest X-ray) and do an ECG and troponin. The diabetes and mental health team should review to address the reasons for insulin omission and to prevent recurrence. [1]

Complications to anticipate (3 marks): [1]

1. Cerebral oedema: He is 19, within the higher-risk age group. Watch for headache, vomiting, drowsiness, bradycardia, rising blood pressure. The Glaser study identified low initial PaCO2 (he has 14, very low), high urea (he has 12), and bicarbonate administration as risk factors [2]. I will NOT give bicarbonate. If cerebral oedema is suspected, reduce fluids, give mannitol 0.5-1 g/kg or 3% saline, and move to ICU.

2. Hypokalaemia: The potassium is currently 5.8 but will fall. I will check hourly and replace aggressively. This is the most dangerous metabolic complication — hypokalaemic arrhythmia is a leading cause of death during treatment. [1]

3. Hypoglycaemia: I will switch to dextrose at glucose below 14 and reduce the FRIII if the fall is too rapid. Hourly glucose monitoring is mandatory. [1]

Communication (1 mark): I will explain to the patient and his mother that this is a life-threatening condition caused by stopping insulin, that the treatment takes about 24 hours with close monitoring in ICU, and that the diabetes team will work with him on sick-day rules (never stop insulin during illness — you often need more) and on the reasons for the omission. [1]