DKA and HHS — Written Clinical Reasoning

SAQ 1 — Severe DKA (12 marks)

Prompt: A 19-year-old man with type 1 diabetes stopped his insulin two days ago. He is drowsy, with deep rapid breathing. Glucose 31 mmol/L, beta-hydroxybutyrate 7.8 mmol/L, venous pH 6.98, bicarbonate 6 mmol/L, potassium 5.8 mmol/L. Grade the severity and outline your first 12 hours of management. ^[1]

Model Answer

Diagnosis and severity (3 marks):

• DKA needs all three components: glucose of 11.1 mmol/L or more or known diabetes, raised ketones, and metabolic acidosis. ^[1]
• His biochemistry is in the consensus severe band: beta-hydroxybutyrate above 6.0 mmol/L, pH below 7.0 and bicarbonate below 10 mmol/L. Not all variables need to be fulfilled to define severity, and the suggested level of care for severe DKA is the intensive care unit. ^[1]
• Insufficient use of insulin is a common precipitant, but examine for infection, ischaemia and other precipitants and record an ECG. ^[1]

Fluids (2 marks):

• Isotonic saline or a balanced crystalloid at 500 to 1,000 mL/h for the first 2 to 4 hours, then guided by haemodynamics, fluid balance and sodium, correcting deficits within 24 to 48 hours. ^[1]

Insulin (3 marks):

• Start a fixed-rate intravenous insulin infusion at 0.1 units/kg/h as soon as possible. His potassium is above 3.5 mmol/L, so insulin need not be delayed. ^[1]
• When glucose falls below 13.9 mmol/L, add 5 to 10 percent dextrose and reduce the infusion to 0.05 units/kg/h, then keep glucose at about 11.1 mmol/L until the ketoacidosis resolves. ^[1]

Potassium (2 marks):

• Start replacement once potassium falls below 5.0 mmol/L, aiming for 4 to 5 mmol/L; 20 to 30 mmol per litre of fluid is enough for most patients. Check potassium 2 hours after starting insulin, then every 4 hours. ^[1]

Bicarbonate and monitoring (2 marks):

• Routine bicarbonate is not recommended, but it should be considered at pH below 7.0: 100 mmol of sodium bicarbonate in 400 mL of sterile water every 2 hours until pH is above 7.0. ^[1]
• In children, Glaser found that bicarbonate treatment, low arterial carbon dioxide and high serum urea nitrogen were associated with cerebral oedema. ^[5]
• Check capillary glucose every 1 to 2 hours, and electrolytes, phosphate, creatinine, beta-hydroxybutyrate and venous pH every 4 hours. Resolution is ketones below 0.6 mmol/L with venous pH of 7.3 or more, or bicarbonate of 18 mmol/L or more. ^[1]