High glucose, low potassium: sequencing treatment in diabetic ketoacidosis on a district ward
A 24-year-old man is brought to a district hospital at 02:00 after two days of vomiting and one day of drowsiness. He is breathing deeply at 30/min, pulse 120/min, BP 102/64 mmHg, capillary glucose 28 mmol/L, blood ketones 5.4 mmol/L. The point-of-care electrolyte machine gives sodium 130, potassium 3.1, bicarbonate 8 mmol/L, creatinine 140 µmol/L. GCS is 14 and he is passing small volumes of urine. There is no intensive care unit, no arterial blood gas analyser after hours, and one functioning oxygen concentrator. The nurse has already drawn up 50 units of soluble insulin in 50 mL and asks whether she should start the infusion now, because "the glucose is very high and he is breathing badly".
1. Should the insulin infusion be started now? Give your fluid, potassium and insulin plan for the first two hours, with numbers and decision points.
Read the worked answer
No - not yet. The potassium is 3.1 mmol/L. Insulin drives potassium into cells, and starting an infusion at this level can precipitate a fatal arrhythmia or respiratory muscle weakness. Correcting the potassium comes first.
First hour
- 0.9% sodium chloride 1 L over 1 hour (approximately 15 mL/kg).
- Add potassium chloride 40 mmol to that litre and run it on a pump or by gravity with a nurse at the bedside; a peripheral line is acceptable but the rate must be watched.
- Recheck potassium (and glucose) after the litre, ideally within 60–90 minutes.
- If the ECG monitor is available, watch for flat T waves and U waves.
Starting insulin
- Once potassium is ≥3.3 mmol/L, begin soluble insulin 0.1 units/kg/hour - for a 70 kg man this is 7 units/hour, so with the 1 unit/mL syringe already prepared, 7 mL/hour.
- Do not give an insulin bolus; there is no evidence it helps and it worsens hypokalaemia.
- Target a glucose fall of 3–5 mmol/L per hour. When glucose falls below 14 mmol/L, change the fluid to 5% dextrose in 0.45% saline (or 10% dextrose 100 mL/hour) and continue the insulin - the insulin is being given to clear ketones, not only to lower glucose.
- Continue potassium in every litre while he is on insulin, aiming for 4.0–5.5 mmol/L.
Second hour
- Second litre of 0.9% saline over 2 hours (slower once the initial deficit is partly corrected), with potassium.
- If systolic BP remains below 90 mmHg after 1 L, give a further rapid 500 mL and look for sepsis or a bleeding source.
- Bicarbonate is not indicated at these values.
2. Which two complications are you most likely to cause or to miss with the resources available, and how will you monitor for them without a blood gas analyser?
Read the worked answer
1. Hypokalaemia and its cardiac consequences. Insulin and fluids dilute and shift potassium. Monitor by hourly point-of-care potassium for the first 4–6 hours, then 2-hourly; watch for ileus, generalised weakness and shallow breathing; use the monitor if there is one. Never run a litre with potassium faster than the standard rate, and never give a concentrated bolus peripherally.
2. Fluid overload and cerebral oedema. He has a creatinine of 140 µmol/L and has been vomiting for two days; rapid large-volume resuscitation can flood him. Signs to chart half-hourly: respiratory rate and pattern, oxygen saturation, new basal crackles, raised JVP, falling GCS or new headache, unequal pupils, bradycardia with hypertension.
Working without gases
- Use the bicarbonate (8 mmol/L), the ketone reading, the anion gap from sodium, chloride and bicarbonate, and the clinical picture (Kussmaul breathing resolving, GCS improving, urine output) to judge response.
- Urine output via a catheter is the single most useful monitoring tool on this ward: aim for 0.5 mL/kg/hour.
- Record all observations on a formal chart with times; deterioration at 03:00 is usually spotted by a trend, not a single reading.
3. At what point would you arrange transfer to the regional hospital, and what must be done before and during transfer?
Read the worked answer
Triggers for transfer
- Potassium that cannot be held above 3.0 mmol/L despite replacement, or that rises above 5.5 mmol/L.
- GCS falling, new focal signs, or a headache with bradycardia and hypertension suggesting cerebral oedema.
- Persistent hypotension after 2 L of crystalloid, or oliguria.
- Bicarbonate below 5 mmol/L or a clinical picture of severe acidosis not improving after 4 hours.
- Any need for ventilator support, or a ward where hourly potassium cannot be guaranteed overnight because only one nurse is on duty.
Before departure
- Two functioning large-bore lines, first litre of fluid with potassium running, insulin infusion started only if potassium is ≥3.3.
- A written referral note with the time of each potassium, glucose, fluid volume and insulin rate, plus the weight and calculated doses.
- Oxygen cylinder, dextrose-containing fluid ready for when glucose drops below 14, glucose meter and ketone strips, and a nurse escort who can check a glucose and pump rate.
- Telephone the receiving unit first so a bed and a potassium machine are ready.
Judgement point: do not transfer a patient who is being successfully stabilised merely for a blood gas; the risk of a 3-hour rough-road journey in a patient with a potassium of 3.1 outweighs the information gained.