New-onset diabetes in an 8-year-old: sequencing fluids, insulin and potassium
Noa, 8 years old, 26 kg, is brought to the emergency department at 02:00. For three days she has had polyuria and polydipsia and for two days vomiting and abdominal pain; today she is drowsy with deep sighing respirations and fruity breath. She is thin, mucous membranes are dry, capillary refill is 3 seconds, HR 132, RR 34, BP 96/58, temperature 37.0 °C, weight 26 kg (pre-illness 28 kg), GCS 14. Capillary glucose 31 mmol/L, venous pH 7.09, bicarbonate 8 mmol/L, sodium 131, potassium 5.4, chloride 98, urea 9.8 mmol/L, blood ketones 5.2 mmol/L, urine ketones large. The paediatric intensive care unit is a 40-minute transfer away and only one infusion pump is free.
1. What is the diagnosis and severity, and in what order do you act in the first hour? Justify the sequence.
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This is diabetic ketoacidosis in new-onset type 1 diabetes, severe (pH 7.09, bicarbonate 8, ketones 5.2, 7.7% weight loss, drowsy) with clinical dehydration but not yet shock (BP 96/58, refill 3 seconds).
Order of actions:
- Airway, breathing, circulation, monitoring: continuous cardiac monitor, oxygen if needed, hourly neurological observations, two IV lines, weigh her, document baseline GCS.
- Confirm the diagnosis: venous gas, glucose, ketones, electrolytes, urea, full blood count, and treat the potassium and sodium from the same sample.
- Fluids first, insulin second: 10 mL/kg (260 mL) 0.9% sodium chloride over 30–60 minutes for volume expansion. Reassess after the bolus - if she remains shocked, the bolus can be repeated; otherwise move to rehydration over 48 hours with an isotonic solution plus maintenance, avoiding rapid changes.
- Insulin after about an hour of fluid, as a continuous infusion 0.05–0.1 units/kg/hour. Do not give a subcutaneous bolus of rapid-acting insulin in a child with severe DKA.
- Do not start insulin before you have thought about potassium (see next answer), and never give bicarbonate routinely.
- Escalate early: discuss with the paediatrician/retrieval service now; the 40-minute transfer and single pump are planning problems, not reasons to delay fluid or monitoring.
Document the time of each step - timing is the audit measure.
2. Potassium is 5.4 mmol/L. What happens to it once insulin starts, and how do you manage it?
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In DKA the serum potassium is falsely reassuring: total body potassium is depleted through osmotic diuresis and vomiting, and the measured 5.4 reflects insulin deficiency, acidosis and hyperosmolality shifting potassium out of cells.
Once insulin is started and the acidosis corrects, potassium moves rapidly back into cells and can fall precipitously - hypokalaemia with arrhythmia is one of the classic causes of death in paediatric DKA.
Management:
- Do not start insulin if potassium is below 3.5 mmol/L - replace potassium first, then start insulin.
- At 5.4 mmol/L, insulin may be started without added potassium, but the potassium must be rechecked within one hour of starting the infusion, then at least every 2–4 hours, and with any change in clinical state.
- Once potassium falls to the normal range, add potassium chloride to the rehydration fluid as prescribed (commonly 40 mmol/L, adjusted to the measured value and the fluid rate).
- Run the infusion on a pump, keep the cardiac monitor on, and know the ECG signs of hypokalaemia (flat T waves, U waves, arrhythmia).
- Also watch the sodium: as glucose falls, the measured sodium should rise. A falling sodium with improving glucose is a warning of cerebral oedema and free-water excess.
- Minimise the number of fluid bags and pumps that two nurses must double-check at 03:00 - concentration errors here are lethal; use a standardised DKA chart.
3. Two hours after starting insulin she develops a severe headache, becomes more drowsy and vomits again. HR 58, BP 128/86. What is happening and what do you do?
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This is cerebral oedema until proven otherwise - the leading cause of death in paediatric DKA. The red flags are precisely these: headache, deteriorating conscious level, vomiting, and the Cushing response of bradycardia with hypertension. Note that her BP was 96/58 and is now 128/86 with a heart rate of 58 - that is the change that matters, not the absolute numbers.
Immediate actions:
- Call for urgent senior help (paediatrician/anaesthetist) and prepare for airway support.
- Reduce the fluid infusion rate and stop any bolus.
- Give hypertonic treatment immediately as prescribed - 3% sodium chloride 2.5–5 mL/kg over 10–15 minutes or mannitol 0.5–1 g/kg - do not wait for imaging. In a 26 kg child that is roughly 65–130 mL of 3% saline.
- Head up 30 degrees, maintain oxygenation, treat fever, avoid hypotonic fluids.
- Do not delay treatment to obtain a CT; image only once she is stabilised, because an early scan does not exclude the diagnosis.
- Neurological observations every 15 minutes, pupils, glucose and electrolytes, and document the time of each intervention.
Afterwards: review the whole course - the fluid rate, whether drops in sodium or glucose occurred too fast, and whether the insulin rate was appropriate. Report it as a critical incident and debrief the team and the family.