New-onset diabetic ketoacidosis in a 7-year-old boy
A 7-year-old boy is brought to the emergency department with 3 days of vomiting, abdominal pain and deep, rapid breathing. He has lost 3 kg over 6 weeks and has been drinking and urinating excessively. He is drowsy but rousable, with dry mucous membranes, heart rate 132/min, blood pressure 92/60 mmHg, respiratory rate 34/min, and capillary refill 3 seconds. Weight is 22 kg. Bedside glucose is 512 mg/dL. Venous blood gas: pH 7.09, pCO2 22 mmHg, bicarbonate 7 mmol/L. Sodium 131 mmol/L, potassium 5.6 mmol/L, chloride 98 mmol/L, urea 38 mg/dL, creatinine 0.7 mg/dL, beta-hydroxybutyrate 5.8 mmol/L. Urine dipstick shows 4+ ketones and 4+ glucose. He has not passed urine since arrival.
1. Set out your fluid and insulin plan with the reasoning behind the timing and rates.
Read the worked answer
He is dehydrated but not in shock: blood pressure is maintained, capillary refill is 3 seconds, and he is rousable. Give 10 mL/kg of 0.9% saline over 30-60 minutes and reassess, rather than repeating large boluses, because rapid fluid administration is associated with cerebral edema. Then begin rehydration calculated over 24-48 hours with 0.9% saline (some protocols use 0.45% saline with added potassium), including ongoing losses and urine output.
Start an insulin infusion at 0.05 units/kg/hr about 1 hour after fluids have begun. Do not give an insulin bolus and do not start subcutaneous insulin: bolus insulin increases the risk of cerebral edema and is not recommended in pediatric DKA. Add 5% dextrose to the rehydration fluid when glucose falls below 250-300 mg/dL, and continue insulin until the acidosis has resolved (pH above 7.30, bicarbonate above 15 mmol/L, beta-hydroxybutyrate below 1 mmol/L), not until glucose normalizes, because ketogenesis lags behind glycemia.
Bicarbonate is not indicated at pH 7.09: it shifts potassium intracellularly, may worsen cerebral edema, and does not improve outcome. Recheck blood gas, electrolytes and glucose hourly at first.
2. How do you manage the potassium and the sodium, given these values?
Read the worked answer
Potassium of 5.6 mmol/L looks high but reflects extracellular shift from insulin deficiency and acidosis, with total body depletion of roughly 3-5 mmol/kg. Do not add potassium until urine output is documented and the ECG shows no hyperkalemic changes, but do not wait for the value to fall into the normal range before replacing it: once insulin starts driving potassium intracellularly it will drop quickly, and hypokalemia can cause arrhythmia.
Once urine output is established, add 40 mmol/L potassium (as chloride with phosphate) to the rehydration fluid and check potassium every 2-4 hours, increasing the concentration if it falls below 4 mmol/L. Sodium of 131 mmol/L is largely dilutional from hyperglycemia and hypertriglyceridemia. Calculate the corrected sodium for glucose; if the corrected sodium rises during therapy rather than falling, that suggests inadequate free water replacement or developing hyperosmolality and is a warning sign.
Use isotonic fluid initially and avoid rapid hypotonic infusions. Monitor phosphate and magnesium as well, since hypophosphatemia can appear once insulin is running, and reassess the fluid prescription with each set of electrolytes.
3. Six hours into treatment he develops a headache and becomes more drowsy. What is happening and what do you do?
Read the worked answer
This is cerebral edema until proven otherwise, the leading cause of death in pediatric DKA, typically appearing 4-12 hours into treatment. Warning signs include headache, irritability or decreasing consciousness, inappropriate bradycardia, rising blood pressure, papilledema, pupillary changes, and focal or posturing movements. The earliest sign is often a subtle behavioral change wrongly attributed to fatigue, which is why serial neurologic checks with documentation matter.
Act immediately without waiting for imaging: give 3% saline at 2.5-5 mL/kg over 10-15 minutes (or mannitol 0.5-1 g/kg over 10-15 minutes), elevate the head of the bed, reduce the fluid infusion rate, avoid hypotonic fluids, and correct any hypoglycemia. Do not perform a lumbar puncture. Reassess every 15 minutes and escalate to intubation and neurosurgical consultation if consciousness continues to deteriorate.
Prevention is what was done earlier: no insulin bolus, insulin started after fluids, gradual rehydration over 24-48 hours, no bicarbonate, and close attention to corrected sodium and effective osmolality. Explain to the family what has happened and that the next 24 hours require intensive monitoring.