Vomiting and abdominal pain in a 9-year-old with new diabetes
Zainab is a 9-year-old girl brought to the emergency department with 3 days of vomiting and abdominal pain. She has lost 4 kg over 6 weeks and has had polyuria and nocturia. She is drowsy but rousable, with deep sighing respirations, dry mucous membranes, and capillary refill of 3 seconds. Weight is 24 kg. Bedside glucose is 29 mmol/L; venous blood gas shows pH 7.12, pCO2 22 mmHg, and bicarbonate 8 mmol/L. Sodium is 130 mmol/L, potassium 5.6 mmol/L, chloride 98 mmol/L, urea 9 mmol/L, and creatinine 70 micromol/L. Blood ketones are 5.2 mmol/L and HbA1c is 12%. Urine ketones are large and urine glucose is 4+. She has no previous diagnosis of diabetes and no family history, and she has not been febrile.
1. Classify the diabetic ketoacidosis and explain the sodium and potassium results. Calculate the corrected sodium and effective osmolality.
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Classification. pH 7.12 and bicarbonate 8 mmol/L with large ketones indicate diabetic ketoacidosis. By pH this is moderate DKA (pH below 7.2 but above 7.1); many protocols classify a bicarbonate below 10 mmol/L as severe, so treat it as at least moderate-to-severe and monitor closely.
Sodium. The measured sodium of 130 mmol/L is falsely low because hyperglycemia draws water into the extracellular space. Corrected sodium = 130 + 1.6 x (29 - 5.5)/5.5 = about 137 mmol/L. Effective osmolality = 2 x 130 + 29 = 289 mOsm/kg. The corrected sodium is normal, not low. A corrected sodium that falls during treatment is a warning sign.
Potassium. 5.6 mmol/L looks high, but total body potassium is depleted by vomiting, osmotic diuresis, and insulin deficiency. Insulin will drive potassium into cells and can cause life-threatening hypokalemia. Check potassium hourly and start replacement once it is below 5.5 mmol/L and urine output is present.
2. Write the first four hours of management, including fluid volumes, insulin, potassium, and monitoring. What would you not do?
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First four hours.
- Fluids: if shock is present, give 10-20 mL/kg of 0.9% saline. This child has dry mucous membranes and delayed capillary refill but is rousable, so give 10 mL/kg over 30-60 minutes and reassess. Then replace the deficit over 48 hours with 0.9% saline plus potassium chloride 40 mmol/L once potassium is below 5.5. Avoid hypotonic fluids.
- Insulin: start a continuous infusion of regular insulin at 0.05-0.1 U/kg/hour, one hour after fluids have started. Do not give a bolus.
- Potassium: hold until potassium is below 5.5 mmol/L and urine output is established, then add 40 mmol/L to the fluids; recheck hourly.
- Glucose: monitor hourly; when glucose falls below 14-17 mmol/L, add 5% dextrose to the fluids and continue insulin to close the ketone gap. Aim for a fall of about 5 mmol/L/hour.
- Monitoring: hourly vital signs, neurological checks, and glucose; electrolytes and blood gas at 2 and 4 hours; strict fluid balance.
- Precipitant: look for infection and take cultures if febrile.
Do not: give bicarbonate unless pH is below 6.9 with shock, give an insulin bolus, use rapid fluid boluses, use hypotonic saline, or start potassium while potassium is above 5.5 with no urine output.
3. Which features would make you suspect cerebral edema, and how would you manage it?
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Suspect cerebral edema if there is headache, irritability or drowsiness, vomiting, hypertension with bradycardia, papilledema, seizures, or a falling Glasgow Coma Scale. In this child, the initial drowsiness is a baseline; any worsening is significant.
Risk factors: new-onset diabetes, younger age, severe acidosis, high urea, rapid fluid administration, and bicarbonate use. This child has several.
Management. Raise the head of the bed, reduce the fluid rate by one-third, and check glucose and sodium. Give mannitol 0.5-1 g/kg IV over 10-15 minutes, or 3% saline 2.5-5 mL/kg if mannitol is unavailable. Call for urgent neuroimaging once stable, and involve pediatric critical care. Do not delay treatment for imaging. Reassess neurological status frequently; if there is no response, repeat mannitol or discuss neurosurgery.