What is the most likely cause of a child's condition presenting with hyperglycemia, metabolic acidosis, ketosis, and hypotension?

Diabetic Ketoacidosis (DKA)

The most likely diagnosis is Diabetic Ketoacidosis (DKA), which represents an acute, life-threatening complication of absolute insulin deficiency characterized by the triad of hyperglycemia, metabolic acidosis (low bicarbonate), and ketosis—manifesting clinically with the fruity breath odor (acetone), vomiting, lethargy, and hypotension described in this case. 1, 2

Clinical Presentation Supporting DKA

This 11-year-old presents with the classic biochemical and clinical features of DKA:

• Hyperglycemia: Blood glucose of 8.9 mmol/L (160 mg/dL), though this is relatively modest and consistent with the fact that approximately 10% of DKA cases present with euglycemic DKA (glucose <11.1 mmol/L or 200 mg/dL) 3
• Metabolic acidosis: Low bicarbonate indicates the acidotic state that defines DKA 1, 2
• Ketosis: The fruity (nail polish-like) breath odor is pathognomonic for acetone/ketones, a hallmark of DKA 4
• Hyponatremia: Serum sodium of 132 mmol/L is an expected consequence of osmotic shifts due to hyperglycemia and volume depletion from vomiting and osmotic diuresis 2
• Dehydration and hypotension: Result from osmotic diuresis and fluid losses from vomiting 3
• Altered mental status: Lethargy and drowsiness are common neurological manifestations of DKA 1, 5

Why Not the Other Options

Uncontrolled Hyperglycemia (Option B) is too vague and doesn't explain the metabolic acidosis, ketosis, or acute decompensation. While hyperglycemia is present, it's the ketoacidosis that makes this life-threatening 1.

Hyponatremia (Option C) is a consequence of DKA, not the primary diagnosis. The hyponatremia results from osmotic shifts and volume depletion, not a primary sodium disorder 2.

Hyperosmolar Hyperglycemic State (Option D) is extremely rare in children and typically occurs in type 2 diabetes with much higher glucose levels (often >33 mmol/L or 600 mg/dL), absence of significant ketosis, and without the fruity breath odor 1, 6. This child's presentation with ketosis and fruity breath definitively rules out HHS.

Critical Diagnostic Considerations

• DKA severity classification: Based on the low bicarbonate and clinical presentation with altered mental status, this likely represents moderate to severe DKA (pH <7.2, bicarbonate <10 mmol/L) 1
• New-onset type 1 diabetes: DKA is the presenting feature in 30-40% of children with newly diagnosed type 1 diabetes, particularly in younger children 1, 7
• Age-related risk: Children under 5 years have the highest risk of presenting with DKA at diagnosis, though this 11-year-old's presentation with a 2-day prodrome of vomiting/diarrhea and decreased intake is classic 8, 7

Immediate Management Priorities

This child requires immediate hospitalization with intensive monitoring for life-threatening complications, particularly cerebral edema which occurs in 0.7-1.0% of pediatric DKA cases and carries 24-70% mortality when symptomatic 5, 3:

• Fluid resuscitation: Initiate IV fluids cautiously, ensuring gradual correction of osmolality (maximal reduction not exceeding 3 mOsm/kg/hour) to prevent cerebral edema 5
• Insulin therapy: Start continuous IV insulin infusion at 0.1 units/kg/hour, but consider delaying 1-2 hours after starting fluids to avoid precipitous osmolality changes 2, 5
• Electrolyte monitoring: Monitor potassium closely and replace as soon as urine output is established, as insulin drives potassium intracellularly and can cause life-threatening hypokalemia 2, 4
• Neurological monitoring: Hourly neurological checks are essential—any worsening mental status demands immediate intervention with mannitol or hypertonic saline 5
• Laboratory monitoring: Check electrolytes, blood glucose, and blood gases every 2-4 hours; hourly capillary glucose 2, 9

Critical Pitfall to Avoid

Never attribute worsening altered mental status solely to the DKA itself—this is early cerebral edema until proven otherwise and requires immediate treatment with mannitol (0.5-1 g/kg IV) or hypertonic saline (3% NaCl 2.5-5 mL/kg over 10-15 minutes) plus consideration for intubation 5. The earliest warning signs are increasing sleepiness and irritability, occurring before ominous signs like seizures, bradycardia, or respiratory arrest 5.