Situation: A nurse on the pediatric ward cares for school-age children and adolescents with type 1 diabetes. Six hours into treatment for diabetic ketoacidosis, a 9-year-old who had been alert and talking complains of headache and vomits again. The nurse compares findings: Heart rate: 118/min → 70/min Blood pressure: 100/62 mmHg → 128/70 mmHg Glasgow Coma Scale score: 15 → 12 Blood glucose: 390 mg/dL (21.7 mmol/L) → 250 mg/dL (13.9 mmol/L) What is the MOST likely cause?

Headache, renewed vomiting, a falling level of consciousness, a falling heart rate, and rising blood pressure after initial improvement are warning signs of cerebral edema, which occurs most often 4–12 hours after DKA treatment starts. The nurse raises the head of the bed, notifies the physician at once, and prepares mannitol or hypertonic saline.

Clinical situation
A 9-year-old in treatment for diabetic ketoacidosis initially improved, then developed headache, vomiting, and a falling Glasgow Coma Scale score. The vital signs changed in a specific pattern: heart rate dropped from 118/min to 70/min, blood pressure rose from 100/62 mmHg to 128/70 mmHg, and GCS fell from 15 to 12. Blood glucose improved from 390 mg/dL to 250 mg/dL, so the problem is not persistent severe hyperglycemia.

Why the answer is cerebral edema
The combination of headache, recurrent vomiting, declining consciousness, bradycardia, and rising blood pressure after initial improvement is the classic warning pattern for cerebral edema during DKA treatment. This complication most often appears 4–12 hours after therapy begins, which matches the “six hours into treatment” timing in this case. The falling heart rate with rising blood pressure reflects increasing intracranial pressure and a Cushing response, not a simple fluid or electrolyte problem.

Pathophysiology in simple terms
Cerebral edema in DKA is accumulation of water in the brain. Two forms are described: vasogenic edema, where the blood–brain barrier breaks down and fluid leaks into the interstitial space, and cellular edema, where astrocytes swell while the barrier stays intact ^[2]. The exact mechanism remains unclear, but the clinical picture is what matters at the bedside. The brain swelling raises intracranial pressure, which compresses the brainstem and produces headache, vomiting, altered mental status, and the vital-sign changes seen here.

How common and how serious is it
Cerebral edema is the most frequent serious complication of pediatric DKA ^[1]. Reported prevalence varies: older data describe 1%–5% of DKA episodes ^[1], while a recent systematic review reports it as relatively uncommon at under 1%, with death in about 0.1%–0.3% of cases ^[3]. However, among survivors, 25% have permanent neurologic deficits ^[3]. This means the nurse must recognize early warning signs immediately, because outcomes depend on prompt intervention.

Why the other options do not fit

Option	Why it is less likely
1. Hypoglycemia	Blood glucose is 250 mg/dL, still elevated, not low. Hypoglycemia would typically cause tachycardia, diaphoresis, and tremors, not bradycardia with rising blood pressure.
2. Worsening acidosis	Glucose is improving, and worsening acidosis alone would more likely cause Kussmaul breathing and tachycardia, not the falling heart rate and rising blood pressure seen here.
4. Hypokalemia	Potassium shifts into cells during insulin therapy and can cause weakness or arrhythmias, but it does not explain the headache, vomiting, and declining GCS with this vital-sign pattern.

Nursing priority and action
Watch out! The earliest clues are often subtle: a new headache, a single episode of vomiting, or a small drop in GCS. Do not wait for full-blown coma. Key point! When cerebral edema is suspected, the nurse raises the head of the bed, notifies the physician immediately, and prepares mannitol or hypertonic saline as ordered. Frequent neurologic checks and vital-sign monitoring are essential during the first 4–12 hours of DKA treatment because that is the highest-risk window ^[1][3].

Connecting the evidence to the bedside
The systematic review notes that clinical presentation can be nonspecific, but hyperglycemia and ketosis are present in almost all cases ^[3]. That is why the nurse must rely on neurologic and hemodynamic trends rather than waiting for a single dramatic finding. The rising blood pressure with falling heart rate in this child is a late and dangerous sign of rising intracranial pressure. Recognizing this pattern early and acting on it is the single most important nursing intervention for preventing death or permanent brain injury in pediatric DKA.