Cerebral hyperemia and impaired cerebral autoregulation associated with diabetic ketoacidosis in critically ill children.

OBJECTIVE: Cerebral edema associated with diabetic ketoacidosis is an uncommon but severe complication of insulin-dependent diabetes mellitus with unclear pathophysiology. We sought to determine whether cerebral edema in patients with diabetic ketoacidosis was related to changes in cerebral blood flow, autoregulation, regional cerebral saturation, or S100B.
DESIGN: Prospective case series.
SETTING: Pediatric intensive care unit of a tertiary children's hospital. PATIENTS: Six patients with diabetic ketoacidosis and altered mental status, requiring computed tomographic scan of the head.
INTERVENTIONS: Study evaluations included: 1) transcranial Doppler evaluations to determine middle cerebral artery flow velocities and cerebral autoregulation, defined by the autoregulatory index, at 6 and 36 hrs; 2) continuous monitoring of regional cerebral oxygenation on the left lateral forehead using near-infrared spectroscopy for the first 24 hrs of admission; 3) serial measurement of S100B as a marker of central nervous system injury; and 4) follow-up head computed tomographic scan.
RESULTS: Serial computed tomographic scans showed that four of six patients had changes in brain volume without overt cerebral edema. Initial scans showed narrowing of the third and lateral ventricles when compared with follow-up. There was no difference in middle cerebral artery flow velocities between admission and recovery at 36 hrs, despite Paco2 increasing during treatment. Cerebral flow was normal to increased, despite hypocapnia. Cerebral autoregulation was impaired in five of six patients at 6 hrs and normalized by 36 hrs. Mean regional cerebral oxygenation was measured in five of six patients and decreased linearly with time. Two patients showed maximal regional cerebral oxygenation before returning to baseline. There were no periods of low regional cerebral oxygenation in any patient at any time. No elevation in S100B was found.
CONCLUSIONS: We found normal to increased cerebral blood flow, elevated regional cerebral oxygenation, impaired autoregulation, and changes in brain volume in clinically ill pediatric patients with diabetic ketoacidosis. We found no evidence of cerebral ischemia. These findings suggest that the pathophysiology of cerebral edema in diabetic ketoacidosis may involve a transient loss of cerebral autoregulation, allowing a paradoxic increase in cerebral blood flow and the development of vasogenic cerebral edema.