SJVO(2) MONITORING IN HEAD-INJURED PATIENTS

Jugular venous oxygen saturation (SjvO(2)) measures the balance betwee n cerebral oxygen delivery and cerebral oxygen consumption. Abnormalit ies that increase oxygen consumption (e.g., fever or seizures) or that decrease oxygen delivery (e.g., increased ICP, hypotension, hypoxia, hypocapnia, or anemia) can decrease SjvO(2). Measuring SjvO(2) continu ously in the ICU in 177 patients with severe head injury, jugular veno us desaturation (SjvO(2) < 50%) was identified at least once in 39% of the patients. Approximately half of the episodes of desaturation were due to intracranial hypertension and half were due to systemic causes . The occurrence of one or more episodes of desaturation was strongly associated with a poor outcome, suggesting that the reduction in oxyge n delivery identified with the SjvO(2) monitoring contributed to the n eurological injury. In the operating room, jugular venous desaturation was identified in 6 of 8 patients who were monitored during emergency evacuation of a traumatic intracranial hematoma. The lowest SjvO(2) o bserved was 28%. In all 8 cases, the SjvO(2) increased, from 47 +/- 10 % to 63 +/- 5% after evacuation of the hematoma. Additional data suppo rting the hypothesis that these secondary insults identified with the SjvO(2) monitoring contribute to the patient's neurological injury com e from measurement of the extracellular concentrations of lactate and excitatory amino acids in the brain using microdialysis. Lactate conce ntration increased from 0.9 +/- 0.3 to 2.4 +/- 0.5 mu mol/L and glutam ate increased from 11.5 +/- 8.5 to 55.0 +/- 10.4 mu mol/L during 8 epi sodes of jugular venous desaturation in 7 of 22 patients monitored wit h microdialysis. SjvO(2) identifies global reductions in cerebral oxyg enation due to a variety of causes, and is useful as a monitor for sec ondary insults in patients with severe head injury.