The effect of hyperventilation and hyperoxia on cerebral venous oxygen saturation in patients with traumatic brain injury.

UNLABELLED

Eighteen head-injured patients undergoing hyperventilation were studied for changes in jugular venous oxygen saturation (SjvO2) and arteriovenous oxygen content difference (AVDO2) in response to changes in PaO2 and PaCO2. SjvO2 decreased significantly from 66% +/- 3% to 56% +/- 3% (mean +/- SD) when PaCO2 decreased from 30 to 25 mm Hg at a PaO2 of 100-150 mm Hg. SjvO2 values returned to baseline (66% +/- 2%) when PaCO2 was restored to 30 mm Hg. Repetition of the study at a PaO2 of 200-250 mm Hg produced a similar pattern. However, SjvO2 values were significantly greater with PaO2 within the range of 200-250 mm Hg (77% +/- 4% and 64% +/- 3%) than SjvO2 measured at a PaO2 of 100-150 mm Hg at PaCO2 values of both 30 and 25 mm Hg. AVDO2 also improved with a PaO2 of 200-250 mm Hg at each PaCO2 (P < 0.001). In conclusion, decreases in SjvO2 associated with decreases in PaCO2 may be offset by increasing PaO2.

IMPLICATIONS

The adequacy of cerebral oxygenation can be estimated in head-injured patients by monitoring jugular bulb oxygen saturation and the arteriovenous oxygenation content difference. Increasing the partial pressure of arterial oxygen above normal offset deleterious effects of hyperventilation on jugular bulb oxygen saturation and arteriovenous oxygenation content difference in head-injured patients.