Cerebral oxygenation during warming after cardiopulmonary bypass

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Abstract
To evaluate jugular venous oxygen saturation (SjvO2), measured with a fiberoptic oximetry catheter, and brain tissue oxygen saturation, measured by near-infrared spectroscopy (NIRSO2), as monitors of cerebral oxygenation during cardiopulmonary bypass surgery. Prospective, clinical study. Operating room of a Veterans Administration Hospital. Nineteen patients undergoing moderate hypothermic cardiopulmonary bypass surgery. SjvO2 and NIRSO2 were monitored in the patients during the surgical procedure. Moderate hypothermic cardiopulmonary bypass surgery had two distinct cerebral hemodynamic phases. While the patients were hypothermic, SjvO2 averaged 80 +/- 7% and none of the patients had an increase in cerebral lactate production. During the rewarming period, however, reductions in SjvO2 to <50% occurred in 16 (84%) patients and increased cerebral anaerobic metabolism developed in 11 (58%) patients. SjvO2 during rewarming was dependent on mean arterial pressure, with 60 mm Hg appearing to be a critical value. Two other factors appeared to also contribute to the jugular desaturation, a low hematocrit and a rapid warming time. The SjvO sub 2 catheter had excellent performance during the surgery. The average difference between paired measurements of SjvO2 by the catheter and in blood samples was -0.4 +/- 4.25%, and the correlation between the two measurements was highly significant (r2 = .93; p < .001). The NIRSO2 trended with the SjvO sub 2 in most patients (r2 = .63; p < .001). The study confirms other studies showing that jugular venous desaturation can occur during rewarming after cardiopulmonary bypass surgery. Presently, SjvO sub 2 appears to be a better monitor of cerebral oxygenation than NIRSO2. However, NIRSO2 has promise as a noninvasive monitor of cerebral oxygenation if future developments allow more quantitative measurements of oxygen saturation. (Crit Care Med 1997; 25:1655-1662)