Jugular bulb oxygen saturation during propofol and isoflurane/nitrous oxide anesthesia in patients undergoing brain tumor surgery

We investigated, in brain tumor patients, the jugular bulb venous oxygen partial pressure (Pjo(2))and hemoglobin saturation (Sjo(2)), the arterial to jugular bulb venous oxygen content difference (AJDo(2)), and middle cerebral artery blood flow velocity (Vmca) during anesthesia, and the effect of hyperventilation on these variables. Twenty patients were randomized to receive either isoflurane/ nitrous oxide/fentanyl (Group 1) or propofol/fentanyl (Group 2). At normoventilation (Paco(2) 35 +/- 2 mm Hg in Group 1 and 33 +/- 3 mm Hg in Group 2), Sjo(2) and Pjo(2) were significantly higher in Group 1 than in Group 2 (Sjo(2) 60% +/- 6% and 49% +/- 13%, respectively; P = 0.019) (Pjo(2) 32 +/- 3 and 27 +/- 5 mm Hg, respectively; P = 0.027). In Group 2, 5 of 10 patients had Sjo, <50%, and 3 of these patients had Sjo, <40% and AJDo(2) >9 mL/dL. All patients in Group 1 had Sjo(2) >50%. During hyperventilation, there were no differences in Sjo(2), Pjo(2), or AJDo(2) between the two groups. On hyperventilation, there was no correlation between the relative decreases of Vmca and 1/AJDo(2) (r = 0.21, P = 0.41). The results indicate during propofol anesthesia, half of the brain tumor patients showed signs of cerebral hypoperfusion, but not during isoflurane/nitrous oxide anesthesia. Furthermore, during Pace, manipulations, shifts in Vmca are inadequate to evaluate brain oxygen delivery in these patients. Implications: During propofol anesthesia at normoventilation, 50% of brain tumor patients showed signs suggesting cerebral hypoperfusion, but this could not be demonstrated during isoflurane/nitrous oxide anesthesia. During Pace, manipulations, consecutive measurements of the cerebral blood flow velocity may be inadequate to assess cerebral oxygenation.