We read with great interest Jansen et al.’s article (1), which compared the effects on the jugular bulb saturation (Sjo2) of two different kinds of anesthesia (propofol versus isoflurane/nitrous oxide), under normoventilation and hyperventilation, in patients undergoing brain tumor surgery. The authors pointed out that, within the group of patients under normoventilation conditions who were anesthetized with propofol, 50% of the patients presented with Sjo2 <50%, something which did not happen in patients who were anesthetized with isoflurane/nitrous oxide.
In this regard, we must observe that, recently, Schaffranietz et al. (2) published an article about patients who also underwent elective brain tumor surgery, who were anesthetized with propofol, and in which they tried to investigate the effect of different ventilation regimens on Sjo2 and on other parameters of cerebral metabolism and oxygenation. In that article, they observed that Paco2 of 31 mm Hg led to global cerebral hypoperfusion, and that the lower limit of normoventilation should be fixed at 32 mm Hg.
Taking such a remark into consideration, we do not think that the two groups under normoventilation in Jansen et al.’s article (1) can be superimposed (Paco2 of 33 ± 3 mm Hg in the group anesthetized with propofol versus Paco2 of 35 ± 2 mm Hg in the group anesthetized with isoflurane and nitrous oxide). It would be interesting to see how many patients in the group under normoventilation and anesthetized with propofol had Paco2 <32 mm Hg, and out of these, the number of patients who presented with low Sjo2. In Schaffranietz et al.’s article (2), patients of all different groups were anesthetized homogeneously, so before concluding that propofol can lead to global cerebral hypoperfusion, and to clarify the information given in Jansen et al.’s article (1), we should see if the Sjo2 in patients who were anesthetized with isoflurane/nitrous oxide with Paco2 of 31 mm Hg would remain within normal limits and more interestingly, which Sjo2 would have patients anesthetized with such a Paco2 and drugs without effects on cerebral blood flow.
Montserrat Olivé
MD Montserrat Noguer MD
References
1. Jansen GFA, van Praagh BH, Kedaria MB, Odoom JA. Jugular bulb oxygen saturation during propofol and isoflurane/nitrous oxide anesthesia in patients undergoing brain tumor surgery. Anesth Analg 1999; 89:358–63.
2. Schaffranietz L, Heinke W. The effect of different ventilation regimens on jugular venous oxygen saturation in elective neurosurgical patients. Neurol Res 1998; 20(Suppl 1):S66–70.
