DOI: 10.1097/00000539-200211000-00070
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Issn Print: 0003-2999
Publication Date: 2002/11/01
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Excerpt
We appreciate the comments by Schaffranietz and colleagues and agree that moderately hyperventilated neurosurgical patients (PaCO2 28–32 mm Hg) receiving propofol (and to a lesser extent inhalational agents, too) can present low SjO2 values (1,2). However, although Schaffranietz et al. did not find SjO2 values compatible with brain hypoperfusion in normoventilated neurosurgical patients receiving propofol either with or without nitrous oxide (3,4), preliminary results of recent studies show that this happens. Indeed, in patients with brain tumors under normoventilation, De Keersmaeker et al. found a higher incidence of jugular bulb desaturation with propofol/nitrous oxide compared with sevoflurane/nitrous oxide (5) and De Deyne et al. also found episodes of low SjO2 values with propofol (6). Moreover, while at PaCO2 of 28–29 mm Hg, we found that mean SjO2 was not affected by the addition of 67% nitrous oxide during propofol anesthesia (SjO2 of 52% and 50% with and without N2O, respectively); mean SjO2 increased from 56% to 66% with N2O in patients receiving sevoflurane (2). In contrast, under normoventilation, the addition of 65% nitrous oxide increased mean SjO2 during both propofol (from 49.5% to 57.5%) and sevoflurane (from 57.6% to 67.2%) anesthesia (6). This increase points out the difficulties in making predictions on the final effect of nitrous oxide, which is highly variable and clearly determined by the basal condition of the patients, mainly including the type of anesthesia and the arterial blood pressure of CO2.
