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Disturbed autoregulation and CO2 reactivity have been reported in patients with brain tumors. Therefore, we decided to monitor the cerebrovascular effects of anesthetic drugs and hyperventilation. Transcranial Doppler sonography (TCD) can measure noninvasively alterations of flow velocities (v) and cross-sectional vessel area (VA) in large brain arteries. Twenty-eight patients with large malignant brain tumors in the territory of the middle cerebral artery (MCA) randomly received propofol or thiopental for induction and maintenance of anesthesia. Mean arterial pressure (MAP), heart rate (HR), and TCD parameters (vMCA and VA of the tumor or nontumor side) were determined at six data points (DP). The first measurements (MAP, HR, and TCD of the nontumor side) were performed before (DP I) and 60 s after (DP II) induction of anesthesia with either 2 mg/kg propofol or 4 mg/kg thiopental. After intubation and normoventilation (50% O2 in air), 0.05-0.1 mg/kg midazolam and an alfentanil infusion (100 μg/kg × h) were initiated. Then MAP, HR, vMCA, and VA of the tumor side were analyzed before (DP III) and 60 s after (DP IV) either propofol (1 mg/kg) or thiopental (2 mg/kg) were given. Finally, the effects of hyperventilation on HR, MAP, vMCA, and VA (tumor side) were determined (DP V and VI). Mean ± SD, thiopental or propofol reactivity (nontumor and tumor side) and CO2 reactivity (tumor side) were calculated; statistical comparison between DP I and II, III and IV, and V and VI was performed by paired t tests (p < 0.05). Unpaired t tests were used to evaluate differences between groups. By injection of propofol or thiopental, MAP was reduced, whereas VA was not markedly influenced. vMCA decreased by 24% after propofol and by 27% after thiopental administration on the nontumor side. On the tumor side, reduced or even paradoxical effects of propofol, thiopental, and hyperventilation on vMCA occurred frequently. Nine patients developed intraoperative brain swelling; five of these had the lowest drug reactivity (tumor side) of their group. TCD can demonstrate disturbed vasoreactivity caused by large brain tumors: Further studies are necessary to define the role of TCD in neuroanesthesia.
Schregel et al. (Thu,) studied this question.