TRANSCRANIAL DOPPLER MONITORING DURING INDUCTION OF ANESTHESIA - EFFECTS OF PROPOFOL, THIOPENTAL, AND HYPERVENTILATION IN PATIENTS WITH LARGE MALIGNANT BRAIN-TUMORS

Disturbed autoregulation and CO, reactivity have been reported in pati ents with brain tumors. Therefore, we decided to monitor the cerebrova scular 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 ar teries. Twenty-eight patients with large malignant brain tumors in the territory of the middle cerebral artery (MCA) randomly received propo fol or thiopental for induction and maintenance of anesthesia. Mean ar terial pressure (MAP), heart rate (HR), and TCD parameters (vMCA and V A of the tumor or nontumor side) were determined at six data points (D P). The first measurements (MAP, HR, and TCD of the nontumor side) wer e performed before (DP I) and 60 s after (DP II) induction of anesthes ia with either 2 mg/kg propofol or 4 mg/kg thiopental. After intubatio n and normoventilation (50% O2 in air), 0.05-0.1 mg/kg midazolam and a n alfentanil infusion (100 mug/kg x h) were initiated. Then MAP, HR, v MCA, and VA of the tumor side were analyzed before (DP III) and 60 s a fter (DP IV) either propofol (I mg/kg) or thiopental (2 mg/kg) were gi ven. Finally, the effects of hyperventilation on HR, MAP, vMCA, and VA (tumor side) were determined (DP V and VI). Mean +/- SD, thiopental o r propofol reactivity (nontumor and tumor side) and CO2 reactivity (tu mor 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 n ot markedly influenced. vMCA decreased by 24% after propofol and by 27 % after thiopental administration on the nontumor side. On the tumor s ide, 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 react ivity (tumor side) of their group. TCD can demonstrate disturbed vasor eactivity caused by large brain tumors: Further studies are necessary to define the role of TCD in neuroanesthesia.