Cerebral blood flow velocity changes under nitrous oxide halothane anesthesia in patients with frontotemporal gliomas: a comparison of the normal and abnormal cerebral hemispheres.

BACKGROUND: Regional differences in vascular response to anesthetic agents in brain areas with and without tumors have not been investigated till now. The existence of such differences may influence the regional distribution of cerebral blood flow under anesthesia. MATERIAL AND METHODS: In 8 patients with frontotemporal gliomas, middle cerebral artery blood flow velocity (VMCA), pulsatality index (PI) and resistance index (RI) were determined in the normal and pathological cerebral hemispheres before and after stable nitrous oxide-halothane anesthesia. RESULTS: During halothane anesthesia, there was an increase in VMCA both in the normal cerebral hemisphere (69 +/- 11 to 100 +/- 38 cm/s; P = 0.05) and the hemisphere with tumor (65 +/- 17 to 83 +/- 28 cm/s; P = 0.04). A significant decrease in the pulsatality index and the resistance index was also observed in both the hemispheres (P < 0.05). The percentage changes of VMCA, PI and RI in both the hemispheres after anesthesia were not significantly different. CONCLUSIONS: In patients with cerebral tumors, nitrous oxide-halothane anesthesia causes comparable changes of cerebral blood flow velocities in the hemisphere with tumor and the normal hemisphere.

Safety of acute normovolemic haemodilution with hydroxyethyl starch during intracranial surgery.

The effect of acute normovolemic haemodilution on haemodynamics, serum osmolality and coagulation parameters was studied in 20 patients undergoing intracranial surgical procedures. After induction of anaesthesia, 740+/-153 ml of blood was collected and the same was replaced with an equal volume of 6% hexaethyl starch. Heart rate (HR), blood pressure (BP), central venous pressure (CVP) and end tidal carbon dioxide tension (Et CO2) were monitored for 45 min. Haemoglobin concentration (Hb), haematocrit (Hct), serum osmolality (Osm), bleeding time (BT), prothrombin time (PT) and platelet count were determined before and 45 min after haemodilution. Hb and Hct were significantly lower following haemodilution (13.1+/-1.8 and 10.3+/-1.7 g/dL for Hb and 38.0+/-4.6%. and 30.1+/-4.5% for Hct). There was no significant change in the HR, BP and Et CO2 throughout the study period. CVP increased marginally from 35 to 45 min but was within normal limits. There was no significant change in serum osmolality, bleeding time and prothrombin time following haemodilution. Platelet count decreased following haemodilution but the values were within normal limits. The brain relaxation, as assessed by a semiquantitative scale, was satisfactory in all cases. None of the patients developed intraoperative brain swelling. In conclusion, acute normovolemic haemodilution with hexaethyl starch is tolerated well haemodynamically. It does not cause changes in serum osmolality which can increase brain oedema. It has no adverse effect on intraoperative haemostasis. It is a safe technique to decrease homologous blood transfusion during intracranial surgery.