Articles: general-anesthesia.
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During carotid endarterectomy (CEA), phenylephrine infusions are commonly used to induce hypertension during carotid clamping in an attempt to increase collateral cerebral blood flow and prevent cerebral ischemia. Although this practice appears to increase the incidence of intraoperative myocardial ischemia during CEA when general anesthesia is employed, whether the limited use of phenylephrine infusions in specific instances of cerebral ischemia, as shown on an electro-encephalogram, results in low perioperative rates of both myocardial infarction (MI) and cerebral infarction remains unclear. We studied 171 CEAs done under general anesthesia performed with selective shunting based on the identification of cerebral ischemia by a two-channel computerized electroencephalographic monitor. ⋯ Two non-Q wave MIs (1.2%) occurred, both nonfatal. There were two cerebral infarctions (1.2%) and three deaths not related to MI (1.8%). Based on these findings, in order to decrease the incidence of both MI and cerebral infarction after general anesthesia for CEA, we recommend the restrictive use of phenylephrine-induced hypertension for specific instances of slowly or poorly reversible cerebral ischemia, as shown on the electroencephalogram.
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We studied the protective effect of prostaglandin E1 (PGE1)-induced hypotensive anesthesia on gastric mucosa in 30 elective surgical patients. Three groups, each composed of 10 patients, received PGE1, nitroglycerin or none during general anesthesia. ⋯ In the PGE1 group the viscosity and pH increased significantly and rapidly (P less than 0.05) as compared with the other groups. This suggests that PGE1 offers prophylactic effect against postoperative acute gastric mucosal lesion (AGML).
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Comparative Study
Somatosensory and auditory evoked responses recorded simultaneously: differential effects of nitrous oxide and isoflurane.
Auditory (AER) and somatosensory evoked responses (SSER) were recorded simultaneously in eight patients under anaesthesia before surgery. We studied the effects of equi-MAC end-expiratory concentrations of isoflurane (0.65-0.75%) and nitrous oxide (60-65%). The anaesthetics were changed at random in three consecutive 10-min periods so that each patient received both drugs. ⋯ We were unable to demonstrate significant differences in Pa and Nb amplitude between isoflurane and nitrous oxide that we had seen previously. However, the amplitude of the SSER wave N20 was reduced significantly by nitrous oxide compared with isoflurane (P = 0.0004). This wave (N20) is thought to emanate from the thalamo-cortical radiations, and our findings may be explained by an analgesic effect of nitrous oxide mediated by endogenous opioids.
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It has recently been reported that the use of halogenated agents during balanced general anesthesia may result in an increase in blood loss associated with cesarean section. This report has been criticized for failure to control for a variety of other factors that may have contributed to the increased blood loss, particularly the indication for and type of cesarean section. The present study was designed in an attempt to resolve this criticism. ⋯ A greater proportion of women undergoing general anesthesia experienced a postoperative decrease in hematocrit of 5 vol% or more compared with patients receiving regional anesthesia (10 of 42 versus 5 of 75, p = 0.018). Thus, we conclude that women undergoing uncomplicated elective repeat cesarean section under general anesthesia supplemented with a halogenated agent are at risk for increased blood loss compared with those women receiving regional anesthesia. However, the increased blood loss was not clinically significant in this study, since none of the patients required transfusion.