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Biomedical subjects

O Z Chi

Publications and source records attributed to O Z Chi.

43 records · Page 3Linked to original sources
PubMed1990

Effects of enflurane on visual evoked potentials in humans.

Effects of enflurane on visual evoked potentials (VEP) were studied in eight healthy female patients. Control VEP were recorded from the occipital electrode (OZ-CZ), and prominent negative (N70) and positive (P100) peaks were observed following flash light stimulation. After induction of anaesthesia with thiopentone, VEP were recorded at expired concentrations of 1.2, 1.8, 2.4 and 2.7% of enflurane in 100% oxygen. The amplitude of the P100 was decreased and the latency of the N70 was increased significantly from the control with all concentrations of enflurane. No significant difference was found between different concentrations of enflurane. The latency of the P100 was increased significantly only at concentrations above MAC and at 2.7% when it was significantly longer than those at 1.2 and 1.8%. We conclude that VEP are altered significantly with enflurane in clinically used concentrations.

Adult↗
PubMed1989

Visual evoked potentials during thiopentone-fentanyl-nitrous oxide anaesthesia in humans.

Visual evoked potentials (VEP) during thiopentone-fentanyl-nitrous oxide anaesthesia were studied in 15 healthy patients undergoing non-neurosurgical procedures. The VEP was recorded before and at 1 and 2 min after induction of anaesthesia with 5-6 mg.kg-1 of thiopentone. After recording the 1 and 2 min VEPs, anaesthesia was maintained with a fentanyl-nitrous oxide-oxygen combination, and further recordings were made at 5, 10, 15 and 20 min after induction. The 1 and 2 min VEPs showed a marked decrease in the amplitudes. Latencies were increased. The amplitudes gradually returned to the control level at 15 min, while the latencies remained increased throughout the study period. In conclusion, thiopentone should be avoided during the critical period of VEP recording. Once it is given, at least 15 min should elapse before an appropriate interpretation of the VEP can be made. Thiopentone-fentanyl-nitrous oxide anaesthesia slightly increases the latencies of the VEP. These effects should be considered in the interpretation of the VEP when thiopentone-fentanyl-nitrous oxide anaesthesia is used.

Adult↗
PubMedDate not supplied

Effects of magnesium sulfate and nifedipine on regional cerebral blood flow during middle cerebral artery ligation in the rat.

The effects of magnesium sulfate and nifedipine on regional cerebral blood flow were compared after ligation of the middle cerebral artery in rats. Twenty-one rats were divided into 3 groups of 7 each. The groups were the magnesium group, the nifedipine group, and the control group. Animals were anesthetized with pentobarbital. The middle cerebral artery was ligated, and magnesium sulfate was infused at a rate of 16 mg/kg/min for 30 min in the magnesium group, and nifedipine was infused at a rate of 10 micrograms/kg/min for 45 min in the nifedipine group. Using [14C]-iodoantipyrine, regional cerebral blood flow was measured 1 hr after middle cerebral artery ligation in the ischemic cortex, contralateral cortex, thalamus, hypothalamus, pons, medulla and cerebellum. In the control group, the mean cerebral blood flow was 30.7 +/- 12.2 ml/min/100 g in the middle cerebral artery-ligated cortex, and 75.9 +/- 10.5 ml/min/100 g in the contralateral cortex. Nifedipine did not significantly alter the cerebral blood flow in any of the brain regions studied. However, in the magnesium group, the regional cerebral blood flow in the middle cerebral artery-ligated cortex was significantly higher (64.2 +/- 8.8 ml/min/100 g) than that recorded in the control and nifedipine groups, whereas the regional cerebral blood flow in the contralateral cortex was not significantly different from other groups. Our data showed that magnesium was effective and superior to nifedipine in improving blood flow in the ischemic area of the brain.

Animals↗
PubMedDate not supplied

Effects of hemorrhage on regional cerebral blood flow in awake and in isoflurane-anesthetized rats.

During hemorrhage, redistribution of cerebral blood flow may occur. We compared the effects of hemorrhage on regional cerebral blood flow in awake rats and in rats anesthetized with 1% or 2% isoflurane. In half of each group, regional cerebral blood flow was measured without hemorrhage. The other half was slowly bled to a mean arterial blood pressure of 40-45 mm Hg before measuring the regional cerebral blood flow. Without hemorrhage, the cortical regional blood flow was greater in the awake animals than that of the caudal part of the brain. In the 2% isoflurane group, however, the regional cerebral blood flow of the caudal part was greater than the cortical regional cerebral blood flow. After hemorrhage, a similar decrease (-45%) of the regional cerebral blood flow was observed in each brain region and the pattern of distribution of it remained unchanged in all experimental groups. However, the absolute value of the cortical flow was higher in the awake animals than in the isoflurane groups. Our experiment demonstrated that hemorrhage decreased the regional cerebral blood flow. However, it did not alter the redistribution of the cerebral blood flow in awake animals nor in the animals anesthetized with isoflurane.

Anesthesia↗