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Query: UMLS:C0278134 (anesthesia)
 110,339 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The influence of halothane (0.6 and 2%) upon cerebral (cortical) blood flow (CBF) and cerebral metabolic rate for oxygen (CMRo2) was studied in artificially ventilated rats, using a modified technique of Kety & Schmidt (1948). The values obtained in halothane anaesthesia were compared to those recorded in nitrous oxide anaesthesia, or to those measured in unanesthetized animals given an analgesic drug (fentanyl citrate). Although it could be confirmed that halothane induces vasodilatation in the brain, there were relatively small differences in CBF between the groups. The results demonstrate that, in the rat, halothane depresses CMRo2 in a dose-dependent way. With 0.6% halothane, CMRo2 was reduced by 20-30% and, with 2% halothane, CMRo2 was reduced by about 50%. Thus, in the rat the effect of 2% halothane upon metabolic rate is comparable to that observed in barbiturate anaesthesia.
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PMID:The effect of halothane anaesthesia upon cerebral oxygen consumption in the rat. 0 48

The influence of an anaesthetic dose of chlormethiazole (Hemineurin) on blood flow (CBF) and oxygen consumption (CMRO2) in the rat brain was investigated. In spontaneously breathing animals a dose of 160 mg . kg-1 of chlormethiazole, infused i.v., induced a state close to surgical anaesthesia. In paralyzed animals, the same dose decreased CBF and CMRO2 to about 60% of control, an effect similar to that observed after an anaesthetic dose of phenobarbitone. Neither a protective nor a detrimental effect of chlormethiazole could be demonstrated when the drug was given during reversible and pronounced, incomplete ischaemia, as evaluated from the postischaemic tissue concentrations of labile phosphates (PCr, ATP, ADP, AMP) and of lactate and pyruvate. It is concluded that protection in this situation (as earlier shown with phenobarbitone) must, at least partly, be related to other mechanisms than a depression of metabolism.
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PMID:Influence of chlormethiazole on cerebral blood flow and oxygen consumption in the rat, and its effect on the recovery of cortical energy metabolism after pronounced, incomplete ischaemia. 3 16

The densities of cerebrospinal fluid and of local anesthetics, applicable to isobaric spinal anesthesia, were determined by using the Digital Density Meter DMA 02. The density of CSF showed little variation and at 37 degrees C was 1.00021 +/- 0.00024 g/cm3 (mean +/- SD, n = 22). The density of the local anesthetics bupivacaine 0.5%, carticaine 2%, lidocaine 2%, mepivacaine 2% and prilocaine 2% varied at 25 degrees C between 1.001 and 1.005 g/cm3, at 37 degrees C between 0.997 and 1.001 g/cm3. Tetracaine 0.5% in CBF increased its density by 0.00046 g/cm3. The addition of the vasoconstrictors adrenaline and ornipressine (POR 8) increased the density of the local anesthetic solutions insignificantly. On the basis of the narrow range of variation of CSF density, reliable statements may be made on the density dependent spread of local anesthetics in spinal anesthesia.
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PMID:[Density of cerebrospinal fluid and local anesthetics (author's transl)]. 52 47

The ethanol tissue sampling method for rCBF measurement was used to obtain information on the effects of cervical sympathetic stimulation in 8 cerebral structures in the non-anaesthetized rabbit. Sympathetic stimulation induced flow decreases of 12-29% according to structure, confirming the capability of this nerve to significantly reduce rCBF. Furthermore, a regional differentiation of cerebral structures into an 'anterior' group (mean decrease 22%) and a 'posterior' group (mean decrease 12%) with different reactivity to stimulation was established, thus confirming previous work in this laboratory with a local thermoclearance technique, and histochemical studies on sympathetic innervation to cerebral arteries and arterioles. These results provide strong evidence of the functional nature of the sympathetic nervous system in CBF regulation. The complementary nature of the ethanol technique (quantitative, multiregional measurement) and the local thermoclearance technique (continuous, semiquantitative measurements in 2-3 regions), and the absence of anaesthesia and significant trauma, means that combination of these two techniques offers considerable advantages in research on dynamic phenomena of the kind studied here.
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PMID:Quantitative multiregional blood flow measurements during cervical sympathetic stimulation. 87 23

Carotid endarterectomy requires temporary surgical occlusion of the involved carotid artery. During occlusion, the minimally acceptable (critical) internal carotid artery stump pressure is reported to be 50 torr, whereas for regional cerebral blood flow (rCBF), a critical range is reported to be 18-24 ml/100 g/min. During 90 carotid endarterectomies, rCBF and stump pressure were measured and the EEG continuously monitored. A positive correlation between rCBF and stump pressure (i.e., when both were either above or below their respective critical values) was observed in only 58 per cent of the cases. In 28 per cent stump pressures of less than 50 torr were observed despite rCBF's above 24 ml/100 g/min and normal EEG's. In 8 per cent stump pressures were more than 50 torr but rCBF's were less than 18 ml/100 g/min and EEG changes of ischemia were commonly observed. In the remaining 6 per cent rCBF's were marginal (18-24 ml/100 g/min) while stump pressures were more than 50 torr and EEG changes were not observed. The relationship between stump pressure and rCBF was influenced by the anesthetic. In the absence of transient ischemia during occlusion (that is, rCBF greater than 18 ml/100 g/min), halothane and enflurane anesthesia were associated with significantly higher rCBF's and lower stump pressures than was neuroleptanesthesia. Pre-occlusion and post-occlusion rCBF measurements also demonstrated cerebral vasodilation by halothane and enflurane (halothane greater than enflurane) and vasoconstriction by neuroleptanesthesia. It is concluded that stump pressure is an unreliable index of CBF during carotid occlusion and that its relationship to CBF is considerably influenced by the anesthetic.
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PMID:Internal carotid artery stump pressure and cerebral blood flow during carotid endarterectomy: modification by halothane, enflurane, and innovar. 97 90

The influence of phenobarbitone anesthesia on blood flow (CBF) and oxygen consumption (GMRO2) was evaluated in the rat brain, using a method that quantitatively measures CBF in mainly cortical areas. The data were compared to those obtained in animals under fentanyl citrate analgesia. Body temperature and arterial CO2 tension were maintained close to normal values in all groups. With 50 mg/kg of phenobarbitone, CBF and CMRO2 were reduced by about 20%. With 150 or 250 mg/kg, further reductions in CBF and CMRO2 were observed. At 250 mg/kg, CBF was reduced to one third, and CMRO2 to about 50% of normal. The results suggest that little further reduction in CBF or CMRO2 can be expected if the dose of phenobarbitone is increased above 250 mg/kg.
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PMID:The effect of phenobarbitone anaesthesia on blood flow and oxygen consumption in the rat brain. 106 78

The Kety-Schmidt washout technique has been modified to measure whole-brain blood flow and metabolism in the rat. During nitrous oxide anesthesia, 14 rats exhaled (133)Xe, and continuous and simultaneous arterial and cerebral venous samples were drawn from a femoral artery and the transverse sinus of the brain. Extracerebral contamination of the venous sample was minimal, and equilibration of (133)Xe in brain tissue and blood was obtained after 10-24 min of inhalation. Cerebral blood flow was calculated from the total activity of the mechanically integrated arterial and venous samples according to the principle of Scheinberg and Stead. At a mean Paco2 of 40 mmHg, CBF averaged 98 +/- 6 (SEM) ml/100 g-min and CMRO2 averaged 5.4 +/- 0.7 (SEM) ml/100 g-min. CBF changed 2.4% with each millimeter Hg change of Paco2 while CMRO2 changed only insignificantly. The values obtained for CBF are higher than reported for man and large laboratory animals bur reflect the proportionately greater amount of gray matter in the rat brain.
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PMID:Whole-brain blood flow and oxygen metabolism in the rat during nitrous oxide anesthesia. 114 36

A recent modification of the Kety-Schmidt wash-out technique for 133xenon was used to measure whole-brain blood flow (CBF) and oxygen consumption (CMRO2) 1 to 4 hours after termination of halothane anesthesia in 15 Wistar rats. In this 3-hour experimental period, mean CBF and CMRO2 were reduced to 29 and 43% of control values, respectively. CBF and CMRO2 determined at the beginning and end of the experimental period were not significantly different from each other. Cerebral venous O2 tension was significantly higher than in the control group, supporting recent suggestions of a primary, intrinsic effect of halothane on the homeostatic control of this variable. It is concluded that halothane is not useful for cerebral metabolic studies in the rat.
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PMID:Whole-brain blood flow and oxygen metabolism in the rat after halothane anesthesia. 118 83

The mechanisms underlying autoregulation of CBF were studied in 19 rabbits using laser-Doppler flowmetry. A cranial plexiglas window was chronically inserted in the skull with dental cement under general anesthesia. The animals then were reanesthetized 5-7 days later and subjected to aortic bleeding while CBF was measured with the probe placed on the window. In the first set of experiments, MABP was decreased (from 90 to 30 mm Hg) and was maintained constant for 1 min. During the first seconds, CBF followed the steep decrease of MABP. Then, CBF increased and reached a plateau within 3-13 s, depending on the severity of hypotension. Hyperemia occurred when blood was restored, and the CBF recovered from this posthypotensive hyperemia with a rapid phase (within 2 s) and a slow phase (total recovery within 1 min). The lower limit of autoregulation was found to be 40 mm Hg. An increase in CBF due to papaverine showed that vasodilation was not maximal below this limit. In the second set of experiments, the rabbits were subjected to four episodes of hypotension at 40 mm Hg each but of different durations (from 2-3 to 60 s). The posthypotensive hyperemia was not influenced by the duration of hypotension, but the time of the total recovery phase increased with the duration of hypotension. We conclude that there exist rapid adaptive mechanisms leading to autoregulation and that the vasodilation is not dependent upon the duration of hypotension.
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PMID:Rapid autoregulation of cerebral blood flow: a laser-Doppler flowmetry study. 161 45

Somatosensory evoked potentials (SEPs) were studied during graded incomplete cerebral ischaemia in eight goats and for the following 2 h. Anaesthesia was maintained with etomidate 1-1.5 mg kg-1 h-1 and 50% nitrous oxide in oxygen. Global cerebral blood flow (gCBF) was measured by a magnetic flow transducer at one internal maxillary artery after surgical occlusion of all other major extracranial cerebral arteries. CBF was reduced every 30 min by 25% with a lower limit of 15-20 ml 100 g-1 min-1. Regional cerebral blood flow (rCBF) in the brainstem and cortex was measured by the microsphere technique. The main findings were: (a) a graded decline in cortical SEP and a concurrent prolongation of the central conduction time (CCT) at gCBF values below 35 ml 100 g-1 min-1 and (b) an incomplete recovery of cortical SEP components during recirculation. Reduction of gCBF affected cortical rCBF more severely than brainstem rCBF. As a result, only cortical SEPs were changed. Our data suggest that reduced cerebral perfusion may result in altered cortical brain electrical activity that may be monitored by SEP recordings.
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PMID:Somatosensory evoked responses during and after graded brain ischaemia in goats. 187 23


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