摘要:

The purpose of this study was to evaluate the time-dependent effects of steady-state halothane anesthesia on cerebrovascular variables and their relationship to cerebrospinal fluid (CSF)pH. Eight mongrel dogs underwent a 7-h anesthetic, receiving halothane (1.0% end-tidal), O2(50%), and balance N2. Cerebral blood flow (CBF) was measured by injection of radioactively labeled micro-spheres. CSF was sampled from the cisterna magna and cerebral venous blood from the superior sagittal sinus. Measurements were made at 2 h postinduction and hourly for 5 h thereafter. Total CBF at 2 h postinduction was 148 ± 36 ml·100 g−1·min−1and showed a significant decay over the subsequent 5 h to 70 ± 3 ml·100 g−1·min−1. Regional variations were noted, those areas with highest initial flows showing both a greater relative and absolute reduction in flow. Cerebral vascular resistance increased significantly (39%), as did mean arterial pressure (15%). CSFpH values remained constant throughout the experiment. Arterial blood acid-base physiology was also unchanged. Sagittal sinus PCO2increased significantly from 43 ± 4 to 49 ± 3 mmHg while sagittal sinuspH decreased from 7.31 ± 0.01 to 7.37 ± 0.02, consistent with the normalization of CBF. Cerebral metabolic oxygen consumption did not change significantly. The authors conclude that time-dependent changes in cerebrovascular parameters under prolonged steady-state halothane anesthesia are not due to changes in CSFpH and thus brain extracellular acid-base chemistry.

ISSN:0003-3022    

出版商:OVID    

年代:1985

数据来源: OVID

摘要:

Median nerve somatosensory evoked potentials (MnSSEPs), brain stem auditory evoked responses (BAERs), and the cortical electroencephalogram (EEG) were recorded in six patients during a 62·min infusion of sodium thiopental (STP) at a rate of 1.25 mg·kg−1·min−1(total dose, 77.5 mg/kg). The EEG became isoelectric after 22 ± 8 (SD) min of STP infusion. Dose-related changes in the latencies and amplitudes of various evoked response wave forms were observed. However, in no instance was any component of either the MnSSEP or the BAER rendered unobtainable by STP administration. For the MnSSEP, progressive increases in the central conduction time (5.33 ± 0.41 ms preinductionvs.7.46 ± 1.2 ms at t = 60 min) and in the latency of the cortical primary specific complex were observed simultaneously with significant reductions in the amplitude of the latter (2.10 ± 0.85 μV preinductionvs.0.85 ± 0.55 μV at t = 60 min). Changes in the latency and amplitude of the response recorded over the upper cervical spine (C2) were not statistically significant in this small population. For the BAER, progressive and significant increases in the latencies of Waves I, III, V (e.g., Wave V latency: 6.16 ± 0.24vs.6.87 ± 0.31 ms) and in the I-III, III-V, and the I-V interwave latencies were observed. The amplitudes of the BAER components were not significantly altered. The authors conclude that the administration of a dose of STP in excess of twice that required to produce EEG isoelectricity can be compatible with effective monitoring of MnSSEPs and BAERs. However, STP produces dose-related changes in both evoked response wave forms, which must be considered in the interpretation of responses elicited during STP anesthesia.

ISSN:0003-3022    

出版商:OVID    

年代:1985

数据来源: OVID

摘要:

The effect of fentanyl on increases in heart rate and mean arterial pressure elicited by electric stimulation of a branch of the radial nerve was studied in anesthetized, paralyzed, and artificially ventilated dogs. In one group, a bolus of 100 μg/kg of fentanyl depressed the evoked changes in heart rate and arterial pressure by 82 and 75%, respectively, by 5 min, and recovery occurred within 90 min. A second group was given increasing bolus doses of fentanyl from 1.5 to 100 μg/kg every 20 min for 200 min. The doses and intervals were chosen to give a logarithmic increase in plasma concentration of fentanyl to include a final bolus dose of 100 μg/kg and were predicted by a two-compartment pharmaco-kinetic model derived from data of the first group. In the second group, the bolus dose of 100 μg/kg after 5 min had no significant effect on evoked cardiovascular responses. Over the following 2 h, the evoked changes in heart rate and arterial pressure increased above those preceding the 100 μg/kg dose. An additional bolus dose of 100 μg/kg given 2 h after the first did not depress the evoked reflexes below the control values. It was concluded that tolerance to the effects of fentanyl can occur within 3 h and that for evoked responses to arterial pressure, rebound withdrawal effects can be seen within an additional 90 min.

ISSN:0003-3022    

出版商:OVID    

年代:1985

数据来源: OVID

摘要:

Local cerebral glucose utilization was measured in rats during nitrous oxide and pentobarbital anesthesia, using the 2-[14C]-deoxyglucose method. During nitrous oxide anesthesia, 67%, marked heterogeneity of glucose utilization was observed. During pentobarbital anesthesia (30 mg/kg), glucose utilization decreased, the decrease being pronounced in the structures where glucose utilization was high during nitrous oxide anesthesia. During combined use of nitrous oxide and pentobarbital (30 mg/kg), with an electroencephalogram (EEG) consisting of 4–6 Hz wave superimposed by 10–15 Hz wave, glucose utilization was higher in many brain structures, including the midbrain reticular formation, than that observed during pentobarbital (30 mg/kg) anesthesia alone. With pentobarbital, 125 mg/kg, the EEG became nearly flat and a dose-related decrease in glucose utilization was observed in the cerebral cortices and inferior colliculus but not observed in any other structures. During the combined use of nitrous oxide and pentobarbital (125 mg/kg), the EEG was nearly flat, and no statistically significant differences in glucose utilization were observed as compared with those during pentobarbital (125 mg/kg) anesthesia in any of the structures examined. The results suggest that nitrous oxide and pentobarbital affect local cerebral glucose metabolism differently and that nitrous oxide acts as cerebral metabolic stimulant in the presence of cortical function during pentobarbital anesthesia.

ISSN:0003-3022    

出版商:OVID    

年代:1985

数据来源: OVID

摘要:

The authors evaluated the potential of a variety of anesthetics in mice to produce subsequent alterations in host defenses. Specific monoclonal antibodies and immunofluorescent microscopy were used to enumerate splenic helper/inducer: suppressor/cytotoxic lymphocyte ratios (HSR), and resistance to bacterial challenge was evaluated by a cecal ligation and puncture (CLP) model. Two hours of anesthesia with the intravenous agents ketamine and pentobarbital and with the inhalational agents isoflurane, enflurane, halothane, and halothane-nitrous oxide, were utilized. All anesthetics produced marked depression in the HSR, measured 24 h postanesthesia (P< 0.05); with all agents, helper T-cell populations were decreased and suppressor populations increased. The HSR remained depressed 72 h postanesthetic, following both ketamine and halothane anesthesia (P< 0.05). A dose-response curve was determined with enflurane; increasing the anesthetic time from 1 to 6 h resulted in progressively greater depression of the HSR 24 h later. Changes in lymphocyte subtypes of similar magnitude were found in mice after burn injury or hind limb crush injury and amputation, whereas simple laparotomy did not produce such changes. Serum corticosterone levels were not elevated 24 h post-anesthetic with enflurane, suggesting that the alterations were not nonspecific stress reactions. Resistance to sepsis was determined by measuring survival for 96 h after CLP. With CLP performed 24 h following 2 h anesthesia, mortality was increased from normal: control mortality 36.3%; ketamine 65.0% (P< 0.023); isoflurane 69.5% (P< 0.006); enflurane 84.2% (P< 0.0002). Anesthesia produces dose-related alterations in splenic helper/inducer and suppressor/cytotoxic lymphocyte populations in mice, which persist for at least 72 h; resistance to subsequent bacterial challenge also is reduced, although the two effects are not proven to be related.

ISSN:0003-3022    

出版商:OVID    

年代:1985

数据来源: OVID

摘要:

The authors examined the effects of large intravenous doses of sufentanil (5–160 μg/kg) on cerebral blood flow (CBF) and cerebral metabolic rate for oxygen (CMRo,) in rats. CBF and CMRo2were measured by a modified Kety-Schmidt technique using135Xenon washout. Progressive decreases in CBF and CMRo2occurred in animals receiving sufentanil. The maximum decrease was 53% and 40% for CBF and CMRo2, respectively, at a dose of 80 μg/kg. The values for CBF and CMRo2in this group were 105 ± 10 ml · 100 g−1· min−1(mean ± SEM) and 6.5 ± 0.5 ml · 100 g−1· min−1, respectively, compared with 226 ± 28 ml · 100 g−1· min−1and 10.9 ± 1 ml · 100 g−1· min−1in the control group, which received N2O 70% in oxygen. Larger doses of sufentanil did not cause further significant changes in CBF and CMRo2. Sharp waves appeared on the electroencephalogram (EEG) of all the animals following sufentanil injection, and some animals had EEG changes develop consistent with seizure activity. This seizure-like activity appeared to consist of a single episode of short duration in the groups receiving 5, 10, and 20 μg/kg sufentanil. The incidence and frequency of seizure activity increased in the groups receiving higher doses of sufentanil, although the duration of seizures was still short. The results of this study indicate that sufentanil causes a significant decrease in CBF and CMRo2similar to that previously reported for fentanyl, and high doses of sufentanil may cause frequent seizure-like patterns appearing on EEG.

ISSN:0003-3022    

出版商:OVID    

年代:1985

数据来源: OVID

摘要:

The emergency management of respiratory arrest can be a difficult problem. The authors hypothesized that tracheal insufflation of O2(TRIO) at low flows could provide adequate oxygenation and sufficient CO2elimination to sustain life until more definitive (but more difficult to implement) measures could be applied. Therefore, 10 anesthetized, paralyzed dogs (15.9–48.2 kg), initially ventilated with conventional mechanical ventilation (CMV) using room air, were studied. CMV was stopped and a 1− or 5-mm id catheter with a constant flow (V) of O2ranging from 0.2 to 3.0 1/min was inserted to within 1 cm of the carina. With all flow rates, Pao2and Paco2initially increased with time; the rate of increase of Pao2was greater and that of Paco2was less, with increasing V. In three dogs studied at flow rates of 2.0 or 3.0 1/min, arterial blood gases reached a plateau after about 2 h:pH = 6.87; Pco2= 164 mmHg; and Po1= 363 mmHg (mean values). These studies were stopped at between 4 and 5 h, with no dogs showing any signs of cardiovascular or other decompensation. Results in which catheter position was studied indicated that as long as the catheter tip was at or past the carina, gas transport was similar to that observed when the catheter tip was 1 cm proximal to the carina. The authors conclude that TRIO at low flow rates can produce sufficient gas exchange to support life for prolonged periods in apneic dogs.

ISSN:0003-3022    

出版商:OVID    

年代:1985

数据来源: OVID

摘要:

Changes in hepatic plasma flow (HPF) during sodium nitro-prusside (SNP) induced hypotension were studied in 14 patients undergoing intracranial aneurysm surgery under neurolept anesthesia. Patients were monitored with the use of a radial artery catheter and a thermistor-tipped Swan-Ganz® catheter. Hypotension was induced with incremental increases in the rate of SNP infusion until a stable mean arterial pressure (MAP) 35–55 mmHg had been achieved. In one group (Group A) of 10 patients, indocyanine green (ICG) clearance was determined simultaneously with hemodynamic variables, before and during SNP hypotension. In a second group (Group B) of four patients, a catheter was inserted into a hepatic vein to determine the ICG hepatic extraction (HE) coefficient. In Group A, MAP decreased from 73 ± 10 (SD) to 41 ± 9 mmHg, while cardiac index (CI) decreased in six patients and increased in four patients. However, the mean value of CI did not change significantly. The mean value of ICG clearance was not significantly affected by SNP hypotension. Nevertheless, a positive linear correlation existed between individual variation in CI and ICG clearance (r = 0.96). On the other hand, no correlation was noted between the change in MAP and ICG clearance. In Group B patients, the ICG HE coefficient remained unchanged during SNP hypotension, suggesting that ICG clearance varies only according to the variation in HPF. In conclusion, this study demonstrated that HPF did not decrease, despite a range of 20–60% decrease in blood pressure when CI is maintaind during SNP hypotension.

ISSN:0003-3022    

出版商:OVID    

年代:1985

数据来源: OVID

摘要:

Recent reports have described resistance to pancuronium-induced neuromuscular blockade in patients chronically receiving anticon-vulsants. This study examines the pharmacokinetics and pharma-codynamics of metocurine (MTC) in 12 patients undergoing cra-niotomy—six on chronic phenytoin therapy and six comparable controls. Each patient received MTC 0.2 mg/kg during the induction of general anesthesia. Quantification of plasma MTC concentration was performed by radioimmunoassay, while the response to MTC was evaluated by evoked compound electromyography (ECEMG). Patients in the phenytoin group were resistant to this dosage of MTC, as demonstrated by their response (83 ± 16% compared with 98 ± 2% depression of ECEMG in control patients,P< 0.05) and by recovery index, defined as the time required for recovery from 25 to 75% of the control ECEMG (53 ± 22 min compared with 125 ± 54 min in control patients,P< 0.01). Similarly, the total duration of neuromuscular blockade, measured to recovery to 90% of control ECEMG, was significantly shorter in the phenytoin group (122 ± 25 min compared with 269 ± 64 min in the control group,P< 0.01). Plasma concentration-time curves were fit to biexponential equations for both groups. These were used to generate two-compartment models. Neither the model parameters nor the plasma concentrations of MTC at any time in the study were significantly different for the two groups. The pharmacody-namic analysis, however, showed that patients on phenytoin require a higher plasma concentration of MTC (0.415 ± 0.095 μg/ml compared with 0.249 ± 0.066 μg/ml in control patients at 50% ECEMG,P< 0.01) to effect a given level of neuromuscular blockade. This resistance could be demonstrated at all levels of neuromuscular blockade (20–80% depression of ECEMG). On the basis of this study, it can be concluded that resistance to metocurine in patients chronically being treated with phenytoin does exist as a result of some, yet undefined, pharmacodynamic alteration in this patient group.

ISSN:0003-3022    

出版商:OVID    

年代:1985

数据来源: OVID

摘要:

Succinylcholine was administered to 10 healthy unanesthetized volunteers to assess its effect on respiratory and nonrespiratory muscle strength and the ventilatory response to CO2. Isohypercap-nia with PETCO28–10 mmHg above control was maintained throughout the study, succinylcholine infusion rates were increased from 20 μg·kg−1·min−1until grip strength (GS) was 20% of control. CO2-stimulated ventilation was 16.1 ± 1.8 1/min (mean ± SD), approximately three times control, and remained at that level throughout the study because of nonsignificant decreases in tidal volume and increases in respiratory frequency. Respiratory strength, as measured by maximum inspiratory pressure (IP), maximum expiratory pressure (EP), and forced vital capacity (FVC), was spared relative to GS. When GS = 50% of control, IP = 86 ± 8% of control, EP = 78 ± 15%, and FVC = 86 ± 9%. Wide variation occurred from subject to subject in the succinylcholineversusGS dose-response curve position. However, in all subjects the slope of the dose-response curve was very steep.

ISSN:0003-3022    

出版商:OVID    

年代:1985

数据来源: OVID