摘要:

The effects of scopolamine and morphine sulfate on brain-stem auditory evoked potentials (BAEPs) were studied in 10 rhesus (Macaca mulatta) monkeys. Study drugs were given intravenously to unanesthetized animals and BAEPs recorded at 3-min and 30-min intervals after administration of 0.1 mg/kg and 0.32 mg/kg of scopolamine and 15 min after administration of 3.2 mg/kg morphine at the end of the experiment. No significant change in either latency or amplitude of different components of BAEPs was observed.

ISSN:0003-3022    

出版商:OVID    

年代:1985

数据来源: OVID

摘要:

Using a dual-isohypercapnic technique, the authors determined the effect of equipotent doses of methohexital (1.5 mg/kg) and etomidate (0.3 mg/kg) on the ventilatory response to CO2(VERCO2) in six healthy volunteers. Speed of induction and duration of hypnosis did not differ significantly between the two drugs. Within 2 min after injection, the slope of VERCO2decreased significantly after both methohexital (from 2.52 to a minimum of 0·15 1.min−1mmHg−1,P< 0.05) and etomidate (from 2.56 to a minimum of 0.62 1·min−1·mmHg−1,P< 0.05); the magnitude of this depression did not differ significantly between the drugs. Methohexital also caused a significant decrease in minute ventilation at end-tidal PCO2of 46 mmHg (VE46) from 14.6 to 4.3 1·min−1within 60 s after injection (P< 0.05). In contrast, after etomidate VE46 gradually increased from 17.9 1·min−1to a maximum of 31.6 1 ± min−1at 3.5 min after injection (P< 0.05); respiratory rate increased significantly, while changes in tidal volume were not significant. Effects of etomidate and methohexital on VE46 differed significantly (P< 0.001). These data indicate that, while etomidate and methohexital similarly depress the medullary centers that modify ventilatory drive in response to changing CO2tensions, ventilation at any given CO2tension is greater after etomidate than after methohexital. This indicates that etomidate may cause a CO2-independent stimulation of ventilation, suggesting its use for induction of anesthesia in cases where maintenance of spontaneous ventilation is desirable.

ISSN:0003-3022    

出版商:OVID    

年代:1985

数据来源: OVID

摘要:

The influence of halothane 0.8–1.2% inspired on the peripheral hypoxic chemoreflex was investigated in 13 cats subjected to artificial brain stem perfusion (ABP). This technique allows for an independent control of blood gas tensions and halothane concentration between blood perfusing the brain stem (central) and the systemic circulation (peripheral). In six cats the ventilatory response to isocapnic hypoxia was assessed during overall halothane anesthesia (HO) before and during ABP. Before ABP, systemic and brain stem circulations both were rendered hypoxic. During ABP, hypoxia was induced systemically while the brain stem was maintained hyperoxic. The ventilatory response in non-ABP cats (mean 698 ml·min−1at Pao26.6 kPa; 50 mmHg) was about half the response in ABP cats (mean 1,194 ml·min−1at Pao26.5 kPa; 49 mmHg), indicating that in the presence of halothane, central hypoxia depressed ventilation appreciably. Compared with chloralose-urethane anesthesia (CU), halothane reduced the ventilatory response to hypoxia in both perfusion conditions but never abolished it. To assess the influence of halothane on peripheral and central mediation of the CO2response during hypoxia, each was assessed during CU anesthesia, during HO, and with halothane applied exclusively peripherally against a background of CU (CUHP). In all drug states, the periphery was kept hypoxic and brain stem hyperoxic. Compared with CU anesthesia, HO and CUHP anesthesia reduced both peripheral (Sp) and central (Sc) CO2sensitivity but not the Sp/Sc ratio. Similarly, the extrapolated Paco2at zero ventilation was not detectably different among these three states. This suggests that in this model, the depression of the peripheral chemoreflex response to CO2in the presence of hypoxemia by halothane applied peripherally is due to peripheral effects of halothane unrelated to chemoreceptor function. The authors' findings indicate that halothane applied to all structures except the brain stem in an artificially perfused cat model depresses the overall peripheral chemoreflex pathway. A direct effect of halothane on the peripheral chemoreceptors cannot be excluded; with respect to the CO2response in the presence of hypoxemia such an effect may be of minor importance in comparison with the depressant effects of halothane on other peripheral structures,i.e., the neuromechanical link between the brain stem and ventilatory movement.

ISSN:0003-3022    

出版商:OVID    

年代:1985

数据来源: OVID

摘要:

This study was performed to determine the cardiovascular and respiratory effects of ketanserin, a specffic 5-HT2antagonist, following oleic acid lung injury in anesthetized dogs. Following intravenous administration of oleic acid (0.1 ml/kg) to a control group (N = 7), systemic blood pressure decreased significantly. This lowered level of systemic blood pressure was maintained throughout the experiment. Cardiac output gradually decreased following oleic acid administration, while total peripheral resistance, pulmonary vascular resistance, and pulmonary arterial pressure were increased significantly. In a group treated with intravenous ketanserin (0.16 mg/kg, N = 7) 60 min after the injection of oleic acid, no decrease in cardiac output was seen. The increased total peripheral resistance, pulmonary vascular resistance, and pulmonary arterial pressure following injection of oleic acid also were returned toward preoleic acid levels. However systemic blood pressure showed no significant improvement after treatment with ketanserin nor did ketanserin protect against progressive hypoxemia following pulmonary injury with oleic acid. A progressive increase in hemoglobin concentration was seen after oleic acid in the control group. This recovered toward the preoleic acid level following treatment with ketanserin. The postmortem lung wet-dry weight ratio was significantly lower in the treated group compared with the control group. In conclusion, these data suggest that serotonin may have a role in including cardiopulmonary hemodynamic disturbances and in producing increases in extravascular lung water when pulmonary edema is induced by oleic acid injection in anesthetized dogs.

ISSN:0003-3022    

出版商:OVID    

年代:1985

数据来源: OVID

摘要:

This study was designed to evaluate the influence of inhalational agents on the intestinal circulation in an isolated loop preparation. Sixty dogs were studied, using three intestinal segments from each dog. Selected intestinal segments were pumped with aortic blood at a constant pressure of 100 mmHg. A mixture of86Rb and 9-μm spheres labeled with141Ce was injected into the arterial cannula supplying the intestinal loop, while mesenteric venous blood was collected for activity counting. A very strong and significant correlation was found between rubidium clearance and microsphere entrapment (r = 0.97,P< 0.0001), suggesting that the shunting of 9-μm spheres through the intestines reflects the arteriovenous shunting of blood. Nitrous oxide anesthesia was accompanied by a higher vascular resistance (VR), lower flow (F), rubidium clearance (Cl-Rb), and microspheres entrapment (Cl-Sph) than pentobarbital anesthesia, indicating that the vascular bed in the intestinal segment was constricted and flow (total and nutritive) decreased. Halothane, enflurane, and isoflurane anesthesia were accompanied by a much lower arteriovenous oxygen content difference (AVDO2) and oxygen uptake than pentobarbital or nitrous oxide. Compared with pentobarbital, enflurane anesthesia was not accompanied by marked differences in VR, F, Cl-Rb, and Cl-Sph; halothane at 2 MAC decreased VR and increased F and Cl-Rb while isoflurane increased VR and decreased F. α-Adrenoceptor blockade with phentolamine (1 mg·kg−1) abolished isoflurane-induced vasoconstriction, suggesting that the increase in VR was mediated via circulating catecholamines. Decreases in mesenteric blood flow, which always have been observed during inhalation anesthesia, primarily are caused by the indirect effects of anesthetics mediated through changes in systemic circulation and the central nervous system.

ISSN:0003-3022    

出版商:OVID    

年代:1985

数据来源: OVID

摘要:

Halothane lessens the dose of epinephrine necessary to induce ventricular arrhythmias. However, results of a previous study in dogs anesthetized at two halothane concentrations suggested, but did not confirm, that at the higher concentration (1.7%) myocardial sensitization to epinephrine was less pronounced. This study was designed to determine the myocardial sensitizing effect of halothane at four concentrations: 0.5, 1.0, 1.5, and 2%. To define the appropriate time interval between repeated epinephrine infusions, plasma epinephrine decay curves were assessed. These data indicated that at 7 min the contribution of the residual epinephrine level to the peak level was negligible. Therefore, 7 min was selected as the interval between epinephrine infusions. The arrhythmogenic dose of epinephrine (ADE) was measured at four concentrations of halothane, 0.5, 1.0, 1.5, and 2.0%. To determine the ADE at the subanesthetic concentration of halothane (0.5%), anesthesia was supplemented with etomidate. In a preliminary study, the authors confirmed that this intravenous hypnotic agent did not affect the halothane-epinephrine arrhythmogenic interaction. By analysis of variance, halothane concentration was shown to have no significant influence on the ADE (P> 0.05). The authors' data indicate that, over a clinically appropriate range, halothane concentration does not alter the threshold for the development of epinephrine-induced ventricular arrhythmias.

ISSN:0003-3022    

出版商:OVID    

年代:1985

数据来源: OVID

摘要:

Cytogetic methods are used increasingly for monitoring exposure to potential mutagens/carcinogens in the environment. By one such method, the sister chromatid exchange (SCE) test, comparison of different groups of hospital personnel has not indicated any mutagenic effect of occupational exposure to waste anesthetic gases. Since no information is available on repeated examinations of operating room personnel during a longer period of occupational exposure, the authors examined SCE in lymphocytes in a total number of 191 venous blood samples drawn from 14 previously unexposed nurses before and during up to 32 months of training as nurse-anesthetists. The initial SCE/cell ranged from 8.03 to 13.13 SCE/cell. Individual linear regressions were performed for the transformed variable, y = (sum SCE + 1)1/2+ (sum SCE + 1)1/2, on time; and for the first 6-month period, the weighted mean of individual slopes was b0= −0.119 ± 0.088, not significantly different from zero. Calculated for the whole observation period, b0= 0.030 ± 0.014,P= 0.034 (two-tailedttest). Converted into SCE/cell, SCE would decrease 0.10 SCE/cell for each 6-month period of exposure (95% confidence limits 0.07–0.13 SCE/cell). The reason for this apparent decrease remains unknown. The results of the present study were in accord with previous studies of operating room personnel and of patients anesthetized with inhaled anesthetics. It was concluded that there is no indication, from the SCE test, of a mutagenic action due to exposurein vivoto currently used inhalation anesthetics.

ISSN:0003-3022    

出版商:OVID    

年代:1985

数据来源: OVID

摘要:

The pharmacokinetics of alfentanil were studied in 11 patients with alcoholic cirrhosis and 10 control patients during general anesthesia. All patients received 50 μg·kg−1alfentanil as an intravenous bolus injection. Plasma concentrations were measured acintervals up to 10 h, using a specific radioimmunoassay technique. Protein binding was measured by equilibrium dialysis. Patients with cirrhosis had a significantly lower (P< 0.01) plasma clearance of alfentanil of 1.6 ± 1.0 ml·min−1·kg−1(mean ± SD) instead of 3.1 ± 1.6 ml · min−1· kg−1in the controls. The total apparent volume of distribution was similar in the two groups. The elimination half-life was prolonged from 90 ± 18 min in the controls to 219 ± 128 min in the cirrhotics (P< 0.01). Patients with cirrhosis had a higher (P< 0.01) alfentanil plasma-free fraction (18.6 ± 9.4%) compared with the control patients (11.5 ± 3.9%). When kinetic parameters were corrected for protein binding, the unbound volume of distribution and the free drug clearance were decreased significantly in patients with cirrhosis. Since the concentration α1-glycoprotein to which alfentanil mainly is bound in plasma did not differ in the two groups, it is suggested that the increase in the free fraction is caused by an alteration of binding sites of this protein in patients with cirrhosis. Owing to its delayed elimination and increased free fraction, alfentanil will exert a prolonged and pronounced effect in patients with cirrhosis.

ISSN:0003-3022    

出版商:OVID    

年代:1985

数据来源: OVID

摘要:

Distribution of ventilation and perfusion in relation to ventilation-perfusion ratio (&OV0312;A/&OV0312;) were studied in 14 patients, with a mean age of 59 yr, before elective lung surgery, in the supine position when awake, during intravenous anesthesia and mechanical ventilation with air, after increasing the fraction of inspired oxygen (FI02) to 0.5, and in the lateral position. Before anesthesia, small inert gas shunts and perfusion of low &OV0312;A/&OV0312; regions, indicating some degree of &OV0312;A/&OV0312; mismatch, were observed in several patients. After induction, FIo2= 0.21, the major changes were a significant decrease in cardiac output and an increase in log SD for perfusion from 0.77 ± 0.45 (SD) to 1.13 ± 0.50 (SD), while the shunt remained low at 1% of cardiac output and arterial oxygen tension (PaO2) was unchanged. An increase to FIO2= 0.5 induced only small changes with a shunt of 2.5% of cardiac output. In the lateral position, the shunt was 4.0% and increases in ventilation to high &OV0312;A/&OV0312; regions were observed. The lack of marked changes in the &OV0312;A/&OV0312; distribution after induction either could be a result of only minor alterations in the distribution of ventilation and perfusion or an effective vascular response to alveolar hypoxia (hypoxic pulmonary vasoconstriction, HPV).

ISSN:0003-3022    

出版商:OVID    

年代:1985

数据来源: OVID

摘要:

After Morton's demonstration in the Ether Dome of the Massachusetts General Hospital, anesthesia for surgery was accepted around the world at a speed unusually fast for any medical or scientific innovation. However, the concept of surgical anesthesia had been rejected on four occasions during the preceding 40 years. The rapid acceptance of anesthesia in 1846 appears to have had a political and social basis as well as medical. Two factors are particularly important. First was a change in the perception of disease and pain; both lost religious connotations and became biologic phenomena as part of a process of secularization that affected all aspects of Western society. Second was the growth of a sense of well-being and progress, which imbued patients and physicians alike with confidence in their ability to control natural processes. During the last half century, pain has remained secular, but the confidence in both progress and the ability to control nature may have diminished.

ISSN:0003-3022    

出版商:OVID    

年代:1985

数据来源: OVID