摘要:

Relationships between plasma concentrations of fentanyl and its analgesic, respiratory and cardiovascular effects were determined in unanesthetized dogs. To avoid drug interactions the authors used trained unanesthetized spontaneously breathing dogs. After a control period in the awake state, fentanyl was injected in increasing amounts (2.5, 5, 20, 40, and 100 μ/kg) at 5-min intervals to a cumulative dose of 167.5 μg/kg administered over 20 min and its effects studied on pain responses (heart and blood pressure changes and somatic responses to tail clamping), respiration (respiratory rate, oxygen consumption, blood gas tensions), and circulation (heart rate and blood pressure). Plasma concentration/effect curves were derived by relating the changes in variables from the awake state to the corresponding plasma concentration (range 2–453 ng/ml). Maximum effects occurred at plasma concentrations at and around 30 ng/ml. Oxygen consumption decreased only slightly and remained well above the basal metabolic rate. Cardiac output, heart rate, respiratory rate, and arterial oxygen tension were almost halved during the full action of fentanyl. In dogs, fentanyl's analgesic action cannot be separated from its respiratory and cardiovascular effects. All receptor-mediated effects are maximal at the same plasma concentration, a phenomenon suggesting saturation of the opiate receptors.

ISSN:0003-3022    

出版商:OVID    

年代:1984

数据来源: OVID

摘要:

The effect of Althesin®, an anesthetic comprising two steroids, on regional cerebral function was determined by measurement of regional cerebral glucose utilization. Rats were anesthetized with an intravenous dose of 4, 8, or 20 mg total steroid/kg. These doses produced anesthesia for 12, 18, and 37 min, respectively. There were no physiologically significant effects of Althesin® (20 mg/kg) on body temperature, blood pH, or blood gases. Blood pressure and heart rate decreased slightly after administration of Althesin®. Althesin® had a profound effect on glucose consumption in many, but not all, cerebral structures. The forebrain (especially cerebral cortex) was affected most, while the hindbrain was much less so or not at all. This pattern of functional depression is in accord with the minimal effects observed on physiologic variables. The effects of Althesin® differ from those of other known anesthetics and suggest a unique mechanism. The possibility of action through naturally occurring steroid receptors is considered.

ISSN:0003-3022    

出版商:OVID    

年代:1984

数据来源: OVID

摘要:

Lung perfusion was studied in 10 patients (mean age 58 yr) in the lateral position during enflurane anesthesia. They were ventilated through a double-lumen endotracheal catheter: 1) by one ventilator with free distribution of ventilation between the lungs, with no (zero) end-expiratory pressure (ZEEP); 2) as above but with a general positive end-expiratory pressure (PEEP) of 9 cmH2O; or 3) by two ventilators with equal distribution of ventilation between the lungs and with a selective PEEP of 8 cmH2O to the dependent lung only. Total ventilation was on average 8 l/min (BTPS) throughout the study. During the first method, 34% of ventilation was distributed to the dependent and 66% to the nondependent lung. Cardiac output (thermodilution) was 4.5 l/min, 57% being distributed to the dependent lung as assessed by iv boli of Xenon 133. During the second method, ventilation was assumed to be distributed equally between the lungs. Cardiac output was decreased to 3.8 l/min, and the dependent lung received 81% of lung blood flow. During the third method, cardiac output was significantly greater than during the second method (4.1 l/min), 51% passing to the dependent lung. Peak and end-inspiratory airway pressures were 5–18 cm H2O lower during selective than during general PEEP. Arterial oxygen tension was significantly greater during the third method than during either of the other ventilator settings and the alveolar-arterial oxygen tension difference was almost halved compared with the first method. It is concluded that differential ventilation with selective PEEP improves ventilation-perfusion matching and thus oxygenation.

ISSN:0003-3022    

出版商:OVID    

年代:1984

数据来源: OVID

摘要:

The effect of halothane on the release and metabolism of norepinephrine during resting conditions and in response to electrical stimulation at 2 Hz was studied in isolated superfused segments of dog saphenous vein. Liquid chromatography with electrochemical detection was used to measure endogenous norepinephrine overflowing in response to electrical stimulation and the content of norepinephrine remaining in the tissue after stimulation. In other preparations, norepinephrine stores were labeled with [3H]norepinephrine, and measurements were made of [3H]norepinephrine and its metabolites (separated by column chromatography) in superfusates. Radiolabeled metabolites of norepinephrine produced intraneuronally (3,4-dihydroxyphenylglycol) and extraneuronally (O-methylated) were quantitated by liquid scintillation spectrometry. Electrically stimulated release and overflow of endogenous norepinephrine was decreased 11.9% at 0.75% halothane, 17.7% at 1.5% and 19.2% at 2.5% halothane. At each halothane concentration studied, the per cent of tissue NE content released in response to electrical stimulation was less. Halothane decreased the fraction of radioactivity lost during basal conditions and during stimulation. Less oxidative deamination of norepinephrine occurred in the presence of halothane.

ISSN:0003-3022    

出版商:OVID    

年代:1984

数据来源: OVID

摘要:

Twenty patients undergoing coronary artery bypass grafting under fentanyl-pancuronium anesthesia were studied. Continuous electrocardiographic (ECG) recording by a Holter Monitor was utilized to determine the incidence of ECG changes of myocardial ischemia during the precardiopulmonary bypass period and to determine the efficacy of an intravenous nitroglycerin (iv NTG) infusion for preventing ischemic ECG changes. Patients in Group 1 (n = 9) received a 0.5 μg · kg-1· min-1iv NTG infusion 20 min prior to induction of anesthesia and throughout the study. Patients in Group 2 (n = 11) received placebo. A randomized double-blind protocol was employed. Anesthesia was induced with fentanyl 3 μg · kg-1· min-1. After fentanyl 25 μg/kg and pancuronium 0.1 μg/kg, the trachea was intubated. After fentanyl 50 μg/kg surgery commenced. Prior to induction of anesthesia, iv NTG caused significant decreases in mean arterial pressure and pulmonary capillary wedge pressure, whereas placebo had no effect. However, subsequent to induction of anesthesia, hemodynamics in the two groups were identical. Fifty per cent of patients developed ECG changes of myocardial ischemia during the period from induction of anesthesia to commencement of cardiopulmonary bypass. The incidence of ischemic ECG changes was virtually identical in Group 1 (5/9) and Group 2 (5/11). Ischemic ECG changes were associated with increases in heart rate, mean arterial pressure, and rate pressure product, and decreases in the endocardial viability ratio (DPTI/SPTI). Increases in pulmonary capillary wedge pressure were not associated with myocardial ischemia. Fentanyl-pancuronium anesthesia, as administered in this study, was associated with a high incidence of myocardial ischemia. Ischemia was related to deteriorating myocardial oxygen balance resulting from the cardiovascular effects of anesthetic induction, endotracheal intubation, and surgery. Intravenous NTG was not superior to placebo for the prevention of ECG changes of myocardial ischemia during fentanyl-pancuronium anesthesia for coronary artery surgery.

ISSN:0003-3022    

出版商:OVID    

年代:1984

数据来源: OVID

摘要:

While the systemic cardiovascular consequences of infrarenal aortic cross-clamping during aortic abdominal surgery are well documented, its repercussions on renal hemodynamics in humans have not been reported. In 12 patients, scheduled for elective aortic surgery, renal clearances, using51Cr EDTA and125I hippuran, were measured before, during, and after infrarenal aortic cross-clamping. A continuous infusion of mannitol 20% at a rate of 100 ml/h was administered throughout the study. Arterial and renal venous blood sampling, obtained at the midpoint of each period, permitted calculation of the extraction fraction of125I hippuran and accurate determination of renal blood flow and its cortical-extracortical distribution. Although cardiac output and systemic vascular resistance did not change significantly between the three study periods, infrarenal aortic cross-clamping decreased125I hippuran clearance by 29 ± 15% (P< 0.05) and renal blood flow by 38 ± 14% (P< 0.001). Simultaneously, an increase of 75 ± 31% in renal vascular resistance (P< 0.05) was observed and the extraction fraction of125I hippuran increased from 0.67 ± 0.05 to 0.74 ± 0.05 (P< 0.01). All of these changes, which indicate global diminution of renal perfusion with a redistribution of renal blood flow toward the cortical compartment, persisted for at least 1 h after release of the aortic clamp. Early signs of renal tubular damage, such as the appearance of lysozyme and ligandine in the urine, however, were never observed. The authors conclude that infrarenal aortic cross-clamping produces profound and sustained alterations in renal hemodynamics and may be harmful in patients with impaired renal function or when surgical occlusion of the aorta is prolonged.

ISSN:0003-3022    

出版商:OVID    

年代:1984

数据来源: OVID

摘要:

The cardiovascular effects of adenosine-induced controlled hypotension were studied in 10 patients undergoing cerebral aneurysm surgery. Adenosine and its metabolites were measured in arterial plasma using high-pressure liquid chromatography. Whole body and cerebral arteriovenous oxygen content differences (AVDO2), arterial lactate levels, and arteriojugular lactate differences were determined. In order to reduce the dose requirement of adenosine, the patients were pretreated with the adenosine uptake inhibitor, dipyridamole (0.3–0.4 mg · kg-1). During the infusion of adenosine (0.14 ± 0.04 mg · kg-1· min-1) the mean arterial blood pressure decreased by 43%, from 82 to 46 mmHg, during a mean hypotensive period of 32 min, without signs of tachyphylaxis. The arterial adenosine level increased from 0.15 ± 0.02 to 2.45 ± 0.65 μM (P< 0.01). Hypotension was caused by a profound decrease in peripheral vascular resistance (61 ± 3%,P< 0.01), which was accompanied by an increase in cardiac output (44 ± 9%,P< 0.01). Heart rate increased moderately by 16 ± 5% (P< 0.01). Pulmonary vascular resistance and central venous pressures were unaffected. Arterial lactate and PaO2were unchanged, while whole body oxygen consumption was decreased by 13 ± 4% (P< 0.05). The AVDO2across the brain was decreased by 37 ± 5% (P< 0.05) without signs of lactate formation. The authors conclude that adenosine rapidly induces a stable and easily controlled hypotension in humans by dilation of arterial resistance vasculature.

ISSN:0003-3022    

出版商:OVID    

年代:1984

数据来源: OVID

摘要:

The effects of 46 h of mechanical ventilation and PEEP on urinary output, sodium excretion, and renal and cardiovascular function were examined. Dogs sedated with sodium pentobarbital were ventilated using one of three modes: spontaneous ventilation (SV), controlled mechanical ventilation (CMV), or CMV with 10 cmH2O positive end-expiratory pressure (CMV with PEEP). Intravenous fluids were given at a constant rate throughout the study and measurements of renal and cardiovascular function were made over four periods. Dogs whose lungs were ventilated with PEEP displayed more than two times the amount of fluid retention seen in the other groups as assessed by mean weight gain. This was due to an initial depression of urine flow, sodium excretion, and free water clearance. Urinary flow rate approximated the rate of fluid infusion by 20 h in SV dogs and by 27 h during CMV, while the maximum during CMV with PEEP occurred at 46 h. There were no significant differences in glomerular filtration rate, renal corticomedullary blood flow distribution, or renal blood flow between groups. During the 46 h, cardiac index increased (SV, +16%; CMV, +19%; CMV with PEEP, +64%), while systemic vascular resistance (SV, –28%; CMV, –30%; CMV with PEEP, –57%), renal vascular resistance (SV, –12%; CMV, –20%; CMV with PEEP, –23%), and mean arterial pressure (SV, –16%; CMV, –15%; CMV with PEEP, –15%) decreased in all groups. This study has demonstrated that when a constant sodium and water load was provided, the SV and CMV groups were rapidly able to adjust the urinary excretion to meet input, while the return of renal function toward normal in the CMV with PEEP group was delayed until almost 46 h from the start of ventilation.

ISSN:0003-3022    

出版商:OVID    

年代:1984

数据来源: OVID

摘要:

The effect of high-frequency ventilation (HFV) on cerebral blood flow (CBF) at normal and elevated intracranial pressure (ICP) was compared with flows measured under the same conditions during intermittent positive pressure ventilation (IPPV). Renal, lung (bronchial artery supply), and cardiac blood flows also were measured during HFV and compared with flows observed during IPPV. Measurements were made in canines with stable hemodynamic variables and arterial CO2and O2tensions in the normal range. CBF during HFV was comparable to the CBF during IPPV. Following an increase in ICP to a mean of 44 ± 18 mmHg (SD), mean CBF decreased to 22.5 ± 11 ml · 100 g-1· min-1(SD) during IPPV and 21.7 ± 13.2 ml · 100 g-1· min-1(SD) during HFV. No statistical differences could be noted in regional or global flow as a function of ventilatory mode. Renal, lung (bronchial artery supply), and cardiac blood flows also showed no statistical variation between HFV and IPPV. Ventilator-synchronous fluctuations in ICP observed during IPPV were reduced during HFV at normal ICP and eliminated by HFV at elevated ICP.

ISSN:0003-3022    

出版商:OVID    

年代:1984

数据来源: OVID

摘要:

Gallamine, metocurine, pancuronium, andd-tubocurarine were compared when given alone and in combination with isolated guinea pig nerve-lumbrical preparations stimulated via the nerve. The experimental design was set up to control the effects of variation among preparations, order of administration, and time of administration (i.e., freshvs.older preparation). The result was an assay able to measure potentiation with a coefficient of variation of 3%. A format for a graphic presentation to summarize such results is presented and discussed. Two combinations, gallamine plusd-tubocurarine and gallamine plus pancuronium, showed no sign of an interaction beyond that to be expected from a simple competitive interaction. Two others, metocurine plus pancuronium and gallamine plus metocurine, showed about a twofold greater potency when combined than would have been expected. The last two sets, pancuronium plusd-tubocurarine and metocurine plusd-tubocurarine, showed a slight degree of potentiation. These studies demonstrate that the deviation from simple additivity seenin vivopersists when examined in a system free from artifacts associated with uptake and distribution in the whole organism.

ISSN:0003-3022    

出版商:OVID    

年代:1984

数据来源: OVID