ISSN:0003-3022    

出版商:OVID    

年代:1986

数据来源: OVID

ISSN:0003-3022    

出版商:OVID    

年代:1986

数据来源: OVID

ISSN:0003-3022    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

To design an efficient infusion regimen from pharmacokinetic data, it is necessary to know the alfentanil plasma concentrations required for satisfactory anesthesia. In 37 patients about to undergo lower abdominal gynecologic, upper abdominal, or breast surgery, anesthesia was induced with alfentanil 150 μg/kg iv and 66% N2O in oxygen. Thereafter, N2O anesthesia was supplemented with a continuous infusion of alfentanil that was varied between 25 and 150 μg · kg-1· h-1, as indicated by the patient's responses to surgical stimulation. Small bolus doses of alfentanil 7 or 14 μg/kg were administered and the infusion rate increased to suppress precisely defined somatic, autonomic, and hemodynamic responses. Arterial plasma concentrations of alfentanil were measured during the operation when the patient did and did not respond to noxious stimulation. Logistic regression was used to determine plasma concentration–effect curves for different stimuli. Plasma alfentanil concentrations required along with 66% N2O to obtund responses to single episodes of stimulation in 50% of the 37 patients (Cp50± SE) were: 475 ± 28 ng/ml for tracheal intubation, 279 ± 20 ng/ml for skin incision, and 150 ± 23 ng/ml for skin closure. Between skin incision and closure, multiple determinations of response/no response were made for each patient and an individual Cp50was estimated. The Cp50(mean ± SD) for the three surgical procedures were: breast, 270 ± 63 ng/ml (n = 12); lower abdominal, 309 ± 44 ng/ml (n = 14); and upper abdominal, 412 ± 135 ng/ml (n = 11). The Cp50for satisfactory spontaneous ventilation after the discontinuation of N2O was 223 ± 13 ng/ml. These data demonstrate that different perioperative stimuli require different alfentanil concentrations to suppress undesirable responses. Thus, the alfentanil infusion rate should be varied according to the patient's responsiveness to stimulation in order to maintain satisfactory anesthetic and operative conditions and to provide rapid recovery of consciousness and spontaneous ventilation.

ISSN:0003-3022    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

The hemodynamic response to 50% nitrous oxide was studied in 12 sedated but responsive infants in the intensive care unit following repair of their congenital heart disease. One-half of the infants studied had an elevated pulmonary vascular resistance index (PVRI > 3.5 Wood units). During mechanical ventilation with a fractional inspired O2concentration (FIO2) of 0.5, hemodynamic parameters were measured after equilibration with 50% nitrogen and then after 50% nitrous oxide. The sequence was repeated once to assure reproducibility of the responses. Average heart rate decreased by 9%, mean arterial blood pressure decreased by 12%, and cardiac index decreased by 13% in both the elevated and normal PVRI groups each time nitrous oxide was given. Although statistically significant, these changes would not generally be clinically important except in infants with severely compromised cardiovascular reserve. In contrast, pulmonary artery pressure and PVRI were not significantly changed by administration of 50% nitrous oxide in either the group with normal PVRI or the group with preexisting elevated PVRI. We conclude that while these mild depressant effects of nitrous oxide onsystemichemodynamics in infants are similar to those previously reported in adults, in infants nitrous oxide does not produce the elevations in pulmonary artery pressure and pulmonary vascular resistance seen in adults.

ISSN:0003-3022    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

Experimental factors implicated in the pathogenesis of halothane hepatotoxicity in the phenobarbital–hypoxia rat model were examined for direct effects on the energy status of isolated rat liver cellsin vitro. Intact hepatocytes were isolated after collagenase per-fusion of livers of adult male Fischer 344 rats previously treated with phenobarbital (0.1% in drinking water for 5–7 days) and/or deprived of food for 48 h. Cells were incubated in Krebs-Henseleit buffer + substrates for 10 min at steady states of energy metabolism, with extracellular PO2constant at 32, 16, or 4 mmHg ± 1% halothane. Fasting produced the largest energy deficits in incubated hepatocytes, regardless of phenobarbital treatment status, PO2value, or presence/absence of halothane. The combination of hypoxic PO2(4 mmHg) and 1% halothane shifted lactate metabolism toward lactate production, whereas hypoxia or halothane alone did not. Prior phenobarbital treatment plus hypoxia decreased adenosine triphosphate/adenosine diphosphate (ATP/ADP) and increased lactate production compared with drug treatment or hypoxia alone. We conclude that pathogenic factors that interact to produce halothane hepatotoxicity act directly and jointly on isolated liver cells to produce energy deficits within 10 min. Differences in the relative importance of pathogenic factorsin vitroandin vivosuggest that short-term, direct effects on hepatocellular energy status are not solely responsible for halothane hepatotoxicity.

ISSN:0003-3022    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

To assess the interaction between isoflurane and the new calcium channel blocker, nicardipine, mongrel dogs were chronically instrumented to allow the following measurements: aortic, left ventricular and left atrial pressures; heart rate; cardiac output; and carotid, coronary, and renal blood flows. The hemodynamic effects of intravenous nicardipine 5, 10, 30, and 50 μg/kg were measured in awake dogs and during 1.6 and 3.0 per cent (end-tidal) isoflurane anesthesia. Nicardipine induced a dose-dependent fall in mean arterial pressure in both awake dogs and during 1.6 and 3.0 per cent isoflurane anesthesia. Heart rate and cardiac output were increased in proportion to the nicardipine dose in the awake dogs and, to a lesser degree, in the dogs anesthetized with 1.6 per cent isoflurane, but did not change during 3.0 per cent isoflurane anesthesia. Left atrial pressure was unchanged by nicardipine in awake dogs and during anesthesia. Left ventricular maximum rate of tension development (dP/dt) increased in awake dogs and decreased during anesthesia. Coronary blood flow increased dose dependently without anesthesia, and, to a smaller degree, during anesthesia. Nicardipine increased carotid blood flow without anesthesia, whereas it was unchanged during anesthesia. Renal blood flow was unchanged in awake dogs and decreased during anesthesia. The authors conclude that nicardipine is a potent vasodilator that minimally affects cardiac function and regional blood flow in the presence of isoflurane. The interactions between nicardipine and isoflurane are mainly the result of the isoflurane-induced inhibition of the reflex tachycardia elicited by nicardipine.

ISSN:0003-3022    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

The authors compared the respiratory effects of an intravenous infusion of ketamine (1 mg · kg-1) with droperidol (0.1 mg · kg-1), or placebo on three different occasions in a double-blind, randomized fashion in eight healthy volunteers. Breathing pattern, thoraco–abdominal motion, end-expiratory positions of the rib cage and abdomen, arterial hemoglobin oxygen saturation (SaO2), and end-tidal carbon dioxide concentration (FECO2) were continuously measured with noninvasive techniques. During the 1-h monitoring period following drug injection, droperidol produced occasionally significant but clinically unimportant differences in respiratory variables when compared with placebo. In contrast, ketamine induced a significant (P< 0.001) and persistent increase in minute ventilation (+75%) from 5 to 20 min after start of infusion by increasing both the driving (i.e., tidal volume/inspiratory time [VT/T]) and the timing (i.e., in-spiratory time/total respiratory cycle time [T/T]) components of ventilation (Milic-Emili J, Grunstein MM: Chest 70 (Suppl): 131–133, 1976). This was obtained without any significant change in end-expiratory positions or change in relative rib cage contribution to tidal volume. Despite multiple apneic episodes observed with ketamine, the subjects maintained a stable SaO2and FECO2, indicating no resting respiratory depression. This study, performed with a noninvasive respiratory monitoring technique, confirms that droperidol infused over 5 min at a clinically used dosage does not cause respiratory depression in healthy subjects, whereas ketamine produces an important ventilatory stimulation.

ISSN:0003-3022    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

Continuous-flow apneic ventilation (CFAV) by endobronchial insufflation of conditioned gas was evaluated in dogs during thoracotomy. In Group 1 (n = 6), dogs were anesthetized with pentobarbital (25 mg/kg). An endobronchial catheter (2.5 mm ID) was introduced into each mainstem bronchus using a fiberoptic bronchoscope and held in place by an endotracheal tube. Before the onset of CFAV (total flow 1.0 1 · kg-1· min-1, the animals were paralyzed with pan-curonium bromide and muscle relaxation was monitored with a peripheral nerve stimulator. The CFAV delivery system consisted of a flow meter, air/oxygen blender, oxygen analyzer, heated humidifier, and ultrasonic spirometer. Blood gas values were measured after 30 min of spontaneous ventilation, and CFAV with: 1) closed chest, fractional inspired O2concentration (FIO2) 0.21; 2) open chest, FIO20.21; 3) open chest, FIO20.21, continuous positive airway pressure (CPAP) 5 mmHg; and 4) open chest FIO20.4, CPAP 5 mmHg. This last combination resulted in a mean PaO2of 113.1 ± 5.5 (SEM) mmHg and a PaCO2of 35.0 ± 2.1 (SEM) mmHg. In Group 2 (n = 6), animals with open chests were ventilated with CFAV (FIO20.4 and CPAP 5 mmHg) for 5 h. Adequate oxygenation and ventilation were achieved. PaCO2after 5 h of CFAV was 41.8 ± 1.9 (SEM) mmHg compared with 40.8 ± 1.9 (SEM) mmHg during spontaneous breathing. PaO2after 5 h of CFAV was 138.1 ± 11.7 (SEM) mmHg. There were no significant changes observed in vascular pressures. Significant differences in other hemodynamic parameters were probably due to pentobarbital anesthesia. Adequate gas exchange can be achieved during CFAV in dogs with open chests for 5 h.

ISSN:0003-3022    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

Administration ofd-tubocurarine (dTC) or diphenylhydantoin (DPH) was evaluated as a pretreatment to prevent succinylcholine (Sch) evoked fasciculations. Experiments were designed to determine the nature of the drug–drug interactions, sites of interaction, and site of fasciculation suppression. Sch is known to evoke repetitive discharge generation by motor nerve terminals (MNTs). Transmission of these prejunctional discharges causes fasciculations. A cat solcus neuromuscular preparationin situ, which enables recording of nerve action potentials initiated by MNTs, their transmitted muscle action potentials, and the resultant contractile responses, was used to explore Sch effects before and after iv pretreatment withdTC or DPH.dTC is known to act prejunctionally to suppress repetitive discharges initiated by facilitatory drugs and tetanic conditioning of MNTs. Accordingly, pretreatment withdTC 50 μg · kg-1suppressed the Sch-induced MNT repetitive discharging and correspondingly suppressed generalized fasciculations without affecting twitch. ThisdTC dose, however, also reduced Sch blocking potency by 33%, slowed its rate, and shortened block duration. These latter effects represent competitive postjunctional antagonism. DPH is also known to suppress MNT repetitive discharging. Correspondingly, Sch-induced repetitive firing and ensuing fasciculations were suppressed by DPH (30 mg · kg-1) without affecting twitch. UnlikedTC, this DPH dose increased Sch blocking potency by 50%, increased the initial rate of block, and did not alter block duration. These DPH effects were dose-dependent and within the anticon-vulsant range for cats. Therefore, patients with anticonvulsant levels of DPH may not require pretreatment before Sch. It is concluded that the effectiveness of a pretreatment regimen for prevention of Sch fasciculations depends on a prejunctional suppression of repetitive firing generated by MNTs. The cat solcus preparation serves as a clinically relevantin situmethod for evaluating prejunctional and postjunctional effects of drugs and should serve as a reliable test for other pretreatment candidates.

ISSN:0003-3022    

出版商:OVID    

年代:1986

数据来源: OVID