摘要:

The measurement of force of contraction of the adductor pollicis muscle following supramaximal stimulation of the ulnar nerve has become a standard method to assess the effect of neuromuscular blocking drugs. However, the diaphragm is regarded as resistant to these drugs, and considerable residual respiratory power might still be present after total block of adductor pollicis function. To quantify this differential effect, train-of-four stimulation was applied to the ulnar and the phrenic nerves in patients under N2O-halothane anesthesia. The force of contraction of the adductor pollicis muscle was measured with a force-displacement transducer and compared with the diaphragmatic electromyogram (EMG). Pancuronium cumulative dose-response curves for both muscles were determined in 10 ASA Class I adults. The mean dose (±SEM) required to depress adductor pollicis and diaphragm responses to first twitch stimulation (ED50) was 29.5 ± 3.5 μg/kg and 59.5 ± 7.0 μg/kg, respectively. Corresponding values for ED90were 45 ± 5 μg/kg and 95 ± 11 μg/kg, respectively, indicating that the diaphragm required approximately twice as much pancuronium as the adductor pollicis for an identical block. At 90% adductor pollicis block, the diaphragm was only 24 ± 4% blocked. It is concluded that the adductor pollicis response might underestimate the degree of diaphragmatic relaxation. On the other hand, the administration of pancuronium in a dose sufficient to produce total paralysis might result in the inability to antagonize neuromuscular block in all muscles.

ISSN:0003-3022    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

Atracurium, a nondepolarizing muscle relaxant, is eliminated through several pathways, including Hofmann elimination (spontaneous degradation in plasma and tissue at normal bodypH and temperature) and ester hydrolysis (catalysis by nonspecific esterases). Because elimination of atracurium occurs in both tissue and plasma, traditional pharmacokinetic models assuming elimination from a single central compartment are inaccurate for atracurium. The authors developed a two-compartment pharnacokinetic model in which hepatic and/or renal elimination occurs from the central compartment (Clorgan), and Hofmann elimination and ester hydrolysis occur from both central and peripheral compartments (Clnonorgan). To determine thein vitrorate constant for Hofmann elimination and ester hydrolysis, atracurium was added to whole blood kept at each patient'spH and temperature. The values for this rate constant ranged from 0.0193 to 0.0238 per min. When these values were applied to the pharmacokinetic model, Cltotal, Clorgan, and Clnonorganwere 4.8 ± 1.1, 3.0 ± 0.9, and 1.9 ± 0.6 ml.kg−1. min−1, respectively. The authors conclude that more than one-half of the clearance of atracurium occursviapathways other than Hofmann elimination and ester hydrolysis.

ISSN:0003-3022    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

The authors determined the effect of acute and chronic aminophylline treatment on the arrhythmogenicity of epinephrine during halothane anesthesia. The dose of epinephrine required to achieve an arrhythmia threshold (ADE) was determined in nine unpremeicated dogs anesthetized with halothane (1.5% v/v) in oxygen (A0). Aminophylline was then infused to achieve and sustain a therapeutic theophylline level (mean ± SD) of 17 ± 2 μg.m−1(A1), at which time the ADE was reassessed. The aminophylline infusion regimen was then adjusted to provide a supratherapeutic level of theophylline of 34 μg. m−1(A2) and the ADE was reassessed. In an additional seven dogs the ADE was assessed before and after 6 weeks of oral aminophylline treatment that yielded a plasma theophylline level of 18 ± 3 μg. ml−1. The ADE was significantly (P< 0.01) reduced from a basal value (mean ± SD) of 2.63 ± 0.97 μg. kg.−1min−1to 1.39 ± 0.47 in the A1state. There was no further decrement in the ADE at the A2state (1.17 ± 0.36). The plasma epinephrine level at the arrhythmia threshold decreased commensurately from 50.7 ± 40.2 ng.ml−1(A0) to 20.0 ± 7.9 and 19.2 ± 7.6 in the A1and A2states, respectively (P< 0.01). In contrast to these acute treatment experiments, neither the ADE (2.65 ± 0.95vs.2.97 ± 1.49 μg. kg−1. min−1) nor the plasma epinephrine levels at the arrhythmia threshold (47.2 ± 13.7vs.51.1 ± 22.0 ng. ml−1) were different after chronic aminophylline treatment. It is concluded that an important arrhythmia-enhancing effect is induced by a clinically relevant dose of acute intravenous aminophylline administration in a canine halothane-epinephrine arrhythmia model. However, this effect is reversed following chronic aminophylline treatment. The authors speculate that, in the acute state, the antiadenosine action of aminophylline potentiates the halothane-epinephrine arrhythmia interaction and that compensatory mechanisms normalize this effect following chronic aminophylline administration.

ISSN:0003-3022    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

To determine the effect of aging on the pharmacokinetics and pharmacodynamics of etomidate, we administered etomidate (5 to 10 mg/min) by intravenous infusion to 21 healthy surgical patients, age 22 to 82 yr. Etomidate produced progressive slowing of the EEG to an easily recognized pattern (stage 3) that determined the dosage endpoint. Subsequent power-spectrum analysis of the EEG gave the median frequency. Median frequency values and simultaneous measurements of blood etomidate concentration were incorporated into a sigmoid Emaxpharmacodynamic model that permitted an estimate of IC50, the blood etomidate concentration which produced a 50% reduction in the median frequency. The dose of etomidate required to reach the uniform EEG endpoint decreased significantly with increasing age (r2= .68) as did the dose needed to produce maximal median frequency depression (r2= .69). None of the parameters of the pharmacodynamic effect model, including IC50, correlated with age, suggesting that increased brain sensitivity in the elderly does not cause the age-related change in dose requirement. The initial distribution volume for etomidate decreased significantly with increasing age (r = .56), implying that a higher initial blood concentration in the elderly following any given dose of etomidate is part of the cause of the lower dose requirement in the elderly patient. A contracted initial distribution volume in the elderly may result from well described physiologic changes of age. Etomidate clearance also decreased with age. Age-dependent changes in etomidate pharmacokinetics rather than altered brain responsiveness may be the basis for the decreased etomidate dose requirement in the elderly.

ISSN:0003-3022    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

This study was designed to determine the nephrotoxic potential of prolonged anesthesia with enflnrane or isoflurane in obese and nonobese Fischer 344 rats. Weight-paired rats received either a regular chow diet or Potter's high fat diet for 16 weeks. The chow-fed (nonobese) rats gained 20% in body weight compared with 45% for the Potter's-fed (obese) rats. Exposure of nine pairs of rats to 2.0% enflurane for 4 h resulted in significantly elevated peak serum F levels (62 ± 11 μMvs.27 ± 6 μM;P< 0.001) in obese compared with nonobese rats and clinical signs of F−-induced nephrotoxicity (i.e., polyuria) confirmed by decreased creatinine and urea nitrogen clearances in the obese rats. Exposure of nine pairs of rats to 1.4% isoflurane for 4 h produced significantly elevated peak serum F−levels (27 ± 8 μMvs.9 ± 0.4 μM;P< 0.001) in obese compared with nonobese rats and subclinical nephrotoxicity in obese rats manifested by significantly decreased creatinine and urea nitrogen clearances, but without polyuria. This study suggests that obese patients may be at risk of developing F−-induced nephrotoxicity following prolonged enflurane anesthesia. Isoflurane may have significant potential for subclinical F−-induced nephrotoxicity in obese patients, to a degree that might affect renal clearance of some drugs in the postoperative period.

ISSN:0003-3022    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

Median nerve somatosensory evoked potentiais (SSEPs) were recorded in 21 healthy subjects anesthetized with halothane, isoflurane, or enflurance (with and without nitrous oxide) for abdominal or pelvic surgery. Recordings were made prior to induction, then at 0.5 MAC increaments of each valatile agent with 60% N2O up to 1.5 MAC, and, finally, at 1.5 MAC without N2O. All three volatile anesthetics produced dose-related reductions in the amplitude and increases in the latency of he cortical component of hte SSEP. These changes were most pronounced with enflurance nad least with halothane. At 1.5 MAC of each volatile agent, cortical latency decrease and amplutede increased when nitrous oxide was discontinued. The results suggests that in neurologically intact patients, end-tidal concentrations of 1. MAC halothane and 0.5 MAC enflurance or isoflurance (each in 60% N2O) can be compatible with effective with effective SSEP monitoring. Volatile anesthetic concentrations consistent with satisfactory somatosensory-evoked potential recording may be grater if N2O is not employed.

ISSN:0003-3022    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

Doses of sufentanil (i.e., 0.01, 0.04, 0.16, 0.63, 2.5, 10, and 40 μg/rat) were injected either into the lumbar epidural space or intravenously in rats weighing ± 250 g, andin vivopharmacologic activities (i.e., prolongation of latency to tail withdrawal in response to noxious heat, blockade of cornea and pinna reflexes, increase of skeletal muscle tone),ex vivoμ-opiate receptor binding (i.e., displacement of specific3H-sufentanil binding in thalamus, striatum, hippocampus, cortex, mamillary body-medulla oblongata segment, medulla oblongata, and in cervical, thoracic, and lumbar spinal cord), and drug concentrations in plasma, brain, cortex, and cerebellum, were determined. An ED50dose of intravenous sufentanil of 0.075 μg/rat produced analgesia. CNS-mediatedin vivoside effects (i.e., blockade of pinna and cornea reflexes, muscle rigidity) were apparent at 6–28 times higher doses. Epidural sufentanil also produced analgesia at an ED50dose of 0.08 μg/rat, but CNS-mediated side effects occurred only at 35 to 76 times higher doses. This greaterin vivoselectivity of epidural sufentanil in producing analgesia was consistent withex vivobinding data that showed that in most areas of brain, but not in spinal cord, more μ-opiate binding occurs with intravenous than with epidural sufentanil. The two routes nonetheless differed by no more than a factor of approximately two in producing detectable levels of sufentanil both in plasma and in brain tissue. Analgesia produced by epidural sufentanil in rats may originate at least in part at μ-opiate receptor sites in the spinal cord; but the minute amounts of sufentanil that may reach the brain after epidural injection of low doses of the drug may perhaps amplify the spinal action.

ISSN:0003-3022    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

Using the radiolabeled microsphere technique, the authors studied hemodynamic variables and regional blood flow to multiple peripheral organs during conventional positive-pressure ventilation (CV) and high-frequency ventilation (HFV) at low and high mean airway pressure (Paw). Twenty supine anesthetized, paralyzed dogs were ventilated using CV (14–16 breaths/min) and HFV (rate = 10 Hz) in random order. In the first group (low Pawn = 10), Pawwas maintained at 3 cmH2O during CV and HFV. In the second group (high Paw, n = 10), Pawwas increased to 13 cmH2O during CV and HFV. Pulmonary capillary wedge pressure and right atrial pressure remained constant during low and high Pawtrials. No differences in heart rate, systemic arterial pressure, intracranial pressure, or cardiac output were noted during CV and HFV within the low and high Pawgroups. In addition, blood flow to multiple peripheral organs during CV and HFV remained constant within each Pawgroup, except for a small decrease in cerebellar blood flow during HFV at high Paw. Comparison of hemodynamic measurements during high and low Pawtrials showed a significant decrease in hepatic arterial and outer kidney cortical flow at high Paw. Total cerebral blood flow was decreased at high Paw, as were regional flows to diencephalon, midbrain, pons, medulla, and cerebellum. However, these differences were not attributable to differences in cerebral perfusion pressure or intracranial pressure, and cerebral oxygen delivery was not different between high Pawand low Pawgroups. It is concluded that under conditions of similar Pawin anesthetized dogs, HFV does not significantly alter hemodynamic patterns or regional circulation relative to CV.

ISSN:0003-3022    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

The authors determined the pharmacokinetics (including transfer ito cerebrospinal fluid [CSF]) and the cardiovascular and central nervous system (CNS) effects of laudanosine, a metabolite of atracurium. Eight dogs were anesthetized with halothane; blood pressure and a fronto-occipital electroencephalographic lead were monitored. Laudanosine (1 mg. kg−1iv) was administered as a bolus, and its concentrations in plasma, CSF, urine, and bile were determined by liquid chromatography. Three-compartment modeling of plasma audanosine concentrations yielded an elimination half-life for laudanosine of 113 ± 24 min (mean ± SD) and a clearance of 25 ± 8 ml. kg−1. min−1. CSF concentrations of laudanosine were highest 5–10 min after iv injection of laudanosine and ranged in concentration from 208 to 572 ng. ml−1(i.e., 36–87% of the corresponding plasma concentrations). Unchanged laudanosine was found in urine (0.5− 12% of injected dose) and bile (o2= 0.2) to a Paco2of 26–28 mmHg. Laudanosine was then administered 2 mg. kg−1iv every 5 min. With cumulative doses of 2–8 mg. kg−1, all dogs showed signs of “awakening” from anesthesia. Cumulative doses of 14–22 mg. kg−1produced seizure activity in all animals. Mean arterial blood pressure decreased significantly to 86% of control levels at 1 min following administration of laudanosine (1 mg. kg−1iv) and returned to control levels 4 min later. The authors conclude that laudanosine in dogs readily crosses the blood-brain barrier and can produce hypotension, signs of “awakening” from halothane anesthesia, and seizures. In addition, laudanosine is excreted unchanged by the kidney, and its metabolites are excreted by both the kidney and liver.

ISSN:0003-3022    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

The hemodynamic and electrophysiologic effects of bupivacaine, etidocaine, mepivacaine, and lidocaine were investigated in 32 pentobarbital-anesthetized adult mongrel dogs. Following equipotent dosing, all four agents produced similar hemodynamic effects: decrease in stroke volume and cardiac output, heart rate slowing, increase in systemic vascular resistance, and increases in pulmonary arterial pressure (PAP) and pulmonary capillary wedge pressure (PCWP). The effects of the various agents on the ECG were different. Compared with the control period, mepivacaine and lidocaine produced slight increases and etidocaine and bupivacaine much greater increases in: 1) the area under the curve of the T-wave; 2) lengthening of the QTU interval; and 3) enhancement of the “slow wave” or U-wave following the T-wave. The effects of the various agents or effective refractory period (ERP) temporal dispersion were dramatically different. The ERP temporal dispersion increased to 48.3 ± 36.0 ms following mepivacaine, 37.4 ± 10.1 ms following lidocaine, 97.1 ± 36.2 ms following bupivacaine, and 92.5 ± 30.5 ms following etidocaine. Six of seven bupivacaine, six of seven etidocaine, two of eight mepivacaine, and none of eight lidocaine animals sustained a polymorphic, undulating ventricular tachycardia similar to Torsades de Pointes following burst ventricular pacing. The results of this study suggest that bupivacaine, etidocaine, and occasionally mepivacaine can result in a Torsades de Pointes-like syndrome following intravenous administration. The magnitude of ERP temporal dispersion differences between the various agents appears to explain their differential arrthymogenicity.

ISSN:0003-3022    

出版商:OVID    

年代:1986

数据来源: OVID