ISSN:0003-3022    

出版商:OVID    

年代:1983

数据来源: OVID

摘要:

Using intraoperative electrophysiologic studies (ES), the authors analyzed the effects of various supplemental intravenous anesthetic agents on the antegrade and retrograde effective refractory period of accessory pathways (AERPAP and RERPAP) in the Wolff-Parkinson-White syndrome (WPWS), as well as their possible clinical implications. Serial evaluations were performed in 18 patients scheduled for surgical section of accessory pathways (AP) after anesthetic induction (thiopental + pancuronium + N2O + fentanyl, 30 μg/kg), infusion of additional fentanyl (up to 50 μg/kg), diazepam (250 μg/kg), and successive doses of droperidol (200 μg/kg up to a total of 600 μg/kg). Neither the induction agents nor the addition of diazepam or fentanyl had a modifying effect on the refractory period of the accessory pathway, whereas droperidol significantly (P< 0.001) increased the AERPAP from 226 ± 8 ms to 352 ± 15 ms with a significant dose-effect correlation. The RERPAP also increased significantly (P< 0.001) from 220 ± 8 to 324 ± 9 ms. These results show that both the antegrade and retrograde refractory period of the AP increased with droperidol. Thus, droperidol may prevent the typical arrhythmias of the WPWS: rapid ventricular response due to antegrade conduction over the AP and reciprocal supraventricular tachycardia due to retrograde conduction over the AP. The authors' clinical data support these findings. They concluded that there is a rational indication for the use of droperidol in the anesthetic management of the WPWS.

ISSN:0003-3022    

出版商:OVID    

年代:1983

数据来源: OVID

摘要:

The present experiments were carried out to study the influence of halothane, enflurane, and isoflurane on the electrophysiologic properties of single sinoatrial (SA) node cells of the guinea pig. The authors used the isolated, spontaneously beating guinea pig SA node superfused with modified Krebs' solution. These anesthetics were studied for their effects on spontaneous rate of discharge of the SA node cell, action potential amplitude, phase 4 dV/dt, phase 0 dV/dt, action potential duration, overshoot, maximum diastolic potential, and threshold potential. In addition, they have studied the interaction of increased extracellular calcium ion concentration with halothane, enflurane, and isoflurane (1 and 2 MAC). Anesthetic concentrations in the superfusing bath were measured using a gas chromatography procedure. Introduction of these anesthetics (1 and 2 MAC) for five minutes produced a significant decrease in the heart rate, decrease in the slope of the phase 4 and phase 0, and a decrease in the action potential duration. At concentrations of 2 MAC, these anesthetics produced a significant decrease in the action potential amplitude and its overshoot. There was no change in the threshold potential, and the maximum diastolic potential was decreased only with 2 MAC halothane. Increasing the extracellular calcium concentration counteracted the negative chronotropic effects of halothane, enflurane, and isoflurane. Addition of the calcium channel blocker, verapamil, potentiated the negative chronotropic effect of halothane. In the present study, a comparison of these anesthetics at equipotent anesthetic doses, indicated that their interaction with calcium does not appear to be competitive and calcium did not completely overcome the direct negative chronotropic effect of these potent anesthetics.

ISSN:0003-3022    

出版商:OVID    

年代:1983

数据来源: OVID

摘要:

Plasma levels of epinephrine which correspond to the arrhythmogenic doses were determined during halothane, enflurane, and pentobarbital anesthesia in the dog. The arrhythmogenic dose was established by a series of 3-min infusion of epinephrine at 10-min intervals. The mean values of the arrhythmogenic doses and the corresponding plasma levels of epinephrine were: 2.18 μg·kg-1·min-1and 38.7 ng/ml during halothane; 11.43 μg·kg-1·min-1and 206.3 ng/ml during enflurane; and 15.27 μg·kg-1·min-1and 296.5 ng/ml during pentobarbital anesthesia. The arrhythmogenic plasma levels of norepinephrine during halothane anesthesia was nearly the same as that of epinephrine.

ISSN:0003-3022    

出版商:OVID    

年代:1983

数据来源: OVID

摘要:

The possibility that antihypertensive therapy in spontaneously hypertensive rats (SHR) will reverse the shift in cerebral autoregulation and improve cerebrovascular performance during sodium-nitroprusside-induced hypotension was tested. Four-month-old SHR and Wistar Kyoto controls (WKY) were tested using four groups. One group each of SHR and WKY received 10 weeks of antihypertensive drug treatment using vasodilators combined with a betaadrenergic blocker, propranolol. A third and fourth group of SHR and WKY, respectively, received 10 weeks of sham treatment (n = 15 rats per group). Systolic pressure was measured weekly by tail cuff occlusion. Antihypertensive drug treatment significantly decreased blood pressure in SHR and WKY over the 10-week treatment period. At the end of 10 weeks, cerebral blood flow (CBF) was measured under control conditions (ketamine anesthesia plus hexamethonium pretreatment) and during SNP-induced hypotension to mean pressure levels of 82–92 mmHg and 54–58 mmHg. CBF was measured with radioactive microspheres and cerebral oxygen consumption (CMRO2) was calculated as the product of CBF and arterial-sagittal sinus blood oxygen content difference. Antihypertensive therapy did not significantly alter CBF in SHR or WKY, measured under control conditions, compared with sham-treated controls. Decreasing blood pressure to 82–92 mmHg produced a 49% decrease in CBF in sham-treated SHR (P< 0.05) but no significant change in CBF in sham- or antihypertensive-treated WKY or antihypertensive-treated SHR. At a mean blood pressure level of 54–58 mmHg, CBF decreased significantly in all SHR and WKY test groups, and decreased significantly more in sham- (69%) than in antihypertensive-treated SHR (49%,P< 0.05). These results indicate that long-term antihypertensive therapy may reverse the shift in cerebral autoregulation produced by chronic hypertension.

ISSN:0003-3022    

出版商:OVID    

年代:1983

数据来源: OVID

摘要:

The clinical pharmacology of BW A444U, a nondepolarizing ester relaxant, was evaluated in 56 consenting ASA class I subjects under nitrous oxide/oxygen-fentanyl-thiopental anesthesia. Using repetitive train-of-four stimulation, the ED95for inhibition of the first twitch in the train (T1) was 0.11 mg/kg. At 0.12 mg/kg, 97% inhibition of T1developed within 4.6 ± 0.6 (SE) min from injection; recovery of T1to 95% of the control height occurred within 52.3 ± 3.1 min. In a comparative group of subjects given 0.5 mg/kgd-tubocurarine, onset and depth of block were not significantly different, but the duration of recovery of T1to 75% of control was at least three times longer (P< 0.001). The duration of BW A444U-induced block therefore may be classified as intermediate betweend-tubocurarine and succinylcholine. There was little cumulative effect, since 5 ± 25 and 25 ± 75% recovery times did not vary significantly on either repetitive or increasing dosage. These properties may be explained at least in part by the finding that BW A444U is hydrolyzed relatively slowlyin vitroby human plasma cholinesterase, at 5.4% the rate of succinylcholine. Consistent with these observations, at the ED100(0.2 mg/kg) there was a significant inverse linear correlation between the duration of block and plasma cholinesterase activity. Neuromuscular block by BW A444U was antagonized readily by neostigmine.No changes in arterial pressure or heart rate were noted at up to 0.12 mg/kg (97% block). At higher dosages (0.16–0.20 mg/kg), brief (2 to 5 min), moderate decreases in mean arterial pressure, slight increases in heart rate, and facial erythema were observed occasionally. These changes correlated well with small increases in serum histamine.The human neuromuscular pharmacology of BW A444U suggests that nondepolarizing relaxants of intermediate duration of action may be produced from ester materials slowly hydrolyzed by plasma cholinesterase, and that BW A444U may have certain clinical pharmacologic advantages over current nondepolarizing relaxants.

ISSN:0003-3022    

出版商:OVID    

年代:1983

数据来源: OVID

摘要:

The systemic toxicity of etidocaine was compared in adult, newborn, and fetal sheep during continuous infusion of the drug into the jugular vein at the rate of 0.5 mg·kg-1·min-1. All recipients exhibited symptoms of toxicity in the following order: convulsions, hypotension, respiratory arrest, and circulatory collapse. The dose of etidocaine required to produce CNS and cardiovascular toxicity was significantly different among the three age groups, being the highest in the fetus and the lowest in the adult. In contrast, no significant difference in etidocaine blood concentrations at the onset of each toxic symptom was observed among the groups except that convulsions and hypotension occurred at lower blood levels in the fetus as compared with the newborn and adult. Comparisons of etidocaine blood concentrations associated with the onset of convulsions and circulatory collapse (CC/CNS ratio) with those of lidocaine reported previously indicate that a narrower margin exists in adults and newborn following administration of etidocaine.

ISSN:0003-3022    

出版商:OVID    

年代:1983

数据来源: OVID

摘要:

Since the cellular defect of malignant hyperthermia (MH) may occur in tissues other than muscle and since platelets share certain contractile characteristics with muscle cells, testing platelets has been suggested as a way to diagnose susceptibility to MH. In analogy to thein vitrodepletion of muscle adenosine triphosphate (ATP), the authors compared platelet basal nucleotide levels and halothane-induced depletion of ATP from 10 MH-susceptible patients and from 12 unrelated nonsusceptible controls. A rapid and simple isocratic high-pressure liquid chromatography technique was used to analyze acid-extracted platelet nucleotides. Halothane added to platelet-rich plasma at 37°C significantly decreased ATP in platelets in a dose-dependent as well as a time-dependent manner. In contrast, adenosine diphosphate (ADP) and adenosine monophosphate (AMP) were not changed significantly. Other volatile anesthetic agents also depleted ATP in platelets. Although ATP in platelets exposed to halothane was depleted significantly, there was no difference between platelets from MH-susceptible patients and non-susceptible controls. Therefore, halothane-induced ATP depletion in platelets is not a reliable test for diagnosing MH susceptibility.

ISSN:0003-3022    

出版商:OVID    

年代:1983

数据来源: OVID

摘要:

Differential ventilation of lungs has been employed in cases of respiratory failure. However, little is known regarding the basic physiologic effects of alternating lung ventilation. The authors therefore examined the changes which occur in cardiopulmonary functions when one lung is ventilated 180 degrees out of phase with the other.Twenty-two dogs were studied. Changing from synchronous to alternating ventilation caused a marked decrease in airway pressure and a large increase in total (lung-thorax) compliance. Left mean airway pressure decreased from 6.3 to 4.2 mmHg (-33%) and the right from 5.1 to 2.8 mmHg (-45%). Left mean total compliance increased from 11 to 17 ml/cmH2O (+55%) and the right from 13 to 27 ml/cmH2O (+108%). By comparison to the large changes in the values for lung mechanics, only minor changes in circulatory function were observed.It is conceivable that alternating lung ventilation would be beneficial in patients with marked unilateral lung damage in whom it may be desirable to reduce ventilation dependence on chest wall expansion and diaphragm movement.

ISSN:0003-3022    

出版商:OVID    

年代:1983

数据来源: OVID

摘要:

The authors studied the pharmacodynamics of four nondepolarising relaxants,d-tubocurarine (dTC), pancuronium, metocurine, and gallamine, at 25°C, 31°C, and 37°C. The rat phrenic nervehemidiaphragm preparation with vascular perfusion was used for these investigations. For each drug at each temperature, a dose-response curve for twitch depression was constructed. ED50values were calculated using probit-log dose regression.dTC, metocurine, and gallamine each demonstrated a near twofold increase in ED50at 25°C compared with 37°C. No such relationship was apparent with pancuronium. In addition, the slopes of the dose-response curves were analyzed for effects due to temperature or drug. Slopes were not influenced by temperature; however, the slopes for metocurine anddTC were lower than those for pancuronium and gallamine. The authors conclude that in the rat, pancuronium retains potency at hypothermia, whereas the other relaxants decrease potency. In addition, metocurine anddTC exhibit less steep dose-response curves under these experimental conditions.

ISSN:0003-3022    

出版商:OVID    

年代:1983

数据来源: OVID