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:

Fourteen patients with normal, global, left ventricular function scheduled for elective myocardial revascularization were studied at rest and during atrial pacing before and during isoflurane anesthesia (0.5% end-tidal) plus 50% nitrous oxide. Rapid atrial pacing was performed in a stepwise fashion until the onset of angina pectoris in the awake patients. The same step increase in pacing rate was applied in the anesthetized patients. Compared with prepacing baseline values, isoflurane significantly decreased systemic blood pressure, coronary perfusion pressure, the rate-pressure product, and cardiac index. No patient had ST-segment depression while awake or during isoflurane anesthesia before pacing was started. Prepacing left and right ventricular filling pressures and wave forms were normal, both while awake and during isoflurane anesthesia. The mean pacing rate at which first signs of myocardial ischemia appeared (V5ST-segment depression ≥0.1 mV, increase in pulmonary capillary wedge pressure (PCWP) to ≥15 mmHg, and prominent PCWP v-waves ≥20 mmHg) was significantly higher during isoflurane anesthesia than in the awake patients (128 ±vs. 115 ± 5 beats/min). With the exception of one patient, the individual pacing rates inducing first signs of ischemia in the awake patients were below the anginal threshold. None of the patients had a reduced ischemic threshold during anesthesia. Eleven anesthetized patients tolerated a higher pacing rate until initial signs of ischemia appeared. In four of these patients, the pacing rate required to induce first signs of ischemia was above the heart rate at which chest pain had been induced while they were awake. At a peak atrial pacing rate of 129 ‡ 5 beats/min, which had induced angina pectoris in the awake patients, the increase in PCWP was significantly smaller during pacing with isoflurane than during control pacing. Prominent PCWP v-waves (>20 mmHg) appeared in 12 of the 14 patients during initial pacing to angina and in eight patients paced during isoflurane anesthesia. In six of these eight patients, the abnormal v-waves were less prominent than those observed during control pacing. Ischemic ST-segment changes developed in 13 of 14 patients during initial pacing and in nine patients during pacing with isoflurane. Mean V5ST-segment depression during the two pacing periods was significantly different, averaging 0.19 and 0.11 m V, respectively. The authors conclude that a low concentration of isoflurane plus nitrous oxide improves the tolerance to pacing-induced myocardial ischemia in patients with significant coronary artery disease.

ISSN:0003-3022    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

Qualitative distribution of coronary flow using thallium-201 perfusion scans immediately postintubation was studied in 22 patients scheduled for elective coronary artery bypass surgery. Ten patients received a thiopental (4 mg/kg) and halothane induction. Twelve patients received a fentanyl (100 μg/kg) induction. Baseline thallium-201 perfusion scans were performed 24 h prior to surgery. These scans were compared with the scans performed postintubation. A thallium-positive scan was accepted as evidence of relative hypo-perfusion. Baseline hemodynamic and ECG data were obtained prior to induction of anesthesia. These data were compared with the data obtained postintubation. Ten patients developed postintubation thallium-perfusion scan defects (thallium-positive scan), even though there was no statistical difference between their baseline hemodynamics and hemodynamics at the time of intubation. There was no difference in the incidence of thallium-positive scans between those patients anesthetized by fentanyl and those patients anesthetized with thiopental-halothane. The authors conclude that relative hypoperfusion, and possibly ischemia, occurred in 45% of patients studied, despite stable hemodynamics, and that the incidence of these events was the same with two different anesthetic techniques.

ISSN:0003-3022    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

The authors prospectively investigated the ability of thiopental to decrease neuropsychiatric complications as a consequence of openventricle operations requiring cardiopulmonary bypass. Eighty-nine randomly assigned patients received sufficient thiopental to maintain electroencephalographic silence throughout the period from before atrial cannulation to termination of bypass. These patients received an average of 39.5 mg/kg of thiopental, while 93 control patients received only fentanyl. On the first postoperative day, five thiopental (5.6%) and eight control (8.6%) patients exhibited clinical neuro-psychiatric abnormalities. By the tenth postoperative day, all neuropsychiatric dysfunction had resolved in the thiopental group but persisted in seven (7.5%) control patients (P< 0.025). The incidence of complications was significantly related to calcification of replaced valves, aortic valve replacement, advanced age, and prolonged bypass, but not to low blood pressure during perfusion. The authors believe their data are consistent with embolism as the most important cause of sensory-motor neurologic dysfunction following cardiopulmonary bypass. The data also provide evidence that thiopental in sufficient dosage can reduce the clinical consequences of these events. This is the first demonstration of cerebral protection by a barbiturate in humans.

ISSN:0003-3022    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

Atracurium infusion requirements were determined in 28 children anesthetized with N2O2, narcotic, N2O2halothane (1% inspired), and N2O:O2enflurane (2% inspired). When the patient was recovering from a bolus dose of 0.4 mg/kg atracurium, a continuous infusion of atracurium was started and the rate was adjusted to maintain 90–99% muscle twitch depression. Patients receiving enflurane anesthesia required atracurium at an infusion rate of 4.9 ‡ 0.3 μg. kg−1. min−1which was a significantly lower rate (P= 0.0001) than those anesthetized with halothane (8.3 ‡ 0.4 μg.kg−1· min−1) or with N2O:O2and narcotic (9.3 ‡ 0.5μg.kg−1· min−1). At the onset of neuromuscular blockade, the twitch response disappeared faster after train-of-four stimulation repeated every 10 s than after single twitch rates of stimulation at 0.1 Hz. In children, during halothane anesthesia after 0.4 mg/kg atracurium, the response of the adductor of the thumb was ablated in 2.0 ‡ 0.3 min with train-of-four stimulation, and in 3.7 ‡ 0.4 min with single twitch stimulation. The authors recommend the use of a nerve stimulator during continuous infusion of atracurium because of the marked interpatient differences in infusion-rate requirements.

ISSN:0003-3022    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

To identify the opioid antagonist activity of nalmefene and to determine its duration in man, six healthy male subjects were pretreated on separate days with a saline placebo, 0.5 mg, 1 mg, or 2 mg nalmefene intravenously in a randomized double-blind fashion. Opioid challenges with fentanyl, 2 μg/kg, then were administered 1,2,4,6, and 8 h afterward. Respiratory depression was monitored by ventilatory and occlusion pressure responses during CO2re-breathing, while analgesia to experimental pain was identified with the submaximal effort tourniquet ischemia test. One hour following placebo pretreatment, the initial fentanyl dose produced marked respiratory depression. Minute ventilation and occlusion pressure at a PCO260 mmHg during rebreathing (VE60 and P0.160) were reduced to 29 and 41% of control, respectively. The slopes of the ventilatory and occlusion pressure responses also decreased significantly to 51 and 55% of control. Respiratory effects were similar with all subsequent fentanyl doses. Pretreatment with 2 mg nalmefene completely prevented the subjective and respiratory effects of fentanyl for the entire 8 h of the experiment. Nalmefene, 1 mg, significantly blunted the fentanyl effects for the same period, but VE60 values at 6 and 8 h were depressed significantly (P< 0.05) to 66 and 61% of control. The antagonist effects of the lowest nalmefene dose, 0.5 mg, persisted for about 4 h, at which time V E60 was 64% of control. Fentanyl administration produced consistent increases in pain tolerance (44–55% above control) throughout the experiment. Nalmefene pretreatment abolished this analgesic response in a dose-related time course that mirrored the respiratory effects almost exactly. These findings demonstrate that nalmefene is an effective opioid antagonist with a duration of action far in excess of naloxone and more clearly related to dose.

ISSN:0003-3022    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

The mechanism underlying the decrease in minute ventilation (VE) observed under halothane anesthesia was investigated in nine spontaneously breathing dogs. Anesthesia was induced with pentobarbital sodium and was maintained with halothane. Inspired fraction of halothane (F1hal) was increased every 30 min, from 0.005 to 0.02. VEdecreased from 8.1 ± 0.9 to 4.8 ± 0.41 min−1(P< 0.001), as F1hal increased from 0 to 0.02. This resulted from a decrease in both mean inspiratory flow (VT/T1) and the duty ratio (T1/TTOT). Transdiaphragmatic pressure (Pdi) and the integrated electrical activity of both hemidiaphragms (Edi) were measured during normal breathing, and during breathing against closed airways (P0di, E0di), in order to obtain an index of the inspiratory neuromuscular output of the diaphragm. With increasing F1hal, there was a significant decrease in Pdi, P0di, Edi, and E0di. The authors measured Pdi and Edi generated during supramaximal stimulation of the two phrenic nerves (P5di, E5di) at frequencies of 10,20,50, and 100 Hz, in order to eliminate in this decrease the role played by a decrease in the neural drive to breathing. P5di and E5di decreased significantly with increasing F1hal, and had not returned to the control values 30 min after discontinuation of halothane administration. The authors conclude that, in pentobarbital-anesthetized dogs, halothane is responsible for a diaphragmatic dysfunction, which may be located either at the neuromuscular junction, on the contractile processes of the muscle, or on both, and for a decrease in the activation time of the inspiratory muscles. Both of these effects contribute to the decrease in VEobserved under halothane anesthesia.

ISSN:0003-3022    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

The role of variation of venous return on baroreflex control of heart rate during lumbar epidural anesthesia was investigated in 12 unpremedicated patients. Group 1 patients (n = 6) received 8 ml of 0.5% plain bupivacaine in the epidural space (L3–4) (mean upper level of analgesia at T10). Group 2 patients (n = 6) received 8 ml of saline at the same level in the epidural space. Following the epidural injection, phenylephrine (PHE) and nitroglycerin (NTG) were employed to alter the stimulation of baroreceptor sites before and during application of lower body positive pressure (LBPP). Plasma bupivacaine, catecholamines, renin activity, and vasopressin were assayed. In contrast to saline, epidural bupivacaine induced a decrease in systolic arterial and right atrial pressures (−11 ‡ 4 and −3.2 ‡ 0.7 mmHg, respectively, mean ‡ SEM) without change in heart rate, an increase in baroreflex slopes during PHE and NTG injections (+5.9 ‡ 1.6 ms/mmHg and +2.8 ‡ 0.9 ms/mmHg, respectively), and a decrease in plasma norepinephrine (−248 ‡ 89 pg/ml). The application of LBPP restored hemodynamic and reflex variables to preepidural analgesia values, whereas plasma catecholamines decreased further. Plasma renin activity and vasopressin were not modified at any time in either groups. This study indicates that lumbar epidural anesthesia enhances cardiac vagal tone mainly through a decrease in venous return.

ISSN:0003-3022    

出版商:OVID    

年代:1986

数据来源: OVID