摘要:

Deliberate hypotension was induced with isofiurane (mean inspired concentration 2.3 ± 1.0%) in 12 patients undergoing craniotomy for clipping of cerebral aneurysms. Global cerebral blood flow (CBF) was measured before, during, and after hypotension. Arterio-venous O2content difference was measured concomitantly, and the cerebral metabolic rate for oxygen (CMRO1)was calculated from these data. Mean arterial pressure (MAP) was reduced from 78 ± 5 mmHg to 51 ± 7 mmHg and then returned to 82 ± 8 mmHg. Mean CBF before hypotension was 49 ± 14 ml·100 g−1-min−1and was unchanged during (45 ± 12 ml · 100 g−1· min−1) and after (49 ± 15 ml. 100 g−1· min−1) hypotension. The CMRO1before hypotension was 2.0 ± 0.6 ml · 100 g−1· min−1. This was statistically significantly (P < 0.025) reduced to 1.5 ± 0.5 ml · 100 g−1· min−1during hypotension and then returned to 2.2 ± 0.6 ml. 100 g−1· min−1on return to normotension. This indicates that the global cerebral O2supply-demand balance was favorably influenced by isoflurane. No complications could be attributed to the hypotensive technique. We conclude that, with regard to global cerebral oxygenation, isoflurane is a safe agent with which to induce hypotension during neurosurgery.

ISSN:0003-3022    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

Clinical observation by the authors suggests that small changes in PaCO2cause significant alterations in pulmonary hemodynamics after cardiac surgery. To examine this, the authors induced moderate ventilatory hypocarbia (Paco2= 30.7 ± 0.4 mmHg, mean ± SD) in eight patients early after coronary artery bypass surgery. Normo-carbia (40.6 ± 0.5 mmHg) and hypercarbia (51.5 ± 0.5 mmHg) were then induced by adding CO1to the inspired gas. Standard hemo-dynamic measurements were performed at each stage. In four of the patients, CO1exposure was subsequently withdrawn in reversed order. There were no clinically significant changes in systemic hemodynamics. Despite unchanged pulmonary blood flow, in all patients pulmonary artery pressure increased with increasing PaCO2An almost two-fold and three-fold increase was observed in the mean pulmonary vascular resistance (PVR) and pulmonary diastolic gradient (pulmonary artery diastolic pressure-pulmonary capillary wedge pressure), respectively, when PaCO2was changed from hypocarbia to hypercarbia. The changes in the pulmonary diastolic gradient correlated (r = 0.77, p < 0.001) with the changes in the PVR. The pulmonary vasoconstrictor response was reversible with CO2washout. Avoidance of even moderate hypercarbia, therefore, seems advisable in the early postperfusion stage because of a further potential impedance to right ventricular ejection. Frequent measurement of pulmonary diastolic pressure gradient provides a useful method of rapid estimation of the resistance to flow in the pulmonary vascular bed.

ISSN:0003-3022    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

The effects of intravenous lidocaine (30 and 60 μg · kg−1· min−1during 30 min) at steady-state plasma levels (1.9 ± 0.2 and 3.5 ± 0.2 μg/ml, respectively) were investigated in conscious dogs, previously instrumented for measurements of arterial and left ventricular (LV) pressures, isometric myocardial contractility indexes (LV peak rate of tension development [dP/dt] and LV [dP/dt]/DP40), and heart rate. In addition, before and at the end of lidocaine infusions, arterial baroreflex responses were tested by bolus injections of nitroglycerin and phenylephrine. Whereas LV peak dP/dt and LV (dP/dt)/DP40 were significantly decreased after the low dosage of lidocaine, these indexes returned to control values after the 10th min of infusion of the high dosage. Moreover, eight out of 14 dogs exhibited continuous tremors, tachycardia, hypertension, and increase in contractility after the 10th min of lidocaine infusion (60 μg · kg−1· min−1), although their lidocaine plasma levels (3.7 ± 0.2 μg/ml) did not differ from those of the whole group. When these dogs were pretreated by combined alpha- and beta-adrenoceptor blocking drugs, none of them had tremors, and there was a constant depressant effect on cardiac chronotropism and inotropism. A specific enhancement of baroreflex sensitivity after phenylephrine injection was observed at the high lidocaine dosage. It is concluded that a central stimulation of both components of the autonomic nervous system modulates the direct effects of therapeutic plasma levels of lidocaine on cardiac chronot-ropism and inotropism in conscious dogs.

ISSN:0003-3022    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

This study reports the results of a double-blind, parallel-group comparison of intravenous methadone with morphine for the control of postoperative pain. Twenty patients (ASA Status 1 or 2) undergoing a surgical procedure involving an upper abdominal incision were randomly allocated to the methadone (n = 10) or morphine (n = 10) treatment groups. The patients were administered a 20-mg intraopeative opioid dose and 5-mg intravenous increments of opioid from precoded syringes in response to pain in the recovery and surgical wards. There was no significant difference between the mean ± SD amount of supplementary methadone (8 ± 6.3 mg) and morphine (9 ± 9 mg) required in the recovery ward to provide initial pain control. The time from initial pain control to the first supplementary dose in the surgical ward was significantly different (P< 0.01) in the methadone group (20.7 ± 20.2 h) when compared to the morphine group (6.2 ± 3.0 h). Further, patients required significantly less (P< 0.001) methadone (11.5 ± 8.5 mg) than morphine (41 ± 14.1 mg) in the surgical ward to provide adequate pain relief throughout the duration of the study (i.e., 60 h). There was a significant difference in visual analogue pain scores between the methadone and morphine groups on postoperative days 1 and 2, suggesting the quality of pain relief was similar for both treatment groups. Blood opioid-concentration monitoring indicated that there was a relationship between blood opioid concentration and pain relief. The minimum effective concentration (MEC) (mean ± SD) values of methadone and morphine were 59.2 ± 24.1 ng/ml and 14.7 ± 4.8 ng/ml, respectively. However, there was a significantly larger (P< 0.001) intrasubject variability in the coefficient of variation in MEC for morphine (39.4 ± 6.6%) compared with methadone (17.8 ± 10.4%).

ISSN:0003-3022    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

The hemodynamic and cardiovascular effects of isoflurane and halothane anesthesia were studied in 15 unpremedicated ASA I children using measurements of heart rate, blood pressure and M-mode echocardiography (echo). The children (ages 2 to 7.3 yr) were randomly assigned to receive either isoflurane (N = 8) or halothane (N = 7) with oxygen. End-tidal carbon dioxide concentrations (range 30–44 mmHg) were monitored throughout the study in each child. The experimental protocol was completed prior to intubation and the initiation of surgery.Within each anesthetic group, preinduction (control) hemodynamic and echo measurements were compared with measurements obtained at two sequential equipotent end-tidal anesthetic concentrations (0.74% and 2.22% isoflurane; or 0.5% and 1.5% halothane). We also compared the data of the isoflurane group with that of the halothane group at each equipotent end-tidal anesthetic concentration. Preinduction hemodynamic (heart rate, blood pressure) and echo measurements (left ventricular dimensions and function) were similar between the two anesthetic groups. With isoflurane or halothane administration, blood pressure decreased significantly, while heart rate remained essentially unchanged. The observed alterations in heart rate and blood pressure were similar in both study groups at each equipotent end-tidal anesthetic concentration. In contrast, there were marked differences in the echo measurements of the two anesthetic groups. Halothane was associated with a significant dosedependent decrease in echo-measured left-ventricular shortening fraction and mean velocity of circumferential fiber shortening. These echo measurements were not significantly altered by isoflurane at either end-tidal anesthetic concentration. These alterations suggest halothane is associated with significant myocardial depression in normal children, while myocardial function is well preserved during isoflurane anesthesia.

ISSN:0003-3022    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

The authors determined the pharmacokinetics of fentanyl 100 μ·kg−1iv in patients undergoing elective abdominal aortic surgery. The mean (±SD) age of the ten patients was 67.2 ± 8.7 yr; their mean weight was 78.5 ± 13.7 kg. Seven patients had aortic aneurysm repair, and the other three patients had aortobifemoral grafts. Serum fentanyl concentrations were determined from samples drawn at increasing intervals over a 24-h period. A three-compartment pharmacokinetic model was fit to the concentrationversustime data. Total drug clearance was 9.8 ± 1.8 ml · min−1· kg−1. The volume of distribution at steady-state (Vdss) was 5.4 ± 1.9·1 kg−1. Elimination half-time was 8.7 ± 2.5 h. There were no significant correlations between these pharmacokinetic parameters and patient's age, duration of aortic cross-clamping, duration of surgery, intraoperative blood loss, or volume of iv fluids given intraoperatively. In healthy volunteers or patients undergoing general surgery, other investigators report mean elimination half-times for fentanyl ranging from 1.7 to 4.4 h. The prolonged elimination half-time in patients having abdominal aortic surgery has important clinical implications. In particular, recovery from large doses will take much longer than would have been anticipated from previously published fentanyl pharmacokinetic data.

ISSN:0003-3022    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

A total of 305 timed-pregnant Sprague-Dawley rats were exposed for 6 h a day on each of three consecutive days in one of three periods, i.e., pregnancy days 14–16, 11–13, or 8–10, either to 0.55 times the minimum alveolar concentration (MAC) of nitrous oxide (75%) or to 0.75 MAC of halothane (0.8%), isoflurane (1.05%) or enflurane (1.65%); an additional 232 positive-control (retinoic acid) and air control rats were studied. Reproductive indices were determined, and the 5178 offspring delivered at cesarean section were examined for external, internal, and skeletal abnormalities. There were no major or minor teratologic effects in anesthetic treated groups, although several developmental variants were observed in halothane- and enflurane-treated groups. Nitrous oxide exposure on days 14–16 resulted in a three-fold increase in fetal resorptions. The results suggest that the volatile anesthetics are not teratogenic and confirm that nitrous oxide may be associated with increased reproductive loss.

ISSN:0003-3022    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

Relationships between plasma concentrations of alfentanil and its analgesic, respiratory, and cardiovascular efects were determined in dogs. To avoid drug interaction, trained, unanesthetized, spontaneously breathing dogs were used. After a control period in the awake state, alfentanil was injected in increasing amounts (10, 20, 80, 160, and 320 μg/kg) at 5-min intervals to a total dose of 590 μg/kg administered over 20 min. The effects were observed on pain responses (heart rate and blood pressure changes and somatic reactions to tail clamping), respiration (respiratory rate, oxygen consumption [V01], blood gas tensions) and circulation (heart rate and blood pressure). The plasma concentration-effect curves, derived by relating the changes in multiple variables from the awake state to the corresponding plasma concentrations (range 8–5079 ng/ml), plateaued at and around 200 ng/ml during the injection period but were displaced in parallel to two-fold higher concentrations during recovery, which resembles acute tolerance. At maximally effective analgesic concentrations, which precipitated profound cardiorespiratory slowing with conspicuous hypoxemia, the V01of 4.4 ± 0.3 ml · kg−1· min−1corresponded with the calculated metabolic rate but increased to 6.3 ± 1.6 ml · kg−1during recovery. The analgesic action of alfentanil, which cannot be separated from its depressant cardiorespiratory effects and maximally effective analgesic concentrations (between 200 and 400 ng/ml), apparently does not jeopardize the adequacy of tissue oxygenation in dogs.

ISSN:0003-3022    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

Critically ill patients must often breathe spontaneously through an endotracheal tube that acts as a fixed inspiratory and expiratory tubular airway resistor. Although this practice is common, its effect on the pattern of breathing is not known. The mean breathing patterns of seven normal, healthy male subjects and eight male patients who had undergone upper abdominal surgery 2–4 days previously were studied breathing through a mouthpiece fitted in random order with a 5, 6, 7, 8, or 15 mm diameter (17 mm long) resistor. These diameters were selected because they simulate the pressure-flow relationships of adult endotracheal tubes. With the 15 mm aperture, the patients had a greater breathing frequency (f) than did the normal subjects (21 ± 5 [SD]vs.14 ± 4 breaths/min,P< 0.01) as well as a smaller mean tidal volume (VT). In both groups, minute ventilation (VE) and f progressively decreased as resistance was increased by decreasing the aperture size from 15 to 6 mm. In the normal subjects, but not the patients, &OV0312;Talso progressively decreased. When the diameter was decreased from 6 mm to 5 mm, there were increases in VTand decreases in f that were more marked in the normal subjects. In both groups, the changes in VEwere accompanied by decreases in mean and peak inspiratory and expiratory flow rates. Throughout the study, oxygen consumption (&OV0312;O2) and carbon dioxide production (&OV0312;CO2) did not change. This, coupled with the decreases in &OV0312;Eresulted in decreases in the ventilatory equivalents to CO2and O2(&OV0312;E/VCO2, VE/VO2). This study demonstrates that increasing tubular airway resistance significantly alters respiratory pattern without affecting gas exchange. When interpreting the breathing pattern of patients whose trachea is intubated, the clinician should consider the effects of the fixed tubular resistance. These results also reinforce previous admonitions that in patients with respiratory dysfunction, it is important to use as large an endotracheal tube as possible and allow spontaneous respirations only once substantial clinical improvement has occurred.

ISSN:0003-3022    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

Contractile responses of isolated rabbit aortic strips to epinephrine and norepinephrine were potentiated in a dose-related manner by (+) ketamine but not by (−) ketamine (1.1 × 10−1M - 3.7 × 10−4M). Potentiation was blocked completely by pretreatment with the extraneuronal uptake inhibitor cortisol (83–138 μM) but was unaffected by the neuronal uptake inhibitor cocaine (29 μM). Responses of the rat anococcygeus muscle to these catecholamines were potentiated by both isomers, with (+) ketamine being more potent than its optical antipode. These effects were blocked completely in tissues from 6-hydroxydopamine sympathectomized animals. Results suggest that inhibition of extraneuronal uptake of catecholamines by racecmic ketamine is due solely to an action of the (+) isomer, whereas both isomers appear capable of inhibiting neuronal uptake.

ISSN:0003-3022    

出版商:OVID    

年代:1986

数据来源: OVID