ISSN:0003-3022    

出版商:OVID    

年代:1984

数据来源: OVID

摘要:

To investigate the central nervous system circulation during spinal anesthesia, local spinal cord blood flow (SCBF) and cerebral blood flow (CBF) were measured simultaneously by the hydrogen clearance technique following subarachnoid lidocaine, phenylephrine, or a combination of both. The mean control values of SCBF and CBF were 22.4 ± 7.9 ml.100 g−1·min−1and 53.1 ± 12.0 ml·100 g−1·min−1, respectively, in dogs lightly anesthetized with halothane.The subarachnoid administration of lidocaine solutions (1, 2, 3, and 5%), 1 ml, failed to produce statistically significant changes in SCBF (P > 0.05). Whereas, when phenylephrine (0.1, 0.2, 0.3, and 0.5%), 1 ml, was injected into the spinal subarachnoid space, SCBF decreased significantly with concentrations greater than 0.2% (P < 0.05). When a mixture of lidocaine (24 mg) and phenylephrine (1 mg) was administered into the subarachnoid space, SCBF decreased significantly and returned to control within 60–90 min. CBF did not change significantly with any of the injections, remaining within less than ±12% of control. Dextrose solutions in water (5 and 7.5%), which were used for dilution of the drugs, did not affect either SCBF or CBF. These results indicate that local spinal cord blood flow can be affected significantly during spinal anesthesia when phenylephrine is added to the local anesthetic solution. However, the circulatory effects of drugs injected into the spinal subarachnoid space appear to be restricted to the local spinal cordper seand do not involve other parts of the CNS.

ISSN:0003-3022    

出版商:OVID    

年代:1984

数据来源: OVID

摘要:

Both halothane (HAL) and acid-base changes produce cardiac arrhythmias in humans. The authors' aim was to determine if HAL alters the effects of hypercapnic acidosis and hypocapnic alkalosis on action potential (AP) properties of ventricular muscle fibers. They superfused the paced right ventricle of 15 guinea pig hearts with non-HCO3buffered salt solution and recorded transmembrane APs with 3 M KCl microelectrodes in 35 subendocardial cells. Random changes in the fractions of HAL were made during low (12% CO2in O2), normal (5% CO2in O2), and high (0% CO2in O2)pH. Compared with controls atpH 7.44, AP duration (APD) and effective refractory period (ERP) significantly decreased by 7 and 4% atpH 8.08 and increased by 7 and 9% atpH 7.09. AtpH 7.44, 0.7–2.1% HAL produced no change in APD; but 2.1% increased ERP, while 3.5% HAL decreased ERP. AtpH 8.08, the decrease in ERP induced with alkalosis alone was converted to an increase with 1.4 and 2.1% HAL. AtpH 7.09, 0.7–1.4% HAL had no additional effect on the acidosis-induced increases in APD and ERP, but 2.1 and 2.8% HAL greatly reduced these responses. At HAL fractions greater than 1.4% the marked inverse changes in APD and ERP, induced alone by acidosis and alkalosis, were no longer significantly different from control. This study shows that the opposing effects of alkalosis to shorten and of acidosis to lengthen APD and ERP were attenuated at low levels and abolished at high levels of HAL. Because increases in ERP may reduce the vulnerability of cardiac fibers to re-entrant excitation, the local proarrhythmogenic effect of alkalosis may be diminished with clinical levels of HAL; also the local antiarrhythmogenic effect of acidosis may be diminished, but only at higher levels of HAL.

ISSN:0003-3022    

出版商:OVID    

年代:1984

数据来源: OVID

摘要:

Because the belief that cyanide is released from nitroprussidein vivorecently was challenged, the authors performed a series of experiments that examined the conditions under which nitroprusside is degraded. These experiments include an examination of the release of cyanide and nitric oxide from nitroprussidein vitro, the release of cyanidein vivo, and a comparison of the biologic activity of intact and degraded nitroprusside. Nitroprusside in aqueous solution degraded when exposed to white or blue light but not to red light. While light at 20 μW·cm−2produced 40% apparent photodegradation after 6 h exposure, while white light at 220 μW·cm−2produced 100% apparent photodegradation after 2 h exposure. At 100% apparent photodegradation, 10% of the nitrosyl ligand was recovered as free nitric oxide, and 0.4% of the cyanide ligand was recovered as free cyanide. Following a 2-h infusion of light-protected nitroprusside in seven patients, cyanide concentrations ranged from 1.4 to 45.5 μM and 0.09 to 3.2 μM in blood and plasma, respectively. These values were not changed by exposing the samples to white light (220 μW·cm−2) for 4 h. Intact and photodegraded nitroprusside produced identical hypotensive responses in rats as would be expected, since the nitrosyl ligand was detected in solution following degradation, and it mediates this action. Cyanide was released from nitroprusside, both on its exposure to lightin vitroand alsoin vivo. The latter was not an artifact of the assay for cyanide. Nitroprusside releases cyanidein vivo, and cyanide toxicity is a true complication of its use.

ISSN:0003-3022    

出版商:OVID    

年代:1984

数据来源: OVID

摘要:

The effect of incremental doses of fentanyl on brain-stem auditory evoked potentials (BAEPs) was studied in 10 patients scheduled for elective surgery. Seven sets of BAEPs were recorded in each patient starting the day before surgery, after premedication and after 10 μg/kg increments of fentanyl up to 50 μg/kg. No significant effect on either absolute or interpeak latencies of wave I, III, and V of evoked potentials was observed.

ISSN:0003-3022    

出版商:OVID    

年代:1984

数据来源: OVID

摘要:

The hypotension accompanying isoflurane suggests that the anesthetic produces an attenuation of sympathetic tone. Previous studies examining the effects of isoflurane on sympathetic efferent nerve activity have required concomitant use of a basal anesthetic or decerebration, both of which independently alter sympathetic activity. This study was performed to examine the effects of isoflurane on sympathetic efferent nerve activity in the absence of basal anesthetic or decerebration. Five mongrel dogs were anesthetized with 4% isoflurane by mask. Platinum electrodes chronically were implanted around a renal nerve adjacent to the renal artery in order to measure renal sympathetic efferent nerve activity in the conscious and anesthetized animal. After 5–24 h for recovery, renal nerve activity and arterial pressure (via an implanted femoral artery cannula) were measured in the conscious, resting animal (control); during induction (4% isoflurane) and intubation; in the anesthetized animal (1.5% and 2.5% isoflurane); and during recovery and extubation.Isoflurane produced a significant dose-dependent depression of arterial blood pressure but did not significantly change heart rate from control. Renal sympathetic efferent nerve activity at 1.5% isoflurane was not significantly different from that in conscious animals, but nerve activity at 2.5% isoflurane was depressed significantly from both control and 1.5% isoflurane. Both intubation and extubation were accompanied by an increase in sympathetic nerve activity. Isoflurane appeared to directly depress sympathetic activity at both levels of anesthesia, but the direct depression of activity at 1.5% isoflurane seemed to be countered by reflex increases in sympathetic tone due to the hypotension accompanying the anesthesia. At 2.5% isoflurane, the central depression of reflex activity by isoflurane combined with direct depression of sympathetic efferent activity resulted in the attenuation of renal nerve activity.

ISSN:0003-3022    

出版商:OVID    

年代:1984

数据来源: OVID

摘要:

From July 1977 to December 1982, 6,245 patients requiring cardiac and noncardiac operations had pulmonary artery (PA) catheterizations for perioperative monitoring. Their ages ranged from 4 to 94 years. PA catheters were inserted through the external or internal jugular vein in 6,146 patients, while arm veins were used in 99 patients. Complications included persistent PVCs requiring therapy in 193 (3.1%), right bundle branch blocks in three (0.048%), left bundle branch and complete heart block each in one patient (0.016%), intrapulmonary hemorrhage in four (0.064%), minor pulmonary infarcts in four (0.064%), perforation of right ventricle in one (0.016%), and death from uncontrollable pulmonary hemorrhage in one patient (0.016%). This investigation reveals a low incidence of morbidity associated with PA catheterization.

ISSN:0003-3022    

出版商:OVID    

年代:1984

数据来源: OVID

ISSN:0003-3022    

出版商:OVID    

年代:1984

数据来源: OVID

摘要:

The authors evaluated the accuracy of a system to measure respiratory gas exchange on an on-line basis by comparing it with a gas collection method. The system incorporates a hot-wire flowmeter, a mass spectrometer, and a microcomputer. It performs on-line compensation for both transport delay and dynamic response of the mass spectrometer. Compensation of flow measurement for changing gas fractions also is performed. Excellent linear correlations were obtained between the two methods: 1) in animals during mechanical ventilation with room air (&OV0312;O2: r = 0.995; &OV0312;CO2: r = 0.993), and nitrous oxide in oxygen (&OV0312;O2: r = 0.975; &OV0312;CO2: r = 0.976); and 2) in men spontaneously breathing room air at different workloads (&OV0312;O2: r = 0.999; &OV0312;CO2: r = 0.998), and higher inspired oxygen fractions (FlO20.38 to 0.75) (&OV0312;O2: r = 0.910; &OV0312;CO2: r = 0.988). The authors consider that the system is suited for accurate and continuous measurement of respiratory gas exchange during mechanical ventilation, anesthesia, and exercise testing.

ISSN:0003-3022    

出版商:OVID    

年代:1984

数据来源: OVID

摘要:

Measurement of serum fentanyl and aifentanil concentrations by radioimmunoassay (RIA) may result in significant errors and high variability when the technique described in the available fentanyl and alfentanil RIA kits is used. The authors found a 29–94% overestimation of measured fentanyl and alfentanil serum levels when3H-fentanyl or3H-alfentanil was added lastly to the mixture of antiserum and sample. This finding is related to a reduction in binding sites for the labeled compounds after preincubation of sample and antiserum. If this sequence is used, it becomes necessary to extend the incubation period up to 6 h for fentanyl and up to 10 h for alfentanil in order to achieve equilibration between unlabeled and labeled drug with respect to antiserum binding. However, when antiserum is added lastly to the mixture of sample and labeled drug, measurement accuracy and precision for fentanyl and alfentanil serum concentrations are enhanced markedly. In addition, it is important to perform the calibration curves and sample measurements using the same medium (i.e., serum alone or a serum / buffer dilution). In summary, to optimize the RIA for fentanyl and alfentanil, the authors recommend the following: 1) adding the antiserum lastly to the mixture of sample and labeled drug; 2) performing calibration curves using patient's blank serum when possible; 3) carefully examining and standardizing each step of the RIA procedure to reduce variability, and, finally; 4) comparing results with those of other established RIA laboratories.

ISSN:0003-3022    

出版商:OVID    

年代:1984

数据来源: OVID