ISSN:0003-3022    

出版商:OVID    

年代:1990

数据来源: OVID

ISSN:0003-3022    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

Eighty-six patients undergoing coronary artery bypass graft (n = 63) or intracardiac (n = 23) surgery were randomly assigned with respect to the target value for Paco2during cardiopulmonary bypass. In 44 patients the target Paco2was 40 mmHg, measured at the standard electrode temperature of 37° C, while in 42 patients the target Paco2was 40 mmHg, corrected to the patient's rectal temperature (lowest value reached: mean 30.1, SD 1.9° C). Other salient features of bypass management include use of bubble oxygenators without arterial filtration, flows of 1.8–2.4 1·min−1·m−2, mean hematocrit of 23%, and mean arterial blood pressure of approximately 70 mmHg, achieved by infusion of phenylephrine or sodium nitroprusside. Neuropsychologic function was assessed with series of tests administered on the day prior to surgery, just before discharge from the hospital (mean 8.0, SD 5.8 days postoperatively, n = 82), and again 7 months later (mean 220.7, SD 54.4 days postoperatively, n =75). The scores at 8 days showed wide variability and generalized impairment unrelated to the Paco2group or to hypotension during cardiopulmonary bypass. At 7 months no significant difference was observed in neuropsychologic performance between the Paco2groups. Regarding cardiac outcome, there were no significant differences between groups in the appearance of new Q-waves on the electrocardiogram, the postoperative creatine kinase-MB fraction, the need for inotropic or intraaortic balloon pump support, or the length of postoperative ventilation or intensive care unit stay. These findings support the hypothesis that CO2management during cardiopulmonary bypass at moderate hypothermia has no clinically significant effect on either neurobehavioral or cardiac outcome.

ISSN:0003-3022    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

Acute regulation of blood pressure in humans is mediated by arterial baroreflex regulation of heart rate, cardiac contractility, and peripheral sympathetic outflow. Brief pharmacologic reductions of blood pressure were employed in 11 healthy volunteers to determine the effects of N2O on baroreflex-mediated increases in heart rate and efferent muscle sympathetic nerve activity. R-R intervals (ECG), blood pressure (radial artery), central venous pressure, respiratory rate (abdominal bellows), and end-tidal gas concentrations (mass spectrometer) were monitored. Efferent sympathetic nerve activity directed to skeletal muscle blood vessels (MSNA) was recorded from an epoxy-coated tungsten needle placed into the peroneal nerve. Data were obtained from six subjects before and during iv bolus administration of sodium nitroprusside (100 μg), during control while breathing 40% N2/60% O2, during administration of N2O (40% N2O/60% O2), and during recovery (40% N2/60% O2). Five subjects served as time controls and breathed 40% N2in O2throughout the protocol. Nitrous oxide produced a 59 ± 18% (P< 0.05) increase in baseline MSNA but did not alter the reflex augmentations in MSNA produced by nitroprusside. In contrast, there was a 39 ± 14% decrease in the slope of the relationship between systolic pressure and R-R interval (P< 0.05) in subjects breathing N2O. N2O thus produces activation of the sympathetic nerves directed to skeletal muscle blood vessels, and it decreases baroreflex-mediated tachycardia without diminishing baroreflex-mediated augmentations in sympathetic outflow.

ISSN:0003-3022    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

Activation of the renin-angiotensin system during open heart surgery may have consequences both beneficial in sustaining blood pressure and deleterious in compromising renal hemodynamics. The influence of short-term pretreatment with captopril on blood pressure and renal function was assessed double-blindversusplacebo in 18 patients without pre-existing cardiac or renal failure, and undergoing coronary artery bypass. No difference in blood pressure and fluid requirement during the surgical period was observed between groups receiving captopril or placebo. Effective renal plasma flow and glomerular filtration rate decreased in the placebo group whereas they remained unaltered in the captopril group; during cardiopulmonary bypass, urinary excretion of sodium was greater in patients receiving captopril than those receiving placebo. These results suggest that captopril pretreatment does not compromise the control of blood pressure and renal function during open heart surgery; additional studies on the protective value of angiotensin-converting enzyme inhibitors are warranted in patients at higher risk for developing renal failure.

ISSN:0003-3022    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

In order to evaluate the role of prostacyclin in d-tubocurarine-induced hypotension in human, the authors examined the relationship of changes of arterial blood pressure and plasma 6-keto-PGF1αlevel following iv administration of d-tubocurarine (dTc), with or without prior administration of aspirin and H1antagonist. The bolus injection of dTc 0.6 mg/kg caused a significant decrease in mean arterial pressure (MAP) that was associated with a significant increase in plasma 6-keto-PGF1α(P< 0.05 in both). The maximum MAP decrease and plasma 6-keto-PGF1αincrease were noted at 2 min after dTc administration. Pretreatment with aspirin DL-lysine (25 mg/kg) or diphenhydramine (1 mg/kg) significantly attenuated the responses of MAP (P< 0.05 in both) and plasma 6-keto-PGF1αlevel (P< 0.01 for aspirin group,P< 0.05 for diphenhydramine group). There was a significant correlation between the changes in plasma 6-keto-PGF1αand those in MAP (Kendall tau (τ) = −0.504,P< 0.01). These findings suggest that a bolus injection of dTc induces a release of prostacyclin through H1receptor, which is responsible for the dTc-induced transient decrease of blood pressure in humans.

ISSN:0003-3022    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

The effect of ketamine alone and in combination with N2O (70% inspired) on median nerve somatosensory evoked potentials (SSEPs) was investigated in 16 neurologically normal patients undergoing elective abdominopelvic procedures. The anesthetic regimen consisted of ketamine (2 mg/kg iv bolus followed by continuous infusion at a rate of 30 μg·kg−1·hr−1), neuromuscular blockade (atracurium), and mechanical ventilation with 100% oxygen. SSEP recordings were obtained immediately preinduction and at 2, 5, 10, 15, 20, and 30 min postinduction. Thereafter, N2O was added with surgical incision and maintained for 15 min. At 5-min intervals, SSEP recordings were again taken during and after N2O. With minor exceptions, mean cortical and noncortical latencies as well as noncortical-evoked potential amplitude were unaffected by either ketamine or N2O. Ketamine induction increased cortical amplitude significantly with maximal increases occurring within 2–10 min. For example, at 5-min postinduction, mean N1-P1 amplitude increased from 2.58 ± 1.05 (baseline) to 2.98 ± 1.20 μV and P1-N2 amplitude increased from 2.12 ± 1.50 (baseline) to 3.99 ± 1.76 μV. Throughout the 30-min period after ketamine induction, mean P1-N2 amplitude increased generally by more (57–88%) than did mean N1-P1 amplitude (6–16%). N2O added to the background ketamine anesthetic produced a rapid and consistent reduction in both N1-P1 and P1-N2 amplitude. Thus, at 1 min after N2O, mean N1-P1 amplitude decreased from 2.74 ± 1.11 to 1.64 ± 0.63 μV, while P1-N2 amplitude decreased from 3.32 ± 1.52 to 1.84 ± 0.87 μV. After 15 min of N2O, these amplitudes remained depressed at 1.35 ± 0.52 and 1.72 ± 0.71 μV, respectively. On elimination of N2O level. It is concluded that, when used as the sole anesthetic agent, ketamine enhances the cortical component of the human somatosensory evoked potential. However, when N2O is introduced, the ketamine enhanced cortical amplitude is reduced by approximately 50%. When judged against the known depressant effect of N2O, this would suggest that ketamine and N2O are near additive with respect to their effects on cortical SSEP amplitude.

ISSN:0003-3022    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

The purpose of this study was to determine whether the pressure produced by contact between a transesophageal echocardiography (TEE) probe and the esophagus was sufficient to cause esophageal damage. The authors studied the effects of sustained contact and associated surface pressure on the esophagus by a TEE probe in anesthetized dogs and humans. Contact pressure between the tip of the probe and the esophageal wall in dogs was measured using a previously described flat balloon of Silastic fitted to the end of a TEE probe and the recording system calibrated with a mercury manometer. In the dog studies, the probe was inserted, maximally flexed, and its position fixed for 4, 6, 8, and 12 h. The maximum surface pressure generated by contact between a probe and the esophageal wall was 10 mmHg. Subsequent pathologic studies failed to reveal either gross or microscopic evidence of tissue damage.The same system was used in short-term patient studies with the surface contact pressure transducer connected to a Camino Catheter 420 Digital Pressure Monitor. In five of six patients contact pressure was <17 mmHg despite maximal rotation of the TEE controls. However, one of the six patients developed very high contact pressure, up to 60 mmHg, between the probe and the esophagus. This patient had no history of esophageal disease but did have intrathoracic pathology.The authors conclude that the maximum surface contact pressure between the esophagus and a fully flexed TEE probe is low in dogs and in most humans, and is unassociated with histologic esophageal damage even with long exposure. However, potentially dangerous pressure may be generated in some cases in humans. It is suggested that the TEE probe not be fixed in a flexed position for prolonged periods since a subset of patients may exist who are at risk for development of high contact pressure and potential esophageal damage.

ISSN:0003-3022    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

This study examined the efficacy of patient-controlled epidural analgesia (PCEA) during labor and compared the suitability of three different PCEA solutions. After establishing effective epidural analgesia with 12 ml of 0.25% bupivacaine, 72 parturients in active labor were randomly assigned to one of four groups: physician-controlled continuous epidural infusion using 0.125% bupivacaine (CEI); PCEA using 0.125% bupivacaine (B); PCEA using 0.125% bupivacaine with fentanyl 1 μg/ml (BF); and PCEA using 0.125% bupivacaine with fentanyl 1 μg/ml and 1:400,000 epinephrine (BFE). The CEI infusion was begun at 12–16 ml/h and adjusted to maintain a T10 sensory level and adequate pain relief. PCEA pumps were programmed to deliver a 6 ml/h basal infusion, 4 ml on-demand boluses, 10-min lockout intervals between doses, and a 20 ml hourly limit. Hemodynamic parameters, sensory level, quality of analgesia, duration of labor, overall satisfaction, and Apgar scores did not differ among groups. Compared with CEI, PCEA with plain bupivacaine did not decrease total local anesthetic usage or average hourly infusion rates during labor. However, addition of fentanyl (groups BF and BFE) decreased hourly infusion requirements. Average hourly infusion rates were 13.0 ± 1.1 ml/h (B), 10.6 ± 0.6 ml/h (BF), and 9.6 ± 0.5 ml/h (BFE); group B differs from others (P< 0.05). No instance of respiratory depression or complication secondary to PCEA was observed. Mild pruritus occurred only with fentanyl-containing solutions, whereas dense motor block developed more frequently with the epinephrine-containing solution. These data suggest that PCEA is a safe and effective method for labor analgesia but that it does not reduce anesthetic requirements or improve analgesia compared with a closely titrated infusion. Of the solutions tested, 0.125% bupivacaine plus fentanyl, 1 μg/ml, appears the most suitable for PCEA use.

ISSN:0003-3022    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

Caffeine sensitivity was studied in chemically skinned muscle fibers from vastus lateralis muscle obtained by biopsy during reconstructive knee surgery from 15 otherwise healthy young individuals. Muscle fiber type was determined by contracture occurring in strontium (slow-oxidative, type I fiber) or calcium (both type I and type II, fast glycolytic fiber) solutions and in several fibers after contracture testing by ATPase enzyme histochemistry. Caffeine sensitivity (mean ± SD), defined as the threshold concentration inducing more than 10% of the maximal tension obtained with a calcium 3 × 10−5mM solution was 2.7 ± 1.3 mM in 37 type I fibers, whereas it was 6.9 ± 2.4 mM in 61 type II fibers. A pairedttest showed a significantly increased sensitivity to caffeine in type I fibers (P< 0.001) in 13 individuals in whom the two fiber types were identified. The mean (±SD) difference between type I and type II fibers was 4.1 ± 1.9 mM. Type I fibers contracted with greater tension in response to the increasing concentration of caffeine than did type II fibers (P< 0.05). These skinned fiber studies showed significantly different caffeine sensitivities between human type I and type II muscle fibers, as previously shown in animal muscles. The findings that human type I muscle fibers have higher caffeine sensitivity than type II muscle fibers should be helpful for the interpretation of thein vitrocontracture test done in muscle strips containing type I and type II fibers in varying proportions.

ISSN:0003-3022    

出版商:OVID    

年代:1990

数据来源: OVID