Methods: New Zealand White rabbits, anesthetized with fentanyl and diazepam, were maintained during cardiopulmonary bypass (CPB) at a brain temperature of 17 degrees Celsius with alpha-stat (group A, n = 9) or pH-stat (group B, n = 9) management. Measurements of brain temperature, systemic hemodynamics, arterial and cerebral venous blood gases and oxygen content, cerebral blood flow (CBF) (radiolabeled microspheres), and cerebral metabolic rate for oxygen (CMRO2) (Fick) were made in each animal at 65 and 95 min of CPB. To control for arterial pressure and CBF differences between techniques, additional rabbits underwent CPB at 17 degrees Celsius. In group C (alpha-stat, n = 8), arterial pressure was decreased with nitroglycerin to values observed with pH-stat management. In group D (pH-stat, n = 8), arterial pressure was increased with angiotensin II to values observed with alpha-stat management. In groups C and D, CBF and CMRO2 were determined before (65 min of CPB) and after (95 min of CPB) arterial pressure manipulation.
Results: In groups A (alpha-stat) and B (pH-stat), arterial pressure; hemispheric CBF (44 plus/minus 17 vs. 21 plus/minus 4 ml *symbol* 100 g sup -1 *symbol* min sup -1 [median plus/minus quartile deviation]; P = 0.017); and CMRO2 (0.54 plus/minus 0.13 vs. 0.32 plus/minus 0.10 ml Oxygen2 *symbol* 100 g sup -1 *symbol* min sup -1; P = 0.0015) were greater in alpha-stat than in pH-stat animals, respectively. As a result of arterial pressure manipulation, in groups C (alpha-stat) and D (pH-stat) neither arterial pressure (75 plus/minus 2 vs. 78 plus/minus 2 mm Hg) nor hemispheric CBF (40 plus/minus 10 vs. 48 plus/minus 6 ml *symbol* 100 g sup -1 *symbol* min sup -1; P = 0.21) differed between alpha-stat and pH-stat management, respectively. Nevertheless, CMRO2 was greater in alpha-stat than in pH-stat animals (0.71 plus/minus 0.10 vs. 0.45 plus/minus 0.10 ml Oxygen2 *symbol* 100 g sup -1 *symbol* min sup -1, respectively; P = 0.002). 相似文献
Methods: Anesthetized New Zealand white rabbits, cooled to 25 degrees Celsius on cardiopulmonary bypass, were randomized to one of two rewarming groups. In the fast group (n = 9), aortic blood temperature was made normothermic over 25 min. Cerebral blood flow (microspheres) and CMRO2 (Fick) were determined at baseline (25 degrees C), and at brain temperatures of 28 degrees, 31 degrees, 34 degrees, and 37 degrees Celsius during rewarming.
Results: Systemic physiologic variables appeared similar between groups. At a brain temperature of 28 degrees C, CMRO2 was 47% greater in the fast rewarming group than in the slow group (2.2 +/-0.5 vs. 1.5+/-0.2 ml O2 *symbol* 100 g sup -1 *symbol* min sup -1, respectively; P = 0.01), whereas CBF did not differ (48+/-18 vs. 49+/-8 ml *symbol* 100 g sup -1 *symbol* min sup -1, respectively; P = 0.47). Throughout rewarming, CBF increased as a function of brain temperature but was indistinguishable between groups. Cerebral metabolic rate for oxygen differences between groups decreased as brain temperatures increased. 相似文献
Methods: As pericranial temperature was varied between 39 and 25 degrees Celsius in normocapnic halothane-anesthetized rats, CMRG (using14 Carbon-deoxyglucose) or the time to depolarization (using a glass microelectrode in the cortex) after a Potassium sup + -induced cardiac arrest was measured. In other studies, CMRG and depolarization times were measured in normothermic animals (37.7 plus/minus 0.2 degree Celsius) anesthetized with high-dose pentobarbital or isoflurane (both producing burst suppression on the electroencephalogram) or in halothane-anesthetized animals whose temperatures were reduced to 27.4 plus/minus 0.3 degree Celsius. These three states were designed to produce equivalent CMRG values.
Results: As temperature was reduced from 39 to 25 degrees Celsius, CMRG decreased from 66 to 21 micro Meter *symbol* 100 g sup -1 *symbol* min1 (Q10 = 2.30), and depolarization times increased from 76 to 326 s. In similarly anesthetized animals at approximately 27 degrees Celsius, CMRG was 32 plus/minus 4 micro Meter *symbol* 100 g sup -1 *symbol* min sup -1 (mean plus/minus SD), whereas in normothermic pentobarbital- and isoflurane-anesthetized rats, CMRG values were 33 plus/minus 3 and 37 plus/minus 4 micro Meter *symbol* 100 g1 *symbol* min sup -1, respectively (P = 0.072 by one-way analysis of variance). Despite these similar metabolic rates, the times to depolarization were markedly different: for hypothermia it was 253 plus/minus 29 s, for pentobarbital 109 plus/minus 24 s, and for isoflurane 130 plus/minus 28 s (P < 0.0001). 相似文献
Methods: Cardiopulmonary bypass was initiated in seven baboons during fentanyl, midazolam, and isoflurane anesthesia. Animals were cooled at a pump flow rate of 2.5 l *symbol* min-1 *symbol* m-2 until esophageal temperature decreased to 20 degrees C. Cardiopulmonary bypass flow was then reduced to 0.5 l *symbol* min-1 *symbol* m-2 (low flow). During low-flow CPB, arterial partial pressure of carbon dioxide (PCO2) and blood pressure were varied in random sequence to three conditions: (1) PCO2 30-39 mmHg (uncorrected for temperature), control blood pressure; (2) PCO2 50-60 mmHg, control blood pressure; and (3) PCO2 30-39 mmHg, blood pressure raised to twice control by phenylephrine infusion. Thereafter, CPB flow was increased to 2.5 l *symbol* min-1 *symbol* m-2, and baboons were rewarmed to normal temperature. Cerebral blood flow was measured by washout of intraarterial133 Xenon before and during CPB.
Results: Phenylephrine administered to increase mean blood pressure from 23+/-3 to 46+/-3 mmHg during low-flow CPB increased CBF from 14+/-3 to 31+/-9 ml *symbol* min-1 *symbol* 100 g-1, P < 0.05. Changes in arterial PCO2 alone during low flow bypass produced no changes in CBF. 相似文献
Methods: Sagittal sinus and cortical microdialysis catheters were inserted into anesthetized pigs. Animals were placed on CPB and randomly assigned to 37 [degree sign] Celsius (n = 10), 34 [degree sign] Celsius (n = 10), 31 [degree sign] Celsius (n = 11), or 28 [degree sign] Celsius (n = 10) management. Next 20 min of global cerebral ischemia was produced by temporarily ligating the innominate and left subclavian arteries, followed by reperfusion, rewarming, and termination of CPB. Cerebral oxygen metabolism (CMRO2) was calculated by cerebral blood flow (radioactive microspheres) and arteriovenous oxygen content gradient. Cortical excitatory amino acids (EAA) by microdialysis were measured using high-performance liquid chromatography. Electroencephalographic (EEG) signals were graded by observers blinded to the protocol. After CPB, cerebrospinal fluid was sampled to test for S-100 protein and the cerebral cortex was biopsied.
Results: Cerebral oxygen metabolism increased after rewarming from 28 [degree sign] Celsius, 31 [degree sign] Celsius, and 34 [degree sign] Celsius CPB but not in the 37 [degree sign] animals; CMRO2, remained lower with 37 [degree sign] Celsius (1.8 +/- 0.2 ml [center dot] min sup -1 [center dot] 100 g sup -1) than with 28 [degree sign] Celsius (3.1 +/- 0.1 ml [center dot] min sup -1 [center dot] 100 g sup -1; P < 0.05). The EEG scores after CPB were depressed in all groups and remained significantly lower in the 37 [degree sign] Celsius animals. With 28 [degree sign] Celsius and 31 [degree sign] Celsius CPB, EAA concentrations did not change. In contrast, glutamate increased by sixfold during ischemia at 37 [degree sign] Celsius and remained significantly greater during reperfusion in the 34 [degree sign] Celsius and 37 [degree sign] Celsius groups. Cortical biopsy specimens showed no intergroup differences in energy metabolites except two to three times greater brain lactate in the 37 [degree sign] Celsius animals. S-100 protein in cerebrospinal fluid was greater in the 37 [degree sign] Celsius (6 +/- 0.9 micro gram/l) and 34 [degree sign] Celsius (3.5 +/- 0.5 micro gram/l) groups than the 31 [degree sign] Celsius (1.9 +/- 0.1 micro gram/l) and 28 [degree sign] Celsius (1.7 +/- 0.2 micro gram/l) animals. 相似文献
Methods: Five volunteers were each studied on 4 days: (1) control; (2) a target blood propofol concentration of 2 micro gram/ml; (3) a target concentration of 4 micro gram/ml; and (4) a target concentration of 8 micro gram/ml. On each day, we increased skin and core temperatures sufficiently to provoke sweating. Skin and core temperatures were subsequently reduced to elicit peripheral vasoconstriction and shivering. We mathematically compensated for changes in skin temperature by using the established linear cutaneous contributions to the control of sweating (10%) and to vasoconstriction and shivering (20%). From these calculated core-temperature thresholds (at a designated skin temperature of 35.7 degrees Celsius), the propofol concentration- response curves for the sweating, vasoconstriction, and shivering thresholds were analyzed using linear regression. We validated this new method by comparing the concentration-dependent effects of propofol with those obtained previously with an established model.
Results: The concentration-response slopes for sweating and vasoconstriction were virtually identical to those reported previously. Propofol significantly decreased the core temperature triggering vasoconstriction (slope = 0.6 plus/minus 0.1 degree Celsius *symbol* micro gram sup -1 *symbol* ml sup -1; r2 = 0.98 plus/minus 0.02) and shivering (slope = 0.7 plus/minus 0.1 degree Celsius *symbol* micro gram sup -1 *symbol* ml sup -1; r2 = 0.95 plus/minus 0.05). In contrast, increasing the blood propofol concentration increased the sweating threshold only slightly (slope = 0.1 plus/minus 0.1 degree Celsius *symbol* micro gram sup -1 *symbol* ml sup -1; r2 = 0.46 plus/minus 0.39). 相似文献
Methods: Thirteen neurosurgical patients underwent cardiopulmonary bypass and deep hypothermic circulatory arrest to facilitate clip application to a giant or otherwise high-risk cerebral aneurysm. Electroencephalographic burst suppression was established before bypass with an infusion of propofol, and the infusion was continued until the end of surgery. Hemodynamic and echocardiographic measurements were made before and during the prebypass propofol infusion and again after bypass. Emergence time also was determined.
Results: Prebypass propofol at 243 plus/minus 57 micro gram *symbol* kg sup -1 *symbol* min sup -1 decreased vascular resistance from 34 plus/minus 8 to 27 plus/minus 8 units without changing heart rate, arterial or filling pressures, cardiac index, stroke volume, or ejection fraction. Propofol blood concentration was 8 plus/minus 2 micro gram/ml. Myocardial wall motion appeared hyperdynamic at the end of cardiopulmonary bypass, and all patients were weaned therefrom without inotropic support. After bypass, vascular resistance decreased further, and cardiovascular performance was improved compared to baseline values. Nine of the 13 patients emerged from anesthesia and were able to follow commands at 3.1 plus/minus 1.4 h. Three others had strokes and a fourth had cerebral swelling. 相似文献
Methods: Fifty-six awake Wistar rats were assigned to seven groups of eight. All groups received a continuous intravenous infusion of lidocaine at a rate of 4 mg *symbol* kg sup -1 *symbol* min sup -1 until generalized convulsions occurred. The control group (group C) received plain lidocaine. The acute hypertensive groups received lidocaine with epinephrine (group E), norepinephrine (group N), or phenylephrine (group P) to increase mean arterial blood pressure (MAP) to 150 plus/minus 5 mm Hg. Sodium nitroprusside (SNP) was added to prevent an increase in mean arterial pressure in the remaining three groups (vasopressor-SNP groups).
Results: The acute hypertensive groups required significantly smaller cumulative doses of lidocaine to produce convulsions compared with control (C - 41.5 plus/minus 2.9 > E - 24.1 plus/minus 2.7, N = 27.1 plus/minus 2.8, P = 26.7 plus/minus 2.5 mg *symbol* kg sup -1; values are mean plus/minus SD, P < 0.01) In addition, plasma lidocaine concentrations (C = 11.0 plus/minus 0.7 > E = 7.4 plus/minus 0.5, N = 7.9 plus/minus 0.6, P = 8.1 plus/minus 0.8 micro gram *symbol* ml sup -1, P < 0.01) and brain lidocaine concentrations (C = 50.9 plus/minus 4.5 > E = 32.6 plus/minus 4.2, N - 34.5 plus/minus 4.8, P - 37.1 plus/minus 4.5 micro gram *symbol* g sup -1, P < 0.01) were less in the acute hypertensive groups at the onset of convulsions. In the vasopressor-SNP groups, the plasma and brain lidocaine concentrations at the onset of convulsions returned to the control values, although epinephrine and norepinephrine, but not phenylephrine, still decreased cumulative convulsant doses of lidocaine significantly (P < 0.01) compared with control (E + SNP = 30.8 plus/minus 2.9 < N + SNP = 34.8 plus/minus 2.8, P < 0.01) < P + SNP = 40.2 plus/minus 3.0 mg *symbol* kg sup -1, P < 0.01). The brain/plasma concentration ratios were similar for the seven groups. 相似文献
Methods: We studied 96 otherwise healthy children, 8-13 yr old, undergoing minor surgery. They received, at random, oral clonidine 2 or 4 micro gram *symbol* kg sup -1 or placebo 105 min before scheduled induction of anesthesia. Part I (n = 48, 16 per group): When hemodynamic parameters after insertion of a venous catheter had been confirmed to be stable, atropine was administered in incremental doses of 2.5, 2.5, and 5 micro gram *symbol* kg sup -1 every 2 min. The HR and blond pressure were recorded at 1-min intervals. Part II (n = 48, 16 per group): After the recording of baseline hemodynamic values, successive doses of atropine (5 micro gram *symbol* kg sup -1 every 2 min, to 40 micro gram *symbol* kg sup -1), were administered until HR increased by 20 beats *symbol* min sup -1. The HR and blood pressure were recorded at 1-min intervals.
Results: Part I: The increases in HR in response to a cumulative dose of atropine 10 micro gram *symbol* kg sup -1 were 33 plus/minus 3%, 16 plus/minus 3%, and 8 plus/minus 2% (mean plus/minus SEM) in children receiving placebo, clonidine 2 micro gram *symbol* kg sup -1, and clonidine 4 micro gram *symbol* kg sup -1, respectively (P < 0.05). Part II: The HR in the control group increased by more than 20 beats *symbol* min sup -1 in response to atropine 20 micro gram *symbol* kg sup -1 or less. In two patients in the clonidine 4 micro gram *symbol* kg sup -1 group, HR did not increase by 20 beats *symbol* min sup -1 even after 40 micro gram *symbol* kg sup -1 of atropine. 相似文献
Methods: The effects of propofol (1, 3, and 10 micro gram *symbol* ml sup -1) on the intrinsic contractility of left ventricular papillary muscles from normal hamsters and those with hypertrophic cardiomyopathy (strain BIO 14.6, aged 6 months) were investigated in vitro (Krebs-Henseleit solution, 29 degrees Celsius, pH 7.40, Calcium sup +1 2.5 mmol *symbol* l [1], stimulation frequency 3/min).
Results: Cardiac hypertrophy (143 plus/minus 13%, P < 0.001) was observed in cardiomyopathic hamsters. The contractility of papillary muscles from hamsters with cardiomyopathy was less than that of controls, as shown by the decrease in maximum shortening velocity (29%, P < 0.03) and active isometric force (-51%, P < 0.03) and active isometric force (-51%, P < 0.001). Propofol did not induce any significant effect on contraction, relaxation, and contraction-relaxation coupling under low and high loads in normal hamsters. The effects of propofol were not significantly different between normal hamsters and those with cardiomyopathy. A slight but significant increase in maximum unloaded shortening velocity was observed in cardiomyopathic hamsters at 3 micro gram *symbol* ml sup -1 (4 plus/minus 6%, P < 0.05) and 10 micro gram *symbol* ml sup -1 (7 plus/minus 6%, P < 0.05). 相似文献
Methods: After an overnight fast, six adolescents between 12 and 17 yr of age were infused with tracer doses of [6,6-sup 2 H2]glucose for 2 h before undergoing anesthesia, and the infusion was continued after induction, until the beginning of surgery. Plasma glucose concentration was monitored throughout, and free fatty acids, lactate, insulin, and glucagon concentrations were measured before and during anesthesia.
Results: Despite the use of a glucose-free maintenance solution, plasma glucose concentration increased slightly but significantly 5 min after induction (5.3 plus/minus 0.4 vs. 4.5 plus/minus 0.4 mmol *symbol* 1 sup -1 , P < 0.05). This early increase corresponded to a significant increase in endogenous glucose production over basal conditions (4.1 plus/minus 0.4 vs. 3.6 plus/minus 0.2 mg *symbol* kg sup -1 *symbol* min sup -1, P < 0.05), with no concomitant change in peripheral glucose utilization. Fifteen minutes after induction, both glucose utilization and production rates decreased steadily and were 20% less than basal values by 35 min after induction (2.9 plus/minus 0.3 vs. 3.6 plus/minus 0.2 mg *symbol* kg sup -1 *symbol* min sup -1, P < 0.05). Similarly, glucose metabolic clearance rate decreased by 25% after 35 min. Despite the increase in blood glucose concentration, anesthesia resulted in a significant decrease in plasma insulin concentration. 相似文献
Methods: In experiment 1, Sprague-Dawley rats were anesthetized with halothane in 50% Oxygen2 -balance Nitrogen2 and their lungs mechanically ventilated. They were randomly assigned to one of three groups according to the dose of ACEA-1021 administered (0, 20, or 40 mg/kg intravenously; n = 6). The bolus dose of ACEA-1021 was followed by a continuous intravenous infusion of vehicle or ACEA-1021 at 14 mg *symbol* kg sup -1 *symbol* h sup -1. Halothane MAC was then determined by the tail-clamp method. In experiment 2, awake rats were randomly assigned to groups according to the same dosages of ACEA-1021 as in experiment 1. Arterial CO2 tension and mean arterial pressure were recorded before and 5 and 30 min after the start of the infusion. The infusion was then stopped, and the time to recovery of the righting reflex was recorded.
Results: In experiment 1, ACEA-1021 decreased halothane MAC (mean + SD) in a dose-dependent manner (control, 0.95 plus/minus 0.15 vol%; ACEA-1021 20 mg/kg, 0.50 plus/minus 0.14 vol%; ACEA-1021 40 mg/kg, 0.14 plus/minus 0.16 vol%; P < 0.01). In experiment 2, arterial CO2 tension was increased by ACEA-1021 (control, 38 plus/minus 3 mmHg; ACEA-1021 20 mg/kg, 43 plus/minus 3 mmHg; ACEA-1021 40 mg/kg, 48 plus/minus 2 mmHg; P < 0.01). Mean arterial pressure was not affected by any dose of ACEA-1021. The righting reflex was abolished in rats receiving ACEA-1021 40 mg/kg only and recovered 30 plus/minus 7 min after discontinuation of the infusion. 相似文献
Methods: In six human subjects, respiratory muscle activity in the parasternal intercostal, abdominal, and diaphragm muscles was measured using fine-wire electromyography electrodes. Chest wall motion was determined by respiratory impedance plethysmography. Electromyography activities and chest wall motion were measured during hyperpnea produced by carbon dioxide rebreathing while the subjects were awake and during 1 MAC halothane anesthesia.
Results: Halothane anesthesia significantly reduced the slope of the response of expiratory minute ventilation to carbon dioxide (from 2.88 plus/minus 0.73 (mean plus/minus SE) to 2.01 plus/minus 0.45 l *symbol* min sup -1 *symbol* mmHg sup -1). During the rebreathing period, breathing frequency significantly increased while awake (from 10.3 plus/minus 1.4 to 19.7 plus/minus 2.6 min sup -1, P < 0.05) and significantly decreased while anesthetized (from 28.8 plus/minus 3.9 to 21.7 plus/minus 1.9 min sup -1, P < 0.05). Increases in respiratory drive to the phrenic motoneurons produced by rebreathing, as estimated by the diaphragm electromyogram, were enhanced by anesthesia. Anesthesia attenuated the response of parasternal electromyography and accentuated the response of the transversus abdominis electromyography to rebreathing. The compartmental response of the ribcage to rebreathing was significantly decreased by anesthesia (from 1.83 plus/minus 0.58 to 0.48 plus/minus 0.13 l *symbol* min sup -1 *symbol* mmHg sup -1), and marked phase shifts between ribcage and abdominal motion developed in some subjects. However, at comparable tidal volumes, the ribcage contribution to ventilation was similar while awake and anesthetized in four of the six subjects. 相似文献