摘要:

To determine the effects of vasomotor tone on intrathoracic and splanchnic blood volume, the distribution of radioactively (99mTc) labeled erythrocytes was recorded by whole body scintigraphy before and during peridural anesthesia (PDA) in eight supine men. The radioactivity was recorded with a gamma camera and its distribution determined in the thorax, abdomen, and limbs. Arterial and central venous pressure, heart rate, and calf volume and flow also were measured. During PDA with a sensory block up to T4/5, radioactivity increased only in the denervated legs (+9.9 ± 2.3% SE), whereas it decreased in all other regions,i.e., in the thorax (-8.1 ± 1.2%), the innervated upper limbs (-10.6 ± 4.0%), and in the splanchnic vasculature (-5 ± 1.7%). However, in two of the subjects, after an initial decrease, splanchnic blood content increased while intrathoracic blood volume decreased further. The effects of PDA on thoracic and splanchnic filling could be duplicated by the sequestration of about 500–600 ml of blood in both legs. In supine humans, high peridural anesthesia evokes the same decrease in intrathoracic blood volume as orthostasis. This seems to be counteracted by a reflex decrease in filling of the denervated muscle and skin areas and also by a constriction of the splanchnic vasculature by an unknown mechanism. Potential circulatory collapse may ensue when the vasoconstrictor response fails in the splanchnic circulation.

ISSN:0003-3022    

出版商:OVID    

年代:1985

数据来源: OVID

摘要:

Inhalational anesthetics “fluidize” biologic membranes. Since arachidonate metabolism also occurs in cell membranes, anesthetic agents may modify arachidonic acid mediator production. The authors used the isolated perfused rabbit lung preparation to examine the effects of inhalational anesthetics on the production of arachi-donate mediators. The oxidant tert-butyl-hydroperoxide (t-bu-OOH) is known to cause pulmonary vasoconstriction by causing increased production of thromboxane A2(TxA2). The authors administered three anesthetics (halothane, cyclopropane, and nitrous oxide) of widely different potencies, at different dosages, each to three different groups of preparations and challenged the lungs at each anesthetic dose with t-bu-OOH. They found a dose-related augmentation of the pulmonary vasopressor response to t-bu-OOH. Preparations given t-bu-OOH alone showed no change in response over time. Lungs perfused with indomethacin (5 μg.ml-1in Krebs-Henseleit buffer), ventilated with cyclopropane (2 MAC), and challenged with t-bu-OOH showed almost complete inhibition of the response to t-bu-OOH. Indomethacin at this concentration is a specific inhibitor of cyclooxygenase. The authors also have demonstrated significantly increased perfusate levels of thromboxane B2(TxB2), the inactive metabolite of TxA2, after oxidant challenge during exposure to 2% halothane compared with TxB2levels before halothane exposure. The authors believe that the augmented pressor response and mediator production occur because of increased substrate (arachidonic acid) availability induced by anesthetic agent.

ISSN:0003-3022    

出版商:OVID    

年代:1985

数据来源: OVID

摘要:

Alterations in cerebral metabolic activity were measured after different doses of phenobarbital. Local cerebral glucose utilization was determined in 58 brain regions with the use of the [14C]deoxyglucose technique in 3-month-old Fischer 344 rats, at 1 h after the ip administration of saline or of phenobarbital. Whole brain glucose utilization declined in a dose-related manner by 4%, 13%, 33%, 35%, and 56% after phenobarbital 18, 60, 180, 300, and 600 mg/kg, respectively. The number of regions significantly affected (P< 0.05) increased from 7 to 95% of the regions examined between doses of 18 to 600 mg/kg. Metabolism decreased in all significantly affected regions except the interpeduncular nucleus, where it was increased. In a separate group of rats, the number of falls per 5 min from a constantly rotating cylinder was measured at subanesthetic doses of phenobarbital. Doses of drug that affected performance on the rotating cylinder (18 and 60 mg/kg) reduced glucose utilization in brain regions involved with motor performance, including the red nucleus, vestibular nucleus, substantia nigra, and deep layers of the superior colliculus, whereas cerebral cortical regions were not altered significantly. The results demonstrate that phenobarbital reduces cerebral glucose utilization, in a dose-dependent manner, in most brain regions and affects subcortical regions of the motor system significantly before reducing metabolism in the cerebral cortex.

ISSN:0003-3022    

出版商:OVID    

年代:1985

数据来源: OVID

摘要:

The authors examined the effects of positive end-expiratory pressure (PEEP) on cardiac function by dimensional analysis of the four heart chambers using M-mode transesophageal echocardiography (TEE). The accuracy of cardiac output (CO) calculated from TEE was confirmed by its close correlation (r = 0.97) with CO, determined by the thermodilution technique. The reliability of TEE also was confirmed by excellent correlation (r = 0.95) between left ventricular end-diastolic (LVEDD) and end-systolic (LVESD) dimensions measured by the two-dimensional precordial echocardiography and those by TEE. With 10 cmH2O PEEP LVEDD decreased from its level during zero end-expiratory pressure (ZEEP), and the calculated stroke volume also decreased. These decreases were greater during 15 cmH2O PEEP, where heart rate increased slightly but significantly. Ejection fraction (EF) and fractional shortening (FS), as a whole, did not change significantly. Mean velocity of circumferential fiber shortening (mean Vcf) significantly increased and LVESD significantly decreased with PEEP. Although systolic blood pressure (SBP) significantly decreased, the (SBP-PEEP value)/LVESD ratio was not changed with PEEP. Such measures of left ventricular systolic function as EF, FS, mean Vcf, and (SBP-PEEP value)/LVESD were not decreased. Right ventricular end-diastolic dimension decreased with PEEP. Right artrial end-diastolic dimension began to decrease immediately after PEEP was initiated, whereas left atrial end-diastolic dimension began to decrease a few seconds later, suggesting that left ventricular preload decreased as a result of a decrease in right ventricular preload. The authors therefore conclude that CO was decreased as a result of the decrease in right and left ventricular preloads.

ISSN:0003-3022    

出版商:OVID    

年代:1985

数据来源: OVID

摘要:

The authors performed a randomized, prospective trial comparing enflurane, halothane, and isoflurane (each administered with nitrous oxide) to establish which inhaled anesthetic produced the fewest complications and the most rapid induction of anesthesia for children undergoing general anesthesia for diagnostic procedures as oncology outpatients. Sixty-six children, ranging from 8 months to 18 years, underwent a total of 124 anesthetics. Induction of anesthesia (time from placement of facemask to beginning of skin preparation) was faster with halothane (2.7 ± 1.0 min, mean ± SD, n = 46) than with enflurane (3.2 ± 0.8 min, n = 43) or isoflurane (3.3 ± 1.2 min, n = 35). Emergence from anesthesia (time from completion of the procedure to spontaneous eye opening) was more rapid with enflurane (4.7 ± 4.4 min) than with halothane (6.2 ± 4.5 min) or isoflurane (6.2 ± 3.9 min). Total time from the start of procedure until discharge was longer with isoflurane (25.1 ± 6.8 min) than with enflurane (21.5 ± 8.6 min) or halothane (22.3 ± 7.6 min). During induction, the incidence of laryngospasm was greatest with isoflurane (23%) and the incidence of excitement least with halothane (13%). During the maintenance of, emergence from, and recovery from anesthesia, coughing occurred most frequently with isoflurane. During the recovery period, headache occurred most frequently with halothane (9%); there were no significant differences in the incidence of nausea, vomiting, hunger, or depressed effect. The authors conclude that the rapid induction and minimal airway-related complications associated with halothane anesthesia make it an excellent anesthetic agent for pediatric patients undergoing short diagnostic procedures.

ISSN:0003-3022    

出版商:OVID    

年代:1985

数据来源: OVID

摘要:

The effects of arterial blood pressure and heart rate on myocardial contraction were studied in a canine model of coronary stenosis. Systolic thickening of a region of myocardium supplied by a cannulated coronary artery was used as a measure of oxygen shortage. A glass stenosis in an external perfusion circuit that provided blood to the cannulated vessel was used to limit coronary flow. Mean arterial pressure was controlled by a blood reservoir and phenylephrine infusion and stabilized at four levels: 60, 80, 100, and 120 mmHg. At each blood pressure level, heart rate was increased by ventricular pacing in steps from 50 to 150 beats/min. Systolic thickening was measured at each of the resulting 20 combinations of blood pressure and heart rate. Measurements were made before cannulation, to serve as an unstenosed control, and following cannulation in the presence of moderate and severe stenoses. In the presence of the severe stenosis, ischemic dysfunction occurred when mean arterial pressure was decreased to 60 mmHg. At this pressure, dysfunction was most dramatic at rapid heart rates. In contrast, hypertension to a mean arterial pressure of 120 mmHg was well tolerated in these nonfailing hearts. Importantly, no single value of either blood pressure or heart rate was found to be associated with ischemia. The threshold for rate-induced ischemia depended on the coexisting value of blood pressure andvice versa.Ischemia was absent if mean arterial pressure exceeded heart rate, that is, if the pressure-rateratioexceeded one.

ISSN:0003-3022    

出版商:OVID    

年代:1985

数据来源: OVID

摘要:

The effects on fertility and reproductive wastage of 110 female Swiss/Webster mice and postnatal survival of their offspring were examined after exposure to either air, 0.4% isoflurane, or 0.1% isoflurane. Treatments were for 4 h daily for 2 weeks before and during pregnancy. In a second experiment, the effects on fertility of 54 male Swiss/Webster mice and on reproductive wastage of their unexposed mates were examined after 4-h daily exposures to either air, 0.4% isoflurane, or 0.1% isoflurane throughout spermatogenesis and during mating. There were no adverse reproductive effects in either experiment. The lack of toxicity of isoflurane is consistent with the results of other reproductive studies in animals that have examined chronic intermittent exposure to subanesthetic concentrations of halothane, enflurane, methoxyflurane, and nitrous oxide. They suggest that these and lower (trace) levels of anesthetic gases may not be the cause of the harmful reproductive effects said to occur in operating room personnel.

ISSN:0003-3022    

出版商:OVID    

年代:1985

数据来源: OVID

摘要:

The effects of halothane anesthesia on cardiopulmonary (low pressure) baroreflex control of peripheral resistance were studied in 10 ASA class I young men. Graded (-5,-7.5, −10, −12.5 mmHg) lower body negative pressure (LBNP) was used to produce progressive decreases in thoracic blood volume and central venous pressure. These stimuli activate reflexes from cardiopulmonary baroreceptors. Volunteers were studied while awake and during 1 MAC (0.75%) and 1.25 MAC (0.93%) halothane anesthesia. Hetastarch (6%) in 0.9% normal saline was infused into patients before baseline recordings were initiated. Blood pressure, stroke volume, cardiac output, and systemic and forearm vascular resistance decreased and forearm blood flow increased during halothane anesthesia. In awake subjects, LBNP did not alter heart rate or blood pressure, but stroke volume and cardiac output decreased. Blood pressure was maintained by cardiopulmonary baroreflex-mediated increases in peripheral resistance. In anesthetized subjects, decreases in stroke volume and cardiac output during LBNP were similar to awake responses, however, hypotension occurred because reflex resistance increases were markedly attenuated. The authors conclude that halothane anesthesia blunts cardiopulmonary baroreflex resistance responses provoked by mild decreases in thoracic blood volume in humans.

ISSN:0003-3022    

出版商:OVID    

年代:1985

数据来源: OVID

摘要:

The comparative effects of low doses (0.03–0.04 mg/kg) of epidural morphine on a nociceptive flexion reflex of the lower limb and on postoperative pain in volunteer patients were studied after orthopedic surgery on one knee. According to the stimulation parameters, it was found that 40–50 min after the injection, morphine produced an increase of 87% and 83% of the reflex threshold and of the threshold of maximal reflex response, respectively, as well as a 80–90% depression of the nociceptive responses when elicited by a constant level of stimulation. Onset of pain relief occurred by the 25th min and increased to a maximum stable level 40–50 min after the injection. These data support the hypothesis that the main site of the pain-relieving effect of epidural morphine is located directly at a spinal level.

ISSN:0003-3022    

出版商:OVID    

年代:1985

数据来源: OVID

摘要:

The authors studied effects of subanesthetic doses of the d- and 1-ketamine stereoisomers on maze performance in mice to determine whether the stereoisomers differed in their ability to disrupt a stable cognitive behavior. Twenty-four Swiss-Webster (CFW) mice were trained to stability in a four-compartment modular maze, using water as a reward. Each compartment contained a central partition with a barrier at the distal end of one of the two passageways. A fixed barrier-sequence was employed. Elapsed time to traverse all four compartments and total number of errors (the number of times a wrong compartment was entered) were measured. A cohort design was employed with the following four groups: saline control, d-ketamine, 1-ketamine, racemate. Two subanesthetic doses, 7.5 and 15 mg/kg of each form of the drug were given subcutaneously at five-day intervals. Both the d-isomer and the racemate significantly prolonged elapsed time at 15 mg/kg, the d-isomer having the greatest effect. The 1-isomer did not alter elapsed time at either dose but appeared to increase spontaneous locomotor activity after injection. Relative to errors, at the 7.5 mg/kg dose there were no changes from control with any form of ketamine. However, at the 15 mg/ kg dose, total errors significantly increased both with the racemate and the d-isomer. The performance decrements observed with the racemate appear to be attributable largely to the d-component.

ISSN:0003-3022    

出版商:OVID    

年代:1985

数据来源: OVID