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Query: UMLS:C0278134 (anesthesia)
 110,339 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In halothane-anesthetized dogs, a decrease in baroreflex sensitivity (BRS) of approximately 20% was observed during the reperfusion period following 5-min global cerebral ischemia. When compared with our previous study on animals under pentobarbital anesthesia, the extent of the decrease in BRS was smaller and apparently more severe ischemia was necessary to damage the vagal component of the baroreflex. Substitution of halothane with pentobarbital during the reperfusion period failed to affect either BRS or the ratio of the vagal component. In another group, pre- and post-ischemic measurements of BRS was performed under halothane anesthesia, but the ischemic insult was given under thiopental anesthesia. In these animals, the extent of decrease in BRS (about 50%) was greater than that in animals subjected to ischemia under halothane anesthesia. The present results suggest that the anesthetics used during the ischemic insult may affect the extent of post-ischemic dysfunction of the baroreflex. The vagal component of the baroreflex may be more resistant to ischemia under halothane anesthesia than under barbiturate anesthesia.
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PMID:Difference between halothane and barbiturate anesthesia in the influence of cerebral ischemia on the vagal baroreflex in dogs. 151 75

The effects of varying concentrations and types of volatile anesthetics on neurochemical sequelae of brain ischemia were evaluated in the rat. Rats were assigned to treatment defined by a 3 x 3 design (anesthetic type and dose) with 5 rats/cell. Each group received halothane, enflurane, or isoflurane 0.5, 1.0, or 2.0 MAC (minimal alveolar concentration). This was followed by preischemic plasma glucose sampling, 5 min hypotension (30 mmHg) and 5 min decapitation cerebral ischemia. Preischemia plasma glucose increased with increasing anesthetic concentration and was highest in the isoflurane groups, varying from a low (+/- SD) of 7.19 +/- 1.79 mumol/ml in the 0.5 MAC halothane group to a high of 12.68 +/- 3.65 mumol/ml in the 2.0 MAC isoflurane group. End-ischemic brain lactate correlated with preischemic plasma glucose (r = 0.5, alpha = 0.5). We conclude that increasing concentration of volatile anesthesia with iv phenylephrine blood pressure support produces higher levels of plasma glucose and brain lactate with cerebral ischemia.
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PMID:Comparison of the effects of volatile anesthetics in varying concentrations on brain energy metabolism with brain ischemia in rats. 151 13

Quantitative methods to measure ocular glucose consumption in vivo, which is dominated by the retina, could provide considerable information about retinal metabolism in healthy and disease states. Eyes that are totally ischemic for at least 4 hr retain good retinal histopathologic features if treated with vitreoperfusion. In such cases, the vitreoperfusion fluid essentially is the only extraretinal source of glucose. We developed a mathematical model to estimate the rate at which glucose is extracted from the vitreoperfusion solution by metabolism (Eglu), compensating for losses via the outflow pathways. With a glass model eye (Eglu = 0) with a known, simulated outflow facility, the measured decline in glucose closely approximated the decline predicted by the equation (r = 0.97). In six formaldehyde-glutaraldehyde fixed cat eyes (Eglu = 0), the measured vitreous glucose concentrations at various times correlated with the calculated values (r = 0.96). With the use of general anesthesia, lensectomy and vitrectomy were performed in 10 cat eyes. Vitreoperfusion was initiated, and the cats were killed to establish total ocular ischemia. The mean +/- SD Eglu values for intervals between 15 and 75, 105 and 165, and 195 and 255 min after ischemia were 8.0 +/- 6.9, 14.4 +/- 10.4, and 19.9 +/- 11.0 micrograms/min, respectively (P less than .05). We conclude that the eyes retained their ability to extract glucose for at least 4 hr but that Eglu values increased during this period for undetermined reasons. In the future, measurements of Eglu may become useful in the evaluation of physiologic and pathologic states of the eye.
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PMID:Ocular glucose extraction using vitreoperfusion in the cat. 152 28

Overstimulation of the N-methyl D-aspartate (NMDA) receptor has been implicated as a factor in the pathogenesis of ischemic injury in the central nervous system. The present study was undertaken to determine whether ketamine hydrochloride, a potent NMDA antagonist, could attenuate ischemic injury in the rabbit retina. Retinal ischemia was induced for 60 min in one eye of 18 albino rabbits by raising intraocular pressure above the systolic blood pressure. Three concentrations of ketamine, 0.5, 1.5, 5.0 mumol were dissolved in 20 microliters of saline solution and injected in the midvitreous in each eye of 14 rabbits 1 hr prior to ischemia. Four rabbits received saline solution as controls. The scotopic electroretinogram was monitored in each eye to assess the postischemic recovery of retinal function. A statistically significant reduction in the b-wave was detected in the eyes treated with saline (P less than 0.05), whereas the postischemic recovery of b-wave amplitude was enhanced by pretreatment with lower doses of ketamine. The highest dose depressed b-wave amplitude regardless of ischemia. Six rabbits underwent unilateral ocular ischemia under general anesthesia with ketamine. A small ameliorative effect was seen (P = 0.029). These results suggest that ketamine may alleviate ischemic injury in the rabbit retina, presumably by antagonizing the NMDA receptor-mediated toxicity. Thus, ketamine may have potential in the treatment of retinal vascular occlusive diseases. Moreover, a modified ischemic state may exist in experiments on ischemia conducted under general anesthesia with ketamine hydrochloride.
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PMID:Ketamine suppresses ischemic injury in the rabbit retina. 153 93

Hemodynamic changes were studied during two different anesthetic techniques in 54 patients undergoing coronary artery bypass grafting (CABG). All patients had normal to moderately impaired left ventricular function and were randomly assigned to two groups. In 27 patients, high thoracic epidural analgesia (TEA) with bupivacaine 0.375% plus sufentanil 1:200,000 (ie, 5 micrograms/mL) was used in combination with general anesthesia with midazolam/N2O; in the other 27 patients, general anesthesia (GA) with midazolam and sufentanil was used. After induction of epidural analgesia, heart rate and mean arterial pressure (MAP) decreased. Changes in cardiac index, systemic vascular resistance, and pulmonary capillary wedge pressure were not observed, whereas the stroke volume index increased significantly. After induction of intravenous anesthesia MAP decreased (20%) in both groups. During the pre-bypass period, metaraminol was used in 7 of 27 patients in the GA group and in 5 of 27 patients in the TEA group to treat hypotension. Inotopic drugs were used in 5 patients in the GA group and in none in the TEA group to treat a low CO. Ten GA patients and 4 TEA patients developed hypertension after sternal spread and the GA patients required more nitroprusside. Four GA patients developed electrocardiographic evidence of prebypass ischemia and, therefore, more nitroglycerin was needed for treating myocardial ischemia. More sodium nitroprusside was needed in the GA group during cardiopulmonary bypass (CPB) and the post-bypass period to treat hypertension with a high SVR. In conclusion, hemodynamic stability was more pronounced in the TEA than the GA group before and after CPB.
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PMID:Coronary artery bypass grafting using two different anesthetic techniques: Part I: Hemodynamic results. 847 38

Desflurane, a coronary vasodilator, may induce myocardial ischemia in patients with coronary artery disease. To determine whether desflurane is safe to administer to the at-risk patient population (with known coronary artery disease), we compared the incidence and characteristics of perioperative myocardial ischemia in 200 patients undergoing coronary artery bypass graft (CABG) surgery randomly assigned to receive desflurane (thiopental adjuvant) versus sufentanil anesthesia. Under conditions of hemodynamic control, perioperative ischemia was assessed using continuous echocardiography (precordial: during induction; transesophageal: during surgery) and Holter electrocardiography (ECG); hemodynamics (including pulmonary artery pressure) were measured continuously. Hemodynamic results: During induction, no significant changes in hemodynamics occurred in the sufentanil group, while in the desflurane group, heart rate, systemic and pulmonary arterial pressure increased and stroke volume decreased significantly. During the intraoperative period, the incidence of hemodynamic variations was low in both anesthetic groups; however, the prebypass incidence of tachycardia (greater than 120% of preoperative baseline heart rate) was greater in the desflurane group (4 +/- 7% of total time monitored) than in the sufentanil group (1 +/- 6%) (P = 0.0003). Similarly, the incidence of prebypass hypotension (less than 80% of preoperative baseline systolic arterial blood pressure) was greater in the desflurane group (21 +/- 14%) than in the sufentanil group (15 +/- 16%) (P = 0.01). ECG results: Preoperatively, 15% (28/191) of patients developed ECG ischemia, with no difference between patients who received desflurane, 13% (12/96) or sufentanil, 16% (16/95) (P = 0.6). During anesthetic induction, 9% (9/99) of patients who received desflurane developed ECG ischemia, compared with 0% (0/98) who received sufentanil (P = 0.007). During the prebypass period, 5% (10/197) of patients developed ECG ischemia, with no difference between patients who received desflurane, 7% (7/99) or sufentanil, 3% (3/98) (P = 0.3). Postbypass, 12% (24/194) of patients developed ECG ischemic changes, with no difference between patients who received desflurane, 13% (13/97) or sufentanil, 11% (11/96) (P = 0.9). Echocardiographic results: The incidence of precordial echocardiographic ischemia during anesthetic induction was 13% (5/39) in the desflurane group versus 0% (0/29) in the sufentanil group (P = 0.1). Moderate to severe transesophageal echocardiographic (TEE) ischemic episodes occurred in 12% (21/175) of patients during prebypass, with no significant difference between the desflurane group, 16% (15/91) and the sufentanil group, 7% (6/84) (P = 0.09). TEE ischemic episodes occurred in 27% (49/178) of patients during the postbypass period, with no difference between the desflurane, 29% (27/92) and sufentanil, 25% (22/86) groups (P = 0.7).(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:The risk of myocardial ischemia in patients receiving desflurane versus sufentanil anesthesia for coronary artery bypass graft surgery. The S.P.I. Research Group. 843 40

Visceral C fibers are stimulated by ischemia and hypoxia, which can be produced by intense vasoconstriction. Epinephrine applied to the gastric submucosa produces a marked vasoconstriction followed by autoregulatory escape. We hypothesize that the autoregulatory escape from epinephrine-induced vasoconstriction in the rat stomach is mediated partly by capsaicin-sensitive C fibers. Functional ablation of these afferent fibers by high-dose systemic capsaicin pretreatment will significantly reduce the magnitude of the autoregulatory escape. Rats received capsaicin (125 mg/kg sc) 10 days before blood flow studies to produce functional impairment of the capsaicin-sensitive afferent nerves. Control rats received vehicle. Under urethan anesthesia, a small area (2 mm diam) of the serosa from the anterior gastric wall was removed to expose the submucosa. The tip of a side-viewing laser-Doppler flow probe was placed inside the stomach directly beneath the exposed submucosa. At 20-min intervals, 20 microliters of buffer, 5 x 10(-4) M epinephrine, 1.6 x 10(-4) M capsaicin, or 3.3 x 10(-2) M histamine was applied topically to the exposed submucosa, with saline washes between applications at 10 min after each application. Blood pressure and laser-Doppler flow signals were monitored continuously. The escape index during the period of epinephrine application was significantly lower in the capsaicin-pretreated rats (0.239 +/- 0.046) than in the vehicle-pretreated rats (0.474 +/- 0.079). Functional ablation of the capsaicin-sensitive afferent fibers was confirmed by a significant blockade of the vasodilatation induced by topical capsaicin. Histamine-induced vasodilatation was unaffected.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Modulation of autoregulatory escape by capsaicin-sensitive afferent nerves in rat stomach. 153 16

The arterial resistometer provides continuous on-line monitoring of changes in arterial resistance. Resistance index (Ri), which bears a direct relationship to systemic vascular resistance (SVR), is defined by the equation Ri = P'/(dP'/dt), where dP'/dt is the peak dP/dt of the arterial waveform, and P' is the pressure at dP'/dt. In 42 patients with unstable angina, changes in Ri were studied at six periods during aortocoronary bypass surgery before tracheal intubation, during tracheal intubation, leg elevation, presternotomy, sternotomy, and dissection of the internal mammary artery. Thirty-four episodes of ischemia (0.1 mV ST segment changes) were observed in 26 patients. All ischemic episodes were associated with increased Ri (mean increase, 102 +/- 52%). Elevation of the pulmonary capillary wedge pressure correlated with ischemia during the preintubation, intubation, and sternotomy periods, but not in the remaining periods. Changes in arterial pressure and heart rate were not good predictors of ischemia. The prevalence of ST segment changes increased markedly during all periods of anesthesia with increase in Ri (P less than 0.05). Ninety-one percent of ST segment changes were associated with a 25% increase from the baseline Ri. Raising the cutoff point to a greater than or equal to 75% increase in Ri improved the specificity of Ri in ischemia detection from 61% to 92%. An increase of greater than or equal to 75% in Ri occurred in only 8% of cases without ST segment changes. It was found that an increase in Ri as depicted by the arterial resistometer was the best hemodynamic correlate of myocardial ischemia.
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PMID:Correlation between myocardial ischemia and changes in arterial resistance during coronary artery bypass surgery. 154 51

Perioperative myocardial ischemia predicts unfavorable outcomes and occurs in as many as 41% of patients with coronary artery disease or cardiac risk factors undergoing noncardiac surgery. To determine the prevalence of myocardial ischemia, we studied 52 consecutive unselected patients undergoing elective hip arthroplasty during lumbar regional anesthesia. Patients were continuously monitored for 6 days using a three-channel Holter monitor. Ninety-nine episodes of myocardial ischemia occurred in 16 patients (31%), six of whom were considered preoperatively to be at low risk for coronary artery disease. Forty-four percent of the ischemic episodes were preceded or accompanied by a heart rate greater than or equal to 100/min and 56% by a heart rate greater than or equal to 90 beats/min. Ninety-six percent of the ischemic episodes were clinically silent, and 82% were not related to patient care events. Thirteen episodes of myocardial ischemia occurred preoperatively, 1 intraoperatively, and 85 postoperatively. The incidence of postoperative ischemic episodes showed a circadian variation: 44% occurred between 6 AM and noon, 33% between noon and 6 PM, 17% between 6 PM and midnight, and 6% between midnight and 6 AM. Six adverse cardiac events occurred during hospitalization (three of the six among patients with perioperative ischemia) and an additional four events during a follow-up period of 12 months (all four events occurred among patients with perioperative ischemia). Patients with perioperative myocardial ischemia had a relative risk of 2.6 (95% confidence interval 1.3-5.2) to develop an adverse cardiac event postoperatively.
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PMID:Perioperative myocardial ischemia in patients undergoing elective hip arthroplasty during lumbar regional anesthesia. 155 Feb 76

In order to characterize intraorgan differences in blood supply of the rat liver, hepatic blood flow (HBF), surface oxygen tension (sPO2) and glycogen content of the largest and smallest lobi have been determined for normal and hemorrhagic rats (N = 68) in ketamin-xylazine anesthesia. 1. Mean HBF +/- SD of lobus sinister measured 1.07 +/- 0.23 ml/g min (n = 119 determinations, N = 9 rats); HBF of lob. caudatus dexter showed a left-shifted histogram (mean value = 0.77 ml/g.min, median = 0.72 ml/g.min, modul = 0.63 ml/g.min, p less than 0.005). 2. Mean sPO2 +/- SD of lob. sin. measured 23 +/- 6.8 mm Hg (n = 168, N = 16). The histograms of lob. caudat. dext. and sin. were left-shifted (mean value of l.c.d. = 9 mm Hg, median = 4 mm Hg, modul = 0 mm Hg, mean value of l.c.s. = 16 mm Hg, median = 17 mm Hg, modul = 0 mm Hg). Under hemorrhage sPO2 became almost zero in 91% of the measurements. 3. In response to an arterial bolus of fluorescence stained gamma-globulins, spreading of the dye showed a pronounced front and marked periportal area within lob. sin., while an irregular convective front and a much smaller area were detected within both of the lobi caudati. Under hemorrhage, intersinusoidal staining and undefined, irregular contours were observed within all lobes. 4. Compared with lob. sin. preferential glycogen depletion and partial centrilobular necrosis were detected within both of the lob. caudati while under hemorrhage the glycogen stores were empty and severe group necroses have been observed especially within the small lobi. From the data it is concluded that in comparison to lob. sin. an insufficient supply and pronounced vulnerability against hepatic ischemia exists within the small lobi caudati.
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PMID:Intraorgan differences of blood flow, oxygen supply and glycogen content in the multilobular liver of normal and hemorrhagic rats. 155 16


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