Anesthesiology
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Randomized Controlled Trial Comparative Study Clinical Trial
Combined epidural and general anesthesia versus general anesthesia for abdominal aortic surgery.
The goal of this randomized study of high-risk surgical patients was to determine whether intraoperative thoracic epidural anesthesia in combination with light general anesthesia alters postoperative morbidity when compared to a standard technique of "balanced" general anesthesia. A total of 173 patients scheduled for abdominal aortic reconstruction were admitted to the study; 86 were to receive "balanced" general anesthesia (group 1) and 87 thoracic epidural anesthesia in combination with light general anesthesia (group 2). Preoperative evaluation included standard clinical tools, dipyridamole thallium gammatomography, and radionuclide angiography. ⋯ In group 2, 6 patients with a nonfunctioning epidural catheter due to technical failure received a balanced general anesthesia and were eliminated from the study. During the postoperative period, group 2 received analgesia of subcutaneous morphine (n = 26), epidural fentanyl (n = 25), or epidural bupivacaine (n = 30). Cardiovascular morbidity did not differ between the two groups: 22 patients in group 1 and 19 patients in group 2 had a major postoperative cardiac event.(ABSTRACT TRUNCATED AT 250 WORDS)
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Differences in cerebral blood flow (CBF) between alpha-stat and pH-stat management depend on preserved responsiveness of the cerebral vasculature to changes in arterial carbon dioxide tension (PaCO2). We tested the hypothesis that hypothermia-induced reductions in CBF would decrease the CBF response to changing PaCO2 (delta CBF/delta PaCO2). Anesthetized New Zealand white rabbits were randomly assigned to one of three temperature groups--group 1 (37 degrees C, n = 9); group 2 (31 degrees C, n = 10); or group 3 (25 degrees C, n = 10)--and were cooled using cardiopulmonary bypass. ⋯ Prior normothermic studies have found delta CBF/delta PaCO2 to be proportional to CBF. Nevertheless, in this study, with hypothermia-induced reductions in CBF, delta CBF/delta PaCO2 was not significantly different between temperature groups. Thus, hypothermia either increased the sensitivity of the cerebral vasculature to carbon dioxide and/or increased the effective level of cerebrospinal fluid respiratory acidosis produced by each increment of temperature-corrected PaCO2.(ABSTRACT TRUNCATED AT 250 WORDS)
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Maldistribution of local anesthetic administered through a subarachnoid catheter recently has been implicated as a possible cause of sacral root injury. To examine subarachnoid distribution of catheter-injected local anesthetic, we constructed a model of the subarachnoid space and administered solutions containing lidocaine and methylene blue through sacrally directed catheters. We studied three catheters: a 28-G endport, a 20-G endport, and a 20-G multiple sideport. ⋯ Differences in peak lidocaine concentration between the two 20-G catheters were neither large nor consistent. However, despite sacral placement, the multiple-sideport catheter distributed anesthetic toward "higher" spinal segments more consistently. Distribution was more favorable when the injected solution was less dense (closer to isobaric).(ABSTRACT TRUNCATED AT 250 WORDS)
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It has been hypothesized recently that succinylcholine-associated increases in intracranial pressure (ICP) are caused by the paraben preservatives contained in multidose vials. We tested that hypothesis in a standard feline model to determine the effects on ICP of equal-volume injections of preservative-free succinylcholine, succinylcholine with preservatives from multi-dose vials that contain both propylparaben and methylparaben, these preservatives alone at five times the dose contained in the succinylcholine, and normal saline. The preservatives alone increased ICP by 0.08 +/- 0.08 mmHg (+/- standard error; not significant). ⋯ Preservative-free succinylcholine and succinylcholine with preservatives increased ICP by 4.2 +/- 0.10 and 3.8 +/- 0.07 mmHg respectively (P less than 0.01 compared to the preservatives alone and normal saline). The 99% upper confidence limit for the increase in ICP induced by the preservatives alone was 0.42 mmHg. This result suggests that parabens do not cause or substantially augment the ICP increase associated with succinylcholine administration.
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To demonstrate that sympathetic responses transmitted by the splanchnic nerve help maintain intravascular stability, 12 mongrel dogs (35-45 kg each), anesthetized with pentobarbital, were given two separate but identical hypotensive stimuli (mean arterial blood pressure of 60 mm Hg for 15 min) by the withdrawal of appropriate amounts of blood. The first stimulus was performed in the absence of drug or surgical manipulation. The second stimulus was performed after animals were subjected to no intervention (n = 4), bilateral splanchnic nerve section (n = 4), or spinal anesthesia (n = 4). ⋯ The volume of blood withdrawn to produce hypotension was similar (approximately 21 ml.kg-1). Bilateral splanchnic nerve section attenuated the adrenal medullary blood flow, arterial epinephrine concentration, and abdominal organ blood flow responses to hypotension by 86, 64, and 66%, respectively (P less than 0.008), and the blood volume withdrawn was reduced by 42% (P less than 0.02). Spinal anesthesia eliminated the adrenal medullary blood flow response to hypotension, attenuated the arterial epinephrine concentration and abdominal organ blood flow responses by 78 and 57%, respectively (P less than 0.01), and decreased the blood volume extracted by 55% (P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)