Anesthesiology
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The authors tested the extent to which thermoregulatory vasoconstriction decreases cutaneous heat loss during isoflurane anesthesia. Thermoregulatory vasoconstriction was provoked by central hypothermia in five nonsurgical volunteers given isoflurane anesthesia. Peripheral arteriovenous shunt flow was quantified using forearm-fingertip skin-surface temperature gradients and volume plethysmography. ⋯ Heat loss from the trunk and head decreased only 14%; in contrast, loss from the hands and feet decreased approximately 57%. There were no clinically important changes in blood pressure or heart rate during vasoconstriction, but oxyhemoglobin saturation (measured by pulse oximetry) increased slightly. These data suggest that thermoregulatory vasoconstriction only minimally decreases cutaneous heat loss.
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Comparative Study
Spinal cord stimulation evoked potentials during thoracoabdominal aortic aneurysm surgery.
Although monitoring of somatosensory evoked potentials elicited from stimulation of lower extremity peripheral nerves has been suggested as a method for assessing neural function during thoracoabdominal aortic aneurysm surgery, this technique has been reported to yield a large number of false positives. It was believed that direct stimulation of the spinal cord would eliminate some of the problems associated with peripheral evoked potentials. The present study compared in 18 patients the use of scalp recorded evoked potential following stimulation of either the posterior tibial nerve via percutaneous needles or the spinal cord via an epidural electrode previously placed fluoroscopically. ⋯ Loss of spinal cord stimulation evoked potentials was found to be correlated with adverse neurologic outcome. Over the period of aortic clamping a gradual decrease in mean amplitude (50% at 45 min [P less than 0.05]) and a 20% increase in mean latency time were observed. Maintenance of adequate distal perfusion may permit the use of peripheral evoked potentials in the assessment of spinal cord ischemia during aortic cross-clamping.(ABSTRACT TRUNCATED AT 250 WORDS)
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Comparative Study
Sympathetic responses to induction of anesthesia in humans with propofol or etomidate.
Anesthetic induction with propofol commonly results in hypotension. This study explored potential mechanisms contributing to hypotension by recording cardiovascular responses including sympathetic neural activity from patients during induction of anesthesia with propofol (2.5 mg.kg-1 plus 200 micrograms.kg-1.min-1) or, for comparison, etomidate (0.3 mg.kg-1 plus 15 micrograms.kg-1.min-1). Twenty-five consenting, nonpremedicated, ASA physical status 1 and 2, surgical patients were evaluated. ⋯ Both cardiac and sympathetic baroslopes were maintained with etomidate but were significantly reduced with propofol, especially in response to hypotension. These findings suggest that propofol-induced hypotension is mediated by an inhibition of the sympathetic nervous system and impairment of baroreflex regulatory mechanisms. Etomidate, conversely, maintains hemodynamic stability through preservation of both sympathetic outflow and autonomic reflexes.
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Randomized Controlled Trial Clinical Trial
The use of oral mexiletine for the treatment of pain after peripheral nerve injury.
Neuropathic pain is often a difficult condition to treat. Clinical and laboratory studies using intravenously administered local anesthetics or antiarrhythmic agents support the use of these drugs for the treatment of neuropathic pain. The availability of the oral antiarrhythmic medication, mexiletine, has made it possible to study the effects of an orally administered medication on chronic neuropathic pain. ⋯ Median pain scores prior to mexiletine were 7, after placebo treatment 7, and while receiving mexiletine (750 mg/day) 4. Side effects were mild and well-tolerated. Mexiletine may be effective in reducing neuropathic pain for patients in whom alternative pain medications have been unsatisfactory.
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Randomized Controlled Trial Clinical Trial
Three posterior percutaneous celiac plexus block techniques. A prospective, randomized study in 61 patients with pancreatic cancer pain.
Variations and refinements of the classic retrocrural technique of neurolytic celiac plexus block (NCPB) for pancreatic cancer pain (PCP) have been proposed over the last 30 yr to improve success rates, avoid complications and enhance diagnostic accuracy. The aim of this prospective, randomized study was to assess the efficacy and morbidity of three posterior percutaneous NCPB techniques in 61 patients with PCP. The 61 patients were randomly allocated to three NCPB treatment groups: group 1 (20 patients, transaortic plexus block); group 2 (20 patients, classic retrocrural block); and group 3 (21 patients, bilateral chemical splanchnicectomy). ⋯ Operative mortality was nil with the three techniques and morbidity negligible. NCPB abolished celiac PCP in 70-80% of patients immediately after the block and in 60-75% until death. Because celiac pain was only a component of PCP in all patients, especially in those with a longer time course until death: 1) abolition of such pain did not ensure high percentages of complete pain relief (immediate pain relief in 40-52%; pain relief until death in 10-24%); 2) NCPB was effective in controlling PCP in a higher percentage of cases if performed early after pain onset, when the pain was still only or mainly of celiac type and responded well to nonsteroidal antiinflammatory drug therapy; and 3) the probability of patients remaining completely pain-free diminished with increased survival time.(ABSTRACT TRUNCATED AT 250 WORDS)