Anesthesia and analgesia
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Anesthesia and analgesia · Jun 2004
Comparative StudyMorphine-induced analgesia, hypotension, and bradycardia are enhanced in hypertensive rats.
Several studies have emphasized an opioidergic link between the central regulation of cardiovascular function and acute noninflammatory pain. By contrast, relatively few studies have investigated the relationships between opioids, hypertension, and inflammatory pain. We used the formalin model of acute inflammatory pain to compare morphine antinociception among spontaneously hypertensive (SHR) rats, their genetic normotensive controls, Wistar-Kyoto (WKY) rats, and Sprague-Dawley (SD) rats. Measures of nociception included both behavioral and cardiovascular end-points (increased mean arterial blood pressure and heart rate). Morphine (3.0 mg/kg subcutaneously) produced greater hypotension and bradycardia in SHR than in WKY or SD rats. We next administered formalin (5%; 50 microL) and observed greater nociception during both Phase 1 and Phase 2 in SHR controls than in WKY controls. The morphine-treated groups did not differ, suggesting that morphine attenuates hypersensitivity to formalin pain in the SHR. Morphine inhibited edema but not paw hyperthermia to a greater degree in SHR, whereas Phase 1 remifentanil produced a relatively shorter delay in the onset of Phase 2 in SHR. We suggest that the presentation of essential hypertension be considered when opioid regimens are planned both during surgery (to minimize cardiovascular complications) and during the postoperative period (to optimize analgesic effects). ⋯ Presentation of essential hypertension should be considered when opioid regimens are planned both during surgery (to minimize cardiovascular complications) and during the postoperative period (to optimize analgesic effects).
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Anesthesia and analgesia · Jun 2004
Comparative StudyA specific alteration in the electroretinogram of Drosophila melanogaster is induced by halothane and other volatile general anesthetics.
In higher organisms, physiological investigations have provided a valuable complement to assays of anesthetic effects on whole-animal behavior. However, although complex motor programs of Drosophila melanogaster have been used to identify genes that influence anesthesia, electrophysiological studies of anesthetic effects in this invertebrate have been limited. Here we show that the electroretinogram (ERG), the extracellular recording of light-evoked mass potentials from the surface of the eye, reveals a distinct effect of halothane, enflurane, isoflurane, and desflurane. Behaviorally relevant concentrations of these volatile anesthetics severely reduced the transient component of the ERG at lights-off. Other prominent ERG components, such as the photoreceptor potential and the lights-on transient, were not consistently affected by these drugs. Surprisingly, for most anesthetics, a diminished off-transient was obtained only with short light pulses. An identical effect was observed in the absence of anesthetic by depressing the function of Shaker potassium channels. The possibility that halothane acts in the visual circuit by closing potassium channels was examined with a simple genetic test; the results were consistent with the hypothesis but fell short of providing definitive support. Nevertheless, our studies establish the ERG as a useful tool both for examining the influence of volatile anesthetics on a simple circuit and for identifying genes that contribute to anesthetic sensitivity. ⋯ Electroretinography (ERG) provides a useful monitor of anesthetic effects on the fruit fly. The effects of volatile anesthetics on the ERG are recapitulated by inactivation of potassium channels.
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Anesthesia and analgesia · Jun 2004
Case ReportsPressure sore as a complication of labor epidural analgesia.
Lumbar epidural analgesia has become a common mode of pain control for laboring patients. Side effects, such as hypotension, motor blockade, respiratory depression, dural puncture, and urinary retention, are well described. Although pressure sores have been thought of as a complication limited to elderly, emaciated, unconscious, or bedridden patients, we describe the occurrence of pressure sores in a young and healthy parturient after lumbar epidural analgesia. ⋯ We report a pressure sore that resulted from lumbar epidural analgesia for labor.
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Anesthesia and analgesia · Jun 2004
Enhanced vasodilatory responses to milrinone in catecholamine-precontracted small pulmonary arteries.
Beta-adrenergic agonists (e.g., epinephrine [E] and norepinephrine [NE]) and phosphodiesterase-III inhibitors (e.g., milrinone) are often used in combination to augment ventricular function in the perioperative period. In the myocardium, milrinone acts synergistically with beta-adrenergic agonists to increase contractility. However, the potential interaction between catecholamines with combined alpha- and beta-adrenergic activity and milrinone in the pulmonary circulation has not been determined. We evaluated the vasodilatory effects of milrinone and nitroglycerine on large elastic and small muscular porcine pulmonary vascular rings precontracted with catecholamines with beta-adrenergic agonist activity (E and NE), the alpha-adrenergic agonist phenylephrine, and a nonadrenergic agonist, the thromboxane analog U46619. In small pulmonary arteries, the vasorelaxation with milrinone was significantly enhanced in rings precontracted with E or NE compared with those precontracted with phenylephrine or U46619. However, in large pulmonary arteries, the vasorelaxation with milrinone was similar in all vessel rings and was not influenced by the agonist used to induce precontraction. In marked contrast, the vasorelaxant responses to nitroglycerine were not altered by the specific agonist used for precontraction in either small or large pulmonary vascular rings. Thus, the pulmonary vascular effects of milrinone are enhanced when combined with drugs with beta-adrenoreceptor agonist activity. The vasodilatory interactions exhibited by phosphodiesterase-III inhibitors and the catecholamines NE and E suggest that their combined use might be beneficial in circumstances in which ventricular dysfunction and increased pulmonary vascular resistance occur. ⋯ This study demonstrated that milrinone had enhanced vasodilator effects when combined with drugs with beta-adrenoreceptor agonist activity in small pulmonary artery segments removed from pigs.
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Anesthesia and analgesia · Jun 2004
Bispectral index during isoflurane anesthesia in pediatric patients.
Bispectral index (BIS) was developed to monitor anesthetic depth in adults, but has been investigated for use in children, using sevoflurane. We examined the concentration-response relationship between BIS and isoflurane. Thirty children undergoing cardiac catheterization received continuous intraoperative BIS monitoring and had BIS values recorded at 6 steady-state end-tidal isoflurane (Et(Iso)) concentrations between 1.5% and 0.5% and at first arousal. The mean (SD) values for BIS were as follows: 1.5%, 32.3 +/- 11.7; 1.3%, 34.7 +/- 12.5; 1.1%, 40.5 +/- 13.3; 0.9%, 48.0 +/- 13.7; 0.7%, 55.9 +/- 14.4; and 0.5%, 61.8 +/- 13.1. There was an inverse correlation between Et(Iso) and BIS (r = -0.634; P < 0.01). There were significant differences (P < 0.0001) in mean BIS values between adjacent Et(Iso) in all cases except 1.5% versus 1.3%. An inhibitory sigmoid E(max) model best described the BIS-isoflurane concentration relationship, with an 50% effective dose of 0.85% (95% confidence interval, 0.72%-0.98%). The mean value of BIS at first arousal was 78.5 +/- 12.3. The relationship between Et(Iso) and BIS is qualitatively and quantitatively similar to that described for isoflurane in adults and sevoflurane in children. These results add to the body of evidence that BIS is adequately calibrated for use in children older than 1 yr. ⋯ This observational study of children undergoing cardiac catheterization characterizes the concentration-response relationship between bispectral index and isoflurane and demonstrates that bispectral index seems adequately calibrated for monitoring the depth of isoflurane anesthesia in pediatric patients.