Anesthesia and analgesia
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Anesthesia and analgesia · Aug 1998
Randomized Controlled Trial Clinical TrialShould adult patients drink fluids before discharge from ambulatory surgery?
We studied 726 consenting patients to determine whether withholding oral fluids from adult ambulatory surgical patients before discharge would decrease the incidence of postoperative nausea and vomiting (PONV) and shorten the duration of stay in the ambulatory surgery unit (ASU). Patients were randomly assigned to the drinking or nondrinking group. Both groups received a standard regimen of general anesthesia, fluid replacement, and analgesia. In the ASU, patients in the drinking group were given mandatory oral fluids to drink before discharge. Nausea and pain were assessed by using a visual analog scale 15, 30, 60, 90, 105, 120, 150, and 180 min postoperatively. The time to drink, sit up, void, and ambulate, and the time until discharge were recorded. Patients were interviewed by telephone 24 h postoperatively. There was no significant difference in the frequency of PONV between the drinking and the nondrinking groups either in the hospital or after discharge. Patients in the drinking group required more time to begin ambulating (105 +/- 38 vs 98 +/- 34 min; P < 0.02) and to void (112 +/- 40 vs 105 +/- 37 min; P < 0.01). Patients in the drinking group also stayed in the ASU longer (85 +/- 49 vs 81 +/- 47 min; P < 0.03). Time to postanesthetic discharge was also significantly longer in the drinking group than the nondrinking group (106 +/- 40 vs 98 +/- 36 min; P < 0.015). A similar percentage of patients in both groups were "very satisfied" with their ambulatory surgical care. There was no difference in postoperative complications and need for medical help. Withholding early postoperative oral fluids facilitated earlier ambulation and decreased the stay in the ASU but did not decrease the incidence of PONV. Thus, in this ambulatory surgical population, there does not seem to be justification to require drinking before discharge. ⋯ To answer the question of whether adult outpatients should drink before discharge after minor surgical procedures, 726 patients were randomized to either drink approximately 150 mL of liquid or not to drink. Neither drinking nor nondrinking worsened postoperative nausea or vomiting or prolonged hospital stay. Therefore, patients should be allowed to choose whether they drink before discharge.
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Anesthesia and analgesia · Aug 1998
Randomized Controlled Trial Clinical TrialBetamethasone reduces postoperative pain and nausea after ambulatory surgery.
The aims of this study were to evaluate the effects of a single-dose glucocorticoid on the incidence and severity of pain and nausea and vomiting (PONV) after ambulatory surgery. Seventy-eight ASA physical status I-III patients scheduled for hemorrhoidectomy or hallux valgus correction were studied using a randomized, double-blind, placebo-controlled protocol. One group received 12 mg of betamethasone i.m. 30 min before the start of surgery (Group B), whereas the placebo group (Group P) received saline. General anesthesia was induced with propofol and fentanyl and maintained with isoflurane in both groups. Pain (measured using a visual analog scale, verbal score, and analgesic requirements), PONV, and other side effects were evaluated postoperatively. Patients in Group B experienced significantly less postoperative pain, less PONV, and better patient satisfaction during the first 24 h after surgery. In conclusion, a single dose of betamethasone (12 mg) seemed to produce analgesic and antiemetic effects after day-case surgery. ⋯ In a placebo-controlled study, the use of corticosteroid prophylaxis (betamethasone) produced a significant reduction in both postoperative pain and nausea in outpatients who received the corticosteroid injection before ambulatory foot or hemorrhoid operations.
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Anesthesia and analgesia · Aug 1998
Randomized Controlled Trial Clinical TrialIncidence and time course of cardiovascular side effects during spinal anesthesia after prophylactic administration of intravenous fluids or vasoconstrictors.
We studied the time course of arterial hypotension and/or bradycardia requiring treatment during spinal anesthesia and compared the efficacy of i.v. fluid or vasoconstrictor administration for the prevention of these side effects. Patients (n = 1066) were randomly allocated to either a volume group (lactated Ringer's solution 15 mL/kg within 15 min before spinal anesthesia), a dihydroergotamine group (10 microg/kg i.m. 15 min before anesthesia), or a placebo group. All patients breathed O2-enriched air during spinal anesthesia (4 mL of plain 0.5% bupivacaine). With the placebo, there were side effects (mean incidence 22.9%) for up to 45 min after the start of anesthesia. Dihydroergotamine reduced the incidence of side effects, preferentially the late ones, more (mean incidence 11.8%) than fluid administration (mean incidence 16.9%), which was effective only during the first 15 min of anesthesia. Both heart rate and arterial pressure decreased within 15 min before the manifestation of symptoms. In a subgroup of patients, the incidence of side effects (8%) was greatly reduced by the intraoperative application of both sedatives and opioids. We conclude that cardiovascular side effects may occur at any time during spinal anesthesia. Fluid administration reduced the incidence of early events, but dihydroergotamine the late events. ⋯ Cardiovascular side effects requiring treatment occurred at any time during spinal anesthesia in our placebo-controlled study, regardless of the prophylactic regimen (fluid infusions versus dihydroergotamine).
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Anesthesia and analgesia · Aug 1998
A molecular description of how noble gases and nitrogen bind to a model site of anesthetic action.
How some noble and diatomic gases produce anesthesia remains unknown. Although these gases have apparently minimal capacities to interact with a putative anesthetic site, xenon is a clinical anesthetic, and argon, krypton, and nitrogen produce anesthesia at hyperbaric pressures. In contrast, neon, helium, and hydrogen do not cause anesthesia at partial pressures up to their convulsant thresholds. We propose that anesthetic sites influenced by noble or diatomic gases produce binding energies composed of London dispersion and charge-induced dipole energies that are sufficient to overcome the concurrent unfavorable decrease in entropy that occurs when a gas molecule occupies the site. To test this hypothesis, we used the x-ray diffraction model of the binding site for Xe in metmyoglobin. This site offers a positively charged moiety of histidine 93 that is 3.8 A from Xe. We simulated placement of He, Ne, Ar, Kr, Xe, H2, and N2 sequentially at this binding site and calculated the binding energies, as well as the repulsive entropy contribution. We used free energies obtained from tonometry experiments to validate the calculated binding energies. We used partial pressures of gases that prevent response to a noxious stimulus (minimum alveolar anesthetic concentration [MAC]) as the anesthetic endpoint. The calculated binding energies correlated with binding energies derived from the in vivo (ln) data (RTln[MAC], where R is the gas constant and T is absolute temperature) with a slope near 1.0, indicating a parallel between the Xe binding site in metmyoglobin and the anesthetic site of action of noble and diatomic gases. Nonimmobilizing gases (Ne, He, and H2) could be distinguished by an unfavorable balance between binding energies and the repulsive entropy contribution. These gases also differed in their inability to displace water from the cavity. ⋯ The Xe binding site in metmyoglobin is a good model for the anesthetic sites of action of noble and diatomic gases. The additional binding energy provided by induction of a dipole in the gas by a charge at the binding site enhanced binding.
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Anesthesia and analgesia · Aug 1998
Minimum alveolar concentrations of noble gases, nitrogen, and sulfur hexafluoride in rats: helium and neon as nonimmobilizers (nonanesthetics)
We assessed the anesthetic properties of helium and neon at hyperbaric pressures by testing their capacity to decrease anesthetic requirement for desflurane using electrical stimulation of the tail as the anesthetic endpoint (i.e., the minimum alveolar anesthetic concentration [MAC]) in rats. Partial pressures of helium or neon near those predicted to produce anesthesia by the Meyer-Overton hypothesis (approximately 80-90 atm), tended to increase desflurane MAC, and these partial pressures of helium and neon produced convulsions when administered alone. In contrast, the noble gases argon, krypton, and xenon were anesthetic with mean MAC values of (+/- SD) of 27.0 +/- 2.6, 7.31 +/- 0.54, and 1.61 +/- 0.17 atm, respectively. Because the lethal partial pressures of nitrogen and sulfur hexafluoride overlapped their anesthetic partial pressures, MAC values were determined for these gases by additivity studies with desflurane. Nitrogen and sulfur hexafluoride MAC values were estimated to be 110 and 14.6 atm, respectively. Of the gases with anesthetic properties, nitrogen deviated the most from the Meyer-Overton hypothesis. ⋯ It has been thought that the high pressures of helium and neon that might be needed to produce anesthesia antagonize their anesthetic properties (pressure reversal of anesthesia). We propose an alternative explanation: like other compounds with a low affinity to water, helium and neon are intrinsically without anesthetic effect.