Anesthesia and analgesia
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Spinal neostigmine produces analgesia in chronically prepared rats, but not in sheep. However, since pain itself activates bulbospinal inhibitory pathways, neostigmine may be more effective in the postoperative period. We examined in sheep the antinociceptive effect of intrathecal neostigmine in the acute postoperative period and determined the muscarinic receptor subtype activated by neostigmine. ⋯ In contrast, intrathecal neostigmine caused no antinociception in another similar study performed at least 5 days after surgery. Pirenzepine, but not AFDX-116, abolished antinociception from neostigmine, suggesting an action on M1 subtype muscarinic receptors. Intrathecal neostigmine is antinociceptive in sheep during the acute postoperative period, and these data suggest that spinal cholinergic tone, and hence intrathecal neostigmine's analgesic effect, may be enhanced during the acute postoperative period.
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Anesthesia and analgesia · Jun 1995
Randomized Controlled Trial Comparative Study Clinical TrialNitrous oxide decreases the threshold for vasoconstriction less than sevoflurane or isoflurane.
The core temperature triggering thermoregulatory arteriovenous shunt constriction is designated the threshold for vasoconstriction. High thresholds are generally desirable because vasoconstriction helps prevent further core hypothermia by decreasing cutaneous heat loss and constraining metabolic heat to the core thermal compartment. Previous studies suggest that nitrous oxide (N2O) may inhibit thermoregulatory vasoconstriction less than comparable doses of volatile anesthetics. ⋯ The threshold for vasoconstriction was 35.8 +/- 0.3 degrees C in the patients given 50% N2O combined with 0.5 MAC sevoflurane, which was significantly greater than that in those given 1.0 MAC sevoflurane: 35.1 +/- 0.4 degrees C. Similarly, the threshold for vasoconstriction was 35.9 +/- 0.3 degrees C in the patients given 60% N2O combined with 0.5 MAC isoflurane, which was significantly greater than that in those given 1.0 MAC isoflurane: 35.0 +/- 0.5 degrees C. We thus conclude that N2O impairs thermoregulation less than sevoflurane or isoflurane.
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Anesthesia and analgesia · Jun 1995
Randomized Controlled Trial Comparative Study Clinical TrialComparative analgesic efficacy of patient-controlled analgesia with ketorolac versus morphine after elective intraabdominal operations.
We conducted a randomized, double-blind trial to compare analgesia and side effects produced by ketorolac and morphine during postoperative patient-controlled analgesia (PCA). Fifty-one patients (ASA classes I and II) undergoing elective intraabdominal procedures were assigned to one of two groups. When postoperative pain first increased to 4/10 (by visual analog scale [VAS]), patients were randomly assigned to one of two groups. ⋯ Mean pain scores were less in Group 1 than in Group 2 at each time, but only significantly so at 15 min (P < 0.0021), 30 min (P < 0.0336), and 24 h (P < 0.0358) after starting PCA. Time to acceptance of oral liquids was equivalent in Groups 1 and 2 (22 h and 21 h, respectively). IV ketorolac PCA, although well tolerated, has limited effectiveness as the sole postoperative analgesic after intraabdominal operations.
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Anesthesia and analgesia · Jun 1995
Carbon monoxide production from degradation of desflurane, enflurane, isoflurane, halothane, and sevoflurane by soda lime and Baralyme.
Anecdotal reports suggest that soda lime and Baralyme brand absorbent can degrade inhaled anesthetics to carbon monoxide (CO). We examined the factors that govern CO production and found that these include: 1) The anesthetic used: for a given minimum alveolar anesthetic concentration (MAC)-multiple, the magnitude of CO production (greatest to least) is desflurane > or = enflurane > isoflurane > halothane = sevoflurane. 2) The absorbent dryness: completely dry soda lime produces much more CO than absorbent with just 1.4% water content, and soda lime containing 4.8% or more water (standard soda lime contains 15% water) generates no CO. ⋯ These results suggest that CO generation can be avoided for all anesthetics by using soda lime with 4.8% (or more) water or Baralyme with 9.7% (or more) water, and by using inflow rates of less than 2-3 L/min. Such inflow rates are low enough to ensure that the absorbent does not dry out.
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Anesthesia and analgesia · Jun 1995
Changes in plasma cholinesterase activity and mivacurium neuromuscular block in response to normothermic cardiopulmonary bypass.
The effect of reduced plasma cholinesterase (ChE) activity in response to normothermic cardiopulmonary bypass (CPB) on mivacurium neuromuscular block was studied in nine patients anesthetized with propofol/fentanyl. Mivacurium was injected intravenously as an initial bolus of 150 micrograms/kg; repeat doses of 75 micrograms/kg were given when the evoked twitch tension attained 75% of control. ⋯ Their DUR25% (time from end of injection to recovery of neuromuscular transmission to 25% of control) were 13 +/- 3 min (means +/- SD) before, 14 +/- 4 min during, and 16 +/- 4 min (P < 0.05) after CPB. It is concluded, that, although markedly reducing the patient's previously normal ChE activity, normothermic CPB had little effect on the time characteristics of mivacurium neuromuscular block.