Anesthesia and analgesia
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Anesthesia and analgesia · Aug 2001
Randomized Controlled Trial Clinical TrialMore epidural than intravenous sufentanil is required to provide comparable postoperative pain relief.
The extent to which epidurally administered sufentanil acts directly on spinal opioid receptors remains controversial. We tested the hypothesis that small-dose boluses of sufentanil, given epidurally or IV, provide comparable analgesia at similar plasma sufentanil concentrations. The lipophilicity of sufentanil makes it likely to be absorbed into fat surrounding the epidural space. We therefore also tested the hypothesis that more epidural than IV sufentanil is required to produce comparable analgesia. Analgesia and plasma sufentanil concentrations were evaluated in 20 postoperative patients randomly assigned to patient-controlled epidural or IV sufentanil. Pain was evaluated with visual analog scales by blinded observers. Sufentanil doses and plasma concentrations were measured. Analgesia was similar with epidural and IV sufentanil administration. Plasma sufentanil concentrations were virtually identical in the two groups. However, significantly larger sufentanil doses were required with epidural administration: 238 +/- 50 microg vs 160 +/- 32 microg (P < 0.01). The primary mechanism by which small-dose boluses of epidurally-administered sufentanil produce analgesia seems to be systemic absorption of the drug with subsequent recirculation to the supraspinal opioid receptors. This study demonstrates that the cumulative dose of sufentanil, when administered as a small epidural bolus, is approximately 50% more than that administered IV to provide comparable analgesia. This indicates that the bioavailability of epidurally-administered sufentanil is reduced and suggests that a large proportion of the drug may be absorbed into the epidural fat. ⋯ More epidural than IV sufentanil was required to provide comparable postoperative pain relief and similar plasma sufentanil concentrations. These data suggest that when sufentanil is administered in small-dose boluses, much of the drug is absorbed into the epidural fat and that the primary mechanism by which epidurally administered sufentanil produces analgesia is via systemic absorption.
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Anesthesia and analgesia · Aug 2001
Randomized Controlled Trial Multicenter Study Comparative Study Clinical TrialA multicenter evaluation of the time-course of action of two doses of rapacuronium after early and late reversal with neostigmine.
Early reversal of rapacuronium may accelerate return of neuromuscular function. This study was designed to compare early (2 min after rapacuronium) or late (at 25% recovery of the first twitch [T1] of train-of-four) reversal of rapacuronium with neostigmine. We studied 119 subjects between the ages of 18 and 75 yr. Anesthesia was induced with fentanyl and thiopental and maintained with nitrous oxide, propofol, and fentanyl. Mechanomyographic neuromuscular monitoring was performed by using train-of-four stimulation of the ulnar nerve. Two groups received 1.5 mg/kg rapacuronium followed by neostigmine (50 microg/kg) and glycopyrrolate (10 microg/kg) either at 2 min after rapacuronium bolus or at 25% T1 recovery. The other two groups received 2.0 mg/kg rapacuronium, after which neostigmine was similarly given. For each rapacuronium dose, the time from the administration of rapacuronium to the start of T1 recovery or 25% T1 recovery was significantly shorter in subjects who received the reversal 2 min after rapacuronium. However, late recovery, defined by times from administration of rapacuronium to 70%, or 80% T4/T1 recovery, was not influenced by early reversal administration. We conclude that initial recovery is accelerated by early administration of neostigmine. Time to full recovery after rapacuronium administration is, however, dose-dependent and not significantly altered by early administration of neostigmine. ⋯ "Rescue reversal," which includes the administration of neostigmine shortly after the administration of rapacuronium, may accelerate the return of spontaneous breathing (early recovery), but does not shorten the time to complete recovery of upper airway function.
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Anesthesia and analgesia · Aug 2001
Randomized Controlled Trial Clinical TrialThe use of remifentanil to facilitate the insertion of the laryngeal mask airway.
Propofol is often used as an IV induction drug for anesthesia and the insertion of a laryngeal mask airway (LMA). As a sole anesthetic, it may be associated with undesirable airway responses such as coughing and gagging. We conducted a randomized, double-blinded study to compare the conditions during insertion of the LMA in 120 patients who received normal saline (Group P), remifentanil 0.25 microg/kg (Group R1), or remifentanil 0.5 microg/kg (Group R2) before the induction of anesthesia with IV propofol. The addition of remifentanil significantly improved the conditions of insertion; in Group R1, 82.5% (33 of 40 patients), and in Group R2, 85.0% (34 of 40 patients) had excellent insertion conditions as compared with the Control group P, 32.5% (13 of 40 patients). Patients in Group P were apneic for a mean (SD) time of 85 (38) s, 186 (75) s in group R1, and 284 (130) s in group R2. There was a lesser decrease in mean arterial blood pressure in group R1. We conclude that remifentanil 0.25 microg/kg, when administered after IV propofol 2.5 mg/kg, provides excellent conditions for insertion of the LMA with minimal hemodynamic disturbances. ⋯ Small-dose remifentanil can provide excellent conditions for laryngeal mask airway insertion with minimal hemodynamic disturbances.