Anesthesia and analgesia
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Anesthesia and analgesia · Nov 2001
Clinical TrialT-wave amplitude as an indicator for detecting intravascular injection of epinephrine test dose in awake and anesthetized elderly patients.
Aging is associated with reduced heart rate (HR) responsiveness to a simulated IV test dose containing epinephrine. We tested the hypothesis that a more contemporary T-wave criterion (positive if there was a > or = 25% decrease in T-wave amplitude) was applicable in both awake and anesthetized older patients. Sixteen healthy patients > or = 65 yr old first received 3 mL of normal saline IV, followed 4 min later by 1.5% lidocaine 3 mL containing 15 microg epinephrine (1:200,000) IV in the supine position when awake, and they were anesthetized with stable 2% end-tidal sevoflurane and 67% nitrous oxide. HR, systolic blood pressure (SBP) determined invasively, and lead II of the electrocardiogram were continuously recorded for 4 min after the IV injections of saline and the test dose. A sensitivity of 88% and a negative predictive value of 89% were obtained in awake patients on the basis of the conventional HR criterion (positive if there was a > or = 20 bpm increase), whereas a sensitivity of 81% and a negative predictive value of 84% were obtained during sevoflurane anesthesia on the basis of the modified HR criterion (positive if there was a > or = 10 bpm increase). However, sensitivities, specificities, and positive and negative predictive values were all 100% on the basis of the SBP (positive if a > or = 15 mm Hg increase was recorded with an arterial line) and the T-wave criteria for both awake and anesthetized conditions. These results suggest that the SBP and T-wave criteria should be applied in awake and anesthetized elderly patients for detecting accidental intravascular injection of the epinephrine-containing test dose. ⋯ To determine whether an epidural catheter is in a blood vessel, an epidural test dose containing 15 microg epinephrine is often used. We found that an increase in systolic blood pressure and a decrease in T-wave amplitude, but not an increase in heart rate, seem to be reliable indicators for detecting accidental intravascular injection in both awake and sevoflurane-anesthetized patients > or = 65 yr old.
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Anesthesia and analgesia · Nov 2001
Precurarization and priming: a theoretical analysis of safety and timing.
The priming principle suggests that the onset of neuromuscular block may be accelerated if an intubating dose is preceded by a priming dose administered a few minutes earlier. We thought it would be instructive to use a pharmacodynamic/pharmacokinetic model to estimate the risk associated with different priming doses and intervals. In any normal population, there is wide variability in the response to neuromuscular blocking drugs. For most relaxants, the coefficient of variation for the 50% effective dose (ED(50)) approximates 20%-25%. Thus, 1 patient in 50 (-2.05 SD) may have an ED(50) only half of the commonly cited value. By using published pharmacodynamic/pharmacokinetic data, we calculated the effect of administering 10%, 20%, or 30% of the ED(95) on the response of the adductor pollicis muscle in a population normally distributed with respect to drug sensitivity. A dose equivalent to 10% of the ED(95) will rarely produce a measurable neuromuscular effect. As this dose is increased, the potential for clinical weakness rapidly escalates. In 1 in 50 individuals, the usual recommendation of 10% of the intubation dose will produce measurable neuromuscular depression. For vecuronium, the optimal priming interval is 5 min. The safety and dependability of the priming principle is very much subject to the laws of probability. ⋯ When using the priming principle to accelerate the onset of neuromuscular block, the initial dose should not exceed 10% the drug's ED(95). For drugs other than rocuronium, the optimal priming interval is not <5 min.
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Anesthesia and analgesia · Nov 2001
Randomized Controlled Trial Comparative Study Clinical TrialUlnar nerve block induced by the new local anesthetic IQB-9302 in healthy volunteers: a comparison with bupivacaine.
We evaluated the duration of sensory anesthesia after blockade of the ulnar nerve of IQB-9302, a new local amide anesthetic, compared with bupivacaine. A double-blinded, randomized, cross-over study in 12 healthy volunteers aged 18 to 35 yr was performed. Three milliliters of 0.25% IQB-9302 was administered in one wrist and bupivacaine in the other. A week later, the blocks were repeated with a concentration of 0.5%. These concentrations were chosen because they seemed to be equipotent in previous studies. The duration of sensory anesthesia was the main variable measured; secondary outcomes were motor block, time to onset, and time to recovery from block. The duration of sensory block was similar for IQB-9302 and bupivacaine at a concentration of 0.25%; median and range: 409 min (0-800 min) for IQB-9302 and 258 min (0-665 min) for bupivacaine (95% confidence interval for the difference from -47 to 545, P = 0.82, Wilcoxon's test). The results with 0.5% were: 525 min (440-735 min) and 690 min (365-1098 min), respectively (P = 0.026). There were no significant differences in the other variables measured. No important adverse reactions were seen. We conclude that IQB-9302 is an effective new local anesthetic for blockade of ulnar nerve at the concentrations tested. ⋯ IQB-9302 is a new local anesthetic that has shown a long duration of action and low cardiovascular toxicity in preclinical studies. We report the results of a phase I clinical trial to compare this new drug with bupivacaine for ulnar nerve block.
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Anesthesia and analgesia · Nov 2001
Randomized Controlled Trial Comparative Study Clinical TrialA comparison of tramadol, amitriptyline, and meperidine for postepidural anesthetic shivering in parturients.
Tramadol is effective for treating shivering during epidural anesthesia in parturients. In addition to its low affinity to opioid receptors, tramadol exerts a modulatory effect on central monoaminergic pathways. In this respect, there are parallels between the mechanisms of the action of tramadol and antidepressants such as amitriptyline. Meperidine is often recommended for the treatment of postanesthetic shivering. This prospective, double-blinded, and randomized clinical study was performed to compare the antishivering effects and accompanying side effects among tramadol, meperidine, and amitriptyline for the treatment of postepidural anesthetic shivering. Forty-five parturients who shivered during cesarean delivery under epidural anesthesia and requested antishivering treatment were randomly allocated to one of three groups for IV treatment: Group T (n = 15) received tramadol 0.5 mg/kg, Group M (n = 15) received meperidine 0.5 mg/kg, and Group A (n = 15) received amitriptyline 15 or 20 mg. The response rate (shivering ceased after treatment in 15 min) was 87% and 93% for Groups T and M, respectively, compared with 13% in Group A (P < 0.01). The time that elapsed from treatment to the time shivering ceased was 5.1 +/- 3.6 min (mean +/- SD) for Group T and 4.2 +/- 2.3 min for Group M. There was a significantly more frequent incidence (33%) of somnolence in Group M when compared with Groups T (7%) and A (0%) (P < 0.01). However, no significant differences were shown for pruritus, nausea, vomiting, or Apgar scores of newborns. We concluded that both tramadol and meperidine show a significantly faster response rate in the treatment of postepidural anesthetic shivering when compared with amitriptyline in the dosage used; tramadol had a decreased incidence of somnolence when compared with meperidine. ⋯ This study was performed to compare the antishivering and side effects among tramadol, amitriptyline, and meperidine for the treatment of postepidural anesthetic shivering in parturients. Both tramadol and meperidine show a significantly faster response rate in the treatment of shivering when compared with amitriptyline. Tramadol had a less frequent incidence of somnolence than meperidine.
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Anesthesia and analgesia · Nov 2001
Randomized Controlled Trial Clinical TrialBuspirone and meperidine synergistically reduce the shivering threshold.
Mild hypothermia (i.e., 34 degrees C) may prove therapeutic for patients with stroke, but it usually provokes shivering. We tested the hypothesis that the combination of buspirone (a serotonin 1A partial agonist) and meperidine synergistically reduces the shivering threshold (triggering tympanic membrane temperature) to at least 34 degrees C while producing little sedation or respiratory depression. Eight volunteers each participated on four randomly-assigned days: 1) large-dose oral buspirone (60 mg); 2) large-dose IV meperidine (target plasma concentration of 0.8 microg/mL); 3) the combination of buspirone (30 mg) and meperidine (0.4 microg/mL); and 4) a control day without drugs. Core hypothermia was induced by infusion of lactated Ringer's solution at 4 degrees C. The control shivering threshold was 35.7 degrees C +/- 0.2 degrees C. The threshold was 35.0 degrees C +/- 0.8 degrees C during large-dose buspirone and 33.4 degrees C +/- 0.3 degrees C during large-dose meperidine. The threshold during the combination of the two drugs was 33.4 degrees C +/- 0.7 degrees C. There was minimal sedation on the buspirone and combination days and mild sedation on the large-dose meperidine day. End-tidal PCO2 increased approximately 10 mm Hg with meperidine alone. Buspirone alone slightly reduced the shivering threshold. The combination of small-dose buspirone and small-dose meperidine acted synergistically to reduce the shivering threshold while causing little sedation or respiratory toxicity. ⋯ Mild hypothermia may be an effective treatment for acute stroke, but it usually triggers shivering, which could be harmful. Our results indicate that the combination of small-dose buspirone and small-dose meperidine acts synergistically to reduce the shivering threshold while causing little sedation or respiratory toxicity. This combination may facilitate the induction of therapeutic hypothermia in stroke victims.