Anesthesia and analgesia
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Anesthesia and analgesia · Jul 1998
Randomized Controlled Trial Clinical TrialPreoperative epidural ketamine does not have a postoperative opioid sparing effect.
Ketamine reduces nociception by binding noncompetitively to the N-methyl-D-aspartate receptor, the activation of which provokes hypersensitivity within the central nervous system. We studied the analgesic effect of extradural ketamine given before or after upper abdominal surgery. We sought to assess the effect of ketamine on preemptive analgesia. Ketamine 60 mg was injected epidurally through an indwelling catheter that was inserted at the T7-8 or T8-9 interspace in 98 patients. Patients were randomly allocated into one of the two groups, each consisting of 49 patients: ketamine was given before the induction of anesthesia (Group 1) and after the parietal peritoneum was closed (Group 2). Sample size was calculated using a two-tailed alpha = 0.05 and power of 95%. For postoperative analgesia, meperidine 25 mg was given epidurally whenever a patient complained of pain or the visual analog scale score was greater than 4. The first and the second day cumulative meperidine consumption was not different between the two groups. We conclude that preoperative epidural ketamine 60 mg does not have a preemptive analgesic effect. ⋯ In patients undergoing upper abdominal surgery, a single epidural injection of 60 mg of ketamine administered preoperatively was not associated with decreased postoperative analgesic demands. This findings does not contribute to one of the fundamental scientific objectives of preemptive analgesia that postoperative analgesia well beyond the duration of any single drug effect could be produced.
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Anesthesia and analgesia · Jul 1998
Randomized Controlled Trial Clinical TrialVisual evaluation of residual curarization in anesthetized patients using one hundred-hertz, five-second tetanic stimulation at the adductor pollicis muscle.
We were looking for a clinical test to indicate a train-of-four (TOF) ratio of approximately 0.9. We compared the adductor pollicis muscle (AP) visually evaluated response to ulnar nerve 100-Hz, 5-s tetanus (RF100 Hz) with the measured AP TOF ratio in 30 ASA physical status I or II adult anesthetized (propofol, sufentanil, N2O/O2) patients. After the induction of anesthesia, the left ulnar nerve was stimulated at the wrist (single twitch and TOF) and the resultant isometric force was measured. When TOF was assessed, the independent investigators, unaware of the left AP-measured TOF ratios, visually evaluated the presence or absence of AP fading elicited by right ulnar nerve 100-Hz, 5-s tetanus. The 30 patients were randomly allocated to receive either 0.5 mg/kg atracurium (n = 15) or 0.1 mg/kg vecuronium (n = 15). The neuromuscular blockade was allowed to resolve spontaneously. A multiple logistic regression analysis was performed by computing the 771 visual observations. The probabilities of success of 100-Hz, 5-s tetanus to detect TOF ratios of 0.8, 0.85, and 0.9 were 99%, 96%, and 67%, respectively. The sensitivity and specificity of 100-Hz, 5-s tetanus as an indicator of TOF ratios of 0.85 and 0.9 are 100% and 75%, 54% and 67%, respectively. We conclude that RF100 Hz visual assessment seems to be highly sensitive in evaluating residual paralysis, as the absence of RF100 Hz visual fading at the AP is compatible with a TOF ratio > 0.85. ⋯ After the administration of muscle relaxants, the absence of visual fading at the adductor pollicis, elicited in anesthetized patients by 100-Hz, 5-s tetanus, is compatible with a train-of four ratio > 0.85. Therefore, clinical observation of fading after 100-Hz, 5-s tetanus seems to be a highly sensitive test in evaluating residual paralysis.
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Anesthesia and analgesia · Jul 1998
Clinical TrialEpidural labor analgesia and the incidence of cesarean delivery for dystocia.
We performed this retrospective study to examine the changes in cesarean delivery rates associated with the establishment of a labor epidural service. In April 1993, St. Louis Regional Medical Center established an on-demand labor epidural service. We obtained demographic data for all patients and reviewed the operative records of all patients undergoing cesarean section who delivered 12 mo before and 16 mo after the start of the labor epidural service. We compared labor epidural rates and total and nulliparous dystocia cesarean delivery rates before and after the epidural service started and among patients who did and did not receive labor epidural analgesia when it was available. Included were 3195 patients who delivered before and 3733 patients who delivered after epidural analgesia became available. Labor epidural rates were 1.2% vs 29.4% for the Before group versus the After group (P < 0.001). Total (9.1% vs 9.7%) and nulliparous dystocia (5.7% vs 6.4%) cesarean delivery rates did not significantly change with the availability of epidural analgesia. However, the total (11.6% vs 8.8%; P = 0.009) and dystocia (8.0% vs 1.0%; P = 0.001) cesarean delivery rates were higher among patients who received epidural analgesia when it was available. We conclude that epidural labor analgesia is associated with, but does not cause, cesarean delivery for dystocia. ⋯ Increased epidural analgesia use did not change the overall dystocia cesarean delivery rate, although dystocia was more common among women who chose an epidural analgesia. Consequently, limiting epidural availability will not affect cesarean delivery rates. The evidence does not support advising patients that epidural labor analgesia increases the risk of cesarean delivery.
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Anesthesia and analgesia · Jul 1998
Comparative Study Clinical TrialComparison of plasma lidocaine concentrations after injection of a fixed small volume in the stellate ganglion, the lumbar epidural space, or a single intercostal nerve.
We measured the plasma lidocaine concentrations after stellate ganglion block (SGB) and compared them with those after intercostal nerve block (ICNB) and epidural block (EB) using identical doses of lidocaine. Thirty patients undergoing SGB (n = 10), ICNB (n = 10), or EB (n = 10) in our pain clinic participated in this study. Six milliliters of 1% lidocaine was used for all nerve blocks. SGB was performed at the C6 transverse process, ICNB was performed on a single intercostal nerve, and epidural lidocaine was injected through the lumbar epidural catheter. After drug administration, venous blood samples were taken from an indwelling catheter in the arm every minute for the first 10 min and 15, 20, 30, 45, and 60 min thereafter. Plasma lidocaine concentrations were measured by using an enzyme immunoassay method. The SGB group showed significantly higher peak plasma lidocaine concentrations than other groups (SGB 1.65 +/- 0.21 microgram/mL, ICNB 0.89 +/- 0.12 microgram/mL, EB 0.91 +/- 0.19 microgram/mL; P < 0.01). The SGB group reached peak levels significantly faster than the other groups (SGB 3.4 +/- 1.0 min, ICNB 7.9 +/- 1.5 min, EB 6.9 +/- 0.7 min; P < 0.01). We conclude that the plasma lidocaine concentrations after SGB were higher than those after ICNB and EB when using small, equal doses of lidocaine. The high and rapid peak plasma lidocaine concentrations after SGB are probably related to the high vascularity of the injection site. ⋯ Higher plasma concentrations of local anesthetics are reportedly obtained after multiple intercostal nerves blocks compared with those after other types of nerve blocks. Our results, however, showed that the peak plasma concentrations after stellate ganglion block were higher and faster than those after a single intercostal nerve block.
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Anesthesia and analgesia · Jul 1998
Practice patterns in managing the difficult airway by anesthesiologists in the United States.
Despite the availability of several techniques and devices for the management of the difficult airway, little information has been published regarding the prevalence of their use by anesthesiologists in the United States. To determine current practice patterns, we surveyed clinicians using a questionnaire consisting of 14 difficult airway scenarios. Anesthesiologists were requested to indicate their likely approach to anesthetic induction (e.g., awake but sedated, general anesthesia with spontaneous ventilation, general anesthesia with apnea after assuring a patent airway, or general anesthesia with apnea) and the primary device they would use to intubate (e.g., direct laryngoscopy [DL], flexible fiberoptic bronchoscope [FOB], rigid fiberoptic device, surgical airway, retrograde intubation kit, laryngeal mask airway, gum elastic bougie, or Combitube). The availability of these devices was also determined (in room at all times, available "stat," available if arranged preoperatively, or not available). The survey was mailed to 1000 randomly chosen active members of the American Society of Anesthesiologists. Second and third surveys were mailed to non responders. Four hundred seventy-two completed surveys were returned. Responses by demographic groups were compared by using chi 2 analysis. DL and FOB-aided tracheal intubation techniques were chosen for most cases by most anesthesiologists (P < 0.05). Anesthesiologists with > 10 yr of clinical experience and those older than 55 yr of age preferred DL with apneic conditions (P < 0.05). Anesthesiologists who had attended workshops within the last 5 yr had greater availability of retrograde guidewire equipment and FOBs (P < 0.05). There was little use of newer alternative airway devices. ⋯ Although the teaching of alternative methods of securing a difficult airway has become ubiquitous, most anesthesiologists rely on direct laryngoscopy and fiberoptic-aided intubation in most clinical circumstances. Although workshops in the management of the difficult airway may have resulted in increased use of the fiberoptic bronchoscope and the availability of retrograde guidewire intubation equipment, other devices have not enjoyed such an increase.