Nitrous Oxide-narcotic Anesthesia Research Articles

Patient State Index

The Patient State Index (PSI) uses derived quantitative electroencephalogram features in a multivariate algorithm that varies as a function of hypnotic state. Data are recorded from two anterior, one midline central, and one midline posterior scalp locations. PSI has been demonstrated to have a significant relation to level of hypnosis during intravenous propofol, inhalation, and nitrous oxide-narcotic anesthesia. This multisite study evaluated the utility of PSI monitoring as an adjunct to standard anesthetic practice for guiding the delivery of propofol and alfentanil to accelerate emergence from anesthesia. Three hundred six patients were enrolled in this multicenter prospective randomized clinical study. Using continuous monitoring throughout the period of propofol-alfentanil-nitrous oxide anesthesia delivery, PSI guidance was compared with use of standard practice guidelines (both before [historic controls] and after exposure to the PSA 4000 monitor [Physiometrix, Inc., N. Billerica, MA; standard practice controls]). Anesthesia was always administered with the aim of providing hemodynamic stability, with rapid recovery. No significant differences were found for demographic variables or for site. The PSI group received significantly less propofol than the standard practice control group (11.9 microg x kg(-1) x min(-1); P < 0.01) and historic control group (18.2 microg x kg(-1) x min(-1); P < 0.001). Verbal response time, emergence time, extubation time, and eligibility for operating room discharge time were all significantly shorter for the PSI group compared with the historic control (3.3-3.8 min; P < 0.001) and standard practice control (1.4-1.5 min; P < 0.05 or P < 0.01) groups. No significant differences in the number of unwanted somatic events or hemodynamic instability and no incidences of reported awareness were found. Patient State Index-directed titration of propofol delivery resulted in faster emergence and recovery from propofol-alfentanil-nitrous oxide anesthesia, with modest decrease in the amount of propofol delivered, without increasing the number of unwanted events.

Dose-Response Relationship and Infusion Requirement of Cisatracurium Besylate in Infants and Children During Nitrous Oxide-Narcotic Anesthesia

Dose-Response Relationship and Infusion Requirement of Cisatracurium Besylate in Infants and Children During Nitrous Oxide-Narcotic Anesthesia

Dose-response relationship and infusion requirement of cisatracurium besylate in infants and children during nitrous oxide-narcotic anesthesia.

To determine the effect of age on the dose-response relation and infusion requirement of cisatracurium besylate in pediatric patients, 32 infants (mean age, 0.7 yr; range, 0.3-1.0 yr) and 32 children (mean age, 4.9 yr; range, 3.1-9.6 yr) were studied during thiopentone-nitrous oxideoxygen-narcotic anesthesia. Potency was determined using a single-dose (20, 26, 33, or 40 microg/kg) technique. Neuromuscular block was assessed by monitoring the electromyographic response of the adductor pollicis to supramaximal train-of-four stimulation of the ulnar nerve at 2 Hz. Least-squares linear regression analysis of the log-probit transformation of dose and maximal response yielded median effective dose (ED50) and 95% effective dose (ED95) values for infants (29+/-3 microg/kg and 43+/-9 microg/kg, respectively) that were similar to those for children (29+/-2 microg/kg and 47+/-7 microg/kg, respectively). The mean infusion rate necessary to maintain 90-99% neuromuscular block during the first hour in infants (1.9+/-0.4 microg x kg(-1) x min(-1); range: 1.3-2.5 microg x kg(-1) x min(-1)) was similar to that in children (2.0+/-0.5 microg x kg(-1) x min(-1); range: 1.3-2.9 microg x kg(-1) x min(-1)). The authors conclude that cisatracurium is equipotent in infants and children when dose is referenced to body weight during balanced anesthesia.

Mivacurium Infusion Requirements in Pediatric Surgical Patients During Nitrous Oxide-Halothane and During Nitrous Oxide-Narcotic Anesthesia

We were interested in determining the infusion rate of mivacurium required to maintain approximately 95% neuromuscular blockade during nitrous oxide-halothane (0.8% end-tidal) or nitrous oxide-narcotic anesthesia. Neuromuscular blockade was monitored by recording the electromyographic activity (Datex NMT) of the adductor pollicis muscle resulting from supramaximal stimulation of the ulnar nerve at 2 Hz for 2 s at 10-s intervals. Mivacurium steady-state infusion requirements averaged 315 +/- 26 micrograms.m-2.min-1 during nitrous oxide-halothane anesthesia and 375 +/- 19 micrograms.m-2.min-1 (mean +/- SEM) during nitrous oxide-narcotic anesthesia. Higher levels of pseudocholinesterase activity were generally associated with a higher mivacurium infusion requirement. During both anesthetics, younger age was associated with a higher infusion requirement when the infusion requirement was calculated in terms of micrograms.kg-1.min-1. This difference was not present when the infusion rate was calculated in terms of micrograms.m-2.m-1. There was no evidence of cumulation during prolonged mivacurium infusion. There was no difference in the rates of spontaneous or reversal-mediated recovery between anesthetic groups. After the termination of the infusion, spontaneous recovery to T4/T1 greater than or equal to 0.75 occurred in 9.8 +/- 0.4 min, with a recovery index, T25-75, of 4.0 +/- 0.2 min (mean +/- SEM). In summary, pseudocholinesterase activity is the major factor influencing mivacurium infusion rate in children during nitrous oxide-narcotic or nitrous oxide-halothane (0.8% end-tidal) anesthesia.

Transcranial magnetic motor evoked potentials (tcMMEP) for functional monitoring of motor pathways during scoliosis surgery.

Transcranial magnetic motor evoked potentials (tcMMEP) were used to assess the functional integrity of the descending motor pathways. The tcMMEP, recorded bilaterally from anterior tibialis muscles, were evoked by an electric current induced in the motor cortex by a high-intensity transient magnetic field applied to the scalp surface. Potentials were recorded from ten of 12 volunteer subjects and preoperatively in 11 of 11 scoliotic patients. Group mean latency in the volunteers (32.0 +/- 2.1 msec) did not differ from that of the scoliotics (28.6 +/- 5.0 msec), but values in the latter group were more variable. During nitrous oxide-narcotic anesthesia, tcMMEP with reproducible latencies were obtained in 9 of 11 (82%) cases. A small, but statistically significant, increase in latency occurred during anesthesia. Compared with preoperative values (523 +/- 490 microV), individual tcMMEP amplitudes were significantly decreased intraoperatively (163 +/- 153 microV). Although the absolute amplitudes varied widely, the minimum recorded value was over 20 microV. Thus, intraoperative tcMMEP waveforms were readily discriminable from background electrical noise. These results demonstrate the technical feasibility of intraoperative tcMMEP monitoring. Combined somatosensory evoked potential and tcMMEP monitoring may provide a more complete picture of spinal cord function, intraoperatively.

Clinical Pharmacology of Mivacurium Chloride (BW B1090U) in Children During Nitrous Oxide-Halothane and Nitrous Oxide-Narcotic Anesthesia

We determined the dose-response relationships of mivacurium (BW B1090U) in children (2-10 years) during nitrous oxide-halothane anesthesia (0.8% end-tidal) and during nitrous oxide-narcotic anesthesia. Neuromuscular blockade was monitored by recording the electromyographic activity of the adductor pollicis muscle resulting from supramaximal stimulation at the ulnar nerve at 2 Hz for 2 seconds at 10-second intervals. To estimate dose-response relationships, for each anesthetic background four subgroups of nine patients received single bolus doses of 20-120 micrograms/kg mivacurium. The ED50 and ED95 (estimated from linear regression plots of log-dose vs. probit of effect) were 52 micrograms/kg and 89 micrograms/kg during halothane anesthesia and 62 micrograms/kg and 103 micrograms/kg during narcotic anesthesia. Nine additional patients in each anesthetic group received 250 micrograms/kg mivacurium. Three of the 18 patients given 250 micrograms/kg mivacurium developed cutaneous flushing; in one of these mean arterial pressure decreased 32% for less than 1 minute; no significant changes in heart rate occurred. With the increase in mivacurium dose from 120 micrograms/kg to 250 micrograms/kg the times to onset of 90% and maximum neuromuscular block decreased by 0.5 to 1 minute, and the times to recovery of neuromuscular transmission to 5% (T5) or 25% (T25) increased by 2-4 minutes. The recovery index (T25-75) in patients anesthetized with halothane was 4.3 +/- 1.5 minute (mean +/- SD); the time to complete recovery (T4:1 greater than or equal to 0.75) was 19.8 +/- 7.4 minutes.

Mivacurium Chloride (BW B1090U)-Induced Neuromuscular Blockade During Nitrous Oxide???Isoflurane and Nitrous Oxide???Narcotic Anesthesia in Adult Surgical Patients

The neuromuscular and cardiovascular effects of mivacurium were studied in 90 adult patients during nitrous oxide-oxygen-isoflurane (n = 45, ISO group) and nitrous oxide-oxygen-narcotic (n = 45, BAL group) anesthesia. Neuromuscular blockade was measured using electromyographic activity of the adductor pollicis muscle after supramaximal stimulation of the ulnar nerve at 2 Hz for 2 seconds at 10-second intervals. To estimate dose-response relations, three subgroups of nine patients in the ISO group received mivacurium doses of 0.025, 0.03, and 0.04 mg/kg, respectively. Similarly, three subgroups of nine patients in the BAL group received mivacurium doses of 0.03, 0.04, and 0.05 mg/kg, respectively. The ED50 and ED95 of mivacurium in each group were estimated from linear regression plots of log dose vs probit of maximum percentage depression of neuromuscular function. The estimated ED50 values for the ISO and BAL groups were 0.029 and 0.041 mg/kg, respectively. The estimated ED95 values for the ISO and BAL groups were 0.045 and 0.058 mg/kg, respectively. Recovery indexes were measured in 26 patients who received ED95 or greater doses of mivacurium in either the ISO or BAL groups. The recovery index was shorter in the BAL group (5.5 +/- 1.6 minutes [n = 10]), than in the ISO group (7.4 +/- 3.0 minutes [n = 16]). The addition of isoflurane (0.5-0.75% end-tidal concentration) to nitrous oxide-narcotic anesthesia augments the degree of neuromuscular blockade from a given dose of mivacurium and also prolongs the recovery index.

General Anesthesia for Outpatient Laparoscopy With an Objective Measure of Recovery

Laparoscopic procedures on an outpatient basis, using nitrous oxide-narcotic anesthesia combined with the use of a muscle relaxant, were performed on 153 patients. Mild hyperventilation was employed to increase carbon dioxide elimination, blood gases being monitored in 38 patients to document this effect. Recovery in 42 patients was assessed by means of the Trieger Dot Test, with testing being carried out preanesthesia, immediately postanesthesia, and at the time of discharge from the recovery room. These data suggest that early discharge is possible, the average recovery time being 81 minutes. A questionnaire returned by 144 patients cited sore throat, hoarseness, nausea, and a sensation of having been “drugged” as the predominant postoperative complaints.