Shigeho Morita

Emergence agitation after sevoflurane versus propofol in pediatric patients

UNLABELLED Sevoflurane may be associated with a high incidence of emergence agitation in preschool children. We tested the hypothesis that maintenance of anesthesia with propofol after sevoflurane induction would reduce the incidence of this excitatory behavior compared with continuing sevoflurane for maintenance. We conducted a randomized, single-blinded, two-period, cross-over study in 16 preschool age children undergoing repeated brief general anesthetics for eye examination. After sevoflurane induction, patients were randomly assigned to receive either sevoflurane or propofol anesthesia for maintenance. The alternative anesthetic was used for the maintenance of anesthesia on the second occasion. We compared the speed and quality of recovery characteristics of these anesthetics, as well as, overall parent satisfaction with anesthesia. Eight patients first received sevoflurane and the remaining eight patients first received propofol. Of the patients who received sevoflurane for the maintenance of anesthesia, 38% developed emergence agitation. In contrast, none developed emergence agitation when propofol was administered for maintenance of anesthesia. Despite emergence agitation, sevoflurane provided a shorter postanesthesia care unit stay than propofol. Parent satisfaction with anesthesia was greater with propofol than with sevoflurane. IMPLICATIONS In this cross-over study, we observed the incidence of emergence agitation with sevoflurane (38%) was significantly greater than with propofol (0%) in premedicated, preschool-aged children undergoing minor noninvasive surgery.

Xenon Provides Faster Emergence from Anesthesia than Does Nitrous Oxide-sevoflurane or Nitrous Oxide-isoflurane

Background: Xenon, an inert gas with anesthetic properties (minimum alveolar concentration [MAC] = 71%), has an extremely low blood:gas partition coefficient (0.14). Therefore, we predicted that xenon would provide more rapid emergence from anesthesia than does N2 O + isoflurane or N2 O + sevoflurane of equivalent MAC. Methods: Thirty American Society of Anesthsiologists class I or II patients undergoing total abdominal hysterectomy were randomly assigned to receive 60% xenon, 60% N2 O + 0.5% isoflurane, or 60% N2 O + 0.7% sevoflurane (all concentrations are end‐tidal: n = 10 per group). After placement of an epidural catheter, anesthesia was induced with standardized doses of midazolam, thiopental, and fentanyl. Thirty minutes later, xenon, N2 O + isoflurane, or N2 O + sevoflurane was started as previously assigned. These regimens were supplemented with epidural anesthesia with mepivacaine so that the mean arterial pressure and heart rate were controlled within 20% of the preoperative values. At the end of operation lasting approximately 2 h, all inhalational anesthetics were discontinued, and the patients were allowed to awaken while breathing spontaneously on an 8 l/min inflow of oxygen. A blinded investigator recorded the time until the patient opened her eyes on command (T1), was judged ready for extubation (T2), could correctly state her name, her date of birth, and the name of the hospital (T3), and could count backward from 10 to 1 in less than 15 s (T4). Results: Emergence times from xenon anesthesia were: T1, 3.4 +/‐ 0.9 min; T2, 3.6 +/‐ 1 min; T3, 5.2 +/‐ 1.4 min; and T4, 6.0 +/‐ 1.6 min (mean +/‐ SD). These were one half to one third of those from N2 O + sevoflurane (T1, 6.0 +/‐ 1.7 min; T4, 10.5 +/‐ 2.5 min) or N2 O + isoflurane (T1, 7.0 +/‐ 1.9 min; T4, 14.3 +/‐ 2.8 min) anesthesia. The three groups did not differ in terms of patient demographics, the duration of anesthesia, the amount of epidural mepivacaine administered, or the postoperative pain rating. No patient could recalls intraoperative events. Conclusions: Emergence from xenon anesthesia is two or three times faster than that from equal‐MAC N2 O + isoflurane or N2 O + sevoflurane anesthesia.

Minimum alveolar concentration-awake of Xenon alone and in combination with isoflurane or sevoflurane.

BackgroundThe minimum alveolar concentration (MAC)-awake is a traditional index of hypnotic potency of an inhalational anesthetic. The MAC-awake of xenon, an inert gas with anesthetic properties (MAC = 71%), has not been determined. It is also unknown how xenon interacts with isoflurane or sevoflurane on the MAC-awake. MethodsIn the first part of the study, 90 female patients received xenon, nitrous oxide (N2O), isoflurane, or sevoflurane supplemented with epidural anesthesia (n = 36 for xenon and n = 18 per group for other anesthetics). In the second part, 72 additional patients received either xenon or N2O combined with the 0.5 times MAC-awake concentration of isoflurane or sevoflurane (0.2% and 0.3%, respectively, based on the results of the first part; n = 18 per group). During emergence, the concentration of an assigned anesthetic (xenon or N2O only in the second part) was decreased in 0.1 MAC decrements every 15 min from 0.8 MAC or from 70% in the case of N2O until the patient followed the command to either open her eyes or to squeeze and release the investigator’s hand. The concentration midway between the value permitting the first response to command and that just preventing it was defined as the MAC-awake. ResultsThe MAC-awake were as follows: xenon, 32.6 ± 6.1% (mean ± SD) or 0.46 ± 0.09 MAC; N2O, 63.3 ± 7.1% (0.61 ± 0.07 MAC); isoflurane, 0.40 ± 0.07% (0.35 ± 0.06 MAC); and sevoflurane, 0.59 ± 0.10% (0.35 ± 0.06 MAC). Addition of the 0.5 MAC-awake concentrations of isoflurane and sevoflurane reduced the MAC-awake of xenon to 0.50 ± 0.15 and 0.51 ± 0.16 times its MAC-awake as a sole agent, but that of N2O to the values significantly greater than 0.5 times its MAC-awake as a sole agent (0.68 ± 0.12 and 0.66 ± 0.14 times MAC-awake;P < 0.01, analysis of variance and Dunnett’s test). ConclusionsThe MAC-awake of xenon is 33% or 0.46 times its MAC. In terms of the MAC-fraction, this is smaller than that for N2O but greater than those for isoflurane and sevoflurane. Unlike N2O, xenon interacts additively with isoflurane and sevoflurane on MAC-awake.

Minimum alveolar concentration (MAC) of xenon with sevoflurane in humans

BackgroundAlthough more than 30 yr ago the minimum alveolar concentration (MAC) of xenon was determined to be 71%, that previous study had technological limitations, and no other studies have confirmed the MAC value of xenon since. The current study was designed to confirm the MAC value of xenon in adult surgical patients using more modern techniques. MethodsSixty patients were anesthetized with sevoflurane with or without xenon. They were randomly allocated to one of four groups; patients in group 1 received no xenon, whereas those in groups 2, 3, and 4 received end-tidal concentrations of 20, 40, and 60%, respectively (n = 15 each group). Target end-tidal sevoflurane concentrations were chosen using the “up-and-down” method in each group. After steady state sevoflurane and xenon concentrations were maintained for at least 15 min, each patient was monitored for a somatic response at surgical incision. Somatic response was defined as any purposeful bodily movement. The MAC of sevoflurane and its reduction by xenon was evaluated using the multiple independent variable logistic regression model. ResultsThe interaction coefficient of the multiple variable logistic regression was not significantly different from zero (P = 0.143). The MAC of xenon calculated as xenon concentration that would reduce MAC of sevoflurane to 0% was 63.1%. ConclusionsThe authors could not determine whether interaction in blocking somatic responses in 50% of patients is additive. The MAC of xenon is in the range of the values that were predicted in a previous study.

Comparison of inhalation inductions with xenon and sevoflurane

Background: Xenon is an odorless gas with low blood‐gas solubility coefficient and without occupational and environmental hazards. This investigation was performed to evaluate the speed of induction, and respiratory and cardiovascular reactions to inhalation induction with xenon compared to an equianesthetic concentration of sevoflurane.

The NMDA-receptor antagonist ketamine abolishes neuropathic pain after epidural administration in a clinical case

A 14-year-old male patient developed severe right limb pain after traumatic sciatic nerve injury. His pain was diagnosed as neuropathic pain (complex regional pain syndrome, type II). He did not respond to any conventional therapy for limb pain including non-steroidal antiinflammatory drugs, antidepressants, anticonvulsants, continuous epidural administration of local anesthetics and psychotherapy. Following continuous epidural administration of a very low dose of ketamine, an N-methyl-D-aspartic acid (NMDA) receptor antagonist, 25 microg/kg per h for 10 days, complete pain relief was obtained without any side-effects. There has been no recurrence of pain for 8 months after discontinuation of epidural ketamine. The symptoms related to dysfunction of the sympathetic nervous system still remained after complete pain relief. We discuss pain mechanisms, pain relief and the use of ketamine in this case.

Effects of Xenon on Hemodynamic Responses to Skin Incision in Humans

BACKGROUND The authors evaluated the hemodynamic suppressive effects of xenon in combination with sevoflurane at skin incision in patients undergoing surgery. METHODS Forty patients were assigned randomly to receive one of the following four anesthetics: 1.3 minimum alveolar concentration (MAC) sevoflurane, 0.7 MAC xenon with 0.6 MAC sevoflurane, 1 MAC xenon with 0.3 MAC sevoflurane, or 0.7 MAC nitrous oxide with 0.6 MAC sevoflurane (n = 10 each group). Systolic blood pressure and heart rate were measured before anesthesia, before incision, and approximately 1 min after incision. RESULTS The changes in hemodynamic variables in response to incision were less with sevoflurane in combination with xenon and nitrous oxide than with sevoflurane alone. Changes in heart rate (in beats/min) were 19+/-11 (+/- SD) for sevoflurane alone, 11+/-6 for 0.7 MAC xenon-sevoflurane, 4+/-4 for 1 MAC xenon-sevoflurane, and 8+/-7 for nitrous oxide-sevoflurane. Changes in systolic blood pressure were 35+/-18 mmHg for sevoflurane alone, 18+/-8 mmHg for 0.7 MAC xenon-sevoflurane, 16+/-7 mmHg for 1 MAC xenon-sevoflurane, and 14+/-10 mmHg for nitrous oxide-sevoflurane. CONCLUSIONS Xenon and nitrous oxide in combination with sevoflurane can reduce hemodynamic responses to skin incision compared with sevoflurane alone. One probable explanation may be that xenon has analgesic properties similar to those of nitrous oxide, although the exact mechanism is yet to be determined.

Increased N-pentane Excretion in Humans: A Consequence of Pulmonary Oxygen Exposure

Lipid peroxidation by free radicals has been suggested as a mechanism of a lung injury caused by breathing higher than normal concentrations of oxygen. The appearance of hydrocarbons such as n-pentane in the expired gas of mammals has been proposed as in vivo evidence of lipid peroxidation. The excretion of n-pentane was studied in 15 healthy volunteers in whom excretion of exogenous n-pentane was determined over a 60- to 90-min period while breathing hydrocarbon-free gases. N-pentane elimination rates (mean ± SEM) in the expired gas at 0, 30, 60, 90, and 120 min were 10.2 ± 1.5, 1.6 ± 0.2, 1.2 ± 0.9, 1.3 ± 0.4, and 1.3 ± 0.3 (pmol · kg−1 · min−1), respectively. Using a specially assembled circuit, a 2-h oxygen exposure study was performed on six healthy volunteers, in whom basal n-pentane excretion varied ten-fold among individuals, from 0.25 to 2.25 pmol · kg−1 · min−1. After breathing 100% oxygen, npentane excretion was augmented 62–420% within 30 to 120 min. The authors conclude that lipid peroxidation may occur in humans within 30 min of breathing 100% oxygen.

Effect of xenon on autonomic cardiovascular control--comparison with isoflurane and nitrous oxide.

STUDY OBJECTIVES To clarify the effect of xenon on the autonomic nervous system by comparing similar effects of isoflurane and nitrous oxide. DESIGN Prospective, randomized study. SETTING Operating room at a university hospital. PATIENTS 39 ASA physical status I and II patients scheduled for general anesthesia. INTERVENTIONS Patients were randomly allocated into one of three groups and received one of the following inhalational anesthetics: 56% of xenon (Group X), 0.94% of isoflurane (Group I), or 70% of nitrous oxide and 0.15% of isoflurane (Group N). Phenylephrine (pressor test) and nicardipine (depressor test) were given to assess baroreflex sensitivity. MEASUREMENTS AND MAIN RESULTS Continuous blood pressure (BP) and electrocardiogram (ECG) were recorded before and during anesthesia to analyze heart rate (HR) variability and baroreflex sensitivity. Power spectrum of HR variability was calculated by fast Fourier transformation and power spectrum densities at low frequency (LF: 0.04-0.15Hz) and high frequency (HF: 0.15-0.40 Hz) were compared. Baroreflex sensitivity was calculated from the slope of regression for BP changes versus associated changes in R-R intervals. For HR variability, Group X showed lower power spectrum densities (ms(2).Hz(-1)) in LF and HF than did Group I (LF: 0.09 +/- 0.06 vs. 0.35 +/- 0.53; p < 0.05; HF: 0.40 +/- 0.34 vs. 0.98 +/- 0.68, p < 0.01). Group X had the lowest baroreflex sensitivity (ms.mmHg(-1)) via pressor test of the three study groups (Group X: 2.00 +/- 0.87, Group I: 3.53 +/- 2.14, Group N: 3.78 +/- 2. 17, p < 0.05). CONCLUSIONS Xenon depressed both sympathetic and parasympathetic transmission more than isoflurane at 0.8 MAC. Xenon was also suggested to be relatively vagotonic.

The Midlatency Auditory Evoked Potentials Predict Responsiveness to Verbal Commands in Patients Emerging from Anesthesia with Xenon, Isoflurane, and Sevoflurane but Not with Nitrous Oxide

Background It has recently been demonstrated that the approximately 40-Hz spectral power of the midlatency auditory evoked potential (MLAEP) correlates well with wakefulness during desflurane or propofol anesthesia. The aim of this study was to characterize how other inhalational anesthetics affects the MLAEP as the patients regain responsiveness to simple verbal command during emergence from anesthesia. Methods Sixty patients were randomly assigned to receive xenon, isoflurane, sevoflurane, or nitrous oxide (N2O) supplemented with epidural anesthesia. During emergence, the concentration of an anesthetic was decreased in 0.1-minimum alveolar concentration (MAC) decrements from 0.8 MAC or from 70% in the case of N2O, and each new concentration was maintained for 15 min. Every 5 min during each equilibration period, the MLAEP was recorded and the patients were asked to open their eyes and squeeze and release the investigator’s hand. This process was repeated until the first response to either of these commands was observed. Results Thirteen patients were excluded because of technical reasons. The preanesthetic MLAEP showed a periodic waveform, where the Na-Pa-Nb complex was the most prominent component contributing to the high energy around 29–39 Hz in the power spectrum. Emergence from xenon, isoflurane, and sevoflurane anesthesia produced similar changes in the MLAEP. The spectral power for the frequency 29 Hz or greater was severely suppressed at 0.8 MAC but significantly recovered between the concentration only 0.1 MAC higher that permitting the first response to command and that associated with the first response. In contrast, N2O hardly affected the MLAEPs, even at the concentrations producing unresponsiveness. Two patients did not lose responsiveness even at the highest concentration tested (70%). Conclusions The MLAEP is closely associated with responsiveness to verbal command during emergence from anesthesia with xenon, isoflurane, and sevoflurane but not with N2O.