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PubMed1989

[Nitrous oxide in anesthesia--present status of the use of nitrous oxide, risks for patients and personnel and treatment of side effects].

Mechanisms of some effects of nitrous oxide have recently been elucidated. Its antinociceptive action depends partly on the involvement of the endorphinergic system. Although vitamin B 12 becomes biologically inactive in the presence of nitrous oxide, this certainly is of no clinical consequence in exposures lasting less than eight hours. Should exposures last over 8 hours, effects of vitamin B 12 inactivation can be compensated for by administration of folinic acid. In contrast, professional exposure to trace levels of nitrous oxide seems not to interfere with human health. Furthermore, closed circle apparatus should be used and operating room air be well scavenged when nitrous oxide is used.

Anesthesia, Inhalation↗
PubMed1990

Randomized comparison of recovery after propofol-nitrous oxide versus thiopentone-isoflurane-nitrous oxide anaesthesia in patients undergoing ambulatory surgery.

A randomized, prospective study was performed to compare recovery characteristics in 41 ASA physical status I-II patients scheduled for ambulatory surgery with either propofol or thiopentone-isoflurane anaesthesia. Particular attention was focused on the recovery time needed to meet discharge criteria. The propofol group received propofol 2 mg.kg-1 for induction followed by propofol infusion (6-9 mg.kg-1.h-1) 1 min after intubation. The thiopentone-isoflurane group received thiopentone 4 mg.kg-1 for induction followed by isoflurane (0.5-2%) 1 min after endotracheal intubation. Other drugs administered during or after anaesthesia were similar between the groups. The propofol group had significantly (P less than 0.05) faster clinical recovery than the isoflurane group with respect to times to response to commands, eye opening, orientation, ability to stand and void, tolerance to oral fluids, "home-readiness", and recovery of perceptual speed. Patients in the propofol group had significantly less (P less than or equal to 0.05) emesis than the patients given isoflurane. We conclude that in patients undergoing ambulatory surgery propofol infusion is preferable to thiopentone-isoflurane anaesthesia, because it may allow faster discharge home.

Adult↗
PubMed1993

Comparison of cardiovascular changes during anaesthesia and recovery from propofol-alfentanil-nitrous oxide and thiopentone-halothane-nitrous oxide anaesthesia in children undergoing otolaryngological surgery.

Propofol/alfentanil anaesthesia was compared with thiopentone/halothane anaesthesia in 86 midazolam-atropine premedicated children undergoing minor otolaryngological surgery. The study was randomised, and evaluation of recovery from anaesthesia was double-blind. The children were divided into two age groups: 1-3 years and 4 years and older. Particular attention was paid to ECG changes during anaesthesia and to the rapidity of recovery. One minute after alfentanil 15 micrograms.kg-1, the children in the propofol group received propofol 2.0-3.0 mg.kg-1 followed by propofol infusion 15 mg.kg-1.h-1. In addition, 0.1% suxamethonium 6 mg.kg-1.h-1 was infused during operation. The other children received thiopentone 5-7 mg.kg-1 followed by halothane (0.5-2%) immediately after endotracheal intubation. Junctional rhythm occurred in 5-35% of the children independent of anaesthesia method, and ventricular ectopic beats were seen in 20% of the older children during halothane anaesthesia. Recovery with respect to times to eye opening or response to verbal contact was significantly faster after propofol/alfentanil anaesthesia than after thiopentone/halothane anaesthesia in the older but not in the younger age group. Furthermore, in the younger age group significantly more crying occurred after propofol/alfentanil than after thiopentone/halothane anaesthesia. On the basis of this study, thiopentone/halothane anaesthesia is recommended for children aged 1-3 years and propofol/alfentanil anaesthesia for older children undergoing adenoidectomy and/or tonsillectomy.

Alfentanil↗
PubMed1996

Effect of nitrous oxide on middle ear pressure: a comparison between inhalational anaesthesia with nitrous oxide and TIVA.

We have investigated the effect of nitrous oxide on the middle ear pressure, comparing inhalational anaesthesia with nitrous oxide and halothane and total intravenous anaesthesia with propofol-alfentanil. Fifty patients with normal healthy ears were divided into two groups. In one group (n = 25), anaesthesia was induced with thiopentone 6 mg kg-1, and maintained with halothane 1% and nitrous oxide 66% in oxygen. In the other group (n = 25), anaesthesia was induced with alfentanil 25 micrograms kg-1 and propofol 2 mg kg-1, and maintained with an infusion of alfentanil 10 micrograms kg-1 min-1 for the first 10 min and then with 0.5 microgram kg-1 min-1 and with propofol 10 mg kg-1 h-1 for the first 10 min, 8 mg kg-1 h-1 for the following 10 min and 6 mg kg-1 h-1 thereafter. Patients were ventilated with an oxygen-air mixture (F1O2 = 0.33). Middle ear pressures were measured during the pre-, intra- and post-anaesthetic period in both ears. A progressive rise was observed (P < 0.05) in the first group, whereas values were within the normal limits clinically and there was no statistically significant change in those receiving total intravenous anaesthesia during the intra-anaesthetic period. The time to reach peak pressure with inhalational anaesthesia was 60 min (181.5 mmH2O) and to return to normal was 30 min (49.5 mmH2O) after cessation of nitrous oxide administration. The incidence of nausea and vomiting was less in the patients not receiving nitrous oxide.

Adolescent↗
PubMed1975

[The use of nitrous oxide as a contrast medium during fractionated gas encephalography in halane-nitrous-oxide anesthesia].

40 children were employed as test cases in fractionated gas encephalography using Halan-nitrous oxide anesthesia, and the level of cerebrospinal pressure, the röntgenoparent quality of the extracerebral spaces and the duration of postencephalographical symptoms were examined using air and nitrous oxide as contrast media. In the course of the examination the cerebrospinal pressure showed a tendency to rise when air was introduced, to fall when nitrous oxide was introduced. After instillation of N2O however the filling of the subarachnoid space was over so quickly that it could not be included in the assessment. Sufficient röntgenograms were obtained for all diagnostic demands through 'hybrid filling', (introduction of nitrous oxide into the ventricles, introduction of air into the subarachnoid spaces). With the aid of the results obtained from this examination attempts will be made to derive differentiated indications for filling with nitrous oxide.

Adolescent↗
PubMedDate not supplied

The differential cost of anesthesia and recovery with propofol-nitrous oxide anesthesia versus thiopental sodium-isoflurane-nitrous oxide anesthesia.

STUDY OBJECTIVE: To assess the recovery room profile of propofol in outpatient anesthesia and to compare it to the profile of a standard technique. DESIGN: A comparative, randomized, double-blind, third-party open study. SETTING: Ambulatory Surgery Center at The Emory Clinic. PATIENTS: Ninety-nine ASA physical status I, II, or III nonpregnant female patients who had been diagnosed as needing breast biopsies. INTERVENTIONS: All patients were given 1 microgram/kg of fentanyl prior to induction. Those in the propofol group were induced with 2.0 to 2.5 mg/kg of propofol and maintained with a 100 to 200 microgram/kg/min infusion of propofol with nitrous oxide (N2O) in oxygen (O2). In the thiopental sodium-isoflurane group, patients were induced with 4.0 to 5.0 mg/kg of thiopental sodium and maintained with isoflurane and N2O in O2. MEASUREMENTS AND MAIN RESULTS: Recovery from anesthesia was assessed by an evaluator who was unaware of the anesthetic technique used for each patient. Immediate recovery time was measured in terms of awakening, response to verbal command, and orientation to time and place. A brief postoperative follow-up questionnaire was completed to assess the patients' subjective feelings regarding their ability to eat, concentrate, and resume normal activities. In the thiopental sodium-isoflurane group, 15 of 50 patients (30%) had nausea and vomiting, but in the propofol group, only 4 of 49 patients (8.1%) had nausea and vomiting (p less than 0.01). The latter group resumed normal activity (i.e., reading and watching television) 7.93 +/- 0.76 hours postanesthesia, whereas the thiopental sodium-isoflurane group resumed normal activity 17.02 +/- 1.21 hours postanesthesia (p less than 0.001). Patients in the propofol group returned to work in an average of 1.5 +/- 0.09 days, compared with 2.0 +/- 0.09 days for the thiopental sodium-isoflurane group (p less than 0.001). CONCLUSIONS: The propofol group needed less nursing care and returned to more productive activity earlier than did the thiopental sodium-isoflurane group.

Ambulatory Surgical Procedures↗
PubMed1992

Continuous intravenous propofol with nitrous oxide for ocular surgery. A comparison with etomidate, alfentanil, nitrous oxide and isoflurane.

Propofol, administered intravenously for induction and as a continuous maintenance anaesthetic with nitrous oxide, was compared, in a group of elderly patients scheduled for ophthalmic surgery, with an anaesthetic technique (etomidate, alfentanil, nitrous oxide and isoflurane) specifically chosen to be haemodynamically stable and evanescent in action. Both techniques resulted in similar effects on blood pressure after induction, intubation and surgical incision, but propofol did not prevent increases in heart rate as effectively at these times. Furthermore, during maintenance anaesthesia, cardiovascular stability and anaesthetic depth were more easily achieved in the group where etomidate, alfentanil and isoflurane were used. Propofol decreased intra-ocular pressure after intubation, while in both groups recovery was rapid with no significant complications. A subgroup of patients receiving alpha-methyldopa had significantly longer post-anaesthetic recovery times.

Aged↗
PubMed1970

Clinical trials of different concentrations of oxygen and nitrous oxide for obstetric analgesia. Report to the Medical Research Council of the Committee on Nitrous Oxide and Oxygen Analgesia in Midwifery.

Trials have been organized by a Medical Research Council committee to assess the effectiveness and safety for analgesia in labour of oxygen and nitrous oxide mixtures in different proportions. In a preliminary trial concentrations of 50% and 60% v/v nitrous oxide were compared, but, as the replies of 409 mothers revealed little difference between the two, the results of administering either 50% or 70% nitrous oxide to 778 mothers were then compared. The data relating to normal labour, obtained on 501 of the mothers in this main trial, showed that the relief of pain given was much the same. There was a suggestion, however, that the higher concentration of nitrous oxide might be useful in abnormal labour. The proportion of mothers with normal deliveries who lost consciousness, though very small, was significantly higher with 70% nitrous oxide than with the lower concentration. Ninety-two per cent. of mothers found the gas and oxygen machine helpful, and midwives reported complete or good co-operation by 77% of those using it. It is concluded that the 50% oxygen and 50% nitrous oxide mixture can safely be used by unsupervised midwives.

Anesthesia, Obstetrical↗
PubMed2005

Biogenesis of the bacterial respiratory CuA, Cu-S enzyme nitrous oxide reductase.

Nitrous oxide reductase (NosZ, EC 1.7.99.6) is the terminal oxidoreductase of a respiratory electron transfer chain that transforms nitrous oxide to dinitrogen. The enzyme carries six Cu atoms. Two are arranged in the mixed-valent binuclear CuA site, and four make up the mu4-sulfide-bridged Cu cluster, CuZ. The biogenesis of a catalytically active NosZ requires auxiliary functions for metal center assembly in the periplasm. Both Tat and Sec pathways share the task to transport the various Nos proteins to their functional sites. Biogenesis of NosZ requires an ABC transporter complex and the periplasmic Cu chaperone NosL. Sustaining whole-cell NosZ function depends on the periplasmic, FAD-containing protein NosX, and the membrane-bound iron-sulfur flavoprotein NosR. Most components with a biogenetic function are now amenable to structural studies.

ATP-Binding Cassette Transporters↗
PubMed1990

Effect of scavenging on ambient levels of nitrous oxide in ambulances.

Nitrous oxide scavenging devices have not been tested in the prehospital setting. We studied two nitrous oxide scavenging devices and their effect on ambient levels of nitrous oxide in the patient compartment of a stationary ambulance. We compared the ambient levels of gas when nitrous oxide scavenging was in use versus when it was not. In addition, we evaluated the effect of two different mask designs on ambient levels of nitrous oxide. With eight healthy male volunteers acting as their own controls using a series of mask/scavenger combinations, we found that there was a significant difference in the ambient levels of nitrous oxide when a scavenger was in use. The mean time-weighted average was 776 parts per million/min when no scavenger was used. When gas scavenging was in use, the mean time-weighted average never exceeded 150 parts per million/min. (P less than .0001). There was no significant difference between nitrous oxide scavengers or between the masks tested in their effect on nitrous oxide ambient levels in the atmosphere. We conclude that nitrous oxide scavengers are effective in lowering nitrous oxide ambient levels in the prehospital setting and merit consideration as adjuncts to nitrous oxide delivery systems in this setting.

Air Pollutants, Occupational↗
PubMed1994

Inhibitors of nitric oxide synthesis antagonize nitrous oxide antinociception in mice and rats.

Administration of the anesthetic gas N2O evoked an antinociceptive effect in two rodent antinociception paradigms. In the mouse abdominal constriction test, pretreatment with the nitric oxide synthase (NOS) inhibitor L-NG-nitroarginine (L-NOARG) caused dose-related antagonism of the antinociceptive effect of N2O but not of either morphine or trans(+/-)-3,4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl)cyclohexyl] benzeneacetamide methane sulfonate. This antinociceptive effect was also antagonized by systemic pretreatment with the NOS inhibitors L-NG-nitroarginine methyl ester (L-NAME) and L-NG-monomethylnitroarginine. The antagonism of N2O by L-NOARG and L-NAME was completely reversed by i.c.v. administration of L-arginine but not D-arginine. In the absence of NOS inhibition, N2O antinociception was potentiated by i.c.v. treatment with L-arginine but not D-arginine. The i.c.v. pretreatment with L-NAME also reduced N2O antinociception; this antagonism was also stereospecifically reversed by L-arginine. In the rat hot plate test, the antinociceptive response to 70% N2O was antagonized in dose-related manner by i.c.v. pretreatment with L-NOARG or L-NAME. N2O antinociception was restored by i.c.v. treatment with L-arginine but not D-arginine. However, neither L-arginine nor D-arginine alone affected N2O antinociception. These results implicate a key role for NO in the mediation of the antinociceptive effects of N2O in both mice and rats.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗
PubMed1987

[Nitrous oxide in combination anesthesia. Quantitative aspects of the effect of nitrous oxide].

UNLABELLED: Minimal Alveolar Concentration (MAC) defines the anesthetic potency of nitrous oxide (N2O) combined with an inhalational anesthetic only for the moment of skin incision. For the complete operation, the proportional action of N2O is unknown. This prospective, randomized study reports the mean intraoperative concentration (MIC) of halothane with and without 70% N2O in combination with premedication, i.v. induction, and muscle relaxation for the duration of operation. METHODS: Forty ASA I-II patients scheduled for hysterectomies gave informed consent. All patients received atropine 0.5 mg, promethazine and pethidine 1 mg/kg i.m. 30-45 min prior to anesthesia, i.v. induction with thiopental, and neuromuscular blockade with alcuronium at the beginning of the operation. Post-induction, patients received randomized halothane in 30% O2/70% N2 (group 1, n = 20) or in 30% O2/70% N2O (group 2, n = 20). In the course of this observation (before induction and up to 15 min after extubation), the following parameters were measured (Table 1): arterial pressure (AP), heart rate (HR), plasma concentrations of growth hormone, prolactin, and cortisol in central venous blood, esophageal temperature, "train-of-four" ratio, and expiratory CO2 concentration. MIC had been computed from the integral of end-expiratory halothane concentration during the course of the operation. RESULTS: Biometric data and concomitant conditions were equivalent within the two groups (Table 2). MIC halothane was 0.72 +/- 0.014 vol% in group 1 (O2/N2) and 0.52 +/- 0.01 vol% in group 2 (O2/N2O).(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia, Inhalation↗
PubMed1993

Low-flow isoflurane-nitrous oxide anaesthesia offers substantial economic advantages over high- and medium-flow isoflurane-nitrous oxide anaesthesia.

Isoflurane consumption was studied for three different fresh gas flows in patients scheduled for major elective abdominal, urological or gynaecological surgery under general anaesthesia with an expected duration of 2 h or more. Thirty patients were randomly assigned to either high-flow anaesthesia using a partial rebreathing system without carbon dioxide absorption (Mapleson D) or medium- or low-flow anaesthesia using a circle system with carbon dioxide absorption. Patients were anaesthetised with isoflurane in 40% oxygen and 60% nitrous oxide. The amount of isoflurane consumed was measured with a precision scale. The total consumption of liquid isoflurane (mean +/- s.d.) during the first 2 h was 40.8 +/- 12.2 ml in the high-flow group, 18.5 +/- 5.4 ml in the medium-flow group and 7.9 +/- 2.2 ml in the low-flow group. The corresponding cost of isoflurane for the three groups was 214 Danish kroner (DKK) (19.5 pounds), 97 DKK (8.8 pounds) and 42 DKK (3.8 pounds), respectively. The calculated total cost of anaesthetics was 286 DKK (26 pounds), 155 DKK (14.1 pounds) and 91 DKK (8.3 pounds), respectively. In conclusion, low-flow isoflurane-nitrous oxide anaesthesia offers substantial economic advantages over high- and medium-flow isoflurane-nitrous oxide anaesthesia.

Adult↗
PubMed1983

Catecholamine mechanisms in the stimulation of mouse locomotor activity by nitrous oxide and morphine.

Nitrous oxide, like morphine, produces a significant increase in mouse locomotor activity. This stimulation of locomotor activity is antagonized by the narcotic antagonist naloxone (10 mg/kg). The catecholamine synthesis inhibitor alpha-methyl-p-tyrosine (300 mg/kg) also significantly reduced the nitrous oxide stimulation of mouse locomotor activity. Administration of naloxone (10 mg/kg) to mice previously treated with alpha-methyl-p-tyrosine resulted in a further decrease in nitrous oxide stimulated activity levels. Haloperidol (0.08-0.64 mg/kg), a potent dopamine receptor antagonist, dose dependently reduced the activity stimulation resulting from exposure to nitrous oxide. Administration of haloperidol (0.08 mg/kg) in conjunction with naloxone (10 mg/kg) further reduced the nitrous oxide effect. In view of the fact that morphine's activity stimulating effects are reduced by alpha-methyl-p-tyrosine and haloperidol, the results reported here suggest additional similarities in the pharmacology of morphine and nitrous oxide. The stimulation of mouse locomotor activity produced by nitrous oxide appears to be mediated by both endogenous opioid and catecholamines.

Animals↗
PubMed1983

Subacute toxic delirium following nitrous oxide abuse.

Nitrous oxide (N2O) abuse has been associated with myeloneuropathy, but significant mental status changes rarely have been described. We treated a patient in whom a subacute delirium developed after heavy N2O abuse; symptoms slowly cleared over three weeks after removal of the neurotoxin.

Acute Disease↗