Self‐administered nitrous–oxide/oxygen analgesia in obstetrics

McANENY, T. M.; Doughty, Andrew

doi:10.1111/j.1365-2044.1963.tb13573.x

Cited by 36 publications

(14 citation statements)

References 6 publications

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“…It has been observed by Kerr [7] and Heneghan et al [8] anaesthesia. Low levels of inspired oxygen are not new as 80% nitrous oxide in oxygen was used to relieve labour pain [9], for the treatment of angina [lo] and in dental anaesthesia [ll]. It can be concluded that the maintenance of the pre-operative Spo, value by using the minimum Ao, in nitrous oxide is not deleterious to patients.…”

Section: Discussionmentioning

confidence: 99%

Calculation of inspired oxygen fraction during anaesthesia based on awake oxygen saturation

Mandal

Chaudhary

1994

Anaesthesia

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SummaryOne hundred ASA grade I or 2 patients were studied to assess the use of awake oxygen saturation to determine the necessary inspired oxygen fraction during anaesthesia. The inspired oxygen fraction was adjusted gradually to the lowest possible value to maintain the pre-operative oxygen saturation at a constant level. Normocapneic ventilation was maintained and analgesia was provided with 0.5 mg.kg-' of pethidine given intravenously. In addition to routine monitoring and measurement (electrocardiograph, oxygen saturation, expired carbon dioxide concentration and noninvasive blood pressure), arterial samples for blood gas analysis and venous samples for lactate and pyruvate levels were taken when awake and 30 min after achieving a steady state with a minimum inspired oxygen fraction. The mean inspired oxygen fraction required in these patients was 20.91 (SD 1.92%) ranging from 18-25%. The arterial pH were 7.34 ( S D 4.04) (awake) and 7.35 (SD 3.15) (after 30 rnin), the partial pressure of oxygen 13.17 ( S D 1.97) (awake) and 13.83 (SD 1.6 kPa) (after 30 min) and the partial pressure of carbon dioxide and base excess were normal. Serum lactate levels were 1.04 (SD 0.25) (awake) and 1.15 (SD 0.48) (after 30 min) mmol.l-', whilst pyruvate levels were 0.1 (SD 0.02) (awake) and 0.12 (SD 0.21) (after 30 min) mmol.1-I. Patients' recovery and postoperative course were uneventful. Key wordsOxygen; blood level. Measurement techniques; pulse oximetry.It is common practice to provide at least 3 170 oxygen with nitrous oxide during anaesthesia. This concept has been well accepted by anaesthetists in past decades when proper monitoring facilities were not available [l-31. At that time anaesthetists had to depend on calculated alveolar oxygen tension (PAo,) and intermittent sampling of arterial blood to assess oxygenation. Such guesswork has been eliminated by the availability of in-line inspired oxygen (Ro,) monitors (0, analyser) and continuous noninvasive arterial oxygen saturation monitors (pulse oximeter). However, even after the recognition of these monitors as minimum standard monitoring devices, anaesthetists are still providing 31 ' YO oxygen during anaesthesia.It is known that cardiac output [4,5] does not decrease during thiopentone and nitrous oxide anaesthesia with spontaneous ventilation, and that oxygen consumption falls to approximately 15% below basal level during controlled ventilation [6]. In spite of these findings, no study has used the pre-operative arterial oxygen saturation (Spo2) value as a guide for adjustment of the intraoperative Ro2 below 31%.The main objective of this study was to determine whether the conventional 3 1 ?LO inspired oxygen fraction is necessary to maintain a constant (pre-operative) Spo, during balanced anaesthesia using nitrous oxide. MethodsOne hundred adult patients of ASA grade 1 or 2 who had no cardiac or respiratory disease or diabetes mellitus were recruited into the study. Patients were of either sex and they acted as their own control. Ethics committee approval and inf...

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Section: Discussionmentioning

confidence: 99%

Calculation of inspired oxygen fraction during anaesthesia based on awake oxygen saturation

Mandal

Chaudhary

1994

Anaesthesia

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“…Cylinders containing a 50: 50 mixture of nitrous oxide and oxygen (Gale, Tunstall and Wilton-Davies, 1964) are now available, and their use by midwives has ibeen approved by the C.M.B. The latter body has also given its approval to the Lucy Baldwin gas and oxygen 'machine i (McAneny and Doughty, 1963), a modification of an older apparatus (the Walton Five). The Lucy Baldwin may be set to deliver oxygen in concentration ranging from 30%/, in nitrous oxide, up to 100%.…”

Section: Drugsmentioning

confidence: 99%

Obstetric Analgesia and Anaesthesia—The Current Scene

Crawford

1966

Postgraduate Medical Journal

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“…The proportions of mothers who were reported to have fallen asleep during contractions were 16.6% and 21.7% with the two mixtures of nitrous oxide and oxygen. Moreover, McAneny & Doughty (1963) reported an increase in the proportion rendered unconscious during inhalation of nitrous oxide from 1% with 50% N 2 O to 5% with 80% N 2 O. The subjective median VAS (0-100 mm) score for sedation during intermittent 50% nitrous oxide analgesia was 51 mm (range 13-100) in a cross-over study by .…”

Section: Sedationmentioning

confidence: 99%

“…The Committee report did not include any information as to which proportion of the parturients received additional tranquilizers or narcotics, but noted that this was not influenced by the concentration of nitrous oxide. McAneny et al (1963) reported 22%-42% of the parturients receiving more than one injection of analgesics. Hence, at least part of the reported pain relief could have been due to the effect of the adjuvant medication.…”

Section: Analgesia With Remifentanil Epidural Block and Nitrous Oxidementioning

confidence: 99%

“…Another systematic review came to the conclusion that inhaled nitrous oxide has analgesic efficacy for relief of labour pain (Kronberg & Thompson 2005). Among the papers included in the review, Kronberg & Thompson based the conclusion on a study by McAneny et al (1963) with a dose-effect relationship observed between 50%, 60% and 70% nitrous oxide concentrations with a ceiling effect at 70%. The Committee report concerning 799 mothers using either 50% or 70% nitrous oxide, however, failed to find any difference in the analgesic effect between the two concentrations (Committee on Nitrous Oxide and Oxygen Analgesia in Midwifery 1970).…”

Section: Analgesia With Remifentanil Epidural Block and Nitrous Oxidementioning

confidence: 99%

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Intravenous patient-controlled analgesia with remifentanil in early labour

Volmanen¹

2011

Acta Anaesthesiologica Scandinavica

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Cover design Raimo Ahonen JUVENES PRINT TAMPERE 2010Volmanen, Petri, Intravenous patient controlled analgesia with remifentanil in early labour. AbstractIn four prospective clinical trials, 114 parturients used intravenous patient-controlled remifentanil analgesia during the 1 st stage of labour. The median effective dose per bolus was ascertained to be 0.4 μg/kg and the pain scores were reduced with this by a median of 2 on a numerical scale (0-10). Compared with nitrous oxide, 15 parturients included in a cross-over study reported a larger reduction in pain scores during remifentanil analgesia (1.5 vs. 0.5, p = 0.001) and better pain relief scores (2.5 vs. 0.5 on a ranked five point scale 0-4, p < 0.001). In a parallel study including 45 parturients, epidural analgesia (EDA, 20 ml bupivacaine 0.625 mg/ml and fentanyl 2 μg/ml) was associated with lower pain scores (5.2 vs. 7.3 with remifentanil, p = 0.004) but variables related to satisfaction with analgesia (pain relief score, proportion of mothers with desire to continue with the given medication and termination of the study due to inadequate pain relief) were similar. A comparison of two methods for timing the remifentanil bolus during the uterine contraction cycle suggested that delaying the bolus does not improve analgesia. A period effect was noted in the cross-over trial with higher pain scores and increased drug consumption during the second study period suggesting acute hyperalgesia.Side effects of remifentanil analgesia included respiratory depression warranting oxygen supplementation in 33% of parturients. Sedation was experienced by the parturients using remifentanil and this was scored as stronger than sedation during nitrous oxide and EDA. The number of parturients with nausea did not increase during remifentanil analgesia. Other maternal side effects included dizziness, a difficulty in visual focusing and itching. Foetal heart rate tracing abnormalities were noted. The incidence of abnormal tracings and decreased UapH were not different, however, from that observed during nitrous oxide or EDA. Apgar scores at 1 and 5 minute indicated no neonatal depression. Keywords

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Self‐administered nitrous–oxide/oxygen analgesia in obstetrics

Cited by 36 publications

References 6 publications

Calculation of inspired oxygen fraction during anaesthesia based on awake oxygen saturation

Calculation of inspired oxygen fraction during anaesthesia based on awake oxygen saturation

Obstetric Analgesia and Anaesthesia—The Current Scene

Intravenous patient-controlled analgesia with remifentanil in early labour

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