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Meta-Analysis
. 2012 Sep 12;2012(9):CD009351.
doi: 10.1002/14651858.CD009351.pub2.

Inhaled analgesia for pain management in labour

Trudy Klomp  1 , Mireille van Poppel, Leanne Jones, Janine Lazet, Marcello Di Nisio, Antoine L M Lagro-Janssen
Affiliations
Meta-Analysis

Inhaled analgesia for pain management in labour

Trudy Klomp et al. Cochrane Database Syst Rev. .

Abstract

Background: Many women would like to have a choice in pain relief during labour and also would like to avoid invasive methods of pain management in labour. Inhaled analgesia during labour involves the self-administered inhalation of sub-anaesthetic concentrations of agents while the mother remains awake and her protective laryngeal reflexes remain intact. Most of the agents are easy to administer, can be started in less than a minute and become effective within a minute.

Objectives: To examine the effects of all modalities of inhaled analgesia on the mother and the newborn for mothers who planned to have a vaginal delivery.

Search methods: We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (31 January 2012), ClinicalTrials.gov, and Current Controlled Trials (2 June 2012), handsearched conference proceedings from the American Society of Clinical Anesthesia (from 1990 to 2011), contacted content experts and trialists and searched reference lists of retrieved studies.

Selection criteria: Randomised controlled trials comparing inhaled analgesia with other inhaled analgesia or placebo or no treatment or other methods of non-pharmacological pain management in labour.

Data collection and analysis: Review authors independently assessed trials for eligibility, methodological quality and extracted all data. Data were double checked for accuracy.

Main results: Twenty-six studies, randomising 2959 women, were included in this review.Inhaled analgesia versus a different type of inhaled analgesia Pain relief was measured using a Visual Analogue Scale (VAS) from 0 to 100 mm where 100 corresponds to the most relief. Pain intensity was measured using a VAS from 0 to 100 mm, where 0 corresponds to no pain at all and 100 corresponds to the worst pain. The highest score for pain relief is the most positive in contrast to 'pain intensity' in which the higher score is more negative. Flurane derivatives were found to offer better pain relief than nitrous oxide in first stage of labour as measured by a lower pain intensity score (average mean difference (MD) 14.39, 95% confidence interval (CI) 4.41 to 24.37, three studies, 70 women), also a higher pain relief score for flurane derivatives compared with nitrous oxide (average MD -16.32, 95% CI -26.85 to -5.79, two studies, 70 women). Substantial heterogeneity was found in the analyses of pain intensity (P = 0.003) and in the analysis of pain relief (P = 0.002).These findings should be considered with caution because of the questionable design of the included cross-over trials. More nausea was found in the nitrous oxide group compared with the flurane derivatives group (risk ratio (RR) 6.60 95% CI 1.85 to 23.52, two studies, 98 women).Inhaled analgesia versus placebo or no treatment Placebo or no treatment was found to offer less pain relief compared to nitrous oxide (average RR 0.06, 95% CI 0.01 to 0.34, two studies, 310 women; MD -3.50, 95% CI -3.75 to -3.25, one study, 509 women). However, nitrous oxide resulted in more side effects for women such as nausea (RR 43.10, 95% CI 2.63 to 706.74, one study, 509 women), vomiting (RR 9.05, 95% CI 1.18 to 69.32, two studies, 619 women), dizziness (RR 113.98, 95% CI 7.09 to 1833.69, one study, 509 women) and drowsiness (RR 77.59, 95% CI 4.80 to 1254.96, one study, 509 women) when compared with placebo or no treatment.There were no significant differences found for any of the outcomes in the studies comparing one strength versus a different strength of inhaled analgesia, in studies comparing different delivery systems or in the study comparing inhaled analgesia with TENS.Due to lack of data, the following outcomes were not analysed within the review: sense of control; satisfaction with childbirth experience; effect on mother/baby interaction; breastfeeding; admission to special care baby unit; poor infant outcomes at long-term follow-up; or costs.

Authors' conclusions: Inhaled analgesia appears to be effective in reducing pain intensity and in giving pain relief in labour. However, substantial heterogeneity was detected for pain intensity. Furthermore, nitrous oxide appears to result in more side effects compared with flurane derivatives. Flurane derivatives result in more drowsiness when compared with nitrous oxide. When inhaled analgesia is compared with no treatment or placebo, nitrous oxide appears to result in even more side effects such as nausea, vomiting, dizziness and drowsiness. There is no evidence for differences for any of the outcomes comparing one strength verus a different strength of inhaled analgesia, comparing different delivery systems or comparing inhaled analgesia with TENS.

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Conflict of interest statement

None known.

Figures

1
1
'Risk of bias' graph: review authors' judgements about each risk of bias item presented as percentages across all included studies.
2
2
'Risk of bias' summary: review authors' judgements about each risk of bias item for each included study.
1.1
1.1. Analysis
Comparison 1 Nitrous oxide versus flurane derivatives, Outcome 1 Pain intensity (VAS 0‐100 first stage).
1.2
1.2. Analysis
Comparison 1 Nitrous oxide versus flurane derivatives, Outcome 2 Pain relief (VAS 0‐100 as 100 is the most pain relief, first stage).
1.3
1.3. Analysis
Comparison 1 Nitrous oxide versus flurane derivatives, Outcome 3 Satisfaction with pain relief (first and second stage, considerable to complete).
1.4
1.4. Analysis
Comparison 1 Nitrous oxide versus flurane derivatives, Outcome 4 Satisfaction with pain relief (second stage, good to excellent).
1.5
1.5. Analysis
Comparison 1 Nitrous oxide versus flurane derivatives, Outcome 5 Assisted vaginal birth.
1.6
1.6. Analysis
Comparison 1 Nitrous oxide versus flurane derivatives, Outcome 6 Caesarean section.
1.7
1.7. Analysis
Comparison 1 Nitrous oxide versus flurane derivatives, Outcome 7 Amnesia.
1.8
1.8. Analysis
Comparison 1 Nitrous oxide versus flurane derivatives, Outcome 8 Drowsiness (VAS 0‐100 mm).
1.9
1.9. Analysis
Comparison 1 Nitrous oxide versus flurane derivatives, Outcome 9 Nausea.
1.10
1.10. Analysis
Comparison 1 Nitrous oxide versus flurane derivatives, Outcome 10 Vomiting.
1.11
1.11. Analysis
Comparison 1 Nitrous oxide versus flurane derivatives, Outcome 11 Blood loss in mL.
1.12
1.12. Analysis
Comparison 1 Nitrous oxide versus flurane derivatives, Outcome 12 Apgar score less than seven at five minutes.
1.13
1.13. Analysis
Comparison 1 Nitrous oxide versus flurane derivatives, Outcome 13 NACS < 35 at 2 hours after delivery.
2.1
2.1. Analysis
Comparison 2 Inhaled analgesia of one strength versus inhaled analgesia of different strength, Outcome 1 Satisfaction with pain relief (first stage, good to complete).
2.2
2.2. Analysis
Comparison 2 Inhaled analgesia of one strength versus inhaled analgesia of different strength, Outcome 2 Satisfaction with pain relief (second stage, good to complete).
2.3
2.3. Analysis
Comparison 2 Inhaled analgesia of one strength versus inhaled analgesia of different strength, Outcome 3 Caesarean section.
2.4
2.4. Analysis
Comparison 2 Inhaled analgesia of one strength versus inhaled analgesia of different strength, Outcome 4 Assisted vaginal birth.
2.5
2.5. Analysis
Comparison 2 Inhaled analgesia of one strength versus inhaled analgesia of different strength, Outcome 5 Vomiting.
2.6
2.6. Analysis
Comparison 2 Inhaled analgesia of one strength versus inhaled analgesia of different strength, Outcome 6 Postpartum haemorrhage.
2.7
2.7. Analysis
Comparison 2 Inhaled analgesia of one strength versus inhaled analgesia of different strength, Outcome 7 Hypoxaemia mother.
3.1
3.1. Analysis
Comparison 3 Inhaled analgesia using one type of delivery system versus a different delivery system, Outcome 1 Satisfaction with pain relief (first stage, considerable to complete).
3.2
3.2. Analysis
Comparison 3 Inhaled analgesia using one type of delivery system versus a different delivery system, Outcome 2 Caesarean section.
3.3
3.3. Analysis
Comparison 3 Inhaled analgesia using one type of delivery system versus a different delivery system, Outcome 3 Vomiting (N2O + nasal).
3.4
3.4. Analysis
Comparison 3 Inhaled analgesia using one type of delivery system versus a different delivery system, Outcome 4 Vomiting dichotomous Penthr./Cypr..
3.5
3.5. Analysis
Comparison 3 Inhaled analgesia using one type of delivery system versus a different delivery system, Outcome 5 Postpartum haemorrhage.
3.6
3.6. Analysis
Comparison 3 Inhaled analgesia using one type of delivery system versus a different delivery system, Outcome 6 Mild pre‐eclampsia.
3.7
3.7. Analysis
Comparison 3 Inhaled analgesia using one type of delivery system versus a different delivery system, Outcome 7 Apgar score (continuous, at 5 min.Penthr/Cypr).
3.8
3.8. Analysis
Comparison 3 Inhaled analgesia using one type of delivery system versus a different delivery system, Outcome 8 Apgar score (continuous N2O/N2O with nasal suppl.).
4.1
4.1. Analysis
Comparison 4 Inhaled analgesia versus placebo control/no treatment, Outcome 1 Pain intensity (first stage, clear/severe to intense/extreme).
4.2
4.2. Analysis
Comparison 4 Inhaled analgesia versus placebo control/no treatment, Outcome 2 Pain intensity (first stage, VAS 0‐10 after 1 hour).
4.3
4.3. Analysis
Comparison 4 Inhaled analgesia versus placebo control/no treatment, Outcome 3 Assisted vaginal birth.
4.4
4.4. Analysis
Comparison 4 Inhaled analgesia versus placebo control/no treatment, Outcome 4 Caesarean section.
4.5
4.5. Analysis
Comparison 4 Inhaled analgesia versus placebo control/no treatment, Outcome 5 Vomiting.
4.6
4.6. Analysis
Comparison 4 Inhaled analgesia versus placebo control/no treatment, Outcome 6 Nausea.
4.7
4.7. Analysis
Comparison 4 Inhaled analgesia versus placebo control/no treatment, Outcome 7 Dizziness.
4.8
4.8. Analysis
Comparison 4 Inhaled analgesia versus placebo control/no treatment, Outcome 8 Drowsiness.
4.9
4.9. Analysis
Comparison 4 Inhaled analgesia versus placebo control/no treatment, Outcome 9 Neonatal asphyxia.
4.10
4.10. Analysis
Comparison 4 Inhaled analgesia versus placebo control/no treatment, Outcome 10 Apgar score 5 min. ⋜ 7 dich..
4.11
4.11. Analysis
Comparison 4 Inhaled analgesia versus placebo control/no treatment, Outcome 11 Apgar score 5 min.cont..
5.1
5.1. Analysis
Comparison 5 Inhaled analgesia versus TENS, Outcome 1 Satisfaction pain relief first period ordinal partial to complete.
5.2
5.2. Analysis
Comparison 5 Inhaled analgesia versus TENS, Outcome 2 Pain intensity first period ordinal moderate to severe.
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