Analgesia for forceps delivery
Abstract
This is a protocol for a Cochrane Review (Intervention). The objectives are as follows:
To assess the effects of different analgesic agents and methods available for forceps delivery, including safety for women and their babies.
Background
Forceps have been used since the 17th century to help deliver live babies by applying traction to the fetal head (Ross 2008). In these times, it was common for women to be heavily sedated during labour and childbirth. Around the middle of the last century, women undergoing forceps deliveries were often given a general anaesthetic, but it soon became clear that using a general anaesthetic for this purpose was associated with significant maternal morbidity and mortality. Use of general anaesthesia for forceps delivery is now rare, with Laws 2009 reporting that in Australia in 2007, only three in 1000 women undergoing an instrumental delivery (vacuum or forceps) were administered a general anaesthetic. Gate 1955 trialed the use of local analgesia for forceps delivery in 65 women, finding improvements in maternal and perinatal morbidity, as well as greater maternal satisfaction. A short time later, O'Sullivan 1962 described the use of pethilorfan (pethidine, levallorphan and promethazine) administered as a slow intravenous injection for forceps delivery, which causes the woman to fall asleep but wake with each contraction. Since then, various forms of local and regional anaesthesia have become the mainstay of analgesia for forceps delivery.
The type of forceps to be used depends on the specific indications and conditions. The most commonly used forceps are Simpson forceps, which are used to deliver a moulded fetal head, as is commonly seen in nulliparous women. Also commonly used are Tucker‐McLane forceps, which have a more rounded cephalic curve, more suitable for the unmoulded fetal head commonly seen in multiparous women (Ross 2008).
Description of the condition
Typically, forceps are used when a singleton fetus in the cephalic position fails to progress to delivery or when delivery needs to be expedited in the second stage of labour because of fetal distress. Indications for forceps delivery include delay or maternal exhaustion in the second stage of labour; dense epidural block with diminished urge to push; suspected fetal distress; maternal medical conditions (e.g. cardiac, respiratory or neurologic) that preclude pushing (Patel 2004).
Forceps deliveries are no longer common, with a report from the US stating that they comprise less than 3% of all births (Ross 2008). In 2007, the corresponding rate for Australia was 3.6%, whereas instrumental deliveries comprised 11.1% of all, with ventouse deliveries being 7.5% (Laws 2009).
Description of the intervention
Regional analgesia, especially epidurals, is often used in forceps deliveries. For example, Laws 2009 reports that in Australia, nearly 50% of instrumental births (vacuum and forceps) used epidural or caudal methods. However, women may request an epidural block during their labour and it will be topped up when doing a forceps delivery if indicated.
Local anaesthetics (such as pudendal blocks or local infiltration) are also commonly used, although regional anaesthesia is often considered to be a better option than local for forceps delivery (Gibbs 2008).
How the intervention might work
Effective analgesia will ensure that the woman remains as comfortable as possible throughout the forceps procedure and subsequently. It will also help the obstetrician perform the procedure safely. While the aim of analgesia is to give sufficient coverage with the least amount of pain and adverse effects, different analgesic types and methods will vary in their capacity to balance anaesthetic coverage, pain relief and avoidance of adverse effects.
Why it is important to do this review
It will be very helpful if we could assess the effects of different types of available analgesic options for forceps delivery with their efficacy and side effects, so obstetricians could choose from the safest and most efficient methods with the fewest side effects.
Objectives
To assess the effects of different analgesic agents and methods available for forceps delivery, including safety for women and their babies.
Methods
Criteria for considering studies for this review
Types of studies
We will include all identified randomised and quasi‐randomised trials assessing and comparing the effectiveness and/or adverse effects of different analgesics for forceps delivery as well as those ones presented only as abstracts. We will not include any cluster‐randomised and crossover trials.
Types of participants
Pregnant women in the second stage of labour undergoing forceps delivery for any indication. This will include all singleton and twin deliveries with cephalic and breech presentation.
Types of interventions
Different methods, any mode or combination of analgesics versus the other pharmacological agents and compared to placebo.
Types of outcome measures
Primary outcomes
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Pain relief, however measured by the authors
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Maternal mortality or serious morbidity (as defined by trial authors) e.g. dural puncture, meningitis or long‐term backache arising from the analgesic method used
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Neonatal mortality or serious morbidity (as defined by trial authors) e.g. fetal distress, low Apgar score less than seven at five minutes, need for neonatal intensive care unit (NICU) or special care neonatal admission arising from the method used
Secondary outcomes
Maternal
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Maternal satisfaction with childbirth experience
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Request for additional analgesia
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Mother‐baby bonding (as defined by trial authors)
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Maternal hypotension as a result of regional anaesthesia (as defined by authors)
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Postnatal depression (authors' definition, treatment for depression or self reported)
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Breastfeeding success and duration (as defined by trial authors)
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Motor blockade
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Respiratory depression requiring oxygen administration
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Headache
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Headache requiring blood patch
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Vomiting
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Itching
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Fever
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Shivers
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Drowsiness
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Urinary retention
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Duration of postpartum hospital stay
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Postpartum hospital admission within six weeks of discharge
Neonate
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Acidosis as defined by cord blood arterial pH less than 7.2
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Acidosis as defined by cord blood arterial pH less than 7.15
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Naloxone administration
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Neonatal intensive care unit (NICU) admission
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Low Apgar score less than seven at five minutes
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Neonatal hypoglycaemia (less than or equal to 1.67 mmol/l)
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Long‐term neonatal complication (e.g. seizures, disability in childhood)
Search methods for identification of studies
Electronic searches
We will contact the Trials Search Co‐ordinator to search the Cochrane Pregnancy and Childbirth Group’s Trials Register.
The Cochrane Pregnancy and Childbirth Group’s Trials Register is maintained by the Trials Search Co‐ordinator and contains trials identified from:
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quarterly searches of the Cochrane Central Register of Controlled Trials (CENTRAL);
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weekly searches of MEDLINE;
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handsearches of 30 journals and the proceedings of major conferences;
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weekly current awareness alerts for a further 44 journals plus monthly BioMed Central email alerts.
Details of the search strategies for CENTRAL and MEDLINE, the list of handsearched journals and conference proceedings, and the list of journals reviewed via the current awareness service can be found in the ‘Specialized Register’ section within the editorial information about the Cochrane Pregnancy and Childbirth Group.
Trials identified through the searching activities described above are each assigned to a review topic (or topics). The Trials Search Co‐ordinator searches the register for each review using the topic list rather than keywords.
Searching other resources
We will review published guidelines and search the reference lists of review articles.
We will not apply any language restrictions.
Data collection and analysis
Selection of studies
Two review authors will independently assess for inclusion all the potential studies we identify as a result of the search strategy. We will resolve any disagreement through discussion or, if required, we will consult a third person.
Data extraction and management
We will design a form to extract data. For eligible studies, two review authors will extract the data using the agreed form. We will resolve discrepancies through discussion or, if required, we will consult a third person. We will enter data into Review Manager software (RevMan 2008) and check for accuracy.
When information regarding any of the above is unclear, we will attempt to contact authors of the original reports to provide further details
Assessment of risk of bias in included studies
Two review authors will independently assess risk of bias for each study using the criteria outlined in the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2009). We will resolve any disagreement by discussion or by involving a third assessor. In cluster‐randomised trials we will use the appropriate methods for assessing bias.
(1) Sequence generation (checking for possible selection bias)
We will describe for each included study the method used to generate the allocation sequence in sufficient detail to allow an assessment of whether it should produce comparable groups.
We will assess the method as:
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adequate (any truly random process, e.g. random number table; computer random number generator);
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inadequate (any non‐random process, e.g. odd or even date of birth; hospital or clinic record number); or
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unclear.
(2) Allocation concealment (checking for possible selection bias)
We will describe for each included study the method used to conceal the allocation sequence and determine whether intervention allocation could have been foreseen in advance of, or during recruitment, or changed after assignment.
We will assess the methods as:
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adequate (e.g. telephone or central randomisation; consecutively numbered sealed opaque envelopes);
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inadequate (open random allocation; unsealed or non‐opaque envelopes, alternation; date of birth);
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unclear.
(3) Blinding (checking for possible performance bias)
We will describe for each included study the methods used, if any, to blind study participants and personnel from knowledge of which intervention a participant received. We will consider that studies are at low risk of bias if they were blinded, or if we judge that the lack of blinding could not have affected the results. We will assess blinding separately for different outcomes or classes of outcomes.
We will assess the methods as:
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adequate, inadequate or unclear for participants;
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adequate, inadequate or unclear for personnel;
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adequate, inadequate or unclear for outcome assessors.
(4) Incomplete outcome data (checking for possible attrition bias through withdrawals, dropouts, protocol deviations)
We will describe for each included study, and for each outcome or class of outcomes, the completeness of data including attrition and exclusions from the analysis. We will state whether attrition and exclusions were reported, the numbers included in the analysis at each stage (compared with the total randomised participants), reasons for attrition or exclusion where reported, and whether missing data were balanced across groups or were related to outcomes. Where sufficient information is reported, or can be supplied by the trial authors, we will re‐include missing data in the analyses which we undertake. We will assess methods as:
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adequate;
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inadequate;
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unclear.
(5) Selective reporting bias
We will describe for each included study how we investigated the possibility of selective outcome reporting bias and what we found.
We will assess the methods as:
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adequate (where it is clear that all of the study’s pre‐specified outcomes and all expected outcomes of interest to the review have been reported);
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inadequate (where not all the study’s pre‐specified outcomes have been reported; one or more reported primary outcomes were not pre‐specified; outcomes of interest are reported incompletely and so cannot be used; study fails to include results of a key outcome that would have been expected to have been reported);
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unclear.
(6) Other sources of bias
We will describe for each included study any important concerns we have about other possible sources of bias.
We will assess whether each study was free of other problems that could put it at risk of bias:
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yes;
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no;
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unclear.
(7) Overall risk of bias
We will make explicit judgements about whether studies are at high risk of bias, according to the criteria given in the Handbook (Higgins 2009). With reference to (1) to (6) above, we will assess the likely magnitude and direction of the bias and whether we consider it is likely to impact on the findings. We will explore the impact of the level of bias through undertaking sensitivity analyses ‐ seeSensitivity analysis.
Measures of treatment effect
Dichotomous data
For dichotomous data, we will present results as summary risk ratio with 95% confidence intervals.
Continuous data
For continuous data, we will use the mean difference if outcomes are measured in the same way between trials. We will use the standardised mean difference to combine trials that measure the same outcome, but use different methods.
Dealing with missing data
For included studies, we will note levels of attrition. We will explore the impact of including studies with high levels of missing data in the overall assessment of treatment effect by using sensitivity analysis.
For all outcomes, we will carry out analyses, as far as possible, on an intention‐to‐treat basis; i.e. we will attempt to include all participants randomised to each group in the analyses, and will analyse all participants in the group to which they were allocated, regardless of whether or not they received the allocated intervention. The denominator for each outcome in each trial will be the number randomised minus any participants whose outcomes are known to be missing.
Assessment of heterogeneity
We will assess statistical heterogeneity in each meta‐analysis using the T², I² and Chi² statistics. We will regard heterogeneity as substantial if T² is greater than zero and either I² is greater than 30% or there is a low P value (less than 0.10) in the Chi² test for heterogeneity.
Assessment of reporting biases
If there are 10 or more studies in the meta‐analysis we will investigate reporting biases (such as publication bias) using funnel plots. We will assess funnel plot asymmetry visually, and use formal tests for funnel plot asymmetry. For continuous outcomes we will use the test proposed by Egger 1997, and for dichotomous outcomes we will use the test proposed by Harbord 2006. If asymmetry is detected in any of these tests or is suggested by a visual assessment, we will perform exploratory analyses to investigate it.
Data synthesis
We will carry out statistical analysis using the Review Manager software (RevMan 2008). We will use fixed‐effect meta‐analysis for combining data where it is reasonable to assume that studies are estimating the same underlying treatment effect: i.e. where trials are examining the same intervention, and the trials’ populations and methods are judged sufficiently similar. If there is clinical heterogeneity sufficient to expect that the underlying treatment effects differ between trials, or if we detect substantial statistical heterogeneity, we will use random‐effects meta‐analysis to produce an overall summary if an average treatment effect across trials is considered clinically meaningful. We will treat the random‐effects summary as the average range of possible treatment effects and we will discuss the clinical implications of treatment effects differing between trials. If the average treatment effect is not clinically meaningful we will not combine trials.
If we use random‐effects analyses, we will present the results as the average treatment effect with its 95% confidence interval, and the estimates of T² and I².
Subgroup analysis and investigation of heterogeneity
If we identify substantial heterogeneity, we will investigate it using subgroup analyses and sensitivity analyses. We will consider whether an overall summary is meaningful, and if it is, use random‐effects analysis to produce it.
We plan to carry out the following subgroup analyses.
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Types of analgesia: continuation of the existing analgesia through labour versus newly administered analgesia.
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Mode of analgesia: regional anaesthesia versus local analgesia
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Types of medications: systemic opioids versus nitrous oxide.
We will use the primary outcomes in subgroup analysis.
For fixed‐effect inverse variance meta‐analyses we will assess differences between subgroups by interaction tests. For random‐effects and fixed‐effect meta‐analyses using methods other than inverse variance, we will assess differences between subgroups by inspection of the subgroups’ confidence intervals; non‐overlapping confidence intervals indicate a statistically significant difference in treatment effect between the subgroups.
Sensitivity analysis
We will carry out sensitivity analysis on the primary outcomes to explore the effect of adequacy of allocation on concealment (including quasi‐randomisation) and other risk of bias components.
