What is the issue?
Regional nerve block is one type of anaesthetic women can receive when having a caesarean section. Two different methods are used. Single-shot spinal involves a single injection of anaesthetic into the lower spine. Combined spinal and epidural block involves using a larger needle and the insertion of a small catheter into the lower spine. This review examines the relative benefits and risks of these two regional block methods for women undergoing caesarean and for their babies.
Why is this important?
Single-shot spinal anaesthesia for caesarean section is relatively easily performed and works quickly. As it involves a single injection, block duration cannot be extended without the woman having another spinal injection. The rapid onset of the block can cause adverse effects, such as low blood pressure (hypotension) and nausea and vomiting. Lower doses of local anaesthetic may reduce these adverse events, and speed up the return of muscle function. In this review, we look at high- and low-dose spinals separately.
With combined spinal-epidural anaesthesia (CSE) the insertion of the epidural catheter allows the injection of small doses into the spine and additional doses of anaesthetic to be administered through the epidural catheter. CSE anaesthetic typically works more slowly and may avoid some of the adverse effects seen in single-shot spinal anaesthetics. Being able to top up anaesthesia can reduce the need for general anaesthetic or sedation when the regional nerve block is not sufficient for surgery. The epidural catheter may also be used to give pain medication after the operation.
What evidence did we find?
We searched for evidence (8 August 2019) and identified 18 randomised controlled trials (1272 women) comparing high- or low-dose single-shot spinal anaesthesia with the CSE method. However, most of our analyses involved fewer studies and relatively small numbers of women. Two trials did not contribute data to our review.
There may be little or no difference between CSE and high-dose spinal in the number of women requiring repeat anaesthesia or general anaesthetic due to failure to establish adequate initial anaesthesia. We are uncertain whether CSE or spinal makes any difference in the need for additional intra-operative analgesia or conversion to general anaesthesia. We are also uncertain about the results for the number of women who were satisfied with anaesthesia, regardless of the type of nerve block. More women in the CSE group (13/21) experienced intra-operative nausea or vomiting requiring treatment than in the high-dose spinal group (6/21). Similar numbers of women between groups experienced post-dural puncture headache (5/56 with CSE versus 6/57 with SSS; 3 studies, 113 women), or intra-operative hypotension requiring treatment (4 trials, 162 women).
There may be little or no difference between CSE and low-dose spinal groups in the number of women requiring repeat anaesthesia or general anaesthetic because of failure to establish adequate initial anaesthesia (3 studies, 224 women). There is probably little or no difference in the need for additional intra-operative analgesia (4 studies, 298 women). We are uncertain of the effect of CSE or low-dose spinal on the need for intra-operative conversion to general anaesthesia, because none of the women required this (3 studies, 222 women). No studies examined women's satisfaction with anaesthesia. The average time to effective anaesthesia was faster with low-dose spinal compared to CSE, although the small difference is unlikely to be clinically meaningful (2 studies, 160 women). CSE appeared to reduce intra-operative hypotension requiring treatment compared with low-dose spinal (4 studies, 336 women). Similar numbers of women between the CSE and low-dose spinal groups experienced intra-operative nausea or vomiting requiring treatment (3/50 with CSE versus 6/50 with SSS; 1 trial, 100 women). There were no post-dural puncture headaches (1 study, 138 women).
All babies were healthy at birth, irrespective of the maternal anaesthesia used (measured by Apgar scores; 5 studies, 242 babies).
What does this mean?
There is currently insufficient evidence to favour one anaesthetic technique over the other. The number of studies and participants for most of our analyses were small, and some studies had design limitations. More studies are needed in order to further evaluate the relative effectiveness and safety of CSE and spinal anaesthesia for caesarean section.
In this review, the number of studies and participants for most of our analyses were small and some of the included trials had design limitations. There was some suggestion that, compared to spinal anaesthesia, CSE could be associated with a reduction in the number of women with intra-operative hypotension, but an increase in intra-operative nausea and vomiting requiring treatment. One small study found that low-dose spinal resulted in a faster time to effective anaesthesia compared to CSE. However, these results are based on limited data and the difference is unlikely to be clinically meaningful. Consequently, there is currently insufficient evidence in support of one technique over the other and more evidence is needed in order to further evaluate the relative effectiveness and safety of CSE and spinal anaesthesia for caesarean section.
More high-quality, sufficiently-powered studies in this area are needed. Such studies could consider using the outcomes listed in this review and should also consider reporting economic aspects of the different methods under investigation.
Single-shot spinal anaesthesia (SSS) and combined spinal-epidural (CSE) anaesthesia are both commonly used for caesarean section anaesthesia. Spinals offer technical simplicity and rapid onset of nerve blockade which can be associated with hypotension. CSE anaesthesia allows for more gradual onset and also prolongation of the anaesthesia through use of a catheter.
To compare the effectiveness and adverse effects of CSE anaesthesia to single-shot spinal anaesthesia for caesarean section.
We searched the Cochrane Pregnancy and Childbirth’s Trials Register, ClinicalTrials.gov, the WHO International Clinical Trials Registry Platform (ICTRP), and reference lists of retrieved studies (search date: 8 August 2019).
We considered all published randomised controlled trials (RCTs) involving a comparison of CSE anaesthesia with single-shot spinal anaesthesia for caesarean section. We further subgrouped spinal anaesthesia as either high-dose (10 or more mg bupivacaine), or low-dose (less than 10 mg bupivacaine).
Two review authors independently assessed trials for inclusion and risks of bias, extracted data and checked them for accuracy. We used standard methodological procedures expected by Cochrane.
We identified 18 trials including 1272 women, but almost all comparisons for individual outcomes involved relatively small numbers of women. Two trials did not report on this review's outcomes and therefore contribute no data towards this review. Trials were conducted in national or university hospitals in Australia (1), Croatia (1), India (1), Italy (1), Singapore (3), South Korea (4), Spain (1), Sweden (1), Turkey (2), UK (1), USA (2). The trials were at a moderate risk of bias overall.
CSE versus high-dose spinal anaesthesia
There may be little or no difference between the CSE and high-dose spinal groups for the number of women requiring a repeat regional block or general anaesthetic as a result of failure to establish adequate initial blockade (risk ratio (RR) 0.32, 95% confidence interval (CI) 0.05 to 1.97; 7 studies, 341 women; low-quality evidence). We are uncertain whether having CSE or spinal makes any difference in the number of women requiring supplemental intra-operative analgesia at any time after CSE or spinal anaesthetic insertion (average RR 1.25, 95% CI 0.19 to 8.43; 7 studies, 390 women; very low-quality evidence), or the number of women requiring intra-operative conversion to general anaesthesia (RR 1.00, 95% CI 0.07 to 14.95; 7 studies, 388 women; very low-quality evidence). We are also uncertain about the results for the number of women who were satisfied with anaesthesia, regardless of whether they received CSE or high-dose spinal (RR 0.93 95% CI 0.73 to 1.19; 2 studies, 72 women; very low-quality evidence). More women in the CSE group (13/21) experienced intra-operative nausea or vomiting requiring treatment than in the high-dose spinal group (6/21). There were 11 cases of post-dural puncture headache (5/56 with CSE versus 6/57 with SSS; 3 trials, 113 women) with no clear difference between groups. There was also no clear difference in intra-operative hypotension requiring treatment (46/86 with CSE versus 41/76 with SSS; 4 trials, 162 women). There were no babies with Apgar score less than seven at five minutes (4 trials, 182 babies).
CSE versus low-dose spinal anaesthesia
There may be little or no difference between the CSE and low-dose spinal groups for the number of women requiring a repeat regional block or general anaesthetic as a result of failure to establish adequate initial blockade (RR 4.81, 95% CI 0.24 to 97.90; 3 studies, 224 women; low-quality evidence). Similarly, there is probably little difference in the number of women requiring supplemental intra-operative analgesia at any time after CSE or low-dose spinal anaesthetic insertion (RR 1.75, 95% CI 0.78 to 3.92; 4 studies, 298 women; moderate-quality evidence). We are uncertain about the effect of CSE or low-dose spinal on the need for intra-operative conversion to general anaesthesia, because this was not required by any of the 222 women in the three trials (low-quality evidence). None of the studies examined whether women were satisfied with their anaesthesia.
The mean time to effective anaesthesia was faster in women who received low-dose spinal compared to CSE, although it is unlikely that the magnitude of this difference is clinically meaningful (standardised mean difference (SMD) 0.85 minutes, 95% CI 0.52 to 1.18 minutes; 2 studies, 160 women).
CSE appeared to reduce the incidence of intra-operative hypotension requiring treatment compared with low-dose spinal (average RR 0.59, 95% CI 0.38 to 0.93; 4 studies, 336 women). Similar numbers of women between the CSE and low-dose spinal groups experienced intra-operative nausea or vomiting requiring treatment (3/50 with CSE versus 6/50 with SSS; 1 study, 100 women), and there were no cases of post-dural puncture headache (1 study, 138 women). No infants in either group had an Apgar score of less than seven at five minutes (1 study; 60 babies).