Prophylactic intravenous preloading for regional analgesia in labour

The effect of giving intravenous fluid to prevent low blood pressure, following regional analgesia for women in labour, is unclear.

Regional (epidural, spinal or combined spinal-epidural) analgesia is a common form of pain relief used during labour. Some women have hypotension (low blood pressure) following regional analgesia which can affect both mother and baby. Intravenous fluids before epidural analgesia with high-dose local anaesthetics reduces hypotension. This benefit is not seen when the more recent low-dose local anaesthetics are used, probably due to a lower risk of hypotension with these drugs. There was not enough evidence to show whether preloading is beneficial for women having regional analgesia during labour using the lower-dose agents, or for women with pregnancy complications.

Authors' conclusions: 

Preloading prior to traditional high-dose local anaesthetic blocks may have some beneficial fetal and maternal effects in healthy women. Low-dose epidural and CSE analgesia techniques may reduce the need for preloading. The studies reviewed were too small to show whether preloading is beneficial for women having regional analgesia during labour using the lower-dose local anaesthetics or opioids. Further investigation of low-dose epidural or CSE (including opioid only) blocks, and the risks and benefits of intravenous preloading for women with pregnancy complications, is required.

[Note: The five citations in the awaiting classification section of the review may alter the conclusions of the review once assessed.]

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Background: 

Reduced uterine blood flow from maternal hypotension may contribute to fetal heart rate changes which are common following regional analgesia (epidural or spinal or combined spinal-epidural (CSE)) during labour. Intravenous fluid preloading may help to reduce maternal hypotension but using lower doses of local anaesthetic, and opioid only blocks, may reduce the need for preloading.

Objectives: 

To assess the effects of prophylactic intravenous fluid preloading before regional analgesia during labour on maternal and fetal well-being.

Search strategy: 

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (19 February 2004). We updated this search on 30 June 2010 and added the results to the awaiting classification section of the review.

Selection criteria: 

Randomised and quasi-randomised trials comparing prophylactic intravenous preloading before regional analgesia during labour with a control group (dummy or no preloading).

Data collection and analysis: 

Two reviewers independently applied eligibility criteria, assessed trial quality and extracted data.

Main results: 

Six studies are included (473 participants). In one epidural trial using high-dose local anaesthetic, preloading with intravenous fluids was shown to counteract the hypotension which frequently follows traditional epidural analgesia (relative risk (RR) 0.07, 95% confidence interval (CI) 0.01 to 0.53; 102 women). This trial was also associated with a reduction in fetal heart rate abnormalities (RR 0.36, 95% CI 0.16 to 0.83; 102 women); no differences were detected in other perinatal and maternal outcomes for this trial and another high-dose epidural trial. In the two epidural low-dose anaesthetic trials, no significant difference in maternal hypotension was found (RR 0.73, 95% CI 0.36 to 1.48; 260 women), although they were underpowered to detect less than a very large effect. No significant differences were seen between groups in these trials for fetal heart rate abnormalities (RR 0.64, 95% CI 0.39 to 1.05; 233 women).

In the two CSE trials, no differences were reported between preloading and no preloading groups. In the spinal/opioid trial, the RR for hypotension was 0.89, 95% CI 0.43 to 1.83 (40 women) and 0.70, 95% CI 0.36 to 1.37 for fetal heart rate abnormalities (32 women). In the opioid only study (30 women), there were no instances of hypotension or fetal heart rate abnormalities in either group.

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