Childbirth by caesarean section is becoming more frequent. Caesarean section requires an anaesthetic, either spinal, spinal epidural, epidural block or general anaesthesia. Postoperative pain is managed with a combination of an opioid such as morphine or pethidine and other analgesics. Opioids cause sedation and they can transfer to breast milk, also sedating the newborn infant. Childbirth is a deeply emotional experience and involves bonding with the newborn and starting breastfeeding. Improvements in pain relief that make the postanaesthesia period less uncomfortable are important. During the operation, local anaesthetic can be injected to block the nerves before cutting the skin or after closing the skin at the end of the operation (abdominal nerve block) or the wound can be irrigated or infiltrated with local anaesthetic solution to reduce postoperative pain (pre-emptive wound analgesia).
The authors identified twenty randomised controlled trials of sufficient quality involving 1150 women. These trials were carried out in both developed and developing countries. In general, local anaesthesia wound infiltration was of benefit in women having a caesarean section requiring regional anaesthetics because of a reduction in the use of opioid analgesia. Women undergoing general anaesthesia who had wound infiltration with local anaesthetics and peritoneal spraying required lower amounts of opioids in the first 24 hours post-operation compared to saline control. Those who had a general anaesthetic and the abdominal wall nerves blocked had reduced pain scores within the first 24 hours postoperative.
Women who had regional anaesthesia and abdominal nerves blocked also benefited by decrease in opioid requirements. Non-steroidal anti-inflammatory drugs provided additional pain relief but with more side effects of pruritus. The commonly used local anaesthetic agents do have side effects but these are very rare, ranging from allergy to cardiovascular and central nervous system effects. There was no report of side effects in infants following local anaesthetic infiltration but the number of women studied was small. The longer theatre time and cost of the local anaesthetic may be offset by less use of postoperative analgesia. The effect on the development of chronic pelvic pain should be an important area of research.