Abstract: We found only three RCTs, in which a total of 230 postpartum women participated. Most of our analyses were based on relatively small numbers of patients and studies. Overall, the certainty of evidence regarding the effectiveness of interventions was low, due to risk of bias and imprecision. We found very low-certainty evidence regarding the safety of interventions because of risk of bias and imprecision. Two studies had unclear risk of selection bias. One study had unclear risk of reporting bias and a high risk of other bias associated with the study protocol. Women who received an intraperitoneal instillation of lidocaine experienced lower intensity intraperitoneal pain than those given a placebo (pooled MD -3.34, 95% CI -4.19 to -2.49, three studies, 190 participants, low-certainty evidence), or an intramuscular injection of morphine (MD -4.8, 95% CI -6.43 to -3.17, one study, 40 participants, low-certainty evidence). We found no clear difference in intraperitoneal pain between women who had an intramuscular injection of morphine added to an intraperitoneal instillation of lidocaine and those who had an intraperitoneal instillation of lidocaine alone (MD -0.40, 95% CI -1.52 to 0.72, one study, 40 participants, low-certainty evidence). An intramuscular injection of morphine alone was not effective for intraperitoneal pain relief compared to placebo (MD 0.50, 95% CI -1.33 to 2.33, one study, 40 women, low-certainty evidence). None of the studies reported any serious adverse events but the evidence was very low-certainty. Intraperitoneal instillation of lidocaine may reduce the number of women requiring additional pain control when compared to placebo (RR 0.27, 95% CI 0.17 to 0.44, three studies, 190 women, low-certainty evidence). An intraperitoneal instillation of lidocaine during postpartum mini-laparotomy tubal ligation before fallopian tubes were tied may offer better intraperitoneal pain control, although the evidence regarding adverse effects is uncertain. We found no clear difference in intraperitoneal pain between women who received a combination of an injection of morphine, and intraperitoneal instillation of lidocaine and those who received an intraperitoneal instillation of lidocaine alone. These results must be interpreted with caution, since the evidence overall was low to very low-certainty.

Plain-language summary: We included three randomised controlled trials involving a total of 230 women. These studies compared lidocaine poured into the abdominal cavity with a placebo, or other treatments, such as an injection of morphine (also known as an opioid) into the muscle, or combination of lidocaine and morphine. All studies took place in Thailand. The evidence described here are from studies published before 31 July, 2017. Pouring lidocaine into the abdominal cavity during a mini-laparotomy tubal ligation before fallopian tubes were tied after delivery may offer better pain control than a placebo or morphine injection, although the evidence regarding adverse effects is uncertain. Women who received a combination of morphine injection and lidocaine poured into the abdominal cavity showed no clear difference in pain with those who received lidocaine alone. An injection of morphine into the muscle alone did not reduce pain more than a placebo. The certainty of evidence regarding the effectiveness of these interventions was low due to risk of bias and imprecision of results. The certainty of evidence regarding the safety of the interventions was very low because of risk of bias and imprecision.