Effect of dexamethasone on prevention of postoperative nausea, vomiting and pain after caesarean section: a randomised, placebo-controlled, double-blind trial.

CONTEXT: Spinal morphine is a common form of postoperative analgesia after caesarean section, but it is associated with postoperative nausea and vomiting.

OBJECTIVE: To evaluate the hypothesis that dexamethasone reduces nausea and vomiting in patients undergoing caesarean section under spinal anaesthesia with morphine.

DESIGN: Interventional, randomised, double-blinded, placebo-controlled study to evaluate a preoperative single dose of dexamethasone.

SETTING: Patients from a tertiary hospital in the city of Sao Paulo, Sao Paulo, Brazil observed from 1 January through 30 June 2008.

PATIENTS OR OTHER PARTICIPANTS: Seventy full-term pregnant patients (American Society of Anesthesiologists 1 or 2) were studied. Patients were randomly allocated into two groups determined by a computerised table. Exclusion criteria were contraindication to regional anaesthesia, allergy to dexamethasone, opioids or local anaesthetics, hypertension or diabetes originated during pregnancy and use of any antiemetic drug received before surgery. Spinal anaesthesia consisted of hyperbaric bupivacaine and morphine.

INTERVENTION: Patients received either dexamethasone 10 mg in 100 ml of isotonic saline, intravenously or 100 ml of isotonic saline (placebo) prior to surgery.

MAIN OUTCOME: Incidence of postoperative nausea and vomiting in the first 24 h were rated and recorded. Pain scores at rest and on movement were evaluated using a visual analogue scale.

RESULTS: During the first 24 hours, nausea occurred in 12/35 (34.4%) patients receiving dexamethasone and in 32/35 (91.4%) receiving placebo (P<0.001). During the same time period, vomiting occurred in 12/35 (34.4%) patients receiving dexamethasone and in 29/35 (82.9%) receiving placebo (P<0.001). Pain at rest and pain on movement was lower in patients who received dexamethasone at some time points during the study period.

CONCLUSION: Dexamethasone reduced the cumulative incidence of nausea and vomiting after caesarean section under spinal anaesthesia with morphine and lowered pain scores on the first postoperative day.