Main outcome measures
The primary outcome was the total amount of opioid use, measured on the
PCA device, in the first 48 hours after caesarean delivery. Our
secondary outcomes were intensity of pain, the incidence of adverse
effects (post-operative nausea/vomiting and pruritus) and time of first
ambulation. Pain was evaluated by visual analog scale (VAS) (0-10) at
rest and at mobilisation (defined as pain during coughing) 2 hours, 6
hours and 12 hours after surgery (except if the patient was asleep) and
thereafter once daily until discharge. The VAS tool consisted of a 10-cm
horizontal line with at one end no pain and at the other end worst pain
ever. Patients were asked to mark the point on the scale that
corresponded to their pain. Post-operative nausea/vomiting and pruritus
were evaluated using a categorical scale ranging from 0 to 2 (0: none,
1: mild (requiring no treatment) and 2: severe (requiring treatment)) at
the same interval pain was assessed. Rescue medications for
post-operative nausea/vomiting and pruritus were taken into account. All
data were collected by independent investigators: nurses, midwifes,
anaesthetists and gynaecologists that were not aware of group
allocation.