Dose response study of caudal neostigmine for postoperative analgesia in paediatric patients undergoing genitourinary surgery.

BACKGROUND

Neostigmine given through the neuraxial route has been found to have analgesic properties. In this clinical trial, we evaluated for the first time the efficacy of a varying dose of caudal neostigmine for postoperative analgesia in children undergoing genitourinary surgery.

METHODS

In this double blind prospective study, we studied 120 children ASA physical status I in age group of 2-8 years scheduled for surgical repair of hypospadias under general anaesthesia. Children were randomly allocated to one of the six groups (n = 20 each) and received either no caudal block (group C) or neostigmine (groups I-V) in doses of 10, 20, 30, 40 and 50 microgram.kg-1 respectively at the end of the surgery. Postoperatively pain was assessed using an objective pain score for 24 h. Blood pressure, heart rate, SpO2, total amount of analgesic consumed and adverse effects, if any, were also recorded.

RESULTS

The duration of postoperative analgesia did not differ significantly between group C and I (P > 0.05). There was significant prolongation in the duration of analgesia in rest of the groups (group II-3.52 +/- 1.37 h; group III-6.50 +/- 1.93 h; group IV-10.45 +/- 3.41 h; group V-13.70 +/- 5.52 h) (P < 0.05). A dose dependent increase in the incidence of nausea and vomiting was also observed with highest incidence in group IV and V (group C-15%; group I-20%; group II and III-30%; group IV-45% and group V-60%) (P < 0.05). No significant alteration in vital signs and other adverse effects were noticed.

CONCLUSIONS

Caudal neostigmine in the dose range of 20-50 microgram.kg-1 provides dose dependent analgesia. However, dose exceeding 30 microgram.kg-1 is associated with a higher incidence of nausea and vomiting.