[Strabismus surgery in children. The effect of paracetamol and bupivacaine]

Postoperative vomiting is induced by different mechanisms such as age, anaesthetic technique and medications, postoperative analgesia, and surgical traction on the extra-ocular muscles. The influence of anticholinergic premedication and the use of benzodiazepines as factors affecting the incidence of vomiting is controversial. In a prospective, randomised, single-blind study we examined two different treatments with regard to postoperative pain, vigilance, and vomiting in young children undergoing strabismus repair. METHODS. After institutional ethical committee approval, informed written consent was obtained from all parents. The children were randomly assigned to three groups: (1) paracetamol (P)--17 patients who received 250-500 mg paracetamol rectally (dependent on body weight) immediately after intubation of the trachea; (2) bupivacaine (B)--17 patients who received two drops 0.5% bupivacaine hydrochloride on the conjunctiva of the eye(s) being corrected following intubation of the trachea and again 10 min after intubation. After the surgeon had exposed the extra-ocular muscle and before readaptation of the conjunctiva, two drops of the same solution were applied again each time directly on the muscle; and (3) controls (C)--16 patients who received rectal paracetamol after completion of the operation but before extubation. The children were premedicated with 0.05 mg/kg flunitrazepam sublingually. After 0.25 mg atropine i.v., anaesthesia was induced with 0.1 mg/kg vecuronium, 5 mg/kg thiopentone, 1.5 vol% enflurane, and N2O/O2 50:50. When the trachea was intubated anaesthesia was maintained with enflurane as required and 70% N2O in oxygen. Extubation was performed only if the patient could touch or did not tolerate the tube. Oral diet was allowed 6 h after extubation at the earliest. EXAMINATION OF VIGILANCE AND ANALGESIA. The degrees of vigilance and pain were evaluated preoperatively and after extubation over 24 h using two different scales. Evaluation of the scales was performed during the first 3 postoperative h at 12 different time points (Figs. 1, 2) and 6, 12, and 24 h after extubation. The evaluation was conducted by nursing staff who were blinded to the treatment (single-blind study). Postoperative analgesia consisted of 250-500 mg rectal paracetamol (all patients). Parametric data were expressed as mean +/- SD, and comparisons were made with the one-way analysis of variance. Fisher's exact test was applied to ordinal data. P < 0.05 indicates a statistically significant difference. RESULTS. Two patients (P) were excluded from the study postoperatively because of refusing rectal paracetamol in spite of pain and postoperative infection of the upper airways, which had manifested on the afternoon of the operative day. No significant differences were found between the three groups in patient characteristics (Table 1). The quantity of enflurane administered, rate, postoperative consumption of rectal paracetamol, and postoperative emesis were highest in the control group (Tables 2, 3), but the incidence of postoperative vomiting ranged only between 13% and 24% (Table 3). Children with preoperative paracetamol needed more time to fulfill the criteria to "stick out the tongue" and "recognising the mother". VIGILANCE. The time to postoperative crying or screaming and restlessness was shorter in the control group. The values reached significant difference at 10 min (P) and 25 min (P and B) after extubation compared with the other groups (Fig. 1). ANALGESIE. At 5, 10, and 150 min after extubation pain was significantly higher in patients in the control group (Fig. 2). CONCLUSIONS. Intraoperative administration of rectal paracetamol or topical 0.5% bupivacaine was most effective in the treatment of postoperative pain for strabismus surgery in younger children. Sublingual flunitrazepam and i.v. atropine given as premedication probably decrease postoperative vomiting.