A new route, jet-injection for anesthetic induction in children - II. ketamine dose-range finding studies.

Ketamine (K) i.m. has been widely used for anesthetic induction in small children in the last decades, if mask induction has failed. In many instances, however, physical restraint was required. In order to eliminate the pain of i.m. injection and to prevent the psychological and physical trauma associated with restraint, we evaluated the utility of jet-injection (j.i.) of K for anesthetic induction in a dose-range finding study. Thirty children (age 1-6 years), whose parents gave a valid consent approved by the IRB and were scheduled for minor surgeries, were randomized into 3 equal groups: A/ketamine 6.0 mg/kg j.i., B/ketamine 3.5 mg/kg j.i., C/ketamine 2.5 mg/kg j.i. As a drying agent atropine 20 microg/kg was also given i.v. The onset of full amnesic/sedative effect of K, the scoring of sedation and emotional state, the ease of placement of the i.v. catheter, the speed of recovery by Aldrete scores, and the time for safe discharge were evaluated. Although no demographic differences were observed among the groups the duration of surgery and anesthesia were longer in the B group (41 and 49 min) than in the A or C groups. The onset of sedation was significantly (p < 0.05) faster in group A (174 sec) than in group B (312 sec) or C (303 sec). However, no significant difference was observed in the onset of complete sedation among the groups. The sedation index was the lowest representing the best sedation in group A (4.2) while in group B and C were somewhat higher (4.6 and 4.4). There were no differences in the ease of i.v. cannulation among the groups. Recovery from anesthesia was the slowest in group A, although the differences among the 3 groups did not reach statistical significance. The mean discharge times ranged from 10-13 min with no differences among the groups. Laryngospasm occurred in 4:10 in group A and 1:10 in groups B and C. Evidently the high dose of K, 6.0 mg/kg caused a proneness to laryngospasm. Since no additional benefit was derived from this high dose, the lower doses (3.0 mg/kg) of K may be sufficient for routine use. None of the children experienced unpleasant recall or pain for the injection or the whole procedure. This new route of anesthetic induction with the jet-injector utilizing K may provide pain-free and stress-free induction as compared to its i.m. injection. This technique also prevents transmission of infection and is [correction of and cost] cost effective since simultaneous and/or sequential injection can be given from a single vial of K.