INTRAVENOUS ISOPROTERENOL AS A MARKER FOR EPIDURAL TEST-DOSING IN CHILDREN

The purpose of this study was to determine if isoproterenol would be a n effective marker of intravascular injection in anesthetized children . Forty-four ASA 1 children, aged 2 mo to 10 yr, were randomly assigne d to two groups. Children in group 1 (n = 21) received 0.05 mug/kg iso proterenol, and children in group 2 (n = 23) received 0.075 mug/kg iso proterenol. A blinded observer continuously recorded heart rate and ar terial blood pressure. Measurements were recorded before the surgical incision at steady-state halothane concentration of 1.2 minimum alveol ar concentration adjusted for age. Isoproterenol produced a graded inc rease in heart rate with mean maximum increases of 16.5 +/- 8.7 beats/ min in group 1 and 21.5 +/- 9.2 beats/min in group 2. No episodes of h ypotension and arrhythmia were noted. Isoproterenol, 0.075 mug/kg, is more sensitive but still is an imperfect marker of an intravascular in jection. It produces a heart rate increase in 96% of children anesthet ized with halothane and nitrous oxide in 50% oxygen. The application o f isoproterenol as an epidural test dose appears promising, but cannot be recommended until its full reliability and neurotoxicity are evalu ated.