Efficacy of Intravenously Injected Epidural Test Dose in Adult Patients Anesthetized with Enflurane or Isoflurane

Lee, Sang Chul; Kim, Kye Min; Kim, Kyoung Ok; Kim, Sang Tae

Abstract

BACKGROUND: Efficacy of epidural test dose for detecting inadvertent intravascular injection during general anesthesia with volatile anesthetics, has not been clearly determined. The object of this study is to see the efficacy of simulated intravenous test dose in adult patients anesthetized with O2-N2O- enflurane or isoflurane.
METHODS
Sixty eight adults were evenly divided into enflurane group and isoflurane group. In enflurane group(n=34), patients were alternatively assigned to group I(n=17) and group II(n=17). After induction of general anesthesia, anesthesia was maintained with O2-N2O(50%)-enflurane(end-tidal concentration 1 vol%). After vital signs were stabilized, normal saline 3 ml was injected intravenously to group I, while 2% lidocaine 3 ml containing 15 mcg epinephrine to group II. Heart rate(HR) and systolic blood pressure(SBP) were measured at 10-seconds intervals for 4 minutes. Study procedure for isoflurane group(group III-normal saline injection vs group IV-test dose injection) was identical to enflurane group except using isoflurane(end-tidal concentration 1 vol%).
RESULTS
1. Enflurane 1 vol% group: When maximum HR increase > or =20 beats/min is regarded as positive test, sensitivity is 71% and specificity is 100%. While SBP increase > or =15 mmHg is regarded as positive test, sensitivity is 94% and specificity is 100%. 2. Isoflurane 1 vol% group: Based on the same criteria, sensitivity is 18% and specificity is 100% for HR, and sensitivity is 94% and specificity is 100% for SBP.
CONCLUSIONS
When epidural analgesia is combined with O2-N2O-enflurane /isoflurane anesthesia, it's better to observe changes in SBP than HR after epidural test dose injection.