ABSTRACT
BACKGROUND: The efficacy of an 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 evaluate the efficacy of a simulated intravenous isoproterenol test dose in adult patients anesthetized with O2-N2O-enflurane. METHODS: Forty-five healthy adult patients were anesthetized with 1 vol% enflurane and nitrous oxide after endotracheal intubation and were randomized to one of three groups according to the dose of isoproterenol. Isoproterenol 1, 2 and 3 microgram groups (n = 15 each) received 3 ml of 2% lidocaine with 1, 2 and 3 microgram isoproterenol IV respectively, to simulate an intravascularly administered test dose. HR and systolic blood pressure were measured at 20-s intervals for 4 min after injection. RESULTS: Mean maximal heart rate increases were 15 8, 21 8, and 27 10 bpm (mean SD) in the isoproterenol 1, 2 and 3 microgram groups, respectively. Isoproterenol 3 microgram produced 100% sensitivity in the modified (> or = 10 bpm increase) HR criteria and 67% sensitivity in the conventional (> or = 20 bpm increase) HR criteria. CONCLUSIONS: To determine whether an epidural catheter may be in a blood vessel, various vasoactive drugs are often administered. The epidural test dose containing 3 microgram isoproterenol might be a reliable marker for intravascular injection based on the modified HR criterion.
Subject(s)
Adult , Humans , Anesthesia, General , Anesthetics , Blood Pressure , Blood Vessels , Catheters , Enflurane , Heart Rate , Intubation, Intratracheal , Isoproterenol , Lidocaine , Nitrous OxideABSTRACT
BACKGROUND: The efficacy of an 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 evaluate the efficacy of a simulated intravenous isoproterenol test dose in adult patients anesthetized with O2-N2O-enflurane. METHODS: Forty-five healthy adult patients were anesthetized with 1 vol% enflurane and nitrous oxide after endotracheal intubation and were randomized to one of three groups according to the dose of isoproterenol. Isoproterenol 1, 2 and 3 microgram groups (n = 15 each) received 3 ml of 2% lidocaine with 1, 2 and 3 microgram isoproterenol IV respectively, to simulate an intravascularly administered test dose. HR and systolic blood pressure were measured at 20-s intervals for 4 min after injection. RESULTS: Mean maximal heart rate increases were 15 8, 21 8, and 27 10 bpm (mean SD) in the isoproterenol 1, 2 and 3 microgram groups, respectively. Isoproterenol 3 microgram produced 100% sensitivity in the modified (> or = 10 bpm increase) HR criteria and 67% sensitivity in the conventional (> or = 20 bpm increase) HR criteria. CONCLUSIONS: To determine whether an epidural catheter may be in a blood vessel, various vasoactive drugs are often administered. The epidural test dose containing 3 microgram isoproterenol might be a reliable marker for intravascular injection based on the modified HR criterion.