The efficacy of hemodynamic and T wave criteria for detecting intravascular injection of epinephrine test doses in anesthetized adults: A dose-response study

Recent studies have shown that an epidural test dose containing 15 mug of e pinephrine has a sensitivity and specificity of 100% for detecting intravas cular injection based on the systolic blood pressure (SBP) (positive if gre ater than or equal to 15-mm Hg increase) and the T wave criteria (positive if greater than or equal to0.1 mV and 25% decrease in amplitude), whereas t he modified heart rate (HR) criterion (positive if greater than or equal to 10-bpm increase) produced uncertain results in sevoflurane-anesthetized ad ults. Because a fractional dose of the test dose may be injected intravascu larly in actual clinical situations, we designed this study to determine, i n a dose-related manner, the efficacy and minimum effective dose of epineph rine based on those hemodynamic and the T wave criteria. Eighty healthy adu lt patients were randomly assigned to one of four groups according to a sim ulated IV test dose under 2% end-tidal sevoflurane and nitrous oxide anesth esia after endotracheal intubation (n = 20 each). The saline group received 3 mL of normal saline IV; the epinephrine-15 group received 3 mt of 1.5% l idocaine containing 15 mug of epinephrine (1:200,000); and the epinephrine- 10 and -5 groups received 2 and 1 mt of the test dose of the identical comp onents, respectively. HR, SBP, and lead II of the electrocardiograph were r ecorded continuously far 5 min after the IV injection of the study drug. Se nsitivities and specificities of 100% were obtained based on the HR and the SBP criteria only if 15 mug of epinephrine was injected IV, whereas sensit ivities and specificities of 100% were obtained based on both T wave criter ia after 15 and 10 mug of epinephrine was injected IV. Two blinded observer s were able to detect all T wave changes in patients who received 15, 10, a nd 5 mug of epinephrine IV, resulting in 100% efficacy (P < 0.05 versus HR and SBP criteria). We conclude that minimum effective epinephrine doses for detecting accidental intravascular injection are 15 <mu>g on the HR and th e SBP criteria, and 10 mug on both T wave criteria, and that observing T wa ve changes may detect even smaller (5 mug) doses of epinephrine injected IV in adult patients anesthetized with sevoflurane and nitrous oxide.