A comparative study of hemodynamic and T-wave criteria for detecting intravascular injection of the test dose (epinephrine) in sevoflurane-anesthetized adults.

This study was designed to determine the efficacy of heart rate (HR), systolic blood pressure (SBP), and changes in T-wave morphology in detecting intravascular injection of 15 microg of epinephrine (test dose) in sevoflurane-anesthetized adults. In addition, the testing threshold using the T-wave amplitude was derived. Ninety-six healthy patients were randomized to receive end-tidal sevoflurane 0.5%, 1%, or 2% and nitrous oxide 67% in oxygen (n = 32 for each sevoflurane concentration). Each group of patients was further randomized to receive 3 mL of 1.5% lidocaine plus 15 microg of epinephrine IV or 3 mL of saline IV (n = 16 each). HR, SBP, and T-wave amplitude were continuously monitored for 5 min after the IV injection of the study drug. None receiving IV saline and 15,15, and 14 patients receiving the IV test dose developed HR increases > or =10 bpm during 0.5%, 1%, and 2% sevoflurane, respectively. No patient receiving saline and all patients receiving the test dose developed SBP increases > or =15 mm Hg. T-wave amplitude decreased by >0.1 mV and by >25% in all patients receiving the IV test dose, and its magnitude was similar regardless of the sevoflurane concentrations. When 0.1-mV and 25% decreases in T-wave amplitude were considered as testing thresholds, 100% sensitivities and specificities were obtained. We conclude that a peak SBP increase > or =15 mm Hg and a decrease in T-wave amplitude > or =0.1 mV and > or =25% are more reliable than a HR increase > or =10 bpm for detecting intravascular injection of epinephrine-containing test dose during sevoflurane anesthesia. IMPLICATIONS: To determine whether an epidural catheter resides in a blood vessel, a standard test dose containing a local anesthetic and 15 microg of epinephrine is used. We found that, in sevoflurane-anesthetized adult patients, a systolic blood pressure increase > or =15 mm Hg and a decrease in T-wave amplitude > or =0.1 mV and > or =25% in lead II, but not a heart rate increase > or =10 bpm, are reliable indicators for detecting intravascular injection.