T-wave amplitude as an indicator for detecting intravascular injection of epinephrine test dose in awake and anesthetized elderly patients

Abstract

Aging is associated with reduced heart rate (HR) responsiveness to a simulated IV test dose containing epinephrine. We tested the hypothesis that a more contemporary T-wave criterion (positive if there was a > or = 25% decrease in T-wave amplitude) was applicable in both awake and anesthetized older patients. Sixteen healthy patients > or = 65 yr old first received 3 mL of normal saline IV, followed 4 min later by 1.5% lidocaine 3 mL containing 15 microg epinephrine (1:200,000) IV in the supine position when awake, and they were anesthetized with stable 2% end-tidal sevoflurane and 67% nitrous oxide. HR, systolic blood pressure (SBP) determined invasively, and lead II of the electrocardiogram were continuously recorded for 4 min after the IV injections of saline and the test dose. A sensitivity of 88% and a negative predictive value of 89% were obtained in awake patients on the basis of the conventional HR criterion (positive if there was a > or = 20 bpm increase), whereas a sensitivity of 81% and a negative predictive value of 84% were obtained during sevoflurane anesthesia on the basis of the modified HR criterion (positive if there was a > or = 10 bpm increase). However, sensitivities, specificities, and positive and negative predictive values were all 100% on the basis of the SBP (positive if a > or = 15 mm Hg increase was recorded with an arterial line) and the T-wave criteria for both awake and anesthetized conditions. These results suggest that the SBP and T-wave criteria should be applied in awake and anesthetized elderly patients for detecting accidental intravascular injection of the epinephrine-containing test dose.

Implications: To determine whether an epidural catheter is in a blood vessel, an epidural test dose containing 15 microg epinephrine is often used. We found that an increase in systolic blood pressure and a decrease in T-wave amplitude, but not an increase in heart rate, seem to be reliable indicators for detecting accidental intravascular injection in both awake and sevoflurane-anesthetized patients > or = 65 yr old.