Does the Choice of Electrocardiography Lead Affect the Efficacy of the T-Wave Criterion for Detecting Intravascular Injection of an Epinephrine Test Dose?

UNLABELLED: Accidental intravascular injection of an epinephrine-containing test dose decreases the T-wave amplitude of a Lead II electrocardiogram (EKG) with 100% sensitivity and specificity on the basis of the T-wave criterion (positive if there is a > or =25% decrease in amplitude). We designed this study to test whether the choice of EKG lead would affect the efficacy of the simulated intravascular test dose in anesthetized patients. After an 8-h fast and no premedication, 35 healthy patients were anesthetized with end-tidal 2% sevoflurane and nitrous oxide after endotracheal intubation. When hemodynamic stability was obtained, all subjects received 3 mL of normal saline IV, followed 4 min later by 1.5% lidocaine 3 mL plus 15 microg of epinephrine (1:200,000) IV. Heart rate, systolic blood pressure, Leads II (n = 35) and V(5) (n = 35), and either Lead I (n = 17) or III (n = 18), whichever had the greater T-wave amplitude, were continuously recorded for 4 min after the saline and test-dose injections. An IV test dose produced significant increases in heart rate and systolic blood pressure and produced decreases in the T-wave amplitude of all EKG leads studied in all subjects, whereas IV saline elicited no changes in these variables. The maximum percentage decreases in T-wave amplitude of Leads II, I, III, and V(5) were -87% +/- 13%, -88% +/- 8%, -94% +/- 15%, and -86% +/- 16%, respectively (mean +/- SD; P > 0.05). There was no significant difference in temporal changes in T-wave amplitude among the 4 leads, and sensitivity and specificity were 100% on the basis of the T-wave criterion, irrespective of the lead examined. Our results indicate that Leads II, I, III, and V(5) of the EKG are equally effective for detecting intravascular injection of the epinephrine-containing test dose in sevoflurane-anesthetized adults. IMPLICATIONS: To determine whether an epidural catheter is in a blood vessel, an epidural test dose containing 15 microg of epinephrine is used. We found that decreases in the T-wave amplitude of Leads I, II, III, and V(5) of the electrocardiogram were equally sensitive and specific for detecting intravascular injection of the test dose in sevoflurane-anesthetized adult patients.