BACKGROUND: This study evaluated the efficacy of a T-wave change after the IV administration of low dose epinephrine containing the test dose during spinal anesthesia. METHODS: Eighty healthy adults undergoing spinal anesthesia were enrolled in this study. The subjects were divided randomly into the following 4 groups: Group S (n = 20) received 3 ml of normal saline, group L (n = 20) received 3 ml of 1.0% lidocaine, group E5 received 3 ml of 1.0% lidocaine with epinephrine 5 microgram, and group E10 received 3 ml of 1.0% lidocaine with epinephrine 10 microgram. The heart rate (HR) and T-wave amplitude were measured with an electrocardiogram and systolic blood pressure (SBP) using a non-invasive method. Positive responses were defined as an increase in HR > or = 20 bpm or SBP > or = 15 mmHg, or a decrease in the T-wave amplitude > or = 25%. RESULTS: The sensitivity (Ss), specificity (Sp), positive predictive value (PPV), and negative predictive value (NPV) of the HR increases were 80%, 100%, 100%, and 83%, respectively, in groups E5 and E10. For the SBP increases, the Ss, Sp, PPV, and NPV were respectively, 55%, 100%, 100%, and 70% in group E5, and 80%, 100%, 100%, and 83% in group E10. For the > or = 25% decrease in T-wave amplitude, Ss, Sp, PPV, and NPV were respectively, 100%, 90%, 91%, and 100% in group E5, and 95%, 90%, 90%, and 95% in group E10. CONCLUSIONS: These results suggest that a change in the T-wave amplitude is useful for detecting the unintentional IV administration of low dose epinephrine during CSEA.