The efficacy of perfusion index as an indicator for intravascular injection of epinephrine-containing epidural test dose in propofol-anesthetized adults

Abstract

BACKGROUND: Perfusion index (PI) is a noninvasive numerical value of peripheral perfusion obtained from a pulse oximeter. In this study, we evaluated the efficacy of PI for detecting intravascular injection of a simulated epidural test dose containing 15 μg of epinephrine in adults during propofol-based anesthesia and compared its reliability with the conventional heart rate (HR) (positive if ≥ 10 bpm) and systolic blood pressure (SBP) (positive if ≥ 15 mm Hg) criteria. METHODS: Forty patients scheduled for elective general surgery under total IV anesthesia were randomized to receive either 3 mL of lidocaine 15 mg/mL with epinephrine 5 μg/mL or 3 mL of saline IV (n = 20 each). HR, SBP, and PI were monitored for 5 min after injection. RESULTS: Injecting the test dose resulted in an average maximum PI decrease by 65% ± 13% at 39 ± 15 s. Moreover, maximal increases in HR and SBP were 19 ± 8 bpm at 49 ± 25 s and 17 ± 7 mm Hg at 102 ± 34 s after test dose injections, respectively. Using the PI criterion for intravascular injection (positive if PI decreases ≥ 10% from the preinjection value) the sensitivity, specificity, positive predictive, and negative predictive values were 100% (95% confidence interval [CI]; CI = 83%-100%). On the contrary, sensitivities of 95% (CI = 76%-99%) and 90% (CI = 70%-97%) were obtained based on HR and SBP criteria, respectively. CONCLUSION: PI is a reliable alternative to conventional hemodynamic criteria for detection of an intravascular injection of epidural test dose in propofol-anesthetized adult patients. © 2009 International Anesthesia Research Society.