The efficacy of plethysmographic pulse wave amplitude as an indicator for intravascular injection of epinephrine-containing epidural test dose in anesthetized adults.

In this study, I evaluated the efficacy of plethysmographic pulse wave amplitude (PPWA) in detecting intravascular injection of a simulated epidural test dose containing 15 microg of epinephrine in adults during either sevoflurane or isoflurane inhaled anesthesia and compared its reliability to the classical heart rate (HR; positive if > or =10 bpm) and systolic blood pressure (SBP; positive if > or =15 mm Hg) criteria. Eighty patients were randomized to receive either 1 mean alveolar anesthetic concentration of sevoflurane or 1 mean alveolar anesthetic concentration of isoflurane (n = 40 for each anesthesia group). Patients in each anesthesia group microg of epinephrine IV or 3 mL of saline IV (n = 20 each). HR, SBP, and PPWA were monitored for 5 min after injection. Injection of the test dose resulted in peak PPWA decrease by 61% +/- 17% and 58% +/- 15% at 61 +/- 12 s and 63 +/- 13 s in the sevoflurane and isoflurane groups, respectively. Positive PPWA criterion, as determined from peak increases during saline administration, was a decrease in PPWA > or =10%. Using this value, the sensitivity, specificity, positive predictive, and negative predictive values of PPWA were 100% in both anesthetic groups. On the contrary, sensitivities of 85% and 95% were obtained based on HR criterion in the sevoflurane and isoflurane patients, respectively, and a sensitivity of 90% was obtained in both anesthesia groups on the basis of SBP criterion. In conclusion, PPWA is a reliable alternative to conventional hemodynamic criteria for detection of an intravascular injection of epidural test dose.