Fentanyl Pretreatment Does Not Impair the Reliability of an Epinephrine-Containing Test Dose During Propofol-Nitrous Oxide Anesthesia

Abstract

We designed this study to determine the hemodynamic responses to and the efficacy of a simulated IV test dose during propofol anesthesia based on the conventional heart rate (HR; positive if increase ≥20 bpm), the modified HR (positive if increase ≥10 bpm), and the systolic blood pressure (SBP; positive if increase ≥15 mm Hg) criteria. Eighty healthy patients were randomized to receive 2 mg/kg propofol or propofol plus fentanyl (100 μg) at the induction of anesthesia (n = 40 each). After endotracheal intubation, anesthesia in both groups was maintained with propofol 8 mg · kg−1 · h−1 and 67% nitrous oxide in oxygen. Each group of patients was further divided into a test dose group receiving 1.5% lidocaine 3 mL plus epinephrine 15 μg (1:200,000) or a saline group ( n = 20 each) receiving 3 mL of isotonic sodium chloride solution IV. HR and SBP were monitored for 4 min after the IV injection of the study drug. The IV injection of the test dose produced a HR increase ≥20 bpm in 20 and 17 patients in the propofol and propofol-fentanyl groups, respectively, whereas all patients receiving the test dose and none receiving saline had HR increases ≥10 bpm. Therefore, in the propofol-fentanyl group, sensitivity, specificity, positive predictive value, and negative predictive value were 85%, 100%, 100%, and 87% according to the conventional HR criterion, and all were 100% according to the modified HR criterion. In the propofol group, 100% efficacy was obtained based on both HR criteria. However, all patients receiving the test dose and none receiving saline developed a SBP increase ≥15 mm Hg, resulting in 100% efficacy based on the conventional SBP criterion in both groups. Our results indicate that both the modified HR criterion and the SBP criterion are clinically applicable during propofol anesthesia with or without supplemental fentanyl. Implications To determine whether an epidural catheter is in a blood vessel, an epidural test dose containing 15 μg of epinephrine is used. We found that, during propofol anesthesia with or without fentanyl, a heart rate increase ≥10 bpm and a systolic blood pressure increase ≥15 mm Hg are reliable indicators for detecting accidental intravascular injection.