A recent study demonstrated 100% effectiveness of hemodynamic criteria during propofol anesthesia, when a full dose of an epinephrine (15 microg)-containing test dose was injected intravascularly. We designed this dose-response study to determine minimal effective epinephrine doses and efficacies of hemodynamic and T-wave criteria for detecting intravascular injection of the epinephrine test dose in propofol-anesthetized adults. Eighty healthy adult patients were randomly assigned to one of four groups according to a simulated IV test dose using propofol (133 microg center dot kg(-1) center dot min(-1)) and nitrous oxide (FIO(2) = 0.33) anesthesia after endotracheal intubation (n = 20 each). The Saline group received 3 mL of normal saline IV; the Epinephrine-15 group received 3 mL of 1.5% lidocaine containing 15 microg epinephrine; and the Epinephrine-10 and -5 groups received 2 and 1 mL of the test dose of the identical components, respectively. Heart rate (HR), systolic blood pressure (SBP), and lead II of the electrocardiogram were recorded continuously for 5 min after the IV injection of the study drug via a peripheral vein. Sensitivities and specificities of 100% were obtained based on the modified HR (positive if greater-than-or-equal to 10 bpm increase) and the T-wave (positive if greater-than-or-equal 25% in amplitude) criteria if greater-than-or-equal 5 microg of epinephrine was injected IV. Based on the SBP criterion (positive if greater-than-or-equal 15 mm Hg increase), however, 100% sensitivity and specificity were associated only with greater-than-or-equal 10 microg of epinephrine doses. These results suggest that the minimal effective epinephrine doses for detecting unintentional intravascular injection are 5 microg based on the HR and T-wave criteria, and 10 microg based on the SBP criterion in adult patients anesthetized with propofol and nitrous oxide.
Implications: Accidental migration of an epidural catheter into a blood vessel is often detected by hemodynamic changes after injecting an epidural test dose containing epinephrine. Our results suggest that 5 microg of epinephrine is not adequate to reliably produce hemodynamic and T-wave alterations in adult patients during propofol anesthesia.