Background and Objectives A test dose containing epinephrine is routinely used during epidural blockade to detect accidental intravenous needle or catheter placement before the administration of local anesthetics to avert local anesthetic systemic toxicity. β-Blocker therapy may interfere with the expected hemodynamic response from an intravascular injection. This study describes a cohort of 24 patients and their response to an epinephrine test dose (ie, if expected increased heart rates during test-dose administration are valid in this population.)
Methods Twenty-four nonsedated, chronically β-blocked patients were enrolled in a prospective, order-randomized, crossover, double-blind study with injections of both placebo and a 15-μg epinephrine test dose in each individual. After injection into a peripheral vein, we observed blood pressure and pulse rate for 5 minutes, injected the other remaining solution (placebo or epinephrine), and observed hemodynamic parameters in the same fashion.
Results Epinephrine raised the heart rate 17.8 beats per minute (bpm) (95% confidence interval [CI], 15.5–20.1) versus placebo 2.0 bpm (95% CI, − 0.3–4.3 P < 0.001) and the systolic blood pressure 23 mm Hg (95% CI, 17.2–28.9) versus placebo 4.4 (95% CI, − 1.5–10.3); P < 0.001 in our chronically β-blocked population. A threshold increase of 20 bpm yielded a sensitivity of 37.5% (95% CI, 18.8%–59.4%) and specificity of 100% (95% CI, 85.8%–100%). Revising a threshold to include a change of 10 bpm or increase in systolic blood pressure of 15 mm Hg or greater yielded 100% (95% CI, 85.8%–100%) sensitivity and 87.5% (95% CI, 67.6%–97.3%) specificity.
Conclusions Epinephrine test-dose administration in nonsedated, chronically β-blocked patients cannot distinguish intravenous injection at the classic threshold increase of 20 bpm. The response in individuals is varied, and thresholds for a positive test need revising for this population of patients on therapeutic β-blockers.
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This work done in the Department of Anesthesiology at Virginia Mason Medical Center.
Sources of financial support: Institutional and Departmental sources and in part by the Daniel C. Moore/L. Donald Bridenbaugh Research Fellowship (to M.R.H.).
This work has been presented at the American Society of Anesthesiologists Annual Meeting in Chicago, October 2011.
The authors declare no conflict of interest.
”C.M.B. is deceased.
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