Department of Anesthesiology, Virginia Mason Medical Center, Seattle, WA 98101, USA.
Reg Anesth Pain Med. 2013 Sep-Oct;38(5):403-8. doi: 10.1097/AAP.0b013e31829bb9fa.
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.)
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.
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.
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.
在硬膜外阻滞期间，常规使用含肾上腺素的试验剂量，以在局部麻醉剂给药之前检测意外的静脉内针或导管放置，以避免局部麻醉剂全身毒性。β受体阻滞剂治疗可能会干扰血管内注射引起的预期血流动力学反应。本研究描述了 24 例患者及其对肾上腺素试验剂量的反应（即，在该人群中，试验剂量给药期间预期的心率增加是否有效）。
24 例未镇静的慢性β受体阻滞剂患者入组前瞻性、顺序随机、交叉、双盲研究，每位患者分别注射安慰剂和 15μg 肾上腺素试验剂量。外周静脉注射后，我们观察 5 分钟的血压和脉搏率，注射另一种剩余溶液（安慰剂或肾上腺素），并以相同方式观察血流动力学参数。
肾上腺素使心率升高 17.8 次/分钟（95%置信区间 [CI]，15.5-20.1），而安慰剂组仅升高 2.0 次/分钟（95% CI，-0.3-4.3；P <0.001），收缩压升高 23mmHg（95% CI，17.2-28.9），而安慰剂组升高 4.4mmHg（95% CI，-1.5-10.3）；在我们的慢性β受体阻滞剂人群中，P <0.001。阈值增加 20 次/分钟，敏感性为 37.5%（95% CI，18.8%-59.4%），特异性为 100%（95% CI，85.8%-100%）。将阈值修改为包括心率增加 10 次/分钟或收缩压增加 15mmHg 或更高，可获得 100%（95% CI，85.8%-100%）的敏感性和 87.5%（95% CI，67.6%-97.3%）的特异性。
在未镇静的慢性β受体阻滞剂患者中，肾上腺素试验剂量给药不能区分经典阈值增加 20 次/分钟的静脉内注射。个体的反应是不同的，需要为接受治疗性β受体阻滞剂的患者群体修改阳性试验的阈值。
