Liu S, Carpenter R L, Chiu A A, McGill T J, Mantell S A
Department of Anesthesiology, Virginia Mason Medical Center, Seattle, Washington 98111, USA.
Reg Anesth. 1995 Sep-Oct;20(5):378-84.
Epinephrine is frequently combined with local anesthesia to prolong analgesia. Determination of the minimal concentration and the dose of epinephrine that produces prolongation of analgesia is important in the face of epinephrine's potential for systemic and local toxicity. The authors undertook this study to determine a dose-response curve of epinephrine on duration of analgesia of both 1% lidocaine and 0.25% bupivacaine after local infiltration. In order to determine whether epinephrine-induced vasoconstriction affected duration of analgesia, the authors correlated duration of analgesia with magnitude of local vasoconstriction as measured with laser Doppler flowmetry.
Six volunteers were studied in a randomized double-blind manner. Ten skin wheals of 0.2 mL solution were subcutaneously injected into both forearms of each volunteer. The solutions consisted of 1% lidocaine with epinephrine concentrations of 0, 1:50,000, 1:200,000, 1:800,000, and 1:3,200,000, and 0.25% bupivacaine with the same epinephrine concentrations. Duration of loss of sensation to pinprick at each wheal was recorded. Skin wheals with 0.2 mL of these same solutions were also subcutaneously injected into the abdomen of the same 6 volunteers, and laser Doppler flowmetry readings of skin blood flow were measured for 6 hours after injection.
Epinephrine prolonged duration of analgesia for both lidocaine and bupivacaine in a dose-related manner (P < .001). All concentrations of epinephrine attenuated the vasodilation observed in the first 15 minutes after injection with plain local anesthesia (P = .03), and blood flow returned to baseline by 30 minutes after injection of either plain or epinephrine-containing solutions. Duration of analgesia correlated with magnitude of vasoconstriction only at the 15-minute measurement (r = .53 and .57, P = .003 and 0.001 for lidocaine and bupivacaine, respectively).
Epinephrine prolongs duration of analgesia after local infiltration in a dose-related manner. Addition of epinephrine in concentrations of 1:50,000 or 1:200,000 increases duration of analgesia after local infiltration by approximately 200%. Addition of doses as dilute as 1:3,200,000 still increases duration of analgesia by approximately 100%. Duration of analgesia appears to correlate with magnitude of epinephrine-induced vasoconstriction using laser Doppler flowmetry. Based on study data, the use of epinephrine in concentrations from 1:200,000 to 1:3,200,000 is recommended for prolongation of analgesia after local infiltration.
肾上腺素常与局部麻醉药联合使用以延长镇痛时间。鉴于肾上腺素存在全身和局部毒性的可能性，确定能产生镇痛时间延长的肾上腺素最小浓度和剂量至关重要。作者开展本研究以确定肾上腺素对局部浸润后1%利多卡因和0.25%布比卡因镇痛持续时间的剂量反应曲线。为了确定肾上腺素诱导的血管收缩是否影响镇痛持续时间，作者将镇痛持续时间与用激光多普勒血流仪测量的局部血管收缩程度进行关联。
对6名志愿者进行随机双盲研究。在每位志愿者的双侧前臂皮下注射10个0.2 mL溶液的皮丘。溶液包括肾上腺素浓度为0、1:50,000、1:200,000、1:800,000和1:3,200,000的1%利多卡因，以及肾上腺素浓度相同的0.25%布比卡因。记录每个皮丘对针刺感觉丧失的持续时间。同样将0.2 mL这些相同溶液的皮丘皮下注射到相同6名志愿者的腹部，并在注射后6小时测量皮肤血流的激光多普勒血流仪读数。
肾上腺素以剂量相关的方式延长了利多卡因和布比卡因的镇痛持续时间（P <.001）。所有浓度的肾上腺素均减弱了单纯局部麻醉注射后最初15分钟内观察到的血管舒张（P =.03），并且在注射单纯溶液或含肾上腺素溶液后30分钟血流恢复到基线水平。仅在15分钟测量时镇痛持续时间与血管收缩程度相关（利多卡因和布比卡因的r分别为.53和.57，P分别为.003和0.001）。
肾上腺素以剂量相关的方式延长局部浸润后的镇痛持续时间。添加1:50,000或1:200,000浓度的肾上腺素可使局部浸润后的镇痛持续时间增加约200%。添加低至1:3,200,000的剂量仍可使镇痛持续时间增加约100%。使用激光多普勒血流仪时，镇痛持续时间似乎与肾上腺素诱导的血管收缩程度相关。基于研究数据，建议使用浓度为1:200,000至1:3,200,000的肾上腺素来延长局部浸润后的镇痛时间。
