Period of latency, progression and duration of blockade of epidural anesthesia with lidocaine, bupivacaine or its association in dogs

ABSTRACT The objective of this study was to evaluate the latency, duration of the effect, and cranial progression of lidocaine and bupivacaine alone or in combination, by epidural route in dogs, and measuring the average pressure of the epidural channel before and after the completion thereof. Eighteen dogs were allocated in three groups, which received epidural: lidocaine 2% (GL) 0.25ml / kg; bupivacaine 0.5% (GB) in the same volume, or the association of both (GLB) in a 1: 1 ratio. Heart and respiratory rates and systolic blood pressure (SBP) were evaluated before treatment (M0) and up to 60 minutes after epidural anesthesia. In addition, the pressure in the epidural canal was evaluated before and after the administration of the treatments, latency period, progression and duration of the block by interdigital and paravertebral pannicus clamping. There was a 12% decrease in SBP in the GL at all times and 16% at 30 minutes in GLB when compared to the baseline. The mean pressure in the epidural space before and after epidural anesthesia was -1.5 (±3.9) and 41 (±16) mmHg), 55% presented negative pressure in the epidural space. The latency period did not differ between groups (GL: 3.5±1.6; GB: 4.5±4.5; and GLB: 2.4±1 minutes) and the duration of blockade was higher in GB (GL: 125±24, GB: 176±24, and GLB: 153±35 minutes). The maximum progression of anesthetics was up to L1-T13 in GL, L4-L3 in GB and L3-L2 in GLB. It is concluded that the association of lidocaine with bupivacaine does not present advantages in relation to the use of the drugs isolated by the epidural route, with lidocaine progressing more cranially in relation to bupivacaine or the association. Lidocaine promoted the reduction of SBP, even when associated with bupivacaine, remaining within the reference values. Only 55% of the dogs presented negative mean pressure in the epidural space before administration of the drugs, so the drop test may not be efficient for locating the epidural space in all animals.

摘要 本研究旨在评估单独或联合应用利多卡因（lidocaine）与布比卡因（bupivacaine）经硬膜外途径给药后在犬体内的起效潜伏期、作用持续时间及麻醉药头侧扩散情况，并测定给药前后硬膜外腔的平均压力。将18只犬随机分为三组，分别经硬膜外给予2%利多卡因（GL组）0.25ml/kg、0.5%布比卡因（GB组）同等体积药液，或按1:1比例联合使用两种药物（GLB组）。分别于给药前（M0）及硬膜外麻醉后60分钟内监测心率、呼吸频率及收缩压（SBP）。此外，采用趾间与椎旁皮褶钳夹法，评估给药前后的硬膜外腔压力、神经阻滞的潜伏期、扩散范围及持续时长。与基础值相比，GL组各时间点收缩压均下降12%，GLB组在给药后30分钟时收缩压下降16%。硬膜外麻醉前后硬膜外腔平均压力分别为-1.5(±3.9)与41(±16)mmHg，其中55%的受试犬给药前硬膜外腔呈负压状态。各组起效潜伏期无显著差异（GL组：3.5±1.6分钟；GB组：4.5±4.5分钟；GLB组：2.4±1分钟）；GB组神经阻滞持续时长更长（GL组：125±24分钟，GB组：176±24分钟，GLB组：153±35分钟）。麻醉药的最大头侧扩散范围：GL组可达L1-T13，GB组为L4-L3，GLB组为L3-L2。研究表明，与单独使用两种药物相比，利多卡因与布比卡因联合硬膜外给药并无额外优势；且利多卡因的麻醉药头侧扩散范围较布比卡因或联合给药更广。利多卡因可降低收缩压，即便与布比卡因联合使用时，其降幅仍处于参考范围内。仅55%的受试犬给药前硬膜外腔呈负压状态，因此悬滴试验（drop test）并非适用于所有动物的硬膜外腔定位方法。