Abstract
Objective
The aim of this study was to review and evaluate the selection and dose of anesthetic agents and the interval from the block procedure to skin incision for supraclavicular brachial plexus block in upper extremity surgery.
Methods
We reviewed our cases that underwent upper extremity surgery using only ultrasound-guided supraclavicular brachial plexus block in our hospital between 2011 and 2016. Adverse events during surgery were evaluated. Receiver operating characteristic (ROC) curves were constructed to investigate the relationship between the time from the end of the block procedure to skin incision and the use of local anesthesia on the surgical site.
Results
There were 255 patients who were divided into three groups according to the anesthetic agents used: group 1, 1% lidocaine (L) 10 ml + 0.75% ropivacaine (R) 20 ml (n = 62); group 2, L 20 ml + R 10 ml (n = 93); and group 3, L 10 ml + R 15 ml (n = 100). The rate of use of local anesthesia on the surgical site was significantly higher in group 3 than in the other two groups. There were no significant differences in the other evaluated items among the three groups. ROC curve analysis indicated that ≥24 min from the end of the block procedure to skin incision might reduce the use of local anesthesia.
Conclusion
The total volume of anesthetic agents had an important influence on the rate of the addition of local anesthesia for surgical pain; however, the combined dose of agents did not influence the evaluation items. For effective analgesia, ≥24 min should elapse from the end of the block procedure to skin incision.
Keywords
Ultrasound-guided supraclavicular brachial plexus block; Upper extremity surgery; Anesthetic agents; Local anesthesia; Analgesia;
1. Introduction
Ultrasound-guided supraclavicular brachial plexus block (BPB) has achieved widespread acceptance and is effective for upper extremity surgery.1,2 It can be used as support for general anesthesia as well as the sole agent for analgesia throughout an upper extremity surgery. In the past, BPB was achieved by nerve stimulation guidance, but the development of ultrasound devices has made ultrasound-guided block more acceptable than block guided by nerve stimulation.3–6
Although there are several reports on the effectiveness of brachial plexus block for upper extremity surgery, there is still no clear consensus on the choice and dose of anesthetic agents to achieve sufficient analgesia for upper extremity surgery. These agents are usually selected at the discretion of the attending anesthesiologists or surgeons. In general, the choice of a particular local anesthetic agent depends mainly on the expected time of action in relation to the duration of surgery and anticipated postoperative pain.1 The use of mixtures of various agents, such as lidocaine, bupivacaine or ropivacaine with or without epinephrine, is a controversial issue.7–9However, such mixtures combine the advantages of quick onset of action and long-lasting analgesia. One example is a mixture of 2% lidocaine and 0.5% bupivacaine (with the addition of adrenaline). The use of agents in the same concentration guarantees reliable motor block, which is highly desirable during surgery.10–13Generally, 25–35 ml of solution is administered, although markedly lower volumes have also been reported to be effective, reducing the risk of complications.1
There is also still no consensus on an appropriate interval between the end of the block procedure and skin incision for effective analgesia. It is known that effective block is generally obtained after 20–30 min (the more precise the agent administration, the quicker the onset of its action)2,10–13; however, more precise information is needed.
The aim of this study was to review and evaluate the choice and dose of anesthetic agents for supraclavicular BPB in upper extremity surgery in our institute, and also to investigate the relationship between the time from the end of the block procedure to the skin incision and the use of local anesthesia on the surgical site for the most effective analgesia.
2. Methods
We reviewed our cases that underwent upper extremity (hand, wrist, forearm and elbow) surgery under only ultrasound-guided supraclavicular brachial plexus block, not including those who underwent surgery under general anesthesia, in our hospital between 2011 and 2016. Patients' characteristics and mixtures and doses of anesthetic agents were collected. Ultrasound-guided supraclavicular brachial plexus block was performed by orthopedic surgeons. Ethical approvals were obtained from the Ethics Committee of Tokyo Women's Medical University (No.4075) and that of Saitama Medical Center, Japan Community Health care Organization (No.16-6).
2.1. Block technique
We used a LOGIQe® or Venue 40® (GE HealthCare, USA) ultrasound system with a 12-MHz linear transducer. The transducer was placed in the supraclavicular fossa parallel to the midshaft of the clavicle, and an attempt was made to visualize the subclavian artery in transverse section. After the subclavian artery and brachial plexus were visualized, a needle was inserted parallel to the transducer. The site of needle insertion was close to the transducer, and the needle was introduced in a plane from the lateral to the medial side. The course of the needle during insertion was continuously controlled. Subsequently, the sheath was penetrated with the needle and half of the total volume of the solution containing local anesthetics was administered to the bundle itself. To increase the probability of blocking the fibers originating from C8–Th1 (mainly the ulnar nerve), the second half of the dose was given in the corner pocket14 — a term taken from billiards to describe the junction between the subclavian artery and the first rib.
2.2. Evaluation
Adverse events during surgery were evaluated including the use of local anesthesia (1% lidocaine) on the surgical site (due to pain), the rate of tourniquet pain, the administration of intraoperative opioid, and the rate of low SpO2 or local anesthetic systemic toxicity (LAST) during surgery. Additionally, we constructed receiver operating characteristic (ROC) curves to investigate the relationship between the time elapsed from the end of the block procedure to skin incision and the use of local anesthesia on the surgical site.
2.3. Statistical analysis
All statistical analyses were performed with EZR (Saitama Medical Center, Jichi Medical University), which is a Japanese graphical user interface for R (The R Foundation for Statistical Computing, Vienna, Austria). Categorical and continuous variables were compared among the three groups by a Kruskal–Wallis test and a one-way analysis of variance (ANOVA), respectively. For intergroup comparisons after the ANOVA, multiple post-hoc tests were performed. Spearman's rank correlation coefficient was used to find correlations between adverse events that were significantly different among the three groups and patient's characteristics. A P value < 0.05 was considered significant.
3. Results
There were 255 patients who underwent upper extremity surgery in our hospital between 2011 and 2016 (Table 1). The only anesthetic agents used were 1% lidocaine (L) and 0.75% ropivacaine (R). Patients were divided into three groups according to their anesthetic agents: group 1, L 10 ml + R 20 ml, total 30 ml (n = 62); group 2, L 20 ml + R 10 ml, total 30 ml (n = 93); group 3, L 10 ml + R 15 ml, total 25 ml (n = 100). There were no obvious criteria for the use of these three formulations; however, the mixture in group 1 was mainly used from 2011 to 2013, whereas the other mixtures were mainly used from 2014 to 2016. This might have been because our surgeons selected the mixtures and volumes at their discretion. There were no patients who received other combinations of anesthetic agents during this period.
The evaluation items are shown in Table 2. According to the statistical analysis, the rate of use of local anesthesia on the surgical site was significantly higher in group 3 than in the other two groups (vs group 1: P = 0.0016; vs group 2: P = 0.0043), but there was no difference between groups 1 and 2 (P = 0.4330). There were no significant differences in the other evaluated items among the three groups; however, low SpO2 and LAST were slightly more frequent in group 2. Spearman correlations between the rate of use of local anesthesia and patients' characteristics are shown in Table 3. In the unadjusted analysis, there have been a correlation between higher BMI or shorter total operation time and the rate of use of local anesthesia (P < 0.05). About surgical area, elbow surgery was significant association with the rate of use of local anesthesia (P < 0.05).
ROC curves were constructed to evaluate the relationship between the time from the end of the block procedure to skin incision and the rate of use of local anesthesia on the surgical site (Fig. 1). The area under the ROC curve (AUC) for group 3 did not reach statistical significance. The AUC for group 1 was 0.587 (sensitivity 50.0%, specificity 79.2%, 95% confidence interval (CI) 0.403 to 0.771) and that for group 2 was 0.723 (sensitivity 69.2%, specificity 77.3%, 95% CI 0.605 to 0.842). The sensitivity/(1-specificity) ratio reached a maximum at a cutoff value of 24 min in both groups 1 and 2. ROC curve analysis indicated that ≥24 min from the end of the block procedure to skin incision might reduce the rate of use of local anesthesia in both groups 1 and 2.
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4. Discussion
In this study, the volume of anesthetic agents in group 3 was 25 ml, and this group had a higher incidence of the addition of local analgesia during surgery than both groups 1 and 2 (both of these groups had a 30-ml volume of anesthetic agents). Therefore, the total volume of anesthetic agents administered had an important influence on the incidence of the addition of local anesthesia for surgical pain. Moreover, since there was no significant difference between groups 1 and 2, the volume of each agent in the mixture was not important. However, in group 2, which had more lidocaine than group 1, the rates of low SpO2 and LAST were slightly higher than those in group 1. Thus, less lidocaine might be better to avoid these adverse events.
Our ROC curve analysis on the relationship between the addition of local anesthesia and the time from the end of the block procedure to skin incision showed that ≥24 min might reduce the rate of use of local anesthesia in groups 1 and 2, but there was no significant difference between these two groups. ROC curve analysis in group 3 showed that the area under the curve was not significant. Therefore, the total volume of anesthetic agents might also be important for the onset of an analgesic effect.
LAST is a frequent complication and is dose dependent. Therefore, reducing the dose of local anesthetic in regional anesthesia can contribute to the safety of this procedure.14 According to our results, less lidocaine might be better to avoid LAST because the rate of LAST was slightly higher in group 2, which had more lidocaine than group 1. There was an interesting report about ultrasound-guided subcostal transversus abdominis plane block (TAPB), which showed that administration of ropivacaine at 3 mg/kg was effective for analgesia, and there were no adverse events or clinical symptoms indicating systemic toxicity.9 Thus, this method might be optimal to provide the minimum dose of ropivacaine for safe and effective local anesthesia.
Meco et al compared supraclavicular BPB and distal peripheral nerve blocks with supraclavicular BPB alone.2 According to their results, the onset of anesthesia in the group with supraclavicular BPB alone using 32 mL of 1.5% lidocaine with epinephrine (5 μg/mL) was 20 (15–30) minutes. In another study that investigated the speed of onset of ‘corner pocket supraclavicular’ BPB, the mean time to successful sensory block was 22 min.15 Their results were similar to the results of our ROC analysis; however, there were some differences between our methods and theirs. In both of the previous studies, only lidocaine (with epinephrine) was used for supraclavicular BPB, whereas two anesthetic agents and three mixtures were used in our study. Thus, our study is novel in that three mixtures for supraclavicular BPB were compared, although the comparison was retrospective.
It is controversial whether long-acting anesthetic agents alone or in a minimally diluted concentration can achieve block onset times that are similar to those achieved by high-concentration, short-acting anesthetic agents. Cuvillon et al reported that mixtures of long-acting local anesthetics (bupivacaine or ropivacaine) with lidocaine induced faster onset of block when they were used for femoral and sciatic nerve blocks.16 On the other hand, Jeff, et al reported that a combination of mepivacaine 1.5% and bupivacaine 0.5% resulted in a block onset time similar to that obtained when either local anesthetic was used alone for ultrasound-guided interscalene block.17 Our results showed that the total volume of a mixture of agents affected the onset of analgesia and this is consistent with the latter study. Their methods and ours were similar; however, upper extremity block was induced in Jeff's study and ours, whereas lower extremity block was induced in Meco's study. This might partially explain the reason for the different results.
Our study has several limitations. First, this was a retrospective study, and the indication for block was not as rigorous as it might have been in a prospective study, and there was also a lack of criteria for administrating additional analgesics, local infiltration of 1% lidocaine, and intraoperative opioid. Furthermore, there were differences in patients' characteristics among the three groups, including BMI, surgical area and total operation time. Since there were many more women than men in this study, the present results might only apply to women. Additional limitations are that we included a relatively small number of cases and used only two anesthetic agents. Also, in ROC analysis, only the AUC of group 2 was high, and the others were relatively low or not significant. In addition, the conclusions based on our ROC analysis might only apply to the patients enrolled in this study.
In conclusion, our results showed that the total volume of anesthetic agents administered had an important influence on the rate of use of local anesthesia for surgical pain. A combined dose of lidocaine and ropivacaine did not influence the evaluation items, but less lidocaine seemed to be better because some adverse events were slightly less frequent. For effective analgesia, ≥24 min should elapse from the end of the block procedure to skin incision.
Conflicts of interest
The study has not received any external funding and the authors declare that they have no conflicts of interest.