By Niemi, Tomi T; Salmela, Liisa; Aromaa, Ulla; Pyhi, Reino; Rosenberg, Per H
Background and Objectives: The surgical site for the creation of an arteriovenous fistula at the lateral aspect of the distal forearm may be faster and more effectively blocked with the infraclavicular coracoid approach than with the axillary approach for brachial plexus block.
Methods: Sixty uremic patients scheduled for the creation of an arteriovenous fistula at the forearm were randomized to receive a single-injection brachial plexus block with 35 to 50 mL mepivacaine 0.95% with epinephrine using the infraclavicular coracoid approach (IC group) or the perivascular axillary approach (AX group). A distal muscular contraction elicited by a nerve stimulator at current
Results: At 30 and 45 minutes, complete loss of sensation was observed more often in group IC than AX in the cutaneous distribution of musculocutaneous nerve (62% v 30% [P
Conclusions: Blockade of the musculocutaneous nerve developed faster with the infraclavicular coracoid approach than with the axillary approach. The infraclavicular coracoid approach may be preferable in patients scheduled for the creation of an arteriovenous fistula at the forearm. Reg Anesth Pain Med 2007;32:55- 59.
Key Words: Brachial plexus block, Infraclavicular coracoid, Axillary.
Succesful musculocutaneous nerve block is usually essential in order to provide adequate anesthesia for the creation of an arteriovenous fistula for hemodialysis because this nerve innervates the lateral aspect of the distal forearm. Analgesia of the median and the radial nerve may also be necessary if the exploration of blood vessels is extended distally.
Although sensory block of the musculocutaneous nerve has been found adequate for hand and forearm surgery in 90% of single- injection perivascular axillary brachial plexus blocks,1 73% of patients may not have complete sensory block (i.e., “no sensation” to pinprick) of the musculocutaneous nerve.2 Because the musculocutaneous nerve leaves the brachial neurovascular compartment distal to the coracoid process, blockade of the nerve has been shown to be more consistent by using a lateral infraclavicular approach than a single-injection axillary brachial plexus approach.3,4 We hypothesized that in uremic patients scheduled for arteriovenous fistula creation, the musculocutaneous nerve and the entire surgical field could be more successfully blocked with a single-injection infraclavicular coracoid technique than with the perivascular axillary brachial plexus block technique.
The study protocol was approved by the Ethics Committee for Surgery of the Hospital District of Helsinki and Uusimaa. Sixty uremic patients, aged 26 to 83 years, scheduled for creation of an arteriovenous fistula for hemodialysis in the lateral antebrachial region gave their written informed consent and were enrolled in the study.
The patients received their regular medication on the morning of surgery. The patients were premedicated with intravenous diazepam before the brachial plexus block. Monitoring consisted of a 5-lead electrocardiogram (ECG), pulse oximetry, and non-invasive blood pressure measurement at 5-minute intervals.
Patients were randomized in 2 groups of 30 to receive either infraclavicular coracoid brachial plexus block (IC group) or axillary brachial plexus block (AX group). Randomization was based on an investigator-generated code that was sealed in sequentially numbered opaque envelopes. The blocks were performed by experienced senior staff members and assessed by an anesthetist who was blinded regarding the block approach.
After infiltration of the skin with 2 to 3 mL of lidocaine 10 mg/ mL, the brachial plexus was identified with a short-beveled electric stimulation needle (Stimuplex, 50 mm; B. Braun Melsungen AG, Melsungen, Germany) connected to a nerve stimulator by using a low current (
After obtaining a peripheral motor response from muscles innervated by 1 of the 4 main nerves at a current ≤0.5 mA, 35 to 50 mL of mepivacaine HCl 9.5 mg/mL with epinephrine 4.8 g/mL (each time a fresh solution was prepared by adding 2.5 mL epinephrine 0.1 mg/mL to 50 mL of mepivacaine HCl 10 mg/mL) was injected slowly in 3 to 5 minutes with intermittent aspiration. The volume of the mepivacaine solution was chosen according to the weight of the patient: 35 mL for 40 to 49 kg, 40 mL for 50 to 59 kg, 45 mL for 60 to 69 kg, and 50 mL for ≥70 kg. The arm was then brought to rest at the patient’s side. In group IC, the arm was resting at the patient’s side during the performance of block and thereafter until surgery.
Skin sensation to pinprick was tested by a groupblinded observer using a 27-gauge short-bevel needle before the block and 5, 15, 30, 45, and 60 minutes after injection of mepivacaine as well as at the end of the surgery. The tests were carried out in 4 areas: in the sensory distribution of median (dorsum of distal phalanx of the middle finger), musculocutaneous (lateral area of frontal forearm), radial (dorsum of proximal phalanx of the thumb), and ulnar nerves (dorsum of distal phalanx of the little finger). Motor power of the hand was tested at the same intervals by grip strength, as well as flexion and extension of the forearm at the elbow. Degree of sensation was graded as “sharp,””blunt,” or “no sensation” and motor power as “normal movement,””decreased movement,” or “no movement.” After surgery, the corresponding tests were performed at 30-minute intervals until 2 of the sensory test territories or motor power of the hand had recovered 1 grade on the test scale.
In case of surgical pain, the surgeon infiltrated lidocaine 10 mg/ mL locally, and 0.05 to 0.15 mg of fentanyl was administered intravenously, as needed. During surgery, intravenous midazolam (maximal dose of 5 mg) or low-dose propofol infusion (after the administration of 5 mg of midazolam) for anxiety was given if needed. Postoperative pain was treated with acetaminophen (intravenously or orally) or oxycodone (intravenously, intramuscularly, or orally), as required. Postoperatively, in the recovery room, the patients were asked to rate their degree of satisfaction about the anesthetic technique and its performance as “dissatisfied,””quite satisfied,””satisfied,” or “very satisfied.”
In our previous study, the musculocutaneous nerve block was absent or partial (pinprick sensation “normal” or “decreased”) in 73% of patients receiving a brachial plexus block by the perivascular axillary approach.2 According to the power analysis, we estimated that 25 patients per group would be needed to show a 50% better result (i.e., 36% of patients having absent or partial musculocutaneous nerve block) with an α- and β-error of 0.05 and 0.2, respectively. The results are expressed as mean values with standard deviation or medians with range. An unpaired Student t test or a Mann-Whitney rank sum test were used for comparison of the demographic variables and operative data. For the analysis of the quality of the block, a chi-square or Fisher exact test was used. Differences were regarded as statistically significant if P
Table 1. Patient Characteristics
In group IC, the brachial plexus could not be identified in 1 patient (body mass index 34 kg/m^sup 2^), and the block was successfully performed using the axillary approach. Thus, the number of patients included in the analysis of block development was 29 in group IC and 30 in group AX. The intra- and postoperative data of 2 group IC patients were excluded because the operating room was not available in time for the scheduled patient (delay of 2 and 3 hours, respectively) and of an additional patient in group IC because of unplanned use of a brachial tourniquet requiring general anest\hesia shortly before the end of surgery.
Data regarding patient characteristics are presented in Table 1. Most of the patients underwent primary reconstruction of an arteriovenous fistula. The rest of the procedures were reoperations, including 2 loop-graft procedures in the proximal region of forearm.
Table 2. Development of Sensory Blockade of the Hand With Infraclavicular Coracoid (IC) (n = 29) and Axillary (AX) (n = 30) Approach of Brachial Plexus Block
Nerve stimulation with a visible motor response was achieved at 0.4 (0.3-0.4) or 0.3 (0.3-0.4) mA (median, 25th/75th percentiles) in group IC or AX, respectively (P > .05). Median nerve motor response was observed in 18 patients in group IC and 21 patients in group AX, respectively. Radial and ulnar nerve motor responses were detected in 9 and in 1 patient in group IC, respectively, and in 8 and in 1 patient in group AX.
In group AX, 2 patients developed transient tachycardia after injection of the local anesthetic. A 51-year-old diabetic patient’s heart rate increased from 60 beats/min to 90 beats/min 10 minutes after the injection of 428 mg of mepivacaine with 216 g of epinephrine, and a transient ST depression of – 1.0 mm in V5 lead of an ECG was observed. She also experienced the insertion of block as uncomfortable and painful. The other group AX patient, a 68-year- old man with ischemic heart disease, had a heart rate increase from 60 beats/min to 93 beats/min with a ST depression of -2.2 mm in V5 lead of ECG 15 minutes after the injection of 428 mg of mepivacaine with 216 g of epinephrine. In both cases, metoprolol was administered intravenously, and the tachycardia with ST depression was shortlived. The patients had successful brachial plexus blocks for surgery. Otherwise, there were no druginduced side effects.
Brachial plexus blockade with mepivacaine using either technique provided similar anesthesia for surgery. Adequate surgical anesthesia, defined as “blunt sensation” or “no sensation” to pinprick in test territories of the ulnar, median radial, and musculocutaneous nerves at 60 minutes after injection of mepivacaine, varied between 90% to 97% group IC and 87% to 97% in group AX (P > .05, Table 2). More patients had pinprick analgesia (“blunt” or “no sensation” to pinprick) in the musculocutaneous nerve distribution 30 minutes after injection in group IC compared with group AX (P
Table 3. Development of Motor Power of the Hand With Infraclavicular Coracoid (IC) (n = 29) and Axillary (AX) (n = 30) Approach of Brachial Plexus Block
Complete pinprick analgesia (“no sensation” to pinprick) was also achieved faster in the musculocutaneous nerve distribution by using the infraclavicular coracoid versus the axillary approach (i.e., at 30 minutes 62% v 30% [P
During surgery, comparable amounts of locally infiltrated lidocaine (7 IC and 15 AX group patients, P > .05) and fentanyl IV (9 IC and 12 AX group patients, P > .05) were required in the study groups. The number of patients requiring neither lidocaine nor fentanyl did not differ between the groups (18 IC and 14 AX group patients). The amount of intraoperative midazolam was not different between the study groups. Low-dose propofol infusion was given in 2 patients in group IC and in 3 patients in group AX. The median (25th- 75th percentiles) operation time was 69 (58-94) minutes in the IC group and 75 (57-102) minutes in the AX group (P > .05).
At the end of surgery, the sensory and motor power of the hand was comparable between the groups (Tables 2 and 3). Thereafter, there were no statistically significant differences between the groups in the recovery of the sensory or motor blockade.
The particular patient (group AX) with tachycardia and ST changes in the ECG was dissatisfied with the anesthetic technique. The others were quite satisfied (7 in group IC and 3 in group AX), satisfied (12 in group IC and 15 in group AX), or very satisfied (10 in group IC and 11 in group AX).
In the present study, the main finding was a slower onset of musculocutaneous nerve anesthesia with single-injection perivascular axillary block technique when compared with infraclavicular coracoid block in patients scheduled for arteriovenous fistula surgery. The number of patients having complete sensory block of musculocutaneous nerve (“no sensation” to pinprick) at 30- and 45-minute testing was almost twice that seen in group IC than group AX. However, at 45 and 60 minutes after injection of mepivacaine, we achieved similar surgical analgesia (“blunt” or “no sensation” to pinprick) on the lateral forearm with both techniques.
There are important differences in the neural anatomy in the axillary and infraclavicular region. In the infraclavicular area, the cords are lying very close to each other around the axillary artery, whereas in the axilla the terminal nerves are separated and variably located at greater distances from each other. The musculocutaneous and axillary nerves have already left the cords at the level of the coracoid process. Therefore, when anesthesia at the territories of these nerves is required, a single-injection technique by identifying only 1 motor response of a terminal nerve may be more applicable when using the infraclavicular coracoid approach than the axillary approach. In the current study using a single-injection method, faster achievement of block with the coracoid approach in comparison with the axillary approach and similar block at 60 minutes after the injection of mepivacaine support the idea of the proximal migration of mepivacaine when administered in the axilla.
An interesting observation in the present study was mild tachycardia with ST depression of the electrocardiogram in 2 of our axillary group patients 10 to 15 minutes after the administration of the total dose of the local anesthetic. The relatively late appearance of symptoms suggests that the reactions were caused by epinephrine absorbed from the injected solution. Similar complications have been reported before.6,7 In our study, the total dose of epinephrine was relatively large, 168 to 240 g (i.e., larger than suggested by Raj and coworkers8 as the maximum recommended dose of 1.5 g/kg/10 min). Intravascular injection of the local anesthetic solutions, a possible complication of both the axillary and the lateral infraclavicular approaches,4,9,10 did not occur in our patients. This raises the question of the risks and benefits of the use of epinephrinecontaining solutions in brachial plexus anesthesia.
The single-injection technique may shorten the duration of the block performance9 and lessen patient distress caused by needle punctures and muscle twitches. On the other hand, anesthesia of the cutaneous lateral nerves of the forearm and of the arm is inconsistently achieved with single-injection IC block techniques. In contrast to the conclusion by Rodrguez and coworkers11 of a low success rate by using single-injection infraclavicular coracoid block (i.e., surgical analgesia in on average 81% of the 7 tested nerve distribution areas), we observed surgical analgesia in 90% to 97% of the test territories of the ulnar, median radial, and musculocutaneous nerves. The difference may be because of the relatively short follow-up period (i.e., 20 minutes) in the study by Rodriguez and coworkers. In the present study, the maximum block was not achieved until 45 minutes, a finding typical when single- injection technique is used.1,2 In addition, a motor stimulation response of median nerve in single-stimulation infraclavicular coracoid approach to brachial plexus appears to be associated with good sensory block of the radial nerve, which may have enabled pain- free surgery also in the innervation area of that nerve.11 In fact, in lateral infraclavicular approaches, the initial motor response is often from the median nerve stimulation,12 and single injection of a large local anesthetic dose (volume) provides analgesia also of the ulnar and radial nerves.1 ‘Nearly all of our patients were very satisfied or satisfied with their regional anesthesia. Only one of our axillary group patients (i.e., the one with an epinephrine- induced acute cardiovascular episode) experienced the placement of the block as uncomfortable.
We conclude that a brachial plexus block with 333 to 475 mg of mepivacaine develops faster by a single-stimulation/injection technique using the infraclavicular coracoid than with the axillary approach, but both have a similar efficacy for surgery in patients scheduled for creation of an arteriovenous fistula of the forearm.
We are grateful to Pekka Tarkkila, M.D., Ph.D., for helpful comments and suggestions during the preparation of the manuscript.
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Tomi T. Niemi, M.D., Ph.D., Liisa Salmela, M.D., Ulla Aromaa, M.D., Ph.D., Reino Pyhi, M.D., Ph.D., and Per H. Rosenberg, M.D., Ph.D.
From the Department of Anesthesiology and Intensive Care Medicine, Helsinki University Hospital, Helsinki, Finland.
Accepted for publication September 21, 2006.
Supported by Helsinki University Hospital Research Grants (EVO).
Reprint requests: Tomi T. Niemi, M.D., Ph.D., Department of Anesthesiology and Intensive Care Medicine, Helsinki University Hospital, PO Box 340, FI-00029 HUS, Helsinki, Finland. E-mail: [email protected]
2007 by the American Society of Regional Anesthesia and Pain Medicine.
Copyright Churchill Livingstone Inc., Medical Publishers Jan/Feb 2007
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