Regional anesthesia has several reported advantages when compared with general anesthesia for patients undergoing upper limb trauma surgery, including improved perioperative analgesia,1 reduced opiate consumption,2 reduced postoperative nausea and vomiting (PONV),3 shorter postanesthesia care unit stay,3 and earlier hospital discharge.4,5
Nerve localization using ultrasound-guidance has been shown to improve success rates,6,7 decrease onset times,6–9 and reduce local anesthetic dose.10–12 Traditionally, local anesthetic volumes of up to and more than 40 mL have been used to perform axillary brachial plexus block.4,13,14 It is not known whether lower dose ultrasound-guided axillary block confers similarly reported advantages when compared with general anesthesia.
We hypothesized that low-dose ultrasound-guided axillary block using 20 mL of solution provides excellent anesthesia for and superior analgesia after upper limb trauma surgery when compared with general anesthesia. We conducted a prospective, randomized, observer-blinded study comparing ultrasound-guided axillary block to general anesthesia evaluating anesthetic and perioperative analgesic outcomes.
After ethical approval and written informed consent, patients scheduled for upper limb trauma surgery to the forearm or hand of <90 min expected duration were enrolled in the study. Patients were 18 yr or older and ASA physical status I, II, or III. Exclusion criteria included language barrier, contraindication to regional anesthesia, multiple injuries, intolerance to nonsteroidal antiinflammatory drugs, nonsteroidal antiinflammatory drug-sensitive asthma, chronic pain history, and pregnancy.
Patients were randomized using a computer-generated random number table. The general anesthesia group received standardized anesthesia, which included fentanyl 1 mg/kg and propofol 1–2 mg/kg. Anesthesia was maintained with oxygen/nitrous oxide and sevoflurane titrated to effect. Morphine was administered in 0.05 mg/kg aliquots at the attending anesthesiologists discretion to treat intraoperative pain.
A SonoSite Titan unit (SonoSite®, Bothwell, WA) with a 38 mm linear array 5–10 MHz transducer (L38) was used to identify the axillary brachial plexus in the ultrasound-guided axillary block group. With the operative arm abducted and externally rotated and the elbow flexed to 90°, the axilla was scanned to reveal the axillary vessels. Each nerve was identified individually. Nerve stimulation was not used to confirm needletip placement. The block solution consisted of 9.5 mL 2% lidocaine with 1:200,000 epinephrine and 9.5 mL 0.5% bupivacaine with clonidine 150 mg (1 mL).15,16
A single operator performed all ultrasound-guided axillary blocks. A Stimuplex A 50 mm needle (Stimuplex®, BBraun, Melsungen, Germany) was directed under ultrasound guidance toward each of the neural structures. The needle was moved to several points around each nerve to facilitate circumferential perineural local anesthetic spread. A total of 3–5 mL of local anesthetic solution was injected and observed to surround each nerve. A maximum of 20 mL of local anesthetic mixture was injected. Motor function was assessed using a modified Bromage Scale and sensory function was assessed using pinprick (25G hypodermic needle), soft touch (gauze), and cold (ethyl chloride spray). Motor and sensory modalities were assessed every 5 up to 30 min postblock. Surgical anesthesia was defined as a motor score of 2 or lower, with absent appreciation of cold and pinprick sensation in the territory of all four terminal branches. Failure of surgical anesthesia at 30 min was managed with either an ultrasound-guided “rescue” block at a site distal to the axilla or a general anesthesia at the patient’s discretion.
Both groups received 1 g acetaminophen and 75 mg diclofenac sodium IV during surgery. Intraoperative local anesthetic wound infiltration by the surgeon was permitted if it was their usual practice. Cyclizine 50 mg and ondansetron 4 mg were administered if patients received opiate analgesia during surgery. Anxiolysis was provided at the patient’s request with midazolam 2–4 mg, titrated to effect. In the recovery room, morphine was administered IV in 2 mg aliquots until satisfactory analgesia was achieved. On discharge, patients were prescribed diclofenac sodium 75 mg for 12 h and acetaminophen 1 g for 6 h to be taken regularly for 48 h after surgery and as required thereafter.
Primary Outcome Measure
The primary outcome measure was pain assessed with a 100 mm visual analog scale (0–100) immediately after surgery in either the recovery room or the operating room in the case of recovery room bypass.
Secondary Outcome Measures
The effectiveness of ultrasound-guided axillary block anesthesia was recorded, as was the need for supplemental block or conversion to general anesthesia. Postoperative pain was measured at 2, 6, 24, 48 h, and at 7 days after surgery using a Verbal Rating Scale (0–10). The anesthesia induction time was defined as the interval in seconds from the patient lying on the operating table (all anesthesia was induced in the operating room) to the time surgical anesthesia was achieved (including performing and assessing ultrasound-guided axillary block or acquiring adequate depth of general anesthesia). Other variables recorded included, the duration of surgery (minutes); morphine consumption (mg); PONV on a four-point scale (0 = No PONV, 1 = Mild; 2 = Moderate; 3 = Severe); the time to first request for supplemental analgesia (minutes); the ability to bypass the recovery room17; the duration of recovery room stay (min); the total operating room transit time (minutes from start of anesthesia to discharge from the operating room complex); and the time to suitability for hospital discharge (min).18
Data were analyzed on an intention-to-treat basis using EpiInfo™ 2002 (Centers for Disease Control and Prevention) statistics software. Normally distributed data were analyzed using the unpaired Student t or analysis of variance as appropriate. Nonnormally distributed data were analyzed using the Mann–Whitney/ Wilcoxon two-sample test. Differences in proportions were compared by Yates χ2 test. Statistical significance was considered at P < 0.05. To detect a 50% difference in visual analog scale pain scores with a Type I error rate of 0.01 and a power of 0.80, it was estimated that 60 patients would be required. We planned an interim analysis at 50% recruitment (30 patients).
The study was terminated at interim analysis (n = 30). No patients meeting entry criteria were excluded from data analysis and none was lost to follow-up. The groups’ baseline characteristics were similar (Table 1). One patient required radial nerve block at the elbow because of incomplete block at 20 min. There were no conversions to general anesthesia. Three ultrasound-guided axillary block patients requested sedation, each received 4 mg midazolam.
Pain scores were significantly lower in the ultrasound-guided axillary block group in the recovery room, at 2 and 6 h postoperatively. There were no significant differences in pain scores at 24, 48 h, or at 7 days (Figs. 1a and b). The ultrasound-guided axillary block group had significantly higher recovery room bypass scores, longer time to first analgesia, shorter recovery room stay, shorter total operating room transit time, and achieved hospital discharge criteria sooner (Table 2). Morphine consumption was higher in the general anesthesia group at all time points (Fig. 2). There were no differences between PONV scores in either group (general anesthesia 0 0/2; and ultrasound-guided axillary block 0 median [range] at all time points P = 0.06). Only one patient in the general anesthesia group required antiemetic rescue in the recovery room.
Four patients (two in either group) violated the postoperative analgesia protocol. Three patients took analgesics as required rather than on a regular basis during the first 48 h after surgery. One patient added tramadol to her analgesia regimen. Only two patients (one in either group) required supplementation of analgesia with codeine phosphate 16 mg for 6 h on the first postoperative day. There were no adverse clinical incidents relating to the conduct of general or regional anesthesia.
Our data demonstrated improved perioperative analgesia, reduced opiate consumption, recovery room bypass, and earlier achievement of hospital discharge criteria with the use of regional anesthesia. This compares favorably with previous reports.1–4 Low injectate dose did not alter the anesthetic or analgesic efficacy of axillary brachial plexus block. The potential for dose reduction with ultrasound guidance is promising. Systemic local anesthetic toxicity is still frequently reported in the anesthesia literature.19,20 Lipid rescue therapy has been associated with improved outcomes after local anesthetic toxicity.21,22 The systemic toxicity of local anesthetics is dose dependent. Reducing the dose of drug administered may contribute to improved safety of regional anesthesia.
We acknowledge that the study has limitations which may limit the generalizability of the data, including small patient numbers (n = 30) and that a single anesthesiologist performed all ultrasound-guided axillary blocks. The study may be criticized as measuring the obvious. Patients with an insensate limb have no pain sensation for the duration of the block. It is therefore not surprising to report superior analgesia when compared with patients who received general anesthesia and parenteral analgesia. Importantly, however, our study demonstrated that previously reported benefits of regional anesthesia are maintained despite the use of low-dose local anesthetic mixture.
In conclusion, when compared with general anesthesia, low-dose ultrasound-guided axillary block provided excellent anesthesia, superior analgesia, reduced opiate consumption, facilitated recovery room bypass, and earlier hospital discharge readiness in patients undergoing upper limb surgery.
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