ORIGINAL ARTICLE Combined Versus Sequential Injection of Mepivacaine and Ropivacaine for Supraclavicular Nerve Blocks Dmitry Roberman, DO,* Harendra Arora, MD,Þ Daniel I. Sessler, MD,þ§ Michael Ritchey, MD,|| Jing You, MS,¶ and Priya Kumar, MDÞ Regional anesthetic techniques and peripheral nerve blocks Background: An ideal local anesthetic with rapid onset and pro- are especially favored for surgeries on the extremities.1Y4 For longed duration has yet to be developed. Clinicians use mixtures of local example, supraclavicular brachial plexus blocks are commonly anesthetics in an attempt to combine their advantages. We tested the performed for upper-extremity surgeries. hypothesis that sequential supraclavicular injection of 1.5% mepivacaine Both rapid onset of the block and prolonged postoperative followed 90 secs later by 0.5% ropivacaine speeds onset of sensory block analgesia are desired characteristics of regional anesthesia. The and prolongs duration of analgesia compared with simultaneous injection choice of local anesthetics or combinations thereof can greatly of the same 2 local anesthetics. influence the effectiveness of the block, onset time, duration of Methods: We enrolled 103 patients undergoing surgery suitable for postoperative analgesia, need for opioid use, and patient satis- supraclavicular anesthesia. The primary outcome was time to 4-nerve faction.2 Mepivacaine and ropivacaine are commonly used in sensory block onset in each of the 4 major nerve distributions: median, peripheral nerve blocks, their drawbacks being a short dura- ulnar, radial, and musculocutaneous. Secondary outcomes included tion with 1.5% mepivacaine5Y7 and a delayed onset with 0.5% time to onset of first sensory block, time to complete motor block, du- ropivacaine.8 A higher concentration of a local anesthetic such ration of analgesia, pain scores at rest and with movement, and total as ropivacaine 0.75% has a quicker onset, but at the cost of a opioid consumption. Outcomes were compared using the Kaplan-Meier greater potential toxicity.9 analysis with the log-rank test or the analysis of variance, as appropriate. An ideal local anesthetic with high potency, low toxicity, Results: Times to 4-nerve sensory block onset were not different be- rapid onset, and prolonged duration does not exist yet. Investiga- tween sequential and combined anesthetic administration. The time tors have therefore tried mixtures of local anesthetics in an at- to complete motor block onset was faster in the combined group as tempt to combine their advantagesVwith conflicting results.10Y12 compared with the sequential. There were not significant differences When combinations of anesthetics are used, the drugs are usually between the 2 randomized groups in other secondary outcomes, such as mixed and injected simultaneously. For example, Moore et al13 the time to onset of first sensory block, the duration of analgesia, the showed that mixing local anesthetics is safe in humans and that pain scores at rest or with movement, or the total opioid consumption. the combination can have desirable properties of both medica- Conclusions: Sequential injection of 1.5% mepivacaine followed tions without producing toxicity. 90 secs later by 0.5% ropivacaine provides no advantage compared with A potential problem is that mixing drugs dilutes the effects simultaneous injection of the same doses. of each. Thus, a mixture of a rapid-onset drug such as mepiva- (Reg Anesth Pain Med 2011;36: 145Y150) caine with a long-acting one such as ropivacaine may well result in slower onset than mepivacaine alone and shorter duration of action than ropivacaine alone. In contrast, sequential adminis- he choice of anesthetic technique combined with a suit- tration of the same amounts of the same drugs may preserve the T able plan for postoperative analgesia can facilitate early desirable features of each. We therefore tested the hypothesis discharge, improve patient comfort, and increase overall satis- that sequential supraclavicular injection of 1.5% mepivacaine faction. Patients having painful procedures under general anes- followed 90 secs later by 0.5% ropivacaine provides a quicker thesia have a 2- to 5-fold greater risk of unplanned overnight onset and a longer duration of analgesia than an equidose com- admissions compared with those having regional anesthesia.1 bination of the 2 local anesthetics. From the *Department of Anesthesiology, Drexel University College of MATERIALS AND METHODS Medicine, Philadelphia, PA; †Department of Anesthesiology, University of North Carolina, Chapel Hill, North Carolina; ‡Department of Outcomes Re- The study was approved by the institutional review board search, Cleveland Clinic, Cleveland, OH; §Department of Anesthesiology, of the Cleveland Clinic with the plan to enroll 116 patients, McMaster University, Hamilton, Ontario, Canada; Departments of ||General aged 18 to 70 years, who were scheduled to undergo an upper- Anesthesiology, and ¶Quantitative Health Sciences and Outcomes Research, Cleveland Clinic, Cleveland, OH. extremity procedure suitable for supraclavicular anesthesia. Accepted for publication November 26, 2010. These procedures were expected to be associated with consid- Address correspondence to: Priya Kumar, MD, University of North Carolina, erable postoperative pain. Patients were excluded from the Department of Anesthesiology, University of North Carolina, N2201 study if they had a history of coagulopathy, infection at the UNC Hospitals, Campus Box 7010, Chapel Hill, NC 27599-7010 (e-mail: [email protected], on the World Wide Web: www.OR.org). needle insertion site, severe chronic obstructive pulmonary dis- Received from the Departments of Outcomes Research, General ease, neuropathy, pneumothorax, contralateral diaphragmatic Anesthesiology, and Quantitative Health Sciences, Cleveland Clinic; paralysis, routine opioid use, or inability to obtain adequate ul- Department of Anesthesiology, University of North Carolina; and the trasound images of the supraclavicular area or were pregnant Department of Anesthesiology, McMaster University. This study was supported entirely by internal funds. None of the authors at the time. have a personal financial interest in this research. Copyright * 2011 by American Society of Regional Anesthesia and Pain Protocol Medicine ISSN: 1098-7339 Randomization was generated by the plan procedure in DOI: 10.1097/AAP.0b013e31820d4235 SAS statistical software (SAS Institute, Inc, Cary, NC), within Regional Anesthesia and Pain Medicine & Volume 36, Number 2, March-April 2011 145 Copyright © 2011 American Society of Regional Anesthesia and Pain Medicine. Unauthorized reproduction of this article is prohibited. Roberman et al Regional Anesthesia and Pain Medicine & Volume 36, Number 2, March-April 2011 randomly sized blocks and was administered via sealed se- time was determined, the assessment frequency was at 1-min quentially numbered opaque envelopes. Envelopes were opened intervals until the development of 4-nerve sensory block in each just before blocks were performed by an attending anesthesi- of the 4 distributions mentioned above. Motor block was as- ologist. Patients were assigned to either (1) combined group- sessed by evaluation of motor strength in the muscle groups sup- ropivacaine and mepivacaine mixture: 1:1 volume mixture of plied by the above nerves, on a scale used by Marhofer et al,15 1.5% mepivacaine and 0.5% ropivacaine in 2 syringes (labeled where 1 = motor paralysis, 2 = decreased motor function, and 1 and 2) with 15 mL in each (total, 30 mL) injected in immedi- 3 = normal motor function. ate sequence; or (2) sequential groupVmepivacaine followed The severity of postoperative pain was assessed by an ob- by ropivacaine: syringe 1 containing 15 mL of 1.5% mepiva- server blinded to treatment using a 0- to 10-point verbal response caine, syringe 2 containing 15 mL of 0.5% ropivacaine (total, score (VRS) at 10-min intervals for 30 mins in the postanesthesia 30 mL); syringe 2 was injected with a 90-sec delay after injec- care unit (PACU). Patients reporting pain scores greater than 2 tion of syringe 1. were administered intravenous morphine (1Y2 mg) every 5 mins We used a previously described ultrasound-guided su- until they were comfortable. After discharge from the PACU, praclavicular approach.14 All blocks were performed under supplemental analgesia for inpatients consisted of acetaminophen the supervision of attending anesthesiologists proficient in 325 mg with oxycodone 5 mg orally every 4 hrs as needed for ultrasound-guided regional anesthesia. The patient was posi- pain for VRS greater than 4, administered by the nurse caring tioned supine, with the head turned 45 degrees to the contralat- for the patient. Pain unrelieved by oral medication (VRS persis- eral side after the standard sterile prep and drape. An ultrasound tently 94) was treated with intravenous morphine. Outpatients probe was placed in the coronal oblique plane in the supracla- received a prescription for oral acetaminophen with oxycodone. vicular fossa. The subclavian artery was identified, with the bra- Patients were instructed to delay administration of analgesics chial plexus located immediately superficial and lateral to it, and until they experienced pain rather than taking oral analgesics the hyperechoic rib and pleura immediately deep to the artery. prophylactically. The duration of analgesia was measured as the A 5-cm-long, 22-gauge insulated needle (Stimuplex; B time from the onset of 4-nerve sensory block until the first re-