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REGIONAL ANESTHESIA

The Effect of Motor Activity on the Onset and Progression of Brachial Plexus Block with Bupivacaine: A Randomized Prospective Study in Patients Undergoing Arthroscopic Shoulder Surgery

Kenneth E. Langen, MD^*, Kenneth D. Candido, MD^*, Michael King, MD^*, Guido Marra, MD, and Alon P. Winnie, MD

From the Departments of *Anesthesiology and Orthopaedic Surgery, Loyola University Medical Center, Maywood, Illnois. Department of Anesthesiology, Northwestern University Medical Center/Feinberg School of Medicine, Chicago, IL.

Address correspondence and reprint requests to Kenneth D. Candido, MD, Professor of Anesthesiology, Loyola University Medical Center, 2160 South First Ave., Maywood, IL 60153. Address e-mail to kdcandido{at}yahoo.com.

	Abstract

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BACKGROUND: A decreased latency of onset of neural blockade has been noted when muscular exercise of the hand was performed after supraclavicular brachial plexus block using lidocaine. In this observational study, we examined the effect of repetitive muscle contraction of the hand on the speed of onset of interscalene brachial plexus block (ISB) using bupivacaine.

METHODS: Forty patients were enrolled, all of whom received an ISB as one component of their anesthetic management for elective arthroscopic shoulder surgery. Patients were asked either to rest their arms after the performance of the ISB (nonexercise group) or to perform a repetitive hand exercise for 5 min (exercise group). Bilateral hand grip strength and tolerance to transcutaneous electrical stimulation were used to quantify the degree of motor and sensory blockade.

RESULTS: Patients in the exercise group had a statistically significant lower tolerance to transcutaneous electrical stimulation 20 min after completion of the block (P < 0.05).

CONCLUSIONS: Our results imply that attempting to use a frequency-dependent conduction block with repetitive motor activity as a clinical adjuvant to brachial plexus block with bupivacaine is without merit.

	Introduction

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Various methods of decreasing the latency of onset of neural blockade have been investigated, with limited success. These have included warming the local anesthetic,1–3 diluting the local anesthetic4 as well as adding bicarbonate,5,6 fentanyl,7 dexamethasone,8,9 magnesium,10 and clonidine.11 Okasha et al.12 have shown that repetitive muscle contraction of the hand reduced the latency of onset of supraclavicular brachial plexus block when lidocaine is used as the local anesthetic. They hypothesized that this was accomplished by harnessing a frequency-dependent blockade of sodium channels.

A major disadvantage of highly lipid-soluble and protein-bound local anesthetics such as bupivacaine when used for peripheral nerve block is the prolonged latency of onset of sensory and motor block. Nevertheless, these pharmacological properties are also those responsible for extending the duration of action of these drugs, making them ideally suited for use in the management of postoperative pain. It would be desirable if a simple intervention such as repetitive hand exercise could reduce the latency of onset of bupivacaine, a local anesthetic having a slow onset. We performed this study to evaluate the efficacy of repetitive hand exercise in reducing the latency of onset of interscalene brachial plexus block (ISB) using bupivacaine 0.5% with epinephrine.

	METHODS

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After IRB approval, 40 consenting male and female ASA physical status I-III patients between the ages of 18 and 65 yr were enrolled in this study. All patients were scheduled to receive an ISB as one component of their anesthetic management for elective arthroscopic shoulder surgery. Patients were excluded from the study if they had coagulation abnormality, Body Mass Index more than 40 kg/m², preexisting neurologic deficit, severe obstructive pulmonary disease, continuing acute pain, implanted electrical device such as a pacemaker, habituation to chronic opioid analgesics, or the inability to cooperate with muscular exercise or measurement of motor or sensory blockade as described below.

Patients were randomly assigned into one of two groups using a computer-generated randomization table. Patients in Group I (nonexercise group), were asked to rest their upper extremities immediately after the performance of the ISB. Patients in Group II (exercise group), were instructed to rapidly and forcefully open and close both of their hands for 5 min beginning immediately after the completion of the ISB.

Patients were placed in the supine position and peripheral IV access was secured. Hemodynamic monitors were applied including a pulse oximeter, noninvasive blood pressure cuff, and electrocardiogram. After documenting initial vital signs, baseline bilateral grip strength and tolerance to transcutaneous electrical stimulation (TES) of the arm to be blocked were measured and recorded. Patients were sedated with midazolam titrated to effect up to 4 mg/70 kg to ensure a comfortable yet cooperative and conversant state. All ISBs were performed using a 22 gauge, 2" Stimuplex® needle with nerve stimulator guidance using Winnie's technique.13 The patients were positioned with the head turned away from the side to be blocked. After aseptic skin preparation, the Stimuplex needle was inserted into the interscalene groove at the level of the cricoid cartilage (C6). It was directed slightly mesiad, caudad, and dorsad into the brachial plexus sheath at the level of the roots of the plexus. This was accomplished using peripheral nerve stimulator guidance starting with a current of 1.0 mA, a frequency of 2 Hz, and a pulse width of 0.1 ms. The minimum current intensity needed to cause an evoked motor response (EMR) was recorded. Acceptable EMRs included pectoralis major muscle contraction (C5–7); biceps and brachialis contraction with forearm flexion (C5–7); deltoid contraction with abduction of the arm (C5–6); triceps contraction with arm extension (C5–T1). Unacceptable EMRs included serratus anterior contraction (C5–7); diaphragmatic contraction (C5); rhomboid major or minor contraction (C5); supraspinatus or infraspinatus contraction (C5, C6); teres major or subscapularis muscle contraction (C5, C6); and latissimus dorsi contraction (C6–8). Forty milliliters of 0.5% bupivacaine with epinephrine 1:200,000 (5 µg/mL) was injected with frequent, intermittent aspiration for blood or cerebrospinal fluid. Completion of the ISB was defined as the time at which the entire volume of local anesthetic had been completely injected.

Immediately after injection of the local anesthetic, all patients were placed in a head-up tilt position. Patients in Group II were asked to rapidly and forcefully open and close both hands for 5 min at the rate of one cycle per second. Patients in Group I were asked to maintain their arms motionless. Bilateral hand grip strength and tolerance to TES were used to quantify the degree of motor and sensory blockade, respectively. Measurements were made at baseline and at 5-min intervals after completion of the ISB over a 20-min observation period. Hand grip strength was measured by asking subjects to grip a hand dynamometer (Jamar®, Duluth, MN) and recording the maximal force the patient could exert.

TES has been used in previous studies in volunteers to quantify pain thresholds after both femoral nerve blocks as well as spinal anesthetics.14–16 In the present study, electrodes were placed on the skin 2 cm apart on the lateral aspect of the ipsilateral upper arm at the midhumeral level. Using an EZStim Model ES 400® (Life-Tech, Houston, TX) nerve stimulator, TES was initially delivered at 5 mA in a 50 Hz square wave pattern and the output was increased in 5 mA increments until each subject described discomfort or until a maximum of 60 mA was attained. The current delivered which caused mild discomfort (verbal pain score = 2 on a 10-point scale), as verbalized by the individual patient, was recorded as the TES threshold. If the patient denied any discomfort at an output of 60 mA, 65 mA was recorded as the TES threshold. For each subsequent measurement of tolerance to TES, the initial output on the nerve stimulator was set at 5 mA below the threshold observed in that patient on the previous measurement.

The sample size for this study was estimated based upon a difference of 3 min in the onset of pinprick sensory analgesia between the exercise and nonexercise groups based on the findings of Okasha et al.12 Assuming a group standard deviation of 3 min, a sample of 17 subjects per group achieves 81% power to detect a significant difference ([alpha] = 0.05) using the Mann-Whitney U-test. In the absence of historical data regarding the use of TES to measure the onset of ISB, an additional three subjects were added to each group.

Age, height, weight, Body Mass Index, and current threshold for EMRs were compared between groups using the Mann-Whitney U-test. Gender and ASA physical status were compared using the ² statistic. TES threshold (mA) and grip strength (lbs) of the blocked arm as well as the unblocked arm were compared between groups using two-way ANOVA for repeated measures. Post hoc comparisons were made using Bonnferroni corrected t-tests. The median time to reach a TES threshold of 60 mA was compared by constructing Kaplan-Meier plots and the Log Rank test. A P < 0.05 was required to reject the null hypothesis.

	RESULTS

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There were no significant differences in the demographics between groups (Table 1). One patient was excluded in Group II because the block was abandoned secondary to patient anxiety and discomfort during the block procedure. No local anesthetic solution was injected, and therefore no assessment of success or failure could be made. An additional patient was recruited for the study.

Patients in Group II had a statistically significant lower tolerance to TES 20 min after completion of the block (Fig. 1). Grip strength of both groups decreased to approximately 40% of baseline 20 min after completion of the block. There was no statistically significant difference in the percent baseline grip strength between the two groups at any time period (Fig. 2). Grip strength of the nonblocked hand remained approximately 100% of baseline strength (Fig. 3).

View larger version (16K): [in this window] [in a new window]   Figure 1. Tolerance to TES following ISB. TES = Transcutaneous electrical stimulation; ISB = Interscalene brachial plexus block. *P < 0.05 comparing exercise and nonexercise groups at 20 min.

View larger version (16K): [in this window] [in a new window]   Figure 2. Grip strength in the blocked hand over the 20-min observation period. There were no significant differences between groups.

View larger version (16K): [in this window] [in a new window]   Figure 3. Grip strength in the nonblocked hand over the 20-min observation period. There were no significant differences between groups of change from baseline.

	DISCUSSION

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The present study indicates that repetitive muscle contraction of the hand does not reduce the onset time of the sensory block of ISB using bupivacaine as the local anesthetic solution. These results contradict those of Okasha et al.,12 who demonstrated that opening and closing of the hand reduced the latency of onset of both sensory and motor brachial plexus block, when lidocaine is used as the local anesthetic. In that study, 5 min of repetitive muscle contraction of the hand resulted in a decrease in the onset of sensory block by 60% (from 14.25 to 5.65 min). Also shortened were latencies of onset of motor block (19.9–10.1 min—49.2% reduction), and complete motor paralysis (25.9–13 min—49.7% reduction). The authors hypothesized that this reduction in latency was accomplished by harnessing a frequency-dependent blockade of sodium channels. The susceptibility of sodium channels in nerves to amino-amide local anesthetics has been shown to increase with repeated or repetitive stimulation.17 This phenomenon is termed "frequency-dependent blockade."

Frequency-dependent block occurs at rapid rates of nerve stimulation. At high frequencies of stimulation, the time interval between nerve impulses is insufficient for local anesthetic molecules to "unbind," leaving a fraction of sodium channels blocked when the next impulse arrives. The conditions that must be met for frequency-dependent block to occur include a weak concentration of local anesthetic (<Cm) (where Cm = the lowest concentration of local anesthetic that blocks impulse conduction within a specified time)18 plus a train of rapidly repetitive stimuli. Frequency-dependent block has been proposed as one mechanism underlying differential spinal subarachnoid block, wherein there is a distinct separation of sympathetic, sensory, and motor blockade noted from cephalad to caudad as the concentration of local anesthetic diminishes to below Cm as it moves upward in the spinal fluid.19 When compared to lidocaine, bupivacaine exhibits greater frequency-dependent blockade at lower stimulation frequencies; this might increase the onset and time course of recovery.17 If a frequency-dependent block of motor or sensory nerves could be accomplished with repetitive muscular activity, the effect of this activity would be clinically more useful with bupivacaine, which has a slow onset, compared to lidocaine.20,21

Courtney et al. demonstrated that drugs of low lipid solubility, such as procaine, were successful in differentially blocking sympathetic fibers without blocking sensory fibers in a spinal model, and postulated that more highly lipid soluble drugs, such as bupivacaine, require more rapid rates of repetitive stimuli to cause frequency-dependent blockade.17 If such is the case, then the 5 min of repetitive stimuli in our study (one cycle per second) should have sufficed to cause frequency-dependent block that is clinically apparent.

The onset of conduction block in isolated nerves depends not only on the physicochemical properties of the drug, especially its pKa, but also on the concentration and total dosage of drug used. One possible explanation for the delayed onset of sensory blockade which we observed in the exercise group is a relative change in the local chemical milieu resulting from repetitive motor activity. Repetitive fist clenching increases the metabolic demand of the upper extremity and produces lactic acid.22–25 The resultant increase in the systemic concentration of hydrogen ions, altering the concentration of ionized versus unionized local anesthetic, may be responsible for slowing the onset of the block.

One limitation of the present study is the use of an ISB technique, versus the supraclavicular technique used by Okasha et al.12 Although ISB is also a "supraclavicular" technique, our block occurred at a root level, versus a trunk level, and this might have influenced our results, since the local anesthetic injected in proximity to three trunks (instead of five roots) are blocking the plexus in its most compact arrangement from origin to destination.

In conclusion, repetitive muscular activity does not decrease the onset of sensory or motor blockade after ISB with bupivacaine. Our results contradict the findings of Okasha et al., and indicate that repetitive motor activity to shorten the onset of anesthesia after an interscalene brachial block by adding a frequency-dependent block is without clinical merit.

	ACKNOWLEDGMENTS

 
Robert McCarthy, Pharm D, Northwestern University/Feinberg School of Medicine, 251 East Huron St., Chicago IL, 60611. Dr. McCarthy provided the statistical analysis for this project.

	Footnotes

 
Accepted for publication October 5, 2007.

	REFERENCES

Top Abstract Introduction METHODS RESULTS DISCUSSION REFERENCES

 

1. Chilvers CR. Warm local anaesthetic—-effect on latency of onset of axillary brachialplexus block. Anaesth Intensive Care 1993;21:795–8[Web of Science][Medline]
2. Heath PJ, Brownlie GS, Herrick MJ. Latency of brachial plexus block. The effect on onset time of warming local anaesthetic solutions. Anaesthesia 1990;45:297–301[Web of Science][Medline]
3. Arai YC, Ueda W, Takimoto E, Manabe M. The influence of hyperbaric bupivacaine temperature on the spread of spinal anesthesia. Anesth Analg 2006;102:272–5[Abstract/Free Full Text]
4. Krenn H, Deusch E, Balogh B, Jellinek H, Oczenski W, Plainer-Zochling E, Fitzgerald RD. Increasing the injection volume by dilution improves the onset of motor blockade, but not sensory blockade of ropivacaine for brachial plexus block. Eur J Anaesthesiol 2003;20:21–5[Web of Science][Medline]
5. Candido KD, Winnie AP, Covino BG, Raza SM, Vasireddy AR, Masters RW. Addition of bicarbonate to plain bupivacaine does not significantly alter the onset or duration of plexus anesthesia. Reg Anesth 1995;20:133–8[Web of Science][Medline]
6. Bedder MD, Kozody R, Craig DB. Comparison of bupivacaine and alkalinized bupivacaine in brachial plexus anesthesia. Anesth Analg 1988;67:48–52[Abstract/Free Full Text]
7. Cherng CH, Yang CP, Wong CS. Epidural fentanyl speeds the onset of sensory and motor blocks during epidural ropivacaine anesthesia. Anesth Analg 2005;101:1834–7[Abstract/Free Full Text]
8. Shrestha BR, Maharjan SK, Tabedar S. Supraclavicular brachial plexus block with and without dexamethasone—a comparative study. Kathmandu Univ Med J (KUMJ) 2003;1:158–60[Medline]
9. Movafegh A, Razazian M, Hajimaohamadi F, Meysamie A. Dexamethasone added to lidocaine prolongs axillary brachial plexus blockade. Anesth Analg 2006;102:263–7[Abstract/Free Full Text]
10. Ozalevli M, Cetin TO, Unlugenc H, Guler T, Isik G. The effect of adding intrathecal magnesium sulphate to bupivacaine-fentanyl spinal anaesthesia. Acta Anaesthesiol Scand 2005;49:1514–9[Web of Science][Medline]
11. Iohom G, Machmachi A, Diarra DP, Khatouf M, Boileau S, Dap F, Boini S, Mertes PM, Bouaziz H. The effects of clonidine added to mepivacaine for paronychia surgery under axillary brachial plexus block. Anesth Analg 2005;100:1179–83[Abstract/Free Full Text]
12. Okasha AS, el-Attar AM, Soliman HL. Enhanced brachial plexus blockade. Effect of pain and muscular exercises on the efficiency of brachial plexus blockade. Anaesthesia 1988;43:327–9[Web of Science][Medline]
13. Winnie AP. Interscalene brachial plexus block. Anesth Analg 1970;49:455–66[Free Full Text]
14. Salinas FV, Neal JM, Sueda LA. Prospective comparison of continuous femoral nerve block with nonstimulating catheter placement versus stimulating catheter-guided perineural placement in volunteers. Reg Anesth Pain Med 2004;29:212–20[Web of Science][Medline]
15. Chiu AA, Liu S, Carpenter RL, Kasman GS, Pollock JE, Neal JM. The effects of epinephrine on lidocaine spinal anesthesia: a cross-over study. Anesth Analg 1995;80:735–9[Abstract]
16. Laitinen LV, Eriksson AT. Electrical stimulation in the measurement of cutaneous sensibility. Pain 1985;22:139–50[Web of Science][Medline]
17. Courtney KR, Kendig JJ, Cohen EN. Frequency-dependent conduction block: the role of nerve impulse pattern in local anesthetic potency. Anesthesiology 1978;48:111–7[Web of Science][Medline]
18. Local anesthetics. DeJong R, ed. St. Louis: Mosby, 1994:66
19. Brull SJ, Green NN. Time courses of zones of differential sensory blockade during spinal anesthesia with hyperbaric tetracaine or bupivacaine. Anesth Analg 1989;69:343–7
20. Starmer CF: Theoretical characterization of ion channel blockade. Competitive binding to periodically accessible receptors. Biophys J 1987;52:405–12[Web of Science][Medline]
21. Fink BR, Cairns AM. Differential use-dependent (frequency-dependent) effects in single mammalian axons: data and clinical considerations. Anesthesiology 1987;67:477–84[Web of Science][Medline]
22. Catcheside PG, Scroop GC. Lactate kinetics in resting and exercising forearms during moderate-intensity supine leg exercises. J Appl Physiol 1993;74:435–43[Abstract/Free Full Text]
23. Hughson RL, Shoemaker JK, Tschakovsky ME, Kowalchuk JM. Dependence of muscle VO₂ on blood flow dynamics at onset of forearm exercise. J Appl Physiol 1996;81:1619–26[Abstract/Free Full Text]
24. Baker J, Brown E, Hill G, Phillips G, Williams R, Davies B: Handgrip contribution to lactate production and leg power during high-intensity exercise. Med Sci Sports Exerc 2002;34:1037–40
25. Tschakovsky ME, Hughson RL. Rapid blunting of sympathetic vasoconstriction in the human forearm at the onset of exercise. J Appl Physiol 2003;94:1785–92[Abstract/Free Full Text]

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This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a colleague Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Langen, K. E. Articles by Winnie, A. P. Search for Related Content PubMed PubMed Citation Articles by Langen, K. E. Articles by Winnie, A. P. Related Collections Anesthetic Techniques Regional Anesthesia Pharmacology