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Does the interscalene block require paresthesia?
Letters to the Editor cobrachialis muscle and the short head of the biceps on the medial aspect of the upper extremity at the distal insertion of the pectoralis major tendon, where it innervates the biceps, the coracobrachialis, and most of the brachialis (3). Finally, the teres major and the lower portion of sttbscapularis are innervated by the lower subscapular nerve, which may be approached by inserting a needle at the medial scapular border at the level of the scapular spine. The needle is advanced in a posteromedial direction, hugging the undersurface of the scapula, until internal rotation of the shoulder occurs in response to electrical stimulation (4). This technique produces approximately 6 months of spasticity reduction and may be repeated if hypertonicity recurs.
387
tained from the anesthetized limb. For this reason, we performed a second experiment, in which a special solution was prepared by dissolving carmine in gelatin, as described by Tanyola~ (7). In this experiment, the colored solution in the nerve t r u n k was demonstrated histopathologically; the macroscopic results were the same as in the first experiment. In these experiments, distribution of a solution to the surrounding tissues and to the nerve trunks during IVRA has been demonstrated in a m a n n e r different from the above-mentioned methods. Additional aspects of the mechanism of IVRA might be elucidated by further neurophysiologic studies in which a carmine-dyed local anesthetic agent prepared in the same m a n n e r as the carmine-dyed saline solution is administered.
Paul G. Loubser, M . D .
H/ilya (~elebi, M.D. Cengiz Oktem, M.D. Berrin Gfinaydin, M.D.
hzstittttefor Rehabilitation and Research Department of Anesthesiology Baylor Collegeof Medicine Houston, Texas
Department of Anaesthesiology and Reanimation Gazi UniversitySchool of Medicine Ankara, Turkey
References 1. Loubser PG. Spasticity associated with spinal cord injury. In: Narayan RK, Wilberger JE, Povlishock 31", eds. Neurotrauma. New York, McGraw-Hill, 1996: 1245-1258. 2. Botte MJ, Keenan ME. Percutaneous phenol blocks of the pectoralis major muscle to treat spastic deformities. J Hand Surg [Am] 1988: 13: 147-149. 3. Glenn MB. Nerve blocks, In: Glenn MB, Whyte J, eds. Practical management of spasticity in children and adults. Philadelphia, Lea & Febiger, 1990: 227-258. 4. Hecht JS. Subscapular nerve block in the painful hemiplegic shoulder. Arch Phys Med Rehabil 1992: 73: 1036-1039. Accepted for publication November 26, 1996.
A Different Approach in Demonstrating the Mechanism of Intravenous Regional Anesthesia To the Editor: The various clinical and experimental investigational methods for elucidation of the mode of action of intravenous regional anesthesia (IVRA) can be divided into three groups, namely radiographic, radioisotopic, and neurophysiologic studies (1-3). The essential mode of the anesthetic agent in IVRA (Bier block) involves direct block of nerve endings near the injection site initially and profound block of main nerve trunks later (4-6). We found that the distribution of a solution that might fill the vascular bed proceeds in a distal to proximal direction by performing IVRA with carmine-dyed saline in two mongrel dogs. In the first experiment, the tissues surounding the limb were dyed, and the nerve sample turned pink, as could easily be seen macroscopically. Since the carmine dye disappeared during fixation, we did not obtain the expected result. However, vactiolization was demonstrated in the nerve preparations ob-
References 1. Fleming SA, Vegia-Pires JA, McCutcheon RM, Emanuel CI. A demonstration of the site of action of intravenous lignocaine. Can J Anaesth 1966: 13: 21-27. 2. Corer C, Robin GC. Experimental studies on IVRA using radioactive lignocaine. Acta Anaesthesiol Scand Suppl 1969: 36: 127. 3. Miles DW, James J, Clarke DE, Witham JG. Site of action of intravenous regional anaesthesia. J Neurol Neurosurg Psychiatry 1964: 27: 574-576. 4. Raj PP, Garcia CE, Burleson JW, Jenkins MT. The site of IVRA. Anesth Analg 1972: 51: 776. 5. Lillie PE, Glynn CJ, Fenwick DG. Site of action of IVRA. Anesthesiology 1984:61: 507-510. 6. Rosenberg PH. IVRA: Nerve block by multiple mechanisms. Reg Anesth 1993: 18: 1-5. 7. Tanyola~ A. Morpholgische Untersuchungen fiber den Lappchenbau und Blutkrelslauf der Leber der Haussaugetiere. Ankara Oniv Vet Fak Dergisi 1972: XIX: 4: 1--445. Accepted for publication November 30, 1996.
Does the Interscalene Block Require Paresthesia? To the Editor: We would like to report a modification of the commonly used technique of interscalene block. The current recommendation is to obtain a paresthesia below the shoulder for a successful block; the operator has to "walk" the needle if the transverse process of C6 has been contacted until a parasthesia is obtained, (1,2). In our experience (over 25 years), the satisfactory block can be achieved without seeking a paresthesia. Having inserted the needle, as usually recommended (1,2), between the antenor and medial scalene muscles at the
388
Regional Anesthesia Vol. 22 No. 4 July-August 1997
level of the cricoid cartilage immediately behind the external jugular vein, we direct tire needle toward the transverse process of C6, which is readily palpable in normal individuals. We deliberately try not to elicit paresthesias. On contact with the transverse process (usually not deeper than 2 cm), the needle is aspirated in four quadrants and, provided one does not meet a *rubbery" resistance, the entire volume of anesthetic (usually 30 mL) is injected. The best predictors of success are the depth of needle insertion and the ease of injection (as with any other interfascial injection). We avoid deep needle insertion because of the possibility of missing the transverse process and contacting the vertebral body instead. Also, the risk of neuraxial injection is higher with deep needle insertion. Directing the needle toward the transverse process and a b o n y contact at shallow depth are both required for proper needle positioning. Sometimes the needle will contact the anterior tubercle of the transverse process at the anterior scalene muscle attachment or the posterior tubercle at the medial scalene muscle attachment. The rubbery resistance to injection, as in intramuscular injection, will be felt by a trained hand. We believe that our technique makes good anatomic sense, since both the brachial and cervical plexuses are enclosed b e t w e e n the same musculofascial planes, but it is not c o m m o n to seek paresthesias for a cervical plexus block. Since we deliberately do not seek paresthesias, our technique makes the block safer since paresthesias m a y be associated with neurologic damage (2),.as well as more pleasant for the patients. Having obtained excellent results, we w h o l e h e a r t e d l y r e c o m m e n d our method. Edward Gologorsky, M.D.
Anesthesia Department Miami Heart Institute Miami Beach, Florida Ruben A. Tenicella, M.D.
Anesthesia Department University of Pittsburgh Medical Center Pittsburgh, Pennsylvania
References I. Cousins ~U, Bridenbaugh PO, eds. Neural blockade in clinical anesthesia and management of pain. New York, Lippincott Raven, 1980: 305-307. 2. Winnie AP, ed. Plexus anesthesia. Philadelphia, WB Saunders 1983: 167-188, 253-258. Accepted/or publication October 4, 1996.
"No Paresthesias--No Anesthesia," the Nerve Stimulator or Neither? To the Editor: The main thrust of the correspondence by Golog0rsky and Tenicella (1) is *paresthesias m a y be associated with
neurologic damage." Unfortunately, this again focuses attention on what appears to be the unending controversy of w h e t h e r to: (1) elicit paresthesia; (2) use the nerve stimulator; or (3) employ a technique based only on tactile sensation, with which Gologorsky and Tenicella claim to have *enjoyed excellent results" and *wholeheartedly r e c o m m e n d it."
Eliciting Paresthesias The dictum *no paresthesia, no anesthesia" for certain peripheral nerve blocks (brachial plexus, sciatic, maxillary, mandibular nerves, etc.) is as valid today as in 1953, w h e n it was first stated (2). Not obtaining paresthesias (electric-like sensations) in such blocks, in which paresthesias confirm placement of the needle's point at the epineurium of the nerve, results in a lower incidence of satisfactory analgesia. Obtaining paresthesias results in at least a 98% incidence of satisfactory anesthesia without the need for conscious sedation. With use of the nerve stimulator, the incidence of satisfactory anesthesia in 230 axillary blocks and 80 lower limb blocks was 86% (3). Since the suggested use in 1962 of the nerve simulators (4), perhaps the dictum should read ~no paresthesias, but often failed anesthesia" (5). To date, only two prospective clinical studies have been published regarding paresthesias. In one involving 154 patients (6), the design was to avoid paresthesias. Nevertheless, paresthesias were unintentionally elicited in 54 patients (39%), but no neurologic sequele were found. In the other study which involved 533 patients, paresthesias were sought deliberately and obtained in 290 patients (7). Among the remaining 243 patients, in w h o m paresthesias were "to be avoided," they occurred unintentionally in 94 patients (40%) (7). Clinical evidence of nerve damage was found in 8 of the 290 patients (2.8%) and in 2 of the 243 patients (0.8%), but "no statistical difference was found in the frequency of nerve lesions between the two groups" (7). Despite this finding, the article concluded *that w h e n e v e r possible nerve blocks should b e performed without searching for paresthesias." This conclusion overlooks the obvious fact that in this study they occurred even w h e n not being sought (7). The studies that condemn paresthesias were performed in rabbits in which neuropathy resulted from "harpooning" (impaling) sciatic nerves under direct vision (8-11). This is markedly different from what occurs w h e n eliciting paresthesia in humans. In these h~ vitro and hz vivo animal studies, the sciatic nerves were impaled so that the entire bevel of the needle was buried below the e p i n e u r i u m - - t h a t is, they were intrafascicular (intraneural) (Fig. 1). It is not possible for anesthetists to verify that such intraneural needle placement occurs w h e n a paresthesia is elicited in humans. Furthermore, in the field of regional anesthesia, few would disagree with the statement of Scott et al. (12) that *animal studies should be accepted only as rough guides as to the situation in humans." A properly elicited paresthesia does not indicate that: (1) the bevel of the needle has punctured the
387
tained from the anesthetized limb. For this reason, we performed a second experiment, in which a special solution was prepared by dissolving carmine in gelatin, as described by Tanyola~ (7). In this experiment, the colored solution in the nerve t r u n k was demonstrated histopathologically; the macroscopic results were the same as in the first experiment. In these experiments, distribution of a solution to the surrounding tissues and to the nerve trunks during IVRA has been demonstrated in a m a n n e r different from the above-mentioned methods. Additional aspects of the mechanism of IVRA might be elucidated by further neurophysiologic studies in which a carmine-dyed local anesthetic agent prepared in the same m a n n e r as the carmine-dyed saline solution is administered.
Paul G. Loubser, M . D .
H/ilya (~elebi, M.D. Cengiz Oktem, M.D. Berrin Gfinaydin, M.D.
hzstittttefor Rehabilitation and Research Department of Anesthesiology Baylor Collegeof Medicine Houston, Texas
Department of Anaesthesiology and Reanimation Gazi UniversitySchool of Medicine Ankara, Turkey
References 1. Loubser PG. Spasticity associated with spinal cord injury. In: Narayan RK, Wilberger JE, Povlishock 31", eds. Neurotrauma. New York, McGraw-Hill, 1996: 1245-1258. 2. Botte MJ, Keenan ME. Percutaneous phenol blocks of the pectoralis major muscle to treat spastic deformities. J Hand Surg [Am] 1988: 13: 147-149. 3. Glenn MB. Nerve blocks, In: Glenn MB, Whyte J, eds. Practical management of spasticity in children and adults. Philadelphia, Lea & Febiger, 1990: 227-258. 4. Hecht JS. Subscapular nerve block in the painful hemiplegic shoulder. Arch Phys Med Rehabil 1992: 73: 1036-1039. Accepted for publication November 26, 1996.
A Different Approach in Demonstrating the Mechanism of Intravenous Regional Anesthesia To the Editor: The various clinical and experimental investigational methods for elucidation of the mode of action of intravenous regional anesthesia (IVRA) can be divided into three groups, namely radiographic, radioisotopic, and neurophysiologic studies (1-3). The essential mode of the anesthetic agent in IVRA (Bier block) involves direct block of nerve endings near the injection site initially and profound block of main nerve trunks later (4-6). We found that the distribution of a solution that might fill the vascular bed proceeds in a distal to proximal direction by performing IVRA with carmine-dyed saline in two mongrel dogs. In the first experiment, the tissues surounding the limb were dyed, and the nerve sample turned pink, as could easily be seen macroscopically. Since the carmine dye disappeared during fixation, we did not obtain the expected result. However, vactiolization was demonstrated in the nerve preparations ob-
References 1. Fleming SA, Vegia-Pires JA, McCutcheon RM, Emanuel CI. A demonstration of the site of action of intravenous lignocaine. Can J Anaesth 1966: 13: 21-27. 2. Corer C, Robin GC. Experimental studies on IVRA using radioactive lignocaine. Acta Anaesthesiol Scand Suppl 1969: 36: 127. 3. Miles DW, James J, Clarke DE, Witham JG. Site of action of intravenous regional anaesthesia. J Neurol Neurosurg Psychiatry 1964: 27: 574-576. 4. Raj PP, Garcia CE, Burleson JW, Jenkins MT. The site of IVRA. Anesth Analg 1972: 51: 776. 5. Lillie PE, Glynn CJ, Fenwick DG. Site of action of IVRA. Anesthesiology 1984:61: 507-510. 6. Rosenberg PH. IVRA: Nerve block by multiple mechanisms. Reg Anesth 1993: 18: 1-5. 7. Tanyola~ A. Morpholgische Untersuchungen fiber den Lappchenbau und Blutkrelslauf der Leber der Haussaugetiere. Ankara Oniv Vet Fak Dergisi 1972: XIX: 4: 1--445. Accepted for publication November 30, 1996.
Does the Interscalene Block Require Paresthesia? To the Editor: We would like to report a modification of the commonly used technique of interscalene block. The current recommendation is to obtain a paresthesia below the shoulder for a successful block; the operator has to "walk" the needle if the transverse process of C6 has been contacted until a parasthesia is obtained, (1,2). In our experience (over 25 years), the satisfactory block can be achieved without seeking a paresthesia. Having inserted the needle, as usually recommended (1,2), between the antenor and medial scalene muscles at the
388
Regional Anesthesia Vol. 22 No. 4 July-August 1997
level of the cricoid cartilage immediately behind the external jugular vein, we direct tire needle toward the transverse process of C6, which is readily palpable in normal individuals. We deliberately try not to elicit paresthesias. On contact with the transverse process (usually not deeper than 2 cm), the needle is aspirated in four quadrants and, provided one does not meet a *rubbery" resistance, the entire volume of anesthetic (usually 30 mL) is injected. The best predictors of success are the depth of needle insertion and the ease of injection (as with any other interfascial injection). We avoid deep needle insertion because of the possibility of missing the transverse process and contacting the vertebral body instead. Also, the risk of neuraxial injection is higher with deep needle insertion. Directing the needle toward the transverse process and a b o n y contact at shallow depth are both required for proper needle positioning. Sometimes the needle will contact the anterior tubercle of the transverse process at the anterior scalene muscle attachment or the posterior tubercle at the medial scalene muscle attachment. The rubbery resistance to injection, as in intramuscular injection, will be felt by a trained hand. We believe that our technique makes good anatomic sense, since both the brachial and cervical plexuses are enclosed b e t w e e n the same musculofascial planes, but it is not c o m m o n to seek paresthesias for a cervical plexus block. Since we deliberately do not seek paresthesias, our technique makes the block safer since paresthesias m a y be associated with neurologic damage (2),.as well as more pleasant for the patients. Having obtained excellent results, we w h o l e h e a r t e d l y r e c o m m e n d our method. Edward Gologorsky, M.D.
Anesthesia Department Miami Heart Institute Miami Beach, Florida Ruben A. Tenicella, M.D.
Anesthesia Department University of Pittsburgh Medical Center Pittsburgh, Pennsylvania
References I. Cousins ~U, Bridenbaugh PO, eds. Neural blockade in clinical anesthesia and management of pain. New York, Lippincott Raven, 1980: 305-307. 2. Winnie AP, ed. Plexus anesthesia. Philadelphia, WB Saunders 1983: 167-188, 253-258. Accepted/or publication October 4, 1996.
"No Paresthesias--No Anesthesia," the Nerve Stimulator or Neither? To the Editor: The main thrust of the correspondence by Golog0rsky and Tenicella (1) is *paresthesias m a y be associated with
neurologic damage." Unfortunately, this again focuses attention on what appears to be the unending controversy of w h e t h e r to: (1) elicit paresthesia; (2) use the nerve stimulator; or (3) employ a technique based only on tactile sensation, with which Gologorsky and Tenicella claim to have *enjoyed excellent results" and *wholeheartedly r e c o m m e n d it."
Eliciting Paresthesias The dictum *no paresthesia, no anesthesia" for certain peripheral nerve blocks (brachial plexus, sciatic, maxillary, mandibular nerves, etc.) is as valid today as in 1953, w h e n it was first stated (2). Not obtaining paresthesias (electric-like sensations) in such blocks, in which paresthesias confirm placement of the needle's point at the epineurium of the nerve, results in a lower incidence of satisfactory analgesia. Obtaining paresthesias results in at least a 98% incidence of satisfactory anesthesia without the need for conscious sedation. With use of the nerve stimulator, the incidence of satisfactory anesthesia in 230 axillary blocks and 80 lower limb blocks was 86% (3). Since the suggested use in 1962 of the nerve simulators (4), perhaps the dictum should read ~no paresthesias, but often failed anesthesia" (5). To date, only two prospective clinical studies have been published regarding paresthesias. In one involving 154 patients (6), the design was to avoid paresthesias. Nevertheless, paresthesias were unintentionally elicited in 54 patients (39%), but no neurologic sequele were found. In the other study which involved 533 patients, paresthesias were sought deliberately and obtained in 290 patients (7). Among the remaining 243 patients, in w h o m paresthesias were "to be avoided," they occurred unintentionally in 94 patients (40%) (7). Clinical evidence of nerve damage was found in 8 of the 290 patients (2.8%) and in 2 of the 243 patients (0.8%), but "no statistical difference was found in the frequency of nerve lesions between the two groups" (7). Despite this finding, the article concluded *that w h e n e v e r possible nerve blocks should b e performed without searching for paresthesias." This conclusion overlooks the obvious fact that in this study they occurred even w h e n not being sought (7). The studies that condemn paresthesias were performed in rabbits in which neuropathy resulted from "harpooning" (impaling) sciatic nerves under direct vision (8-11). This is markedly different from what occurs w h e n eliciting paresthesia in humans. In these h~ vitro and hz vivo animal studies, the sciatic nerves were impaled so that the entire bevel of the needle was buried below the e p i n e u r i u m - - t h a t is, they were intrafascicular (intraneural) (Fig. 1). It is not possible for anesthetists to verify that such intraneural needle placement occurs w h e n a paresthesia is elicited in humans. Furthermore, in the field of regional anesthesia, few would disagree with the statement of Scott et al. (12) that *animal studies should be accepted only as rough guides as to the situation in humans." A properly elicited paresthesia does not indicate that: (1) the bevel of the needle has punctured the