Axillary block of the brachial plexus

Transcription

1 VOL 17 NO 3 ANESTHESIA JULY 1962 Axillary block of the brachial plexus Guest Faculty Member, Department of Anesthesia Western Reserve University Medical School, Cleveland 6, Ohio The axillary approach to brachial plexus block is rapidly gaining in popularity in North America, having almost replaced the supraclavicular approach in some centres and the method would appear to deserve wider recognition. Axillary block offers several advantages over the supraclavicular technique of brachial plexus block and has no serious disadvantages. The principal advantage of the axillary approach is the complete avoidance of the complication of pneumothorax, while offering at least an equal chance of successful block. When bilateral blocks are to be performed, the axillary technique is particularly suitable as it avoids the doubled risk of inducing pneumothorax and phrenic nerve paralysis which exists if the supraclavicular method is used. The value of brachial plexus block for the patient with a full stomach, for the outpatient, for the diabetic, for the patient with cardiac, pulmonary, hepatic or renal disease and for the tough anaesthetic-resistant adult is recognised. Only the risk of inducing a pneumothorax may have deterred anaesthetists from employing an otherwise excellent technique for such patients. Brachial plexus block is associated with little or no post-operative nausea and vomiting. It is an economical technique, requires the minimum of equipment and is suitable for use in disaster conditions. HISTORY In 1911 Hirschel' injected the brachial plexus blindly. He directed a 23 inch needle upwards from the axilla, passing it in front of the plexus and behind the clavicle. With so short a needle he could not have 274

2 ANESTHESIA 275 reached the brachial plexus in the neck, as was his intention, but longer needles were unobtainable at this timez. Labat3,in 1922, describedanaxillary approach tothe brachial plexus. Pitkin's method, devised in the late 1920's and published in 1946 after his death4, modified Hirschel's approach by using a needle 6 to 8 inches long to reach the transverse processes of the sixth and seventh cervical vertebrae from the axilla. Although successful in Pitkin's hands, the method never became popular, perhaps because the blind insertion of an 8 inch needle in two directions appealed to neither patient nor anaesthetist. In 1949 Accardo and Adrianis described a technique which, for the first time, made an axillary approach to the brachial plexus simple, safe and effective, because it employed accurate anatomical landmarks and entailed only a relatively superficial injection. In this technique no attempt is made to reach the brachialplexus in the neck. This approach with slight but important modifications has been the basis of the methods used by Burnham6 and Hudon and Jacques7in Clayton and Turner8 reported on the use of a similar technique in children in the same year. De Jongg reported on the method in 1961 and in that year Brand and Papper 10 compared axillary block favourably with supraclavicular block. ANATOMY The axilla The axilla is shaped like a pyramid, having the axillary fascia as its base. This base is small when the arm is by the side and the fascia is relaxed. The apex of the pyramid is the portal through which the vessels and nerves pass between the neck and the axilla. The axilla contains the axillary artery and vein, the cords and terminal branches of the brachial plexus, fat and lymph nodes. As the cords and terminal branches of the plexus cross the axilla they maintain a definite and constant relationship to the axillary artery and, together with the artery, constitute a neuro-vascular bundle. The axillary sheath This is a sheath of tough fibrous tissue which encloses the axillary artery, the axillary vein, the lower part of the brachial plexus and its terminal branches. The axillary sheath is crossed by septa which fix the nervous structures in their constant relationship to the artery. De Jongg estimates that the axillary sheath of the average adult is capable of holding 42ml of solution.

3 276 ANESTHESIA M U SCU LOCU TAN E OU 5 N. MEDIAN N. FIG. 1 Transverse section of arm at lower axilla The brachial plexus In the upper axilla, the brachial plexus is composed of a lateral, medial and posterior cord, so-named because of their relationship to the axillary artery. In mid-axilla the plexus gives off branches to shoulder and chest muscles and also the medial brachial and medial antebrachial cutaneous nerves. These two cutaneous nerves remain within the axillary sheath in their downward course. In the lower axilla the brachial plexus forms its principal terminal branches, the musculocutaneous, median, radial and ulnar nerves. The last three named nerves continue downward within the axillary sheath and are closely related to the artery. The median, ulnar and radial nerves lie respectively anteriorly, posteriorly and medially to the artery in its easily palpable lower portion. The musculocutaneous nerve, it should be noted, does not continue downwards within the axillary sheath, but soon leaves the sheath to enter the substance of the coracobrachialis muscle.

4 ANSSTHESIA 277 Consequently, solutions injected into the lower and easily accessible part of the axillary sheath can readily reach the radial, median and ulnar nerves, but can only reach the musculocutaneous nerve and the brachial plexus by spreading upwards within the axillary sheath. To ensure this upward spread, a volume of solution sufficient to fill the axillary sheath is required and the injection should be made as high in the axilla as possible. If the musculocutaneous nerve is not blocked, the skin on the radial side of the forearm will remain sensitive to pain. The in t ercostobrachial nerve This is a branch of the second thoracic nerve, is not a branch of the brachial plexus and is not blocked directly by either the supraclavicular or the axillary technique of brachial plexus block. Fortunately, the nerve lies under the skin at the point of injection used in the axillary approach and so can easily be blocked after performing the main injection into the axillary sheath, thereby producing analgesia of the medial surface of the upper arm. Consideration of these anatomical details shows that by the injection of local anaesthetic solution into the Mary sheath in amounts adequate to ensure spread within the sheath, it is possible to produce analgesia of almost the whole upper limb. Sensation will be retained over the upper part of the deltoid muscle in the area of skin supplied by the supraclavicular nerves (C3 and C4) and in the shoulder joint, which is supplied mainly by the suprascapular nerve, a branch of the brachial plexus in the neck. TECHNIQUE Premedication is usually given and may usefully include pethidine or an opiate. The patient lies on his back with his arm abducted to a right angle. The elbow is then flexed and the arm allowed to rest on a convenient support. The axillary hair having been shaved if necessary, antiseptic solution is applied to a wide area of the upper arm and axilla which is then draped with sterile towels. Sterile gloves are worn by the anaesthetist, who now stands by the patient s side, facing towards the patient s axilla. The pulsations of the axillary artery are sought and are then traced proximally as high into the axilla as possible. This, the highest point in the axilla at which arterial pulsations can be distinctly felt, is the preferred site for injection. Injection at a lower point may result in incomplete analgesia. A short fine needle should be used for the injection. A needle of 24 Standard Wire Gauge is suitable. Such a needle probably lessens the risk of damage to nerves, and accidental puncture of the axillary

5 278 ANESTHESIA FIG. 2 The axilla, showing important landmarks and needle in position artery or vein is unlikely to be followed by the formation of a hamatoma. A small needle is less alarming to the patient, causes less pain and a needle 3 inch in length is quite long enough to reach the axillary sheath. A skin wheal is raised at the selected point, which should be proximal to the lower border of the pectoralis major muscle. The needle is now advanced so that it just misses the axillary artery, passing to one side of it. A finger is kept over the artery during this procedure. A very characteristic pop or click is experienced as the needle pierces the fascia1 wall of the axillary sheath. The needle point now lies within the neurovascular compartment. After careful aspiration for blood, 1 5-2Oml of solution are injected. The needle point is now withdrawn from the axillary sheath to the subcutaneous tissues and is reinserted into the axillary sheath on the other side of the artery, where a further 15-2Oml of solution are injected. Arterial pulsations may be transmitted along the needle, confirming its presence within the axillary sheath. Accidental puncture of the axillary artery or vein is not serious, provided it is recognised and intravascular injection is avoided. No harm has resulted from proceeding with the block after vascular puncture. Paraesthesia are not sought, although their occurrence presages a successful block. If it is desired to block the intercostobrachial and medial brachial cutaneous nerves, 2-3ml of solution are injected subcutaneously before finally withdrawing the needle. This should be done if the area of

6 ANESTHESIA 279 operation includes the medial side of the upper arm, or if a pneumatic tourniquet is to be used. Before the application of a pneumatic tourniquet, a subcutaneous ring of solution may be placed round the upper arm. This ring block was performed in only a few cases in the present series, and in the many cases where it was omitted, the tourniquet was well tolerated and this procedure is not regarded as essential. Analgesia is usually complete in from ten to twenty minutes, but in a few instances as long as thirty minutes may be required for complete analgesia. The mean time of onset of complete block was sixteen minutes in the present series. There is usually evidence of sympathetic blockade, and muscular weakness is common if higher concentrations of local anasthetic drugs are used. Drugs Lignocaine in 1 per cent solution and 2-chloroprocaine in 2 per cent solution were the agents used in over 90 per cent of the cases in the present series. Both drugs were very effective and there were no toxic reactions to either agent. In most cases adrenaline in 1 : 200,000 dilution was also used, and in a few instances amethocaine in per cent concentration was combined with 2-chloroprocaine in a successful effort to prolong analgesia. Using these agents in these concentrations, it is possible to inject 40ml of solution with safety and to fiu the axillary sheath. Maximum doses of these drugs for healthy adults are: lignocaine 500mg, 2-chloroprocaine looomg and amethocaine 1OOmg11. For children the doses of these drugs should be estimated on the basis of body weight using 5-7mglkg of lignocaine, mg/kg of 2-chloroprocaine and mg/kg of amethocainell. The ill or elderly adult should receive 4Oml of a weaker solution, thus reducing the dose in mg, but still using sufficient solution to fill the axillary sheath. RESULTS 140 axillary blocks were performed in fifteen months by various workers, including anasthetists and surgeons in training. Some of these were performing their fist nerve blocks and it was in their hands that most of the unsuccessful blocks occurred. 123 blocks (87.9 per cent) were successful, 15 blocks (10.7 per cent) were partially successful and 2 blocks (1.4 per cent) were failures. A block was classed as successful only if complete analgesia of the area supplied by the radial, median, ulnar and musculocutaneous nerves was achieved, and as partially successful if three of these four nerves were blocked. If more than one nerve remained unaffected the block was classed as a failure. The incomplete analgesia in fifteen cases is believed to be due either to the injection of too little solution

7 280 ANBSTHESIA (less than 25ml) or to injection too low in the axillary sheath, and it is probable that these results could be improved upon. Although these partially successful blocks were easily reinforced by a further injection into the axillary sheath or by blocking the unaffected nerve at the elbow or wrist, they are not regarded as successful for the purposes of this report. In the two cases where the block was a complete failure, it is presumed that the solution was deposited outside the axillary sheath. One of these patients was a very obese woman, in whom it was difficult to locate the axillary artery. Twenty-one patients (15.0 per cent) were less than fourteen years old, the youngest being only three years of age. These children had received sedative premedication and usually co-operated well, the injection being no more upsetting than those to which they had become accustomed in the course of various inoculations and vaccinations. The technique was used for emergency surgery in these children as it avoided the risk of inhaling vomitus, which would have been associated with general anaesthesia. Complications There were no serious complications in this series of cases. Haematoma formation, intravascular injection and signs of overdose of local anaesthetic drug did not occur and there were no instances of postblock nerve damage or pain. Two patients developed transient headache and hypertension, attributed to the absorption of adrenaline. A needle broke in the arm of a restless child, but was easily removed. In the case of a child who had a supracondylar fracture of the humerus, the radial pulse became imperceptible after axillary block with 1 per cent lignocaine solution containing 1 : 200,000 adrenaline. The fracture was reduced and the radial pulse was restored. It is not possible to be certain whether the impairment of the arterial blood flow was due to vascular spasm caused by the injection of adrenaline near the axillary artery, or to occlusion of the brachial artery at the site of fracture. The second explanation seems the more probable in view of the sequence of events, and Clayton and Turners in fact consider the sympathetic paralysis which accompanies brachial plexus block to be beneficial in this type of fracture. These results are in general agreement with reported series of axillary blocks, in none of which did any serious or permanent complications occur The precise incidence of pneumothorax complicating supraclavicular block of the brachial plexus is not easy to assess, but the complication is not uncommon. The pneumothorax may not develop for some hours and so may go undetected12. Adriani and Evangelou13 found

8 Risk of pneumothorax Phrenic nerve paralysis Safety of bilateral blocks Homer s syndrome Vagus and recurrent Laryngeal nerve paralysis Risk of subarachnoid injection Risk of hzmatoma formation Upset for patient Damage to nerve tissue Success rate Suitability for operations on the shoulder ANESTHESIA 28 1 Table 1 A comparison of axillary and supraclavicular techniques AXKLARY None None No impairment of ventilation None None None Slight, using fine needle Slight, using fine needle Probably very slight or none % Not suitable SUPRACLAVICULAR Occurs in 1-6 % Occurs in % Ventilation may be substantially impaired Occurs in % May occur Very slight rjsk : 0.06% in one series Greater risk, using larger needle Greater, using larger needle Probably greater, using large needle and injecting into the brachial plexus % Suitable that pleural puncture was the commonest complication of nerve blocks in general. Pneumothorax has followed supraclavicular brachial plexus block in 0.9 to 6.1 per cent of cases in recorded series and at least three fatalities from this complication have been reported1 8. Wishart19 stressed the special risk of producing a tension pneumothorax by puncturing an emphysematous bulla. Phrenic nerve paralysis is common after supraclavicular block20 and is usually of no significance unless bilateral or in the presence of already impaired pulmonary function. Homer s syndrome21, vagus and recurrent laryngeal nerve paralysis and subarachnoid injection may all follow supraclavicular, but not axillary block of the brachial plexus. The development of postblock neuropathy may be related to the careless or traumatic use of a needle23, which may perhaps cause small intraneural hamorrhages. The intraneural injection of local anasthetic solutions may damage nerve tissue by increasing the tension within the nerve. The use of fine needles and the avoidance of direct injection into the brachial plexus may assist in preventing neuropathy after axillary block. In the present series and other recorded series of axillary blocks this complication did not occur, or was of brief duration. The tourniquet paralysis syndrome26 may, provide an alternative explanation for any neurological sequelae of brachial plexus block. Recent publications on brachial plexus block record the incidence of successful blocks as follows:

9 282 ANESTHESIA Table 2 Percentages of successful blocks AXILLARY APPROACH SUPRACLAVICLAR APPROACH Clayton &Turner 98.7 per cents Hudon & Jaques 95.0 per cent7 Burnham 92.6 per cent6 Forth & Tremblay 91.5 per cent24 Brand & Papper 91.5 per cent1 0 Brand & Papper 84.4 per cent 10 De Jong 91.5 per cent9 Hudon & Jaques 86.0 per cent7 Present series 87.9 per cent These results show that the axillary technique can offer at least as high a success rate as can the supraclavicular approach. It is unlikely that any technique of brachial plexus block can be successful in every case. Moore25 states that the over-all incidence of complete failure of regional block techniques in the hands of physicians skilled in their usage is approximately 5 to 7 per cent. SUMMARY AND CONCLUSION Axillary block of the brachial plexus involves the injection of an adequate amount of local anzesthetik solution into the axillary sheath, using the axillary artery as a landmark. In a series of 140 cases, 123 blocks (87.9 per cent) were completely successful and only 2 (1.4 per cent) were considered failures. In the remaining fifteen cases, three of the four major sensory nerves of the arm were blocked. The hazard of pneumothorax is eliminated by using the axillary approach and other complications of brachialplexus blockareabolished or their incidence is reduced. The axillary technique should be preferred where the complications of pneumothorax or phrenic nerve paralysis present special dangers, as in patients with cardiac or pulmonary disease and where bilateral block is to be performed. Axillary block is simple, safe and at least as successful as the supraclavicular approach and may replace the latter technique for operations below the level of the shoulder. References IHIRSCHEL, G. (1911). Munch. med. Wschr., 58, (2), PITK KIN, G. P. (1946). Conduction anesthesia. Editors, SOUTHWORTH, J. L. and HINGSON, R. A., J. B. Lippincott Company, Philadelphia, ed. I, p LABAT, G. (1922). Regionalanesthesia. W. B. Saunders, Philadelphia. 4PITKIN, G. P. (1946). Conduction UneStheSiU. Editom, SOUTHWORTH, J. L. ~~~HINGSON, R. A., J. B. Lippincott Company, Philadelphia, ed. I, p.448. SACCARDO, N. J. and ADRIANI, J. (1949). South. med. J., 42,920. URNHAM, P. J. (1959). J. Amer. med. Ass., 169,941. THUDON, F. and JAQUES, A. (1959). Cunud. hcesth. Soc. J.,6,400. CLAYT TON, M. L. andturner D. A. (1959). J. Amer. med. Ass

10 ANAZSTHESIA 283 9DE JONG, R. H. (1961). Anesthesiology, 22,215. ~OBRAND, L. and PAPPER, E. M. (1961). Anesthesiology, 22,226. * 'BONICA, J. J. (1959). Clinical applications of diagnostic and therapeutic nerve blocks. Charles C. Thomas, Springfield, Ill., p.76. M MOO RE, D. c. (1955). Complications of regional anesthesia. Charles C. Thomas, Springfield, Ill., pp I3ADRIANI, J. and AVANGELOU, M. (1955). curr. Res. Anesth.,34,96. 14GRISWOLD,R. A. andwoodson, W. H. (1943). Amer. J. surg.,59,439. ~SDMARJIAN, E. (1946). Rhode Islundmed. J., 29, M00RE, D. C. andbridenbaugh, L. D. (1954). Anesthesiology, 15,475. I'BONICA, J. J., MOORE, D. C. andorlov, M. (1949). Amer. J. Surg., 78,65. 18DE PABLO, J. S. anddiez-mallo, J. (1948). Ann. surg., 128,956. WISHAR ART, H. Y.(1954). Brit. J. Anlesth., 26, 120. ~OMOORE, D. c. (1961). Regional block. Charles C. Thomas, Springfield, Ill., ed. 3, p.198. M MOO RE, D. c. (1961). Regional block. Charles C. Thomas, Springfield, Ill., ed. 3, p.193. M MOO RE, D. c. (1955). Complications ofregionalanesthesia. Charles C. Thomas, Springfield, Ill., p.49. ~~BONICA, J. J. (1958). Modern trends in anaesthesia. Editors, EVANS, P. T. ~~~GRAY,T. c.butterworth, London,p FORTIN, 0. andtremblay, L. (1959). Canud. Anlesth. soc.j., 6,32. ~SMOORE, D. c. (1955). Complications of regional anesthesia. Charles C. Thomas, Springfield, Ill., p.247., MOULDAV AVER, J. (1954). Arch. Surg. 68,136.