The Emergency Department Axillary Nerve Block - Windrose ：急诊科的腋神经阻滞-温德洛斯

The Emergency Department Axillary Nerve Block - Windrose ：急诊科的腋神经阻滞-温德洛斯 THE AXILLARY NERVE BLOCK FOR UPPER EXTREMITY ANESTHESIA IN THE EMERGENCY DEPARTMENT MARK E. BORDEN, MD EDWARD A. PANACEK, MD, MPH Revision 04/ 22/07 Word count: 2612 INTRODUCTION The Emergency Physician (EP) is frequently faced with the need for good upper extremity anesthesia. Forearm fractures, large and complex lacerations, and other conditions of the upper extremity are regularly treated in the Emergency Department (ED). Multiple techniques of regional anesthesia can be used to achieve pain control for fracture reduction. While hematoma blocks and Bier Blocks are frequently used, both have inherent difficulties and mixed efficacy (7,15). Procedural sedation (PSA) is also available for procedures. PSA requires more personnel and monitoring and generally results in a longer recovery time, and ED stay. The axillary nerve block (ANB) provides another alternative for achieving excellent upper extremity anesthesia. Although the technique is commonly and effectively performed by anesthesiologists, and by some emergency physicians, it is not well described in the emergency medicine literature. The ANB is an excellent, and very safe, regional anesthesia technique with the potential of reducing ED length of stay and improving overall patient satisfaction. We report six cases of emergency physician performed axillary nerve blocks that were successful in providing analgesia. We also describe the technique in detail. Technique Preparation Patient Selection: Patients in whom a motor and sensory assessment of the extremity is difficult or abnormal should not undergo an ANB. In addition, patient feedback during the procedure is helpful. Elbow dislocation, and supracondylar humerus fractures should not be reduced by the use of regional anesthesia, as there will be a delay in the neurovascular reassessment, and these injuries are prone to neurovascular compromise. Inability to abduct the arm will make the procedure more challenging, but this is not an absolute contraindication. Infection at the injection site is a contraindication. Patient Education: Explain to the patient that he/she will receive a “large injection of numbing medicine through a very small needle.” During the injection the patient may feel sensations that “shoot” to the hand or arm (paresthesias) and if these feelings are noted, he/she should tell you. Tell the patient that the pain will “go away,” and to a greater or lesser degree, so will the ability to move the arm. Since tricep motor function (extension) is usually lost to a greater degree than bicep/brachialis function (flexion), it is a good idea to warn the patient not to “scratch his/her nose,” as if they do so they may “hit” their nose instead. Tourniquet placement. Placement of a blood draw type tourniquet distal to the injection site encourages proximal movement of the anesthetic within the axillary sheath (see discussion). The tourniquet is placed while the arm is at the patient’s side. If the tourniquet is placed as high as possible on the patient’s arm before abduction of the arm, the tourniquet will generally be very close to the ideal location of three centimeters from the axillary crease upon abduction. The tourniquet is left in place for ten minutes following the injection. Approach The nerves that you will be blocking lie within a neurovascular sheath. As the Medial, Posterior, and Lateral cords of the Brachial Plexus enter the arm they divide into the Median, Radial, Ulnar, Musculocutaneous and Axillary Nerves. The Axillary Artery (becoming Brachial Artery) and Axillary Vein are within the neurovascular sheath at this level, as well. Two approaches to blocking this area are especially well suited for Emergency Department use. The ANB has been thoroughly studied in the pediatric population (13, 14, 17, 18) and is also very well suited for pediatric use. These techniques are described. Transarterial ANB is commonly performed through the transarterial approach (1,2,3,8). The transarterial approach takes advantage of the fact that the axillary artery is within the neurovascular sheath. By going through the artery, anesthetic is placed reliably within the neurovascular sheath, and can then diffuse, over time, into the nerves. Palpation of the artery should be done with several fingers to better localize the vessel. By palpating immediately proximal to the tourniquet, and injecting proximal to the palpating fingers, the physician is able to inject very proximally on the arm. This will ensure the highest probability of success. Though relatively superficial, the axillary artery can be difficult to palpate in some patients, and time should be spent to ensure accurate localization. Injection. A 5/8 inch straight 25 gauge or ? inch 25 gauge butterfly needle (with extension tubing) is preferred. A longer needle is not needed, and increases the chance of inadvertently injecting deep to the neurovascular bundle. The needle is inserted toward the palpated artery. When a flash is seen, insertion is continued until blood return ceases. A <0.5ml volume is then injected to clear the hub/extension tubing and aspiration is repeated to confirm position immediately behind the artery. The injection is then performed in 5.0 ml increments, aspirating between injections to ensure that the correct position has been maintained. When 5.0 ml remains, the needle is slowly withdrawn through the artery, until blood return ceases. A <0.5ml volume is then injected to clear the hub/tubing, and aspiration repeated to confirm position immediately superficial to the artery. The last 5.0 ml is then injected, and the needle withdrawn. With volumes greater than 30 ml, it is difficult to maintain position with the needle attached directly to the syringe, and thus the butterfly type needle with attached tubing is helpful. A second person can assist with the butterfly setup to handle the syringe, and this person is told when to aspirate and inject by the primary operator. A single operator can use the butterfly needle, and a small amount of blood will enter the extension tubing without aspiration as the artery is penetrated. Perivascular The perivascular technique is performed with the same equipment as the transarterial, and the same patient selection and education applies. Rather than penetrating the artery, the artery is carefully localized, and the anesthetic injected at the same depth as the artery, both superior, and inferior. When properly localized, the neurovascular sheath will display the same sausage-like swelling post injection as is seen with the transarterial method. The perivascular method can be guided by ultrasound, and the injected anesthetic can be clearly seen as an enlarging hypoechoic area (see pitfalls, 4). Anesthetic mixtures. Several different anesthetic mixtures can be used, dependent upon the desired duration of the block, and the patient involved (Table 1). Volume is more important to the success of the block than concentration, and saline is commonly added to increase the volume as needed. For a shorter acting block, 5.0 mg/kg of 1% lidocaine, diluted with equal volume of normal saline (1:1 mixture) to a concentration of 0.5%. This mixture is 5.0 mg per ml. and thus one ml per kg can be used. A maximum of 50.0 ml is generally considered adequate in most adults (250 mg lidocaine). Duration of action is from 40-90 minutes. Lidocaine with epinephrine can be used in the same volume and concentration, and this will extend the duration, as well as providing an added dosage safety margin. Larger volumes are sometimes used in the anesthesia literature, but the benefit of increasing beyond 50 ml seems minimal. If longer duration is desired, a 1:1 mixture of 20 ml of 0.25% bupivicaine, and 20 ml of 1% lidocaine with epinephrine, increased with 10 ml normal saline to a volume of 50.0 ml is used in larger adult (>50kg) patients. In smaller adults/females (<50kg) a 1:1 mixture of 15 ml of 0.25% Bupivicaine, and 15.0 ml of 1% lidocaine with epinephrine, diluted with 10cc of normal saline to a volume of 40.0 ml is used. The long lasting mixtures are also well suited to the patient who will be going from the ED to the OR for further repair, and have become an increasingly frequent choice at our institution. Case Examples Following are six representative cases from an ongoing prospective case series of axillary blocks performed in the emergency department at our institution. In each case the patient, and operator (person performing the ANB), were asked to “rate the pain of the anesthetic procedure/injection on a 0-10 scale 0 being no pain, and 10 being the worst pain you have ever felt. Both the patient and the operator (person performing the reduction) were then asked to “rate the pain felt during the reduction/straightening of the arm on a 0-10 scale.” Case 1. A 15-year-old male presented to the ED with a significantly displaced, both bone forearm fracture sustained in a fall. The patient appeared to be in considerable pain. After neurovascular examination the axillary block was instilled. Twenty ml of 1.0 % lidocaine with epinephrine, combined with twenty ml of 0.25% bupivicaine ( 40.0 ml total) was used. Complete pain control at rest was achieved within one minute of the injection. After return from x-ray the fracture was reduced to anatomic alignment under fluoroscopy by orthopedics. Several forceful attempts by multiple persons were required. The patient rated the pain of the injection 1/10, stating that there was actually no pain, but that it felt “strange.” The operator rated the pain of injection 0/10, as there was no objective sign of pain. Immediately following reduction the patient rated the pain of reduction 0/10, saying that there was “no pain.” An orthopedic resident rated the pain of reduction 0/10. The fracture later underwent ORIF as scheduled. Chart review showed no complications. Case 2. A 14-year-old male sustained a both bone forearm fracture by falling off a rope swing. On presentation the patient appeared to be in moderate pain. After neurovascular examination the axillary block was performed. Twenty cc of 1% lidocaine with epinephrine, combined with 20 ml of 0.25% bupivicaine, and diluted with 10 ml Normal Saline for a 50 ml total was used. Pain of injection was rated 0/10 by the patient, and by the operator. The patient was pain free at rest within one minute of block completion. After x-ray the fracture was reduced with moderate difficulty. Immediately following reduction the patient rated the pain of reduction 0/10. The Emergency Medicine Resident who performed the reduction also rated the pain of reduction 0/10. There was no evidence of complications acutely, or per subsequent chart review. Case 3. An 8 year-old male sustained a dorsally displaced distal radius fracture during a fall from the monkey bars at his school. The patient appeared to be in significant discomfort on arrival, and was apprehensive of needles. The patient did agree to a shot to “Make the pain go away”, however, and tolerated the injection well. 16 ml of 1.0 % lidocaine with epinephrine, diluted with an equal amount of normal saline was used. When asked to rate the pain of injection the patient was unable to identify when the injection had occurred, as he was not looking. A nursing observer rated the pain of injection as 0/10, as the patient “didn’t seem to notice the injection.” Pain control was apparent at 2 minutes post block, as the patient became talkative and began to move the arm without discomfort. The reduction was done with the c-arm by an orthopedic resident. Pain control was complete. The resident rated patient pain at 0/10. The patient showed no sign of discomfort, and was very curious to see the x-rays on the fluoro. monitor as the reduction occurred. The patient, when asked to rate the pain on a 0-10 scale after the cast had been placed stated that there “was, and is no pain.” Follow up visit noted a 15 degree apex volar angulation, which was considered acceptable. There was no evidence of complication acutely or per subsequent chart review. Case 4. A 54 year old male presented with a distal radius fracture after falling backwards out of a parked car. The patient had refused conscious or deep sedation, stating that; “It took days for me to come out of it last time.” Neurovascular exam was intact. The patient was diaphoretic and in moderate distress. An ANB was performed using twenty ml of 1 % lidocaine with epinephrine, combined with 20.0 ml of 0.25% bupivicaine and diluted with 10.0 ml Normal Saline for a total volume of 50 ml. Pain of injection was rated 1/10 by the patient. The operator rated the pain of injection 0/10 as there was no visible sign of pain. The patient was pain free within five minutes of the injection. The fracture was reduced with difficulty, requiring repeated forceful manipulation. The patient rated pain of reduction 0/10 saying; “I didn’t feel a thing.” The orthopedic resident who performed the reduction rated the pain of reduction 0/10. There were no evident complications. The patient returned 2 weeks later. He had missed his appointment with orthopedics and had used his cast in a fight, “to defend himself”, breaking the cast in the process. Neurovascular exam was intact at this time. No complications of the previous anesthesia/reduction were apparent. Case 5. A 55 year old male presented from an outlying facility with a splinted, dorsally displaced distal radius fracture. Reduction by hematoma block had been attempted, but had failed. The patient had refused a repeat hematoma block stating that it was “the most painful experience of my life.” The patient agreed to undergo a “nerve block.” and was consented. After neurovascular exam, twenty ml of 1.0 % lidocaine, 20.0 ml of 0.25% bupivicaine, and 10.0 ml of normal saline was used. The patient rated the pain of injection at 2/10. An observer rated the pain of injection at 1/10. Pain control at rest was immediate, but the patient remained apprehensive. Complete distal motor blockade and dense anesthesia of the fracture site occurred at twenty minutes post injection. The patient seemed tense and winced several times during the reduction, which was difficult, and required repeated attempts. The orthopedic resident rated the pain of reduction at 1/10. The patient rated the pain of reduction at 2/10. When asked if he would have a “nerve block” again he said yes, but added that some “happy juice” would be good, too. There were no evident complications. Case 6. A 76 year old female presented with a dorsally displace distal radius fracture sustained during a ground level mechanical fall. The patient appeared to be in no distress on arrival, with pain on movement only. Neurovascular exam was intact. The patient had a complicated medical history including renal failure and diabetes. A block of short duration was desired by the orthopedist. Fifteen ml of 1.0 % lidocaine with epinephrine was combined with fifteen ml of plain lidocaine. Ten ml of normal saline was added for a total volume of 40.0 ml. The patient rated the pain of the transarterial injection as 0/10, as did a nurse observer. As the orthopedic resident was present at the time of the injection, he wanted to perform the reduction as soon as possible. At seven minutes the resident felt that the arm was ready for manipulation, as the patient showed no sign of pain when the fracture site was gently moved. Splinting materials were readied and at 10 minutes the arm was reduced. The orthopedist rated the pain of reduction at 0/10, as did the patient, who showed no sign of discomfort. There were no acute complications. Chart review showed good healing and no complications. Discussion: The axillary block was originally described by Dejong in 1961(1). This paper provides a thorough discussion of anatomy and technique, and is highly recommended as background reading. There are many techniques used to localize the neurovascular sheath and these include the use of nerve stimulation, and elicitation of paresthesias. The transarterial, and perivascular techniques, however, are similar in efficacy (6,8), far less likely to cause nerve injury, and are thus safer, and less subject to criticism. Forearm fractures can be anesthetized prior to reduction in several ways. The transcortical anesthesia technique or “Hematoma Block” is commonly used. The advantage of this technique is speed and simplicity. Disadvantages of this method include pain as an 18 or 20 gauge needle is inserted into the fracture site, and potential risk of infection, as a closed fracture is converted into an open one. Pain during reduction is also frequently significant (see case 5 above) especially with difficult reductions, as skin sensation generally remains intact. The low dose “Bier Block”, is another method used by emergency physicians. (15) The advantages of this technique include better anesthesia than the Hematoma Block and fairly consistent efficacy. Disadvantages of this method include the need to place an I.V. in the injured extremity, the need for nursing attendance to maintain the blood pressure cuff, and the risks associated with accidental systemic administration of large doses of local anesthetic. If the initial attempt at reduction fails, the block must be repeated before another attempt. The shorter duration of the Bier Block prevents instillation before x-ray, and manipulation for x-ray is therefore more painful. The I.V. must be removed before application of a splint. Procedural sedation is often used for the reduction of forearm fractures. Both moderate and deep sedation are used safely and effectively by emergency physicians. Advantages of procedural sedation include; availability of multiple agents with safe and effective sedation profiles, and lack of operator dependency. Disadvantages include adverse drug reactions, respiratory depression, aspiration, hypoxia, and other airway problems, delayed recovery time, and the requirement of significant nursing resources. Reduction without anesthesia may also be a viable option. Immediate reduction is indicated if the trauma has caused a neurovascular compromise in the extremity. A dose of medication IM may provide some pain control in these rare cases, and distracting the patient may help. The ANB is another option that can be used for upper extremity injuries. Advantages of this technique include; minimal nursing support required, speed, simplicity, long duration (allowing for repeat reductions/repeat x-rays if needed), and continued pain control in the post reduction period. The ANB also provides muscular relaxation, which facilitates fracture reduction. The technique is simple, and easily taught. It is comfortable for the patient and extremely unlikely to cause a complication. The ANB can be performed quickly, eliminating the need for an IV in most cases. Disadvantages include; a degree of operator dependency, the inability to repeat the neurologic examination immediately after reduction, and potential drug reactions. When performed properly the ANB results in complete regional anesthesia, allowing an absolutely pain free reduction in over 90 percent of cases (3,4,8,12) There is some variability in the anatomy of the region, which results in the occasional incomplete block. Good pain control at rest, however, is still generally achieved and this pain control is nearly immediate. In the case of an incomplete block, the patient can be gently tested for pain at the fracture site to determine if adequate anesthesia for reduction has been achieved. Another regional technique such as a musculocutaneous nerve block (2) or intravenous medication can be used to supplement if needed. Pitfalls the author has observed in over 10 years of teaching the ANB include: 1.Infiltrating too deep.. As already noted, the neurovascular compartment is very superficial . Even in an obese patient, a ? inch needle has always been long enough. In the average patient you will not need the entire ? inch needle. If the needle is advanced too far beyond the artery you will inject deep to the neurovascular compartment, and a block will not be achieved. A recent study (23) emphasizes that using too long a needle can decrease success rate significantly. The correctly performed injection into the neurovascular compartment produces a “sausage like”, confined, subcutaneous swelling, that is easily seen in all but the most obese patients (figure 4). 2. Using too small a volume of anesthetic. The ANB is a volume dependent technique. At least 40.0 ml is needed to diffuse adequately in the adult patient. When using the transarterial/perivascular techniques the objective is to fill the neurovascular compartment with anesthetic that then diffuses into the nerves. An adequate volume is required to both surround the nerves, and to move proximally far enough to reach the musculocutaneous/ proximal nerves. 3. Attempting procedure too soon. Immediate rest pain control is generally achieved with a properly placed injection. If a gentle manipulation is attempted immediately after the block, however, some pain will still be felt. The person performing the reduction in this case should be instructed to wait before performing the procedure. A significant number of patients will be ready at five minutes, but the density of anesthesia will generally increase for 20-30 minutes. In obvious fractures, the patient can receive the ANB prior obtaining radiographs. The positioning required in radiology is thus less painful. 4. Not injecting proximally enough on the arm. The more proximally on the arm the ANB is performed the more likely it will be complete. The musculocutaneous nerve has already left the neurovascular bundle at the point where the injection is performed: consequently, proximal placement of the anesthetic is required. When using ultrasound to locate the neurovascular sheath it is important to inject proximally to the probe. There is a tendency for physicians new to the ANB to place the probe proximal to the injection, as the probe tends to rest stably in the axillary crease. This probe placement results in a more distal injection, and a higher partial block rate. In the case of an incomplete block, another regional technique can be used to supplement the block(2). Moderate sedation can also be used in the case of an incomplete block and the doses of these medications will usually be much lower than those normally needed to provide good pain control during reduction. Conclusion: We described the use of the axillary nerve block in the ED. The ANB offers many advantages for regional anesthesia. Its ease of use and clinical efficacy make it an excellent option for pain control in forearm injuries. The ANB as described is a surprisingly painless, highly effective, and simple technique that has withstood the test of over 45 years of continued use. The methods which we use in the emergency department are subject to continuous review and criticism, both by ourselves, and by many physicians of other specialties. The ANB as discussed was perfected in such an environment, and has much to recommend it for use by the emergency physician. Figure 4-Finishing the injection Figure 1-Placement of the partial venous tourniquet Figure 2-Palpation and injection Table 1-Axillary Block Anesthetic Doses Duration Drug Dosing Volume Comments Short Lidocaine 0.5% 5.0 mg/kg Dilute 1.0 % Use 40 ml for <40 minutes 1 ml per kg lido 1:1 with small adults body weight normal saline <50kg to maximum of 50 ml Medium Lidocaine 0.5% 5 mg/kg Dilute 1% lido Use 40 ml for 40-90 minute with 1 ml per kg 1:1 with small adults epinephrine body weight normal saline <50kg to maximum of 50 ml Long Lidocaine 1.0% 20 ml Dilute with Use 15 ml >90 minutes with lidocaine with normal saline Lidocaine/15 ml epinephrine epi. to total of 50ml Bupivicaine/10.0 Bupivicaine ml saline for 0.25% 20 ml 0.25% small adults Bupivicaine <50kg Figure 3-The two operator technique Figure 4) Sausage-like swelling of the neurovascular compartment after properly placed injection REFERENCES 1) Dejong, R. H. 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