To minimize the possibility of error due to the presence of heparin, it is necessary to collect at least 1 mL of blood in a prepackaged syringe or 3 mL of blood if preparing your own syringe with heparin. If it is necessary to redirect the needle, it is imperative to first withdraw the needle until the tip is just below the skin surface before changing the angle in order to avoid lacerating the artery or adjacent structures. If no blood return occurs, slowly withdraw the needle and watch for blood flow into the syringe. The blood flow will generally fill the syringe without necessitating the withdrawal of the plunger in a patient with a brisk pulse. Advance the needle through the skin until blood enters the syringe ( Figure 57-6B). Insert the needle at a 30° to 45° angle to the skin and just above the arterial pulse ( Figure 57-5). This will allow for easier assessment of arterial blood return. Withdraw the plunger of the syringe so that 1 to 3 mL of air space is available in the syringe. Grasp the heparinized syringe with the dominant hand. Reidentify the pulse by palpation with the nondominant hand ( Figure 57-6A). Other useable sites include the dorsalis pedis, brachial, posterior tibial, and superficial temporal arteries. 1 The use of other sites generally follows the techniques described below for the radial artery with the exception of the regional anatomic differences. The discussion below focuses on puncture or cannulation of the radial and femoral arteries as over 90% of arterial punctures or cannulations occur at these sites. An attempt at ipsilateral ulnar artery catheterization is not advisable as both limbs of the hand's circulation may be compromised. Other acceptable second-attempt sites of access include the femoral, dorsalis pedis, and brachial arteries. The radial artery on the contralateral wrist is also a satisfactory second site for attempted access. If the first attempt at needle or catheter introduction is unsuccessful, and the pulse is still palpable, reattempt the procedure more proximally along this same artery. 1 Begin distally where the pulse is most palpable near the proximal wrist flexor crease. The preferred site for the initial attempt at arterial puncture or cannulation is the radial artery. + +ĭescriptions of the anatomy for arterial puncture or cannulation sites are described in detail earlier in this chapter. If the artery is to be cannulated, the arm should remain in extension while the cannula is in place. The preferred location for puncture or cannulation of the brachial artery is in, or just proximal to, the antecubital fossa and directly above the brachial artery pulse. The arterial pulsation is most easily identified at the level of the proximal flexor crease of the antecubital fossa. The brachial artery pulse should be palpable just medial to the biceps muscle. Move laterally until the medial edge of the biceps muscle is palpated. In order to locate the artery, start by palpating the medial epicondyle of the humerus. The brachial artery is more easily identified when the elbow is fully extended. In the antecubital fossa, the brachial artery is located lateral to the medial epicondyle of the humerus and medial to the biceps brachii muscle. The brachial artery divides at approximately the level of the neck of the radius to become the ulnar and radial arteries. ![]() The brachial artery courses along the medial side of the antecubital fossa just lateral to the median nerve ( Figure 57-3). Thus it is recommended, but not required, to cannulate another site if the Allen test is abnormal. 2 This can include arterial thrombosis, hand ischemia, and hand necrosis. 4 Although an abnormal Allen test may not preclude radial artery puncture or cannulation, it may indicate a greater need for caution and alert the Emergency Physician to potential problems after the procedure is performed. 39 The relative safety of radial artery cannulation without the Allen test has been demonstrated in a large case series of patients without major peripheral vascular disease. 1, 2, 4, 38 The Allen test is subjective, often improperly performed, and has poor sensitivity and specificity to predict complications. Some authors have questioned the utility of performing an Allen test. There is concern that radial artery occlusion from an intraluminal clot or an external hematoma can result in hand ischemia if the ulnar artery cannot provide adequate collateral blood flow. The performance of an Allen test to confirm adequate collateral circulation to the hand is generally advocated before radial artery puncture or cannulation.
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