Pitfalls

• Any sign of vascular compromise to the hand should be evaluated immediately. Amputation of digits is frequently the only treatment option available because ischemia is not noticed until tissue necrosis has occurred.

Diagnostic Studies

Plain radiographs of the distal radius, wrist, and hand demonstrated no acute bony abnormalities. Upper extremity angiography was performed later in the patient's hospital stay, and complete occlusion of the radial artery was demonstrated just proximal to the wrist. Furthermore, the ulnar artery was shown to provide little blood flow to the radial side of the hand. Some collateral flow was present coming from the ulnar arch, although no large vessels could be seen extending to the distal portion of the thumb or index finger.

Differential Diagnosis

Radial artery thrombosis due to cannulation injury Embolic thrombosis of digital vessels

Small vessel occlusion due to diabetes or a vasculitic disease

Digital ischemia as a side effect of pharmacologic blood pressure support (e.g.,

Neo-Synephrine related vasoconstriction) Localized severe infection

Diagnosis

Radial Artery Thrombosis Due to Cannulation Injury in a Patient with Radial Dominant Flow to the Hand

Vascular complications due to cannulation or injection injuries can be devastating. It is important to know how radial artery cannulation injury occurs, not only because of the high frequency of radial artery use for placement of monitoring catheters, but also because of the extreme consequences of radial artery damage in select individuals.

Understanding the arterial anatomy of the hand is key in accounting for cannulation injury. There are two main arches that support vascularity to the digits: the superficial palmar arch, which is an extension of the ulnar artery, and the deep palmar arch, which generally arises from the radial artery (Fig. 25—3). The superficial (ulnar) arch, which is

Proper Volar Digital Arteries

Common Volar Digital Arteries

Proper Volar Digital Arteries

Common Volar Digital Arteries

Deep Volar Arch

Radial Artery.

Volar

Metacarpal Artery I

Ramus of the Superficial Arch

Radial Artery.

Volar

Metacarpal Arteries II-IV Superficial Volar Arch

Deep Volar Arch /Ramus of the Deep Arch Ulnar Artery Volar Interosseous Artery

Figure 25—3. Vascular anatomy of the hand, demon-

ficial arches and their typical communications.

• Forcible extension of the digits or hyperextension of the wrist can produce blanching, causing a false-positive Allen's test.

• At least 11 pounds of pressure are required to occlude the radial or ulnar artery at the wrist when performing an Allen's test.

• Allen's test must be modified when it is performed in unconscious patients. To perform the test for these patients, hand ischemia can be temporarily induced using an Esmarch bandage, and a reflow to the palmar arches can be assessed using a Doppler ultrasound device.

• Catheters that are not irrigated will reliably produce radial artery thrombosis if left in place for more than 40 hours. Most authors recommend leaving the catheter in place for no more than 12 to 18 hours.

• Pulse oximetry may provide normal values in the face of significantly compromised blood flow to the digits. It is therefore less valuable in identifying critical ischemia to the digits.

• When a radial artery catheter is in place, it should not be ignored. The site should be examined periodically. Circumferential bandages (including hospital identification bracelets) should be removed, and hypotension, vasoconstrictive drugs, and hypothermia should be avoided if at all possible. Any signs of ischemia or inflammation, such as redness at the site, loss of capillary refill or normal tissue color distally, or change in pulses in the wrist or palm, should prompt immediate removal of the catheter. Any failure of local changes to reverse within 1 hour should make surgical exploration of the artery a serious consideration.

slightly more distal and palmar than the deep arch (radial arch), is the primary blood supply to the ulnar three digits through its connections with the volar digital arteries. The deep arch comes off the radial artery, where this vessel drops down through the anatomic snuffbox and branches into the princeps pollicis artery (to the thumb). This large vessel to the index finger terminates at the deep palmar arch. In the usual circumstance, both arches connect to each other. The ulnar arch often terminates as a smaller diameter vessel that connects to a superficial branch of the radial artery, and the deep radial arch usually terminates in the ulnar palm by connecting to the ulnar arch via collateral vessels. There can be, however, great variability in the specific vascular networking within any given hand. For example, the median artery, which is present in fetal development, can occasionally persist as a major vessel and contribute additional blood flow to the two main arches. More importantly, the two main arches may exist as "incomplete" patterns, in which there are minimal connections between the radial and ulnar derived vascular trees in the palm. It is thought that an incomplete ulnar arch exists in ~20% of hands, and in this scenario the thumb and index finger derive most, if not all, of their blood supply from the radial artery (Fig. 25-4).

Identification of individuals at risk for radial artery cannulation injury, therefore, relies on noting the presence of incomplete arch vascular anatomy. Sometimes a history of cold intolerance in the hand provides a clue, although more commonly physical examination or vascular imaging is necessary. Simple physical examination can be remarkably helpful in identifying radial or ulnar artery dominance in the hand. The modified Allen's test involves manually occluding both vessels in one hand after the patient makes a tight fist several times to pump blood out of the hand. Then, with the patient's digits gently extended, the radial artery is released and the time

Radial Artery The Hand
Figure 25—4. An example of an "incomplete" vascular arch pattern, in which flow to the thumb and index finger are dependent on radial artery patency.

Up to 30% of thrombi may form a day or more after the catheter is removed from the radial artery. Therefore, careful observation for hand ischemia must be pursued for several days after the catheter is removed.

required for the palm to regain its normal color is noted. The test is then repeated, noting the refill time when the ulnar is artery released. Normal refill time is between 2 and 3 seconds. A positive Allen's test, or failure of palmar capillary refill in less than 4 or 5 seconds, is suggestive of incomplete arch vasculature. The vascular examination of the wrist and hand can be further worked up by a variety of more sophisticated methods, including Doppler ultrasound, pneumoplethysmography, and angiography. It should be noted, though, that the timed Allen is a remarkably simple and accurate screening test that can identify patients with incomplete palmar arches.

In addition to vascular anatomy, there are several other factors that seem to influence development of ischemia after radial artery cannulation. A smaller catheter, such as a 20-gauge size, seems to be less likely to produce thrombosis than a larger one (18-gauge). Teflon catheters that are irrigated regularly seem to produce less thrombosis-producing irritation than heparin-coated polyethylene catheters. Duration ofcatheter presence is also an issue. The longer the catheter is present, the more likely it is to produce occlusion of the vessel. One study showed that in catheters present for more than 40 hours, thrombosis was present in 93% of patients, compared with 25% for catheters removed at 20 hours or less.

In most cases, even if thrombosis of the radial artery occurs, the presence of complete vascular arches prevents critical ischemia from occurring in any particular part of the hand. Furthermore, in many cases, the thrombus is recanalized over time and does not cause any clinical symptoms. However, in patients with incomplete vascular arches, occlusion of the radial artery can produce total ischemia in one or several fingers (usually the thumb and index). Furthermore, medical conditions may be present that can further lower the threshold at which critical ischemia develops. Examples of such factors include hypotension, vasoconstrictive drugs, diabetes, peripheral vascular disease, coagulopathy, and Raynaud's phenomenon. Some authors have found that pretreatment with aspirin may reduce the incidence of thrombosis following radial artery catheterization.

In the clinical scenario described here, note that the patient was initially hypotensive, she received vasoconstrictive drugs, the catheter placed was an 18-gauge instead of a 20-gauge, and the catheter was in place for more than 3 days. All of these issues can have an impact on producing gangrene ifthe vascular arches are incomplete.

Surgical Management

A protective splint was applied to the hand to prevent trauma to the compromised digits. One week later, when the patient had been medically stabilized, a thumb and index finger amputation was performed. No further progression of necrosis had occurred since the original assessment, and a transproximal phalanx amputation was performed for the thumb. The index finger was treated with an amputation through the distal portion of the middle phalanx. Digital neurectomies were performed at the amputation sites. No infection was present. Mid-lateral incisions were used and direct closure via a "fish-mouth" type wound was possible with well-vascularized local soft tissue.

Postoperative Management

A forearm-based radial gutter splint was applied in the operating room and left in place for 1 week. Dressing change at that time demonstrated well-healing wounds with no evidence of infection or further soft tissue necrosis. Small individual dressings were applied to the thumb and index finger for 1 week. Occupational therapy was started with the first dressing change to aid in stump desensitization and proximal joint motion.

Alternative Treatment

The compromised hand due to radial artery thrombosis usually attracts attention after irreversible ischemic necrosis has occurred; consequently, amputation of dead tissue is the only remaining treatment option. However, if hand ischemia is identified very early, alternative therapies may be helpful. Such interventions include use of intravenous heparin or low molecular weight dextran, intermittent sympathetic block, and intraarterial administration of reserpine or papaverine. Methods to improve cardiac output may also be helpful. Ultimately, surgical intervention via thrombectomy and repair of the injured vessel segment may be necessary to avert gangrene of the radial digits.

Suggested Readings

Baker RJ, Chunpraprah B, Nyhus LM. Severe ischemia of the hand following radial artery catheterization. Surgery 1976;80:449-457.

Bedford RF. Radial arterial function following percutaneous cannulation with 18 and 20 gauge catheters. Anesthesiology 1977;47:37-39.

Bedford RF. Wrist circumference predicts the risk of radial-arterial occlusion after cannulation. Anesthesiology 1978;48:377-378.

Bedford RF, Ashford TP. Aspirin pretreatment prevents post-cannulation radial-artery thrombosis. Anesthesiology 1979;51:176-178.

Bedford RF, Wollman H. Complications ofpercutaneous radial-artery cannulation. Anesthesiology 1973;38:228-236.

Coleman SS, Anson BJ. Arterial patterns in the hand based upon a study of 650 specimens. Surg Gynecol Obstet 1961;113:409-424.

Crossland SG, Neviaser RJ. Complications of radial artery catheterization. Hand 1977;9:287-290.

Downs JB, Chapman RL, Hawkins IF. Prolonged radial artery catheterization. Arch Surg 1974;108:671-673.

Downs JB, Rackstein AD, Klein EF, Hawkins IF. Hazards of radial-artery catheterization. Anesthesiology 1973;38:283-286.

Ejrup B, Boguslav F, Wright IS. Clinical evaluation of blood flow to the hand. Circulation 1966;33:778-780.

Falor WH, Hansel JR, Williams GB. Gangrene of the hand: a complication of radial artery cannulation. J Trauma 1976;16:713-715.

Gelberman RH, Blasingame JP. The timed Allen test. J Trauma 1981;21:477-479.

Katz AM, Birnbaum M, Moylan J, Pellett J. Gangrene of the hand and forearm: a complication of radial artery cannulation. Crit Care Med 1974;2:270-272.

Lee KL, Miller JG, Laitung G. Hand ischemia following radial artery cannulation. J Hand Surg 1995;20B:493-495.

Levinsohn DG, Gordon L, Sessler DI. The Allen's test: analysis of four methods. J Hand Surg 1991;16A:279-282.

Mandel MA, Dauchot PJ. Radial artery cannulation in 1,000 patients: precautions and complications. J Hand Surg 1997;2:482-485.

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