Iatrogenic Ischemic Necrosis of the Thumb: A Case Report

Level of Evidence: Level V – Case Report Iatrogenic Ischemic Necrosis of the Thumb

Patient presentation:
A 41-year-old Caucasian female with a medical history of type II diabetes mellitus, hypertension, obstructive sleep apnea, morbid obesity (BMI 41), GERD, asthma, anxiety, and depression presented in septic shock, diabetic ketoacidosis, and anuric renal failure with hemodynamic instability and altered level of consciousness secondary to a two-week history of worsening right axillary MSSA abscess. The patient was intubated due to altered mental status, achieved hemodynamic stability with three vasopressors, and was taken to the operating room for right axillary abscess incision and drainage. She decompensated overnight, and continuous renal replacement therapy (CRRT) was initiated with arterial line placement in the patient’s right radial artery for hemodynamic monitoring. It is unclear whether placement of her arterial line contralateral to her known infection was considered.

The following morning, the patient’s right thumb appeared dusky in color with a nonpalpable radial pulse. The right radial arterial line was subsequently removed and a heparin drip was initiated. The implicated arterial line remained in place for approximately 17 hours in total. A vascular surgeon was consulted the following day, who noted that she was a poor surgical candidate given her overall clinical status and agreed with the decision to utilize a heparin drip. It is unclear whether thrombolytic therapy was discussed at this time. An arterial duplex ultrasound completed two days after arterial line removal noted occlusion of the right radial artery from the mid forearm to the level of the wrist, involving the lateral palmar arch on the thumb side.

While the patient’s overall condition stabilized, her thumb ischemia continued to worsen. Three days after the initial arterial line placement, she was transferred to another healthcare facility and orthopedic surgery was consulted. Activated partial thromboplastin time (aPTT) at that time was noted to be 34 seconds (reference, 22-31). Initial orthopedic physical examination of the right upper extremity revealed a large wound in the right axilla and a necrotic right thumb. The tip of the distal phalanx appeared black, dry, and shriveled with dusky mottling and significant blistering extending proximally over the thenar eminence and dorsal aspect of the hand in the distribution of the radial artery (Figure 1, A).

Figure 1: Outcomes of right thumb ischemia. A) Right thumb on admission, after approximately four days of ischemia, B-C) five days of ischemia, D-E) seven days of ischemia, F) 11 days of ischemia, G-H) 23 days of ischemia, I-J) 4 weeks after right thumb amputation.

Pulses were 2+ in the left upper and bilateral lower extremities with normal capillary refill <2 seconds. The right radial pulse was not palpable. Doppler ultrasound of the right upper extremity revealed audible blood flow in the ulnar artery, diminished flow in the index finger and the palmar arch as the probe moved radially across the third metacarpal, and complete lack of flow in the thumb and radial artery distal to the wrist. X-ray of the right hand and thumb revealed diffuse moderate soft tissue swelling with no underlying osseous lesions or evidence of acute traumatic injury. Digital blood pressures were normal in all digits except for the thumb, where no blood pressure was detected. Upper arterial duplex ultrasound of the right extremity revealed triphasic signals in the bilateral brachial, radial, and ulnar arteries with strong signals in the palmar arch and all digital arteries, except for the thumb, where Doppler flow was not visualized (Figure 2).

Figure 2: Results of right upper extremity digital blood pressures and upper extremity arterial duplex ultrasound.

At this point, the decision to amputate was made given her arterial occlusion and advanced necrosis of the thumb. The heparin drip was discontinued, 81 mg of oral aspirin daily was initiated, and the area of ischemia was allowed to fully declare itself. Angiography was unable to be performed in the inpatient setting given continued renal compromise.

In subsequent weeks, the patient’s right thumb continued to progress beyond previously demarcated borders, with further bullae formation on the dorsal surface of her hand and increased mottling extending proximally up the right arm (Figure 1, B-E). The patient’s overall clinical status otherwise continued to improve. Her urine output increased as her prerenal kidney injury resolved. She was extubated and weaned off oxygen support. Thumb wound cultures collected on admission remained negative with no organismal growth. She was ultimately discharged home and continued to follow in orthopedic clinic until the area of ischemia fully declared itself, approximately one month after her initial arterial line placement (Figure 1, F-H). Surgery was scheduled to amputate the right thumb, and a Tc-99m MDP nuclear bone scan of the hands was ordered for evaluation of bone integrity and surgical planning (Figure 3). The patient was taken to the operating room and the thumb was disarticulated to the level of the CMC joint with a partial resection of the trapezium. The procedure was tolerated well, with no complications and minimal blood loss. The patient was followed in clinic until complete resolution of her surgical wound, with ongoing discussion of prosthetic and surgical options to increase her functionality (Figure 1, I & J).

Figure 3: Results of Tc-99m MDP nuclear bone scan showed complete nonvisualization of the right proximal phalanx, distal phalanx, and mid and distal first metacarpal of the thumb in all 3 phases of imaging. The surrounding soft tissues of the right thumb were not visualized on blood pool and blood flow phase images. Mild hyperemia was noted in the right wrist, with normal uptake in remainder of the right and left hand.

Diagnosis and Treatment:
The differential diagnosis of digital ischemia is broad and includes a number of vasospastic, occlusive, and mixed etiologies that must be weighed against a number of patient-specific risk factors (Table 1). The rapid onset of ischemia, following placement of an ipsilateral radial artery arterial line, is suggestive of an occlusive, or vaso-occlusive etiology¹. The thumb is typically supplied by a single branch that stems from either the deep palmar arch or the radial artery, called the princeps pollicis artery (Figure 4). Therefore, isolated ischemia of the thumb may result from occlusion within or proximal to the origin of this terminal branch. Given the isolated distribution of ischemia to the thumb in this patient, one possibility is that she had an anatomical variation of the palmar arch such that the thumb was supplied solely by the radial artery^2-4.

Figure 4: Illustration of normal vascular anatomy of the right hand.

Differential diagnoses	Symptoms
Vasospastic (physiologic, pharmacologic) ●          Sympathetic stress-response ●          Raynaud’s phenomenon ●          Iatrogenic (vasopressors)	Acute onset, reversible, cold, pale-dusky digits ●          Systemic sympathetic symptoms (dilated pupils, tachycardia, hypertension, etc.) ●          Episodic, environmental triggers ●          All digits affected
Occlusive (embolic, thrombotic, perforation) ●          Coagulative (ITP, TTP, DIC, Factor V Leiden, SLE) ●          Infectious ●          Atherosclerosis ●          Traumatic ●          Iatrogenic (arterial cannulation)	Acute or chronic, painful, cold, pale-dusky digits, pulselessness ●          Systemic symptoms ●          Fever, leukocytosis ●          Progressive symptoms ●          Rapid onset, distinctive inciting event ●          Distinctive inciting event
Vasospastic-occlusive (mixed etiology)	Mixed

Table 1: Differential diagnosis and symptoms of radial artery ischemia.

This patient’s female gender, history of uncontrolled diabetes mellitus, altered mental status, acute septic state, arterial line placement, three vasopressor infusion requirement, and recent upper extremity surgery in the setting of right axillary infection all placed her at higher risk for iatrogenic radial artery injury^5,6. Therefore, highest on the differential diagnosis in this scenario are a catheter-associated thrombosis or septic embolization, leading to subsequent digital ischemia and related complications^7-12.

Prompt identification and workup is essential if there is concern for vascular compromise of a digit in the context of a recently placed arterial line. In such cases the arterial line should be immediately withdrawn, with urgent evaluation of the radial artery with Doppler or duplex-color ultrasound modalities to determine vascular status and an appropriate revascularization strategy (Figure 5)^13-15. This is a true medical emergency, as irreversible ischemic injury is imminent without prompt intervention.

Figure 5: Diagnostic and treatment algorithm for the patient with clinical signs of acute radial artery ischemia. Algorithm modified from Rutherford et al. 1997 classification of acute limb ischemia.

At the time of orthopedic surgery consultation, this critically ill patient with a 3-day history of unresolved digital ischemia presented a challenging clinical scenario with a significantly elevated risk of morbidity. Initial attempts at pharmacologic restoration of blood flow with heparin were unsuccessful and ischemia continued to progress. It is possible that there was an incorrect titration of heparin, as a larger aPTT value would be expected with a heparin drip. Vascular imaging and emergent revascularization were warranted upon immediate recognition of radial artery occlusion; however, the arterial duplex ultrasound was not performed until two days after recognition. In situations such as these, a low threshold for emergent revascularization must be maintained in the critically ill patient with acute digital ischemia, as symptoms suggestive of marginally and immediately threatened digits (i.e. pain, motor, and sensory deficits) may be masked by altered mental status. Although it is unclear whether interventional revascularization would have been possible for this patient given her critical condition, urgent vascular imaging may have helped identify the occlusive etiology and tailor treatment strategies accordingly. A thorough clinical exam, vascular studies, and imaging are required to determine the extent of ischemia and plan for intervention^14,15.

This patient’s physical examination and Doppler findings were ultimately consistent with dry gangrene secondary to thrombotic occlusion. Though this patient had a known right axillary abscess, the absence of digital infection lowered the suspicion for ischemia attributable to septic embolism, and lack of osseous lesions on radiography lowered the clinical suspicion for underlying osteonecrosis. Doppler findings of diminished blood flow radially over the palmar arch and the index finger, with complete lack of blood flow to the thumb, suggested a complete occlusion of the first digital artery.

Given the advanced presentation of this patient’s thumb necrosis, the decision was made to amputate. In the setting of a non-infected necrotic digit, it is imperative to let the zone of ischemia fully declare itself prior to amputation as to avoid multiple unnecessary procedures. Though not indicated in this patient due to her advanced presentation of tissue necrosis, tPA or thrombectomy should also be considered as an intervention in an attempt to salvage an affected digit after a thorough evaluation and discussion of risks and benefits¹⁴.

Discussion and Conclusions:
We present a case of iatrogenic ischemic necrosis of the right thumb secondary to arterial line placement in the right radial artery, ultimately leading to thumb amputation. It is unclear why the arterial line was placed ipsilaterally to the side of infection in this patient, as it is well known that this should be avoided if possible. This outcome could also have been avoided with the use of ultrasound prior to arterial line placement to evaluate vascular anatomy and confirm intact palmar arches, thereby ensuring an anastomosis through which blood could flow despite radial artery thrombosis^1,16,17. Ultrasound imaging is widely available, relatively inexpensive, and does not significantly delay care, making this an ideal modality for the evaluation of vascular anatomy.

This case was further complicated by delayed vascular imaging and potentially improper titration of initial heparin drip after the recognition of ischemia. It is also unclear whether thrombolytic therapy was considered, though it is likely this was deferred given the patient’s initial clinical status. In situations of known or suspected vascular injury, it is imperative that emergent further evaluation is completed, including a thorough physical examination, vascular studies such as Doppler and triphasic or color-Doppler ultrasound, and imaging such as a plain radiograph and CT or MR angiogram¹³. In this case there was adequate recognition of physical examination changes of thumb ischemia with prompt removal of the implicated arterial line and heparin drip initiation. However, there was a two-day delay to further imaging and a three-day delay before subsequent orthopedic consultation. This delay, in combination with likely improper titration of a heparin drip, led to advanced necrosis that was unsalvageable and ultimately resulted in right thumb amputation.

This case is complicated by several additional factors, including the myriad comorbidities of the patient, intubation and altered mental status, renal function preventing angiography, vasopressor requirement and infiltration, and initial care at an outside facility with subsequent transfer. It is possible that anatomic variations in the vascular supply to the thumb could have predisposed this patient to thromboembolic ischemia^2-4. Use of non-contrast angiography was considered in this case, though the Doppler and triphasic ultrasound findings coupled with physical exam findings were determined to be sufficient to elect for an amputation. Vascular collapse may have predisposed to arterial line placement complications and vasopressor infiltration in this patient^5,6.

Here we present an algorithm for management of acute radial ischemia adapted from guidelines for management of acute limb ischemia (Figure 5)¹⁵. Future patients can benefit from prompt identification and intervention to limit the extent and morbidity of critical digit ischemia and necrosis.

Conflict of Interest Statement:

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Statement of Human and Animal Rights:

This article does not contain any studies with human or animal subjects.

Statement of Informed Consent:

There is no highly identifiable personal information within this case report.

Statement of Funding:

The author(s) received no financial support for the research, authorship, and/or publication of this article.

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