Clinical

Underlying peripheral arterial or venous disease in patients with lower extremity SSTIs


 

2. There are signs and symptoms of underlying vascular disease in a patient with a lower extremity SSTI. Now what?

Neither PAD nor CVI is a clinical diagnosis, thus further work-up is required to confirm the diagnosis and accurately classify disease severity. The timing of this work-up is of unique interest to hospitalists.

Most patients who are hospitalized with cellulitis or a superficial wound infection do not need urgent inpatient work-up of suspected peripheral arterial or venous disease. The one notable exception to this is patients with diabetic foot infections or infected arterial ulcers that need prompt evaluation for possible critical limb ischemia. Barring cases of critical limb ischemia, the main objective of identifying PAD or CVI in patients hospitalized for SSTIs is to appropriately arrange testing and follow-up after discharge.

To address specific management strategies, it is useful to stratify patients by symptom and exam severity as follows: mild/moderate PAD symptoms without ulcer; infected ulcer with PAD features; mild/moderate CVI symptoms without ulcer; and infected ulcer with CVI features. As specific guidelines for the inpatient work-up and management of suspected peripheral arterial and venous disease are sparse, we rely on guidelines and best practices used in the outpatient setting and adapt them to these potential inpatient presentations.

Mild/Moderate PAD symptoms with superimposed cellulitis but no ulceration

In a patient admitted for cellulitis without open wounds, history and review of systems might reveal the presence of claudication or other symptoms suspicious for PAD. While the U.S. Preventative Services Task Force and American College of Cardiology discourages the routine screening of asymptomatic patients for PAD, patients with risk factors who endorse symptoms should undergo initial testing for PAD with an ankle-brachial index (ABI).10

The ABI is the ratio of ankle blood pressure to arm blood pressure, and is measured via sphygmomanometry with a Doppler probe. The ABI remains the simplest, most inexpensive first-line test for PAD. An ABI value of less than 0.9 is considered diagnostic for PAD and has been found to be more than 95% specific for arterial stenoses of greater than 50% on angiography across multiple studies.11

In an inpatient with risk factors for PAD and claudication symptoms, referral for outpatient ABIs with subsequent follow-up by a primary care physician should be arranged. If a diagnosis of PAD is made via ABI, the PCP should reinforce risk factor modification (tobacco cessation, diet, exercise, and aggressive lipid, blood pressure and blood glucose control) and start medical management with a single anti-platelet agent to reduce the risk of MI, stroke, or “vascular death.” The most recent ACC guidelines recommend either aspirin or clopidogrel as an acceptable anti-platelet agent (grade 1A).12 Cilostazol may be considered if claudication symptoms are significantly interfering with lifestyle. If this management fails, the patient may be referred to a vascular specialist for consideration of revascularization.

Infected ulcer with PAD features

Unlike cellulitis, arterial ulcers are a direct sequela of arterial insufficiency and represent the far end of the spectrum of disease severity and in certain cases treatment failure. Patients who present with advanced ischemic and/or diabetic foot ulcers may have never been evaluated for PAD as an outpatient. Prompt work-up and management is required given the high degree of morbidity and mortality associated with arterial ulcers. Whether an urgent inpatient evaluation is indicated depends on the clinical evaluation.

The first step is to determine the depth of the ulceration. Critical limb ischemia may be present if the ulcer is deep, gangrenous, overlies a bony prominence, or is associated with systemic signs of sepsis. A physical exam should include an assessment of the pulses including femoral, popliteal, PT and DP, preferably with bedside Doppler ultrasound. If pulses are absent, urgent vascular surgery evaluation is warranted to prevent loss of limb; the work-up generally involves imaging such as computed tomography angiography or magnetic resonance angiography to identify culprit lesions, or if sufficiently suspicious, immediate invasive angiogram with the potential for endovascular intervention.

While palpable pulses can be reassuring and raise the possibility of a nonarterial etiology of ulceration – such as a microvascular, neuropathic or venous disease – it is important to remember that pulse exams are often unreliable and provider dependent.13 Moreover, the presence of pulses does not effectively exclude severe PAD or critical limb ischemia in patients with a high pretest probability.14 Thus, in cases of deep, complex lower extremity and foot ulcers, it is prudent to obtain urgent evaluation by a surgical wound specialist, which depending on the institution may be podiatry, vascular surgery, or wound care. This may lead to a better clinical assessment of the wound and clearer recommendations regarding the need for additional testing, such as imaging, to rule out osteomyelitis, surgical debridement, or amputation.

Inpatient ABIs in this situation may help diagnose and quantify the severity of PAD. Newer classification schemes such as the Society of Vascular Surgery Wound Ischemia Foot Infection score take into account clinical findings as well as ABI scores to better prognosticate limb loss and select patients for intervention.15 If the clinical picture is deemed sufficiently suspicious for critical limb ischemia, the patient may be taken directly for invasive testing with possible intervention.

If an infected ulcer is superficial, shows no signs of gangrene, and has been present for less than 30 days, further work-up for suspected PAD can generally be deferred to an outpatient setting after resolution of the acute infection. Management of the wound is highly institution dependent. When available, a wound care specialist (physician or nurse) or a plastic surgeon can be consulted as an inpatient to give specific recommendations that can range anywhere from enzymatic debridement to simple dressing. If this service is unavailable, we recommend dressing the wound with moist nonocclusive dressings with frequent changes. Referrals for ABI testing and follow up in podiatry, wound care, or vascular clinic should be arranged. Finally, educating the patient on what to expect can increase compliance with the outpatient treatment plan.

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