Angiographic evaluation of lower extremity acute limb ischemia in an extracorporeal membrane oxygenation patient using bedside portable radiograph

Abstract

A 47-year-old patient was emergently placed onto venoarterial extracorporeal membrane oxygenation on postoperative day 1 after coronary artery bypass surgery for refractory ventricular tachycardic arrest. The patient subsequently lost pulses in the right lower extremity and was too unstable to be transported for a computed tomography scan or to the hybrid operating room for an angiogram. Bedside administration of contrast via the perfusion sheaths with concurrent portable radiograph allowed for imaging of the right lower extremity vasculature to assess for patency. This technique can facilitate rapid diagnosis and decision-making in a critically ill patient, avoiding high-risk transportation and/or unnecessary vascular procedures.

Venoarterial extracorporeal membrane oxygenation (VA ECMO) has become increasingly common as a means of temporary circulatory support in patients with severe acute cardiogenic shock.¹ Although several configurations of drainage and return cannulas for the ECMO circuit have been described, the common femoral artery and common femoral vein are most often most often used as first-line access options in VA ECMO.^1,2 Owing to the large diameter of the cannulas, occlusion of the access vessels is unfortunately quite common.1, 2, 3, 4 To mitigate this, a perfusion sheath may be placed in the ipsilateral superficial femoral artery to maintain antegrade perfusion to the lower extremity. Despite the placement of an antegrade perfusion sheath, distal ischemic complications have been reported in up to 70% of patients placed on VA ECMO.1, 2, 3 Owing to the critical status of these patients, transportation out of the intensive care unit (ICU) and advanced imaging with computed tomography angiography or angiography in a hybrid suite is not always feasible. Therefore, options for evaluating the lower extremity vasculature at the bedside rapidly are important tools and include Doppler signal evaluation, arterial duplex, and near infrared spectroscopy to assess for distal tissue oxygenation.^2,3,5,6 Although these tools serve an important role in identifying issues with distal perfusion, they are not always adequate for an accurate diagnosis of the etiology of the ischemia. Angiography remains the gold standard in cases of suspected distal malperfusion.

With consent for publication obtained from the patient per our institution's policies, we report the case of a critically ill patient who required emergent initiation of VA ECMO support and subsequently developed concerns for acute limb ischemia. Bedside angiography using iodinated contrast and sequential plain-film radiograph was performed via the profunda femoris and superficial femoral artery perfusion sheaths for rapid diagnosis and management.

Case report

A 47-year-old woman with a past medical history relevant for type 2 diabetes, hypertension, and peripheral artery disease was transferred to our institution for coronary artery bypass graft (CABG) evaluation. She underwent an uncomplicated three-vessel CABG with cardiothoracic surgery and was extubated postoperatively in the ICU on postoperative day 0. On postoperative day 1, she developed sustained ventricular tachycardia and subsequently went into pulseless ventricular tachycardia/ventricular fibrillation prompting cardiopulmonary resuscitation without return of spontaneous circulation. She was intubated for respiratory failure and emergently placed onto VA ECMO at the bedside.

A 15F return cannula was placed in the right common femoral artery and a 25F drainage cannula was placed in the right common femoral vein. Bedside cannulation of the right superficial femoral artery for the return cannula was unsuccessful, and the patient converted to sinus bradycardia after the VA ECMO circuit was initiated. She was then taken for cardiac catheterization, which demonstrated patency of all three CABG grafts and a decreased ejection fraction of 30%. The interventional cardiologists subsequently placed a 5F perfusion sheath antegrade in the right superficial femoral artery after first erroneously accessing and placing a 5F perfusion sheath antegrade in the right profunda femoris artery.

The patient's right lower extremity dorsalis pedis and posterior tibial Doppler signals were no longer able to be obtained by the ICU team after being started on VA ECMO; therefore, vascular surgery was consulted. Investigation of the profunda femoris perfusion sheath demonstrated good back-bleeding; the superficial femoral artery perfusion sheath yielded return of a clot on initial aspiration. Bedside arterial duplex ultrasound examination was performed using a portable ultrasound machine in the ICU, which demonstrated color flow with monophasic waveforms in the superficial femoral artery distal to the perfusion cannula. In the below-knee popliteal artery, color flow was no longer visible and only a faint waveform could be obtained on power Doppler ultrasound examination in the below-knee popliteal artery and tibial vessels. Although the motor/sensory status of the patient's right lower extremity could not be evaluated owing to intubation and sedation, there was a high index of suspicion for thromboembolism causing acute limb ischemia given the return of a clot from the superficial femoral artery perfusion sheath, with bedside ultrasound examination demonstrating severely limited flow in the below knee popliteal and tibial arteries.

Discussion was held with the ICU and cardiothoracic surgery teams regarding switching to a central VA ECMO cannulation via repeat sternotomy while removing all cannulas and sheaths from the femoral vessels and performing an angiogram with possible intervention in the hybrid operating room. Monitoring the patient and potentially allowing for demarcation of the limb before amputation further down the line was discussed as well, but all teams participating in her care felt her young age warranted further workup and aggressive measures. Owing to increasing pressor requirements, it was not immediately obvious on bedside ultrasound examination whether her vessels were completely occluded or severely spasmed distally, however, and more definitive imaging and clinical data was needed before performing such a large and high-risk surgical intervention on this acutely critically ill patient.

A portable x-ray machine was called to bedside because a mobile C-arm is not compatible with ICU beds. The machine was positioned over the right thigh and several static images were taken shortly after the administration of Isovue contrast through the superficial femoral artery perfusion sheath and the profunda femoris perfusion sheath (Fig 1, Fig 2, Fig 3, Fig 4). Images taken in the proximal leg near the perfusion sheaths were taken immediately after contrast administration via the superficial femoral artery and profunda femoris artery perfusion sheaths, whereas the distal lower extremity images were taken several seconds after contrast administration through the superficial femoral artery sheath to allow for adequate contrast circulation. A total of 100 mL of nondiluted Isovue contrast were administered via the perfusion sheaths to obtain static images at all levels of the lower extremity. The images ruled out flow-limiting dissection or occlusion of the lower extremity vasculature, rather demonstrating distal tibial vessel tapering with limited distal perfusion of the foot, likely owing to multipressor shock and vasospasm. The below-knee popliteal artery of concern on the bedside ultrasound examination was patent without any stenosis or occlusion with inline flow to all three tibial vessels that tapered out uniformly down by the ankle, thereby definitively ruling out any thromboembolic phenomenon from the VA ECMO circuit sheaths and cannulas. The profunda femoris was also able to be imaged via the perfusion sheath, demonstrating a widely patent vessel with distal branches able to visualized as well. As a result of these imaging findings, transport of this critically ill patient was able to be avoided, and a diagnosis was obtained allowing for continued supportive care without pursuing unindicated, high-risk surgical intervention. The patient was ultimately weaned off pressor with return of Doppler signals to the foot, and was successfully ramped down on the VA ECMO circuit to allow for decannulation. She required tracheostomy and percutaneous endoscopic gastrostomy tube placement, but ultimately survived the hospitalization and was discharged to a long-term care facility.

Fig 1.

Superficial femoral artery static angiogram image after administration of contrast via the superficial femoral artery perfusion sheath.

Fig 2.

Distal superficial femoral artery and popliteal artery static angiogram image after administration of contrast via the superficial femoral artery perfusion sheath.

Fig 3.

Tibial vessels static angiogram image after administration of contrast via the superficial femoral artery perfusion sheath.

Fig 4.

Profunda femoris artery static angiogram image after administration of contrast via the profunda femoris perfusion sheath.

Discussion

VA ECMO is increasingly being used in the treatment of acute severe cardiac and cardiopulmonary shock.^1,4,5 Large-bore access complications are common, and perfusion sheaths do not obviate these concerns.1, 2, 3^,5, 6, 7 This case serves to illustrate a bedside technique that can be used to diagnose the etiology of distal malperfusion and potentially limit dangerous transport and/or unnecessary procedures.

Although other bedside techniques and imaging modalities can be performed, this case highlights the importance of using multiple adjuncts and correlating imaging findings with clinical status, in this case the possibility of pressor-induced vasospasm despite ultrasounds findings concerning for occlusion. Angiography remains the gold standard for evaluation of the arterial tree of the lower extremity, and this bedside technique serves as a rapid and easily obtainable alternative to traditional fluoroscopic angiography. Although this technique has been described before,⁴ it is not used routinely at our institution. We anticipate using it again in the future to address similar cases.

Conclusions

In a critically ill patient on VA ECMO with concerns for acute limb ischemia, bedside portable angiography after contrast administration via perfusion sheaths serves as a rapid tool for distal vasculature evaluation. This serves as a readily obtainable imaging modality for assisting in collaboration between vascular surgery and ICU teams for guiding management of patients on VA ECMO.

Funding

None.

Disclosures

None.