Peter K. Henke
John W. Rectenwald
Presentation
A 68-year-old active man presents to the emergency room (ER) with a 4-hour history of right limb pain and numbness. He had fallen out of bed and noticed worsening limb symptoms ever since. He notes no prior leg problems and no history of claudication. His past history is significant for a myocardial infarction 7 years ago and subsequent CABG. Past medical history includes tobacco use and hypertension but no diabetes or stroke. Medications include an aspirin, a calcium channel blocker, and a statin agent. He was able to ambulate with assistance into the car and ER but now has a difficult time moving his foot due to pain and neurologic impairment.
Differential Diagnosis
At this point, lower limb etiologies include direct trauma and possible fracture, deep vein thrombosis, spinal cord compression, and arterial ischemia.
Evaluation
Physical Examination
On exam, his cardiac rhythm is irregularly, irregular with a rate of 130, BP = 130/90, and RR = 20. His abdomen is soft and nontender. Pulse exam is +2/4 of radial, left femoral, and pedal pulses, right femoral +3/4, but 0/4 for right popliteal and pedal pulses. He has a normal neurologic exam on the left. He has diminished sensation below the knee on the right and decreased foot dorsiflexion, associated with coolness. No external trauma is noted, and no swelling is noted in either limb.
Presentation Continued
Acute limb ischemia (ALI) is a common vascular emergency that all physicians should be able to recognize and treat in a timely fashion (Figure 1). Delays in diagnosis and lack of anticoagulation are causes of limb loss in ALI. At this point, the history and PE give a clear picture of ALI. In this case, lack of external trauma, swelling, and DVT makes fracture less likely. Nerve root compression is possible but would usually be associated with a distinctly different neurologic exam usually involving a whole-leg motor deficit. The most significant find ing suggesting ALI is that he has a total pulse deficit below the femoral artery on the symptomatic side but a normal exam on the nonaffected side. This patient has several of the “6” “P’s” of ALI, namely parathesis, pulselessness, poikliothermia, and paralysis. According to the Society for Vascular Surgery (SVS) limb ischemia grading system, he has a level IIb ischemia and requires rapid revascularization to save his leg.
Laboratory/EKG
As comorbid diseases and conditions account for much of the mortality of ALI, it is important to evaluate for common problems that may compromise the patient acutely. These are primarily cardiac and renal diseases, including a potential for hyperkalemia, anemia, and acute myocardial infarction after ischemia reperfusion injury. Standard blood assessment includes CBC, electrolytes, BUN, creatinine, troponin, and CPK. A baseline CXR is optional.
Other Imaging and Noninvasive Tests
These should not delay definitive treatment, the urgency of which is dictated by the history and PE findings. If immediately available, duplex ultrasonography can image the arterial flow and demonstrate the location and extent of the occlusive embolus. An echocardiogram, if rapidly available, may also be useful for confirming presence of cardiac thrombus and overall function, but is not necessary preoperatively and should not delay revascularization. An ankle brachial index can be done as well, but in most cases of true ALI, is zero.
Therapy
Medical
Hydration with normal saline is standard practice. Urine output should be monitored, with a goal of at least 1 mg/Kg/h. An oral aspirin should be administered, and a heparin bolus given, approximately 80 U/Kg, followed by 18 U/Kg/h continuous infusion for a goal aPTT 2 to 2.5× baseline. It is common for patients with ALI to have multiple acute medical problems that must be treated appropriately, and saving life before limb is paramount. First and foremost is evaluation and stabilization of cardiac issues, and ensuring adequate renal clearance.
FIGURE 1 • Diagnostic and therapeutic algorithm for a patient who presents with ALI.
Interventional
The most likely etiology of ALI in this case is a cardiac embolism, and the lower extremity is the most common site of origin in general. Other etiologies include thrombosis in situ (such as a graft thrombosis) or peripheral aneurysms, trauma, and aortoiliac dissection. Arteriography with thrombolysis is an option, but given the patient’s classic history for an arterial thromboembolism (an antecedent cardiac event, lack of history of claudication, and normal vascular exam on his contralateral asymptomatic leg), this step may delay reperfusion achieved more readily with surgery. For cases where the etiology is not clear or points toward a nonembolic etiology (e.g., graft thrombosis or occluded aneurysm), proceeding to the arteriogram suite is best.
Procedural Basics
A longitudinal incision in the groin (or in the medial upper thigh, or below the knee, depending on the clinical circumstances) is made and the femoral artery is exposed to include the common, deep, and superficial femoral artery. These are controlled with vessel loops. After ensuring the patient’s ACT is >250, the loops are secured and the artery opened transversely if not significantly diseased. After adequate pulsatile arterial inflow is established by embolectomy, attention is turned to the distal thrombectomy. The use of the embolectomy catheter relies on the catheter traversing a thrombus, and pulling it out with gentle inflation of the balloon, in a continuous motion. The typical sizes are 4 and 5 for larger arteries, such as femoral and iliacs, and smaller with 2 and 3 size for distal arteries. After ensuring adequate back bleeding and having passed the catheter at least twice without retrieving thrombus, the arteriotomy is flushed with heparinized saline and closed with nonabsorbable suture in an interrupted fashion. Blood flow is reestablished to the distal limb, and Doppler signals are checked.
When the etiology of ALI is not clear by history and physical exam, arteriography with thrombolysis or catheter-assisted extraction is the best option (Figures 2 and 3). Versatile equipment in well-outfitted endovascular, hybrid rooms includes over-the-wire embolectomy catheters, suction embolectomy catheters, and high-resolution C-arm fluoroscopy that allows concurrent endovascular and open techniques. This scenario will likely be the standard in the next 5 years. Proper case selection is essential, as failed lysis or frivolous persistence at endoluminal approaches confers a significantly increased risk of limb loss and death. Thrombolytic agents may cause a systemic fibrinolytic state and potentially release thrombus from the atrium or ventricle and may cause a stroke or other complications. Thus, an echocardiogram should be obtained prior to beginning thrombolysis if the suspected source of the embolus is intracardiac.
FIGURE 2 • A: Appearance of a patient with underlying mild peripheral arterial disease who presented with severe right lower ischemia. B: Later DSA arteriogram after 5 mg of tPA intra-arterially. C: Shows wire traversal and approximately 8 hours after thrombolytic started with opening of tibial vessels. This patient went on to have full resolution, with the underlying etiology thought to be a hypercoaguable state.
It is important to continue therapeutic heparin throughout the case, as well as maintain adequate hydration. Determining a postoperative CPK and urine myoglobin may aid with resuscitation. Consideration of a four-compartment fasciotomy to treat postreperfusion compartment syndrome should be given to any patient with ALI greater than 6-hour duration, as the morbidity is low. With good wound care, these can often be closed by delayed primary closure.
Routine follow-up with history and physical exam, but no specific imaging protocol, is needed for the affected and contralateral limb if palpable pulses returned. Standard cardiovascular risk factor modification therapies should be pursued.
Presentation Continued
Laboratory evaluation reveals a normal hematocrit (HCT) of 38, and a normal BUN/Cr, and potassium. An EKG shows atrial fibrillation with no obvious ST elevation or depression. Baseline CPK is elevated at 1,000. The patient also denies any chest pain and a rapid troponin I level is within normal limits. Thus, it is unlikely he has suffered a recurrent major myocardial infarction. His urine output is greater than 30 mL/h. If his blood pressure tolerates it, an intravenous (IV) beta-blocker or calcium channel blocker is reasonable with his tachycardia.
The embolic location is likely below the femoral artery as his femoral is normal (if not prominent), and no pulses or signals are present distally. The patient needs revascularization within 1 to 2 hours, as it is likely he has had approximately 4 hours of total ischemia, or he may suffer permanent muscle and nerve damage, rendering a nonsalvageable limb. As this patient has critical late ischemia, surgical embolectomy is the most appropriate means to rapidly restore limb blood flow, as compared with thrombolysis, which may take several hours before adequate reperfusion.
FIGURE 3 • This patient with modest bilateral PAD presented with ALI and underwent percutaneous suction catheter embolectomy for ALI. A: The arteriogram shows a complete thrombotic obstruction at the distal popliteal artery. B,C: A five French guide catheter is advanced into the thrombus with aspiration, followed by pulsed infusion of thrombolytic agent. Repeat arteriogram shows opening of the tibial-peroneal trunk and tibial vessels. D: Completion arteriogram with tibial vessels showing arterial patency and no evidence of distal thromboemboli.
After cardiac rate control and heparinization, he is taken to the operating room and both lower extremities are prepped and draped to allow potential inflow site, as well as vein for conduit, should these be necessary. An open thromboembolectomy via a femoral approach under local anesthesia with IV sedation is performed. Pedal signals are present at close. The patient undergoes four-compartment fasciotomy.
Discussion
Several important issues with ALI should be kept in mind; first, major errors occur with lack of timely diagnosis, anticoagulation, documentation of the exam pre- and postoperatively, and focusing too much on the limb salvage at the expense of the life (Table 1). Second, the same principles hold if the patient presents with upper-extremity ALI. The operative approach is usually the medial distal brachial artery in the upper arm, or at the confluence of the radial and ulnar in the forearm. Third, recurrent on table or early recurrent ALI suggests an incomplete thrombectomy, or a persistent nidus of thromboembolism. For this, it is important to proceed with an on-table angiogram to visualize the inflow anatomy. Similarly, if no signals are present after reestablishing blood flow to the limb (after full embolectomy), an arteriogram is best for imaging the outflow. An intraoperative thrombolytic agent can be given (e.g., 10 mg tPA) intra-arterially and/or vasodilator, nitroglycerin (50 to 100 µg), may be helpful. Fourth, never force the embolectomy catheter in the artery, as dissection of the artery is a major problem that often requires endoluminal techniques or an open bypass to repair. Lastly, ALI in the setting of trauma is particularly challenging because of the disrupted operative field with limited, if any, soft tissue graft coverage, the frequent inability to give heparin, and the common need to perform a bypass rather than simple embolectomy. In these cases, proceeding as expeditiously without heparin or local small doses is reasonable.
TABLE 1. Acute Limb Ischemia Pitfalls
Case Conclusion
Postoperatively, the patient was maintained on heparin and then systematically anticoagulated with a vitamin K antagonist for 3 months. He was also discharged on a beta-blocker for heart rate control with early follow-up with his local cardiologists. Reassessment can be done at that time in relation to source control; that is, if he is in sinus rhythm and his ECHO shows no thrombus, it is reasonable to stop the anticoagulation at this time. His fasciotomy sites were closed by delayed primary closure on his initial inpatient admission, and his mild foot drop has since resolved.
TAKE HOME POINTS
· Early recognition of ALI is critical.
· Determine the site of occlusion based on exam and ease of anatomical exposure.
· Don’t limit your therapy options; consider contrast imaging intraoperatively if available.
· Start with the small catheter first, followed by a larger embolectomy catheter and don’t force the catheter if encountering persistent obstruction.
· Any of the embolectomy procedures can be done under local anesthesia to minimize cardiovascular stress.
· Don’t hesitate to proceed to a distal arterial exposure if thrombosis is extensive.
· Always pass a thrombectomy catheter proximally—regardless of inflow. A lesion proximally may be the source of thromboemboli.
SUGGESTED READINGS
Eliason JL, Wainess RM, Proctor MP, et al. A national and single institutional experience in the contemporary treatment of acute lower extremity ischemia. Ann Surg. 2003;238:382–390.
Henke PK. What is the optimum perioperative drug therapy following lower extremity vein bypass surgery? Semin Vasc Surg. 2009;22:245–251.
Ouriel K, Veith FJ, Sarahara AA. A comparison of recombinant urokinase with vascular surgery as initial treatment for acute arterial occlusion of the legs. N Engl J Med. 1998;338:1105–1111.
Palfreyman SJ, Booth A, Michaels JA. A systematic review of intra-arterial thrombolytic therapy for lower limb ischemia. Eur J Vasc Endovasc Surg. 2000;19:143–157.
Panetta T, Thompson JE, Talkington CM, et al. Arterial embolectomy: a 34-year experience with 400 cases. Surg Clin N Am. 1986;66:339–352.
Rutherford RB, Baker JD, Ernst C, et al. Recommended standards for reports dealing with lower ischemia: revised version. J Vasc Surg. 1997;26:517–538.