Cannula-Associated Limb Ischemia Severity Score Predicts Need for Distal Perfusion Catheter Placement in Venoarterial Extracorporeal Membrane Oxygenation Patients

Identify risk factors and develop a predictive model for cannula-associated limb ischemia requiring distal perfusion cannula (DPC) placement in venoarterial extracorporeal membrane oxygenation (VA-ECMO) patients. Single-center retrospective review of all consecutive patients who underwent peripheral VA-ECMO from 2016 to 2019. Patients were excluded if ECMO duration was <24 hours or if they underwent prophylactic DPC placement during time of cannulation. Clinical factors including laboratory shock markers, abnormal postcannulation computed tomography angiogram (CTA), limb near infrared spectroscopy (NIRS) discrepancy, and limb examination discrepancy were compared between patients requiring DPC placement to those who did not. Laboratory shock markers were defined as initial lactate ≥4 mmol/L and pH ≤7.2. Abnormal postcannulation CTA was defined as diminished or absent arterial contrast opacification distal to the arterial cannula. Limb NIRS discrepancy was defined as ≥25% rSO2 saturation discrepancy relative to contralateral limb. Limb examination discrepancy was defined as two or more abnormal physical examination findings (absent dorsalis pedis signal, absent posterior tibial signal, capillary refill of >2 seconds, edema, motor deficit, sensory deficit, or pallor) not present in contralateral limb. Fifty-four patients were included for analysis (35 males, 19 females; mean age, 55.9 ± 13 years), of whom 17 (32%) underwent DPC placement. Thirty-three patients (61%) survived VA-ECMO and 27 (50%) survived to discharge. Using selective DPC placement, there was a 0% incidence of limb amputation. One patient (1.8%) developed cannula-associated limb ischemia with persistent ischemic changes despite DPC placement; however, the patient did not survive ECMO. Patients with positive laboratory shock markers (n = 22) were significantly more likely to undergo DPC placement compared to those without (n = 32) (11 [50%] vs 6 [19%]; P = .0198). Patients with abnormal postcannulation CTA (n = 4) were significantly more likely to undergo DPC placement compared to those without (n = 25) (4 [100%] vs 2 [8%]; P = .006). All patients with unilateral limb NIRS discrepancy (n = 4) underwent DPC placement, whereas all patients without limb NIRS discrepancy (n = 15) did not undergo DPC placement (4 [100%] vs 0 [0%]; P = .0003). Patients with limb examination discrepancy (n = 15) were significantly more likely to undergo DPC placement compared to those without (n = 39) (15 [100%] vs 2 [5%]; P < .0001). Using the above clinical factors, we have derived the Cannula-associated limb ischemia severity score (CALIS score), to predict VA-ECMO patients that will benefit from selective DPC placement (Table). Cannula-associated limb ischemia requiring DPC placement can be predicted with high-fidelity using the CALIS score and was associated with no limb loss in our study.TableCannula-associated limb ischemia severity score (CALIS score)CategoryDefinitionPointsLaboratory shock markersLaboratory markers during VA-ECMO cannulation with lactate ≥4mmol/L and pH ≤ 7.21Abnormal postcannulation CTACTA obtained after VA-ECMO cannulation demonstrating diminished or absent arterial contrast opacification distal to arterial cannula2Limb NIRS discrepancyNIRS discrepancy in which there is ≥25% rSO2 saturation discrepancy relative to contralateral limb2Limb examination discrepancyLimb exam with ≥2 abnormal physical examination findings (absent dorsalis pedis signal, absent posterior tibial signal, capillary refill >2 seconds, edema, motor deficit, sensory deficit, or pallor) not present on contralateral limb2Scoring: 0 points: Low probability for cannula-associated limb ischemia. No need for DPC placement. 1 point: Intermediate probability for cannula-associated limb ischemia. Have low threshold for DPC placement. ≥2 points: High probability for cannula-associated limb ischemia. Recommend DPC placement.CTA, Computed tomography angiography; DPC, distal perfusion catheter; VA-ECMO, venoarterial extracorporeal membrane oxygenation. Open table in a new tab