New strategy for distal limb perfusion in veno-arterial extracorporeal membrane oxygenation treatment: application of continuous renal replacement therapy tubing

Extracorporeal membrane oxygenation (ECMO) is a technology that can temporarily take over the functions of the heart and lungs. Acute kidney injury is a common issue in patients receiving ECMO treatment, with reported incidence rates ranging from 70% to 85%.[1] To maintain the balance of fluids and electrolytes in patients, continuous renal replacement therapy (CRRT) is frequently employed.

Following the onset of peripheral veno-arterial extracorporeal membrane oxygenation (VA-ECMO), acute limb ischemia has become a worrisome complication with significant implications for patient prognosis and survival.[2] It can lead to insufficient blood flow to the affected limb, potentially culminating in limb amputation or death in severe cases.[3] According to the current literature, the incidence rate of limb ischemia is approximately 17%.[4] Acute limb ischemia is typically linked to various factors, including patient comorbidities, hemodynamic factors resulting in low flow rates, and the size of catheters inserted.[5] Early detection, prevention, and management of this severe complication are imperative for emergency medicine and intensive care specialists. The attainment of successful distal limb perfusion is paramount for preventing acute limb ischemia among patients undergoing VA-ECMO.[6]

Hence, the placement of a distal perfusion catheter during VA-ECMO is highly important. In clinical settings, a 6F–8F distal infusion arterial sheath is commonly inserted to mitigate this complication. However, this approach often necessitates the use of additional extension tubing. Certain ECMO kits, such as Cardiohelp (Getinge, Sweden), do not include the requisite distal infusion extension tubing, with most ECMO kits providing only one connecting tube. Currently, all distal limb perfusion catheters lack the ability to precisely regulate blood flow in the lower limbs. To address this issue, we propose a novel method using CRRT tubing and flow control to provide precise management of blood flow to the distal limbs. The connection approach is illustrated in Figure 1, where oxygenated blood is redirected through the CRRT tubing into a blood filter before being reconnected to a 6F arterial sheath for perfusion of the distal limbs (e.g., perfusion of the lower limbs via the superficial femoral artery). Moreover, the ultrasound may be used to assess the blood flow velocity in the lower limbs, with the CRRT blood flow rate adjusted accordingly.

Figure 1.

The adjustment of extracorporeal membrane oxygenation (ECMO) distal perfusion employing a continuous renal replacement therapy (CRRT) apparatus in veno-arterial ECMO for precise control of blood flow to the distal extremities. A fraction of oxygenated blood is directed into the CRRT circuit to regulate fluid levels and maintain electrolyte balance. Subsequently, the blood is re-infused into the superficial femoral artery to deliver oxygen-enriched blood to the distal extremities.

Therefore, the CRRT circuit serves two purposes: 1) to maintain fluid and electrolyte balance to stabilize the internal environment; and 2) to serve as part of the VA-ECMO distal perfusion mechanism, allowing precise regulation of blood flow to the distal limbs.

One limitation of this method is that alterations in blood flow within the CRRT device may impact fluid removal efficiency. Additionally, incorporating the CRRT circuit after the oxygenator in the veno-arterial circuit could increase the risk of air or blood clots in the lower limbs. Since this method is merely an alternative in situations where adequate equipment is not available and has not undergone extensive multicenter clinical investigation, it serves solely as a reference.