Peripheral VA-ECMO #1: Cannulation Strategy

Peripheral veno-arterial extracorporeal membrane oxygenation (VA-ECMO) is an emergency mechanical circulatory support modality used to restore systemic perfusion and oxygen delivery in patients with severe cardiac or cardiopulmonary failure. Compared with central cannulation, peripheral access can often be established more rapidly and in a wider range of settings, including the intensive care unit, emergency department, and operating room. However, the choice of cannulation site is not simply a matter of technical convenience. It is a major determinant of support physiology because it shapes arterial flow direction, left ventricular (LV) loading conditions, and the regional distribution of oxygenated blood to the brain, heart, abdominal organs, and extremities [1,5].

1. Core principle

The immediate purpose of peripheral VA-ECMO is to drain systemic venous blood, oxygenate it extracorporeally, and return it to the arterial circulation quickly enough to restore end-organ perfusion. Once support begins, however, the physiologic consequences become configuration-dependent. In practical terms, the cannulation strategy influences three interrelated domains:

1. Flow direction
• whether arterial reinfusion is delivered more centrally or in a retrograde fashion against native aortic flow
2. Ventricular loading
• especially whether arterial return increases LV afterload and predisposes to aortic valve non-opening, pulmonary edema, and LV distension
3. Regional perfusion
• particularly cerebral oxygenation, coronary oxygen delivery, and distal limb perfusion [1,5,6]

For this reason, cannulation should be viewed not merely as “access,” but as the first major hemodynamic decision in VA-ECMO management.

2. Neck cannulation

2.1 Basic configuration

Neck cannulation most commonly uses the right internal jugular vein for venous drainage and the right common carotid artery for arterial return. This remains a common peripheral VA-ECMO strategy in neonates and small infants, particularly when femoral vessels are too small to provide safe and effective support [1,3].

2.2 Why it is favored in smaller patients

In neonatal and infant ECMO, the cervical vessels offer several practical advantages:

• direct surgical exposure
• vessel caliber that is often more suitable than the femoral vessels
• rapid initiation of support
• central arterial reinfusion without dependence on small distal lower-extremity vessels

Accordingly, cervical cannulation remains highly relevant in pediatric practice, even as femoral access has expanded in larger children and adolescents [1,3].

2.3 Neurologic and vascular considerations

The principal concern with neck cannulation is not support adequacy, but the implications of carotid artery sacrifice, reconstruction, or long-term patency. Contemporary evidence suggests that practice variation remains substantial, even among larger children, and the relationship between carotid cannulation and neurologic injury is more nuanced than earlier unadjusted analyses suggested [1,2]. Large registry-based analyses have shown that although crude neurologic event rates may appear higher with carotid access in some cohorts, adjustment for age, diagnosis, and illness severity attenuates this association, and carotid cannulation has not consistently emerged as an independent predictor of stroke [2].

Thus, current interpretation is more balanced: carotid access should not be assumed to be inherently inferior, but it requires deliberate attention to neurologic monitoring, technical precision at decannulation, and follow-up of cervical vessel management. In small pediatric patients, these trade-offs are often acceptable because the anatomic alternatives may be limited [1,2].

2.4 Practical teaching point

Neck cannulation is usually the most anatomically natural peripheral VA-ECMO strategy in neonates and small infants. Its value lies in size-appropriate access and central reinfusion rather than in any universal superiority across all age groups.

3. Femoral cannulation

3.1 Basic configuration

Femoral peripheral VA-ECMO generally uses the femoral vein for drainage and the femoral artery for arterial return. In larger children, adolescents, and adults, this is often the most widely applicable peripheral configuration because it allows rapid deployment and broad procedural familiarity [3,5].

3.2 Major physiologic feature: retrograde aortic flow

The defining hemodynamic consequence of femoral arterial return is retrograde flow up the descending thoracic aorta toward the aortic arch and root. This has major clinical implications. Because the ECMO circuit is pushing blood retrograde into the arterial tree, femoral VA-ECMO may substantially increase aortic pressure and LV afterload. If native LV function is poor, this can reduce or abolish aortic valve opening, elevate LV end-diastolic pressure, worsen left atrial hypertension, promote pulmonary edema, and impair myocardial recovery [5,6].

This afterload penalty is central to understanding why a technically successful femoral cannulation may still require early downstream adjustments in support strategy.

3.3 LV distension and the need for unloading

One of the most important contemporary concepts in VA-ECMO management is that LV distension should be anticipated early rather than treated only after overt deterioration. Warning signs include:

• minimal or absent aortic valve opening
• increasing LV size
• rising left atrial or pulmonary venous pressures
• pulmonary edema
• spontaneous echo contrast or stasis in the LV or aortic root

Modern practice increasingly favors early recognition of patients who may require adjunctive unloading. Depending on age, anatomy, and institutional approach, this may include ventilator optimization, afterload reduction, atrial decompression, surgical venting, transseptal strategies, or adjunct devices in appropriate larger patients [6].

3.4 Differential upper-body hypoxemia

Femoral VA-ECMO also creates the possibility of differential hypoxemia when native cardiac output recovers while pulmonary gas exchange remains poor. In this setting, the heart ejects relatively desaturated blood antegrade into the ascending aorta, while the ECMO circuit continues to deliver well-oxygenated blood retrograde from the femoral artery. The result is a mixing point somewhere in the aorta, with the upper body, brain, and coronary arteries potentially receiving less oxygenated blood than the lower body [7].

This phenomenon is especially important because the myocardium and brain are the very territories one most wants to protect. Right upper-extremity saturation and right radial arterial blood gas monitoring therefore assume particular importance during femoral VA-ECMO [7].

3.5 Distal limb ischemia

The major access-related complication specific to femoral arterial cannulation is distal limb ischemia. This risk is particularly relevant in smaller patients and whenever the arterial cannula occupies a substantial proportion of the vessel lumen. Reported rates vary across series, but clinically significant ischemia remains a well-recognized hazard of femoral VA-ECMO and may require distal reperfusion, fasciotomy, decannulation, or vascular reconstruction [3,4]. Preventive strategies, including distal perfusion catheters and careful surveillance of limb perfusion, are therefore central to femoral cannulation practice [4,5].

3.6 Practical teaching point

Femoral cannulation is often the fastest and most scalable peripheral VA-ECMO strategy in larger patients, but it comes with a characteristic physiologic cost: retrograde aortic flow, increased LV afterload, risk of differential upper-body hypoxemia, and risk of distal limb ischemia.

4. How current evidence reframes the neck-versus-femoral question

A modern reading of the literature suggests that the debate should not be framed as a simple contest between two access sites. Instead, the available evidence supports a more individualized approach.

4.1 What the literature suggests

• Practice variation remains substantial, especially in pediatric cohorts, indicating that institutional preference still influences access selection [1].
• Mortality differences between carotid and femoral peripheral approaches have not been shown consistently enough to justify a single universal strategy [1,2].
• Carotid access has a distinct neurologic and vessel-management profile, but adjusted analyses do not show a consistent independent stroke penalty [2].
• Femoral access has a distinct vascular complication profile, especially limb ischemia, and requires active preventive planning [3,4].
• Peripheral configurations in general may offer lower bleeding burden than central strategies in some analyses, but that advantage does not eliminate the need to manage peripheral-specific complications carefully [8].

4.2 Practical selection framework

Neck cannulation is generally favored when:

• the patient is a neonate or small infant
• femoral vessels are too small
• rapid central reinfusion is desirable
• lower-extremity ischemic risk is unacceptable

Femoral cannulation is generally favored when:

• the patient is larger
• groin access is rapidly feasible
• immediate deployment is required
• vessel caliber permits adequate flow with a distal perfusion strategy when needed

Accordingly, the most useful formulation is not “Which site is best?” but rather:

Which site best matches this patient’s size, anatomy, urgency, and expected support physiology?

5. Contemporary clinical perspective

Peripheral VA-ECMO should not be regarded as a static cannulation configuration. It is a dynamic support state that evolves as cardiac function, pulmonary function, and vascular complications change over time. Three implications follow:

1. Cannulation strategy should anticipate the next physiologic problem.

A femoral configuration may restore blood pressure quickly yet later produce LV overload or differential hypoxemia.

2. Monitoring must be site-specific.

Neck cannulation requires attention to cerebral perfusion, neurologic surveillance, and cervical vessel management. Femoral cannulation requires active monitoring of LV loading, right-arm oxygenation, and distal limb perfusion.

3. Reconfiguration may become necessary.

In selected patients, persistent differential hypoxemia, inadequate LV unloading, or access-related complications may require conversion to another configuration or the addition of adjunctive drainage or return limbs [6,7].

6. High-yield summary

Peripheral VA-ECMO cannulation is not only about gaining access.

It is the first major determinant of support physiology.

Neck cannulation

• usually uses the right carotid artery and right internal jugular vein
• is often preferred in neonates and small infants
• provides central arterial reinfusion
• avoids the classic femoral limb-ischemia problem
• requires careful attention to neurologic and cervical vascular issues

Femoral cannulation

• usually uses the femoral vein and femoral artery
• is widely used in larger patients
• generates retrograde aortic flow
• can increase LV afterload
• may produce differential upper-body hypoxemia
• requires careful surveillance for distal limb ischemia

Most important concept

The cannulation site determines not only where the cannulas go, but how the entire circulation behaves once VA-ECMO begins.

References

[1] Assy J, Di Nardo M, El Rassi I. Peripheral veno-arterial ECMO cannulation in children: Review of the relevant ELSO publications. Perfusion. 2025 Dec 8:2676591251407295. doi: 10.1177/02676591251407295.

[2] Johnson K, Jarboe MD, Mychaliska GB, Barbaro RP, Rycus P, Hirschl RB, et al. Is there a best approach for extracorporeal life support cannulation: a review of the extracorporeal life support organization. J Pediatr Surg. 2018;53(7):1301-1304.

[3] Fraser CD 3rd, Kovler ML, Guzman W Jr, Rhee DS, Lum YW, Alaish SM, et al. Pediatric Femoral Arterial Cannulations in Extracorporeal Membrane Oxygenation: A Review and Strategies for Optimization. ASAIO J. 2019;65(7):636-641.

[4] Bonicolini E, Martucci G, Simons J, Raffa GM, Spina C, Lo Coco V, et al. Limb ischemia in peripheral veno-arterial extracorporeal membrane oxygenation: a narrative review of incidence, prevention, monitoring, and treatment. Crit Care. 2019;23(1):266.

[5] Lorusso R, Shekar K, MacLaren G, Schmidt M, Pellegrino V, Meyns B, et al. ELSO Interim Guidelines for Venoarterial Extracorporeal Membrane Oxygenation in Adult Cardiac Patients. ASAIO J. 2021;67(8):827-844.

[6] Ezad SM, Ryan M, Donker DW, Pappalardo F, Barrett N, Camporota L, et al. Unloading the Left Ventricle in Venoarterial ECMO: In Whom, When, and How? Circulation. 2023;147(16):1237-1250.

[7] Falk L, Sallisalmi M, Andersson Lindholm J, Lindfors M, Frenckner B, Broomé M, et al. Differential hypoxemia during venoarterial extracorporeal membrane oxygenation. Perfusion. 2019;34(1_suppl):22-29.

[8] Raffa GM, Kowalewski M, Brodie D, Ogino MT, Whitman GJR, Meani P, et al. Meta-Analysis of Peripheral or Central Extracorporeal Membrane Oxygenation in Postcardiotomy and Non-Postcardiotomy Shock. Ann Thorac Surg. 2019;107(1):311-321.