Knowing that blood is circulating isn’t enough when it comes to protecting the limb during ECMO. It’s equally important to know how much and how well the blood is flowing. 

Many teams monitor distal perfusion using near-infrared spectroscopy (NIRS), which offers helpful insight into tissue oxygenation. But perfusion isn’t just about saturation; it’s also about flow. That’s where NIRS alone can fall short. And that’s why the ELSO guidelines recommend a dual monitoring approach.

NIRS Has Value, but It Also Has Limitations

NIRS has become a go-to tool in ECMO programs for good reason. It’s non-invasive, offers continuous monitoring, and supports clinical awareness of tissue oxygenation (all benefits of flow measurement, too!). 

But the utility of NIRS isn’t always guaranteed:

• Cost: NIRS systems are expensive to purchase and maintain.
• Access: In many hospitals, NIRS is a shared resource. That means when a patient needs it for limb perfusion monitoring, the system might be in use elsewhere.
• Accuracy across skin tones: Studies have shown that NIRS efficacy declines with increased melanin pigmentation. Darker skin tone is associated with worse NIRS performance and lower NIRS values, leading to potential inaccuracies.

These challenges don’t diminish NIRS’s usefulness, but they underscore its limitations when used alone. And, even when available, NIRS only tells part of the story when it comes to limb perfusion.

That’s because NIRS measures oxygenation, not blood flow volume. It’s designed to detect drops in tissue saturation, providing an early warning system for ischemia. 

Flow sensors and meters, by contrast, measure the actual volume of blood passing through the DPC in real time. This data can be used by the care team to avoid both under- and over-perfusion, which can lead to tissue damage, compartment syndrome, or even limb loss.

When you’re monitoring something as delicate and critical as distal perfusion, you need both oxygenation and flow to make data-driven decisions.

What the ELSO Guidelines Recommend

The Extracorporeal Life Support Organization (ELSO) explicitly recommends dual monitoring for patients on VA ECMO in ELSO Interim Guidelines for Venoarterial Extracorporeal Membrane Oxygenation in Adult Cardiac Patients. 

Specifically, the guidelines state:

• Tissue saturation by NIRS should be above 50%, preferably 60%, and there should be less than a 20% difference between the two extremities.
• When possible, measurement of flow confirms adequate tissue perfusion, targeting at least 100ml/min.

In short, oxygenation and flow measurement work together. NIRS alone gives part of the picture, while real-time flow monitoring completes it.

An Easy Way To Add Flow to Your Monitoring

If you’re wondering whether this means overhauling your setup, the answer is no. 

Transonic’s AureFlo® sensor and Optima® Flowmeter are made for teams like yours. They clamp right onto 1/8-inch DPC tubing without interrupting your circuit or workflow.

That means you get:

• Real-time, beat-to-beat measurements
• Fast confirmation of whether your DPC is in range
• Compatibility with your existing ECMO system
• Insight you can use in the ICU, OR, or cath lab

Adding flow measurement is a small, easy change to make to your workflow, but one that gives you a much clearer picture of what’s happening and saves time in the long run. 

Learn more about flow measurement for distal limb perfusion.