Cannulation and Cannula Configurations for VV-ECMO

Achieving proper vascular access is a fundamental step in implementing an ECMO treatment [9-15]. An important historical step in cannulation for ECMO has been the availability of thin-walled cannulas, in the early 1990s, that allowed to move from surgical to percutaneous cannulation techniques. The percutaneous approach has several advantages: reduced risk of bleeding, shorter operative time and easier mobilization and nursing of the patient. This reason has become the standard technique for VV-ECMO [9-15].

Choice of vessels, cannulas type and size and configuration are mainly dictated by the maximum ECBF needed for the support of the patient, the maximum recirculation tolerable, the patient comfort, the patient anatomical features, the presence of some obstructed vein and local preferences.

The size and position of the drainage cannula are the main determinants of ECBF. For ECBF higher than 3-4 l/min, drainage cannula size to up 23-28 Fr is necessary. The best position is the intrahepatic portion of the inferior vena cava or in the right atrium. Cannulas with multiple holes distributed along the cannulas are available to enhance blood drainage (multiple-stage drainage cannulas). The reim- mission cannulas normally have holes only in a short portion near to their extremity.

For VV-ECMO four different cannula configurations are available (Fig. 7.2):

Fig. 7.2 A schematic of cannula configuration using single-lumen cannulas. Independently from the reimmission cannula, the drainage cannula should be placed with the tip above renal veins. Drainage performance and recirculation rate are reported on the bottom. Though drainage is considered easier with the jugular-femoral approach, recirculation is higher and the effective extracorporeal blood flow is lower than with the other configurations

• 1. Femoral-jugular configuration: The drainage cannula (21-28 Fr, 38-55 cm long) is inserted through the femoral vein and positioned with the tip in the inferior vena cava, while the reimmission cannula (19-21 Fr, 15-38 cm long) is inserted through the jugular vein with the tip in the right atrium. This represents the most used and also the easiest configuration. ECBF rates up to 6-7 L/min are easily obtained with minimal recirculation [16].
• 2. Femoro-femoral configuration: The drainage cannula (21-28 Fr, 38-55 cm long) is inserted through the femoral vein and positioned with the tip in the inferior vena cava, while the reimmission cannula (21-23 Fr, 50-55 cm long) is inserted through the contralateral femoral vein with the tip positioned in the inferior vena cava (but higher than the drainage cannula) or in the right atrium. The femoro- femoral approach offers safer access and less possibility of accidental cannula dislocation. Mobilization of the patient’s head is facilitated, but at the expense of lower limb mobilization. With this approach, minimization of recirculation requires careful positioning of the cannula tips.
• 3. Jugular-femoral configuration: The drainage cannula (21-25 Fr, 15-38 cm long) is inserted through the jugular vein and positioned with the tip in the right atrium, while the reimmission cannula (19-23 Fr, 15-55 cm long) is inserted through the femoral vein. Though popular in some centre, this approach is not much diffused given the high recirculation.
• 4. Single-vessel double-lumen cannula: A single double-lumen cannula is inserted through the jugular vein. Different types of double-lumen cannulas are available. The most popular is the AVALON ELITE® Bi-Caval Dual Lumen Catheter [1720]: the cannula is positioned through the jugular vein with the tip in the inferior vena cava. The configuration of the cannula allows drainage of blood from both the superior and inferior vena cava, while reimmission is in the right atrium. Sizes ranging from 13 to 31 Fr are available.