Veno-Right Ventricular ECMO
After administering IV heparin, 300 IU/kg, the right femoral vein was exposed and a 22F percutaneous venous cannula (Togo Medikit Co Ltd; Tokyo, Japan) was inserted directly over a guidewire to serve as the drainage cannula. The tip of this venous cannula was positioned at the superior cavoatrial junction. An 18F wire-reinforced venous cannula (William Harvey venous cannula; Bard Inc; Billerica, Mass), used as the outflow cannula, was passed into the right ventricle across the tricuspid valve through the right jugular vein. The position of this return cannula was confirmed by directed palpation through a sixth right intercostal thoracotomy. The inflow and outflow cannula lines were connected to a perfusion circuit comprising a Nikkiso centrifugal pump (HPM-15; Nikkiso Co; Tokyo, Japan) and a membrane oxygenator (Midflow D705; Dideco Co; Mirandola, Italy). A flow probe was attached to the distal outlet line of the pump, and blood flow was measured using an electromagnetic flow meter (Nikkiso Co). The system (total priming volume, 250 mL) was primed with 0.9% w/v normal saline solution. A diagram of the veno-right ventricular (veno-RV) ECMO system is shown in Figure 1. The animals were subjected to moderate hypothermic veno-RV ECMO. The maximum possible blood flow rate was maintained, generally 100 mL/kg/min, and the blood/oxygen gas ratio in the oxygenator was maintained at 1:2. During veno-RV ECMO, the nasopharyngeal temperature of each animal was maintained at 30 to 31°C using a heat exchange machine, and the activated clotting time was maintained at greater than 400 s using a Hemochron 400 instrument (Model 400; Hemochron; Edison, NJ). canadian neighbor pharmacy
Acute Experimental Protocol
The pump was started with the aim of reaching a blood flow rate of 100 mL/kg/min. Once stable bypass conditions were established, the ventilator was disconnected to collapse the lungs, and veno-RV ECMO was performed without mechanical lung ventilation for 1 h; blood gas levels and hemodynamics were investigated. The hemodynamic parameters, heart rate (HR), mean femoral arterial pressure (AP), mean pulmonary arterial pressure (PAP) and mean LAP, were monitored continuously. Blood samples were obtained from the oxygenator inlet and outlet lines, LA, PA, and FA before veno-RV ECMO (baseline) and then 15, 30, 45, and 60 min after starting veno-RV ECMO without lung ventilation support. Blood samples were then analyzed (AB-510; Radiometer; Copenhagen, Denmark). After veno-RV ECMO was performed for 1 h, the lungs were mechanically ventilated again (as before veno-RV ECMO); a blood sample was obtained 15 min after ventilation was restarted. No vasoactive drugs were administered during or after veno-RV ECMO. After the animals were sacrificed by IV injection of potassium chloride, all the lungs were excised rapidly and preserved immediately in 10% w/v formaldehyde for hematoxylin-eosin staining.
Figure 1. Diagram of the veno-RV ECMO system, which consists of a centrifugal pump and a membrane oxygenator.