A CPB circuit ought to be primed with fluid and all air expunged from the arterial line/cannula before connection to the affected person. The circuit is primed with a crystalloid solution and occasionally blood merchandise also are added. Prior to cannulation (commonly after starting the pericardium whilst the usage of principal cannulation), heparin or another anticoagulant is administered until the activated clotting time is above 480 seconds.
The arterial cannulation website is inspected for calcification or other sickness. Preoperative imaging or an ultrasound probe may be used to assist perceive aortic calcifications that would potentially become dislodged and cause an occlusion or stroke. Once the cannulation web page has been deemed secure, concentric, diamond-fashioned pursestring sutures are positioned within the distal ascending aorta. A stab incision with a scalpel is made within the pursestrings and the arterial cannula is passed thru the incision. It is crucial the cannula is handed perpendicular to the aorta to keep away from creating an aortic dissection. The pursestrings sutures are cinched across the cannula using a tourniquet and secured to the cannula. At this factor, the perfusionist advances the arterial line of the CPB circuit and the doctor connects the arterial line coming from the patient to the arterial line coming from the CPB device. Care need to be taken to ensure no air is in the circuit when the 2 are connected, or else the affected person should develop an air embolism. Other sites for arterial cannulation encompass the axillary artery, brachiocephalic artery, or femoral artery.
Aside from the variations in area, venous cannulation is done similarly to arterial cannulation. Since calcification of the venous gadget is much less commonplace, the inspection or use of an ultrasound for calcification on the cannulation sites makes no sense. Also, because the venous machine is below lots less pressure than the arterial device, only a unmarried suture is required to preserve the cannula in area. If most effective a unmarried cannula is for use (twin-level cannulation), it’s far passed thru the proper atrial appendage, thru the tricuspid valve, and into the inferior vena cava. If cannula are required (single-stage cannulation), the primary one is typically passed through the advanced vena cava and the second thru the inferior vena cava. The femoral vein will also be cannulated in pick sufferers.
If the heart must be stopped for the operation, cardioplegia cannulas are also required. Antegrade cardiopledgia (forward flowing, via the coronary heart’s arteries), retrograde cardiopledgia (backwards flowing, via the heart’s veins), or each types may be used depending on the operation and health care professional desire. For antegrade cardiopledgia, a small incision is made within the aorta proximal to the arterial cannulation site (between the coronary heart and arterial cannulation website online) and the cannula is located via this to supply cardiopledgia to the coronary arteries. For retrograde cardiopledgia, an incision is made on the posterior (returned) surface of the heart through the right ventricle. The cannula is located in this incision, passed via the tricuspid valve, and into the coronary sinus. The cardiopledgia traces are connected to the CPB machine.
At this factor, the patient is prepared to head on bypass. Blood from the venous cannula(s) enters the CPB machine with the aid of gravity where it’s miles oxygenated and cooled (if necessary) earlier than returning to the body through the arterial cannula. Cardiopledgia can now be administered to forestall the coronary heart, and a go-clamp is located throughout the aorta between the arterial cannula and cardiopledgia cannula to save you the arterial blood from flowing backwards into the heart.
Once the affected person is ready to come off of skip support, the go-clamp and cannulas are removed and protamine sulfate is administered to opposite the anticoagulative results of heparin.