Direct Central Cannulation Technique: A Stepwise Guide

The development of cardiopulmonary bypass (CPB) has revolutionized cardiac surgery (1). To improve the outcome of patients undergoing cardiac surgery, a task force has developed evidence-based guidelines for the use of CPB, which contributed to the optimization and standardization of CPB techniques (2). However, to ensure safe and effective practice, surgeons need to be adequately trained with appropriate knowledge, skills, and expertise (3).  

The distal ascending aorta is the most common arterial cannulation site, while the femoral and axillary arteries are the most common alternatives. The size of the cannula is selected preoperatively between a perfusionist and a surgeon, based on the patient body surface area, anticipated flow rate, and the target vessel. Using a checklist is also recommended during the setup and prior to initiating CPB. Central venous cannulation can be performed using single cavoatrial (two-stage) through the right atrial appendage or bicaval approaches. Venous cannulas are usually made of flexible plastic that is reinforced to prevent kinking.  

This stepwise video guide demonstrates the standard direct aortic and venous cannulation technique. 

Patient Presentation 

The patient is a seventy-two-year-old man being operated upon for a coronary bypass graft surgery. During a preoperative workup, a coronary angiography reveals a severe three-vessel coronary artery disease. A transthoracic echocardiogram demonstrates good biventricular heart function with no valvular abnormalities. 

Operative Steps  

Preparation for Cardiopulmonary Bypass 

After the surgeon is ready to commence CPB, a heart-lung console is positioned next to the operating table on the patient’s left side. A sterile prepackaged tubing kit allows the perfusionist to pass the sterile lines to a scrub nurse or assistant at the operative field. Adequate lengths of tubing should be provided. After administration of systemic heparin and verification that the patient is adequately anticoagulated, the priming is recirculated through the CPB circuit while the lines are inspected by the surgeon or an assistant to verify that there are no visible air bubbles. After recirculation is stopped, the arterial and venous lines are clamped and divided. The aortic cannula should be checked before use. 

Direct Aortic Cannulation 

The aortic cannulation is performed before the venous, as it allows for rapid transfusion if the patient hemodynamically deteriorates. Heparin should be dosed between 300 to 500 U/kg based on the patient’s weight . Two concentric and adventitial purse-string sutures are placed into the aortic wall of the distal ascending aorta to allow enough space for applying the aortic cross-clamp. Optimal systolic arterial blood pressure (BP) during cannulation should be below 100 mmHg. If BP is too high, there may be a higher risk of tears, blood loss, or dissection; if too low, it may be harder to insert the cannula with a higher risk of injuring the back wall of the aorta. 

It is of paramount importance to clear the adventitia within the purse-string suture, and to make a full-thickness incision of appropriate size. The leak is controlled with a finger by approximating the adventitia with a forceps or by simultaneously inserting the cannula. Special care should be taken to confirm that there is an adequate pulsation, as its absence may indicate malposition of the cannula or its insertion within the aortic wall, with the risk of arterial wall hematoma or dissection upon initiation of CPB. Purse-string sutures are snared and secured together with a tie. After the aortic cannula is filled retrogradely with blood, it is connected to the arterial line while the perfusionist is slowly advancing the priming with a retrograde flow to ensure an air-free connection. It is important to keep in mind that during aortic cannulation, dislodgement of atheromatous debris from the aortic wall can occur with a risk of perioperative stroke. To prevent this, the aorta can be palpated before cannulation, and a transesophageal echocardiography or epiaortic ultrasound can be used for screening. 

Venous Cannulation 

Central venous cannulation can be performed with single cavoatrial (two-stage) or bicaval approach. Single cavoatrial cannulas are usually inserted through the right atrial appendage after placing a full-thickness purse-string suture, and the tip of the cannula at the level of the upper part of the inferior vena cava (IVC). Bicaval cannulas are usually placed through separate incisions. It is important to carefully place the purse-string bites to avoid tearing of the right atrium, as the medial surface of the right atrium can be frail. It is also important to stay away from the atrioventricular (AV) groove to avoid risk of injuring the right coronary artery, and to avoid sinoatrial (SA) node injury at the junction of superior vena cava and the right atrium. A tourniquet is placed on the purse string. 

The right atrium incision is made in the middle of the purse string with an 11-blade followed by the scissors. Once the cannula is within the right atrium, the tip is directed downward to the IVC with the appropriate depth until the marker. A purse-string suture is snared and secured with a tie, and the cannula is connected to the venous line with the least air as possible. Finally, the venous drainage needs to be checked with the perfusionist. If there is any concern, the cannula may need to be repositioned and other causes investigated. 

Outcome  

Coronary artery bypass grafting was uneventful, and the patient was weaned of CPB with minimal inotropic and vasopressor support. The patient made a quick recovery following the procedure. 

References

1. Gravlee GP, Davis RF, Stammers AH, Ungerleider RM, editors, Cardiopulmonary Bypass: Principles and Practice. 3rd ed. Lippincott Williams and Wilkins. 2008. p. 261-281
2. Wahba A, Milojevic M, Boer C, et al. EACTS/EACTA/EBCP Committee Reviewers. 2019 EACTS/EACTA/EBCP guidelines on cardiopulmonary bypass in adult cardiac surgery. Eur J Cardiothorac Surg. 2020 Feb 1;57(2):210-251.
3. Svenmarker S, Häggmark S, Jansson E, Lindholm R, Appelblad M, Aberg T. Quality assurance in clinical perfusion. Eur J Cardiothorac Surg. 1998 Oct;14(4):409-14.

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