**5. Types of cannulas**

Aortic cannulas come in a variety of commercially available options. Cannula size should be selected in conjunction with the perfusionist team so as to utilize the appropriate cannula for adequate flow within the circuit. Too large of a cannula may require an aortotomy that is difficult to close in a standard fashion, while too small of a cannula will not allow sufficient flows. A narrower cannula can cause high pressure gradients, cavitation, or jets of flow which can increase the likelihood of dissection. Diffusion-tip cannulas are available which provide multidirectional flow to reduce jets. The tip of the cannula may be straight, tapered, or angled, as well as made from metal or plastic. Various tip modifications, such as flanges or adjustable rings, are available to prevent the cannula from being inserted too far into the aorta and impeding flow to the head vessels. When using an alternate arterial cannulation site, certain adjustments must be made. Adequate bypass support via femoral cannulation is best achieved with a long, wire-reinforced cannula, whereas the diameter of the axillary artery must be taken into account when selecting an appropriate cannula [10].

## **6. Steps to cannulation**

Arterial cannulation is almost always completed prior to venous cannulation during the setup for cardiopulmonary bypass. The steps below outline the appropriate manner in which arterial cannulation can be achieved.

1.Identify the appropriate cannulation site through the use of preoperative imaging, surgical history, and operator preference (**Figure 1**).


These should be snared in the standard fashion, as they will be tightened and tied after the cannula has been removed to close the aortotomy. The adventitia within the sutures is then gently divided to prepare for aortotomy (**Figure 3**).


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**Figure 3.**

**Figure 2.**

*The adventitia is gently removed from the cannulation site within the purse string sutures.*

*Cannulation for Cardiopulmonary Bypass DOI: http://dx.doi.org/10.5772/intechopen.86033*

Closing the aortic cannulation site is rather straightforward. The purse string sutures that were placed prior to the cannula insertion are utilized to close the incision once the tubing has been removed. If needed, an additional mattress

*Cannulation site opposite brachiocephalic artery with purse string sutures placed. Note the cannula at the lower* 

*border of the image with a flange marking the maximum length of desired insertion.*

**Figure 1.** *Ascending aortic exposure prior to cannulation.*

#### *Cannulation for Cardiopulmonary Bypass DOI: http://dx.doi.org/10.5772/intechopen.86033*

Closing the aortic cannulation site is rather straightforward. The purse string sutures that were placed prior to the cannula insertion are utilized to close the incision once the tubing has been removed. If needed, an additional mattress

#### **Figure 2.**

*Cardiac Surgery Procedures*

2.Utilize additional intraoperative imaging, such as TEE and epi-aortic ultrasound (discussed below), and surgical palpation to ensure avoidance of atherosclerotic regions to minimize risk of embolization. Adequate surgical exposure should be obtained through tedious dissection of the desired vessel. When using the axillary or femoral artery, proximal and distal control should be obtained in the form of vessel loops. Ascending aortic exposure should include the origin identification and isolation of the brachiocephalic trunk and

3.Two purse string sutures should be placed at the intended access site, typically with monofilament (Prolene™) or braided (Ethibond™) nonabsorbable suture, at a distance that can accommodate an average 20–22F cannula (**Figure 2**).

These should be snared in the standard fashion, as they will be tightened and tied after the cannula has been removed to close the aortotomy. The adventitia within the sutures is then gently divided to prepare for aortotomy (**Figure 3**).

4.Close attention should be paid to the systemic blood pressure, which should be below 100 mmHg prior to aortotomy to decrease the incidence of dissection. A #11 or #15 blade is used to make the aortotomy within the purse string sutures, while the adventitia superior to the incision is pulled gently inferiorly to cover the defect in order to prevent excessive bleeding (**Figure 4**). The incision should be adequate to accommodate the selected cannula but not excessively wide so as to cause difficulty snaring the cannula in place while on bypass. The selected cannula is then inserted into the aorta, and the sutures snared down (**Figure 5**). As previously mentioned, the cannula tip should not be inserted

any further than necessary so as to provide optimal systemic flow.

5.Appropriate placement of the cannula is then verified by checking for adequate back-bleeding, which is an opportunity to de-air the cannula as well. Alternatively, the perfusionist may check the arterial waveform for flow verification after the line has been de-aired and connected to the circuit.

6.The arterial cannula and snares are then tied together with silk ties to provide

the main pulmonary artery, at a minimum.

additional stability [11] (**Figure 6**).

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**Figure 1.**

*Ascending aortic exposure prior to cannulation.*

*Cannulation site opposite brachiocephalic artery with purse string sutures placed. Note the cannula at the lower border of the image with a flange marking the maximum length of desired insertion.*

#### **Figure 4.**

*A scalpel is used to make the aortotomy at the cannulation site, while gentle inferior traction is placed with the adventitia to prevent excessive bleeding.*

#### **Figure 5.**

*The aortic cannula has been inserted, and the purse string sutures snared down.*

or figure-of-eight suture can be placed to reinforce the aortotomy [12]. The use of felt pledges is left to the discretion of the surgeon. These are composed of prosthetic material such as polytetrafluorethylene and are used to achieve a greater level of hemostasis, especially in patients with fragile tissue such as the

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*Cannulation for Cardiopulmonary Bypass DOI: http://dx.doi.org/10.5772/intechopen.86033*

**7. Axillary artery cannulation**

**Figure 6.**

significantly.

elderly [12]. There is, however, a theoretically increased risk of bacterial infection with their use [12]. When closing femoral or axillary cannulation sites, a bovine pericardial patch is frequently used so as not to narrow the arterial diameter

If the axillary artery is selected as the cannulation site, the exposure should be completed prior to median sternotomy. The right side is preferred. To isolate the artery, an incision is made 2 fingerbreadths inferiorly at the middle 1/3 of the clavicle. The incision may be extended laterally. The subcutaneous tissue is dissected down to the level of the pectoralis major. The pectoralis major is then split in the direction of its fibers, and the pecoralis minor is retracted laterally. The axillary vein is the first vascular structure encountered. It is dissected out and retracted inferiorly. Care should be taken to ligate small venous branches. The brachial plexus is superior to the artery and should be avoided if possible. Once the axillary artery is dissected from the surrounding tissue and isolated, the decision must be made to cannulate the artery directly or use an extension graft, such as Dacron. If the artery is to be cannulated directly, open transverse arteriotomy may be made or Seldinger technique employed for cannula placement. A graft is most helpful for small arteries where there is concern that the size of the cannula will completely occlude distal flow or if there is concern that the artery will be significantly narrowed when the arteriotomy is closed. If a graft is to be used, proximal and distal clamps should be placed on the artery, followed by a longitudinal arteriotomy. Graft anastomosis is typically completed with a 6-0 polypropylene suture. After the anastomosis is complete, the graft can be cannulated and blood flow to the arm restored. At the completion of cardiopulmonary bypass, the graft may be ligated and oversewn. If a graft is not used, the arteriotomy can be closed in the standard fashion after decannulation. Standard cannulation strategies should be used, as discussed above. After

*The aortic cannula and snared purse string sutures are secured together with a heavy silk suture.*

#### *Cannulation for Cardiopulmonary Bypass DOI: http://dx.doi.org/10.5772/intechopen.86033*

*Cardiac Surgery Procedures*

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**Figure 5.**

**Figure 4.**

*adventitia to prevent excessive bleeding.*

or figure-of-eight suture can be placed to reinforce the aortotomy [12]. The use of felt pledges is left to the discretion of the surgeon. These are composed of prosthetic material such as polytetrafluorethylene and are used to achieve a greater level of hemostasis, especially in patients with fragile tissue such as the

*The aortic cannula has been inserted, and the purse string sutures snared down.*

*A scalpel is used to make the aortotomy at the cannulation site, while gentle inferior traction is placed with the* 

elderly [12]. There is, however, a theoretically increased risk of bacterial infection with their use [12]. When closing femoral or axillary cannulation sites, a bovine pericardial patch is frequently used so as not to narrow the arterial diameter significantly.

**Figure 6.** *The aortic cannula and snared purse string sutures are secured together with a heavy silk suture.*
