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FIG. 2.20 Clamp injury to the right coronary artery.
FIG. 2.21 Management of a right coronary artery clamp injury.
Bicaval Cannulation
Technique
Some procedures that entail exposure inside the right side of the heart, such as repair of an atrial septal defect,
ventricular septal defect, or tricuspid valve, require bicaval cannulation. This can be accomplished by introducing
caval cannulas through purse-string sutures in the right atrial appendage and lower on the right atrial wall (Fig.
2.23). At present, we cannulate each vena cava directly (Fig. 2.24). This technique provides excellent exposure
of the intraatrial anatomy, which is particularly desirable in pediatric patients (see Technique of Direct Caval
Cannulation section).
Location of Tape Around the Superior Cava
The actual site for placement of tapes around the superior vena cava should be well above (˜1 cm) the cavoatrial
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junction so as not to injure the sinoatrial node (Fig. 2.23).
FIG. 2.22 Cannulation through a segment of pericardium left intact on the atrial wall.
Placing Tapes Around the Cavae
Care must be taken when passing a right-angled clamp around either the superior or inferior vena cava to avoid
tearing the back wall. Sharp dissection may be necessary to create a safe passage for the clamp. In addition, the
umbilical tape should be pulled around the cava slowly to avoid a sawing injury.
Excess Length of the Cannula
Excess length of the cannula in the superior vena cava may interfere with the flow from the azygos and
innominate veins, thereby obstructing the venous return from the upper body. Constant monitoring of the
pressure in the superior vena cava can reveal any pressure increase and thereby alert the surgical team. Minor
manipulation of the cannula usually relieves the obstruction, which can otherwise cause engorgement of the
central nervous venous system with neurologic sequela.
Left Superior Vena Cava
If a left superior vena cava is present and no innominate vein is noted, it should be directly cannulated.
Technique of Direct Caval Cannulation
Inferior Vena Cava
A 4-0 or 5-0 Prolene purse-string suture is applied at the junction of the inferior vena cava and the right atrium.
Friable Inferior Vena Cava Wall
Whenever the wall of the inferior vena cava appears to be friable, the purse-string suture should incorporate the
parietal pericardium overlying the diaphragm for added security. However, a curvilinear incision is made on the
pericardium 1 to 2 cm from the edge of the suture if it appears to be under tension.
FIG. 2.23 Placement of tapes around the cava in bicaval cannulation.
A stab wound is made in the center of the purse-string suture. The opening is dilated with a tonsillar clamp. An
appropriately sized right-angled cannula is introduced, and the purse-string suture is secured around the
cannula.
Superior Vena Cava
The pericardial reflection on the superior vena cava is divided to maximally free up the great vein. A rectangular
or oval purse-string suture of 5-0 or 4-0 Prolene is placed in the adventitia of the superior vena cava close to its
junction with the innominate vein. The adventitia within the purse-string is divided, and the vein wall is identified
and incised with a knife. The opening is enlarged with a tonsillar clamp if necessary. An appropriately sized right-
angled cannula is introduced into the lumen, and the purse-string suture is secured. In patients with deep chests,
a ringed clamp is used to load the cannula and direct it into the vessel.
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FIG. 2.24 Direct caval cannulation.
Alternatively, with the superior vena caval cannula in place, partial cardiopulmonary bypass is established and
the right side of the heart is decompressed. Inferior vena caval cannulation is carried out as just described. This
is particularly useful in infants and patients who are hemodynamically unstable.
Vena Caval Stenosis
The purse-string suture for superior and inferior venae cavae should be small enough to accommodate the
cannula and not cause stenosis once tied. This is apt to occur when the vena cava is relatively small or in
children and infants. Occasionally repair sutures are needed to control bleeding once decannulated. If bleeding
persists, it is advisable not to place many repair sutures and fix the defect on bypass under direct vision. If
narrowing is suspected, direct proximal and distal pressure measurements as well as transesophageal
echocardiographic assessment are mandatory. If a significant stenosis is identified, return to cardiopulmonary
bypass via direct right atrial cannulation is utilized to repair the caval defect under visualization.
Femoral Venous Cannulation
If cardiopulmonary bypass is required before or during a redo sternotomy, the venous drainage can be secured
by cannulating the femoral vein. This technique is also useful for minimally invasive approaches.
Technique
The femoral vein can be cannulated percutaneously. We prefer to expose the femoral vein through a small
incision below the inguinal ligament if simultaneous femoral arterial access is needed. A purse-string suture of 5-
0 Prolene is placed on the anterior aspect of the common femoral vein. A long venous cannula with multiple side
holes is placed by first passing a guide wire through a needle puncture in the middle of the purse-string stitch.
The cannula mounted on a tapered dilator sheath is gently advanced over the guide wire and positioned either in
the right atrium or inferior vena cava depending on the procedure to be performed under transesophageal
echocardiographic control. At the conclusion of the procedure, the cannula is withdrawn from the vein and the
purse-string suture is tied.
Iliac Vein Injury
Venous cannulas that lack a guidewire often hang up at the pelvic brim, resulting in inadequate venous return. If
an attempt is made to advance the cannula into the inferior vena cava, perforation of the iliac vein may occur
with catastrophic consequences.
To ensure adequate venous return, assisted venous drainage with a centrifugal pump or vacuum assist is
useful.
Adequacy of Bypass
Upon initiation of bypass, organ perfusion is compromised by the initial flow of crystalloid volume with minimal
oxygen carrying capacity, hypotension due to rapid hemodilution and non-pulsatile flow. This problem is
exacerbated when organs including the brain are normothermic at the initiation of bypass. Cardiopulmonary
bypass should therefore be started gradually to mitigate this problem. As the arterial flow and venous return
increase, a search for possible problems with the cardiopulmonary bypass is made. It is a simple matter to stop
the bypass, if necessary, and rectify any complication at this stage of the operation.
Signs of Aortic Dissection
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Excessive pressure in the pump line concomitant with low perfusion pressure signals aortic dissection (see
Retrograde Aortic Dissection section).
Intraoperative transesophageal echocardiography is most helpful in confirming this diagnosis.
Only awareness and prompt diagnosis of this complication followed by immediate cessation of cardiopulmonary
bypass can ensure patient survival. The cannulation site must be switched from the ascending aorta to one of
the femoral arteries, and cardiopulmonary bypass must be reestablished as expeditiously as possible. This
permits the continuation of the surgery. The reversal of blood flow into the lumen of the arterial system
obliterates the false channel and stops the progression of aortic dissection. The problem of ascending aortic
injury is then addressed in a controlled situation (see Traumatic Disruption and Dissection of the Ascending
Aorta section).
Improper Positioning of Caval Cannula
A decrease in venous return causes distention of the heart. The decrease can be due to a kink in the venous
line, impaction of the basket of the dual-stage atriocaval cannula against the atrial wall, or improper positioning of
the caval cannulas. The inferior vena caval cannula can be too far down obstructing the hepatic vein drainage,
which can lead to postoperative liver dysfunction. The superior vena caval cannula can be too high, interfering
with innominate and azygos vein drainage. As mentioned previously, inadequate head and neck venous return
can result in cerebral edema and postoperative neurologic complications. In cases of bicaval cannulation,
cardiopulmonary bypass is usually begun with only superior vena caval return, and its adequacy is ascertained
by noting the volume of venous return and the central venous pressure. If the central venous pressure remains
high, the superior vena caval cannula is moved around until a near-zero central venous pressure is achieved.
The inferior vena caval cannula is then unclamped.
Retrograde Aortic Dissection
Retrograde aortic dissection is indeed a catastrophic complication that may follow femoral or external iliac
cannulation. A diseased artery, faulty cannulation technique, and trauma produced by a high-velocity perfusion
jet are major factors that may cause a tear of the intima with medial separation. It is therefore essential to
introduce an adequately sized, beveled, smooth cannula into a relatively normal vessel in an atraumatic manner.
The perfusion should be
started gradually, with the surgeon being cognizant at all times of the possible occurrence of aortic dissection.
The most significant diagnostic feature is low flow with high arterial line pressure in the circuit. The arterial return
into the false lumen is responsible for excessive pressure in the arterial line while the actual perfusion of the
patient is inadequate. This leads to a decrease in venous return. If this complication occurs, perfusion should be
immediately stopped. The femoral artery or the external iliac artery on the opposite side should then be
cannulated if not involved; otherwise, the ascending aorta, the subclavian or axillary artery must be cannulated.
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FIG. 2.25 Use of a Hemashield tube graft for aortic disruption.
Traumatic Disruption and Dissection of the Ascending Aorta
Intraoperative traumatic dissection or disruption of the ascending aorta is a rare but dramatic complication of
open-heart surgery. The areas of aortic cannulation, the proximal anastomosis of an aortocoronary saphenous
vein graft, and an aortotomy done for exposure of the aortic valve are the usual sites prone to such a
complication. This is especially so in reoperative procedures. Although faulty techniques always predispose a
surgical procedure to complications, poor tissue quality and the presence of infection are the most common key
precipitating factors in the development of aortic injury. The only preventive measure is awareness of the
possibility of such complications and meticulous surgical technique in handling the tissues. In most cases, the
torn segment of the aorta will be excised with an arrested heart and replaced with a Hemashield tube graft
(Meadox Medicals, Oakland, NJ) (Fig. 2.25).
3
Myocardial Preservation
Myocardial protection has clearly made open-heart surgery a safe and reproducible technique. There continues
to be many modifications of the chemical composition of the cardioplegic solution, the optimal temperature (cold
or warm), and the route of infusion (antegrade or retrograde). As the concepts of myocardial preservation and
surgical approaches have evolved, improved cannulas and cardioplegia delivery systems have been introduced.
AORTIC ROOT INFUSION TECHNIQUE
The cannula is introduced into the root of the aorta through a 4-0 Prolene, one-and-a-half-circle purse-string
suture that is snugged down and secured to the cannula. Although any large-bore needle or cannula is
satisfactory, those with a trocar introducer and a side arm for direct intraaortic pressure monitoring are most
useful. The side arm can also be used for venting.
Insufficient Infusion Pressure
Distortion of, or insufficient pressure in, the aortic root may prevent adequate coaptation of the aortic valve
leaflets, as will aortic valve insufficiency. The cardioplegic solution passes through the open valve and
overdistends the left ventricle, which can cause direct myocardial injury. Digital pressure on the right ventricular
outflow tract at the level of the aortic annulus may produce coaptation of the leaflets and prevent regurgitation of
the cardioplegic solution.
Excessive Infusion Pressure
Excessive infusion pressure can traumatize the coronary arteries, resulting in ischemic myocardial injury.
Accurate monitoring of the infusion pressure in the aortic root can be satisfactorily accomplished from the side
arm of specially designed cannulas.
Air Embolism
Air embolism to the coronary arteries can cause serious myocardial injury. Every effort must be made to clear the
cardioplegic line of any air bubbles. A bubble trap is now incorporated into cardioplegia administration systems to
minimize this possibility.
Impurities in the Cardioplegic Solution
Impurities and particulate matter may be present in the cardioplegic solution and can occlude terminal coronary
arteries, causing myocardial injury. Quality control in the preparation of the cardioplegic solution prevents such
complications.
Warm Cardioplegic Solution
Between infusions, the cardioplegic solution remaining in the tubing warms up. The warm solution should be
flushed out through either the free arm of the Y connecting tube or into the vent before infusion into the coronary
system.
Maintaining Uniform Cooling
Uniform cooling of the myocardium by infusion of cold cardioplegic solution is an integral part of myocardial
protection. At some institutions, temperature probes in various parts of the septum and ventricular wall are used
to monitor myocardial temperature during the course of the surgery. We typically utilize moderate systemic
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hypothermia, insulating pads, and topical cooling on the right ventricular surface in order to ensure uniform
cooling.
Inadequate Protection of the Right Ventricle
Despite all precautions to keep the heart cool, the anterior surface of the heart tends to rewarm because of the
ambient air temperature and the heat radiated from the operating room lights. A gauze pad soaked with cold
saline and ice placed over the heart provides additional protection for the right ventricle.
Topical Hypothermia
Placement of an insulating pad, a commercially available cooling “jacket,” or a cold lap pad behind the heart can
minimize rewarming of the heart by the warmer blood in the descending aorta during the cardioplegic arrest.
Care must be taken to avoid cold injury to the left phrenic nerve.
FIG. 3.1 A: Hand-held cannula for direct infusion into the coronary artery. B: Cannula advanced into the
coronary artery causing obstruction at the bifurcation.
DIRECT CORONARY ARTERY PERFUSION
When the aortic root is to be opened, as during aortic valve replacement, cardioplegic solution is administered
directly into each coronary ostium with a cannula (Fig. 3.1A). This technique is equally useful in patients who
have more than mild insufficiency of the aortic valve.
Cannula Damage to Coronary Ostium
Excessive pressure from the cannula against the coronary ostium can cause an intimal tear or late ostial
stenosis.
Size of the Cannula
The cannula must be the correct size, and only a snug fit is necessary to prevent leakage. A cannula head that is
too large or excessive pressure on the coronary ostium may not only interfere with satisfactory perfusion of the
coronary system but can also traumatize the coronary ostium.
Short Left Main Coronary Artery
The cannula can also interfere with satisfactory infusion of cardioplegic solution if the left main coronary artery is
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short. A branching artery may have its origin very near the ostium of the left main artery and therefore be
obstructed by the head of the cannula itself (Fig. 3.1B). Prior knowledge of this anatomy allows the surgeon to
take preventive measures. The use of a cannula with side holes prevents this complication. A flexible, hand-held,
soft-tipped cannula with a collar around the tip can provide satisfactory infusion of cardioplegic solution directly
into the coronary arteries (Fig. 3.1A). The collar presses against the aortic wall and the coronary ostium to
prevent spillage of cardioplegic solution into the aorta.
MYOCARDIAL PRESERVATION BY THE RETROGRADE PERFUSION METHOD
Retrograde infusion of cardioplegic solution into the coronary sinus is very efficient, although its effectiveness in
perfusing the right atrium, right ventricle, and inferior wall of the left ventricle may not always be adequate. The
technique provides retrograde perfusion of segments of myocardium that may not be equally perfused by the
antegrade route in patients with severe coronary artery disease. To ensure optimal myocardial protection, an
integrated method of antegrade and retrograde cardioplegia delivery is used in most centers.
Almost all retrograde cannulas are dual lumen to allow infusion of cardioplegic solution and monitoring of
pressure in the coronary sinus. A balloon, manually inflatable or self-inflating, surrounds the distal body of the
cannula, approximately 1 cm from the tip, proximal to the flow holes. A stylet is provided for ease of proper
placement.
Technique
Through a stab incision in the center of a 4-0 Prolene purse-string suture in the mid-atrium, a special retroplegia
cannula is introduced and directed into the coronary sinus. The correct position of the cannula is verified by
palpation or echocardiography. The stylet is withdrawn when the cannula is in a satisfactory position. The purse-
string suture ends are snugged through a tourniquet, which is then tied to the cannula.
When difficulty is experienced in placing the retrograde cannula, it is often possible to elevate the
decompressed
heart while on bypass, visualize the course of coronary sinus, and direct the cannula tip.
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FIG. 3.2 A: Perforation of the coronary sinus by a retrograde cannula. B: Coronary sinus tear. C: Suture closure
of the coronary sinus tear using epicardial tissue.
Intraoperative transesophageal echocardiography can often be helpful in directing the cannula along the
course of the coronary sinus and verifying the correct position of the cannula. This is particularly important when
performing cardiac surgery through minimally invasive incisions.
Perforation of the Coronary Sinus
The stylet and cannula must be guided into the coronary sinus very gently and not be advanced if any resistance
is encountered. The coronary sinus wall is very thin and can be perforated by the stylet or the cannula tip.
A tear in the coronary sinus must be dealt with by closing the epicardium carefully over the tear with a fine
Prolene suture (Fig. 3.2). Alternatively, it is patched with a piece of autologous pericardium when the patient is
on full cardiopulmonary bypass to prevent stenosis or occlusion of the coronary sinus.
Monitoring Infusion Pressure
The infusion pressure must be kept above 20 mm Hg and below 45 mm Hg in order to achieve effective
myocardial perfusion and avoid edema and coronary sinus rupture. To accomplish this, the position of the
cannula or the flow rate must be adjusted accordingly.
Monitoring Temperature
The perfusionist monitors the temperature of the cardioplegic solution as it leaves the delivery system. The
temperature can also be monitored as the solution enters the coronary sinus through some specially designed
retrograde cannulas.
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