Saturday, November 27, 2010

The Norwood Procedure - The Surgeon's Perspective

Note: The following post is an excerpt from Dr. Michael McMullan's (the surgeon that did Lillian's surgery) account of the surgery. As such, it is heavy on the medical terms. I've tried to insert some of my own comments [they look like this] when appropriate to translate things into English when I can personally for those that are not medical professionals.This is an exact copy of what he wrote aside from my comments. Dr. McMullan, if you happen upon this and would prefer this not be up, please contact me.

Also, I'm not sure why it looks like the black is changing colors in some areas. It is all the same color when I post it, it may be some weird visual brain trick.

1. Modified Norwood procedure with 6 mm Sano shunt.
2. Central ECMO (extracorporeal membrane oxygenation) cannulation.

SURGEONS: David McMullan, MD, Attending; Lester Permut, MD, Assistant.


1. Severely hypoplastic ascending aorta with focal narrowing of the transverse aortic arch. [her aorta is very small and only gets smaller]
2. Globally depressed ventricular function. [What she does have doesn't work well]

1. Thymus.
2. Ductal tissue. 
3. Atrial septum.
4. Right ventricular muscle.

INDICATIONS: This infant was born with hypoplastic left heart syndrome and was stabilized in the Neonatal ICU. Her diagnostic studies and clinical history were presented at our multidisciplinary conference and it was the consensus of those present that she would benefit from a Norwood procedure at this time. By echocardiography, she has a very small ascending aorta. I discussed the risks and benefits of the surgical procedure with the patient's parents in detail. They asked appropriate questions, expressed their understanding, and provided written and informed consent. 

DESCRIPTION OF PROCEDURE: After obtaining Informed consent, the patient was taken to the operating room and underwent general anesthesia. Her chest and abdomen were prepped and draped. A transesophageal echocardiogram [an echo where the probe is passed down the esophagus as opposed to being on the outside of the chest to get better pictures] was performed. A midline sternotomy [this is the opening and cracking of her chest] was performed. The thymus [an organ that helps regulate the immune system] and anterior portion of the anterior pericardium were resected. [they were removed] The pericardium [the double walled sack that contains the heart and the roots of the blood vessels] was treated in glutaraldehyde [a medical grade disinfectant]. Inspection of the mediastinal [the group of structures containing contains the heart, the great vessels of the heart, esophagus, trachea, phrenic nerve, cardiac nerve, thoracic duct, thymus, and lymph nodes of the central chest] contents revealed a dilated right ventricle, severely hypoplastic ascending aorta, and focal narrowing of the mid transverse arch. The right subclavian artery and innominate artery [arteries that supply the right side of the body with blood] were mobilized. While attempting to prepare the ductus arteriosus [the shunt that kept her alive] for cannulation, the patient developed hypotension and bradycardia [extremely low blood pressure and heart rate, respectively]. In light of what was perceived to be acute coronary ischemia [i.e., severe restriction of blood flow to the heart] related to inadequate blood flow through the hypoplastic ascending aorta, a brief period of direct cardiac massage was initiated [that is, they were manually pumping her heart with their hands]. Cardiopulmonary bypass was initiated utilizing ductus arteriosus and right atrial cannulation. Upon initiation of bypass, the branch pulmonary arteries were mobilized and occluded using vessel loops to prevent pulmonary over circulation. Using vascular clamps to isolate the distal innominate artery, a longitudinal arteriotomy [the cutting open of an artery] was performed at this site and a Gore-Tex tube graft was anastomosed [or connected] to the site using running Prolene suture. The vascular clamp was removed to establish flow through the graft. An arterial cannula was then inserted into the graft and secured with Nurolon suture. This was then connected to the arterial limb of the cardiopulmonary bypass circuit to establish a second source of arterial blood flow. As the patient was being cooled to deep hypothermia [done to protect her brain], the transverse aortic arch, ductus arteriosus, left subclavian artery, and left common carotid artery were mobilized [the left subclavian artery supplies blood to the left arm, the left common carotid artery supplies the head and neck with oxygenated blood]. A vascular clamp was placed across the distal ascending aorta and the ascending aorta was transected proximally [they cut into the aorta]. Cold crystalloid cardioplegia [the root cardio is heart and plegia is paralysis, fairly straight forward from there] was delivered directly into the ascending aorta to achieve diastolic arrest. Cardioplegia was readministered at 30-minute intervals by direct aortic cannulation. A tourniquet was placed around the ductus arteriosus to exclude the pulmonary circulation [they tied off the main source of blood to the arteries that carry blood to the lungs]. The pulmonary artery was then divided at its bifurcation. An incision was made in the ascending aorta towards the sinotubular junction. A similar incision was made in the base of the pulmonary artery in the two sites were anastomosed [they joined a portion of her aorta with her pulmonary artery] with running 7-0 Prolene suture to create the root of the neoaorta. The ductus arteriosus was then separated from the pulmonary artery [this is no loner needed as blood can now flow to the lungs through the hybrid aorta/pulmonary artery they created]. The resulting defect of the pulmonary artery was closed primarily. A 6 mm Gore-Tex graft was then anastomosed to a portion of autologous pericardium [donated tissue from herself] after creating a circular defect with a punch. The pericardial skirt was then anastomosed to the distal main pulmonary artery. When the patient had adequately cooled, cardiopulmonary bypass flow was reduced [they turned down the bypass machine] and vessel loops were used to exclude the left common carotid and subclavian arteries. The base of the innominate artery was excluded with a vascular clamp to establish low-flow antegrade cerebral perfusion [they stopped blood flow to certain parts of her body when she was cool enough to maintain blood flow to the brain]. The ductus arteriosus cannula was clamped and removed. An occlusive clamp was placed across the descending thoracic aorta distal to the insertion of the ductus arteriosus. The ductus arteriosus was sharply resected. A longitudinal aortotomy was made from the transected end of the ascending aorta to the level of ductal insertion [they made a large cut in her aorta]. The midportion of the transverse arch appeared to be severely hypoplastic, measuring approximately 0.5 mm in diameter. The arteriotomy was then extended distally beyond the insertion of the ductus arteriosus for approximately 1 cm. A piece of pulmonary homograft was trimmed to the appropriate dimensions and then used to reconstruct the undersurface of the transverse arch with running 7-0 Prolene suture [I think his wording is pretty clear, but to make sure you understand, they used donor tissue to rebuild and expand her aorta]. A brief period of deep hypothermic circulatory arrest was initiated [her entire body's circulation was stopped]. During this period, a limited right atriotomy was performed and a portion of the atrial septum was excised to create an unobstructed inter-atrial pathway [they created a defect that allows blood to flow between the right and left atriums, most HLHS children have this defect already]. The right atrium was then closed with running Prolene suture and low-flow antegrade cerebral perfusion was reinitiated [they restarted blood flow to her brain]. Advancing a right angle clamp through the neoaortic valve, an appropriate site on the right ventricular free wall was selected for the origin of the Sano shunt. A circular punch was used to create a defect and the surrounding muscle was undermined sharply [i.e., they made a hole in her heart wall for the shunt]. The reconstructed ascending aorta/transverse arch was anastomosed to the reconstructed aortic root [they reconnected the aorta and and it's root after they were repaired] using running 6-0 Prolene suture. The proximal Sano shunt was then anastomosed to the right ventriculotomy [they connected the shunt to the hole they made in the right ventricle] using interrupted pledgeted mattress Prolene sutures. The vascular clamp on the descending thoracic aorta was removed, allowing the arch to fill with blood. The vascular clamp on the base of the innominate was then removed to establish antegrade blood flow through the aortic arch and cardiopulmonary bypass flow was increased [they were reopening and increasing blood flow to the heart after creating the shunt]. The patient was fully rewarmed. Vessel loops around the left common carotid artery and left subclavian artery were then released. The patient was weaned from cardiopulmonary bypass. Although ventricular function initially appeared to be adequate, global myocardial dysfunction [her heart was not beating well enough on its own] was evident on echocardiography. Visual inspection on the surface of the heart revealed appropriate filling of the left and right coronary distribution. Cardiopulmonary bypass was reinitiated to rest myocardium. After a period of approximately 30 minutes, we again weaned cardiopulmonary bypass. The patient achieved a sustainable perfusion pressure for a number of minutes. However, she subsequently began to demonstrate progressive myocardial dysfunction.

Given what appeared to be appropriate coronary artery filling and improvement of myocardial function after a period of additional cardiopulmonary bypass support, we elected to proceed with ECMO [went over this before, but to recap, a portable full heart/lung bypass machine] cannulation to support the heart during the early postoperative period. An ECMO circuit was introduced to the field. The innominate artery cannula was disconnected and then reconnected to the arterial limb of the ECMO circuit during a brief period of cessation of cardiopulmonary bypass. The right atrial cannula was then connected to the venous limb of the ECMO circuit in a similar fashion. ECMO flow was initiated. Protamine was given [Protamine counteracts Heparin, it increase pulmonary artery pressure and decreases peripheral blood pressure, myocardial oxygen consumption, cardiac output, and heart rate]. Hemostasis was obtained [they contained her bleeding to a set area]. Chest tubes were placed and secured with suture [to drain said bleeding].

The surgical site was then closed with an Esmarch dressing and an occlusive dressing was placed over this. The patient tolerated the procedure well and was taken to the Cardiac ICU in critical condition. We plan to perform ECMO decannulation once myocardial recovery has been demonstrated by echocardiography.

An appropriately trained resident was not available to assist with this procedure. I have asked the ICU team to assist in the postoperative management of this patient, including establishing hemodynamic stability, ECMO management, and ventilator management.

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