Indications for continuous prostacyclin include patients with idiopathic pulmonary arterial hypertension who have a negative response to the short-acting vasodilator challenge during catheterization or those who fail other therapies. Its mechanisms of action include pulmonary artery vasodilation, inhibition of platelet aggregation, and decreased vascular wall remodeling. Current forms of therapy include subcutaneous and intravenous administration. Chronic intravenous infusion requires placement of a Hickman catheter in the subclavian vein and use of an infusion pump.
Continuous prostacyclin - discussion
The continuous use of prostacyclin improves cardiac hemodynamics, exercise tolerance and survival, especially in patients with severe symptoms at rest. The major adverse effects of long-term prostacyclin use are attributable to the delivery system involved. These adverse effects include catheter related infections and thrombosis as well as infusion pump failure.
IV continuous prostacyclin therapy photograph
This is a photograph of another patient with idiopathic pulmonary hypertension on intravenous prostacyclin therapy. The Hickman catheter that is in the subclavian vein has been tunneled subcutaneously and can be seen exiting the chest. It is connected to an ambulatory infusion pump that is in the pack attached to the patient's waist.
Lung transplantation
Lung transplantation should be considered for patients who continue to have progressive symptoms on intravenous prostacyclin. While combined heart-lung transplant was initially performed, bilateral lung transplantation has become the procedure of choice for most patients with refractory idiopathic pulmonary hypertension. With lung transplantation, the survival rate is similar, the operative mortality rate is lower and the waiting time is less than for the combined heart-lung transplant. Lung transplantation alone will lower the pulmonary artery pressure, leading to regression of right ventricular hypertrophy and improved function, thereby eliminating the need for cardiac transplantation.
Bilateral lung transplantation
Donor heart and lungs are extracted together and then separated and used in different patients. When bilateral lung transplantation is performed, each lung is replaced one at a time. Single lung anesthesia is during replacement of the opposite lung. Cardiopulmonary bypass is not employed in the majority of cases, but is available on a stand-by basis. Systemic and pulmonary arterial pressures are monitored as well as arterial and venous oxymetry, cardiac output and end tidal carbon dioxide.
Lung transplant surgery
The following lung transplant is presented through the courtesy of Cine-Med, the American College of Surgeons and Dr. Joel Cooper and was carried out at the Washington University School of Medicine.
Following completion of the thoracotomy and the transverse sternotomy, the right lung is deflated and the hilar structures are mobilized, including intrapericardial mobilization of the pulmonary artery, isolation of the pulmonary veins near the hilum of the lung and division of pleural adhesions, if any are present. The first branch of the pulmonary artery is being isolated in preparation for subsequent ligature and division.
After mobilization of the lung and the hilar structures, the right lung is re-expanded. The donor lungs have arrived. Here you see the right and left pulmonary arteries being separated at their origin. Each pulmonary artery is dissected free from the surrounding tissues to facilitate the subsequent arterial anastomoses.
Here you see the atrial cuff being divided vertically in the mid line into two atrial cuffs. surrounding respective right and left pulmonary veins.
The left main stem bronchus is initially divided near the carina. The left lung is then packed in cold, moist gauze. One-lung anesthesia is again established, the right lung collapsed and the extraction begun. Once the lung has been removed, the pericardium is opened posteriorly behind the pulmonary venous stump, as shown here. The right lung, wrapped in cold, moist gauze, is placed in the pleural space and the bronchial anastomosis is the first to be performed. A vascular clamp is then placed centrally on the pulmonary artery and its staple line trimmed from the descending branch, and end-to-end anastomosis is performed with running, non-absorbable, monofilament sutures. First, the posterior wall of the arterial anastomosis and then the anterior wall. The donor and recipient atrial cuffs are then anastomosed with running 4.0 monofilament, non-absorbable suture material. The atrial suture line is then completed, the vascular clamps are removed from the artery and the atrium and the lung is inflated.
The left thoracotomy is then completed, the left lung deflated and the left lung replacement is completed.