Pathophysiological alterations in perfused and nonperfused lungs during cardiopulmonary bypass

Pulmonary hypertension associated with cardiopulmonary bypass and cardiac surgery

BACKGROUND AND AIM

Pulmonary hypertension (PH) is frequently associated with cardiovascular surgery and is a common complication that has been observed after surgery utilizing cardiopulmonary bypass (CPB). The purpose of this review is to explain the characteristics of PH, the mechanisms of PH induced by cardiac surgery and CPB, treatments for postoperative PH, and future directions in treating PH induced by cardiac surgery and CPB using up-to-date findings.

METHODS

The PubMed database was utilized to find published articles.

RESULTS

There are many mechanisms that contribute to PH after cardiac surgery and CPB which involve pulmonary vasomotor dysfunction, cyclooxygenase, the thromboxane A2 and prostacyclin pathway, the nitric oxide pathway, inflammation, and oxidative stress. Furthermore, there are several effective treatments for postoperative PH within different types of cardiac surgery.

CONCLUSIONS

By possessing a deep understanding of the mechanisms that contribute to PH after cardiac surgery and CPB, researchers can develop treatments for clinicians to use which target the mechanisms of PH and ultimately reduce and/or eliminate postoperative PH. Additionally, learning about the most up-to-date studies regarding treatments can allow clinicians to choose the best treatments for patients who are undergoing cardiac surgery and CPB.

Cardiopulmonary bypass reduces pulmonary surfactant activity in infants

OBJECTIVE

Infants younger than 1 year of age undergoing cardiopulmonary bypass surgery often have severe lung injury necessitating increased postoperative respiratory mechanical support. Inasmuch as the mechanisms may involve an impairment of the pulmonary surfactant system, our aim was to determine whether changes of surfactant occur in such infants.

METHODS

From the day of the operation to day 7 after the operation, serial tracheobronchial small-volume lavages of 19 infants (aged 166 +/- 29 days) were fractionated into a small and a large surfactant aggregate fraction and compared with those of 13 infants without lung disease (aged 203 +/- 33 days).

RESULTS

After cardiac operations with cardiopulmonary bypass surgery, total protein in lavages was increased 3-fold to 4-fold and decreased linearly with time. Surfactant protein A was increased on day 1 and day 2 and then decreased, whereas surfactant protein B and total phospholipids were increased on day 1. The ratio of phospholipids in small and large surfactant fractions was unchanged, but the surface activity of the large-aggregate surfactant was impaired on days 1 to 3.

CONCLUSIONS

Lung injury in infants after cardiopulmonary bypass surgery involves significant biochemical and functional disturbances of the pulmonary surfactant system. Inasmuch as substitution with natural surfactant might correct these deficiencies, the potential of this approach to reduce postoperative morbidity needs to be investigated.

Diagnosis and management of postoperative pulmonary hypertensive crisis

In this paper we discuss two infants and one child who experienced a previously unreported complication after complete correction of a large, unrestrictive ventricular septal defect. Two patients had documented pulmonary hypertensive crises and severe right-heart failure secondary to hypoxia and pulmonary vasoconstriction. These crises were associated with significantly increased right ventricular (RV) peak systolic and end-diastolic pressures and right-to-left shunting via a foramen ovale which, in turn, exaggerated the hypoxis. The crises were treated successfully with tolazoline in the second and third patients. RV pressure returned to normal values and have remained normal up to 12 months postoperatively in the second patient. Although the RV pressures decreased with tolazoline in the third patient, they never reached normal values. Postoperative monitoring of pulmonary artery and RV pressures in infants with large ventricular septal defects is essential when unexplained complications are encountered. Tolazoline proved to be very effective in the treatment of two patients with pulmonary vasoconstriction secondary to hypoxia.