Updates in Anesthetic Management of Congenital Diaphragmatic Hernia

Abstract

SUMMARY T he diaphragm forms between 4 and 8 weeks' gestation and divides the coelomic cavity into the pleural and peritoneal cavities. The central tendon derives from the transverse septum, and the peripheral muscular portion of the diaphragm arises from the posterolateralpleuroperitoneal membranes, which eventually fuse with the transverse septum. Failure of this fusion is the cause of posterolateral diaphragmatic hernia (so-called foramen of Bochdalek hernia). Because the left side of the diaphragm closes after the right side, most diaphragmatic hernias occur on the left. 85% to 90% of CDHs are on the left side, and most of these contain small bowel, spleen, stomach, and colon; occasionally the left lobe of the liver is found in the defect. Right-sided hernias usually contain the right lobe of the liver and intestine, and they sometimes have a delayed presentation. The pathophysiology in CDHs reflects an interface between pulmonary hypoplasia and pulmonary hypertension. Displacement of the abdominal viscera into the thoracic cavity during gestation prevents normal growth and development of the ipsilateral lung. In addition, the mediastinal shift that occurs during gestation contributes to pulmonary hypoplasia of the contralateral lung. Several pharmacologic agents have been used to reduce pulmonary hypertension, such as prostaglandin E, acetylcholine, histamine, bradykinin, nitroprusside, fentanyl sedation, general anesthesia, and tolazoline, however. Inhaled nitric oxide has been shown to be a potent pulmonary vasodilator, but it has been disappointing in that few seriously ill infants receive significant benefit. Inotropic agents, such as dopamine and dobutamine, seem to help the pulmonary hypertension by increasing systemic blood pressure, which minimizes right-to-Ieft shunting through the patent ductus arteriosus. Acidosis and hypercarbia increase pulmonary vascular resistance, whereas alkalosis and hypocarbia cause pulmonary vasodilation. Spontaneous low mean airway pressure ventilation and permissive hypercapnia have shown great promise. Stabilization of cardiorespiratory system. Endotracheal intubation is critical, nasogastric or orogastric tube placement, Permissive hypercapnia and stable hypoxemia (>80%), associated with survival of 76%. Delayed repair (24 to 72 hours) improves survival when compared with early emergent repair. Allows stabilization of the infant before surgical repair. 1/3 of patients will require ECMO. Reports of 70% survival by Bohn with early use of HFOV and ECMO for patients unable to be stabilized on reasonable ventilatory setting (pH.7.25, Peak Pressures <30 cm H2O, pre-ductal SO2 >90% with FiO2 <60%). Inhaled nitric oxide (iNO) beneficial in isolated PPHN. Careful attention to right sided heart failure increases survival by 10%. Finally, the introduction of ECMO and HFOV, in parallel with advances in other aspects of treatment, improved the results and the top institutions reported survivals approaching 90% although, sometimes, their statistics excluded chromosomal aberrations, multiple malformations and even some patients that did not reach surgery.