Pathophysiology of congenital diaphragmatic hernia. V. Effect of exogenous surfactant therapy on gas exchange and lung mechanics in the lamb congenital diaphragmatic hernia model.

The aim of this study was to assess the impact of surfactant deficiency on the pathophysiology of congenital diaphragmatic hernia (CDH). Pregnant ewes were operated on at 80 days of gestation for creation of a diaphragmatic hernia in the lambs. Twenty-one lambs survived to be delivered by cesarean section and were studied. Compliance was improved when surface tension effects were removed by saline solution in lungs of both control animals and lambs with CDH; however, the lungs of the lambs with CDH still had significantly impaired compliance. In a second series of experiments, two groups were studied: a surfactant-treated and a control, nontreated group. Surfactant was given prophylactically into the liquid-filled lungs before the first breath. All lambs were paralyzed and sedated and their lungs mechanically ventilated with 100% oxygen for 30 minutes; gas exchange was then assessed, pressure-volume data were obtained, and compliance was calculated. Surfactant significantly improved gas exchange; arterial oxygen pressure increased from 39 +/- 11.4 to 316 +/- 53.6 mm Hg, arterial carbon dioxide pressure decreased from 148 to 63 mm Hg, and pH increased from 6.87 to 7.16 (p < 0.001). Lung volume at 25 cm H2O, functional residual capacity, and compliance were all increased (p < 0.02). Thus, in the CDH lamb model, pulmonary mechanics are impaired by both parenchymal and surfactant abnormalities. Both lung mechanics and gas exchange are markedly improved by exogenous surfactant therapy.

Chronic intestinal pseudo-obstruction with meconium ileus at onset.

Cystic fibrosis is most often the underlying cause of meconium ileus. We describe the diagnosis and treatment of a patient with chronic intestinal pseudo-obstruction, and not with cystic fibrosis, whose initial manifestation was meconium ileus.

Hypovolemic shock and intestinal ischemia: a preventable complication of incomplete formula labeling.

A 19-day-old male infant was seen with full-thickness gangrene of the transverse colon. Hyperosmolar formula feedings caused by inadequate "directions for use" was the probable cause. Improved formula labeling might prevent further cases.

Contact lens complications.

Contact lens wearers who develop complications related to their lens use are likely to present to emergency departments for care. The pathophysiology of contact lens complications is outlined, and clinical presentations of various conditions related to both soft and hard lens wear are summarized. Guidelines for emergency department management are suggested.

Differential expression of N-ras in metaplastic retinal pigmented epithelium.

Changes in expression of proto-oncogenes have been suggested as a key element in controlling the proliferative and differentiated status of a cell. We studied the expression of several of these genes in proliferating normal and metaplastic RPE cells. Using cDNAs to the c-myc, N-ras and n-myc genes we performed Northern blot analysis on the cytoplasmic RNA in normal and metaplastic RPE cells. We found that proliferating normal and metaplastic RPE cells exhibit similar patterns of expression of the c-myc gene. In contrast, when compared to normal cells, proliferating metaplastic RPE cells exhibited early and abnormally high levels of a 4 kb N-ras RNA. These changes in N-ras expression precede the vitreous-induced phenotypic change from an epithelial to a fibroblastic morphology. Understanding what role, if any, the N-ras gene plays in this metaplasia may lead to a better understanding of proliferative disorders such as proliferative vitreoretinopathy.