Effects of an aorticopulmonary shunt on lung fluid balance in the young lamb.

We studied the effects of increased pulmonary blood flow on lung fluid balance in seven chronically instrumented lambs (18 +/- 1 d) with surgically created aorticopulmonary shunts. We measured mean pulmonary arterial and left atrial pressure (LAP), pulmonary blood flow, lung lymph flow, and lymph (CL) and plasma (CP) protein concentration with the shunt closed and opened. With the shunt partially open, a 35% increase in pulmonary blood flow resulted in an increase in pulmonary arterial pressure (15.5 +/- 1 to 19.5 +/- 1 torr) and LAP (2.0 +/- 0.5 to 3.5 +/- 0.5 torr). Lung lymph flow nearly doubled (1.53 +/- 0.28 to 2.83 +/- 0.52 mL/h) whereas the CL decreased (4.1 +/- 0.1 to 3.4 +/- 0.1 g/dL) resulting in a decrease in the CL/CP ratio (0.67 +/- 0.01 to 0.58 +/- 0.01). With the shunt fully open, pulmonary blood flow increased 65% over baseline, pulmonary arterial pressure increased from 16.5 +/- 2.0 to 26.5 +/- 5 torr, and LAP increased from 1.5 +/- 0.5 to 6.5 +/- 2.0 torr. Lung lymph flow increased (1.1 +/- 0.2 to 3.1 +/- 0.2 mL/h) whereas CL (4.1 +/- 0.1 to 3.1 +/- 0.3 g/dL) and CL/CP (0.66 +/- 0.02 to 0.51 +/- 0.05) decreased. All changes were statistically significant (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)