A critical analysis of renal blood flow distribution during hemorrhage in dogs

Renal blood flow (RBF) and its distribution were measured before and during hemorrhage by utilizing: 1) and electromagnetic flowmeter, 2) radioactive microspheres, 3) 85Kr washout and 4) a freeze-dissection 85Kr disappearance technique. Before hemorrhage, total RBF was 3.48 and 3.56 ml/g.min measured with microspheres and flowmeter. Outer cortical flow was 6.65 and 7.56 ml/g.min measured with microspheres and freeze-dissection respectively while inner cortical flow was 5.15 and 4.38 ml/g.min. After hemorrhage, total flow as measured with either method was 2.3 ml/g.min. Outer and inner cortical flow (3.85 and 3.08 ml/g.min respectively) measured with microspheres was higher than that measured by freeze-dissection (1.54 and 1.60 ml/g.min). The data suggest that preglomerular renal blood flow distribution may be different than cortical capillary flow distribution, especially during hemorrhage. The freeze-dissection technique provides flow rates for the outer medulla that are closet to component II (outer medullary flow) of any of the components of the externally monitored inert gas washout. Components I and II of the externally monitored washout may represent whole cortex and subcortical outer medulla respectively.