Peripheral lymph flow in sheep with bacterial peritonitis: evidence for increased peripheral microvascular permeability accompanying systemic sepsis.

We studied the effects of systemic sepsis on peripheral microcirculatory fluid exchange by examining changes in flow (Qlymph) and lymph-to-plasma [L/P] total protein and albumin ratios from lymph draining, the efferent duct of a prefemoral lymph node in sheep, before and during surgically-induced peritonitis. After baseline study, peritonitis was produced by cecal ligation, perforation, and devascularization. By 24 hours blood cultures revealed a polymicrobial bacteremia. The hemodynamic response to the septic insult during the 72-hour study period was characterized by an increase in heart rate and an initial fall in stroke volume index; yet, the mean blood pressure remained unchanged from baseline levels throughout the study protocol. The intrapulmonary shunt fraction increased (p less than 0.05) by 48 hours, as did both the Qlymph (2.6 +/- 1.9 ml/hr to 6.8 +/- 4.6 ml/hr; p less than 0.05) and the calculated lymph albumin clearance (1.6 +/- 1.2 ml/hr to 3.1 +/- 1.7 ml/hr; p less than 0.05). Although the calculated serum to interstitial colloid osmotic pressure gradient fell (F = 4.37; p less than 0.04), both the [L/P] total protein and albumin ratios were unchanged from baseline throughout 72 hours of study. Further, [L/P] total protein ratios were unrelated to Qlymph (r = -0.20); as Qlymph (experimental/baseline) increased with sepsis, [L/P] total protein ratio (experimental/baseline) did not fall (r = +0.62). We therefore conclude that systemic sepsis, as represented by this model of bacterial peritonitis, results in increased peripheral microcirculatory fluid flux that is primarily a consequence of an increase in permeability of the peripheral microvascular exchanging membrane.