Splanchnic perfusion during hemodialysis: Evidence for marginal tissue perfusion

Objective: Splanchnic perfusion may he compromised during hemodialysis beca use of hypovolemia, inflammatory response, and blood flow redistribution. T he aim of this study was to assess the response of splanchnic blood flow an d oxygen transport to hemodialysis. Design: A prospective clinical study. Setting: A mixed medical-surgical intensive care unit in a university hospi tal. Patients: Nine patients with acute renal failure, Interventions: A 4-hr period of hemodialysis. Measurements and Main Results: Systemic (via a pulmonary artery catheter), hepatosplanchnic, and femoral (via dye dilution) blood flow and gastric muc osal Pco(2) were measured before, during, and 2 hrs after hemodialysis. Dur ing hemodialysis, despite unchanged arterial blood pressure, cardiac output and stroke volume decreased from 3.0 +/- 1.0 L/m(2)/min (mean +/- SD) to 2 .3 +/- 0.7 L/m(2)/min (p = .02), and from 38 +/- 16 mL/m(2)/min to 28 +/- 1 2 mL/m(2)/min (p = .01), respectively. Splanchnic but not femoral blood flo w decreased from 0.9 +/- 0.3 L/m(2)/min to 0.7 +/- 0.2 L/m(2)/min (p = .02) , The blood flows returned to baseline values after dialysis without need f or therapeutic interventions, Gastric mucosal-arterial Pco(2) gradients wer e high before dialysis (35 +/- 23 torr [4.6 +/- 3.1 kPa]) and did not chang e. Renin but not atrial natriuretic peptide concentration increased during hemodialysis from 13 +/- 13 mug/L to 35 +/- 40 mug/L and decreased afterwar d to baseline values (13 +/- 13 mug/L; p = .01). Whereas interleukin 6 tend ed to decrease, tumor necrosis factor cy increased during hemodialysis from 74 +/- 24 pg/mL to 86 +/- 31 pg/mL and continued to increase after hemodia lysis to 108 +/- 66 pg/mL (p = .022). Conclusion: Hemodialysis and fluid removal in normotensive patients with ac ute renal failure may result in a reduction of systemic and splanchnic bloo d flow that is undetectable using traditional clinical signs. In contrast t o what is observed in hypovolemia, the changes in regional blood flow are r apidly reversible after hemodialysis.