Effect of positive end-expiratory pressure on splanchnic perfusion in acute lung injury

Byline: P. Kiefer (1), S. Nunes (1), P. Kosonen (1), J. Takala (1) Keywords: Key words Acute lung injury; Pressure gradients; PEEP; Splanchnic perfusion Abstract: Objective: To evaluate the acute effects of an increased positive end-expiratory pressure (PEEP) on splanchnic tissue perfusion.APDesign: Clinical prospective study.APSetting: Intensive care unit in a university clinic.APPatients: Six patients with severe acute lung injury (ALI) requiring mechanical ventilation. All patients had bilateral infiltrates in chest X-ray, PaO.sub.2/FiO.sub.2 < 200 mmHg and stable hemodynamics without vasoactive drugs.APInterventions: PEEP was increased by 5 cm[H.sub.2]O from a clinically selected PEEP level (8/6--11 cm[H.sub.2]O) up to (13/10--14 cm[H.sub.2]O) followed by a return to baseline.APMeasurements and main results: Splanchnic blood flow was measured using primed continuous infusion of indocyanine green dye with hepatic venous sampling and systemic hemodynamics by routine monitoring. In addition, we estimated gastric mucosal-arterial PCO.sub.2 difference and splanchnic lactate/pyruvate exchange. After a baseline measurement, PEEP was increased. After 60 min all measurements were repeated. PEEP was returned to the baseline level and a third measurement followed. PEEP had no effect on cardiac index (baseline I: 3.2/6.1--2.5 l/min/m.sup.2 PEEP: 3.3/5.7--AP2.3 l/min/m.sup.2 baseline II: 3.4/6.0--2.5 l/min/m.sup.2) neither did PEEP have any effect on splanchnic blood flow (baseline I: 0.91/1.39--0.62 l/min/m.sup.2 PEEP: 1.04/1.75--0.54 l/min/m.sup.2 baseline II:1.07/1.42--0.68 l/min/m.sup.2, respectively) or perfusion (gastric mucosal-arterial PCO.sub.2 difference baseline I: 2.1/12.8--0.6 kPa PEEP: 1.7/14.5--0.7 kPa baseline II: 1.7/8.8--0.1 kPa lactate uptake baseline I: 0.5/1.1--0.3 mmol/min/m.sup.2 PEEP: 0.4/1.0--0.3 mmol/min/m.sup.2 baseline II: 0.5/0.9--0.3 mmol/min/m.sup.2 hepatic venous lactate/pyruvate baseline I: 9.7/10.6--5.7 PEEP: 9.7/14.2--6.4 baseline II: 8.4/12.4--7.3 respectively).APConclusion: PEEP by itself does not have a consistent effect on splanchnic blood flow and metabolism when cardiac index is stable and patients are ventilated within the linear part of the pv curve. Author Affiliation: (1) Critical Care Research Program, Division of Intensive Care, Department of Anesthesiology and Intensive Care, Kuopio University Hospital, 70 210 Kuopio, Finland, e-mail: jukka.takala@insel.ch, Tel.: + 31-41-6 32 44 00 Fax: + 31-41-6 32 41 00, FI (2) Department of Intensive Care Medicine, University Hospital of Bern (Inselspital), 3010 Bern, Switzerland, CH Article note: Received: 29 April 1999/Final revision received: 17 November 1999/Accepted: 2 February 2000