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Effect of positive end-expiratory pressure on splanchnic perfusion in acute lung injury
1Department of Anesthesiology and Intensive Care, Kuopio University Hospital, Finland.
Objective:
To evaluate the acute effects of an increased positive end-expiratory pressure (PEEP) on splanchnic tissue perfusion.
Design:
Clinical prospective study.
Setting:
Intensive care unit in a university clinic.
Patients:
Six patients with severe acute lung injury (ALI) requiring mechanical ventilation. All patients had bilateral infiltrates in chest X-ray, PaO2/FiO2 < 200 mmHg and stable hemodynamics without vasoactive drugs.
Interventions:
PEEP was increased by 5 cmH2O from a clinically selected PEEP level (8/6-11 cmH2O) up to (13/10-14 cmH2O) followed by a return to baseline.
Measurements 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 PCO2 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/m2; PEEP: 3.3/5.7-2.3 l/min/m2; baseline II: 3.4/6.0-2.5 l/min/m2); neither did PEEP have any effect on splanchnic blood flow (baseline I: 0.91/1.39-0.62 l/min/m2; PEEP: 1.04/1.75-0.54 l/min/m2; baseline II: 1.07/1.42-0.68 l/min/m2, respectively) or perfusion (gastric mucosal-arterial PCO2 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/m2; PEEP: 0.4/1.0-0.3 mmol/min/m2; baseline II: 0.5/0.9-0.3 mmol/min/m2; 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).
Conclusion:
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.