Effects of Positive End Expiratory Pressure (PEEP) on intracranial and cerebral perfusion pressure in pediatric neurosurgical patients

Background: Positive end expiratory pressure (PEEP) improves oxygenation by optimizing alveolar recruitment and reducing intrapulmonary shunt. Unfortunately, PEEP can interfere with intracranial pressure (ICP) by increasing intrathoracic pressure. We hypothesized that the use of different PEEP levels could have an effect on intracranial and cerebral perfusion pressure (CPP), gas exchange, respiratory system mechanics, and hemodynamics in pediatric patients undergoing major neurosurgical procedures.Method: Twenty-one consecutive pediatric patients undergoing surgical procedure for intracranial tumors were enrolled in this study, conducted between April 2008 and August 2009. Invasive radial pressure, central venous pressure (CVP), arterial oxygen saturation, ICP, and CPP were monitored. The middle cerebral artery mean velocity (V-med) was determined by transcranial Doppler. At 0 cm H2O (ZEEP), the following parameters were recorded: systolic, mean, and diastolic arterial pressure, CVP, ICP, CPP, V-med, and arterial blood gases. After assessment at 0 PEEP (ZEEP), PEEP 4 and PEEP 8 were applied: all parameters were recorded at each level.Results: The application of PEEP (from ZEEP to PEEP 8) significantly increased compliance of the respiratory system indexed to the weight of the patients (CrsI) (P=0.0001) without ICP modifications. No significant variations were observed in values of arterial pressure (MAP), CPP, V-med, total resistance of the respiratory system indexed to the weight of the patients (RRSmaxI), and ohmic resistance of the respiratory system indexed to the weight of the patients (RRSminI). CVP significantly increased between ZEEP and PEEP 8 (P=0.02), and between PEEP 4 and PEEP 8 (P<0.05). Partial arterial pressure of oxygen (PaO2), partial arterial pressure of carbon dioxide (PaCO2), partial arterial pressure of oxygen/inspiratory fraction of oxygen (PaO2/FiO(2)), and pH were not significantly modified.Conclusion: We describe cerebral hemodynamic responses to PEEP application in pediatrics. PEEP values up to 8 cm H2O seem to be safe in pediatric patients with intracranial neoplasm, and, in our opinion, PEEP should be applied immediately after surgery to restore lung recruitment.