Hämodynamische auswirkungen aktueller beatmungsverfahren auf die zerebrale perfusion

Abstract

Objective The aim of our study was to investigate the effects of these new strategies [the new approach by Amato et al. (NAA) and the modified "open lung"concept (OLC)] on cerebral perfusion using an animal model. Method After inducing ARDS with a thorax contusion, 38 pigs (German Edelschwein), divided into two groups, were mechanically ventilated either with NAA or OLC over a 24 h period. Measurements of intracranial pressure (ICP), cerebral perfusion pressure (CPP), intracerebral partial pressure of oxygen (ptiO2) and transcranial Doppler ultrasound (TCD) were conducted. Results In the NAA group with a tolerance of paCO2 up to 80 mm Hg (permissive hypercapnia) a fast increase of ICP by 11.5 ± 5.4 mm Hg (p < 0.05) and a consecutive moderate decrease of CPP were observed. The elevated ICP was detected throughout the study period. The ptiO2 increased significantly from 49 ± 39 mm Hg to 84 ± 24 mm Hg. The TCD showed an increase of systolic, diastolic and mean flow velocities. In the OLC group a brief increase of ICP and a decrease of CPP were observed during the initial recruitment maneuvre (< 60 s). The TCD showed a decrease in flow velocities followed by a rapid increase. The ICP rose from 14.0 ± 5.4 mm Hg to 19 ± 6.2 mm Hg (p < 0.05) and returned to baseline values after one hour. There was no evidence of critical increase of ICP during the study period. The ptiO2 rose significantly. No negative effects of high-PEEP level were observed. Conclusion Patients with ARDS or acute lung injury additionally suffering from cerebrovascular diseases should be treated by a respiratory strategy without permissive hypercapnia, because of the negative effects of permissive hypercapnia on ICP in the NAA group. The hyperventilation that ensues with the "open lung" concept attenuates the permissive hypercapnia. There was no increase in ICP and no longer significant decrease in CPP using the "open lung" concept. There was no evidence of negative effects of PEEP levels of up to 16-20 cm H2O.