Development of a piglet model for cerebrovascular autoregulation assessment with altered PaCO2

Abstract

IntroductionCerebrovascular autoregulation (CA) capacity can be impaired in the aftermath of acute brain injuries. Altered physiological states, such as hypo- and hypercapnia, affect CA. Although these effects have been demonstrated in several animal experiments, the exact effect of PaCO₂ on the plateau of cerebral blood flow (CBF) across the spectrum of arterial blood pressures has not been fully disclosed. Research QuestionThe aim was to explore pial vasodynamics in response to changing PaCO₂ in a porcine cranial window model, as preparation for an experimental setup in which the CBF plateau position is investigated under different PaCO₂ conditions. Material and MethodsFive piglets were brought under anesthesia, intubated, ventilated and instrumented with a cranial window through which pial arteriolar diameters could be microscopically observed. By changing ventilation to either hyper- or hypoventilation we were able to investigate a range of PaCO2 from 25 till 90mmHg. ResultsAltering the respiratory rate to manipulate PaCO₂ by ventilation appeared to be feasible and reliable. Discussion and ConclusionWe found that ETCO₂ reliably represents PaCO₂ in our model. Pial arteriolar diameter changes followed the direction of PaCO₂ changes, but the effect of PaCO₂ on the diameters was not linear. Only in the hypercapnia setting did we observe a clear and consistent vasodilation of the pial arterioles.