The effects of ketamine-xylazine anesthesia on cerebral blood flow and oxygenation observed using nuclear magnetic resonance perfusion imaging and electron paramagnetic resonance oximetry

Ketamine-xylazine is a commonly used anesthetic for laboratory rats. Previo us results showed that rats anesthetized with ketamine-xylazine can have a much lower cerebral partial pressure of oxygen (PtO2), compared to unanesth etized and isoflurane anesthetized rats. The underlying mechanisms for the PtO2 reduction need to be elucidated. In this study, we measured regional c erebral blood flow (CBF) using nuclear magnetic resonance (NMR) perfusion i maging and cortical PtO2 using electron paramagnetic resonance (EPR) oximet ry in the forebrain of rats under isoflurane, ketamine, ketamine-xylazine a nd isoflurane-xylazine anesthesia. The results show that in ventilated rats ketamine at a dose of 50 mg/kg does not induce significant changes in CBF, compared to isoflurane. Ketamine-xylazine in combination causes 25-65% red uctions in forebrain CBF in a region-dependent manner. Adding xylazine to i soflurane anesthesia results in similar regional reductions in CBF. EPR oxi metry measurements show ketamine increases cortical PtO2 while xylazine dec reases cortical PtO2. The xylazine induced reduction in CBF could explain t he reduced brain oxygenation observed in ketamine-xylazine anesthetized rat s. (C) 2001 Elsevier Science B.V. All rights reserved.