Visualisation of cortical pO(2) during an epidural mass lesion in rodents

Monitoring p(bt)O(2) is a valuable supplemental -procedure for neurocritically ill patients. Here, we utilise an opto-chemical method for measuring cortical pO(2) during a reversibly introduced epidural mass lesion in a rat model. The sensor was placed in a cortical window of 17 ventilated Wistar rats. Inflating the balloon device over the contralateral hemisphere increased ICP. Physiological parameters and cortical pO(2) were recorded. The ICP increased from 6.2 ± 4.6 to 44.6 ± 12.6 mmHg (p < 0.001). Cortical pO(2) over arterioles changed from 28.9 ± 2.1 to 19.0 ± 2.1 mmHg (p < 0.001), over venules from 14.8 ± 1.2 to 9.9 ± 1.5 mmHg (p = 0.002) and over parenchyma from 4.1 ± 0.7 to 2.4 ± 0.8 mmHg respectively (p < 0.001), while basic physiological parameters remained constant (p > 0.05). During baseline, arterial pO(2) correlated significantly with cortex arteriole and venole pO(2), but not with cortex parenchyma pO(2). While ICP was raised, cortical pO(2) did not correlate with arterial pO(2). In this model, a moderate epidural mass lesion causes a significant decrease in cortical pO(2). Cortex parenchyma pO(2) appeared to be independent from arterial pO(2). The correlation of cortex vessel pO(2) with arterial pO(2) disappeared during the epidural mass lesion. These findings show the capability of the device to elucidate the behaviour of functionally different cortex areas at pathophysiological conditions.