Introduction
Near-infrared spectroscopy (NIRS) can be used as a non-invasive monitoring technique for regional cerebral oxygenation (rScO 2 ). We studied basal rScO 2 , after atropin blockade and after hypertensive testing by phenylephrin in a cardiac muscarinic receptor overexpression rabbit strain with severe cardiac pauses (H) compared to a normal rabbit strain (N).
Results
– rScO 2 values are systematically higher in H rabbits compared to N rabbits: (H = 75.6% ± 5.6 vs N = 60.7% ± 5.7, n = 6 in each group, P < 0.05);
– Atropin decrease rScO 2 in both groups, but this reduction is more marked in H rabbits ( Fig. 1 );
– During the phenylephrin test, the cardiac pauses in the H group are longer than in the N group (H: 24 285 ms ± 8 837 [ n = 6] vs N: 3 566 ms ± 1 455 [ n = 8]).
We observed a progressive hypoxia with rScO 2 decrease in both groups during the test. Unexpectedly, the rScO 2 reduction is not as pronounced in H rabbits with severe cardiac pauses as in the N group ( Fig. 1 ).
Conclusion
These data support the hypothesis that: A higher rScO 2 by NIRS could reflect a higher central muscarinic receptor density, protecting brain against hypoxia. RScO 2 could be a non-invasive muscarinic receptor overexpression marker, useful in vasovagal syncope study.
