Changes in Intestinal Mucosal Microvascular Perfusion Assessed Using Orthogonal Polarisation Spectral Imaging in the Horse

Aims: Although several markers for measuring global tissue perfusion are available, there are currently no practical measurements of capillary microvascular perfusion in horses with hypovolaemia. Orthogonal polarisation spectral (OPS) imaging allows assessment of capillary microvascular perfusion by visualisation of mucosal blood flow. This study aims to demonstrate that administration of the α2 adrenoreceptor agonist detomidine, results in measurable changes in mucosal blood flow that can be determined using OPS. We hypothesise that these changes will mirror known aberrations in total peripheral resistance and cardiac output. 

Methods:Microvascular blood flow was recorded using OPS placed manually, per rectum in 6 normal horses (weighing 603 ± 134 kg) undergoing sedation for a range of clinical procedures. The OPS recordings were made prior to and following sedation (5, 10, 20 min) with detomidine (10 ug/kg bwt) and butorphanol (10 ug/kg bwt) administered by i.v. injection. Microvascular perfusion was determined using standardised methods from OPS recordings including proportion of perfused vessels (PPV), functional capillary density (FCD), microvascular flow index (MFI) and vessel density (VD). [...]