A scanning fluorometer for imaging ischaemic areas in traumatized muscle

The criteria used to evaluate the state of muscle surrounding a bullet wound are: a lack of contractility, a lack of capillary bleeding, and changes in colour and consistency. Muscle with all these properties may be assumed to be irreversibly damaged. However, the boundary between such tissue and tissue with potentially reversible levels of damage may not be clear cut. In general, oxygen lack due to blood vessel damage may be sufficient to cause irreversible damage or may result in a site of anaerobic infection. Such areas may occur at some distance from the missile track. Tissue responses to oxygen lack can be monitored by observing changes in intrinsic cellular fluorescence. The blue autofluorescence of intracellular pyridine nucleotides increases with anoxia, whereas the green autofluorescence of intracellular flavoprotein has been found to decrease with anoxia. We have developed a scanning fluorometer which rapidly provides an image of the distribution of anoxic areas in soft tissues. In experiments with anaesthetized rabbits, occlusion of the blood vessels to the gracilis muscle caused an increase in its pyridine nucleotide fluorescence and a decrease in its flavoprotein fluorescence. The changes were hastened by stimulation of the muscle to fatigue. Arterial infusion of colloidal carbon confirmed that adjacent muscles still had a blood flow. The apparatus has potential for the identification of hypoxic zones peripheral to the permanent wound cavity. Conversely, it may also help to indicate whether vascular repair after trauma of large blood vessels has led to improvement of the metabolic status of tissue being reperfused.