PURPOSE: Ischemia-reperfusion injuries (I-R) of the extremities are a clinical issue in military trauma as well as civilian medicine. However, there is no reliable noninvasive monitoring tool to determine the severity of muscle damage during ischemia, or during subsequent reperfusion other than physical examination, and histological analysis is required for confirmation. In this study, we performed a non-invasive continuous wave near infrared spectroscopy (CWNIRS) measurement pre and post tourniquet induced I-R to detect muscle hemodynamic differences between 2 hours and 3 hours tourniquet applications.
METHODS: Thirteen male Sprague-Dawley rats (∼450g) were divided into two groups, 2 hours (n=6) and 3 hours (n=7) of pneumatic tourniquet application. Light source and detector probes of a CWNIRS system were placed in transmission geometry on the tourniquet applied limb. 250mmHg tourniquet pressure was applied after 10 minute baseline CWNIRS measurement of changes in oxyhemoglobin [OHb] and deoxyhemoglobin [RHb] concentration. Tourniquets were released after 2 hours or 3 hours and the recovery hemodynamics were monitored for an additional 2 hours. Rats were euthanized 24hrs post tourniquet application to examine for injury, edema and viability of muscles. Contralateral muscles served as controls for each animal.
RESULTS: In both groups, [OHb] dropped immediately, then gradually decreased after tourniquet application, then recovered once the tourniquet was released. [RHb] initially increased, then slowly decreased after tourniquets were applied. However, significant differences in hemodynamics were observed during the reperfusion phase comparing the 2 hour and 3 hour tourniquet groups. While release after 2 hours of tourniquet caused [OHb] to overshoot above the baseline during reperfusion, 3 hour group continued to have lower [OHb] than the baseline [OHb]. We found significant correlation between the elapsed time from tourniquet release to the 1st recovery peak of [OHb] and wet muscle weight ratio between tourniquet and contralateral limb muscles (R=0.86).
CONCLUSION: Hemodynamic patterns from non-invasive CWNIRS demonstrated significant differences between 2 hour and 3 hour I-R.
CLINICAL IMPLICATIONS: Non-invasive CWNIRS may be used as a non-invasive prognostic tool of I-R in extremities.
DISCLOSURE: Jae Kim, No Financial Disclosure Information; No Product/Research Disclosure Information