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Monitoring of skeletal muscle ischemia using near infrared spectroscopy

University of British Columbia

Early diagnosis of acute limb muscle ischemia (LMI) is essential in order to avoid serious, irreversible local and systemic complications resulting in loss of the limb or even death. To date, techniques for monitoring LMI are limited by lack of a feasible and reliable monitoring method. Purpose: The main purposes of this thesis were to examine the feasibility and convergent validity of conventional and wireless near infrared spectroscopy (NIRS) for continuous monitoring of skeletal muscle oxygenation and hemodynamics during transient and long-term LMI and to investigate the predictive value of NIRS-derived data for evaluation of limb muscle oxidative changes during tourniquet-induced LMI. Methods: Following a complete literature review (Chapter 2), forearm muscle oxygenation and hemodynamics were studied in 10 healthy subjects using wireless NIRS instrumentation during isometric muscle contraction and tourniquet-induced LMI (Chapter 3). In Chapter 4, changes in NIRS-derived leg muscle oxygenation and hemodynamics, in conjunction with muscle oxidative changes, following tourniquet-induced LMI were investigated in 17 patients undergoing surgery for ankle fracture. In Chapter 5, the effect of electromagnetic interference (EMI) from 3 commonly used surgical instruments on NIRS signals were investigated using a mathematical method of signal analysis. Results: Chapter 2: No validated monitoring method for early detection of acute LMI was revealed. Chapters 3-4: Wireless and conventional NIRS data were consistent with muscle ischemia and reperfusion. Chapter 4: An average of 43.2±14.6 minutes of tourniquet-induced ischemia led to a 172.3±145.7% (range: 10.7-363.3%) increase in muscle protein oxidation (P<0.0005). Changes in NIRS-derived muscle oxygenated and total-hemoglobin were both negatively correlated, while reoxygenation-rate was positively correlated (P<0.05) to muscle protein oxidation. Chapter 5: EMI from 3 OR instruments was found to have no effect on NIRS signals (P<0.01). Conclusions: NIRS is a feasible method for continuous monitoring of limb muscle oxygenation and hemodynamics during transient and long-term tourniquet-induced ischemia. Tourniquet-induced LMI of 21-74 minutes leads to oxidative muscle damage. A significant negative association between the extent of tourniquet-induced oxidative damage and changes in NIRS-derived local muscle oxygenated blood volume was found. EMI of commonly used orthopedic surgical instruments does not affect NIRS signals.

Text

2011-03-21

Attribution-NonCommercial-ShareAlike 3.0 Unported

http://hdl.handle.net/2429/32630

Experimental Medicine

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-sa/3.0/