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Measuring Reperfusion of the Hand of Patients Undergoing Coronary Artery Bypass Surgery Using Laser Speckle Contrast Analysis: an Objective Allen’s Test.
Stefan C. Sandker1, Erwin Hondebrink2, Jan G. Grandjean1, Wiendelt Steenbergen2.
1Thoraxcenter Twente, Enschede, Netherlands, 2Department of Biomedical Photonic Imaging, MIRA Institute for Biomedical Technology and Technical Medicine, University of Twente, Enschede, Netherlands.

OBJECTIVE: The radial artery (RA) has become a routinely used conduit for coronary artery bypass graft surgery (CABG). Prior to surgery the Allen’s test is performed to test the patency of the ulnar artery (UA). The predictive value of a positive test is 0.53. In this pilot study we investigated if laser speckle contrast analysis (LASCA) provides a more objective determination of the reperfusion time compared to the conventional Allen’s test.
METHODS: When the hand is illuminated with a coherent 660nm 75mW continuous wave laser, the backscattered light will result in constructive and destructive interference consisting of bright and dark areas, speckles. This speckle pattern will change due to movement of red blood cells. LASCA uses these changes to visualize the perfusion during the Allen’s test at 30 frames/second. The average perfusion value of each frame of a 5x5cm2 area on the palmar side of the hand is calculated and set against time (blue line). The reperfusion time is calculated using the first derivative of a 6th order polynomial curve fit (red line). The reperfusion time of the hand of patients undergoing CABG (n=18) is calculated using LASCA and is compared to the conventional Allen’s test performed by the nurse practitioner.
RESULTS: LASCA measurements showed a negative Allen’s test of both hands of eleven patients. Seven had a borderline reperfusion time of 5-6 seconds and/or a positive Allen’s test of one or both hands. These results were in agreement with the conventional Allen’s test. Furthermore, differences in reperfusion of different regions in the measured area were visible. The Figure shows an Allen’s test of a 56 year old male patient.

CONCLUSIONS: LASCA is able to visualize perfusion of the hand and measure a quick, moderate, slow reperfusion response or no reperfusion. It is technically feasible to determine the reperfusion time of the hand. LASCA could be a useful and objective tool to assess UA patency prior to harvesting of the RA as a bypass graft.

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