Observation of Leukocyte Kinetics Using Handheld Vital Microscopes During Surgery and Critical Illness

Abstract

Leukocyte recruitment and adhesion to the endothelial wall are hallmarks of systemic inflammation that occur during several conditions, such as sepsis, ischemia/reperfusion injury and cardiac surgery. Monitoring of microcirculatory leukocytes is a potential candidate tool to assess the inflammatory and pathophysiological status of the patient at the bedside. In the last few years, new methodologies have been introduced using hand-held vital microscopy to monitor microcirculatory leukocytes in surgical and critically ill patients. These methods have been validated to assess microcirculatory leukocyte kinetics at the bedside of the patient. The three methods applied by hand-held vital microscopy to identify leukocytes are known as the conventional manual counting method, the frame averaging method and the space-time diagram method. The conventional manual counting method is accomplished by visual counting of rolling leukocytes. This method cannot distinguish between microcirculatory leukocytes and plasma gaps. The frame averaging method has been developed to distinguish between rolling leukocytes and plasma gaps. This method transforms and filters microcirculatory video-clips in such a manner that red blood cells (RBCs), plasma gaps and non-rolling leukocytes can be distinguished thereby allowing quantification of the number rolling leukocytes. The space-time diagram was developed to measure the velocity of leukocytes and to distinguish and quantify the number of rolling, non-rolling leukocytes in the microcirculation. All three methods have shown increased microcirculatory leukocytes in states of systemic inflammation during surgery and critical illness enabling integration with conventional microhemodynamic assessment using hand-held vital microscopy for point-of-care use at the bedside.