An Optical Technique for Real-Time Monitoring of Hemolysis During Hemodialysis

Hemolysis--the lysis of red blood cells (RBCs) causing the release of free hemoglobin (Hb) into the patient's blood--is an unavoidable side effect of any extracorporeal circulation. If not promptly detected, hemolysis and the consequent free Hb can lead to severe health risks for the patient, such as thrombosis, compromised oxygen-carrying capacity that may cause injury to the brain and other organs, and, ultimately, the death of the patient. Accurate measurement methods to detect Hb have been known for a long time. However, such methods generally exploit toxic chemicals and/or are unable to distinguish the deleterious free Hb from the Hb contained inside intact RBCs; thus they are unsuitable for inline monitoring of the extracorporeal circulation. In this paper, a simple measurement method and a measuring system for early detection of hemolysis in hemodialysis (HD) are described. The developed measuring system performs an optical analysis of the dialysis fluid in order to estimate the free Hb concentration in the blood returned to the patient, thus potentially allowing for the first time the real-time and in-line quantitative monitoring of hemolysis in HD. Moreover, the noncontact features of the proposed technique and its analyses of the waste of the hemodialyzer allow both overcoming several issues related to biological risk in medical devices and easy integration into hemodialyzers already in use. Only vast clinical trials may be able to reasonably provide a significant estimation of the achievable measurement uncertainty. Nevertheless, the reported preliminary ex vivo experiments show that hemolysis can be detected with resolution and sensitivity potentially sufficient to reduce risks for patients.