Abstract
Background and Objectives
Laser irradiation induces blood coagulation by heating of blood components. It is a complex phenomenon which encompasses a variety of processes, such as cell shape modification, cell membrane rupture, protein denaturation, aggregation, and finally blood gelation. An in vitro study was performed to investigate heating temperatures leading to transformation of blood and to have a better understanding of the dynamics of temperature dependent modifications of blood in the nearβinfrared.
Study Design/Materials and Methods
Slow heating of whole blood and hemolized blood was performed using a specific optical chamber. Eight hundred and five and 940 nm light transmission of blood was measured as a function of time during heating at various temperatures (60β75Β°C).
Results
During heating of whole blood, three phases were clearly identified. For hemolized blood, only phase 3 was present. For whole blood, the duration of each phase was correlated to blood temperature. A temporary increase of transmission was observed during heating with a maximum at 65Β°C. The analysis of the dynamics of temperature dependent modifications of blood are consistent with cell shape modification, denaturation, and aggregation of blood, resulting in the formation of an aqueous gelβmatrix.
Conclusions
βSlowβ vessel heating which is now proposed as the optimal mechanism for permanent vessel closure should be reconsidered in terms of our results. In that particular case, the optical coefficients of blood could be different from those expected. In case of a large blood vessel, this could be an advantage since a βtemporaryβ higher transmission of light could lead to a more homogeneous heating of the blood vessel. In case of a small blood vessel, this phenomenon could lead to a collateral damage of the skin. Lasers Surg. Med. 00:1β7,2005. Β© 2005 WileyβLiss, Inc.