The effect of anesthetic induction on subcutaneous blood flow in various areas of the human face, assessed using infrared method based on three temperatures

Assessment of microcirculation is of considerable interest in both research and clinical practice, as it provides information on local tissue perfusion. Information on the state of the microvascular bed is important in several metabolic and cardiovascular disorders, in critically ill patients, and during anesthesia. In this study, the feasibility of deriving clinically relevant parameters using infrared thermography was explored. The effect of anesthetic induction on the temperature dynamics of different facial regions driven by changes in blood flow was investigated. The method was based on a skin heat-balance model that enables estimation of thermal perfusion indices using three relevant temperatures (skin, ambient, core). The study was conducted in a cohort of patients undergoing anesthetic induction prior to cardiac surgery. The observed increases in thermal perfusion indices over the nose, cheeks, medial corners of the eyes, and forehead are most likely attributable to reduced sympathetic activity. The vasoplegic effect of anesthetic induction enabled validation of the proposed thermal method for assessing local perfusion abnormalities manifested on facial skin.