The relationship between pneumatic tourniquet time and the amount of pulmonary emboli in patients undergoing knee arthroscopic surgeries

Near-fatal pulmonary embolism can occur immediately after tourniquet release after orthopedic surgeries. In this study, we determined the relationship between tourniquet time and the occurrence of pulmonary emboli in 30 patients undergoing arthroscopic knee surgeries, by using transesophageal echocardiography. The right atrium (RA) was continuously monitored by transesophageal echocardiography, and the number of emboli present was assessed with the following formula: Amount of emboli = 100 X [(total embolic area in the RA after tourni-quet release) - (total area of emboli or artifact in the RA before tourniquet release)]/(RAarea). The area was assessed 0-300 s after tourniquet release by using image-analysis software. The peak amount of emboli appeared approximately 50 s after tourniquet release. In addition, there was a significant correlation between amount of emboli (Ae [%]) and tourniquet time (Ttq [min]): (Ae = 0.1 X Ttq - 1.0, r = 0.795, P < 0.01). This study suggests that acute pulmonary embolism may occur within I min of tourniquet release and that the number of emboli is dependent on Ttq.