Preliminary exploration of tissue oxygen saturation index using near-infrared spectroscopy in two infants of neonatal catheter-associated venous thrombosis

Near-infrared spectroscopy (NIRS) is commonly used for monitoring oxygen saturation in brain and abdominal tissues, while reports on the monitoring of local tissue oxygen saturation in limbs are very limited. This study observed the changes in limb tissue oxygen saturation index (TOI) in two infants of catheter-related venous thrombosis (CRT) and preliminarily investigated their correlation. This study involved two infants who experienced limb catheterization complicated by venous thrombosis. NIRS was employed for the continuous monitoring of TOI prior to, during, and subsequent to urokinase thrombolysis. The safe TOI range was established at 58%–68% ±2; a reduction above 20% from baseline signified an anomaly. Changes in skin color and temperature of the affected limb were simultaneously observed, and the thrombolytic effect was comprehensively assessed using vascular ultrasound. Infant 1 was diagnosed with right iliac vein thrombosis; after 144 h of thrombolytic therapy, the TOI of the affected lower limb returned to the normal range, with no abnormalities in limb skin temperature or circumference. Infant 2 involved axillary vein thrombosis near the subclavian vein; following 17 h of combined thrombolysis and anticoagulation therapy, TOI values in both upper limbs became balanced, and ultrasound follow-up revealed no residual thrombus, indicating restored venous patency. NIRS-monitored limb tissue oxygen saturation index can indicate the local venous filling status, which may facilitate the assessment of thrombolytic efficacy and the surveillance of thrombus formation.