Changes in the Microvascular Reactivity on Leg During Spinal Anesthesia

The VOT procedure was conducted twice in each patient, before and 15 min after intrathecal injection. An NIRS sensor (INVOSTM 5100C Cerebral/Somatic Oximeter; Medtronic, Minneapolis, MN, USA) was attached to the patient's gastrocnemius muscle. A tourniquet (A.T.S ® 3000 Automatic Tourniquet System; Zimmer Inc., Warsaw, IL, USA) was applied to the thigh and inflated to a pressure value 50 mmHg over the patient's baseline systolic blood pressure in the leg and maintained for 5 min. After a 5-min ischemic period, the tourniquet was rapidly deflated to 0 mmHg. The StO2 data was continuously recorded during the VOT procedure. After confirmation of spinal anesthesia using cold sensitivity, the VOT procedure was repeated in the same manner as mentioned above. The occlusion slope and recovery slope were calculated based on the measured StO2 data.