Background: Deep vein thrombosis (DVT) is a major complication in critical care. There are various methods of prophylaxis, but none of them fully prevent DVT, and each method has adverse effects. Electrical muscle stimulation (EMS) could be a new effective approach to prevent DVT in intensive care unit (ICU) patients. We hypothesized that EMS increases the venous flow of the lower limbs and has a prophylactic effect against the formation of DVT. Methods: This study included 26 patients admitted to a single ICU. We enrolled patients who could not move themselves due to spinal cord injury, head injury, central nervous system abnormalities, and sedation for mechanical ventilation. The patients were randomly allocated to either the EMS group or the control group. Patients in the EMS group received 30-min sessions of EMS applied to the bilateral lower extremities on arbitrary days within 14 days after admission. The control patients received no EMS. The peak flow velocity and diameter of the popliteal vein (Pop.V) and common femoral vein (CFV) were measured by ultrasound and then the volumes of venous flow were calculated using a formula. Results: There were no statistically significant differences in patient characteristics between the two groups except for the mortality rate. In the EMS group, the median and interquartile range (IQR, 25th-75th percentile) of velocities of the Pop.V and CFV were higher during EMS compared with at rest: 10.6 (8.0-14.8) vs 24.5 (15.1-37.8) cm/s and 17.0 (12.3-23.8) vs 24.3 (17.0-33.0) cm/s, respectively (p &lt
0.05). The median (IQR) of volumes of venous flow of the Pop.V and CFV at rest and during EMS were 4.2 (2.7-7.2) vs 8.6 (5.4-16.1) cm3/s and 12.9 (9.7-21.4) vs 20.8 (12.3-34.1) cm3/s, respectively (p &lt
0.05). There were no major complications related to EMS. Conclusions: EMS increased the venous flow of the lower limbs. EMS could be one potential method for venous thromboprophylaxis. Trial registration:UMIN000013642