Background: This study aimed to find out the optimal time delay of epinephrine in one-per-mil tumescent solution containing 1:1,000,000 epinephrine and 0.2% lidocaine to achieve optimal visualization in hand surgery. Materials and methods: Twelve healthy male subjects who volunteered to join this prospective, randomized, double blind study were selected with convenient sampling technique. The subject's hand and the solution, either the one-per-mil or normal saline solution, were randomly selected. Injections were given to the ring finger's pulp, whereas the oxygen saturation (SpO 2 ) of each finger was measured with Masimo's Radical-7 Pulse Oximeter at 5 min before injection and continuously up to 45 min after injection. The device showed the SpO 2 every 2 s. Any value of SpO 2 was noted if it stayed the same point for at least 30 s in a row without interruption. The time of the lowest SpO 2 was recorded and analyzed. Results: The average of SpO 2 after injection in the epinephrine group was 96.5 (95-97), P = 0.002, whereas the normal saline group was 97.5 ± 1.168, P = 0.003. Both were statistically significant compared with their respective baseline values. The average delta SpO 2 of the epinephrine group was 3.42 ± 0.996, whereas the normal saline group was 1.50 ± 1.567 (P = 0.001; CI 0.923-2.911). The time to achieve the lowest SpO 2 in the epinephrine group was obtained at the average time of 13.90 ± 5.38 min after injection. Conclusions: The optimal time delay of the epinephrine in the one-per-mil tumescent solution was 13.90 ± 5.38 min after injection.