IRCT2012100811020N2 IRCT 2013-02-18 Zahedan University of Medical Sciences, Deputy of Research Effect of different methods of remifentanil administration in labor pain Comparison of Incremental Bolus and Infusion Administration of Remifentanil on Labor Pain and Length of Delivery Time in Women During Labor. 2012-01-23 anticipated 82 Complete https://irct.ir/trial/11381 interventional Randomization: Randomized, Blinding: Single blinded, Placebo: Not used, Assignment: Parallel, Purpose: Treatment. N/A Single spontaneous delivery. Intervention 1: If the intensity of pain reaches to 7 or more (based on verbal numeric grading criteria) in group A, remifentanil (in method of incremental infusion) will be prescribed from 0.025 microgram per kg of body weight of the patients in minute and If needed its dose gradually increases to 0.05, 0.075, and 0.1. For preparing, 1 mg remifentani is diluted into 100 ml of normal saline in solution (concentration of 10 micrograms per milliliter). Intervention 2: If the intensity of pain reaches to 7 or more (based on verbal numeric grading criteria) in group B, remifentanil (in method of incremental bolus) will be prescribed in dose of 0.25 microgram per kg, and If needed another bolus will be received in dose of 0.5 microgram per kg. lockout time between two boluses was 4 minutes. For preparing, 1 mg remifentani is diluted into 100 ml of normal saline in solution (concentration of 10 micrograms.