Study objective: To Determine the effect of sedation protocol using Richmond Agitation-Sedation Scale (RASS) on clinical outcomes of mechanically ventilated patients in Intensive Care Unit (ICU) Study design: Single blind Randomized Clinical Trial, including intervention and control groups, single center, phase 1 trial. Study method: a) Sample size: A total of 90 patients will randomly divided into two groups of intervention and control group (N= 45 for each group). b) Randomization: All the eligible patients will be included in the study from Feb 2017 to May 2017 (The Poisson simple random sampling). The first five patients will be allocated to the intervention (head) or control (tail) group, and the second five patients will be allocated to the other group (tails) using tossing a coin. c) Intervention: In this study, the control group will receive the routine treatment and sedation according to the patients' physiological reactions and nurses' clinical judgment to control pain. In the intervention group the control of pain and sedation will be managed using a researcher-made designed protocol. In the proposed protocol, the sedation level of patients will be assessed and recorded using RASS Scale each hour, at the same time of assessment of patients' vital signs by nurses. No particular intervention will be needed if the score is less than -2. If the patient’s Richmond score is between 1 and -1, sedation drugs will be infused just before invasive procedures. However, the patient will receive the appropriate nursing interventions (non-drug interventions) such as repositioning, reducing the endotracheal tube pressure on mouth or nose, reducing environmental noise, etc. if their sedation level score is more than +2. If the patients are sedated, the sedation level will be checked hourly; otherwise, the RASS Scale will be applied and the sedative drugs will be administered according to the patient’s medication order. d) Intervention duration: The scoring of patients' sedation level will be assessed using RASS scale, and the appropriate interventions (drug and non-drug) will be done hourly during the mechanical ventilation (maximum of 10 days) throughout the day (24 hours). e) Outcomes under study: Ventilation duration, ICU stay duration, the final outcomes including transferring from the ICU and death.