The primary aim of this clinical trial is to compare the effectiveness of fentanyl vs morphine as analgosedation in mechanically ventilated adult patients in the ICU. This study also aims to compare the outcomes of patients between the two groups.

The main questions it aims to answer are :

1. Does propofol and fentanyl infusion as analgo-sedation achieve targeted sedation score at 12 and 24 hours compared to propofol and morphine infusion in mechanically ventilated adult patients in the intensive care unit (ICU)?
2. Is there a difference between the proportion of patients requiring rescue sedation dose between the fentanyl and morphine groups?

Researchers will randomize patients into 2 groups (Fentanyl and Morphine) and will start study drug accordingly for sedation in ICU.Proportion of patients from each group achieving targeted sedation score at 12 and 24 hours following initiation of the drug and proportion of patients from each group requiring rescue sedation dose will be recorded and analyzed.

Furthemore duration of mechanical ventilation, length of ICU stay and 14 days mortality rate will recorded and compared between this 2 groups of patients.

Inclusion Criteria:

• Age >18 years old
• Patients who are expected by the ICU team to require invasive mechanical ventilation in ICU for at least more than 24 hours and for whom the ICU team decides to initiate continuous infusion of sedation
• A patient who was ventilated and sedated not more than 12 hours before ICU admission.

Exclusion Criteria:

• Patients with chronic use of narcotics
• Patients with chronic liver failure or end-stage renal failure
• Patients with severe chronic neurocognitive dysfunction
• Patients with drug overdose
• Patients with a known allergy to either morphine or fentanyl
• Patients who are receiving neuromuscular blockers
• Patients who are pregnant
• Patients who are diagnosed to have severe traumatic brain in