Introduction: Pain is a subjective symptom, a physiological response that is difficult to assess, which affects the body physically and/or emotionally. It is a common phenomenon among clinical and surgical patients in Intensive Care Units (ICU). And its effects are the combined results of physiological and behavioral aggressions caused by clinical conditions, immobility and the execution of common procedures in ICU's. The presence of pain appears to be independently associated with worse clinical outcomes, including higher infection rates, patient-ventilator asynchronies, delirium, prolonged mechanical ventilation (MV), length of hospital stay and higher healthcare costs.

Objectives: To evaluate the prevalence of pain and its associated factors in mechanically ventilated surgical patients in ICU's.

Methods: This is a cohort, prospective, multicenter study designed to estimate the prevalence of pain, its intensity, its associated factors, correlating them to outcomes such as patient-ventilator asynchrony rate, time to weaning, and 28-day mortality in mechanically ventilated patients. All research participants who meet the inclusion criteria and who are not using neuromuscular blockers, or have any other condition associated with altered pain perception, will be evaluated using the Behavioral Pain Scale (BPS) and the Critical Care Pain Observation Tool (CPOT) on the 2nd day of mechanical ventilation and on the first day of awakening, when the RASS scale is between 4 and -2. At the same time, data will be collected on the ongoing sedoanalegesia strategy, and the asynchrony index will be calculated \[(Nº of asynchronous ventilatory cycles/Nº of ventilatory cycles studied) \*100\]. The end point of the research will be 28 days, where the time until weaning, time until discharge or death will be established using the Kaplan-Meier estimators. Expected results: The prevalence of pain and its intensity is associated with the presence of patient-ventilator asynchronies and thus with harsh outcomes related to the length of stay in the ICU, time until weaning and thirty-day mortality in the ICU. It is estimated that there is agreement between the BPS and CPOT scales in mechanically ventilated patients.