Background: This study arose from the need to improve alt tasks related to monitoring pain in post cardiac surgery patients. Objectives: Checking and quantifying the pain suffered by patients undergoing cardiac surgery in the first 24 hours of their stay in the intensive care unit (ICU), treated with Dexmedetomidine (Dex) as analgesic adjuvant, as well as their degree of sedation and the need for opiates such as rescue analgesia. Material and methods: Unicentric study, observational, descriptive, from April 2016 to September 2017. Both genders, all adult, undergoing cardiac surgery, operating theatre-extubated and Dex continuous infusion carriers. Pain degree level was evaluated by the Visual analogue Scale of Pain (VAS), from immediately post-surgery until 24 hours from ICU entry and sedation degree, by the Richmond Sedation Agitation Scale (RASS), only while the Dex infusion lasted. Results: 109 patients were included. The results obtained showed that the average pain suffered by patients during the first 24 hours was .47 with standard deviation (SD) of 1.25; the average maximum pain experienced was 3.58 with a range of 0 to 8 and the RASS average was -.68 (SD: 0,80). In addition, 44.04% of the patients needed rescue opiates, although only 7.32% showed severe pain greater than 6. Conclusions: The Dex infusion patients showed mild levels of pain, however, a small percentage, who must be taken into account, suffered severe pain. (C) 2019 Sociedad Espanola de Enfermeria Intensiva y Unidades Coronarias (SEEIUC). Published by Elsevier Espana, S.L.U. All rights reserved.