Are vital signs valid indicators for the assessment of pain in postoperative cardiac surgery ICU adults?

The aim of this study was to examine the discriminant and criterion validity of vital signs (mean arterial pressure [MAP], heart rate [HR], respiratory rate [HR], transcutaneous oxygen saturation [SpO2], and end-tidal CO2) for pain assessment in postoperative cardiac surgery ICU adults. A repeated-measure within-subject design was used. A convenience sample of 105 patients from a cardiology health center in Canada participated. Patients were observed during three testing periods: (1) unconscious and mechanically ventilated, (2) conscious and mechanically ventilated and (3) after extubation. For each of these testing periods, vital signs were assessed using the ICU monitoring at rest, during a nociceptice procedure and 20min postprocedure. Conscious patients’ self-reports of pain were obtained. Discriminant validity was supported with significant changes in most vital signs during the nociceptive procedure. Some of the vital signs (HR, RR, and SpO2) were associated with the patients’ self-reports of pain but were dependent on the patients’ status (mechanically ventilated or not). Findings regarding the use of vital signs for pain assessment are not consistent and should be considered with caution. As recommended by experts, vital signs should only be used as a cue when behavioural indicators are no longer available in mechanically ventilated or unconscious patients.