Assessment of pain in sedated and mechanically ventilated patients: an observational study

Background: Critically ill patients often undergo unpleasant procedures. We quantified the effects of an unpleasant stimulus on physiological and behavioral parameters and evaluated how they are modified by sedation and analgesia. Methods: A 6-month study in the 30-bed intensive care unit (ICU) of a university hospital examined 21 sedated patients from various diagnostic groups. Hemodynamic and respiratory parameters, pupil size, facial expression, muscle tone, body movement, and the Richmond Agitation-Sedation Scale (RASS) score were measured before and during intratracheal suctioning, first in sedated patients, after sedation was stopped, and after an opioid bolus. Results: Before intratracheal suctioning, patients had RASS scores of -1.8 +/- 1.2 (mean +/- standard deviation; sedation), -0.6 +/- 1.7 (sedation stop), and -0.9 +/- 1.4 (analgesia) (P = 0.014). Intratracheal suctioning significantly increased RASS during both sedation (to -0.6 +/- 1.7) and sedation stop (to 1.0 +/- 1.5) (both P <0.01), but not during analgesia. Systolic blood pressure increased during sedation (by 9 +/- 10 mmHg), during sedation stop (by 15 +/- 17 mmHg) and during analgesia (by 9 +/- 4 mmHg; all P <0.01), but diastolic pressure only during sedation and sedation stop (both P <0.01). Facial expression, body movement, and muscle tone changed significantly during the episodes of intratracheal suctioning. Heart rate, tidal volume, and pupil size remained stable under all conditions. Conclusions: Intratracheal suctioning evoked significant changes in some physiological and behavioral parameters. Some physiological changes were suppressed by analgesia, but at our ICU's standard doses, neither analgesia nor sedation attenuated changes in behavioral parameters at the intensity tested.