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.