Nociception and pain assessment during suctioning procedures in mechanically ventilated patients in the intensive care unit: A validation study of the Nociception Level index (NOL™).

Background: Many patients in the intensive care unit (ICU) cannot communicate pain through self-reports or behaviors. Though individual physiologic parameters (e.g. heart rate, HR) lack validity for ICU nociception and pain assessment, a multiparameter approach (i.e. Nociception Level index, NOL) has shown promise in anesthesia, but its use in the ICU is new.

Aim: The aim of this study was to validate the NOL for ICU nociception and pain assessment in mechanically ventilated patients.

Methods: In this prospective observational study, NOL values (0-100) were recorded before, during, and 15 min after a nonnociceptive procedure (blood pressure cuff inflation) and a nociceptive procedure (mouth, endotracheal, or tracheal suctioning) in patients able or not to self-report. Validation included discriminative (nociceptive vs. nonnociceptive procedures), criterion (pain intensity and Critical Care Pain Observation Tool, CPOT) and convergent (procedural pain distress) strategies, and test-retest reliability. HR validity was also examined.

Results: Of 53 enrolled patients, we had 14 losses (9 NOL-related), thus data from 39 were analyzed. Missing data occurred in 25% of patients at some time points. NOL median values were significantly higher during suctioning (>25) than cuff inflation (<10) and remained stable pre/postsuctioning. Positive correlations were found for pain intensity and CPOT but not for procedural pain distress. HR increased slightly during suctioning but was not correlated with pain criteria.

Conclusions: The discriminative validity of the NOL was supported for ICU nociception in all patients and showed stable resting values. Criterion validity for pain assessment was only significant in patients able to self-report. Convergent validity was not supported. HR showed poor validity.