Sensory phenotypes of chronic pain in critically ill patients: a prospective observational study

INTRODUCTION: Determining sensory phenotypes that reflect underlying pain mechanisms may be relevant for critically ill patients with chronic pain. OBJECTIVE: To evaluate the intensity, localization and sensory phenotypes of chronic pain in critically ill patients. MATERIALS AND METHODS: The study included 99 critically ill patients. Inclusion criteria: age 18–75 years, length of stay in the ICU > 3 days, duration of mechanical ventilation > 48 hours, APACHE II score ≥ 7 points, obtaining informed consent. Localization, intensity, and qualitative characteristics of long-term (at least 6 months) pain associated with ICU stay were assessed using the Brief Pain Inventory and the PainDetect Questionnaire, and the severity of anxiety and depression on the HADS scale. Before discharge, all patients underwent thermal quantitative sensory testing (CST) with assessment of cold detection thresholds and warm detection thresholds, paradoxical thermal sensations, cold pain thresholds and heat pain thresholds, conditioned pain modulation. RESULTS: After 6 months chronic pain syndrome developed in 59 % of patients. Data were obtained on the intensity, localization, and severity of the neuropathic and dysfunctional components of pain. When assessing the thermal parameters of QST, a statistically significant difference in the distribution of values for the thresholds of sensitivity to cold and heat was obtained between the group of patients with chronic pain and the group without pain (p < 0.0001) Hierarchical cluster analysis revealed a statistically significant relationship between changes in static and dynamic parameters of thermal sensory testing, the formation of an “irritated” and “deafferent” sensory phenotype depending on the duration of mechanical ventilation, stay in the ICU and assessment on the SOFA scale. CONCLUSIONS: sensory phenotypes make it possible to identify patients with dysfunction of small diameter fibers, impaired endogenous pain control mechanisms, which will allow selecting an individual program to pain relief.