Association between lymphocyte expression of the apoptotic receptor Fas and pain in critically ill patients

Abstract

Elizabeth DE Papathanassoglou,1,* Meropi DA Mpouzika,2,* Margarita Giannakopoulou,3 Evangelos Bozas,3 Nicos Middleton,2 George Tsiaousis,2 Andreas Karabinis4,5 1Faculty of Nursing, University of Alberta, Edmonton, AB, Canada; 2Department of Nursing, Cyprus University of Technology, Limassol, Cyprus; 3Department of Nursing, School of Health Sciences, National and Kapodistrian University of Athens, 4Surgical Care Unit, The Onassis Cardiac Surgery Center, Kallithea, 5School of Medicine, National and Kapodistrian University of Athens, Athens, Greece *These authors contributed equally to this work Objective: Lymphocyte apoptosis in critical illness is associated with immunosuppression. We explored for the first time the associations between pain ratings and expression of the apoptotic receptor Fas on B and T cells in critically ill patients and the potential mediating effects of adrenocorticotropic hormone (ACTH), cortisol, and substance P (SP).Design: This is an exploratory correlational study with repeated measurements (14 days follow-up) and cross-sectional comparisons.Setting: This study was conducted in a state hospital in the metropolitan area of Athens, Greece.Participants: The participants were 36 consecutive critically ill patients and 36 matched controls.Outcome measures: Pain measured by the self-reported numeric rating scale [NRS], the behavioral pain scale, and the pain assessment scale was the primary outcome measure. Flow cytometry (Fas), electrochemiluminescence (ACTH and cortisol) and enzyme-linked immunosorbent assay (SP) were used. Mixed linear models for repeated measurements and bivariable associations at discrete time points were employed.Results: Significant pain at rest was noted. Pain ratings associated with Fas expression on cytotoxic T cells (P=0.041) and B cells (P=0.005), even after adjustment for a number of clinical treatment factors (P=0.006 and P=0.052, respectively). On the day that more patients were able to communicate, Fas on B cells (r=0.897, P=0.029) and cytotoxic T cells (r=0.832; P=0.037) associated with NRS ratings. Associations between pain ratings and ACTH serum levels were noted (P<0.05). When stress neuropeptide levels were added to the model, the statistical significance of the associations between pain ratings and Fas expression was attenuated (P=0.052–0.063), suggesting that stress neuropeptides may partially mediate the association.Conclusion: Preliminary evidence for the association between pain and lymphocyte apoptotic susceptibility is provided. The role of pain management in maintaining immunocompetence in critical illness is worth exploring. Keywords: lymphocyte apoptosis, pain, critical illness, adrenocorticotropic hormone, cortisol, substance P

Keywords

• Lymphocyte apoptosis
• pain
• critical illness
• adrenocorticotropic hormone
• cortisol
• substance P