Persistent inflammation, immunosuppression, and catabolism syndrome (PICS): a review of definitions, potential therapies, and research priorities

Summary

This narrative review examines Persistent Inflammation, Immunosuppression, and Catabolism Syndrome (PICS), a recognised clinical endotype of chronic critical illness characterised by ongoing organ dysfunction, sarcopenia, recurrent infection, and metabolic derangement. The authors survey potential therapeutic avenues—including drugs to restore immune homeostasis, modify myeloid-derived suppressor cells, reduce persistent inflammation, and limit catabolism, alongside nutritional strategies such as ketogenic feeding and probiotics—whilst acknowledging substantial heterogeneity in PICS definitions and the likely need for consensus diagnostic criteria and multimodal, personalised treatment strategies.

UK applicability

The clinical management challenges described in PICS are pertinent to UK critical care settings and NHS intensive care practice. However, the review focuses on clinical immunology and pharmacotherapy rather than nutritional or agricultural interventions, so direct application to food systems or farming policy is limited unless UK nutrition guidance for critical illness is revised to incorporate the proposed nutritional support strategies (ketogenic feeding, probiotics).

Key measures

Definitions and diagnostic criteria for PICS; proposed therapeutic mechanisms and candidate interventions (immunostimulatory agents, MDSC modulators, anti-inflammatory drugs, antioxidants, anti-catabolic agents, nutritional support); identification of research priorities and endotypes of chronic critical illness.

Outcomes reported

The review synthesises definitions, pathophysiological mechanisms, and potential therapeutic approaches for PICS, a clinical endotype characterised by a self-perpetuating cycle of organ dysfunction, inflammation, catabolism, and immunosuppression. It identifies candidate drugs and nutritional strategies that may address specific pathophysiological features, though notes the absence of licensed treatments and the need for personalised, multimodal approaches.

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