Pathophysiology, assessment, and treatment of chronic cancer pain in critically ill patients

Pain is a common and distressing symptom in cancer patients, with prevalence as high as 69% in those with advanced cancer. The pathophysiologic mechanisms of cancer pain are complex and change with progression and/or cure of the disease with several pain syndromes unique to cancer survivors. Evidence over the past decade has revealed suboptimal evaluation and treatment of pain in critically ill patients in the intensive care unit (ICU). The experience of pain is a subjective phenomenon, and assessment of pain in the critically ill cancer patients can pose multiple challenges. Despite the considerable increase in the therapeutic use of opioids, there is limited evidence-based data pertaining to the optimal management of chronic cancer pain in the critical care setting. Treatment involves continuation of chronic opioid therapy as indicated and use of adjuvants and interventional therapies based on the pathophysiology of the pain syndrome. This chapter elaborates on the pathophysiology of chronic cancer pain, assessment in the ICU setting, and available treatment modalities.