Continuous subcutaneous infusion for pain control in dying patients: experiences from a tertiary palliative care center

BACKGROUND: Continuous subcutaneous infusion (CSCI) via ambulatory infusion pump (AIP) is a valuable method of pain control in palliative care. When using CSCI, low-dose methadone as add-on to other opioids might be an option in complex pain situations. This study aimed to investigate the effects, and adverse effects, of CSCI for pain control in dying patients, with particular interest in methadone use. METHODS: This was an observational cohort study. Imminently dying patients with pain, admitted to specialized palliative inpatient wards and introduced on CSCI, were monitored daily by staff for symptoms (Integrated Palliative Care Outcome Scale - IPOS), sedation (Richmond Agitation and Sedation Scale – RASS), performance status (Eastern Cooperative Oncology Group - ECOG) and delirium (Confusion Assessment Method - CAM). RESULTS: Ninety-three patients with a median survival of 4 days were included. Of the 47 patients who survived ≥3 days, the proportion of patients with severe/overwhelming pain decreased from 45 to 19% (p < 0.001) after starting CSCI, with only a moderate increase in morphine equivalent daily dose of opioids (MEDD). Alertness was marginally decreased (1 point on the 10-point RASS scale, p = 0.001), whereas performance status and prevalence of delirium, regardless of age, remained unchanged. Both patients with methadone as add-on (MET, n = 13) and patients with only other opioids (NMET, n = 34), improved in pain control (p < 0.05 and 0.001, respectively), despite that MET patients had higher pain scores at baseline (p < 0.05) and were on a higher MEDD (240 mg vs.133 mg). No serious adverse effects demanding treatment stop were reported. CONCLUSIONS: CSCI via AIP is an effective way to reduce pain in dying patients without increased adverse effects. Add-on methadone may be beneficial in patients with severe complex pain.