The influence of age upon opioid analgesic use in the patient-controlled analgesia (PCA) environment

It is often asserted that older patients are more sensitive to opioid analgesics than younger patients but experimental evidence for this assertion remains sparse. Two studies were conducted investigating the relationship between age and opioid analgesic use in the patient-controlled analgesia environment. In study I, the relationship was analysed subsequent to our publication of a study investigating patients' responses to opioid use with patient-controlled analgesia. Fifty-five postoperative patients, stratified into 'older' and 'younger' patients by median age, received morphine or pethidine or fentanyl patient-controlled analgesia. A strong inverse relationship was found between age and fentanyl and morphine use but not between age and pethidine use. Study II was a retrospective study of the medical records of 199 patient-controlled analgesia patients who had received morphine or pethidine patient-controlled analgesia; there were insufficient patients who had used fentanyl for a reasonable sample. There was a difference in morphine use with the younger patients using significantly more morphine than the older patients (> 60 years). Findings were less clear for patients receiving pethidine but there was an inverse correlation between age and pethidine use as well. Overall, the findings of these two studies supported the common clinical belief that older patients require less opioids than younger patients.