Recent advances in postoperative pain therapy

Abstract

Despite many advances in the provision of pain services, acute pain after surgery remains a serious cause of severe suffering that is often undermanaged despite our best efforts.⁶³⁴³⁷ Acute pain teams have been introduced in many hospitals, but recent evidence from a UK national postal questionnaire suggests that they are struggling with the problem of alleviating acute pain successfully.⁹⁰ In a review of published data of pooled pain scores from nearly 20 000 surgical patients having intramuscular, patient controlled analgesia (PCA) or extradural analgesia, the overall mean (95% confidence interval) incidence of moderate to severe and severe pain was 29.7 (26.4–33.0)% and 10.9 (8.4–13.4)%, respectively.³⁷ Often the provision of effective postoperative analgesia is limited by side-effects, and these have been quantified in contemporary anaesthetic practice by Cashman and Dolin with special attention to respiratory depression and hypotension after intramuscular, PCA and extradural analgesia,²⁸ in a companion paper to their study of analgesic efficacy.³⁷ Cashman and Dolin concluded that assuming an acute pain service uses a mixture of the three analgesic techniques studied (intramuscular, PCA, and extradural analgesia), then the expected incidence of respiratory depression (defined by a low ventilatory frequency) should be less than 1%, and the expected incidence of hypotension related to analgesic technique should be less than 5%. Interestingly, while the incidence of respiratory depression decreased over the period 1980–99, the incidence of hypotension did not.²⁸ The risk of side-effects from other analgesics in use for acute postoperative pain therapy is well defined. NSAIDs, for example, are effective analgesics, but have potential adverse effects that may render them contraindicated in many patients having surgery.⁴⁷⁷⁶