Pain management

Abstract

Unrelieved post-operative pain has a number of adverse physiological effects that can impair post-operative recovery and convalescence. In patients with pre-operatively reduced organ functional reserves, such pain-induced changes may increase post-operative morbidity, and even mortality in high-risk patients. Freedom from severe pain in the immediate post-anaesthetic phase makes overall management of pain in the entire post-operative period more feasible. This will reduce unnecessary suffering, anxiety, sleep deprivation and emotional fatigue; optimal pain management may also improve cardio-respiratory functions, gastrointestinal and metabolic functions, and reduce changes in pain modulating mechanisms that cause persistent post-operative neuropathic pain. Optimal post-operative pain management is a prerequisite for early mobilization and a vigorous post-operative rehabilitation programme. The concept of ‘pre-emptive’ analgesia is still valid in that pain receiving and modulating neurones in the central nervous system will become sensitized by ongoing C-fibre nociceptive input from traumatized tissues. It is, however, not possible to prevent this sensitization by pre-treatment alone; rather it is necessary to have ongoing pain treatment as long as there is nociceptive input during the peri- and post-operative period. Anaesthesiologists have a unique opportunity to give surgical patients a flying start with post-operative pain relief by always employing analgesia-based peri- and post-anaesthetic management. A well-balanced multi-component pain relief regimen with peripheral, regional, or central neural blockade during and after surgery whenever appropriate and feasible, combined with a non-opioid and opioid analgesics should be applied. Of the non-opioid analgesics, paracetamol rectally or the prodrug propacetamol intravenously, is the safest drug in this group. It does not interfere with haemostatic mechanisms or thromboprophylactic regimens, is not ulcerogenic, and does not influence kidney function in hypovolaemic patients. The more potent NSAIDs, such as ketorolac, diclofenac, indomethacin, which also can be administered parenterally, naproxen, ketoprofen, ibuprofen, or piroxicam, all may give better pain relief than paracetamol, and they are largely safe for short-term use. However, I do worry about the potentially very serious adverse effects of some of these drugs. Glucocorticoids administered parenterally are potent analgesics and probably deserve wider use in post-operative pain management. Their adverse effects appear not to be frequent. they may have additional beneficial effects on post-operative fatigue. Whether epidural administration is more effective than parenteral administration, and whether the added risk is justifiable, remains an open question. Opioid analgesics are still the mainstay for routine post-operative pain relief. Patient-controlled opioid analgesia (PCA) is an extremely popular method with a large majority of patients who get the opportunity to use this method. However, in the immediate post-anaesthetic period, PCA is sometimes difficult to apply because of interactions with general anaesthetic drug ‘hangover’ effects such as sedation, confusion and nausea. Safe, low-dose epidural opioid administration is optimally exploited only if it is combined with a low concentration local anaesthetic. The local anaesthetic causes most of the specific beneficial effects of optimal epidural analgesia. These include improved cardiorespiratory, circulatory-haemostatic gastrointestinal, endocrine-metabolic functions. The specific spinal analgesic effect of opioid-plus-local anaesthetic can be further improved by adding an adrenergic component such as adrenaline. This low-dose epidural analgesic mixture (fentanyl-bupivacaine-adrenaline) gives excellent analgesia after major surgery, almost free of adverse effects, only if the epidural catheter is placed in a segmentally correct position: the analgesic mixture acts on opioid and adrenergic receptors and other synaptic transmission-inhibiting mechanisms of the spinal cord, not on the nerve roots. This means that the epidural catheter always will have to be above lumbar level L1–2 even for abdominoperineal or lower extremity surgery. Patient-controlled analgesia and epidural analgesia is best started in the post-anaesthesia care unit, but they can and must be implemented on surgical wards so that the patients benefit from these excellent techniques throughout the painful part of the post-operative course. This requires a major teaching and motivating programme for all nurses, surgeons and anaesthesiologists involved. Experience with implementing hospital-wide post-operative pain management programmes in two university hospitals have convinced me that this is possible only if sufficient personnel resources are available for this important task. Moreover, to ensure continuous safe post-operative pain management for most surgical patients, an ongoing programme for teaching, monitoring, quality control and quality-improvement is mandatory. This does require capital and personnel resources, but must give an overall very positive cost-benefit result for the health care system, with a more comfortable and shorter post-operative course and more satisfied patients.