Perioperative pain relief
Acute Pain Management
Optimal management of acute postoperative pain requires planning, patient and staff education, and tailoring to the type of surgery and the needs of the individual patient. Patients vary greatly (up to eight-fold) in their requirement for analgesia, even after identical surgical procedures. Under-treatment results in unacceptable levels of pain with tachycardia, hypertension, vasoconstriction and ‘splinting’ of the affected part. Painful abdominal and thoracic wounds restrict inspiration, leading to tachypnoea, small tidal volumes, and inhibition of the patient from effective coughing and mobilisation. This predisposes to chest infection, delayed mobilisation, deep venous thrombosis, muscle wasting and pressure sores.
However, analgesic administration above the patient’s requirement increases the risks of side effects such as nausea, vomiting, somnolence and dizziness or, if greatly in excess, severe central effects including depressed consciousness and
respiration. This is fortunately rare, and can be avoided by sensible initial dosing followed by titration until the patient is comfortable. Exaggerated fears of opioid induced central depression and addiction have led all too commonly to inhibition amongst staff from prescribing and administering adequate doses of opioids. Intermittent intramuscular dosing also leads to delays in administration of the ‘controlled’ opioids compounded by the time to onset of action of action.
As a result of these common deficiencies, a Joint Working Party of the Royal Colleges of Anaesthetists and Surgeons was convened, which published the report Pain after Surgery in 1990. It recommended the establishment of acute pain teams, comprising medical and nursing specialists, to oversee the implementation of guidelines for practice including routine recording of pain levels, and educating both staff and patients. Combinations of analgesic methods [local anaesthesia and nonsteroidal anti-inflammatory drugs (NSAIDs) with opioid drugs] were advocated, as were the more sophisticated methods of pain management such as ‘patient-controlled analgesia’.
The Working Party report also encouraged further use of combined treatments (termed balanced analgesia) such as with:
• local anaesthetic blocks — excellent short-term analgesia, but requires skill and has a small failure rate. Continuous catheter techniques prolong pain relief but are only appropriate for inpatients;
• spinal opioids — generally very useful for appropriate types of surgery, but again requires skill, and is limited by concerns over severe respiratory depression;
• NSAIDs — in combination reduce requirement for opioids and alone are useful for moderate pain, but are limited by concerns over side effects, such as renal impairment, peptic ulceration and inducing acute bronchospasm in asthmatics. They are not adequate as sole analgesic therapy after major surgery.
The report called for further research and, amongst other aims, hoped for the advent of a powerful analgesic on a par with morphine, but without marked respiratory depressant activity. While the development of tailor-made opioid agonists with differential receptor activity has not yet solved this problem, attention turned more to finding alternative pathways at which to attenuate the afferent pain impulses. For example, clonidine has been administered epidurally to stimulate the spinal cord adrenergic inhibitory mechanisms.
Severe acute pain increases morbidity after trauma or surgery.
Appreciation of pain pathways and the three main classes of pain — nociceptive, neuropathic/sympathetic and that of mainly psychological origin — together with enhanced awareness of pain, has led to new and multimodal treatment strategies.
The methods of prevention are:
• adequate analgesia by intravenous narcotic drugs at the time of surgery;
• regional anaesthesia alone or supplementing general anaesthesia during surgery to prevent excitation of central pathways;
• the use of prostaglandin inhibitory drugs during surgery. Diclofenac suppositories are effective in reducing the pain from tissue damage in bone and muscle, and are used at the time of operation.
These three approaches used together are good at preventing the cycle of pain and muscle spasm from becoming established in the recovery period.
The same methods can be used for managing the pain of acute trauma.
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