A major problem in some parts of the world is that certain drugs, such as morphine, which are the mainstay of postoperative pain relief in many places, are not available. In addition, economic factors may mean that techniques of pain relief such as patient-controlled analgesia (P.C.A.) are unavailable and that techniques of regional anaesthesia which employ continuous infusions through disposable catheters are impossible. It is no use advocating techniques such as these if they are beyond local resources. It is better to maximise the effective use of local anaesthetic techniques and intermittent delivery of such analgesic drugs as are available. This review will discuss the use of the more advanced techniques in broad terms with the hope that the availability of both drugs and equipment can be improved in the longer term.

In general, the introduction of new and potentially expensive techniques is resisted by administration and professions alike. However, the introduction of such techniques may yield increased benefits in the form of improved recovery and faster discharge from hospital with consequent reductions in the cost of health care. Effective postoperative pain management may be encouraged by education of politicians, administrators, professional colleagues and patients.

Assessment of pain is in two parts; before the operation to make a pain management plan and afterwards to see whether the plan is working. The preoperative assessment includes the factors mentioned previously, as well as variables such as age, sex, weight, degree of obesity, current drug intake or past history of drug-related problems. Potential difficulties caused by language or culture are also assessed. There may be problems related to age, and relief of pain in children and the elderly are considered under separate headings.

There is some evidence to suggest that the use of opioid premedication establishes a level of analgesic control from the outset. There is however no evidence to support the use of local anaesthetic blocks or peripherally acting drugs in this pre-emptive fashion.

Rating scales are the most commonly used method of assessing acute pain and its relief. In practice, these are either words or numbers. In addition, a numerical value can be derived from a visual analogue scale. All these methods are simple, can be readily understood and require little in the way of technology or resources.

Words can be translated into any language and a simple five point scale is normally used. An example is shown below.

Numbers can be assigned to each of the words for recording purposes (0-4). A simple numerical rating scale would require the patient to choose a number between 0 and 10 to represent their pain. Zero indicates that the patient has no pain and 10 means that the pain is as bad as can be imagined.

Visual analogue scales have a 10cm line which is marked as shown below. The patient is asked to make a vertical mark on the line to indicate the intensity of their pain.

There should be no other markings, numbers or words along the line as this tends to influence the results. It is most important to ensure that the patient understands the two end points. A small percentage of patients including the elderly and those with limited education have difficulty with visual analogue scales. Most can be trained by giving examples of familiar pain problems and relating these to positions along the line. If pain is being assessed regularly, then at the time of assessment the patient should not be able to see any other score as this may affect his decision. A visual analogue can be scored by measuring from the left side how far the patient marked towards the maximum pain end. This number can then be used to compare changes in the pain level.

Assessment of pain in infants or patients who cannot communicate can be difficult. Pain can be assessed with picture scales using varied facial expressions or by clinical observation (for example: sighing, groaning, sweating, ability to move). The latter method has the advantage that it does not rely on the patient to any great degree and can be carried out when other vital signs such as heart rate and blood pressure are being assessed. Asking the patient to take a deep breath or to cough or move will also provide useful information and it is important to emphasise that measurement of pain while the patient is at rest is unlikely to indicate the need for analgesia. Pain relief should be assessed when the patient is active.

Simple questions like "where does it hurt? " and "what does it feel like?" may allow a qualitative evaluation of pain after surgery. Pain distant from the operative site may indicate complications not associated with the procedure which may require separate treatment. Complaints of generalised pain all over the body may represent stress, anxiety, or in some cases fever. The description of the pain may indicate the cause. For example sharp, stabbing pain is associated with surgery, whereas numbness or tingling may mean nerve compression or ischaemia. Unusual or vague descriptions are more likely to be due to non-organic causes.

It may be difficult to assess pain in the early post-operative period by any of the methods described. It should be stressed that the assessment must be made at regular intervals and should form part of the routine postoperative observations. The progress of the patient is more easily assessed if results are charted in graphical form rather than as a number. Nursing, auxiliary and trainee medical staff should be encouraged to use assessment of pain routinely. Furthermore, they should be given training in the use of all forms of analgesic technique so they become confident in their use. Experience suggests that frequent assessment and delivery of analgesia whenever needed become a routine once the benefit to the patient is recognised.

 
Pharmacology

The World Health Organisation Analgesic Ladder was introduced to improve pain control in patients with cancer pain. However, it has lessons for the management of acute pain as it employs a logical strategy to pain management. As originally described, the ladder has three rungs.

In the first instance peripherally acting drugs such as aspirin, paracetamol or non-steroidal anti-inflammatory drugs (NSAIDs) are given. If pain control is not achieved, the second part of the ladder is to introduce weak opioid drugs such as codeine or dextropropoxyphene together with appropriate agents to control and minimise side effects. If effective control is not achieved by this change, the final rung of the ladder is to introduce strong opioid drugs such as morphine. Analgesia from peripherally acting drugs may be additive to that from centrally-acting opioids and thus, the two are given together.

The World Federation of Societies of Anaesthesiologists (WFSA) Analgesic Ladder has been developed to treat acute pain. Initially, the pain can be expected to be severe and may need controlling with strong analgesics in combination with local anaesthetic blocks and peripherally acting drugs.

The oral route for the administration of drugs may be denied because of the nature of the surgery and drugs may have to be given by injection. Normally, postoperative pain should decrease with time and the need for drugs to be given by injection should cease. The second rung on the postoperative pain ladder is the restoration of the use of the oral route to deliver analgesia. Strong opioids may no longer be required and adequate analgesia can be obtained by using combinations of peripherally acting agents and weak opioids. The final step is when the pain can be controlled by peripherally acting agents alone.

(Continued...)

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