Acute pain management for the preregistration house officer

Don't switch off if you are not at this stage yet. Medical students often spend the most time with patients so may be the first to know if a patient is suffering from pain. Oliver Jones summarises how you should manage a patient who is in acute pain

One of the common scenarios facing a newly qualified doctor is the call to the ward or to an accident and emergency department because a patient is in pain. Although every medical student can name a great range of analgesics, approaching the problem in a rational way can be quite daunting. This article provides a background to the management of pain, which is an issue of great concern to the patient but often relatively neglected by medical staff.

Before you write on the chart

Although a prescription for an analgesic may seem like the inevitable outcome of the consultation, a history and examination must be the starting point. This allows you to gauge the level of pain and the effectiveness of measures already taken. Analgesic drugs relieve pain of any cause. However, it is better to treat some painful syndromes with other specific drugs which are not strictly analgesics (see table).

If you still decide that an analgesic should be prescribed the choice is between non-narcotic and narcotic analgesia. Non-narcotic analgesics (such as aspirin) act predominantly peripherally and do not cause drowsiness, while the narcotic drugs (such as opioids) have a central action and often cause drowsiness. It is worth noting that the mechanism of some widely used drugs, such as paracetamol, is not fully understood. It is useful to consider analgesics in three different categories.

Non-narcotic analgesia for mild pain--for example, aspirin, paracetamol, and ibuprofen

The non-steroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen, are particularly effective when used for pain that has an inflammatory component, such as muscle strains or bony pain. For an anti-inflammatory action, these drugs usually need to be used at a higher dose than would be needed for analgesia alone. Aspirin should not be given to children under the age of 12, as it is associated with Reye's syndrome.

Low efficacy narcotic analgesics--for example, codeine, dihydrocodeine--or combined analgesics--for example, coproxamol--for moderate pain

The combination analgesics such as coproxamol, which is the mild opioid dextropropoxyphene combined with paracetamol, are widely used in the community (and hospitals). While convenient, they have the
theoretical disadvantage of most combination drugs, in that they may have inadequate dosing of one or other component.

High efficacy narcotic analgesics for severe pain--for example, morphine, pethidine

These drugs are very effective for visceral pain, and they may usefully be combined with a NSAID, when there is significant tissue injury. Morphine is the most generally used high efficacy narcotic. It is usually given by the intramuscular (IM) or subcutaneous (SC) route. 10 mg is usually given, with the dose being repeated every three hours if necessary (the half life of morphine is around two hours).

Morphine's side effects include nausea and vomiting, and so an antiemetic should be coadministered. It can also cause respiratory depression so should be used with caution in patients after an operation and in those with respiratory disease. Further side effects are suppression of the cough reflex and constipation. Morphine can be reversed by naloxone, 100-200 µg given intravenously. Naloxone has a shorter half life than morphine and so this dose may need to be repeated.

Where to start

Very quickly, you will become better at assessing patients' pain level as mild, moderate, or severe. This will guide you as to what drug you should start with. You should not attempt to learn the names and doses of every analgesic as most doctors regularly use only eight or nine drugs across the above categories.

Failure to control pain

If your prescription has not helped, check that the patient's clinical condition is not deteriorating and check the patient's drug chart. The fact that a drug is written on the chart does not mean that the patient has been receiving it. If you have written it on the "as required" side the patient may not have asked for it or the nurses may not have been giving it. Furthermore, the patient may not have been receiving the maximum dose. A useful practical way of getting round this problem is to write the prescription on the regular side of the chart so that the patient does not have to ask for the drug and the nurses will give it on their regular drug rounds.

Local practices vary, but in many hospitals patient controlled analgesia (PCA) is another option, especially for patients after an operation. This commonly involves narcotics, such as pethidine or morphine, given by the intravenous or subcutaneous route. A bolus of the drug is automatically given when the patient presses a hand held button. Your prescription of a PCA must specify the amount of drug in each bolus and the "lockout time." This is the time period that must elapse between successive demands and acts as a safety net to prevent patients from inadvertently overdosing themselves. A steady background infusion of the drug can also be incorporated. The ward sister or hospital pharmacist will be able to advise you on the commonly used practices in your hospital.

If this still fails to control pain then move up a category on analgesic strength. If you are not getting on top of the pain or you are using high efficacy opioids at reasonable doses then you should ask for help. Ask someone senior on the team or a member of the pain team, if your hospital has one. Many anaesthetists are also interested in the management of pain, and all should be if you are dealing with a patient who has had an operation.

For more information on the postoperative management of pain, refer to "Anaesthesia explained" in the March issue of the studentBMJ. (www.studentbmj.com/issues/01/03/education/52.php)

Oliver Jones, research fellow, department of pharmacology, University of Oxford


studentBMJ 2001;09:399-442 November ISSN 0966-6494