Pain Centre

05 December 2008

Traditional way of post-operative pain relief: Injections of morphine or another opioid

The "traditional" way of postoperative pain relief involves injections of morphine or another opioid.

Pain relief only when the patient requests it:
When a patient has pain and requests a strong pain killer, the nursing staff injects an intramuscular opioid (morphine, pethidine, omnopon, etc.). The injected drug is taken up from the muscle into the bloodstream, travels to the brain, and there exerts its pain killing effect.

There are a few disadvantages of this method:

  • Patients always wait a while, sometimes an hour or more, before they actually ask for painkillers. There are many reasons for this: the staff always looks so busy and they are too embarrassed to disturb them, they do not want to be seen as weak and complaining, the surgeon told them it was not going to be painful (surgeons often do that). By then the pain has often become very severe. When the nursing staff responds, it takes on the average 30 – 40 minutes before the painkiller is actually administered, and there after another 10 – 15 minutes before the painkiller works. All this together leaves the patient in pain for two hours, not an ideal situation.

  • The amount administered is often not sufficient, especially if the pain has become severe. Most opioids are given too little, too late.

  • It involves an injection each time, which in itself is painful.

Only 30 – 40 % of patients find this method of pain relief satisfactory.

Pain relief at regular intervals:
A better way is to inject the opioids at regular intervals, e.g. every four hours, and not only on the patient’s request. This will provide better continuous pain relief, but sometimes not enough, like during painful physiotherapy sessions, or sometimes too much, like at night (sleep reduces the requirements for painkillers by 50%).

This method is satisfactory to more patients (about 50 – 60%), but there is obviously still room for improvement.

Pain relief detailed to patients’ needs: “Patient Controlled Analgesia (PCA)”:
This is a very elegant method of pain relief, and is satisfactory to 70 – 80% of patients. The traditional drugs (morphine, pethidine etc.) are used, but the amount that is administered is individualised to every patient’s needs: it is now not the nursing staff or the prescribing doctor who dictates how much painkiller the patient is receiving, but the patient him- or herself.

This is important, because every patient has a different pain treshold and sensitivity to opioids, and even in the same patient, opioid requirements change during the course of the day.

How does it work?
The anaesthetist prepares a small bag of morphine (or other opioids), which is put into a special pump, and connected to a vein or the intravenous fluid line. This pump can be (often electronically) programmed to the patient’s individual needs. When the patient presses a button on the pump, it will inject a small amount of painkiller straight into the bloodstream.

This amount is about five times less than what nursing staff would inject into the muscle, but it can be administered much more frequently, like every five minutes. The patients can therefore decide exactly how much painkiller they get, they do not have to wait for nursing staff and will not need any extra painful injections.

To prevent overdosing and abuse, a safety mechanism built into this pump will allow the patient to get painkiller only every five or 10 minutes or less, depending on how it is programmed by the anaesthetist. The patient can press the button hundreds of time in succession, but the pump will always wait the programmed amount of time since the last shot before allowing another one. Another safety mechanism is that when the patient becomes comfortable, he/she often falls asleep, because of the sedative effect of the opioids, and stops pressing the button, until pain wakes them up again.

The PCA pump allows patients to choose exactly the amount of painkiller they receive, and to balance the pain relief against the side-effects of the painkillers: if they want to be painfree, they can press the button often; if they want to be more awake, e.g. when visitors come, they press the button less often and will put up with some more pain.

The reason that opioids are given too little, too late is the overwhelming fear the nursing staff have of the side-effects. The most dangerous one is respiratory depression. Indeed, if opioids are given to somebody not experiencing pain, the side-effects will clearly show: respiratory depression, sedation, also itch and nausea, and because of the euphoric effect, addiction. However, if an opioid is given to somebody who has severe pain, the primary effect will be its painkilling, with very little, if any, effect on respiration, sedation, addiction, itch and nausea.

Somebody who has been given an opioid for pain will not stop breathing! Unfortunately, nursing staff worldwide are so scared of this side-effect that they generally leave their patients in pain, which is completely unnecessary.

Read more:
Muscle pains
Pain control

Arthritis Foundation of South Africa
Multiple Sclerosis South Africa
The South African Society of Physiotherapy


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