17 August 2010

Questions and answers about epidural analgesia

Here our expert answers questions that are frequently asked about epidural anaesthesia.

What should happen if an epidural does not seem to work well?
The levels of temperature sensation must be tested with an ice cube. If the area is blocked by epidural local anaesthetic, the coldness will either feel warm or it will not be felt at all. If the surgical area is not covered by the anaesthetic, a top-up should be given and the rate of the infusion should be increased.

If these levels are adequate, the anaesthetist may have to increase the concentration of the epidural mixture.

Does a patient need to be weaned off an epidural infusion?
No, this is not necessary, as an epidural infusion is either running or not running. Diminishing the infusion rate will only decrease the effect on the anaesthetised area, which also happens naturally when the infusion is simply switched off.

Why does an epidural sometimes suddenly stop working?

  • There can be a number of different causes, which include the following:
  • There could be an infusion pump failure or a catheter disconnection. The latter can happen when a sudden movement pulls the catheter out of the epidural space.
  • An incorrect mixture, such as when the infusion rate is too low and the spread of the epidural block has become too small.
  • The epidural has been running for a few days and the patient has built up a tolerance.
  • There is a complication in the condition of the patient which is too painful for the epidural to block.
  • There has been a delay of more than 15 minutes in the changeover of infusion bags.
  • The infusion pump or the patient-controlled analgesia (PCA) pump has been set incorrectly or the patient does not understand how to use the PCA pump.

Can the epidural analgesia block important warning signs of possible complications?
No, the epidural infusion is usually too weak to block the severe pain that can be caused by surgical complications.

Is it possible to mobilise the patient while he/she is still receiving epidural analgesia?
It should not be a problem, as one of the main advantages of epidural analgesia is that patients can be mobilised without feeling pain. The epidural catheter should not be removed before the expected postoperative pain has vanished. It is not necessary that patients lie flat with an epidural – if all parameters are stable, the patient can sit and even walk.

What happens when a patient who always had a purely sensory block, also develops a motor block?
This could be serious and could be a warning sign of a serious complication of the epidural infusion. The anaesthetist needs to be informed. This happens when a haematoma (accumulation of blood that forms a clot or swelling) has developed in the spinal canal, or when the epidural block has converted to a spinal block, which in certain cases can lead to cardiovascular or respiratory suppression. It could also be that during the insertion of the epidural a small cut was made through which local anaesthetic has leaked into the spinal cord.

Who should prepare the mixture for epidural infusions?
Nursing staff can do this, but only if the anaesthetist has left very clear instructions on exactly what to do.

If a patient is pain free, does that mean that the epidural infusion can be switched off?

No, not at all. One should keep in mind that the patient is pain free because of the epidural infusion. Should the infusion be stopped, pain will most likely return within a few hours.

Reviewed by Prof CL Odendal, senior specialist at the department of anaesthesiology at the University of the Free State, April 2010.

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