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Ensuring prompt diagnosis and treatment of epidural abscess

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VOL: 101, ISSUE: 20, PAGE NO: 36

Julie Murdoch, RGN, MSc, is clinical nurse specialist in pain management, Pain Management Services, Royal Devon and Exeter Foundation Trust

Epidural injection and catheter insertion are common practice in most acute trusts. An epidural abscess is a rare but potentially catastrophic complication of these techniques. It can result in permanent paralysis with double incontinence if not detected at an early stage and promptly treated. The incidence of epidural abscess formation associated with epidural analgesia is less than 0.1 per cent.

Epidural injection and catheter insertion are common practice in most acute trusts. An epidural abscess is a rare but potentially catastrophic complication of these techniques. It can result in permanent paralysis with double incontinence if not detected at an early stage and promptly treated. The incidence of epidural abscess formation associated with epidural analgesia is less than 0.1 per cent.

Epidural abscesses also occur in patients who have not received epidural analgesia. In a review of 915 patients, only 5.5 per cent of abscesses were due to epidural analgesia (Reihsaus et al, 2000). However, the symptoms, treatment and potential outcome remain the same whatever the cause.

Anatomy of the epidural space
The epidural space surrounds the spinal cord and is encased within the vertebral canal. It contains nerve roots, fat, blood vessels, and lymph vessels. The epidural space runs the length of the vertebral column. Drugs can be injected or infused into this space, most commonly in the lumbar and thoracic regions.

Source of infection
Skin abscesses and furuncles are the most common source of infection. Infection related to epidural catheterisation is associated with:

- Poor aseptic technique;

- Direct spread, for example tracking from the skin along the catheter path;

- Haematogenous spread in bacteraemic patients, that is when bleeding caused by needle or catheter trauma allows organisms to enter the epidural space (Carson and Wildsmith, 1995).

The catheter itself can also act as a focus for infection. The most common causative organism is Staphylococcus aureus (Joshi et al, 2003; Lu et al, 2002; Kindler et al, 1998). Some patients are at higher risk of developing infection (Box 1).

Diagnosis and treatment
Symptoms generally include signs of spinal cord compression and infection (Box 2). Early recognition, diagnosis and treatment are essential to improving the chances of the patient making a full recovery. Delays of longer than 24 hours are associated with an increased incidence of permanent neurological deficit. It is recommended (with epidural haematoma) that the delay should be no more than eight hours (Breivik, 1998).

Magnetic resonance imaging (MRI) is used to confirm diagnosis. Patients generally need to undergo spinal surgery to remove any abscess or pus from the epidural space, thus decompressing the spinal cord. Antibiotic therapy is also commenced. The degree of neurological deficit is directly related to the treatment outcome. Individuals with severe neurological deficit, such as paralysis, prior to treatment are less likely to recover normal function following treatment.

Nursing implications
Nurses play a key role in caring for patients with epidural analgesia and should have the knowledge and skills needed to reduce the risk of complications. Most trusts now require documented evidence of competency-based training and assessment. Acute pain teams have been introduced to most acute trusts following the working party report on post-operative pain management (Royal College of Surgeons, College of Anaesthetists, 1990).

The acute pain nurse is responsible for providing epidural training and assists in the monitoring of patients with epidural analgesia. Although the risk of developing an epidural abscess is low, nurses must be aware of the early symptoms to ensure prompt diagnosis and treatment. The management of risk is underpinned by infection control measures, patient monitoring and patient and carer information.

Infection control measures

Infection control begins with the anaesthetist's assessment of the patient. Potential contraindications to epidural catheter placement include local infection, pyrexia, and bacteraemia or septicaemia.

Insertion of an epidural catheter is a strict aseptic technique, usually performed in theatre or in the anaesthetic room. It is recommended that the anaesthetist wears sterile gloves and apron with some trusts also requiring the use of masks.

The epidural catheter insertion site is covered with a sterile, transparent, semi-occlusive dressing. It is then secured to the patient's back using tape. A bacterial filter (200µm) is attached to the catheter to reduce the risk of infusion of bacteria and foreign bodies. Ideally, any syringes or bags of infusate should be prepared under sterile conditions.

The nursing staff are responsible for checking the epidural insertion site for any signs of inflammation, exudate and movement of the catheter. Our team recommend that this is recorded at least every eight hours. Any concerns should be reported to the pain nurse or anaesthetist. Generally, dressings are left in situ unless there is excess leakage at the site, with any dressing change being strictly aseptic. The risk of infection increases if the site is uncovered or multiple dressing changes are required. The decision may be made to remove the epidural catheter should this occur.

Epidural catheters may also need to be removed should there be disconnection of the catheter from the filter. We do not advocate that staff reconnect catheters following filter disconnection. Staff should obtain advice from the pain nurse or anaesthetist and the patient must be made aware of any increase in infection risk.

Epidural catheters generally remain sited for up to five days. Occasionally, catheters are 'tunnelled', which means they remain sited for longer periods as it is more difficult for infection to track to the epidural space. Usually, for the purposes of childbirth and postoperative pain management, catheters are untunnelled. Tunnelled catheters may be used following trauma and for patients who have intractable cancer pain; these patients are expected to have prolonged analgesic requirements.

Removal of the epidural catheter is an aseptic technique. Some trusts automatically send catheter tips for testing. The tip should be sent for culture in all patients who are pyrexial, have inflammatory changes at the insertion site or have had the catheter sited for longer than five days. The site is then covered with a sterile dressing for 24 hours.

Monitoring

Monitoring of the epidural site has been included in the infection control measures. The site must also be examined following removal of the catheter to ensure adequate healing. Any signs of infection should be reported to the medical staff and swabs sent for testing.

The patient should also be monitored for signs of neurological deficit. Epidural infusions contain local anaesthetic, which often results in some numbness and/or leg weakness. The best method of checking sensory loss is to use the patient's response to cold sensation. Ideally, ice in a glove is used. The nurse is looking for areas of numbness and this should be recorded on the epidural monitoring chart. The numbness should not extend above the nipple line; numbness above this level denotes a high level block that can affect respiratory and cardiac function, such as decreased respiratory effort, bradycardia, and hypotension. Any dense weakness, particularly the inability to move one or both legs must be reported. Occasionally, an epidural infusion will be turned down or off to see if the numbness reduces; this would denote local anaesthetic action rather than spinal cord compression. Some trusts use the Bromage score to assess motor function (Table 1).

Monitoring of neurological function should continue after the epidural has been removed. The local anaesthetic action generally recedes within six hours of removal. Any residual deficit should be reported. Epidural abscesses can take days or weeks to form. It is therefore important for the patient to report any back pain, site infection or neurological deficit following catheter removal.

Patient information

Patients and/or carers should be informed of the potential complications of epidural analgesia. This is particularly important in cases of epidural abscess, which can develop following discharge from hospital. Patients need to know the risks of the procedure and the associated signs and symptoms. They also need to understand the importance of reporting symptoms immediately, either to the nurse when they are in hospital or to the GP once they are home.

Epidural haematoma
Epidural haematoma is also a rare complication associated with epidural analgesia. An epidural haematoma is a collection of blood within the epidural space, which can result in spinal cord compression. The symptoms are similar to those of epidural abscess although there will be no signs of infection. Again, this requires prompt treatment to improve outcome. Diagnosis is confirmed by MRI. Treatment generally involves surgical decompression.

Conclusion
Epidural abscess is a rare complication of epidural injection or catheterisation. Long-term neurological deficits can be minimised by early diagnosis and prompt treatment. It is essential that nursing staff monitor the patient appropriately so that signs of this complication are recognised quickly and reported immediately to the pain team or anaesthetist. Patients need to be aware of the risks of the procedure and the symptoms to look out for. They also need to understand the importance of prompt reporting of symptoms to a health care professional.

Learning objectives
Each week Nursing Times publishes a guided learning article with reflection points to help you with your CPD. After reading the article you should be able to:

- Understand the anatomy of the epidural space;

- Be able to recognise the symptoms of epidural abscess;

- Know the infection control measures for this area of care;

- Know your actions should you suspect an abscess.

Guided reflection
Use the following points to write a reflection for your PREP portfolio:

- Outline where you work and why this article is relevant;

- Describe what the article says about preventing infection and explain how this is managed where you work;

- List the signs of epidural abscess and your actions should you suspect a patient may have developed this problem;

- How do you plan to use and share the information within this article?

- This article has been double-blind peer-reviewed.

For related articles on this subject and links to relevant websites see www.nursingtimes.net

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