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Spinals and Epidurals

A common concern in POCU is the monitoring and management of regional anaesthesia - here we take a closer look...

Mr Evans

Your next patient comes out of theatre and into POCU:

Neuraxial Blockade

Neuraxial blockade can either be epidural or spinal anaesthesia or a combination of the two.

It involves an injection of pain-relieving drugs (local anaesthetic +/- opioids) into the epidural space (called epidural anaesthesia) or into the fluid surrounding the spinal cord, the cerebrospinal fluid (called spinal anaesthesia).

Have a look at the diagram below. Can you name the different structures labelled?
Epidural and Spinal Anaesthesia. (Source, ID: 1769472851)

The difference between Spinal & Epidural

Spinal blocks are a one-shot needle technique which provide a single dose of local anaesthetic to coat the nerves and usually numbs from the waist down to allow lower limb surgery.
Epidural blocks leave a thin catheter in situ which allows an ongoing slow infusion of local anaesthetic to continue running after surgery has finished. This provides continuous pain relief in the postoperative period which is good for patients who have had abdominal surgery as it allows them to take effective deep breaths and cough, thus reducing the risk of respiratory complications.
Check out the table below for more differences between the two:
Epidural vs Spinal. (Image credit: Ellie Powell)

Spinal

  • Injection of small dose of local anaesthetic (LA) into the cerebral spinal fluid (CSF) within the intrathecal space
  • Always injected below the 3rd lumbar vertebrae. The spinal cord usually ends at the L1/2 level so this avoids the spinal cord and aims to avoid injury.
  • The LA only lasts for about 1.5 hours, so for postoperative analgesia we can add a long-acting opiate – i.e. diamorphine or morphine (the dose may be reduced for elderly patients).
  • The patient’s legs are usually weak for about 6hrs as the LA gradually wears off
  • Depending on the opiate used, the effects can last for 12-24hrs from the insertion of the spinal. Patients will require more pain relief when this wears off.
  • Patients need increased monitoring during the first 24h post intrathecal opiate – the main risk is respiratory depression. See care plan below for details.
  • Anti-emetics and naloxone should always be prescribed – see sticker for drug chart
  • Prophylactic Low molecular weight heparin (e.g. clexane should not be given until 4h post spinal injection, and the inserting doctor should ensure the platelet level and coagulation levels are normal before inserting the spinal. Also that any anti-coagulation has been omitted as per national recommendations (can we have a link to this please) before a spinal can be inserted due to the risk of spinal haematoma (more on this later).

Epidural:

  • Catheter inserted roughly at level of surgical incision to provide analgesia to the correct dermatomal level
  • Normally epidurals are “loaded” with local anaesthetic by anaesthetist intra-op to assess it is working effectively postoperatively
  • Once confirmed that the epidural is the correct place and working effectively it is connected to bag of pre-made local anaesthetic (LA) mix which is delivered by programmed pump
  • The pump is locked and giving set is incompatible with IV access to avoid accidental IV administration of LA
  • LA is usually a weak concentration so patient should still be able to move their legs, and mixed with a small amount of fentanyl – usually 0.1% levobupivacaine with 2mcg/ml fentanyl
  • Depending on the insertion level i.e. thoracic vs lumbar the rate is usually 0-12 ml/hr (usually started around 8ml/hr but can be adjusted as required)
  • On top of this, the patient can give themselves a bolus – like a PCA (hence PCEA!) – a few ml with a lockout period (but not all hospitals have this option)
  • Again, antiemetics and naloxone should be prescribed – see pre-filled sticker for drug chart below
  • Epidurals are more unpredictable than spinals. We can’t tell how well they are going to work until the patient wakes up and we can assess their analgesia. They may work perfectly, but they may be unilateral, patchy and sometimes don’t work at all. Epidurals often require regular assessment and optimisation to ensure they are working effectively- therefore it is important to know how to assess the epidural (more on this coming up in 5.20).

Troubleshooting an epidural

  • Be sure to check connections are securely connected – importantly ensuring the filter is securely on! If it is disconnected this needs to be escalated to the NIC and doctor straight away as there is a potential risk of infection, hence this needs to reviewed and addressed as soon as possible.
  • Check the sensory block with ice/cold spray; the patient shouldn’t be able to feel cold, but will still feel wet/pressure
  • Check for a motor block- if unable to move legs this needs to be escalated as an emergency asap to a senior nurse and doctor who understands the principles of epidurals *more covered below. Initial treatment is stopping the epidural and calling for a senior review.
  • If the block is one sided-unilateral – turn the patient so the painful side is down. Gravity sometimes helps get the LA to one side
  • If this doesn’t work call the anaesthetist / pain team – they may need to give an additional bolus of LA down the epidural to establish the block
  • Sometimes the epidural just doesn’t work despite trying all the above measures. In this case, the options are either to re-site it or take it out and replace it with alternative analgesia such as a PCA. This will depend on the patient and the type of surgery they have had.

Potential problems with epidurals

Common

  • Hypotension: Due to blockade of the sympathetic nervous system it causes vasodilatation: sometimes patients need some vasopressor (e.g. metaraminol/noradrenaline) to counteract this to raise the blood pressure
  • Side effects of opioids: itching, nausea & vomiting. Antiemetics should always be prescribed. If these don’t work and side effects are severe, there is the option to switch to a plain bag of local anaesthesia without fentanyl

Rare

  • Leg weakness: the concentration used after surgery is weak so shouldn’t cause leg weakness. The patient should be monitored regularly to check they can straight leg raise. If they can’t, the epidural should be stopped and the patient re-examined in 1 hour. Usually, the patient will regain some power in their legs once the epidural wears off, but if they don’t – contact the doctor immediately.
  • Motor block: Rarely, the epidural can be inserted into the incorrect place. A motor block may signify that the catheter has passed through the dura and is placed in the CSF, causing a motor block. If the patient has motor weakness, the initial treatment is stopping the epidural and calling for a senior review urgently. *Rarely, patients can develop a spinal haematoma or abscess causing compression of the spinal cord. This is an anaesthetic emergency and must be diagnosed rapidly (see below for the identification and management)
  • Superficial haematoma: blood can leak from vessels that are damaged during epidural insertion or from catheter removal. This can’t be seen from outside but can cause a clot to press on the spinal cord or nerves. Clearly this is important, and the main defence against it is our awareness that it can happen. A haematoma can also be caused by anticoagulation, therefore, we always allow time between the giving low molecular weight heparin and removing the epidural.

Very Rare

Is the development of an Epidural Haematoma occurring in 1 in 150,000 patients. This normally presents 24-48hours after an epidural or spinal procedure.
Red flag symptoms of a haematoma include: + severe, localised constant back pain + leg weakness (unilateral or bilateral) + urinary/faecal incontinence.
This is an emergency and its TIME CRITICAL. The use of MRI is the gold standard for diagnosis. Click here for the NYSORA management summary of spinal haematoma)
Epidural abscesses present similarly to epidural haematomas but usually with a additional fever. This is also an emergency and investigation is similar to that of epidural haematoma.

Contraindications to neuraxial blockade

Of course, let’s not forget that there may be contraindications to patients receiving neuraxial blockade for their procedure or for postoperative analgesia.
These include:
  • Patient refusal
  • Allergy
  • Local infection
  • Bleeding disorders (low platelets count or clotting dysfunction) or medication (there are numerous anti-platelet medicines for prophylaxis or treatments)
  • Low blood volume
  • Fixed cardiac output (for example in aortic stenosis)
  • Raised intracranial pressure

Final thoughts on neuraxial blockade

Anticoagulants/antiplatelets

Healthcare professionals in Cardiff have the following information on their lanyard to help them remember what to do in the removal of epidurals and anticoagulants:

Removal of epidural catheter and anticoagulant guidelines

  • It is ok to have low molecular weight heparin (e.g. clexane) whilst having an epidural in, but care must be taken with timings of drug administration when removing the epidural (see on the right).
  • The same applies with anticoagulants (e.g. rivaroxaban, apixaban). Make sure you check with the pain team or anaesthetist before giving any of these if a patient has an epidural.
  • Don’t give any LMWH for 4 hours after the epidural has been inserted or removed
  • Don’t give any antiplatelets (except aspirin) or warfarin AT ALL if a patient has an epidural – they take a long time to wear off (longer than the epidural should be in for!)
  • The sticker should be put on the drug chart by an anticoagulants/antiplatelets that shouldn’t be given.
Epidural sticker. (Photo credit: Catherine Griffiths)

Rectus sheath catheters

  • Used for open abdominal surgery with midline incision, usually inserted by surgeons when closing
  • Bilateral catheters inserted into the rectus sheath
  • Not used with epidural but can be used with spinal anaesthesia
  • Likely to still need a PCA
  • “Loaded in theatre” with 30ml each side of 0.25% levobupivacaine; then connected to pre-mixed bag of plain 0.1% levobupivacaine (no fentanyl), which is delivered by epidural pump at 20ml/hr (10ml/h each side)
  • Prescribed on same chart as epidural “regional infusion of local anaesthetic”
  • Sticker on drug chart “local anaesthetic continuous infusion”
  • Additional monitoring will be necessary
  • If inadequate the anaesthetist or pain team can administer additional boluses of LA
  • Removed by day 5 or sooner if no longer required

Other LA catheters are used, which you may come across occasionally – the same principles apply.

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