Epidural

This covers insertion of an epidural catheter. Management of an epidural (including complications of management), and particulars of the labour epidural are covered elsewhere.

Indications and Contraindications

General contraindications to neuraxial techniques are covered under principles of neuraxial anaesthesia.

Epidural catheters are commonly used for:

  • Analgesia
    • Adjunct to major abdominal and thoracic procedures
      In general, offers significant benefit in high-risk patients and high-risk surgery:
      • Reduces stress response
      • Reduces incidence of serious complications
      • Provides excellent analgesia
      • In combination with a general anaesthetic.
    • Labor
    • Chronic pain
  • Anaesthesia
    • As a sole technique, e.g. epidural top-up
    • As a combined spinal-epidural technique

Equipment

  • Procedure tray
  • Epidural kit
    Containing:
    • Tuohy needle
    • Frictionless syringe
    • Epidural catheter
    • Catheter connector and filter
  • Skin local anaesthetic
    In a 5ml syringe with a 23G needle.
  • Opioid
    e.g. Fentanyl.
  • Epidural local anaesthetic
    e.g. 20ml 0.2% ropivacaine.
  • Dressing

Technique

  • Preparation
  • Procedure
  • Post
  • Removal

Preparation

  • Obtain good IV access
    14-16G.
  • Obtain a pre-procedure BP
    Maternal hypertension may suggest pre-eclampsia.
  • Obtain consent
  • Prepare equipment

Procedure

  • Position the patient
    Most failures are related to poor positioning.

    • If sitting, ensure:
      • Flat, level mattress
        Commonly bed is not level or mother may be sitting on the division in the mattress.
        • If possible (e.g. operating table), bed can be tilted (slightly) so that the pelvis rocks forward, and the patient must bring their centre of gravity forwards to avoid toppling backwards off the bed
          This ↑ lumbar kyphosis.
      • Feet flat on a stool
      • As far back on the bed as possible
        Patients back should be closest to you, with their calves touching the side of the bed.
      • Ensure knees are higher than hips
      • Hold a pillow close to the chest
      • Place chin on chest and relax shoulders
      • Ensure knees, hips, and shoulders are in a line
      • Slump

  • Identify the target interspace

  • Prepare the skin

    • Chlorhexidine is superior
      Should be kept away and separate from the procedure tray, and allowed to dry fully. Ideally should be applied by the assistant.

  • Hat, gown, glove, drape
    Place a hat on the patient as well.

  • Prepare equipment
    Prime catheter with saline.

  • Skin local
    23G needle is usually adequate to anaesthetise the interspinous ligament in the non-obese patient.

  • Approach may be midline or paramedian

  • Insert Tuohy needle through the skin and supraspinous ligament

    • Needle will be held firm in the ligament - on letting go the needle will be tethered, whilst it tends to fall if in fat
    • Typically 2-3cm deep
    • Remove stylet/obturator from Tuohy needle and attach loss of resistance syringe

  • Slowly advance needle and syringe

    • Maintain contact with the patient and apply countertraction to the needle to minimise effect of patient movement on needle position
    • With saline:
      • Majority of forwards pressure should be on the plunger of the syringe
        Just enough pressure should be applied to the hub of the needle such that minimal saline is injected into the ligament.
        • Too much pressure on the plunger means the ligament becomes oedematous and boggy
        • Too much pressure through the needle hub may lead to accidental dural puncture
      • Consider hydrodissecting the epidural space with saline once it is found, to open up the space in preparation for the catheter
        Saline commonly flows from the needle afterwards, and may be concerning for dural puncture.
    • With air:
      • Carefully advance the syringe < 1 mm at a time
      • Check for loss of resistance by intermittently ballotting the plunger
      • Minimal air should be injected into the space.

  • Remove syringe
    Observe for:

    • CSF
      Typically continual, brisk flow. If uncertain, can check sample for glucose. See accidental dural puncture.
    • Blood
      If blood returns through the Tuohy needle it should be withdrawn. Attempt cannulation at a different interspace.

  • Thread the catheter

    • Warn for potential of transient electric shock sensation
      Ensure this has resolved when the catheter has been adjusted to the correct position.
    • Never withdraw the catheter through the Tuohy needle
      It may shear off and be retained in the epidural space.
    • Aim to leave the catheter at 3-5cm
      5cm with a multiorifice catheter or 3-4cm with a uniorifice catheter is optimal for analgesia.
      • ≥ 7cm is associated with
      • < 3 cm is associated with dislodgement

  • Observe catheter for:

    • Saline
      • Continuous flow suggests dural puncture
        Can be confirmed with:
        • Easy aspiration of CSF
        • Testing for presence of glucose
      • Meniscal drop is not helpful once the dural space has been pressurised (i.e; with saline), and is rarely useful with loss of resistance to air techniques
    • Blood
      Indicates cannulation of an epidural vein.
      • Epidural veins can be cannulated during insertion
        More when the veins are engorged, as occurs in:
        • The sitting position
        • Pregnancy
      • If blood is aspirated from the catheter:
        • Remove the Tuohy needle
        • Pull the catheter back 1-2cm
        • Flush the catheter with saline
        • Lower the catheter to see if blood flows freely
          If no blood flows, gently aspirate.
        • If:
          • Blood flows or is aspirated
            Withdraw it 1cm and flush with saline, then check for free-flowing or aspirated blood.
          • No blood flows
            Cautiously give test dose.
          • Blood flows or is aspirated, and the epidural is 3cm in the space.
            Remove and try at a different interspace.

  • Connect filter

  • Deliver test dose
    Ensure HR, BP, and SpO2 monitoring.

  • Apply dressing
    Can provide second loading dose at this stage.

Post-Procedure

  • Measure BP Q5 minutely for at least 20 minutes
    Continue longer if BP is labile.
    • BP should be checked 5 minutes after every subsequent top-up or bolus
  • Evaluate for intrathecal injection
    • Presence of motor block
  • Document procedure
    Should include:
    • Name
    • Date and time
    • Consent and risks discussed
    • Patient position
    • Aseptic techniques used
    • Level, approach, and needle used
    • Loss of resistance technique
    • Technique used
    • Depth to space
    • Presence/absence of CSF, blood
    • Length of catheter in space
    • Bolus dose
    • Efficacy and any neurology
    • Complications

Dosing

Dosing epidural depends on:

  • Targeted block level
  • Required speed of onset
  • Desired density of blockade
    Analgesia vs. surgical anaesthesia.

Analgesia:

  • Ropivacaine 0.1-0.25%

Anaesthesia:

  • Ropivacaine 0.5%
  • Lignocaine 2%

Complications

  • Dural puncture (~1/100)
    Post-dural puncture headache.
  • Hypotension (Up to ~1/30)
    May lead to nausea.
  • Respiratory depression (~1/200)
  • Epidural haematoma (~1/150,000)
    Affected by:
    • Intra-abdominal pressure
      High IAP impairs epidural venous drainage.
    • Needle size
    • Use of anticoagulants
  • Epidural abscess (0.05%)
  • Neurological damage (0.5%)
    • Typically transient
    • Majority associated with motor block rather than pain
    • Poorer outcomes are associated with:
      • Delayed (> 24 hour) presention
      • No surgical intervention
    • Severe neurological damage is associated with:
      • Delayed diagnosis of haematoma or abscess
      • Haematoma in 50% of cases
      • Administration of heparin intraoperatively in > 50% of cases
      • Presence of pre-existing coagulation abnormality in 75% of cases
  • High block
  • Urinary retention
    • IDC placement
  • Itch
    • Due to presence of opioids within epidural
  • Back pain
    Localised pain due to tissue trauma from the needle is common. Note that:
    • Pre-existing arthritis/osteoporois ↑ risk of back pain
      Epidural analgesia does not ↑ this risk.

Management of Complications Relating to Epidural Insertion{#comp}

This covers complications of insertion. Troubleshooting the working epidural is covered here.

Complications of epidural insertion include:

  • Accidental dural puncture
  • Subdural injection
  • Intravascular injection
  • Broken epidural catheter
  • Paraesthesia

Accidental Dural Puncture

Management of PDPH is covered here.

Dural puncture is:

  • Common
    1-2% of epidural insertions.
    • Predominantly by needle
    • Rarely by catheter
      Important as may result in inadvertent total spinal.
  • May lead to PDPH
    75-85% in the labour epidural population.

Following dural puncture, one can either:

  • Use as an intrathecal catheter
    This is a higher risk technique.
    • Pass epidural catheter and leave 2-2.5cm in the space
    • Label clearly as SPINAL
    • Cautiously establish block
      Typically, intrathecal doses are ~1/10th of epidural doses.
      • Consider using 1.5-2ml of 0.25% bupivacaine with 15µg of fentanyl
    • Leave catheter in situ for 24 hours, but this is not supported by evidence
      Initially thought to reduce requirement for blood patch, however this is not born out in replication studies.
  • Remove and repeat
    • Higher risk of subsequent dural puncture
    • Cautiously test dose repeat epidural
      Some LA may migrate intrathecally.
  • Note there is no benefit for prophylactic blood patch

Subdural Injection

Occasionally, injection may be between the dura and the arachnoid. Subdural injection:

  • Typically causes a:
    • Delayed onset
      10-30 minutes may elapse; however block density tends to ↑ rapidly after onset. Hypotension may be the presenting symptom.
    • High block
      Due to reduced compliance of the subdural space compared to the epidural space, causing solution to rise higher in the space.
    • Weak/patchy block
      Due to spread of a small amount of LA through a large area.

Intravascular Injection

Intravascular injection of LA may:

  • Occur:
    • At insertion
    • Following migration/manipulation of catheter
  • Lead to systemic LA toxicity

Management priorities are:

  • ABC
  • Management of LA toxicity
  • Foetus
    Evaluate foetal heart rate:
    • If normal, labour may continue
    • Cat 1 LUSCS should be planned in setting of non-reassuring trace

Broken Epidural Catheter

  • Generally should be left in place

Paraesthesia

  • Occurs in 5-25% of insertions
  • If paraesthesia persists after catheter maniuplation then the catheter should be removed and re-inserted in a different space
    May be an association with severe neurological deficit.

References

  1. Don’t Panic! The Registrars Guide to the Epidural. Miles L, Christelis N.
  2. Susan M Nimmo, BSc (Hons) MB ChB (Hons) MRCP FRCA; Benefit and outcome after epidural analgesia. Contin Educ Anaesth Crit Care Pain 2004; 4 (2): 44-47. doi: 10.1093/bjaceaccp/mkh014
  3. http://www.nysora.com/regional-anesthesia/foundations-of-ra/3300-ra-in-anticoagulated-patient.html
  4. Rollins M, Lucero J. Overview of anesthetic considerations for Cesarean delivery. Br Med Bull. 2012;101:105-25. doi: 10.1093/bmb/ldr050. Epub 2012 Jan 4.
  5. The Association of Anaesthetists of Great Britain and Ireland, The Obstetric Anaesthetists’ Association. Regional Anaesthesia and Patients with Abnormalities of Coagulation. 2013.
  6. Narouze S, Benzon HT, Provenzano D, Buvanendran A, De Andres J, Deer T, Rauck R, Huntoon MA. Interventional Spine and Pain Procedures in Patients on Antiplatelet and Anticoagulant Medications (Second Edition): Guidelines From the American Society of Regional Anesthesia and Pain Medicine, the European Society of Regional Anaesthesia and Pain Therapy, the American Academy of Pain Medicine, the International Neuromodulation Society, the North American Neuromodulation Society, and the World Institute of Pain. Reg Anesth Pain Med. 2018 Apr;43(3):225-262.