FRCA Notes

Epidural Top-Up

Resources

  • Epidural top-ups can provide effective anaesthesia for LSCS or other procedures, avoiding further needling of the neuraxis and GA
  • Risks include failure (see below) and need for GA, or conversely high block

Factors associated with suitability for top-up
Good, bilateral blocks
No missed segments
Patient satisfaction
Minimal anaesthetist interventions/intra-partum top-ups
(Midwife satisfaction)

Catheter location

  • Visually inspect catheter to ensure appropriately connected

  • Gentle aspiration of the epidural catheter to ensure:
    • No inadvertent intravascular placement and risk of LA toxicity
    • No inadvertent intrathecal placement and risk of total spinal
    • Reportedly sensitivity 98% & specificity 100%; can give rise to false negatives

  • Epidural test dose of local anaesthetic
    • Benefits from helping confirm position
    • Risks delaying time to onset of adequate blockade for LSCS

  • Epidural test dose of adrenaline 10-15μg in lidocaine
    • An increase in HR of 10bpm one minute after injection combined with clinical evaluation (whilst patient not contracting) is associated with a ensitivity 100% and specificity 96% for intravascular placement
    • At that dose deemed non-harmful to the foetus

Top-up location

  • Both labour room and theatre are suitable locations for top-ups, each with benefits and risks
  • Labour room top-ups facilitate more rapid onset of surgical anaesthesia by the time patient is in theatre...
  • ...but with the risk of increased distance from help, monitoring difficulties and delayed recognition/management of complications
  • Interestingly, NICE say induction of anaesthesia (RA or GA) should take place in theatre

Local anaesthetic

  • Options include:
    • 2% lidocaine
    • (3% 2-chloroprocaine)
    • 0.5% (levo)bupivacaine
    • 0.75% ropivacaine
  • Choice of LA is patient- and anaesthetist-specific

  • Lidocaine has a shorter time to onset of surgical anaesthesia than the longer-acting agents (between 2mins and 5mins)
  • Use of additives (see below) does add some time, especially if unfamiliar with the technique
  • Chloroprocaine has a shorter time to onset, but a much shorter duration and intra-operative supplementation is frequently required

  • Mixing lidocaine and bupivacaine in an attempt to get the best of both worlds doesn't appear to confer benefit over each agent alone

Opioids

  • Fentanyl 50 - 100μg
  • Sufentanil 10 - 20μg
  • These increase speed of onset, improve quality of anaesthesia and provide intra-operative analgesia for visceral pain

  • Post-delivery of the feotus:
    • Morphine 2.5mg
    • Diamorphine 3mg (if you can find it)
  • Higher doses associated with increased opioid-related side-effects without significant additional analgesic benefit

Bicarbonate

  • 8.4% NaHCO3 (1mEq/ml) may be added to lidocaine at a dose of 1ml per 10ml lidocaine i.e. 2ml in 20ml
  • It raises the pH of the solution, bringing it closer to lidocaine's pKa and increasing fraction of unionised LA molecules
  • It reduces time to onset of surgical anaesthesia by a mean of 4.5min
  • Not suitable for use with (levo)bupivacaine or ropivacaine as it causes precipitation

Adrenaline

  • Benefits from:
    1. Causes vasoconstriction of the epidural venous plexus, leading to:
      • Reduced systemic absorption of LA and reduced risk of LA toxicity
      • Prolonged duration of action of LA

    2. Causes stimulation of ɑ2-adrenoreceptors in the superficial laminae of the spinal cord, improving the quality of anaesthesia
  • Typically a dose of 5μg/ml is used e.g. 100μg in 20ml

Others

  • Further studies are required to establish benefits/risks of using additional agents such as clonidine, dexmedetomidine, ketamine, magnesium and neostigmine

  • The incidence of failed top-up is quoted as 1 in 20, but with a wide range (0 - 21%)
  • A 2012 meta-analysis of patients undergoing top-ups found:
    • 10.7% required supplementation via IV or inhalational routes
    • 7.7% required a second anaesthetic technique (RA or GA)
    • 5% required GA
Risk factors for failure of top-up
Non-Obstetric anaesthetist topping it up (OR 4.6)
Anaesthetic top-ups required intra-partum (1 unscheduled top-up = 3x ↑ risk of failure)
↑ Parturient pain in the 2hrs prior to LSCS
↑ Degree of urgency (40x ↑ risk of failure due to lack of time)
↑ Duration of epidural use
↑ BMI and/or height
Air used for LOR technique at insertion

Options for management of failed top-up

  • General anaesthesia
    • Benefits from a fast onset, but comes with the standard array of risks associated with GA for LSCS
    • Proactive management of poorly functioning labour epidurals and avoiding top-up of unsuitable epidurals (see above) can reduce need for GA

  • Spinal anaesthesia
    • Benefits from being rapid onset and with a low risk of LAST
    • Risks high block or even total spinal, and can also fail
    • Can somewhat mitigate the risks by:
      • Using it '1st line' instead of attempting top-up of a dubious epidural
      • Identifying failed top-up early to reduce epidural LA volume given
      • Reducing volume of intrathecal injectate if failed top-up
      • If time allows, waiting until 30mins since the last epidural bolus dose (either via PCEA or during failed top-up)

  • CSE
    • Benefits from the rapid onset action of a reduced-dose spinal component, as well as extension of the block via the epidural component
    • Risks, however, include a longer time to perform the technique, LAST and an untested epidural catheter

  • Epidural anaesthesia
    • A repeat epidural carries similar risks to the CSE technique, but without the benefit of the rapid-onset spinal component

  • Continuous spinal anaesthesia
    • This technique allows fast, effective, titratable anaesthesia
    • However, it is largely unfamiliar and carries high risk of PDPH, infection and high spinal block