Infusion of drug(s) into epidural space via epidural catheter
Indications for epidural infusions
- Thoracic, abdominal and lower-limb surgical procedures:
- Intraoperative analgesia
- Postoperative analgesia
- Analgesia for chest, abdomen, pelvis or lower-limb trauma.
Drugs for epidural infusion
The most commonly used epidural infusion is a local anaesthetic and opioid mixture.
Local anaesthetic can be used alone, to allow alternative opiate administration (e.g. patient-controlled analgesia).
Lowest possible effective concentration of local anaesthetic should be used, to maximise the preservation of motor function:
- Improves patient satisfaction
- Aids detection of neurological complications
- If higher concentrations used, infusion rate should be reduced periodically, to allow assessment of motor block
The use of other epidural adjuvants can be used to minimise opioid dosage, improving analgesia and minimising opioid-related side-effects [1–4].
- Opioids: fentanyl, morphine, hydromorphone
- α2 agonists: clonidine
- A meta-analysis comparing the efficacy of local anaesthetic alone versus local anaesthetic + opioid concluded that the combination of local anaesthetic + opioid was associated with a significant reduction in pain score on first postoperative day .
- The choice of opioid is determined by characteristics such as onset, duration of action and potency; these result from their physicochemical properties.
- Highly potent, rapid onset occurs in: high lipid solubility and low pKa.
- Long duration of action occurs in: relatively low lipid solubility.
- Opioids contain both tertiary amine and hydroxyl groups.
- Tertiary amine: ionised at physiological pH (7.4), making all opiates water-soluble.
- Hydroxyl groups: variation of hydroxyl groups confers different lipophilicity.
| Relative lipid solubility
| pKa (% unionised)
|| 8 (23%)
|| 7.6 (34%)
|| 8.4 (8%)|
| Epidural loading dose
|| 2–5 mg
|| 2–3 mg
|| 50–100 µg|
- Low lipid solubility (relatively hydrophilic)
- Slow onset of action (45–60 minutes) 
- Long duration of action (8–24 hours)
- Moderate lipid solubility
- More rapid onset of action (20–40 minutes)
- Moderate duration of action (10–20 hours)
- High lipid solubility
- Rapid onset of action (15–30 minutes)
- Shorter duration of action (2–4 hours)
Epidural loading dose: 75–150 µg
- Stimulates pre-synaptic alpha-2 receptors in dorsal horn of spinal cord.
- Inhibits release of noradrenaline, modulating nociceptive signal transmission.
- Synergistic effect with local anaesthetic/opiate.
- Block conduction via Aδ and C fibres.
- Local vasoconstriction impairs removal of local anaesthetic.
Infusion concentration 0.75–1 µg/ml
Patient-controlled epidural analgesia (PCEA)
Varying protocols for epidural infusion are dependent on drug dose and combination – refer to your specific institution’s policy.
- Patient self-administers drug bolus into epidural space via epidural catheter.
- Drug bolus controlled by epidural infusion pump with a pre-set bolus dose, bolus lock-out period and a maximum allowable dose over a given period.
- A PCEA may also include a background infusion rate.
Suggested guidelines for PCEA set-up :
||Drug and concentration
|| Basal rate (ml/h
|| Demand dose (ml)
|| Lockout (min)|
||Bupivacaine 0.025% + fentanyl 10 µg/ml
||Ropivicaine 0.08%+ fentanyl 2 µg/ml
|Lower abdomen, lower extremity and vascular: lumbar epidural
||Bupivicaine 0.0625% + fentanyl 5 µg/ml
|Lower abdomen with thoracic epidural
||Bupivicaine 0.125% + fentanyl 5 µg/ml
|Hip or knee surgery
||Bupivicaine 0.06% + fentanyl 10 µg/ml
|Hip or knee surgery
||Bupivicaine 0.06% + 1 µg/ml clonidine
|Bupivicaine and clonidine for abdominal hysterectomy
||Bupivicaine 0.125% + 0.75 µg/ml clonidine
|| 10 ml loading dose
|| 10 |
(NB 30 ml limit within 4 h)
Benefits of PCEA
- Bolus-only PCEA with local anaesthetic/opioid combination provides comparable analgesic benefit to continuous infusion with significantly smaller volume of solution [1, 2].
- Provision of analgesia with reduced incidence of motor block .
Ongoing care of all patients with epidural infusions or PCEA
Observations and monitoring :
- Following initial epidural bolus
- Blood pressure should be recorded every 5 minutes for 20 minutes.
- Following epidural infusion
- Respiratory rate, oxygen saturations, heart rate, blood pressure, temperature, pain score and sedation level
- Hourly for first 12 hours
- Every 2 hours from 12–24 hours
- Every 4 hours after 24 hours
- Continue observations for a minimum of 24 hours following cessation of epidural infusion/PCEA.
- Continuous epidural infusion/PCEA: minimum daily assessment of:
- Motor blockade (use of Bromage score – see below)
- Adequacy of analgesia (at rest and on movement/deep breathing)
- Signs of infection: erythema, swelling, discharge, fever
- Signs of haematoma: dense/unilateral motor or sensory block, urinary incontinence, faecal incontinence, new/worsening back pain.
Complications of epidural infusions and PCEA
- Systemic local anaesthetic toxicity
- Respiratory depression (immediate/delayed)
- High block
- No analgesic benefit
- Inadequate analgesia
- Missed segment/patchy block
- Nausea and vomiting
- Post-dural puncture headache
- Pressure sores
- Epidural haematoma
- Epidural abscess
- Spinal cord ischaemia
- Nerve injury.
Delayed respiratory depression
Epidural infusions commonly run for 2–3 days (maximum quoted between 4–5 days).
- A significant complication of epidural administration of opioids.
- Results from rostral spread of opioid to respiratory centre in medulla.
- Can occur up to 18 hours after administration.
- Incidence reported in 0.01–3% of patients .
- Patients at increased risk include the paediatric, elderly, obese and patients with obstructive sleep apnoea.
Bromage score 
||Degree of block|
|| Free movement of legs and feet
|| Just able to flex knees with free movement of feet
|| Unable to flex knees but with free movement of feet
||Almost complete (66%)|
|| Unable to move legs or feet
Author: Dr Rebecca Medlock
References 1. Wilson JA, Nimmo AF, Fleetwood-Walker SM, Colvin LA. A randomised double blind trial of the effect of pre-emptive epidural ketamine on persistent pain after lower limb amputation. Pain 2008; 135(1-2): 108–18.
2. Subramaniam K, Subramaniam B, Steinbrook RA. Ketamine as adjuvant analgesic to opioids: a quantitative and qualitative systematic review. Anesth Analg 2004; 99(2): 482–95.
3. Farmery AD, Wilson-MacDonald J. The analgesic effect of epidural clonidine after spinal surgery: a randomized placebo-controlled trial. Anesth Analg 2009; 108(2): 631–4.
4. De Kock M, Wiederkher P, Laghmiche A, Scholtes JL. Epidural clonidine used as the sole analgesic agent during and after abdominal surgery. A dose-response study. Anesthesiology 1997; 86(2): 285–92.
Further reading Khangure N. Anaesthetic tutorial of the week # 230: Adjuvant agents in neuraxial blockade anaesthesia. Available at http://www.frca.co.uk/Documents/230%20Neuraxial%20adjuvants.pdf
Hindle A. Intrathecal opioids in the management of acute postoperative pain. Contin Educ Anaesth Crit Care Pain 2008; 8(3): 81–5.