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As surgeons, we are often asked, and indeed often choose, to administer nerve blocks intraoperatively. These techniques are often learnt on the job and not formally taught; however it is important to be aware of the general risks and benefits associated with these blocks, as well as basic anatomy and proper techniques of administration.
Risks
- Nerve damage
- Infection
- Haematoma
- Failure
- Drug allergy
- Inadvertent injury to an insensate limb e.g. smoking/ironing with a insensate arm
- Systemic local anaesthetic (LA) toxicity
Causes: Drug overdose, inadvertent intravascular injection, rapid absorption of bolus dose, cumulative effect of infusions or repeated doses, susceptible patients e.g. cardiac conduction blocks
A very useful AAGBI management guide can be found here
Benefits
- Postoperative pain relief
- Pre-emptive analgesia (some studies have shown a reduction in postoperative analgesia requirements when regional anaesthesia was established before incision made)
- Reduced surgical stress response
- Reduced use in volatile anaesthetics and opiates therefore reduced PONV and opiate side effects e.g. pruritus, reduced gut motility, respiratory depression, confusion, retention
- Early mobilisation and physiotherapy
- Shorter stays in ITU/hospital
Contra-indications: patient refusal, local infection, anticoagulation
A note on continuous peripheral nerve blocks
The maximum duration of single-shot peripheral nerve blocks is about 24 hours; more usually, it lasts between 8 and 16 hours with long-acting LA drugs such as bupivacaine or ropivacaine. Continuous peripheral nerve blocks can therefore extend duration of analgesia postoperatively and minimise opioid-induced side effects.
Disadvantages
- Motor block inhibiting patient rehabilitation or resulting in falls (if lower limb)
- Loss of lower limb proprioception makes walking difficult
Problems/complications
- Secondary block failure: occurs after the initial LA bolus to establish block wears off. Usually because the block needle successfully delivered LA around target nerves but catheter tip not correctly positioned
- Technical issues e.g. catheter dislodgement, kinking, blocking, leaking
- Infection (risk factors include catheters >48h, femoral or axillary site, lack of antibiotic prophylaxis, diabetes, ICU admission)
- Neurological injury
Technicalities
Any commercially available medical infusion pump can be used to infuse LA perineurally via a peripheral nerve catheter, but portable devices are preferred. Consult your friendly anaesthetist regarding LA concentration, dosages and speed of infusion.
References
Warman P, Conn D, Nicholls B, Wilkinson D. Regional Anaesthesia, Stimulation, and Ultrasound Techniques. Oxford Specialist Handbooks in Anaesthesia. 1st ed. USA: Oxford University Press; 2014.
Cave G, Harrop-Griffiths W, Harvey M, Meek T, Picard J, Short T and Weinberg G. AAGBI Safety Guideline on Management of Severe Local Anaesthetic Toxicity [Internet]. 2010 [cited 16 October 2018]. Available from: https://www.aagbi.org/sites/default/files/la_toxicity_2010_0.pdf
Author:
Ms Yanyu Tan
| Speciality:
Anaesthetics/ICU
| Date Added:
09/11/2018
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