Regional Analgesia



Background

When a patient arrives in the department with a painful condition Think analgesia, sling, local anaesthesia, narcotics.

Do not send any patient away without some pain relief. You may only have to suggest they use the simple analgesics they have at home or can buy at a chemist.

  • Mild pain - paracetamol or an NSAID [Not in active PUD or Aspirin sensitive patients]
  • Moderate pain - a combination of the above two drugs
  • Severe pain - add Opioid analgesics (Dihydrocodeine 30 mg)

It is worth asking asthmatics whether they have taken NSAIDs before. You may wish to look at NNTs for oral analgesics [Bandolier]

For children

Please refer to paediatric doses and paediatric pain management. For skin wounds in children, topical anaesthesia should be used in preference to lignocaine infiltration [BestBets]. Use TAC in preference to EMLA for topical anaesthesia [BestBets]


Analgesia for severe pain

The safest and most effective way of providing adequate analgesia is to administer small quantities of diluted morphine intravenously. Most patients with acute myocardial infarction require about 5mg of morphine IV given with either 12.5 mg of Prochlorperazine or 10 mg of metoclopramide. The morphine can be diluted with equal amounts of water for injection. It is also important to appreciate that those patients with severe abdominal pain caused by peritonitis cannot wait indefinitely before they are assessed by on-call surgeons. Such patients would benefit greatly by titration of small amounts of intravenous opiates given at frequent intervals.

For paediatric patients and information on intranasal diamorphine (unfortunately not available in Eire) please refer to our paediatric analgesia section.


Local Anaesthesia

The toxic dose for Lignocaine is 3 mgs per kilo or 20 mls of 1% Lignocaine for an adult.

The dose in a child is 1 ml of 1% plain Lignocaine for each year of the child's age.

Local anaesthetics are best administered with the patient supine

Methods of infiltration for local anaesthetics.

  • Use as small a needle as possible.
  • Begin proximally.
  • Inject slowly.
  • Repeat process distal to the wound.
  • Wait, and test for anaesthesia after 5 minutes

Mx of Severe Local Anaesthetic Toxicity Signs of severe toxicity

Signs

  • Sudden loss of consciousness, with or without tonic-clonic convulsions.
  • Cardiovascular collapse: bradycardia, conduction blocks, asystole and VT.

Immediate management:

  • Stop injecting the LA, Call for help.
  • Maintain the airway, 100% oxygen and ensure adequate lung ventilation.
  • Confirm or establish intravenous access.
  • Control seizures: with Benzodiazepines.
  • Assess cardiovascular status throughout.

Management of cardiac arrest associated with LA injection:

  • Start cardiopulmonary resuscitation (CPR) using standard protocols.
  • Manage arrhythmias using the same protocols.
  • Prolonged resuscitation may be necessary.

Treatment of cardiac arrest with lipid emulsion:(70kg)>

  • Give an intravenous bolus injection of Intralipid® 20% 1.5 ml.kg-1 over 1 min (100 ml).
  • Start an intravenous infusion of Intralipid® 20% at 0.25 ml.kg-1.min-1(400 ml over 20 min).
  • Repeat the bolus injection twice at 5 min intervals if necessary (x2 further boluses of 100 ml)
  • After another 5 min, increase the rate to 0.5 ml.kg-1.min-1 if necessary (400 ml over 10 min)
  • Continue infusion until a stable and adequate circulation has been restored
  • Continue CPR throughout treatment with lipid emulsion
  • Recovery from LA-induced cardiac arrest may take >1 hr
  • Please report all cases to the Irish Medicines Board and the LipidRescueTM.
  • The Association of Anaesthetists of Great Britain & Ireland 2007 guidelines.

Nerve block

This is an extremely effective method of providing analgesia, especially in the upper limb. In general you must wait longer than direct infiltration for the block to work as the anaesthetic must diffuse into larger nerves. If the patient experiences pain in the nerve distribution then stop injecting immediately, withdraw slightly and try injecting again.

Avoid use Adrenaline around end arteries e.g. digital, nose, ear or penile blocks.

Median nerve block

Median Nerve Anatomy Wrist
  • Median nerve lies between flexor carpi radialis and palmaris longus
  • 1 to 2 cm proximal to distal flexor crease
  • Aim under palmaris longus
  • 4 - 5 mls 1% solution plus or minus Adrenaline
  • If resistance - stop
  • If swelling - correct
  • A further 1 to 2 mls over subcutaneous tissues may be needed.

Intercostal block

  • Good for # ribs 6,7,8 (does not block visceral pain which requires coeliac plexus block)
  • Contra-indicated where PTX would be dangerous (e.g. already reduced respiratory reserve)
Drawing of Intercostal block lateral view
Diagram of intercosatl block anatony from behind

Paravertebral block


Important Anaotmical Landmarks when considering Tibial Nerve Block

Tibial nerve block

For the sole of the foot.

Use 10 ml of 1% lignocaine ± Adrenaline. Do not use Adrenaline in patients with peripheral vascular disease.

Aim medial to the tendo Achilles behind the posterior tibia artery, between the tendons of flexor digitorum longus and flexor hallux longus.


Supra-orbital/supra-trochlear block.

Is used for forehead and scalp anaesthesia. The supra orbital nerve leaves the orbit through the supra orbital notch. This notch lies medially in the supra orbital rim, on a vertical line through the medial aspect of the cornea. The supra-trochlear nerve exits the orbit at the junction of the superior orbital rim and the medial wall of the orbit. The two nerves have a sensory distribution from forehead to coronal suture from mid-line to temporal region.

Infiltrate subcutaneously completely parallel to the supra-orbital rim above the eyebrow 5 ml of 2% lignocaine with Adrenaline. Do not infiltrate directly around the nerve or its foramen.



Content by Dr Íomhar O' Sullivan 11/12/2003. Reviewed by Dr ÍOS 08/07/2004, 25/05/2006, 27/02/2007, 18/02/2008. Additional background information on the management of LA Toxicity kindly provided by Dr Brian O' Donnell. Last review Dr ÍOS 28/12/18.