FRCA Notes

Intra-arterial Injection

The curriculum requires us to be able to 'recognise an intra-arterial injection of a harmful substance and its appropriate management'

Resources

  • Accidental intra-arterial injection is a patient safety incident which may result in significant harm
  • The incidence is unknown, with older studies suggesting an incidence of 1 in 3,400 to 56,000

Patient factors

  • Difficult IV access inc. morbid obesity, dark skin
  • Aberrant (radial) arterial anatomy
    • 1% have superficial radial arteries in the forearm e.g. the antebrachialis superficialis dorsalis artery
  • Loss of arterial pulse:
    • Hypotensive patient in whom arterial flashback is less prominent
    • Thoracic outlet syndrome (arterial pulse lost with an abducted and internally rotated arm)
  • Anaesthetised patient (i.e. symptoms unrecognised)
  • Hypoxia (low PaO2 on sample from line may be falsely reassuring of a venous cannulation)

Cannula-related factors

  • Those with arterial line in situ ± inadequately trained staff
  • Positioning a-line close to IV access
  • Multiple infusions/injection ports
  • Antecubital fossa: unrecognised cannulation of brachial artery or aberrant ulnar artery
  • Dorsum of hand: unrecognised cannulation of superficial branch of radial artery

  • There are multiple pathophysiological mechanisms, which are likely to be drug-dependent
  • The final common pathway for all these pathophysiological mechanisms is thrombosis
  • This leads to ischaemia, inflammation, oedema and tissue necrosis
  • Mechanisms include:
    • Arterial vasospasm
    • Chemical arteritis due to endothelial inflammation
    • Direct endothelial cytotoxicity
    • Intraluminal drug precipitation, crystal formation and embolisation into the microcirculation
    • Endogenous inflammatory response e.g. release of thromboxane
      • Thromboxane can damage endothelium and induced platelet activation (and thus thrombosis)

Prior to injection

  • Backflow of bright red blood into tubing
  • Pulsatile blood in the tubing
  • High PO2 of aspirated samples
  • Transduction demonstrates arterial trace

Awake patient

  • Immediate, severe pain at site of injection
  • Skin hyperaemia/pallor
  • Paraesthesia
  • Arterial spasm/thrombus causing cyanosis

Anaesthetised patient

  • Failure of drugs to have expected effect
  • Severe ischaemia and digital necrosis (may take up to 72hrs to develop)

Thiopentone

  • If injected arterially, the tautomeric equilibrium swings to the keto-form, which precipitates into thiopental crystals
  • These wedge in small vessels and cause ischaemia and pain
  • Doesn't occur when given IV due to dilution with more venous blood

Other anaesthetic drugs

Class Drug Effect
Opioid Fentanyl None
Morphine None
Induction agent Propofol Hyperaemia, distal blanching
Thiopentone Ischaemia, necrosis, tissue death
Ketamine Necrosis
NMBA Suxamethonium None
Rocuronium Ischaemia
Atracurium Ischaemia
Pancuronium None
Benzodiazepine Midazolam ?None
Other Phenytoin Ischaemia, necrosis, tissue death
Amiodarone Ischaemia


Intra-arterial injection is an anaesthetic emergency, and I would seek senior anaesthetic support

Immediate management

  • Stop injecting the drug
  • Call for senior help
  • Follow local protocol/guideline (if available)

  • The degree of ongoing intervention will depend on the severity of the reaction, which itself will depend on the drug(s) injected

Further management

  • Leave cannula in situ for time being
    • Administer saline or heparin-saline flush, followed by infusion of saline e.g. 3ml/hr
    • Cannula may be used for angiography or intra-arterial therapy
    • Mark as arterial and not to be used (may be easier to just remove it to eliminate further risk)

  • Seek opinion from specialist teams, namely Vascular Surgery, IR and/or Plastic Surgery

  • Analgesia for patient e.g. NSAID, opioid
  • Elevate limb for up to 72hrs; to improve venous & lymphatic drainage and reduce compartment pressures

  • Vasodilation of artery
    • Papaverine 40-80mg
    • Sympathetic block of affected limb (also analgesic) e.g. stellate ganglion, interscalene, axillary block using LA or guanethidine
    • Prostaglandin analogues e.g. iloprost (PGI2)
    • Intra-arterial lidocaine (also analgesic) e.g. 10ml 1%, or 2ml/kg total dose

  • Anticoagulation
    • 5000 IU heparin bolus followed by heparin infusion for ≥72hrs, aiming APTTr 2-2.5
    • Continue anticoagulation for 10-14 days

  • No robustly demonstrable benefit from routine administration of either steroids or antibiotics

Subsequent management

  • Document in notes
  • Critical incident form
  • Fulfil duty of candour
  • Presentation at M&M etc.
  • Appropriate follow-up to ensure symptom resolution