Question 8

College answer

Potential causes

Microcirculatory disturbance secondary to DIC/Vasopressor requirement/worsening septic state.

Suggested by:
Clinical deterioration of patient: escalating vasopressor requirements, worsening acidosis etc. Likely a gradual change not clearly temporally associated with line insertion
Likely to see similar changes in the other limbs
Radial pulse present, arterial waveform present/normal.
Doppler USS, arteriography: - no abnormalities
 

Traumatic Injury to artery secondary to line insertion
Suggested by:
May be history of difficult insertion, multiple attempts. Other limbs not affected
Likely to manifest relatively quickly after line insertion. Pulse may not be present, arterial waveform abnormal
Imaging may reveal arterial dissection flap, lack of flow distal to line.

Embolic/thrombotic phenomena (including inadvertent drug administration via line)
Rapid onset
History of drug administration through arterial line
ay be other embolic phenomena
May have patchy ischaemic changes over digits
Waveform may be absent or present/normal depending on site of embolus
Imaging may demonstrate thrombus.

Examiners Comments:

Candidates listed the causes, but commonly did not outline how they would distinguish between them. The answer template focussed on history and clinical examination, whereas the candidates’ answers focussed mainly on extensive investigations which would not have been appropriate. This meant that the answers often lacked depth, and therefore did not score well.

Discussion

One can only add very little to what the college had already

The possibilities are:

• Complication of line insertion
  • Possible complications which threaten limb perfusion include:
    • Mis-sized catheter (resulting in vessel occlusion)
    • Haematoma causing compression
    • Laceration causing vasospasm
    • Intimal dissection
    • Vessel  thrombosis
  • Distinguishing features:
    • Rapid onset
    • Evidence of multiple attempts
    • Pain and swelling at the insertion site
    • Dissection or thrombosis detected on angiography or ultrasonography of the affected limb
• Complication of critical illness
  • Severe shock may give rise to poor limb perfusion
  • Distinguishing features:
    • Gradual onset
    • All limbs will be poorly perfused
    • Vasopressor requirements will be high
    • Angiography or ultrasonography of the affected limb will demonstrate normal patent vessels
• Embolic phenomena
  • ​​​​​​​Due to 
    • Air embolism from the counterpressure set
    • Accidental administration of medications
    • Thrombi (from the line insertion site or from upstream, eg. in the context of AF)
    • Cholesterol emboli (also could be from line insertion)
    • Forgotten guidewire
  • Distinguishing features:
    • Rapid onset
    • History of drug administration or guidewire mismanagement
    • Vessel obstruction detected on angiography or ultrasonography of the affected limb

Scheer,Perel and Pfeiffer.Complications and risk factors of peripheral arterial catheters used for haemodynamic monitoring in anaesthesia and intensive care medicine. Crit Care. 2002; 6(3): 199–204.