Complications

• Give 5 mg vitamin K by slow (5 minute) iv infusion ^a
• Give a concentrate of factors II, VII, IX, and X at a dose of 50 units of factor IX per kg body weight ^c  
• If no concentrate is available give fresh frozen plasma (~ 1 litre for an adult) ^d
• Stop warfarin ^c

Major bleed (e.g. haematuria or epistaxis)

• Stop warfarin for 1 or more days ^c
• Consider giving 0.5 mg to 2.0 mg vitamin K iv (clinical response takes 4 to 6 hours) ^c  

INR > 5.0 without haemorrhage

• Continue warfarin and give 1 to 2 mg of vitamin K orally
  

Unexpected bleed at therapeutic levels of INR

• Investigate for underlying malignancy (look for GI and GU especially)
  

Other complications

• Warfarin-induced skin necrosis - this is very rare