<unk> may be caused by: * Puncture of distal vein wall during venipuncture * Puncture of any portion of the vein wall by mechanical friction from the catheter/needle cannula * Dislodgement of the catheter/needle cannula from the intima of the vein which may be a result of a poorly secured IV device or inappropriate choice of venous site to puncture. * Improper cannula size or excessive delivery rate of the fluid
Infiltration 
Reabsorption
Countercurrent exchange
Excretion
Redox
Reuptake
Lufttransport
Bioconcentration