- Pain on injection can be immediate or delayed (10-20s later)
- Cause remains unclear
- Possible mechanisms include:
- Direct irritant effect of phenol (particularly that in aqueous phase)
- Effect of pH or osmolarity – considered less likely as solution almost isotonic with physiological pH
- Indirect effect due to release of local inflammatory mediators such as kininogenin
Detailed discussion is given in an article by tan et al.
- Injection technique:
- Large vein
- Slow speed of injection
- Local Anaesthetic:
- Lignocaine premedication (10-20mg given 10s before injection)
- Lignocaine mixed with propofol (10-20mg mixed with 190mg propofol)
- No clear evidence either method superior
- Temperature:
- Propofol cooled to 4 degrees
- Premedication with opioids
- GTN patch at site of injection
Detailed discussion is given in an article by tan et al.