An intravenous sedative hypnotic, propofol is available as an opaque white emulsion including soybean and egg lecithin. The preparation most frequently used is a concentration of 1% (10mg/ml) but it can be diluted in 5% dextrose up to 2mg/ml. Propofol phosphate (fospropofol) is a newer water-soluble invention, not common in clinical practice in 2008.
Propofol is popular for its rapid onset of action, smooth recovery, and amnesic properties. In contrast to some other hypnotic agents it does not cause nausea. It is not an analgesic. It has some anticonvulsant activity.
- Induction of general anaesthesia in adults and children over 1 month of age
- Maintenance of general anaesthesia in adults and children over 3 years of age
- Sedation for surgical and diagnostic procedures in adults over 17 years of age
- Sedation in intensive care in adults over 17 years of age
Propofol is administered only intravenously. It can be bolused rapidly, and indeed induces anaesthesia faster this way. However it should not be administered as a rapid bolus in the elderly. The induction dose for general anaesthesia is around 2mg/kg. This is increased in the anxious, in children, and in alcoholics. It is decreased in the elderly. Propofol can be infused as part of a total intravenous anaesthetic (TIVA). It can be administered via an infusion pump set up to deliver a target controlled infusion (TCI).
- Monitor blood lipids in potential fat overload or prolonged infusion (> 72 hours) situations
- The high prolonged doses given with refractory status epilepticus may produce significant mortality and morbidity
- Children under 17 years
Cautions and Interactions
- At > 5mg/kg/hour in combination with catecholamines and/or steroids, a rare "propofol infusion syndrome" has been described, causing or worsening:
which with prolonged infusions can be fatal
Some formulations of propofol are made using a soya bean oil emulsion. There is potential for a cross-over reaction in patients who have peanut allergy as both are legumes, although the manufacturers do not give figures. Probably over-cautious to avoid its use, but medicolegally safer.
1ml of 1% propofol contains 100mg of fat
- Pain at the site of injection
- Vasodilatation leading to hypotension
- Apnoea (often transient)
- Myoclonic movements
- Alteration of the lipid profile on prolonged infusion
Propofol is a weak acid. It has a pKa of 11. It is presented in an oil in water emulsion with soybean oil, glycerol, egg lecithin, disodium edetate, and sodium hydroxide. This emulsion has a pH of 7 - 8.5.
The clinical effect of propofol is seen within one arm to brain circulation time.
GABA-A receptors are ligand-gated ion channels for chloride ions. They have an inhibitory function on neurones. Propofol may positively modulate this by slowing GABA-A closing times.
The endocanabinoid system may also be involved.