Knowledge
-
A. Physiochemistry
- A highly lipid-soluble alkylphenol.
- 2,6 di-isopropyl phenol
- 20 mL ampoules contain:
- 200 mg 1% propofol
- 10% soybean oil (solubiliser)
- 1.2% egg lecithin (emulsifier)
- 2.25% glycerol (make isotonic)
- Sodium hydroxide (buffer)
- pKa 11, pH 7
- 90% non-ionised @ pH 7.4
- weak acid
- stable at room temp, not light sensitive
- 1 mL = 0.1 g fat = 1.1 kcal
B. Pharmacokinetics
- Dose
- 2 mg/kg induction -> 2-6 mcg/mL
- 3-4 mg/kg in children
- 1 mg/kg load then: 10, 8, 6 mg/kg/h infusion (10m, 10m, cont) after 1 mg/kg loading - aims for blood conc of 3 ug/mL.
- Children: 15 mg/kg/h for 15 min, 13 mg/kg/h for 15 min, 11 mg/kg/h for 30 min then 9 mg/kg/h for 1-2 h, then 9 mg/kg/h for 2-4 h -> 3 ug/mL.
- Sedation 25-100 mcg/kg/min
- Plasma levels:
- major surg 4 mcg/mL (4-8 ug/mL)
- minor surg 3 mcg/mL
- 50% wake @ 1.07 mcg/mL (decrement lvl: 1.2 mcg/mL on TCI)
- 50% orientated @ 0.95 mcg/mL
- Psychomotor perfomance pre-op levels @ 0.3 mcg/mL
- Absorption - IV
- Distribution - Vdcc 0.5 L/kg, Vdss 2-10 L/kg
- Protein binding - 98% albumin
- Onset < 60s, peak 60-90s (slightly slower than thio: peak 30-60s); Offset 5-10 min (faster than thio).
- Metabolism - alpha1∆ 2 min, tß∆ 1h, CSHT-8h: 30 min. Conjugated to glucuronide & sulphate - water sol and renally excreted. 0.3% excreted unchanged.
- Clearance - 30 mL/kg/min.
- Children - larger central vol; longer CSHT (10m@1h & 20m@4h cf. 7m@1h & 10m@4h for adults); slower recovery; but require higher infusion rates and have higher clearance (req. same blood (=effect) conc as adults).
- NB: children have primarily pharmacokinetic differences not pharmacodynamic.
- Women - higher clearance.
C. Pharmacodynamics
- Mech - potentiates GABA inhibition.
- CNS - anaesthetic, anticonvulsant (?), antiemetic, antipruritic, amnesic.
- Not ant-analgesic like thio.
- Inc interthreshold range for temp
- CVS - 25-45% dec MAP, dec CO, dec SVR (dec SNS outflow; direct effect on veins, dec intracellular Ca mobilisation), HR unchanged (resets barorec response).
- Resp - resp depression (apnoea in 30% alone, 100% + narcotic), dec TV, inc RR, bronchodilation (slight), dep laryngeal reflexes.
- Renal - dec RBF, green urine.
- GIT - antiemetic, no hepatic effects.
- Haem - intralipid dec platelet aggregation.
- SEs - anaphylaxis rare; sig hypotension in volume depleted; hallucinations; abuse.
-
A barbiturate derivative (Brevital™, Brietal™) intravenous anaesthetic agent, no longer available in Australia although still used in other parts of the world.
Preferred for use in electroconvulsive therapy for its pro-seizure effects and comparatively short duration.
Compared to thiopentone
- Oxybarbiturate
- Made up in 50 mL to 1% solution
- 3x more potent
- 3x clearance (12 mL/kg/min)
- tß½ 3 h (STP 8h)
- Greater ionised proportion
- Less protein binding (65%)
- More rapid recovery: 2-3 min (smaller fat compartment, no active metabolites, ⇡ clearance)
- Higher incidence of pain on injection
- Pro-convulsant/epileptiform EEG (excitatory in 30%)
- PONV (30%)
- Less dec MAP, more inc HR than STP
- More pronounced resp depression
-
A collection of landmark papers relevant to anaesthesia and anesthesiology.
Generally, these papers are practice changing and hold current, ongoing significance beyond their historical importance.
This is a dynamic and changing document that will be updated, pruned and added to as appropriate. Many of these papers have free full-text provided by the publisher because of their significance.
summary
-
A collection of the top 20 most cited pediatric anesthesiology papers of all time from Ravi Tripathi's excellent 2011 study:
Tripathi, R. A bibliometric search of citation classics in anesthesiology. BMC Anesthesiol. 2011 Jan 1;11:24.
These are probably 20 articles that every anaesthetist or anesthesiologist with even a small component of pediatric practice should be aware of – not necessarily because they are still practice changing, but because they our foundational to our current understanding and practice of pediatric anesthesia.
These articles help to both show where we have come from, and where we may be heading.
summary
...and 2 more notes
-