BT_GS 1.30 Describe and compare the pharmacokinetics of intravenous induction agents …
BT_GS 1.31 Describe and compare the pharmacodynamics of intravenous induction agents …
Thiopentone is a terrific drug. Unfortunately, the current generation of trainees lack familiarity and confidence with it.
T / F compared with propofol, a standard induction dose of thiopentone causes less vasodilation and less hypotension
T / F when diluted with 20 mL water, 500 mg thiopentone makes a 2.5% solution, with a pH of 11 (regarding the pH, can you explain why you think this is true or false? Why is this pH necessary / not necessary?)
T / F in plasma, thiopentone is 80% bound to albumin
T / F thiopentone is a weak base with pKa 7.6 – therefore, 12% of an injected dose will be available to cross the blood brain barrier
T / F the majority of thiopentone is metabolised to inactive metabolites
T / F thiopentone effectively blunts the upper airway reflexes
Now that you’ve become fascinated by thiopentone, it would be useful to use this knowledge to answer some SAQ’s.
- Write short notes on the pharmacology of thiopentone.
- Compare and contrast the pharmacology of propofol and thiopentone.
- Explain the advantages and disadvantages of propofol and thiopentone for induction of general anaesthesia.
These 3 SAQ’s are in ascending order of complexity, in terms of the level of understanding they are testing. Regurgitating your summary notes (Q1) is low level knowledge – a candidate may score highly without really understanding what they are writing. But Q3 requires not only the application of PK and PD data – this information must be further organised to address the advantages and disadvantages. Scoring well on this question would demonstrate a high level of understanding (appropriate given the “core” nature of the drugs in question).
Have a go at answering the 3 SAQ’s above. While the 3 answers will each contain some of the same information, the final answers will be quite different. Hopefully this will help you reflect on the importance of reading the question!!