Anaesthetics Flashcards
Which anaesthetic agent is useful in patients who suffer from post-op nausea + vomiting?
propofol - is also an anti-emetic
What is thought to be the mechanism of action of volatile liquid anaesthetics (desflurane, isoflurane, sevoflurane)?
Exact mechanism of action unknown. May act via a combination of GABA, glycine and NDMA receptors
What are 3 adverse effects of volatile anaesthetic agents (desflurane etc.)?
- myocardial depression
- malignant hyperthermia
- halothane (not used comonly any more) hepatotoxic
What is thought to be the mechanism of action of nitrous oxide?
exact mechanism of action unknown. May act via a combination of NDMA, nACh, 5-HT3, GABA and glycine receptors
What is an adverse effect and therefore contraindication of nitrous oxide?
diffuses into gas filled compartments of the body therefore leading to an increase in pressure; should therefore be avoided in pneumothorax
What are 4 examples of intravenous antibiotics?
- propofol
- thiopental
- etomidate
- ketamine
What is the mechanism of action of propofol?
Potentiates GABA-A
What are 2 adverse effects of propofol?
- pain on injection - activation of pain receptor TRPA1
- hypotension
What are 2 situations when propofol is used?
- common induction agent
- used extensively in intensive care for ventilated patients
What is an additional effect, as well as being an anaesthetic agent, of propofol?
anti-emetic effects (useful in post-operative vomiting)
What is the mechanism of thiopental?
type of barbiturate - potentiates GABA-A
What is a side-effect of thiopental?
laryngospasm
Why does thiopental affect the brain quickly?
highly lipid-soluble
What is the mechanism of action of etomidate?
potentiates GABA-A
What are 2 adverse effects of etomidate?
- primary adrenal suppression (seoncdary to reversibly inhibiting 11β-hydroxylase)
- myoclonus
In which specific situation may etomidate be the induction agent of choice and why?
in cases of haemodynamic instability - causes less hypotension that propofol and thiopental during induction
What is the mechanism of action of ketamine?
blocks NMDA receptors
What are 2 adverse effects of ketamine?
disorientation
hallucinations
In what situation may ketamine be a useful anaesthetic / analgesic and why?
trauma - doesn’t cause a drop in blood pressure
What counts as clear fluids pre-op?
water, juice with no bits, coffee/tea without milk, ice lollies
What is the guidance for adjustments to metformin on for patients undergoing surgery?
- day prior to admission - take as normal
- day of surgery, morning op - if OD or BD take as normal, if TDS omit lunchtime dose
- day of surgery, afternoon op - if OD or BD take as normal, if TDS omit lunchtime dose
What is the guidance for adjustments to sulphonylureas on the day of surgery?
- day prior - take as normal
- day of surgery for morning op - if taken OD in morning, omit dose. if BD - omit morning dose
- dy of surgery for afternoon op - if OD in morning, omit dose. if BD omit both doses that day
What is adjustment to be made to DPP4 inhibitors (gliptins) in patients undergoing surgery?
- day before - take as normal
- day of (morning op) - take as normal
- day of (pm op) - take as normal
What is adjustment to be made to GLP1 analogues (e.g. exenatide) in patients undergoing surgery?
- day before - take as normal
- day of (morning op) - take as normal
- day of (pm op) - take as normal
What is adjustment to be made to SGLT2i drugs (-flozins) in patients undergoing surgery?
- day before - take as normal
- day of (morning op) - omit on day of surgery
- day of (pm op) - omit on day of surgery
What adjustments should be made to twice daily biphasic or ultra-long acting insulins e.g. Novomix 30, Humulin M3 in patients having surgery?
- day before: no dose change
- day of (am op): halve morning dose, evening dose as normal
- day of (pm op): halve morning dose, evening dose as normal
What special preparation is required for thyroid surgery?
vocal cord check
What special preparation is required for parathyroid surgery?
consider methylene blue to identify gland
What special preparation is required for sentinel node biopsy?
radioactive marker / patent blue dye
What special preparation is required for surgery involving the thoracic duct ?
consider administration of cream
What special preparation is required for phaeochromocytoma surgery?
alpha and beta blockade
What special preparation is required for carcinoid tumour surgery?
octreotide cover
What special preparation is required for colorectal surgery?
bowel prep (esp L sided surgery)
What special preparation is required for patients with thyrotoxicosis undergoing surgery?
lugols iodine/medical therapy
What is the commonest reason for desaturation after intubation?
oesophageal intubation
How does malignant hyperthermia present?
- increased end-tidal CO2
- increased body temperature, diaphoresis
- sustained muscular contraction and rhabdomyolysis
- metabolic acidosis
What is the dose of adrenaline for anaphylaxis < 6 months?
100 - 150 micrograms (0.1 - 0.15 ml 1 in 1000)
What is the dose of adrenaline for anaphylaxis 6 months - 6 years?
150 micrograms (0.15 ml 1 in 1000)
What is the dose of adrenaline for anaphylaxis in children 6 - 12 years?
300 micrograms (0.3 ml 1 in 1000)
What is the dose of adrenaline for anaphylaxis in an adult and child > 12 years?
500 micrograms (0.5 ml 1 in 1000)
What adjustments should be made to once daily insulins e.g. Lantus, Levemir in patients having surgery?
- day before: reduce dose by 20%
- day of surgery (am op): reduce dose by 20%
- day of surgery (pm op): reduce dose by 20%
