At rest what 2 factors are balanced in brain consciousness?
Excitation through glutamate (NMDA receptors) and inhibition through NMDA (NMDA receptors).
What parts of the brain are targeted by anaesthesia and what is this group of parts called?
Hindbrain, midbrain and thalamus (the reticular formation).
What is the function of GABA receptors? Which anaesthetics interact with GABA receptors? Which anaesthetics don’t interact with GABA receptors, and what do they interact with?
GABA receptors are ligand gated ion channels which, upon binding with GABA, allow negative chloride ions across to inside the membrane hyper polarising it and making it more difficult to excite, depressing areas of the brain. Xenon, NO, Ketamine, which react with NMDA receptors.
What are the 3 main IV (general) anaesthetics? What are their common side effects?
Propofol, barbiturates, ketamine. Nausea and vomiting. Hypotension. Post operative cognitive dysfunction (older patients). Chest infection.
When are local and regional anaesthetics used?
Dentistry, obstetrics, regional surgery, post-op wound pain, chronic pain management.
What are the steps of anaesthesia for procedures?
Premedication - Hypnotic e.g. benzodiazepine. Induction - IV normally with barbiturate or inhalation. Intraoperative analgesic - opioid Muscle paralysis - allows incubation/ventilation/stillness Maintenance - IV and/or inhalation Muscle-paralysis reversal/anaelgesia/recovery - opiod/NSAID/paracetamol/antiemetic
What are Guedel’s stages of anaesthesia?
What 4 things are lost with increased concentrations of anaesthetics? In what order are they lost?
How is the potency of volatile anaesthetics measured?
Minimum Alveolar Concentration - the alveolar concentration at which 50% of subjects fail to move after surgical stimulus.
What makes up a regional anaesthetic? Name some types of block commonly used? How is it used for labour?
A local and/or opioid used to ‘block’ a nerve. Axillary, supreclavicular, femoral, sciatic etc (any major nerve). Extradural (around the spinal cord)/intrathecal (inside the meninges)/combined.
Give 4 examples of local anaesthetics. What is their mechanism of action? 3 indications? 1 contraindications? 2 ADRs? What increases the duration of these analgesics?
Lidocaine, bupivacaine, ropivacaine, procaine. MoA - Is absorbed into and blocks voltage gates Na2+ channels blocking small myelinated afferent nerves. The more the nerve fires, the more the channels will open and will be blocked, so these are use dependant. Indications - Contraindications - ADRs - Problems if they become systemic. Adrenaline increase duration.
Give 2 examples of volatile anaesthetics. 1 indication? 2 contraindications? 2 ADRs?
Nitrous oxide, isoflurane. Indications - maintenance of analgesia (NO must be combined with other anaesthetics) Contraindications - pneumothorax (NO), susceptibility to malignant hypothermia (isoflurane) ADRs - Bone marrow suppression (NO), hypotension though decreased systemic vascular resistance.