Introduction to Anaesthetics - Lecture Flashcards
What are the 3 types of anaesthesia and what do they do?
- General anaesthesia = total loss of sensation.
- Regional anaesthesia = loss of sensation to a region or part of body.
- Local anaesthesia = topical.
Define:
- Amnesia
- Analgesia
- Akinesis
- Lack of response and recall to noxious stimuli - unconsciousness.
- Pain relief.
- Immobilisation / paralysis.
What do you need for general anaesthesia?
- Monitoring
- IV access
- Start the process - induction of anaesthesia + start analgesia and muscle relaxation.
- Maintain the process - maintenance agents + replace fluid loss blood loss.
- Reverse muscle relaxation.
What is the best induction agent for:
- Burn dressing change?
- Arm operation under GA with an LMA?
- Hx of HF + requires GA?
- Intestinal obstruction + requires emergency laparotomy?
- Porphyria + needs inguinal hernia repair?
- Ketamine - short procedure.
- Propofol - commonly used.
- Etomidate - haemodynamic stability (steady blood flow).
- Thiopentone - RSI.
- Porphyria - NOT thiopentone.
- What are the positives of using propofol.
2. What dose is used?
- Excellent suppression of airway reflexes + decreases incidence of PONV.
- Dose = 1.5 - 2.5 mg/kg
What are the unwanted effects of propofol?
- Marked drop in HR and BP.
- Pain on injection.
- Causes involuntary movements.
- What are positives of using thiopentone?
2. What dose is used?
- Faster than propofol - used for rapid sequence induction.
- Antiepileptic properties + protects brain.
- Dose = 4 - 5 mg/kg
What are the unwanted effects of thiopentone?
- Drops BP but raises HR.
- Rash
- Bronchospasm
- Intra-arterial injection = can cause thrombosis and gangrene.
- Contraindicated in porphyria.
- When is ketamine used and what are the positives?
- What is the dose?
- How long does it take to act?
- Sole anaesthetic for short procedures.
- Raise HR/BP
- Bronchodilation
- Dose = 1 - 1.5 mg/kg
- Slow = 90 seconds.
What are the unwanted effects of ketamine?
- N&V
2. Emergence phenomenon.
What is emergence phenomenon?
Hallucinations, vivid dreams, illusions - basically, px trips out when coming around from anaesthesia.
What are the positives of etomidate and what is the dose?
- Rapid onset
- Haemodynamic stability - good for HF px
- Lowest incidence of hypersensitivity reaction.
- Dose = 0.3 mg/kg
What are the unwanted effects of etomidate?
- Pain on injection.
- Spontaneous movements.
- Adreno-cortical suppression.
- High incidence of PONV.
How long do induction agents last for?
4 - 10 minutes
What can be used to maintain amnesia?
- Propofol infusion - total intravenous anaesthesia.
2. Inhalation agents = sevoflurane, desflurane, isoflurane, enflurane.
What is MAC?
Minimum alveolar concentration - the concentration of vapour required, to prevent the reaction to a surgical stimulus, in 50% of px.
What are the MAC values for:
- Nitrous oxide
- Sevoflurane
- Desflurane
- Isoflurane
- Enflurane
- 104%
- 2%
- 6%
- 1.15%
- 1.6%
Best inhalation agent for:
- Long, 8 hour, finger re-implantation.
- Chubby child with no IV access.
- Organ retrieval from a donor.
- Desflurane - low lipid solubility + used for long operations.
- Sevoflurane
- Isoflurane - least effect on organ blood flow.
What are analgesics required for?
Intubation, insertion of LMA, intra-operative pain relief and postoperative pain relief.
- What short-acting opioids are used?
2. What long-acting opioids are used?
- Fentanyl, alfentanil, remifentanil.
2. Morphine, oxycodone
What other analgesics are used?
- Paracetamol IV
- NSAIDS = Diclofenac, Parecoxib, Ketorolac
Most commonly used analgesic?
Paracetamol
Most commonly used oral opioid in adults?
Codeine
IV NSAIDS?
Ketorlac, Parecoxib
Name the only depolarising muscle relxant and what is its dose?
Suxamethonium - RSI
Dose = 1 -1.5 mg/kg
What are the adverse effects of suxamethonium?
Muscle pains, fasciculations, hyperkalemia, malignant hyperthermia, rise in IOP/ICP
How do non-depolarising muscle relaxants work?
Compete with acetylcholine for nicotinic receptors.
What is the difference between suxamethonium and non-depolarising muscle relaxants?
Sux = rapid onset and rapid offset (RSI) + lots of side effects.
Non = slow onset and variable duration + less side effects.
What can be used to reverse the effects of atracurium?
Neostigmine or Glycopyrrolate.
What drugs are commonly used to treat hypotension whilst px is undergoing surgery?
- Ephedrine
- Phenylephrine
- Metaraminol
(Vaso-active drugs)
How does ephedrine work?
Acts directly and indirectly on alpha and beta receptors (adrenergic receptors) - causing vasoconstriction.
Increasing HR and contractility = rise in BP.
How does phenylephrine / meteraminol work?
Causes vasoconstriction - direct action on alpha receptors.
Drops HR.
Best vaso-active agent for:
- Low BP, low HR
- Low BP, high HR
- ICU / severe sepsis
- Ephedrine
- Phenylephrine / Metaraminol
- Noradrenaline / Adrenaline
What % of px get PONV after GA?
20-30%
Name the commonly used anti-emetic agents and what class of drug?
- 5HT3 blocker = Ondansetron
- Anti-histamine = Cyclizine
- Steroid = Dexamethasone
- Phenothiazine = Prochlorperazine (Stemetil)
- Anti-dopaminergic = Metoclopramide
What are the 4 steps to reversal of GA?
- Stop anaesthetic vapours
- Give o2
- Perform throat suction
- Give reversal muscle relaxant
How does neostigmine work?
Anti-cholinesterase = prevents breakdown of acetylcholine
