Induction and Maintenance of Anaesthesia Flashcards
(43 cards)
Name the 5 routes of drug administration/delivery
IM
IV
SC
Inhaled
Across mucous membranes
Name the 3 things that general anaesthesia includes
- Amnesia
- Loss of consciousness (hypnosis)
- Immobility, often associated with analgesia and suppression of autonomic reflexes
Name the main pharmacokinetic properties of propofol (absorption, solubility, distribution, metabolism, elimination)
Absorption - minimal oral bioavailability therefore inject IV
Solubility - Minimally soluble in water therefore injected as an emulsion
Distribution - 98% protein bound
Metabolism - liver, process of glucuronidation
Elimination - renal
Name the main pharmacodynamic properties of propofol
Anaesthesia in 5-8 mins
Respiratory and cardiovascular depression
Decreased cerebral metabolic rate of oxygen (CMRO2)
Haemodynamic effects due to sympathetic depression
- Decreased HR, MAP, SVR and CVP
- Stable cardiac output
Why do we need to intubate ASAP when using propofol
Apnoea is common
Name the main pharmacokinetic properties of alfaxalone (absorption, solubility, distribution, metabolism, elimination)
Absorption - good bioavailability
Solubility - soluble in water - can give IM or IV
Distribution - 30-50% protein bound
Metabolism - liver, rapid (also lungs and kidney)
Elimination - renal (small % bile)
Name the main pharmacodynamic properties of alfaxalone
Anaesthesia
Decreased cerebral metabolic rate of oxygen (CMRO2)
Haemodynamic effects minimal
- Stable cardiac output
- Stable HR, MAP, SVR, CVP
How should you administer alfaxalone and propofol
Titrate to effect - over 60 seconds
What are the haemodynamic effects of ketamine
Minimal
Stable cardiac output
Increased HR, MAP, SVR, CVP
What effects does ketamine have on the cardiovascular system, and what patients is it contraindicated in
Increases arterial pressure, HR and cardiac output - due to stimulation of SNS
Increases pulmonary arterial pressure
Contraindicated in patients with coronary artery disease and poorly controlled hypertension
What effects does ketamine have on the respiratory system
Minimal effect on ventilatory drive
Bronchodilator - preserves upper airway reflexes
Patients with an increased risk of aspiration may require airway protection
What effects does ketamine have on the cerebral system
Increased cerebral blood flow, intracranial pressure and cerebral oxygen requirements
Dissociative anaesthesia - patent may appear conscious e.g. eye-opening, swallowing
Analgesia and opioid sparing
Which drug can you use to minimise the unpleasant dream/hallucinations following administration of ketamine
Benzodiazepines
Name the main pharmacokinetic properties of ketamine (availability, solubility, distribution, metabolism, elimination)
Availability - Good bioavailability - IV, IM, squirted into mouth
Solubility - soluble in water
Distribution - 12% protein bound
Metabolism - liver => norketamine
Elimination - renal, small % bile
Name the 2 main volatile agents used in maintenance of anaesthesia
Isofluorane
Sevofluorane
Name the main pharmacodynamic properties of volatile agents
Anaesthesia
Cardiopulmonary depression
- Reduced cardiac output, HR, MAP, SVR, CVP
Name the main pharmacokinetic properties of the volatile agents (absorption, solubility, distribution, metabolism, elimination)
Absorption - lungs
Solubility - in tissues/blood varies
Distribution - Via blood to brain
Metabolism - minimal
Elimination - lungs
How is the speed of induction with volatile agents related to cardiac output and why
Speed of induction is inversely proportional to cardiac output
Due to negative effects of cardiac output on alveolar partial pressure
Name 3 ways anaesthesia can be maintained
- Inhalational anaesthesia
- Total intravenous anaesthesia (TIVA)
- Mix of the two - Partial intravenous anaesthesia (PIVA)
Are volatile/inhalational agents vapours or gasses
Vapours
Which gasses can be used to carry volatile agents to the patient
Oxygen - most common
Medical air?
May include NO
How do inhalational agents work (cause anaesthesia)
Fresh gas + volatile agent are inhaled => alveoli
The agent is soluble in blood, plasma conc. increases
Agent => brain
What factors does the rate of plasma increase of volatile agents depend on and how
The concentration of the agent
- Increase in conc => quicker increase of plasma conc.
Patient’s ventilation
- Increased ventilation => faster increase in plasma conc.
Cardiac output
- Increased CO => slower increase
Solubility of the agent in the blood
- increased solubility => slower increase
- Poorly soluble agents diffuse out of blood to tissues more quickly
What 3 receptors do we think volatile agents act on
- GABA
- NMDA
- Ach
