Chapter 30 - General Anaesthetics Flashcards
What do general anaesthetics do?
-produce unconsciousness
-lack of pain response
How are general anaesthetics administered?
-inhalation
-intravenous
What is balanced anaesthesia?
a technique used to compensate for an ideal anesthetic that uses a combo of drugs
Goals of Balanced Anaesthesia:
-smooth induction
-rapid analgesia
-muscle relaxation
What inhaled drugs make up balanced anaesthesia?
-propofol
-NM blocking agents
-opioids
-nitrous oxide
Transmission is enhanced at ____________ synapses
inhibitory
Transmission is depressed at ______________ synapses
excitatory
All agents used today enhance activation of GABA receptors except…
nitrous oxide
What is the minimum alveolar concentration (MAC)?
the minimum concentration of drug in the alveolar air that will produce immobility in 50% of patients exposed to pain
Low MAC = _______ anaesthetic potency
high
Uptake of Inhaled Anaesthetics
in the lungs, greater concentration = more rapid uptake
What determines distribution of inhaled anaesthetics?
regional blood flow
What are the areas of fastest uptake?
-brain
-kidney
-heart
How are inhaled anaesthetics eliminated?
in expired breath via lungs
What are the adverse effects of inhaled anaesthetics?
-respiratory and cardiac depression
-dysrhythmias (sensitization to catecholamines)
-malignant hyperthermia
-aspiration of gastric contents (USE ET TUBE!!!)
-hepatotoxicity
Why are pre-anaesthetic medications given?
given to reduce anxiety, produce pre-op amnesia, relieve post-op pain
What are pre-anaesthetic benzodiazepines used for?
reduce anxiety and produce amnesia
What are pre-anaesthetic opioids used for?
pain and cough reduction
What are pre-anaesthetic clonidine used for?
used for hypertension
What are pre-anaesthetic anti-cholinergics used for?
decrease risk of bradycardia
What are some neuromuscular blocking agents?
succinylcholine and pancuronium
What are neuromuscular blocking agents used for?
reduce amount of anaesthesia needed and prevent skeletal muscle contraction
What medications are given post-anaesthesia?
-analgesics
-antiemetics
-muscarinic antagonists
What are post-anaesthetic analgesics used for?
pain relief (mild - acetaminophen and severe - opioids)
What are post-anaesthetic antiemetics?
-ondansetron
-promethazine
-droperidol
What are post-anaesthetic muscarinic antagonists used for?
bethanechol - abdominal distension and urinary retention
Properties of sevoflurance
rapid induction and recovery
Nitrous oxide aka
laughing gas
What is the prototype of the volatile inhalation anaesthetics?
isoflurane
Properties of isoflurane:
-rapid action
-depth can be raised or lowered easily
-weak analgesic
-inadequate muscle relaxation for surgery
Isoflurane induction is produced with __________
propofol
What drug must be added to isoflurane to improve muscle relaxation for surgery?
pancuronium
What are the adverse effects of isoflurance?
-hypotension
-respiratory depression
-nausea
-vomiting
-decreased urine output
Nitrous oxide has a _____ anaesthetic potency and a _____ analgesic potency
low; high
What is nitrous oxide never used as?
a primary anaesthetic
___% nitrous oxide gives equal pain relief to morphine
20
What are the side effects of nitrous oxide?
nausea and vomiting
Name the IV anaesthetics:
-short-acting barbiturates
-benzodiazepines
-propofol
-etomidate
-ketamine
The neuroleptic-opioid combination is…
droperidol and fentanyl
Thiopental properties:
-rapid onset
-slow recovery
-CV and respiratory depression
-pain with injection
Etomidate properties:
-rapid onset
-fast recovery
-excitatory effects during induction
-adrenocortical suppression
-less CV and resp depression
-injection site pain
Propofol properties:
-rapid onset
-very rapid recovery
-CV and resp depression
-injection pain
What is the most common induction agent?
Propofol
Ketamine properties:
-slow onset
-post-anaesthetic effects
-psychomimetic effects
-N&V
-no injection pain
What is the primary use of benzodiazepines?
IV induction of anaesthesia
Properties of diazepam?
-loc in 1 min
-little muscle relaxation
Properties of Midazolam:
-unconsciousness in 80s
-dangerous cardiorespiratory effects
When does unconsciousness develop and last with propofol?
develops in 60s and lasts 3-5 mins
What is propofol used for?
induction and maintenance of analgesia
What are the adverse effects of propofol?
-respiratory depression
-hypotension
-risk of bacterial infection
-abuse
What is etomidate?
a potent hypnotic agent
What is etomidate used for?
induction
What are adverse effects of repeated etomidate use?
-hypotension
-oliguria
-electrolyte disturbances
-N&V
What is the preferred drug for patients with CV disorders?
etomidate
What are the effects of Ketamine?
-dissociative anaesthesia
-sedation
-immobility
-analgesia
-amnesia
What are the adverse effects of ketamine?
-hallucinations
-disturbing dreams
-delirium
What is ketamine used for?
young children with minor procedures
What environment should ketamine be used in?
a soothing environment
