General Anesthetics Flashcards
what are general anesthetics (GA)?
drugs that produce unconsciousness and lack of responsiveness to all painful stimuli
what are the two groups GA can be separated into?
- inhalent anesthetics
- IV anesthetics
what is the definition of analgesia?
loss of sensibility of pain
what is the definition of anesthesia?
refers to not only the loss of pain, but to the loss of all sensations and consciousness
what would the properties be if an ideal anesthetic existed?
-unconsciousness
- analgesia
- muscle relaxation
- amnesia
- adverse effects would be minimal
DOES NOT EXIST
what is balanced anesthesia?
combining drugs to accomplish what we cannot achieve with an inhalation anesthetic alone
what are the common drugs that are combined to make the ideal anesthesia?
- propofol and short-acting barbiturates
- neuromuscular blocking agents
- opioids and nitrous oxide
what is the action of inhalant anesthetics?
enhance transmission at inhibitory synapses and by depressing transmission at excitatory synapses
what is the action of nitrous oxide?
enhances GABA receptors
what is the definition of minimum alveolar concentration (MAC)?
the minimum concentration of drug in alveolar air that will produce immobility in 50% of patients exposed to painful stimulus
what does the MAC tell us?
approx. how much anesthesic the inspired air must contain to produce anesthesia
what does a low MAC indicate?
high anesthetic potency
in order to produce GA in all patients - what must the inspired anesthetic concentration be?
1.2-1.5 times the MAC
what are the principal determinants of anesthetic concentration?
- uptake from the lungs
- distribution to the CNS and other tissues
what are factors that determine the anesthetic uptake?
- amount inspired
- pulmonary ventilation
- solubility of the anesthetic in blood
- blood flow through the lungs
what is distribution determined by?
regional blood flow
in what tissues does anesthesia rapidly rise in?
brain, kidney, liver, and heart - tissues that receive the greatest amount of blood
in what tissues is anesthesia distribution slower?
- skin and skeletal muscle
- fat, bone, ligaments
where are inhaled anesthetics generally eliminated?
in the lungs…
what same factors that influence uptake also influence _____?
elimination
why does anesthesia leave the brain the fastest after administration has stopped?
because blood flow is high here - brain will wake before body
what are 6 adverse effects of GA?
- respiratory and cardiac depression
- sensitization of the heart to catecholamines
- malignant hyperthermia
- aspiration of gastric contents
- hepatotoxicity
- toxicity to operating room personel
what do almost all patients require when under GA d/t resp depression?
to be ventilated
what is malignant hyperthermia?
- rare
- muscle rigidity and a profound elevation of temp
what can trigger malignant hyperthermia?
succinylcholine - a neuromuscular blocker
why does aspiration of gastric contents happen?
reflex that usually prevents this is absent
what can aspiration of gastric contents cause?
bronchospasm and pneumonia
what might be needed for aspiration?
endotracheal tube
what are reactions of toxicity of OR personel?
headache, reduced alertness, and spontaneous abortion
what drugs results in decreased anesthetic dosage?
opioids
what drugs result in an increased anesthetic dosage?
CNS stimulants
what are 3 reasons preanesthetic medications are administered?
- reducing anxiety
- producing preoperative amnesia
- relieving pre/postoperative pain
what are alpha adrenergic agonists given for?
adjuncts to anesthesia - both produce effects in the CNS
what are anticholinergic drugs given for?
dec. the risk of bradycardia during surgery
what are neuromuscular blocking agents given for?
relaxing skeletal muscle
why are antiemetic given postoperatively?
may have some nausea as recovering from anesthesia
why are muscarinic agonists given after surgery?
abdominal distention and urinary retention are possible post-operative complications
who are the only two people who can do the dosing and administration of anesthetics?
anesthesiologist (physician), anesthetist (nurse)
what are the two type of inhalation anesthetics?
gases and volatile liquids
what are gases?
exist in gaseous state at atmospheric pressure
what are volatile liquids?
exist in liquid form at atmospheric pressure but can easily be volatilized (turned to vapour)
what is isoflurane?
- volatile inhalation
- high potency
- emerge rapidly
- respiratory irritant
when do patients awake after ceasing isoflurane?
approx 20 min
what is requires with isoflurane?
a strong analgesic and other muscle relaxant drug
what might isoflurane inhibit during labour?
uterine contractions
what are adverse effects of isoflurane?
- hypotension
- resp depression
what is nitrous oxide?
- “laughing gas”
- volatile liquid
- high anesthetic potency
is nitrous oxide ever employed as a primary anesthetic?
NO - impossible to produce surgical anesthesia alone
why is nitrous oxide given?
to supplement the analgesic effects of the primary anesthetic
what are adverse effects of nitrous oxide?
there are none - cannot cause CNS depression
when are IV anesthetics used?
alone or to supplement an inhalent
what is benzodiazepine used for?
to reduce anxiety and promote amnesia
what is midazolam used for?
- induction of anesthesia and to produce conscious sedation
when used for induction, what is midazolam commonly combined with?
barbiturate
- unconscious in 80 sec
what is propofol?
- most widely ised IV anesthetic
- indicated for induction and maintenance of GA as part of balanced anesthesia technique
what does propofol promote the release of?
GABA
what is the onset of propofol?
less than 60 sec
what is the duration of propofol?
3-5 mins
how can extended sedation for propofol be achieved?
a continuous low-dose, not exceeding 4mg/kg/hour
what does propofol put the patient at high risk for?
bacterial infections
when are preoperative meds given?
30-60 mins before surgery
what are nursing implications for preoperative meds?
- calm patient
- provide analgesia
- counteract adverse effects of general analgesia
what are nursing implications for postoperative patients?
- know what frug they have been given in hospital
- know what drugs they are taking at home
