Inhalant anesthesia 1 & 2 Flashcards
What is Dalton’s law of partial pressure
total pressure of a gas mix is equal to sum of partial pressure of the individual gases
solubility
expressed as a partition coefficient describes capacity of a given solvent to dissolve anesthetic gas
What is blood-gas partition coefficient
describes amt of anesthetic in blood vs. alveolar gas at equal partial pressures
What is the significance of knowing the amount of alveolar gas
the anesthetic in alveolar gas represents brain concentration this is location of effect anesthetic dissolved in blood is pharmacologically inactive!
How to incr alveolar delivery of anesthetic gas
Incr inspired anesthetic concentration:
- incr vaporizer setting
- incr fresh gas flow
Incr alveolar ventilation:
- incr minute ventilation
how to decrease removal of anes gas from alveoli
decr blood solubility of anesthetic
What is Minimum Alveolar Concentration (MAC)
Minimum alveolar concentration of an anesthetic that prevents movement in 50% of pts exposed to a noxious stimulus
What ensures immobility in 95% of patients
1.2-1.4 x MAC
Example: 1.2MAC of iso = 1.2 x 1.3 = 1.6%
What are CV effects of inhalants
Decrease:
CO
BP
SVR
Contractility (inotropy)
No change or Increase:
HR (chronotropy)
What are respiratory effects of inhalants
Decrease ventilation
Bronchodilation
irritating odor: desflurane & iso
least irritating odor: sevo
What are neurologic effects of inhalants
Incr ICP @ >1 MAC (incr cerebral blood flow)
Decr cerebral metabolic rate
acts on brain & SC to produce immobility (not analgesia)
suppress seizure activity (except Enflurane)
What are renal effects of inhalants
Decr GFR & renal blood flow
Renal failure (methoxyflurane)
what is Compound A
Produced from sevoflurane breakdown in CO2 absorbent (baralyme > soda lime)
Nephrotoxic in rats
What are hepatic effects of inhalants
decr liver blood flow & O2 delivery (related to decr CO)
Halothane can cause hepatotoxicity 2 types:
incr liv enzymes (mild, self limiting)
Halothane hepatitis = immune mediated often fatal
What inhalant can cause malignant hyperthermia
What spp most affected
Whats first sign
Tx
Px
occurance rate
Halothane
Pigs
Rapid incr in EtCO2
Dantrolene (muscle relaxant)
Poor-grave despite tx
extremely rare
What can be a consequence of N2O use
diffusion hypoxia when N2O d/c
prevent by providing 100% O2 for 5-10 minutes after stopping N2O
What are 3 anesthetic related common complication of inhalants
Hypotension
Hypoventilation
Hypothermia
What is considered hypotension in SA
LA
what is corresponding number on Dopper BP
MAP < 60 mmHg
MAO < 70 mmHg
80 or 90 respectively
What is the most appropriate & effective tx for hypotension during inhalant anesthesia
1 evaluate pt & turn down vaporizer if pt is too deep for current level of stimulation
if pt is light, add MAC sparing drug, then turn down vaporizer
What is considered hypventilation with inhalant anes
PaCO2 >40 mmHg OR EtCO2 >45 mmHG
What is appropriate tx for hypoventilation
1 evaluate pt & turn down vaporizer if pt too dep for curren level of stimulation
What is considered hypothermia during anesthesia
Temp < 97° F or 36° C
What is appropriate tx for hypothermia
Prevention is more effective than tx!
various ways:
BAIR hugger
bubble wrap feet
cover
warm water pad
etc.
What will a CO2 rebreathing waveform look like on capnograph
waveform does NOT return to baseline (0) between breaths