QUIZ - Volatiles ANZCA Exam
2025 Questions and Answers
Which compound(s) is/are broken down in soda-lime?
A. Nitrous oxide
B. Halothane
C. Sevoflurane
D. Desflurane
E. All of the above - ANSWER✔✔-E
Regarding nitrous oxide at 70%:
A. Synthetised from ? & N2 at 273C
B. Decreases muscle blood flow by 30%
C. Decreases cerebral autoregulation 24%
D. ?
COPYRIGHT © 2025 ALL RIGHTS RESERVED
,Nitrous oxide (N2O):
A. ?Increases/decreases CBF
B. Is an effective oxidant
C. Is made by heating nitrogen and oxygen in an iron retort
D. Decreases pulmonary artery pressure in neonates
Nitrous oxide at 70%
A. 99% equilibration at 3 minutes
B. About 10L uptake within first 3 minutes
C. Reduces muscle blood flow by 30%
D. Decreases cerebral autoregulation by 70%
E. ? - ANSWER✔✔-INO2
A - incorrect. "Manufactured by heating ammonium nitrate to 240 degrees celsius and
removing impurities... by passage through scrubbers and waters" (Yentis et. al.,
Anaesthesia and Intensive Care A-Z, 2004, p.371)
B - probably incorrect - "Nitrous oxide does not change SVR" (Stoelting 3rd ed p46)
C - ?correct. "increases cerebral blood flow and ICP slightly" (Yentis 2004, p.371, and
Stoelting), which indicates a decrease in autoregulation, but is it by 24%?!
COPYRIGHT © 2025 ALL RIGHTS RESERVED
, IN02b
A - correct if says INCREASES CBF, see answer for C IN02
B - Note the yellow warning sticker on the cylinder [1]
C - Incorrect, see answer A for IN02
D - Incorrect. NITRIC oxide is used to treat pulmonary hypertension, not nitrous oxide
IN02c Nitrous oxide at 70%
A. 99% equilibration at 3 minutes - incorrect; takes longer than this - Stoelting p27 '
Inhalation of a constant PI of nitrous oxide... for 10 minutes results in a PA that is >80%
of the PI).' Figure 1.18 indicates around 90% equilibtration at 3 mintues, 98% at 10
minutes.
B. About 10L uptake within first 3 minutes - Incorrect Stoelting p27 'up to 10 liters
during the first 10 to 15 minutes'.
C. Reduces muscle blood flow by 30%. - I think this is the only likely answer. Recall that
it has a muscle relaxant effect, reducing metabolic requirements thus vasoconstricting
via metabolic autoregulation.
D. Decreases cerebral autoregulation by 70% - Incorrect. Recall that this is 0.69 MAC -
CBF will be minimally altered.
The following drugs are (potent) triggers for malignant hyperthermia EXCEPT:
COPYRIGHT © 2025 ALL RIGHTS RESERVED
2025 Questions and Answers
Which compound(s) is/are broken down in soda-lime?
A. Nitrous oxide
B. Halothane
C. Sevoflurane
D. Desflurane
E. All of the above - ANSWER✔✔-E
Regarding nitrous oxide at 70%:
A. Synthetised from ? & N2 at 273C
B. Decreases muscle blood flow by 30%
C. Decreases cerebral autoregulation 24%
D. ?
COPYRIGHT © 2025 ALL RIGHTS RESERVED
,Nitrous oxide (N2O):
A. ?Increases/decreases CBF
B. Is an effective oxidant
C. Is made by heating nitrogen and oxygen in an iron retort
D. Decreases pulmonary artery pressure in neonates
Nitrous oxide at 70%
A. 99% equilibration at 3 minutes
B. About 10L uptake within first 3 minutes
C. Reduces muscle blood flow by 30%
D. Decreases cerebral autoregulation by 70%
E. ? - ANSWER✔✔-INO2
A - incorrect. "Manufactured by heating ammonium nitrate to 240 degrees celsius and
removing impurities... by passage through scrubbers and waters" (Yentis et. al.,
Anaesthesia and Intensive Care A-Z, 2004, p.371)
B - probably incorrect - "Nitrous oxide does not change SVR" (Stoelting 3rd ed p46)
C - ?correct. "increases cerebral blood flow and ICP slightly" (Yentis 2004, p.371, and
Stoelting), which indicates a decrease in autoregulation, but is it by 24%?!
COPYRIGHT © 2025 ALL RIGHTS RESERVED
, IN02b
A - correct if says INCREASES CBF, see answer for C IN02
B - Note the yellow warning sticker on the cylinder [1]
C - Incorrect, see answer A for IN02
D - Incorrect. NITRIC oxide is used to treat pulmonary hypertension, not nitrous oxide
IN02c Nitrous oxide at 70%
A. 99% equilibration at 3 minutes - incorrect; takes longer than this - Stoelting p27 '
Inhalation of a constant PI of nitrous oxide... for 10 minutes results in a PA that is >80%
of the PI).' Figure 1.18 indicates around 90% equilibtration at 3 mintues, 98% at 10
minutes.
B. About 10L uptake within first 3 minutes - Incorrect Stoelting p27 'up to 10 liters
during the first 10 to 15 minutes'.
C. Reduces muscle blood flow by 30%. - I think this is the only likely answer. Recall that
it has a muscle relaxant effect, reducing metabolic requirements thus vasoconstricting
via metabolic autoregulation.
D. Decreases cerebral autoregulation by 70% - Incorrect. Recall that this is 0.69 MAC -
CBF will be minimally altered.
The following drugs are (potent) triggers for malignant hyperthermia EXCEPT:
COPYRIGHT © 2025 ALL RIGHTS RESERVED
