1.
Inhalational Anesthetics
Nitrous Oxide , Halothane
Mahmood Hasan Taha
H.D Anesthesia
Zakho General H.
Aug 2022

2.
Nitrous Oxide (N2O), Laugh Gas
• Clear, colorless, non explosive , non flammable.
• Supplied by pipeline or pressurized cylinders.
• Boiling point -89ċ.
• Gas at room temperature.
• ≈ 5 times more rapid diffusion than N2.
• Inexpensive.!!

3.
• Safe ?, weak anesthetic but good analgesic.
• No toxicity to Heart, Liver, Kidneys.
• Prolong exposure to N2O → bone marrow
depression (megaloblastic anemia) &
peripheral neuropathies.
• Teratogenic after long term uses.
• MAC = 105

4.
Effects on organ systems

5.
Cardiovascular:
• Minimal tendency to
sympathetic stimulation.
• Myocardial depression:
caution in IHD & sever hypovolemia.
• B.P, COP & HR unchanged or slightly
increased.

6.
Respiratory:
• RR ↑
• Vt ↓
• Vm (-)
• Diffusional hypoxia during recovery d.t
elimination of N2O via alveolus is so rapid, this
hypoxia can be prevented by administration of
100% O2 for 5-10 minute after discontinuing
N2O.

7.
Cerebral:
• CBF ↑,CBV↑,ICP↑(mild), CMRO2 ↑.
Renal:
• GFR ↓ ,UOP ↓.
Liver:
• HBF ↓ < other volatile Anesthetics.
Gastrointestinal:
• PONV ↑
Neuromuscular:
• ↑ potency of non depolarizing NMBA.

8.
Contraindications:
• Space occupying gas
Brain? , Lung? , GIT? , ETT ?
Pneumothorax, bullae, small bowel obstruction,
middle ear surgery.

9.
• Metabolism: 0.004%.
• 70% nitrous oxide for >2hours have
been shown to have more postoperative
complications: atelectasis, fever, pneumonia,
and wound infections.
_______________

10.
Halothane (Fluothane) 1956

11.
General Description:
• Non flammable.
• Non explosive.
• Potent anesthetic.
• Induction is pleasant.
• Recovery delayed.
• Shivering is common.

12.
• Malignant hyperthermia & hepatitis ?
• Rarely used nowadays.
• MAC = 0.75
• Blood/ Gas: 2.3, Oil/ Gas: 224
• Boiling point 50.2℃, SVP 32.5 mmHg.
• Color code: red.
• Clear, colorless liquid in brown glass bottle.

13.
• 0.1% Thymol as preservative to protect against
decomposition by light.
• The Thymol preservative does not readily
evaporate, and therefore builds up in the
vaporizer, which requires drainage and
cleaning at regular intervals.

14.
• Slightly water soluble.
• Soda lime: compatible.
• Halothane may corrode or tarnish most metals:
with the exception of chromium , nickel and
titanium; Halothane attacks aluminum, tin, lead,
magnesium, brass and solder alloys in the presence
of water; this contact causes rubber and some
plastic materials to deteriorate rapidly.

15.
• Suitable vaporizer:
Old design: Goldman vaporizers.
• Designed by an English physician Dr. Victor Goldman
(1903b. – 1994d). tow models: 1956 - 1962.
Modern and New design:
a specifically calibrated plenum vaporizers e.g:
(TEC3,4,5&7, Dräger Vapor, Penlon, Blease).
The term plenum= pressurized chamber in which the
FGF is above atmospheric pressure.

16.
Goldman vaporizer (made in England)

17.
TEC2 Cyprane Fluotec Vaporizer

18.
TEC3 Cyprane Fluotec Vaporizer (out of circuit)

19.
Accoma / Halothane Vaporizer
made in Japan 1980s

20.
Datex - Ohmeda TEC3(within the circuit) Halothane Vaporizer

21.
Ohmeda Fluotec4/ Halothane Vaporizer

22.
Datex Ohmeda Fluotec5/ Halothane Vaporizer

23.
Dräger Vapor 19.1 / Halothane Vaporizer

24.
Dräger Vapor 2000 – Halothane Vaporizer

25.
Dräger Vapor 3000 – Halothane Vaporizer

26.
Penlon, Sigma Delta – Halothane Vaporizer

27.
Blease- Datum- Halothane Vaporizer

28.
Datex - Omeda Tec7/ Halothane Vaporizer

29.
Effects on organ systems

30.
Cardiovascular:
• Myocardial depression,
COP ↓.
• B.P ↓↓ → HR ↓.
• At 2 MAC of Halothane
without surgery, 50% reduction in COP & B.P.

31.
• Coronary vasodilatation but coronary Blood
flow reduced d.t. ↓ in MAP.
• Adequate myocardial perfusion is usually
maintained d.t ↓ in O2 consumption (↓
demand).

32.
• Halothane sensitizes the heart to
arrhythmogenic effect of epinephrine
(epinephrine > 1.5 mcg/kg should be avoided).

33.
Lidocaine HCl 2% with Epinephrine
20mg/10mcg per mL

34.
Carpules cartridge syringe

35.
Respiratory:
•Non irritant.
•Rapid, shallow breathing
( Vt ↓ , RR ↑).
•Vm ↓ → ↑ PaCO2.
•Apneic threshold ↑.
•Good bronchodilator → safe in asthma.
•Mucociliary function ↓ → post operative
atelectasis & hypoxia.

36.
Neuromuscular:
• Adequate M.R for intubation of a child.
• potentiate the non depolarizing (NMBA) action.
• Malignant hyperthermia triggering.

37.
Renal:
RBF ↓, GFR↓ , UOP↓.

38.
Liver:
• HBF↓↓.
• Halothane hepatitis:
Extremely rare (1 : 35000).
Multiple exposure at short interval.
Middle age obese females.
Family history.
Personal history.
Avoidance??

39.
Uterus:
Uterine relaxation.
Others:
Postoperative shivering is common.

40.
Contraindications:
• History of unexplained liver dysfunction,
jaundice following prior administration.
• Risk of triggering malignant hyperthermia.
• With caution in neurosurgical procedure d.t ↑
ICP or ↑ CBF.
• Hypovolemic patient or sever left ventricular
failure.
• With exogenous epinephrine or with pheochrom-
ocytoma.

41.
Drug Interaction:
• Myocardial depression ↑↑ with B-blockers &
Ca++ blockers.
• Tricyclic antidep. & MAOI → ↑↓ (fluctuation)
B.P & arrhythmias.
• Halothane + aminophylline → serious
ventricular arrhythmias.

42.
Metabolism and elimination:
• 60 -80 % unchanged via lungs.
• 20% metabolized in liver (metabolites
excreted in urine for several weeks).