Inhalational Anesthetics; Nitrous Oxide and Halothane.pptx

All details about N2O and Halothane volatile anesthetic, their physical properties , their anesthetic effect on human body systems, also the indications and the history, the complications and contraindications, the metabolism.
How supplied ? Types of vaporizers, old and modern.

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

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

3. Safe ?, weak anesthetic but good analgesic. No toxicity to Heart, Liver, Kidneys. Prolong exposure to N 2 O → 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 N 2 O via alveolus is so rapid, this hypoxia can be prevented by administration of 100% O 2 for 5-10 minute after discontinuing N 2 O.

7. Cerebral: CBF ↑,CBV↑, ICP↑(mild), CMRO 2 ↑. 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 T hymol preservative does not readily evaporate, and therefore builds up in the vaporizer, which requires drainage and cleaning at regular intervals.

14. S lightly 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 . V ictor Goldman (1903b. – 1994d). t ow 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. TEC 2 Cyprane Fluotec Vaporizer

18. TEC 3 Cyprane Fluotec Vaporizer (out of circuit)

19. Accoma / Halothane Vaporizer made in Japan 1980s

20. Datex - Ohmeda TEC 3 (within the circuit ) Halothane Vaporizer

21. Ohmeda Fluotec4/ Halothane Vaporizer

22. Datex Ohmeda Fluotec5/ Halothane Vaporizer

23. Dräger V apor 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 O 2 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 ↓ → ↑ PaCO 2 . •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).