Inhalational anesthetic agents
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Inhalational anesthetic agents

Inhalational anesthetic agents

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  • Alveolare concentration equilibirate more rapidly with inspired concentration. <br />
  • Decrease in tidal volume but increase in ventilatory rate (if opioids drugs are absent) <br />

Inhalational anesthetic agents Presentation Transcript

  • 1. Dr. Tarun Yadav Department of Anesthesiology – JNMC, Sawangi(M) Wardha 1
  • 2. 1. Introduction 2. Pathway O2-Brain 3.MAC (Definition and Values and factors effecting MAC) 4. Factors determining how quickly the inhalational agent reaches the alveoli reaches and the brain from the alveoli 5. Nitrous Oxide (N2O) 5.1. physical properties, Pharmacology and side effects) 5.2. What is diffusion hypoxia? 5.3. Second gas effect 2
  • 3. 6. Halothane 6.1. properties 6.2. Metabolism 6.3. Dosage, Administration an Supply 6.4. Indications and contraindications 6.5. Effect on Organ Systems 6.6. Advantages and Disadvantages 3
  • 4. 7. Isoflurane and Sevoflurane 7.1. properties 7.2.Effect on Organ Systems 7.3. Advantages and Disadvantages 7.4. Indications and contraindications 4
  • 5. INHALATIONAL ANAESTHETIC AGENT Introduction  IV anesthesia : induce anesthesia Inhalation anesthesia : maintain anesthesia  IV anesthesia : mg/KG or microgram/Kg Inhalation anesthesia : Percentage of the volume % EXAMPLE: 2 L/min. O2 + 4 L/min N2O  Conc. Of N2O = 4/(2+4) = 66% 5
  • 6. 6
  • 7. MAC Definition  Minimal alveolar concentration (MAC): Is defined as the conc. At 1 atmosphere of anesthetic in the alveoli that s required to produce immobility in 50% of adults patient subjected to a surgical incision  MAC is important to compare the potencies of various inhalational anesthetic agents  1.2 -1.3 MAC prevent movement in 95% of patients 7
  • 8. MAC Value N2O = 105%  Halothane = 0.75%  Isoflurane = 1.16%  Euflurane = 1.68%  Sevoflurane = 2%  Deslurane = 6%   N2O alone is unable to produce adequate anesthesia ( require high conc. ) 8
  • 9. 9
  • 10. No Effect on MAC  Gender  Duration of anesthesia  Carbon dioxide tension (21-95 mmHg)  Metabolic Acid base status  Hypertension  Hyperkalemia 10
  • 11. Factors determining how quickly the inhalational agent reaches the alveoli? 1-Increasing the delivered concentrations of anesthetic 2- The gas flow rate through the anesthetic machine 3-Increasing minute ventilation MV = Respiratory Rate × Tidal volume 11
  • 12. Factors determining how quickly the inhalational agent reaches the brain from the alveoli in order to establish anesthesia? 1- The rate of blood flow to the brain 2- The solubility of the inhalational agent in the brain 3- The difference in the arterial and venous concentration of the inhalational agent 12
  • 13. NHALATIONAL ANAESTHETIC AGENT Nitrous Oxide (N2O) 13
  • 14.  Physical - property: laughing Not flammable Odorless Colorless Tasteless 14
  • 15.  PHARMACOLOGY: - Good Analgesic Weak anesthetic Excreted via lungs MAC = 105% Lower water solubility Not Metabolized in the body 15
  • 16.  - SIDE EFFECTS: Diffusion Hypoxia. Effects on closed gas spaces.(nitrous oxide can diffuse 20 times faster into closed spaces than it can be removed, resulting in expansion of pneumothorax, bowel gas, or air embolism or in an increase in pressure within noncompliant cavities such as the cranium or middle ear. - CVS depression Toxicity Teratogenic 16
  • 17. What is diffusion hypoxia? Diffusion hypoxia is a decrease in PO2 usually observed as the patient is emerging from an inhalational anesthetic where nitrous oxide (N2O) was a component. The rapid outpouring of insoluble N2O can displace alveolar oxygen, resulting in hypoxia. All patients should receive supplemental O2 at the end of an anesthetic and during the immediate recovery period. 17
  • 18. Second gas effect: The ability of the large Jan 1, 2014 Dr. Med. Khaled Radaideh volume uptake of one gas (first gas) to accelerate the rate of rise of the alveolar partial pressure of a concurrently administered companion gas (second gas) is known as the second gas effect. 18
  • 19. Halothane 19
  • 20. Synthesized in 1951. * Volatile liquid easily vaporized, stable, and nonflammable * Most potent inhalational anesthetic •MAC of 0.75% •Colorless liquid , pleasant smell , decomposed by light. So should be stored in container away from light and heat • It has low blood/gas solubility coeffient of 2.5 and thus induction of anasthesia is relatively rapid. 20
  • 21.  20% metabolized in liver by oxidative pathways.  Major metabolites : bromin, chlorine, Trifloroacetic acid, Trifloroacetylethanl amide. 21
  • 22. The induction dose varies from patient to patient. The maintenance dose varies from 0.5 to 1.5%.  Halothane may be administered with either oxygen or a mixture of oxygen and nitrous oxide.  How is Halothane Supplied  Halothane is supplied in amber colored 250 mL glass bottles, stabilized with thymol 0.01% (w/w).  Store in cool, dry place and protect from undue exposure to light.  22
  • 23.  Indications  Halothane is indicated for the induction and maintenance of general anesthesia.  Contraindications  Halothane is not recommended for obstetrical anesthesia except when uterine relaxation is required. 23
  • 24. Respiratory system: Halothane anesthesia progressively depresses respiration.  Its cause inhibition of salivary & bronchial secretion.  Its may cause tachypnea & reduce in tidal volume and alveolar ventilation .  Its cause decrease in mucocillary function which lead to sputum retention.  It causes bronchodilation. Hypoxia, acidosis, or apnea may develop during deep anesthesia.  24
  • 25. Cardiovascular system:  Halothane anesthesia reduces the blood pressure, and cause bradycardia.(atropin may reverse bradycardia.).  It cause myocardial relaxation & Hypotention.  Its also causes dilation of the vessels of the skin and skeletal muscles  Halothane maybe advantages In pts with CAD , bcz of decrease of oxygen demand.  Arrhythemias are very commone .(especially with epinephrine). ◦ To minimize effects :  Avoid hypoxemia and hypercapnia  Avoid conc. Of adrenaline higher than 1 in 10000 25
  • 26. Gastro intestinal tract: Inhibition of gastrointestinal motility.  Cause sever post. Operative nausea & vomiting Uterus:  Halothane relaxes uterine muscle, may cause postpartum hemorrhage .  Concentration of less than 0.5 % associated with increase blood loss during therapeutic abortion. Skeletal muscle:  Its cause skeletal muscle relaxation .  Postoperatively , shivering is common , this increase oxygen requirement>>> which cause hypoxemia 26
  • 27. Hepatic dysfunction:  Two type of dysfunction:  1- Type I hepatotoxicity ,mild, associated with derangement in liver function test , this result from metabolic of Halothane in liver. results from reductive (anaerobic) biotransformation of halothane rather than the normal oxidative pathway.  2- Type II hepatotoxicity: fulminate (uncommon); sever jaundice ,fever,progressing to fulminating hepatic necrosis, Its increased by repeated exposure of the drugs. high mortality 30-70% 27
  • 28.  1- A careful anasthetic history .  2- repeated exposure of halothane within 3 months should be avoided.  3- History of unexplained jaundice or pyrexia after previous exposure of halothane. 28
  • 29.  Rapid smooth induction .  Minimal stimulation of salivary & bronchial secretion.  Brochiodilatation.  Muscle relaxant .  Relatively rapid recovery. 29
  • 30.  Poor analgesia.  Arrhythmias.  Post operatively shivering.  Possibility of liver toxicity. 30
  • 31. Enflurane MAC =1.68% Potent cardiovascular depressant Dr. Med. Khaled Radaideh Jan 1, 2014 31
  • 32. Isoflurane Properties - isomer of enflurane. - Carcinogenic (not approved) - colorless, volatile, liquid, pungent odor. - stable. - No preservative . - Non-flammable. 32
  • 33. Isoflurane Properties - Least soluble of the modern inhalational agent  equilibrate more rapidly - Induction rapid theoretically (pungency??) - pungency  cough, breath holding. 33
  • 34. Isoflurane effects on systems:Respiratory: dose dependent depression of vetilation. CVS: - myocardial depressant (vitro Vs Clinical), coronary vasodilatation (coronary steal syndrome). uterus: relaxation of uterine muscles (same). 34
  • 35. Isoflurane effects on systems:CNS: low concentration Vs High concentration. Low : no change on the flow. High : increase blood flow by vasodilatation of the cerebral arteries. -Muscles: relaxation (dose-dependent). 35
  • 36. Isoflurane Advantages and Disadvantages Advantages -Rapid induction and recovery. -Little risk of hepatic or renal toxicity. -Cardiovascular stability. -Muscle relaxation. Disadvantages -Pungent odor. -Coronary vasodilatation. 36
  • 37. Sevoflurane Properties -New drug. -Non flammable. -Pleasant smell. -MAC 2%. -Stable. -Low blood/gas partition coefficient  faster equilibrium. - non irritant so the fastest for induction. 37
  • 38. Sevoflurane Advantages and Disadvantages Advantages Well tolerated (non-irritant, sweet odor), even at high. 1 concentrations, making this the agent of choice for . inhalational induction ) Rapid induction and recovery (low blood:gas coefficient. 2 Does not sensitize the myocardium to catecholamines as. 3 .much as halothane Does not result in carbon monoxide production with dry. 4 . soda lime 38
  • 39. Sevoflurane Advantages and Disadvantages Disadvantages .Less potent than similar halogenated agents. 1 Interacts with CO2 absorbers. In the presence of soda lime. 2 (and more with barium lime) compound A (a vinyl ether) is . produced which is toxic to the brain, liver, and kidneys About 5% is metabolized and elevation of serum fluoride. 3 . levels has led to concerns about the risk of renal toxicity Postoperative agitation may be more common in children. 4 . then seen with halothane 39
  • 40. Sevoflurane effects on systems - Respiratory: -non-irritant, depression. -CVS: same as isoflurane (slightly lower effect) -CNS: same as halothane and isoflurane. -Muscle relaxation: same as isoflurane. 40
  • 41. Desflurane MAC =6 % 41
  • 42. 42