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Presentator – Dr.Milan Kharel
Moderator - Dr. Madhu Gyawali
 IV anesthesia : induce anesthesia
Inhalation anesthesia : maintain anesthesia
 IV anesthesia : mg/KG or microgram/Kg
In...
HISTORY OF ANESTHESIA
 Diethyl ether first used by William T.G. Morton in the USA
in 1846
 Chloroform was the next agent to receive attention,...
 Halothane, synthesized in 1951 by prominent
British chemist, Charles Walter Suckling,
while working at the Imperial Chem...
 a variety of other agents were investigated but
discarded for various reasons
A.Explosive mixtures with oxygen –
-diethy...
THE BASIC CONCEPTS…
7
MAC Definition
 Minimal alveolar concentration (MAC):
Is defined as the conc. At 1 atmosphere of
anesthetic in the alveol...
MAC Value
 N2O = 105%
 Halothane = 0.75%
 Isoflurane = 1.16%
 Euflurane = 1.68%
 Sevoflurane = 2%
 Deslurane = 6%
 ...
10
No Effect on MAC
 Gender
 Duration of anesthesia
 Carbon dioxide tension (21-95 mmHg)
 Metabolic Acid base status
 Hy...
 Pressure exerted by the molecules of the vapor phase at
equilibrium of molecules moving in and out of liquid phase
 Vap...
Vapour Pressure & BP
Agent BP (0
C) VP (20 0
C)
Halothane 50 243
Enflurane 56 175
Isoflurane 48 238
Sevoflurane 58 160
Des...
15
1. Transfer from Inspired Air to Alveoli
i. the inspired gas concentration FI
ii. alveolar ventilation VA
iii. characteris...
A)Inspired Gas Concentration FI:-
 according to Dalton's law of partial pressures, the
tension of an individual gas in in...
 each inspiration delivers some anaesthetic to the
lung and, if unopposed by uptake into the blood,
normal ventilation wo...
 A) Blood:Gas Partition Coefficient
 the solubility of a gas in liquid is given by its
Ostwald solubility coefficient, τ...
Solubility of Inhaled Drugs
solubility (partition) coefficient - the extent to
which a gas will dissolve in a given solven...
Solubility of Inhaled Drugs
Halo Enflur Isoflur Sevofl Desfl N2O
Blood/G
as
2.54 1.8 1.4 0.69 0.42 0.47
Brain/Bl
ood
1.9 -...
Solubility of Inhaled Drugs
 Effective pulmonary blood flow determines the
rate at which agents pass from gas to blood
 an increase in flow will slo...
 this represents tissue uptake of the inhaled
agent
 blood cannot approach equilibrium with alveolar air
until the distr...
 A) Tissue:Blood Partition Coefficient:-
 the rate of rise of tension in these regions is
proportional to the arterial-t...
 Methoxyflurane- 61
 Halothane- 62
 Enflurane -36
 Isoflurane- 52
 Sevoflurane -55
 Desflurane - 30
 Nitrous Oxide-...
 the higher the blood flow to a region, the faster the
delivery of anaesthetic and the more rapid will be
equilibration
...
 a. vessel rich group VRG - brain, heart,
kidney & liver
 b. the muscle group MG - muscle & skin
 c. the fat group FG -...
 with equilibration tissue tension rises and the rate
of diffusion slows, as does uptake in the lung
 the rate is determ...
 Concentration and Second Gas Effects
 - increasing the inspired concentration not only
increases the alveolar conc but ...
 this effect is also important where there is a
second gas, such as 1% halothane, in the
inspired mixture
 the removal o...
 
1. Rapid and pleasant induction
2. Rapid changes in the depth of anesthesia
3. Adequate muscle relaxation
4. Wide margin...
INHALATIONAL ANAESTHETIC
AGENTS
35
CLASSIFICATION
1.Gas :
• Nitrous Oxide
2. Volatile Liquids :
• Ether
• Halothane
• Enfl...
Nitrous Oxide (N2O)
36
 Physical property:
- laughing
- Not flammable
- Odorless
- Colorless
- Tasteless
37
 PHARMACOLOGY:
- Good Analgesic
- Weak anesthetic
- Excreted via lungs
- MAC = 105%
- Lower water solubility
- Not Metabo...
 SIDE EFFECTS:
- Diffusion Hypoxia.
- Effects on closed gas spaces.(nitrous oxide can
diffuse 20 times faster into closed...
What is diffusion hypoxia?
Diffusion hypoxia is a decrease in PO2 usually
observed as the patient is emerging from an
inha...
Second gas effect: The ability of the large
volume uptake of one gas (first gas) to
accelerate the rate of rise of the alv...
EFFECT IN CLOSED GAS SPACE
ETHER
•Properties:
•Colorless, highly volatile, pungent odor,
flammable, explosive, stored in cool area.
Solubility 12;
MAC 2-3%
•Pharmacodynamics:
Lungs: Stimulates resp, increases secretion, not
good in respiratory diseases
Kidney: decreases urine...
Ether as an anesthetic
•Advantage: CNS depression, excellent muscle
relaxant, causes surgical anesthesia
•Disadvantage: Fl...
Halothane
Synthesized in 1951.
* Most potent inhalational anesthetic
•MAC of 0.75%
It has low blood/gas solubility coeffient of 2.5 ...
 Chemical and Physical Properties
 Halogenated compound chemically:
2-bromo-2-chloro-1,1,1-tri fluoro
ethane
 Volatile,...
Potency is
defined(determined)
quantitatively as the minimum
alveolar concentration (MAC),
Numerically, MAC is small for...
 Halothane is a potent anesthetic but a relatively
weak analgesic. Thus, it is usually coadministered
with nitrous oxide,...
 No specific receptor has been identified as the locus of
general anesthetic action –generally-.
 It appears that a vari...
 20% metabolized in liver by oxidative
pathways.
 Major metabolites : bromin, chlorine,
Trifloroacetic acid, Trifloroace...
 The induction dose varies from patient to patient.
The maintenance dose varies from 0.5 to 1.5%.
 Halothane may be admi...
 Indications
 Halothane is indicated for the induction and
maintenance of general anesthesia.
 Contraindications
 Halo...
Respiratory system:
 Halothane anesthesia progressively depresses
respiration.
 Its cause inhibition of salivary & bronc...
Cardiovascular system:
 Halothane anesthesia reduces the blood pressure, and cause
bradycardia.(atropin may reverse brady...
Gastro intestinal tract:
Inhibition of gastrointestinal motility.
 Cause sever post. Operative nausea & vomiting
Uterus:
...
Hepatic dysfunction:
 Two type of dysfunction:
 1- Type I hepatotoxicity ,mild, associated with derangement
in liver fun...
 1- A careful anasthetic history .
 2- repeated exposure of halothane within
3 months should be avoided.
 3- History of...
 Rapid smooth induction .
 Minimal stimulation of salivary & bronchial
secretion.
 Brochiodilatation.
 Muscle relaxant...
 Poor analgesia.
 Arrhythmias.
 Post operatively shivering.
 Possibility of liver toxicity.
Enflurane
•MAC =1.68%
•Potent cardiovascular depressant
Sweet and ethereal odor.
Generally do not sensitizes the heart to
...
Isoflurane
Properties
- isomer of enflurane.
- Carcinogenic (not approved)
- colorless, volatile, liquid, pungent odor.
- ...
Isoflurane
Properties
- Least soluble of the modern inhalational agent 
equilibrate more rapidly
- Induction rapid theore...
Isoflurane
effects on systems:-
Respiratory:
dose dependent depression of vetilation.
CVS:
- myocardial depressant (vitro ...
Isoflurane
effects on systems:-
CNS:
low concentration Vs High concentration.
Low : no change on the flow.
High : increa...
Isoflurane
Advantages and Disadvantages
Advantages
-Rapid induction and recovery.
-Little risk of hepatic or renal toxicit...
Sevoflurane
Properties
-New drug.
-Non flammable.
-Pleasant smell.
-MAC 2%.
-Stable.
-Low blood/gas partition coefficient ...
Sevoflurane
effects on systems
-- Respiratory:
-non-irritant, depression.
-CVS: same as isoflurane (slightly lower
effect)...
Sevoflurane
Advantages and Disadvantages
Advantages
1.Well tolerated (non-irritant, sweet odor), even at high
concentratio...
Sevoflurane
Disadvantages
1.Less potent than similar halogenated agents.
2.Interacts with CO2
absorbers. In the presence o...
Desflurane
MAC =6 %
It is delivered through special vaporizer.
It is a popular anesthetic for day care surgery.
Induction ...
Anesthetic Blood: Gas
Partition
Coefficients
Oil: Gas
Partition
Coefficients
Features Notes
Halothane 2.3 220 PLEASANT Arr...
Miller’s Anesthesia 7th
Edition
Pharmacology – K.D. Tripathi Clinical Pharmacology – Bennett & Brown
78
Inhalational Anesthetic Agents
Inhalational Anesthetic Agents
Inhalational Anesthetic Agents
Inhalational Anesthetic Agents
Inhalational Anesthetic Agents
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Inhalational Anesthetic Agents

  1. 1. Presentator – Dr.Milan Kharel Moderator - Dr. Madhu Gyawali
  2. 2.  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% INHALATIONAL ANAESTHETIC AGENT Introduction
  3. 3. HISTORY OF ANESTHESIA
  4. 4.  Diethyl ether first used by William T.G. Morton in the USA in 1846  Chloroform was the next agent to receive attention, by James Simpson in 1847 it was discontinued due to:- a. severe cardiovascular depression (sudden death ? VF) b. dose dependent hepatotoxicity  Cyclopropane was discovered accidentally in 1929 and was very popular for almost 30 yrs  the increasing use of electronic equipment necessitated the discontinuation of this inflammable agent.
  5. 5.  Halothane, synthesized in 1951 by prominent British chemist, Charles Walter Suckling, while working at the Imperial Chemical Industries (ICI). Later in 1956, M. Johnstone used it clinically first time  Enflurane has been in use since 1970  Isoflurane- (1981), Desflurane-1996
  6. 6.  a variety of other agents were investigated but discarded for various reasons A.Explosive mixtures with oxygen – -diethyl ether - ethyl chloride - divinyl ether - cyclopropane b. postoperative liver necrosis / sudden death - chloroform c. postoperative renal failure - methoxyflurane
  7. 7. THE BASIC CONCEPTS… 7
  8. 8. MAC Definition  Minimal alveolar concentration (MAC): Is defined as the conc. At 1 atmosphere of anesthetic in the alveoli that is 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 8
  9. 9. 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. ) 9
  10. 10. 10
  11. 11. No Effect on MAC  Gender  Duration of anesthesia  Carbon dioxide tension (21-95 mmHg)  Metabolic Acid base status  Hypertension  Hyperkalemia 11
  12. 12.  Pressure exerted by the molecules of the vapor phase at equilibrium of molecules moving in and out of liquid phase  Vapor Pressure dependent on temperature and physical characteristics of liquid, independent of atmospheric pressure  ↑ Temperature→↑ Vapor Pressure  Vapor pressure is a measure of the agent’s ability to evaporate (volatility) .The greater is the vapor pressure, the greater the concentration of inhalant deliverable to the patient (and environment).  Boiling Point: Temperature at which vapor pressure equals atmospheric pressure Vapour Pressure & BP
  13. 13. Vapour Pressure & BP Agent BP (0 C) VP (20 0 C) Halothane 50 243 Enflurane 56 175 Isoflurane 48 238 Sevoflurane 58 160 Desflurane 23 664 Nitrous Oxide -89 Xenon -107
  14. 14. 15
  15. 15. 1. Transfer from Inspired Air to Alveoli i. the inspired gas concentration FI ii. alveolar ventilation VA iii. characteristics of the anaesthetic circuit 2. Transfer from Alveoli to Arterial Blood i. blood:gas partition coefficient τB:G ii. cardiac output CO iii. alveoli to venous pressure difference dPA-vGas 3. Transfer from Arterial Blood to Tissues i. tissue:blood partition coefficient τT:B ii. tissue blood flow iii. arterial to tissue pressure difference dPa-tGas
  16. 16. A)Inspired Gas Concentration FI:-  according to Dalton's law of partial pressures, the tension of an individual gas in inspired air is equal to,  PIgas = FIgas x Atm  the greater the inspired pressure the greater the approach of FA to FI = the concentration effect  this is only significant where FI is very high, as is the case for N2O (or cyclopropane)  when another gas is used in the presence of such an agent, there is increased uptake of the second gas, the Second gas effect
  17. 17.  each inspiration delivers some anaesthetic to the lung and, if unopposed by uptake into the blood, normal ventilation would increase FA/FI to 95-98% in 2 minutes  this rate of rise is dependent upon minute ventilation and FRC  the greater the FRC, the slower the rise in FA  hyperventilation will decrease CBF, and this tends to offset the increased rise of FA/FI
  18. 18.  A) Blood:Gas Partition Coefficient  the solubility of a gas in liquid is given by its Ostwald solubility coefficient, τ  this represents the ratio of the concentration in blood to the concentration in the gas phase  lower B:G coefficients are seen with, haemodilution ,obesity , hypoalbuminaemia and starvation  higher coefficients are seen in, adults versus children, hypothermia & postprandially
  19. 19. Solubility of Inhaled Drugs solubility (partition) coefficient - the extent to which a gas will dissolve in a given solvent Predicts the speed of induction, recovery, and change in anesthetic depth for an inhalant. Ideal inhaled anesthetics should have low blood/gas and low tissue/blood solubility and low solubility in plastic and rubber. Low solubility means rapid induction and emergence and more precise control
  20. 20. Solubility of Inhaled Drugs Halo Enflur Isoflur Sevofl Desfl N2O Blood/G as 2.54 1.8 1.4 0.69 0.42 0.47 Brain/Bl ood 1.9 - 1.6 1.7 1.3 0.5 Fat/ Blood 51 - 45 48 27 2.3
  21. 21. Solubility of Inhaled Drugs
  22. 22.  Effective pulmonary blood flow determines the rate at which agents pass from gas to blood  an increase in flow will slow the initial portion of the arterial tension/time curve by delaying the approach of FA to FI  a low CO state, conversely, will speed the rise of FA/FI  these effects are greater for highly soluble agents
  23. 23.  this represents tissue uptake of the inhaled agent  blood cannot approach equilibrium with alveolar air until the distribution of anaesthetic from the blood to the tissues is nearly complete  with equilibration, the alveolar/mixed venous tension difference progressively falls as tissue tensions rises  since diffusion is directly proportional to the tension difference, the rate of diffusion into the blood progressively slows
  24. 24.  A) Tissue:Blood Partition Coefficient:-  the rate of rise of tension in these regions is proportional to the arterial-tissue tension difference conversely, their solubility in lipid tissues is far greater than that for blood  at equilibrium the concentration in lipid tissues will be far greater than that in blood  the tissue concentration will rise above that of blood well before pressure equilibrium, even though the tissue tension is lower
  25. 25.  Methoxyflurane- 61  Halothane- 62  Enflurane -36  Isoflurane- 52  Sevoflurane -55  Desflurane - 30  Nitrous Oxide- 2.3
  26. 26.  the higher the blood flow to a region, the faster the delivery of anaesthetic and the more rapid will be equilibration  the body tissues have been divided into groups according to their level of perfusion and tissue blood flow,
  27. 27.  a. vessel rich group VRG - brain, heart, kidney & liver  b. the muscle group MG - muscle & skin  c. the fat group FG - large capacity/minimal flow  d. vessel poor group VPG - bone, cartilage, CT
  28. 28.  with equilibration tissue tension rises and the rate of diffusion slows, as does uptake in the lung  the rate is determined by the tissue time constant, which in turn depends upon both the tissue capacity (τT:B) and the tissue blood flow  TC(τ)= Tissue Capacity / 100g Blood Flow/ 100g
  29. 29.  Concentration and Second Gas Effects  - increasing the inspired concentration not only increases the alveolar conc but also increases the rate of rise of volatile anaesthetic agents in the alveoli  eg., during the inhalation of 75% N2O/O2, initially as much as 1 l/min may diffuse into the bloodstream across the lungs ,this effectively draws more gas into the lungs from the anaesthetic circuit, thereby increasing the effective minute ventilation
  30. 30.  this effect is also important where there is a second gas, such as 1% halothane, in the inspired mixture  the removal of a large volume of N2O from the alveolar air increases the delivery of the second gas, effectively increasing its delivery to the alveoli and increasing its diffusion into arterial blood K/A Second Gas Effect
  31. 31.   1. Rapid and pleasant induction 2. Rapid changes in the depth of anesthesia 3. Adequate muscle relaxation 4. Wide margin of safety 5. Absence of toxic/adverse effects   CHARACTERISTICS OF AN IDEAL ANESTHETIC No single agent yet identified is an ideal anesthetic
  32. 32. INHALATIONAL ANAESTHETIC AGENTS 35 CLASSIFICATION 1.Gas : • Nitrous Oxide 2. Volatile Liquids : • Ether • Halothane • Enflurane • Isoflurane • Desflurane • Sevoflurane
  33. 33. Nitrous Oxide (N2O) 36
  34. 34.  Physical property: - laughing - Not flammable - Odorless - Colorless - Tasteless 37
  35. 35.  PHARMACOLOGY: - Good Analgesic - Weak anesthetic - Excreted via lungs - MAC = 105% - Lower water solubility - Not Metabolized in the body 38
  36. 36.  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 39
  37. 37. 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. 40
  38. 38. Second gas effect: The ability of the large 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. 41
  39. 39. EFFECT IN CLOSED GAS SPACE
  40. 40. ETHER
  41. 41. •Properties: •Colorless, highly volatile, pungent odor, flammable, explosive, stored in cool area. Solubility 12; MAC 2-3%
  42. 42. •Pharmacodynamics: Lungs: Stimulates resp, increases secretion, not good in respiratory diseases Kidney: decreases urine output Liver: Minimum effect, decreases liver glycogen Heart: Initially increases cardiac output, then decreases card. output, suppresses vasomotor center.
  43. 43. Ether as an anesthetic •Advantage: CNS depression, excellent muscle relaxant, causes surgical anesthesia •Disadvantage: Flammable, irritates mucus membrane, breath holding, induces nausea & vomiting •Contraindications: Resp., kidney and liver diseases •Better agents are available now, so not used now.
  44. 44. Halothane
  45. 45. Synthesized in 1951. * Most potent inhalational anesthetic •MAC of 0.75% It has low blood/gas solubility coeffient of 2.5 and thus induction of anasthesia is relatively rapid.
  46. 46.  Chemical and Physical Properties  Halogenated compound chemically: 2-bromo-2-chloro-1,1,1-tri fluoro ethane  Volatile, so kept in sealed bottles  Colorless, Pleasant odor, Non-irritant  Non-explosive, Non-inflammable  Light-sensitive  Corrosive, Interaction – rubber and plastic tubing
  47. 47. Potency is defined(determined) quantitatively as the minimum alveolar concentration (MAC), Numerically, MAC is small for potent anesthetics such as Halothane and large for less potent agents such as nitrous oxide.
  48. 48.  Halothane is a potent anesthetic but a relatively weak analgesic. Thus, it is usually coadministered with nitrous oxide, opioids, or local anesthetics.  It is a potent bronchodilator.  Halothane relaxes both skeletal and uterine muscles and can be used in obstetrics when uterine relaxation is indicated.  Halothane is not hepatotoxic in children (unlike its potential effect on adults).  Combined with its pleasant odor, it is suitable in pediatrics for inhalation induction, although sevoflurane is now the agent of choice.
  49. 49.  No specific receptor has been identified as the locus of general anesthetic action –generally-.  It appears that a variety of molecular mechanisms may contribute to the activity of general anesthetics.  Halothane activates GABAA , glycine receptors, 5-HT3and  twin-pore K+ channels .  It antagonizes NMDA receptor.  It inhibits nACh(block excitatory postsynaptic currents of nicotinic receptors) and voltage-gated sodium channels. --------------------------------------------------------------------------------------- --  At clinically effective concentrations, general anesthetics increase the sensitivity of the γ-aminobutyric acid (GABA-A) receptors to the inhibitory neurotransmitter GABA. This increases chloride ion influx and cause Hyperpolarization  Decrease Excitability  CNS Depression
  50. 50.  20% metabolized in liver by oxidative pathways.  Major metabolites : bromin, chlorine, Trifloroacetic acid, Trifloroacetylethanl amide.
  51. 51.  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.
  52. 52.  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.
  53. 53. 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.
  54. 54. 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 common .(especially with epinephrine). ◦ To minimize effects :  Avoid hypoxemia and hypercapnia  Avoid conc. Of adrenaline higher than 1 in 10000
  55. 55. 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
  56. 56. 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%
  57. 57.  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.
  58. 58.  Rapid smooth induction .  Minimal stimulation of salivary & bronchial secretion.  Brochiodilatation.  Muscle relaxant .  Relatively rapid recovery.
  59. 59.  Poor analgesia.  Arrhythmias.  Post operatively shivering.  Possibility of liver toxicity.
  60. 60. Enflurane •MAC =1.68% •Potent cardiovascular depressant Sweet and ethereal odor. Generally do not sensitizes the heart to catecholamines. Seizures occurs at deeper levels – contraindicated in epileptics. Caution in renal failure due to fluoride.
  61. 61. Isoflurane Properties - isomer of enflurane. - Carcinogenic (not approved) - colorless, volatile, liquid, pungent odor. - stable. - No preservative . - Non-flammable.
  62. 62. Isoflurane Properties - Least soluble of the modern inhalational agent  equilibrate more rapidly - Induction rapid theoretically (pungency??) - pungency  cough, breath holding.
  63. 63. 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).
  64. 64. 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).
  65. 65. 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.
  66. 66. 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.
  67. 67. 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.
  68. 68. Sevoflurane Advantages and Disadvantages Advantages 1.Well tolerated (non-irritant, sweet odor), even at high concentrations, making this the agent of choice for inhalational induction. 2.Rapid induction and recovery (low blood:gas coefficient) 3.Does not sensitize the myocardium to catecholamines as much as halothane. 4.Does not result in carbon monoxide production with dry soda lime.
  69. 69. Sevoflurane Disadvantages 1.Less potent than similar halogenated agents. 2.Interacts with CO2 absorbers. In the presence of soda lime (and more with barium lime) compound A (a vinyl ether) is produced which is toxic to the brain, liver, and kidneys. 3.About 5% is metabolized and elevation of serum fluoride levels has led to concerns about the risk of renal toxicity. 4.Postoperative agitation may be more common in children then seen with halothane.
  70. 70. Desflurane MAC =6 % It is delivered through special vaporizer. It is a popular anesthetic for day care surgery. Induction and recovery is fast, cognitive and motor impairment are short lived It irritates the air passages producing cough and laryngospasm.
  71. 71. Anesthetic Blood: Gas Partition Coefficients Oil: Gas Partition Coefficients Features Notes Halothane 2.3 220 PLEASANT Arrhythmia Hepatitis Hyperthermia Enflurane 1.9 98 PUNGENT Seizures Hyperthermia Isoflurane 1.4 91 PUNGENT Widely used Sevoflurane 0.62 53 PLEASANT Ideal Desflurane 0.42 23 IRRITANT Cough Nitrous oxide 0.47 1.4 PLEASANT Anemia
  72. 72. Miller’s Anesthesia 7th Edition Pharmacology – K.D. Tripathi Clinical Pharmacology – Bennett & Brown
  73. 73. 78
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Inhalational Anesthetic Agents

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