Inhalation anesthetics
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INHALATION ANESTHETICS. Dr. Rupak Bhattarai. INTRODUCTION. Nitrous oxide, Chloroform and Ether were the first universally accepted general anesthetics. Ethyl chloride, Ethylene and Cyclopropane were also used , but the toxicity and flammability led to their withdrawal from the market.

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INHALATION ANESTHETICS

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Inhalation anesthetics

INHALATION ANESTHETICS

Dr. Rupak Bhattarai


Introduction

INTRODUCTION

  • Nitrous oxide, Chloroform and Ether were the first universally accepted general anesthetics.

  • Ethyl chloride, Ethylene and Cyclopropane were also used , but the toxicity and flammability led to their withdrawal from the market.

  • Mainly 5 inhalation anesthetics agents are used in clinical practice these days:

  • 1. Nitrous oxide

  • 2.Halothane

  • 3.Isoflurane

  • 4.Desflurane

  • 5. Sevoflurane


Minimum alveolar concentration mac

MINIMUM ALVEOLAR CONCENTRATION (MAC)

DEF: The minimum alveolar concentration of an inhaled anesthetics is the alveolar concentration that prevents movement in 50% of patient in response to a standardized stimulus (e.g. Surgical Incision)


Mac value of inhalation anesthetics agents

MAC VALUE OF INHALATION ANESTHETICS AGENTS

  • Nitrous oxide: 105%

  • Halothane: 0.75%

  • Isoflurane : 1.2%

  • Desflurane: 6%

  • Sevoflurane: 2%


Nitrous oxide

NITROUS OXIDE

Physical properties:

  • It is a laughing gas.

  • It is only inorganic anesthetic gas in clinical use.

  • Colorless and odorless

  • Non Explosive and Non Infammable

  • Gas at room temperature and can be kept as a liquid under pressure.

  • It is relatively inexpensive.


Effects of nitrous oxide on organ system

Effects of Nitrous Oxide on Organ System

1. CARDIOVASCULAR SYSTEM

  • Stimulate sympathetic nervous system.

  • Directly depresses myocardial contractility.

  • Arterial blood pressure ,heart rate and cardiac output are slightly increased.

    2. RESPIRATORY SYSTEM:

  • Increases respiratory rate with decreases tidal volume.

  • Minimal change in minute ventilation.


Inhalation anesthetics

3. CEREBRAL:

  • Increases CBF thus increasing intracranial pressure.

    4. RENAL SYSTEM:

  • It decreases renal blood flow thus leads to drop in glomerular filtration rate and urinary output.

    5. HEPATIC SYSTEM:

  • Decreases the Hepatic blood flow but to a lesser extent than other inhalation agents.

    6. GASTROINTESTINAL:

  • It causes post operative Nausea and Vomiting.


Contraindication of n2o

CONTRAINDICATION OF N2O

  • Air embolism

  • Pneumothorax

  • Acute Intestinal Obstruction

  • Tension Pneumocephalus

  • Tympanic membrane grafting


Halothane

HALOTHANE

  • Physical Properties:

  • It is halogenated alkene.

  • Non Inflammable and Non explosive.

  • Least expensive .


Effects on organ system

EFFECTS ON ORGAN SYSTEM

  • CARDIOVASCULAR:

  • Dose dependent reduction of arterial blood pressure by direct myocardial depression.

  • It is a coronary artery vasodilator.

  • It causes slowing of SA node conduction resulting in bradycardia.

    2. RESPIRATORY SYSTEM:

  • Causes rapid ,shallow breathing.

  • Decrease in alveolar ventilation and Paco2 elevated.

  • Potent dronchodilator.


Inhalation anesthetics

3. CEREBRAL:

  • It increases cerebral blood flow.

    4. NEUROMUSCULAR:

  • Relaxes skelatal muscle and potentiates Non depolarizing neuro-muscular blocking agents.

    5.RENAL:

  • Reduces renal blood flow, glomerular filtration rate and urinary output.

    6. HEPATIC:

  • Decreases hepatic blood flow.


Contraindication

CONTRAINDICATION

  • Unexplained liver dysfunction.

  • Intra-cranial mass lesions.

  • Hypo-volemic patient with severe cardiac diseases.


Isoflurane

ISOFLURANE

  • It is non flammable volatile with a pungent smell.

    EFFECTS ON ORGAN SYSTEM:

  • CARDIOVASCULAR:

  • Causes minimal cardiac depression.

  • Rapid increase in MAC lead to increase in HR and BP.( Coronary Steal)

  • Dilates coronary arteries.

    2. RESPIRATORY SYSTEM:

  • Respiratory depression .

  • Acts as a good bronchodilator.


Inhalation anesthetics

3. CEREBRAL:

If con> 1 MAC causes increase in CBF and Intracranial pressure.

4. NEUROMUSCULAR:

Relaxes skeletal muscles.

5. RENAL:

Decreases renal blood flow , glomerular filtration rate and urinary output.

6. HEAPTIC:

Reduces hepatic blood flow.

INDICATIONS- For Cardiac and Neuro- Surgery


Contraindication1

CONTRAINDICATION

  • No such contraindication.

  • Patient with severe hypovolemia may not tolorate its vasodilating effects.


Desflurane

DESFLURANE

  • Structure much similar to that of isoflurane.

  • Recovery time are approximately 50 % less than those of Isoflurane. Pungent Smell

  • TEC 6

    EFFECTS ON ORGAN SYSTEM:

  • CARDIOVASCULAR SYSTEM:

  • Similar to Isoflurane( Increases HR and BP when increased MAC rapidly)

  • Dilates coronary arteries.


Inhalation anesthetics

2. RESPIRATORY SYSTEM:

  • Causes decrease in tidal volume and increase in resp rate.

  • Pungency and airway irritation so causes coughing and sometime bronchospasm.

    3. CEREBRAL:

  • Increases CBF and Intracranial pressure.

    4. NEUROMUSCULAR:

  • Relaxes skeletal muscle.

    5. RENAL AND HEPATIC SYSTEM:

  • No any evidence has been documented.

    INDICATION- For Hepatic and Renal Surgery


Contraindication2

CONTRAINDICATION

  • Severe hypo-volemia.

  • Intracranial hypertension.

  • Malignant hyperthermia.


Sevoflurane

SEVOFLURANE

  • It is Non pungency.

    EFFECTS ON ORGANS:

  • CARDIOVASCULAR SYSTEM:

  • Mildly depresses myocardial contractility.

  • May prolong QT interval, but no significance.

    2. RESPIRATORY SYSTEM:

  • Depresses respiratory rate.

  • It reverses broncho-spasm


Inhalation anesthetics

3. CEREBRAL:

  • Increases CBF and intra-cranial pressure.

    4. RENAL SYSTEM:

  • Slightly decreases renal blood flow. Higher Conc Causes Nephro-toxicity

    5. HEPATIC:

  • Decreases portal vein blood flow but increases hepatic artery blood flow thus maintaining total hepatic blood flow.

    6.NEUROMUSCULAR:

  • Adequate muscle relaxation.


Contraindication3

CONTRAINDICATION

  • Severe hypo-volemia.

  • Intracranial hypertension.

  • Malignant hyperthermia.


Ether

ETHER

  • W.T.G Morton on 16th Oct 1846 used for removal of jaw tumor.

    PHYSICAL PROPERTIES:

  • Pungent smelling liquid, decomposes in presence of light, air, heat.

  • Highly inflammable and explosive.

  • Highly irritant vapour.

  • Very Cheap.

  • Also called as Complete Anesthetic agents.

  • Can be used by less experience hands.


Inhalation anesthetics

  • Induction very slow, pungent smells and may causes laryngeal spasm

  • Very good analgesic.

  • Very good muscle relaxants.


Inhalation anesthetics

  • Cardiovascular: Does-not depresses myocardium, but stimulates sympathetic system.

  • Respiratory system: Does-not depresses respiration.

    It is a potent bronchodilator.

    Tracheo-bronchial secretions is markedly increased.

  • GIT: Nausea and vomiting.

  • Hepatic and renal: Well preserved.

  • Cerebral: Increases intracranial pressure.

  • May causes Hyperglycemia.


Stages of ether anesthesia

STAGES OF ETHER ANESTHESIA

  • STAGE I: (Stage of analgesia) (From analgesia to loss of consciousness)

  • Respiration is regular with small tidal volume.

  • Pupil is normal in size.

  • STAGE II : (Stage of Excitement): ( From loss of consciousness to rhythmic respiration)

  • Respiration is irregular.

  • Pupil is Mid dilated.

  • Eyelashes reflex absent.


Inhalation anesthetics

  • STAGE III : ( Stage of Anesthesia):

  • Plane I: ( From rhythmic resp to cessation of eye movement)Respiration is regular with large volume. Pupil is normal in size. Eyelashes reflex absent, Pharyngeal and vomiting reflex lost.

  • Plane II: (From cessation of eye movement to resp paresis)Respiration is regular with large volume , Pupil is mid dilated with corneal reflexes lost.

  • Plane III: ( Resp paresis to Paralysis)From Respiration is regular with small volume, Pupil is moderate dilated with laryngeal reflexes absent.

  • Plane IV: (Diaphragmatic Paralysis)Respiration is irregular with small volume, Pupil dilated and centrally placed.


Inhalation anesthetics

  • Stage IV: (Stage of overdose) (Medullary Paralysis)

  • Apnea

  • Pupil dilated and non reacting to light.

    NOTE: Withdrawal of anesthetic agents and administration of 100% oxygen lightens anesthesia with recovery.


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