Effect on respiratory system:


  • All inhalational agents.
  • Halothane – Maximum bronchodilatation.
  • DOC in asthmatics (intravenous anesthetics) = Ketamine.

Respiratory depression (minimal):

  • All inhalational agents.
  • Enflurane – Maximum depression.
  • Halothane – Maximum inhibition of ventilatory response to increased CO2 & hypoxia.


  • Vasodilate pulmonary vascular bed – All inhalational agents.
  • By blunting hypoxic pulmonary vasoconstriction (HPV) response. 
  • Halothane – Maximum effect; Also by isoflurane

Phosgene production:

  • By Trilene -> Causes ARDS.
Effects on CVS:
Cardiac output: 

  • CO best maintained with isoflurane.
  • Isoflurane – Most cardiostable inhalational agent & agent of choice for cardiovascular surgery.
  • Due to reflex tachycardia acting as protective baroreceptor reflex is minimally inhibited by isoflurane. 

CO decreasing drugs:

  • All inhalational agents decrease CO, except ether & cyclopropane.
  • Cardiovascular stability in decreasing order:Isoflurane (most stable) > desflurane > Sevoflurane > Halothane > Enflurane. 

Baroreceptor reflex:

  • Halothane – Only agent suppressing baroreceptor reflex –> causes tachycardia.

Myocardial contractility:

  • All inhalational agents cause directly depress contractility. 
  • Isoflurane, desflurane & sevoflurane cause minimum depression to similar level.
Systemic vascular resistance (SVR):

  • All inhalational agents decrease –> result in hypotension. 
  • Except cyclopropane, ether, halothane & N20 – Not decrease SVR.
  • Isoflurane, Desflurane & Halothane = Cause maximum hypotension.
  • Isoflurone – Inhalational DOC for controlled hypotension.
  • Note: Halothane causes hypotension by myocardial depression, not decrease SVR.
Cardiac adrenaline sensitization:

  • Halothane – Sensitizes heart to adrenaline –> Results in arrhythmias.
  • Contraindicated in pheochromocytoma along with adrenaline.

Sympathetic stimulation:

  • Cyclopropane & Ether -> maintain CO & not decrease SVR.
  • (Note: Other inhalational agents cause those effects).
Coronary steal phenomenon.

  • By Isoflurane
  • Mainly in patient with coronary artery stenosis.
  • Causes coronary artery vasodilatation in non-ischemic area & diverts blood away from ischemic zone.
  • N20 has no effect on BP, CO HR.

Effect on liver:


  • Mild toxicity – All inhalational agents.
  • By decreasing hepatic blood flow.
  • Direct hepatotoxicity (hepatitis, hepatic necrosis)
  • Halothane, chloroform, trilene & methoxyflurane.

DOC in liver disease

  • Isoflurane – Due to least effect on hepatic blood flow.

Effect on kidney:

Renal function depression:

  • All inhalational agents.
  • By decreasing renal blood flow. 

Nephrotoxic agent:

  • Most nephrotoxic – Methoxyflurane causes high output (polyuric) renal failure.
  • Sevoflurane & enflurane – No renal toxicity in normal person; contraindicated in renal patients.
  • By producing nephrotoxic compound A.
  • Desflurane has no nephrotoxicity.


  • Direct toxicity caused by fluorinated compounds due to inorganic fluoride (F-) production.
  • Renal threshold beyond which fluoride levels are toxic is 50 mm. 

Effect on Brain:

Increasing ICT:

  • All inhalational agents.
  • By increasing cerebral blood flow –> ICT.
  • Provide cerebral protection by decreasing cerebral metabolic rate.
  • Maximum cerebral protection – Isoflurane.
  • Inhalational DOC for neurosurgery.
  • Enflurane – Provokes seizure.
  • Contraindicated in epilepsy.


  • Dichloroacetylene involving most commonly 5th CN.

Effect on hematopoietic system:

  • Bone marrow depression (aplastic anemia) & Vit B12 deficiency – By nitrous oxide.
  • Vit B12 deficiency causes megaloblastic anemia & subacute degeneration of spinal cord.

Effect on muscle relaxation & analgesia:

Muscle relaxation:

  • All inhalational agents except N2O. 
  • By neuro-muscular blockade.
  • Maximum relaxation – By ether (unused), desflurane.

Analgesic action:

  • All inhalational agents except halothane.
  • Maximum – Trilene, N2O & ether. 
  • No analgesic action – Halothane.

Effect on uterine relaxation:

  • All fluorinated anesthetics.
  • Halothane (maximum), isoflurane, desflurane, sevoflurane, enflurane.


  • DOC for assisting external or internal version during late pregnancy.
  • Contraindicated during labor 4 – Due to post-partum hemorrhage.

Effect on Inflammability & reaction with sodaline:

Inflammable agents:

  • Ether, Cyclopropane, ethylene oxide, ethyl chloride.
  • Cautery should not be used in vicinity (up to 25 cms).

Inducing inflammability:

  • Agents can be made non-inflammable by adding fluorine atoms.
  • Trichloroethylene (Trilene) & sevoflurane reacts with soda lime -> Not be used in closed (circle) system.

Effect on metabolism:

  • Most inhaled anesthetics are eliminated from lung.
  • Hepatic metabolism also occurs in order:
  • Methoxyflurane (> 50%) > Halothane (20%)> Ether (10 -15%) > enflurane (3-5%) > sevoflurane (3%) > isoflurane (0.2%) > desflurane (< 0.1%) > N20 (0%). 
  • N20 does not have any metabolism in body.
  • Some agent cause hyperglycemia; chloroform (most profound), ether cyclopropane.

Effects on anesthetic circuit:

  • Corroding metals & vaporizing in breathing circuit – Halothane.
  • Halothane & methoxyflurane – Absorbed by rubber of anesthetic circuit & polyvinylchloride of ET tube.
  • Can be used only on replacing plastic tubing.

Exam Important

  • Halothane causes maximum bronchodilatation.
  • DOC in asthmatics (intravenous anesthetics) is ketamine.
  • All inhalational agents vasodilate pulmonary vascular bed, by blunting hypoxic pulmonary vasoconstriction (HPV) response. 
  • Halothane has maximum vasodilatory effect.
  • CO best maintained with isoflurane.
  • Isoflurane is most cardiostable inhalational agent & agent of choice for cardiovascular surgery.
  • Halothane, only agent suppressing baroreceptor reflex –> causes tachycardia.
  • Isoflurane, desflurane & sevoflurane depress myocardial contractility to similar level.
  • Isoflurane is inhalational DOC for controlled hypotension.
  • Halothane sensitizes heart to adrenaline resulting arrhythmias, contraindicated in pheochromocytoma along with adrenaline.
  • Isoflurane causes coronary steal phenomenon.
  • DOC in liver disease is Isoflurane, due to least effect on hepatic blood flow.
  • Direct hepatotoxicity (hepatitis, hepatic necrosis) are caused by Halothane, chloroform, trilene & methoxyflurane.
  • Most nephrotoxic is Methoxyflurane causes high output (polyuric) renal failure.
  • Desflurane has no nephrotoxicity.
  • Sevoflurane & enflurane causes no renal toxicity in normal person;contraindicated in renal patients.
  • Isoflurane provides maximum cerebral protection by decreasing cerebral metabolic rate, hence inhalational DOC for neurosurgery.
  • Enflurane provokes seizure & contraindicated in epilepsy.
  • Nitrous oxide causes bone marrow depression (aplastic anemia) & Vit B12 deficiency.
  • Vit B12 deficiency causes megaloblastic anemia & subacute degeneration of spinal cord.
  • Maximum analgesic action is seen with Trilene & nil analgesic action with halothane.
  • Halothane (maximum), isoflurane, desflurane, sevofluraneenflurane can cause uterine relaxation.
  • Halothane DOC for assisting external or internal version during late pregnancy.
  • Halothane is contraindicated during labor 4 – Due to post-partum hemorrhage.
  • Inflammable agents are ether, Cyclopropane, ethylene oxide, ethyl chloride & cautery should not be used in vicinity (up to 25 cms).
  • Trichloroethylene (Trilene) & sevoflurane reacts with soda lime, hence not be used in closed (circle) system.
  • Most inhaled anesthetics are eliminated from lung.
  • Neurotoxicity is caused by dichloroacetylene involving most commonly 5th CN.
  • Sevoflurane produces nephrotoxic compound A.
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