Loading....
Coupon Accepted Successfully!

 

Systemic Effect of inhalational agents

  1. Bronchial muscles - All are bronchodilators
     
    Maximum - Halothane (agent of choice for asthma patients)
  2. Pulmonary vascular resistance --> All (but left atrial pressure, so pulmonary blood flow not compromised.
  3. Mucociliary function - All agents the ciliary movement except ether
  4. Respiration: All agents tidal volume but frequency
    1. Max. with halothane & minimum with ether
    2. All ventilatory responses (like pCO2) are blunted
  5. Effects on CVS
    1. N2O - No effect on CVS
    2. All Other agents decrease mean arterial pressure by 25%
    3. Cardiac Output (CO)- (Maximum fall in CO) Halothane > Enflurane > Isoflurane > Desflurane
    4. Systemic Vascular Resistance (SVR)- (Maximum fall in SVR) Isoflurane > enflurane > halothane

Extra Edge

 

Isoflurane is agent of choice for controlled hypotension

  1. Baroreceptor reflex- Halothane > Enflurane > Isoflurane
    1. Because of the above reasons, i.e maintenance of CO, minimum effect on baroreceptor reflex,
    2. Isoflurane is agent of choice for cardiac patients except ischemic patient.
  2. All potentiate neuromuscular blocking drugs.
     
    Desflurane > sevoflurane > enflurane > halothane
  3. All increases post operative nausea vomiting
    1. Metabolism
      1. All inhalational agents undergo oxidation (which may be dealkylation or Dehalogenation) except halothane which also undergoes reduction
      2. Some of the inhalation agents are metabolized by cytochrome P450 enzyme in the liver cell..
Cyclopropane, trichloroethylene and methoxyflurane are no longer used.
 
Table 1: Comparative properties of various Inhalational agents
 
Anesthetic Boiling
Point (oC)
Inflamma-
bility
Irritancy
(odour)
Oil: Gas
partition
co-efficient
Blood: Gas partition co-efficient* MAC (%) Induction Muscle
relaxation
1. Ether 35 Infl. + Explosive + + +
(Pungent)
6 5 12 .1 1.9 Slow Very good
2. Halothane 50 Non infl. -
(Pleasant)
254 2.3 0.75 Interm. Fair
3. Enflurane 56 Noninfl. - 98 1.9 1.68 Interm. Good
4. Isoflurane 48 Noninfl. +
(Nt pleasant)
99 1.4 1.2 Fast Good
5. Desflurane 24 Noninfl. + (Unpleasant)
-
19 0.42 6.0 Fast Good
6. Sevoflurane 59 Noninfl.   50 0.68 2.0 Fast Good
7. N2O Gas Noninfl. (Pleasant)
-
1.4 0.47 105 Fast Poor

Table 2: Effect of Inhalational Agents on Different Organ System
  HALOTHANE ISOFLURANE SEVOFLURANE DESFLURANE
CENTRAL NERVOUS SYSTEM Decreases cerebral metabolic oxygen requirement(CMOR).
INCREASES cerebral blood flow(CBF).
DECREASES ICP
EEG activity decreases.
Decreases cerebral metabolic oxygen requirement (CMOR).
INCREASES cerebral blood flow (CBF).
DECREASES ICP
EEG activity decreases.
Decreases cerebral metabolic oxygen requirement (CMOR).
INCREASES cerebral blood flow (CBF).
DECREASES ICP
EEG activity decreases.
Decreases cerebral metabolic oxygen requirement (CMOR).
INCREASES cerebral blood flow (CBF).
DECREASES ICP
EEG activity decreases.
CARDIOVASCULAR SYSTEM Direct myocardium depressant.
decreases SA node contractility (bradycardia).
Decreased cardiac ouput
Decreased blood pressure.
Sensitizes myocardium to arrythomogenic action of cathecholamine.
Decreases systemic vascular resistance.
Decreased blood pressure.
Reflex sympathetic tachycardia
Decreases systemic vascular resistance.
Decreased blood pressure.
Reflex sympathetic tachycardia
Decreases systemic vascular resistance.
Decreased blood pressure.
Reflex sympathetic tachycardia
RESPIRATORY SYSTEM Respiratory centre depression.
Blunting of hypoxic hypercapnic reflex.
best bronchodilator.
hypoxic pulmonary drive blunted.
Respiratory centre depression.
Blunting of hypoxic hypercapnic reflex.
best bronchodilator.
hypoxic pulmonary drive blunted
Respiratory centre depression.
Blunting of hypoxic hypercapnic reflex.
best bronchodilator.
hypoxic pulmonary drive blunted
Respiratory centre depression.
Blunting of hypoxic hypercapnic reflex.
best bronchodilator.
hypoxic pulmonary drive blunted
HEPATIC SYSTEM Autoimmune hepatitis.
portal blood flow decreased effectively.
Minimal effect on portal blood flow. Minimal effect on portal blood flow. Minimal effect on portal blood flow.
RENAL SYSTEM Renal blood flow minimally decreased. Renal blood flow minimally decreased. Renal blood flow minimally decreased. Renal blood flow minimally decreased.




Test Your Skills Now!
Take a Quiz now
Reviewer Name