Substance:

MOA:

CI:

Effects of substances:

Halothane

Balance between strengthening inhibitory and weakening of excitatory circuits in SSS.

No longer often used due to hepatotoxicity and newer drugs.

CNS:              

Rapid smooth induction, Stage 2 = absent, cerebral blood flow + increased intracranial pressure

Autonomic :

Bradycardia

CVS:              

Blood pressure lowered, Sensitizes myocardium for arrhythmogenic effects of catecholamines.

Respiratory system :

Not saliva-bronchial secretions or coughing.

Musculoskeletal:

"MUSCLE TWITCHING"

Skeletal muscle-relaxing effects Stage III

Increase operation of non-depolarizing effects.

Reduces action of depolarizing effects e.g.  middle like succinylcholine)

Post-operative → hypoxia

Uterus:                      

Reduced muscle contraction that causes external turning of baby.           

Liver : Hepatotoxic, is metabolized by the liver.( Rare and unpredictable)

Enflurane

(Drugs strengthen the inhibitory lanes and weaken the excitatory lanes).

No longer use so often but use for maintenance. .

CNS:

Fast,smooth induction convulsions sometimes, NOT epileptics.

CVS:

No sensitization of the myocardium, less ↓ than

Halothane.

Respiratory:

More↓ than Halothane

Isoflurane

Drugs react with lipid component (Drugs are very lipid soluble ) of the cell membrane:

• Disturbance of membrane channels

• Direct activation v GABA – A receptors

More ideal remedy than halothane and enflurane. Replaced the above 2 mainly.  Not in patients who have to breathe spontaneously. Mainly maintenance

CNS:

Faster induction + recovery than Halothane.

CVS:

Less ↓ than Halothane + Enflurane No sensitization of myocardium.

Respiratory:

Potent ↓ effect. Strengthens because of potent skeletal muscle relaxing effect.

Desflurane

Different neurons – different sensitivities:

E.g. Dorsal horn cells of the spinal cord are particularly sensitive to inhalation drugs, brain stem neurons are quite resistant against effects of drugs.

Even more ideal than Isoflurane or sevoflurane.

Potential to be used for various surgical procedures.

Because of effect on resp. → NOT as induction.

CNS:

Even faster induction + recovery than Isoflurane, ↑ cerebral blood flow and intracranial pressure.

CVS:

Less ↓ than Halothane + Enflurane.

Respiratory:

Strong smell, irritate airways, if used as induction drug

→ cough, shortness of breath and laryngospasm.

Sevoflurane

Induction and maintenance.

Effects similar to Desflurane, less irritation of airways

Potentiate the effects of the non-depolarising muscle relaxants like the other halogenated ethers.

Undergoes metabolism + chemically unstable

N2O (Inorganic laugh gas)

Status

As additive drug in anaesthesia.

Single drug for short dental procedures e.g. extractions

Inorganic gas

CNS

Weak anaesthetic, potent analgesic, amnesia

CVS :

No effect

Resp. :

Pure N2O → hypoxia, always mix with O2 or air. Recovery phase: N2O fast

diffusion from blood to alveoli, ↓ O2 pressure, → hypoxia

No skeletal muscle relaxation

Methoxyflurane