DRUG:

SYSTEM:

EFFECT:

Halothane

(1^st series standard)

Central nervous system:

Fast smooth muscle induction, stage II present.

↑ cerebral blood flow and ↑ intracranial pressure.

Autonomic:

Bradycardia ( decreased heart Rate)

Cardiovascular system:

Decreased blood pressure, Sensitised myocardium for arrhythmogenic effects of catecholamines.

Respiratory system:

No saliva, Bronchial secretions or cough.

Musculo-skeletal system:

Skeletal muscle relaxing effects in stadium III

↑ Action of the non-depolarizing muscle relaxants

↓ Action of the depolarizing skeletal muscle relaxants.

Post-operative shaking = lead to hypoxia

Uterus:

Decrease muscle contractions

Halothane was commonly used to promote the external twisting of the baby. If the baby is not in the correct position in the birth canal then they would turn the baby externally.

Liver:

Hepatotoxic (rare & unpredictable).

Be careful in patients with liver cirrhosis, and decreased liver functioning.

Enflurane

Central nervous system:

Fast, smooth induction convulsions.

Contra-indicated in epileptic patients.

Cardiovascular system:

No sensitisation of the myocardium.

Less oppressive than Halothane.

Respiratory system:

More suppressive than Halothane.

Isoflurane

Central nervous system:

Faster induction & recovery than Halothane

Cardiovascular system:

Less oppressive than Halothane

No sensitization of myocardium

Respiratory system:

MOST POTENT RESPIRATORY DEPRESSOR.

Potent ↓ effect

Skeletal muscle relaxing effects

Desflurane

Central nervous system:

Faster induction & recovery than Isoflurane

↑ Intracranial pressure

↑ cerebral blood flow

Cardiovascular effects

Less suppressive effect than Halothane & Enflurane

Respiratory system

Potent smell

Irritating in airways

If used as inducing agent, it causes a cough, SOB and laryngospasm

Sevoflurane

Effects similar to Desflurane, less irritation of airways.

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

Undergoes liver metabolism & chemically unstable. Caution in patients with reduced/ compromised liver function

Nitrous Oxide

(N₂O)

Central nervous system:

Weak anaesthetic, potent analgesic, amnesia

Cardiovascular system:

No effect

Respiratory system:

Pure N₂O causes hypoxia. Must always be mixed with O₂ or air.

Recovery phase: N₂O fast diffusion from the blood to the alveoli and is expired outside, ↓ O₂ pressure = hypoxia

Skeletal muscle relaxing effects:

No effect