Types of Inhalational Anaesthesia and Their Properties

1. Ether 
   • On its own, ether can cause unconsciousness, forgetfulness, analgesia, and immobility. • It has a gradual induction and emergence.  It is no longer in use.
2. Nitrous Oxide
   • Nitrous oxide is a less potent medication that is nonetheless used in conjunction with other medications to maximize their effects. Unlike ether, nitrous oxide has a rapid induction and emergency.
3. Chloroform
   • Because of cardiac arrhythmias and hepatotoxicity, chloroform is no longer utilized.

Blood Gas Solubility Coefficient (BG)

The blood gas solubility coefficient indicates how quickly the body absorbs the substance. It serves as a marker for the emergence and induction rates.  The relationship between BG and the rates of induction and emergence is inverse.

Minimal Alveolar Concentration

The concentration of the inhalational agent that, in 50% of the tested population, results in no reaction or movement upon skin incision is known as the minimum alveolar concentration. The indicator of an inhalation agent's potency is the minimum alveolar concentration.
Potency is inversely correlated with MAC.

Pungency

Pungenency is defined as an offensive or unpleasant odor. Sevoflurane and halothane are examples of inhalational drugs with minimal pungency that are pleasant to the patient and are therefore recommended for inducing anesthesia. 
Desflurane is a very strong anesthetic that irritates the respiratory system and is unpleasant for the patient. As a result, it is not recommended for use as an induction agent, however it can be used as a maintenance agent.

4. Nitrous Oxide: Nitrous oxide is not a suitable agent for inducing anesthesia due to its high Minimum Alveolar Concentration of 104. It offers emergency and quick induction. Therefore, nitrous oxide can be utilized to induce anesthesia when mixed with other strong drugs.

There is a second gas impact in nitrous oxide. Nitrous oxide swiftly diffuses into the blood as soon as it and other agents enter alveoli, creating space inside the alveoli that allows more second gas to enter. Because nitrogen is not as soluble as nitrous oxide (30 times more soluble than nitrogen), nitrous oxide diffuses more into the tight spaces, increasing their volume and pressure.

In situations such as pneumothorax, small bowel blockage, retinal surgery, and middle ear surgery, nitrous oxide is contraindicated.

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Enigma 1: Evaluation of Nitrous Oxide in Gas Mixture for Anesthesia

A 2007 clinical investigation found that using nitrous oxide for longer than two hours increased the risk of problems following surgery, including wound infections, nausea, and vomiting after the procedure.

Enigma 2: Evaluation of Nitrous Oxide and Gas Mixture for Anesthesia

There is a modest increase in the risk of post-operative nausea and vomiting when nitrous oxide is administered, but overall there is no higher risk of post-operative sequelae, according to 2014 clinical trial results.

5. Isoflurane

Isoflurane is the most often used powerful anesthetic medication. Compared to halothane, it has less metabolism, less cardiac output loss, and less catecholamine sensitization. 
Isoflurane is not a preferred agent for induction of anesthesia because of its strong odor, but it can be used for maintenance of anesthesia. • It is not recommended for use in patients with coronary artery disease because it raises heart rate and consequently increases myocardial oxygen consumption.

6.Sevoflurane                                                                        

Sevoflurane is superior than isoflurane; it has a low blood gas coefficient, meaning it induces and emerges quickly.  Decreased nausea and vomiting following surgery.  Because sevoflurane causes bronchodilatation and lowers airway pressure, it is a favored agent for inducing anesthesia in youngsters and is more comfortable. It is also preferred in cases of bronchial asthma and other bronchospasm problems.  Because sevoflurane has few side effects, it is also utilized in the treatment of cardiovascular disorders.

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Adverse Effect

Sevoflurane metabolism results in an increase in fluoride ion concentration.  In the presence of soda lime and the enzyme beta lyase, sevoflurane breaks down into compound A, which is harmful to rats' kidneys.  Because beta lyase activity in humans is so low, the possibility of nephrotoxicity is only speculative. 

7.Desflurane

Desflurane is the most volatile and least potent hydrocarbon-based anesthetic; as such, it is administered via a specialized electrically heated vaporizer. Its pungent odor makes it an unfavorable induction agent. Common side effects include tachycardia and hypertension. Desflurane has a low blood gas coefficient, meaning it has rapid induction and emergence.
Carbon monoxide is produced when desflurane, enflurane, or isoflurane come into contact with baralyme (in the presence of high temperatures and high concentrations of the medicines). 
When the equipment is not in use, the gas flow can be turned off to avoid this problem.

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