1.7: Other inhalation anesthetics 

1.7.1 Isoflurane 

Isoflurane is a nonflammable colorless volatile anesthetic with a pungent odor. Its vapor pressure and boiling point is similar to halothane. Some have suggested using it in a halothane vaporizer but this is not recommended. Isoflurane is almost totally excreted by the lungs. 

Systemic effects of isoflurane 

• Central nervous system (CNS): Like other inhalational agents, it causes CNS depression and anesthesia but it has no convulsant effect. 
• Cardiovascular system (CVS): Little effect on myocardial contractility. Heart rhythm is stable. Isoflurane does not increase the sensitivity of the myocardium to adrenaline. 
• Respiratory system: Decrease in tidal volume and Increase in respiratory rate. 
• Muscle tone: Potentiates non-depolarizing muscle relaxants. 
• Liver and kidneys: Negligible changes in liver and renal function. 

Advantages of isoflurane 

• Rapid onset and recovery from anesthesia 
• No convulsant effect on central nervous system even with hypocapnia 
• Low risk of cardiac arrhythmias and no increased sensitivity to adrenaline 
• Low toxicity to liver and kidneys 
• Non explosive and non-flammable 

Disadvantages: Expensive 

1.7.2 Savoflurane 

This is a newer inhalational agent. It is non-flammable with a pleasant smell. It has a very low blood/gas solubility and provides the most rapid induction and recovery of all currently available inhalational agents. No pungency and rapid increases in alveolar anesthetic concentration make sevoflurane an excellent choice for smooth and rapid inhalation inductions in pediatric and adult patients. Like other volatile anesthetics, sevoflurane potentiates neuromuscular blocking agents. It does not sensitize the heart to catecholamine-induced arrhythmias. 

Systemic effects 

• Cardiovascular system: mildly depresses myocardial contractility. Systemic vascular resistance and arterial blood pressure decline slightly. 
• Central nervous system: Causes slight increases in CBF and intracranial pressure at normocarbia. 
• Neuromuscular: Produces adequate muscle relaxation for intubation of children following an inhalation induction. 
• Renal and hepatic: Reduce hepatic and renal blood flow 

Advantages of sevoflurane 

• Rapid induction 
• Rapid recovery 
• Minimum cardiovascular effects 

Disadvantages

• High cost 

1.7.3: Enflurane 

• It is stable, nonflammable liquid ,Pungent odor with MAC of1.68% 

Systemic Effects of enflurane 

• Potent inotropic and chronotropic depressant and decreases systemic vascular resistance-- lowers blood pressure and conduction dramatically 
• Inhibits sympathetic baroreflex response 
• Sensitizes myocardium to effects of exogenous catecholamine—arrhythmias 
• espiratory drive is greatly depressed-- central and peripheral responses 
• Increases dead space 
• produces hypercarbia in spontaneously breathing patient 
• Metabolism one-tenth that of halothane-- does not release quantity of hepatotoxic metabolites 
• Metabolism releases fluoride ion-- renal toxicity 
• Seizure