Isoflurane respiratory effects

Desflurane is less potent than the other fluorinated anesthetics having MAC values of 5.7 to 8.9% in animals (76,85), and 6% to 7.25% in surgical patients. The respiratory effects are similar to isoflurane. Heart rate is somewhat increased and blood pressure decreased with increasing concentrations. Cardiac output remains fairly stable. Desflurane does not sensitize the myocardium to epinephrine relative to isoflurane (86). EEG effects are similar to isoflurane and muscle relaxation is satisfactory (87). Desflurane is not metabolized to any significant extent (88,89) as levels of fluoride ion in the semm and urine are not increased even after prolonged exposure. Desflurane appears to offer advantages over sevoflurane and other inhaled anesthetics because of its limited solubiHty in blood and other tissues. It is the least metabolized of current agents. 

Respiratory effects. Isoflurane causes respiratory depression the respiratory rate increases, tidal volume decreases, and the minute volume is reduced. The ventilatory response to carbon dioxide is diminished. Although it irritates the upper airway it is a bronchodilator. 

Steffey E P, Howland D Jr 1980 Comparison of circulatory and respiratory effects of isoflurane and halothane anesthesia in horses. American Journal of Veterinary Research 41 821-825... 

Respiratory System The respiratory effects of enflurane are similar to those of halothane. Enflurane produces a greater depression of the ventilatory responses to hypoxia and hypercarbia than do either halothane or isoflurane and, like other inhalational anesthetics, is an effective bronchodilator. 

This is also a new compound and undergoing clinical trial. It is noninflammable, non-irritant agent. It produces more rapid induction and termination of anaesthesia than observed with other inhalational agents. The respiratory and circulatory effects of sevoflurane resemble those of isoflurane. 

Sevoflurane is a chemical analogue of isoflurane. It is less chemically stable than the other volatile anaesthetics in current use. About 3% is metabolised in the body and it is degraded by contact with carbon dioxide absorbents, such as soda lime. The reaction with soda lime causes the formation of a vinyl ether (Compound A), which may be nephrotoxic. Sevoflurane is less soluble than isoflurane and is very pleasant to breathe, which makes it an excellent choice for inhalational induction of anaesthesia, particularly in children. The respiratory and cardiovascular effects of sevoflurane are very similar to isoflurane. 

In ponies, desflurane (MAC) caused a decrease in arterial blood pressure and systemic vascular resistance while heart rate and cardiac index were not changed significantly (Clarke et al 1996). Increasing the concentration of desflurane to 1.3 times MAC resulted in further depression of the arterial blood pressure and a significant decrease in the cardiac index, attributed to the onset of cardiac depression at higher concentrations (Clarke et al 1996). Desflurane also results in respiratory depression there is a significant increase in PaC02 at MAC (Clarke et al 1996). In other species, the cardiopulmonary effects of desflurane are considered to be approximately equal to those of isoflurane, but a direct comparison of desflurane and other inhalation anesthetics has not yet been carried out in the horse. 

Respiratory System Patients spontaneously breathing isoflurane have a normal respiration rate but a reduced tidal volume, resulting in a marked reduction in alveolar ventilation and an increase in arterial CO tension. Isoflurane depresses the ventilatory response to hypercapnia and hypoxia. While an effective bronchodilator, isoflurane also is an airway irritant and can stimulate airway reflexes during induction, producing coughing and laryngospasm. 

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