Desflurane 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. 

Desflurane does not have a marked bronchodilator effect and in cigarette smokers it is associated with significant bronchoconstriction. In clinical practice, both humidification of inspired gases and opioids are thought to reduce airway irritability but even at moderate concentrations (2 MAC), desflurane is more likely to cause coughing than sevoflurane. In common with other volatile agents, desflurane causes dose-related respiratory depression. Tidal volume is reduced and respiratory rate increases, initially. As inspired concentrations of desflurane increase, the trend is to hypoventilation and hypercardia and apnoea is to be expected at concentrations of 1.5 MAC or greater. 

INHALATIONAL- HALOTHANE TERBUTALINE, THEOPHYLLINE Cases of arrhythmias when these bronchodilators are co-administered with halothane Possibly due to sensitization of the myocardium to circulating catecholamines by the volatile anaesthetics to varying degrees Risk of cardiac events is higher with halothane. Desflurane is irritant to the upper respiratory tract, and t secretions can occur and are best avoided in patients with bronchial asthma. Sevoflurane is non-irritant and unlikely to cause serious adverse effects... 

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 As with halothane and enflurane, desflurane causes a concentration-dependent increase in respiratory rate and a decrease in tidal volume. At concentrations <1 MAC, the net effect is to preserve minute ventilation at concentrations >1 MAC, minute ventilation is markedly depressed, resulting in elevated arterial CO tension (Pa -Q ). Patients spontaneously breathing desflurane at concentrations greater than 1.5 MAC have extreme elevations of Pa. and may become apneic. Desflurane is a bronchodUator it also is a strong airway irritant and can cause coughing, breath-holding, laryngospasm, and excessive respiratory secretions. Thus, desflurane is not used for induction of anesthesia. 

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