Desflurane

Desflurane :

• Synthesized  in 1959-1966
• First use in human 1988 available for general use in clinical start from 1993
• The structure of Desflurane is similar to isoflurane   

Physical properties :

• It is colorless stored in amber colored bottle without preservative
• Not broken down by soda lime, light or metal 
• Non-flammable 
• Pungent smell 
• MAC with oxygen is 6%
• MAC is 3% with 60% nitrous oxide
• Mac in children 9%  (7 with N20)
• Blood/gas solubility co-eff 0.42
• Oil/gas solubility co-eff 18.7

Metabolism :

• Approximately 0.02% of the inhaled desflurane is metabolized in the body by deflurination to trifluro-acetic acid which is excreted in urine 
• It is delivered through special vaporizer (TEC6) It is a popular anesthetic for day care surgery.
• Induction and recovery is fast, cognitive and motor impairment are short lived
• It irritates the air passages producing cough and Laryngospasam.

ACTION ON RESPIRATORY SYSTEM :

• Respiratory depression decrease tidal volume increase respiratory rate 
• Decrease ventilatory response to increase CO2
• Irritant to air way not suitable for inhalational induction but best agent for maintenance 
• Produce coughing, breath holding and Laryngospasam 
• Increased salivation  

Action on CVS :

• Dose dependent decrease systemic vascular resistance which decrease arterial pressure 
• Decrease myocardial contractility
• At low concentration heart rate remain normal but at high concentration heart rate increase 
• In the absence of pre-medication increase sympathetic activity 
• Do not sensitize myocardium to catecholamine  
• Cardiac output remains relatively unchanged  

Action on CNS:

• Like the other volatile anesthetics,desflurane directly vasodilates the cerebral vasculature,
• Increasing CBF, cerebral blood volume, and intracranial pressure at normotension and normocapnia
• decrease in cerebral vascular resistance is a marked decline in the cerebral metabolic rate of oxygen (CMRO 2 )
• It not cause seizuers activity at any level  

Action on Renal system :

• There is no evidence of any signifi cant nephrotoxic effects caused by exposure to desflurane. 
• However as cardiac output declines, decreases in urine output and glomerular filtration should be expected with desflurane and all other anesthetics

Action on hepatic system :

• Hepatic function tests are generally unaffected by desflurane, assuming that organ perfusion is maintained perioperatively. 
• Desflurane undergoes minimal metabolism, therefore the risk of anesthetic- induced hepatitis is likewise minimal. 
• As with Isoflurane and sevoflurane, hepatic oxygen delivery is generally maintained.

Advantages :

• Rapid recovery 
• Non toxic to liver and kidney 
• Ideal agent for maintenance 
• No convulsion  
• Low blood/gas solubility 

Disadvantage:

• Desflurane, more than other volatile anesthetics, is degraded by desiccated CO2 absorbent (particularly barium hydroxide lime, but also sodium and potassium hydroxide) into potentially clinically significant levels of carbon monoxide.
• Carbon monoxide poisoning is difficult to diagnose under general anesthesia, but the presence of carboxyhemoglobin may be detectable by arterial blood gas analysis or lower than expected pulse oximetry readings