Isoflurane inhalation induction

A rapid Isoflurane inhalation induction is possible with isoflurane because of low blood/gas solubility coefficient. It has a pungent odour, patients complain of burning sensation in the airway though there is no increase in airway reflexes or secretions. So a smoother induction is seen with halothane or sevoflurane which are preferred for inhalational induction.

Recovery: After Isoflurane inhalation induction is discontinued, emergence is prompt. The incidence of nausea and vomiting is similar to other volatile agents. Indications for isoflurane are in cases where disturbance in cardiac rhythi is likely, neurological patients with raised ICP, preexisting liver or renal disease or frequent anaesthesia. Isoflurane inhalation induction is avoidable in multiple coronary vessel disease or in cases where tachycardia is harmful.

Miller’s Anesthesia 7th Edition says the following about Isoflurane inhalation induction –

Isoflurane, an isomer of enflurane, is defluorinated much less than enflurane is. Because of the resistance to defluorination and the decreased likelihood of other toxicities, prolonged isoflurane administration has been investigated for use outside the operating room.

Isoflurane was investigated for its effectiveness in long-term sedation of patients maintained on mechanical ventilation. In the first study, the highest serum fluoride concentration was measured in a 2-year-old child who received 73 MAC-hours of isoflurane and had a serum fluoride level of 37.4 µmol/L.

In the second study, pediatric patients undergoing mechanical ventilation received isoflurane for 13 to 497 MAC-hours. The highest serum F- concentration was 26.1 µmol/L, with no alterations in serum creatinine or osmolality.

From these studies we can safely conclude that isoflurane can be administered for very long periods without producing clinically significant serum fluoride concentrations; however, influences on metabolism and renal and hepatic function should be carefully considered.



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