End-tidal Anesthetic Concentration: Monitoring, Interpretation, and Clinical Application

Abstract

Age-adjusted fraction of minimum alveolar concentration derived from end-tidal anesthetic partial pressure measurement remains a useful drug advisory display to help prevent awareness if interpreted with proper understanding of the quantal and probabilistic nature of minimum alveolar concentration, semantics, drug interactions, and hysteresis.

The science behind banning desflurane

“…Proper dosing of opioids and other adjuvants will allow the target-agent concentration to be lowered, thereby reducing waste even further. 9 Recycling or destruction of potent inhaled anaesthetics eliminated via the scavenging systems are being explored. However, these techniques are no different for desflurane than for sevoflurane and should be introduced universally, irrespective of what agent is used.…”

“…12,13 The faster emergence after desflurane anaesthesia is entirely predictable based on calculated central nervous system time constants. 9 However, the clinical impact of this is minimal because the 2 to 3 min slower emergence after sevoflurane anaesthesia can easily be overcome by turning off the vapouriser 2 to 3 min sooner when sevoflurane is used. Discharge times from the post anaesthesia care unit do not differ between desflurane and sevoflurane.…”

“…Proper dosing of opioids and other adjuvants will allow the target-agent concentration to be lowered, thereby reducing waste even further 9 . Recycling or destruction of potent inhaled anaesthetics eliminated via the scavenging systems are being explored.…”

Anesthetic MAC: Origin, Utility, and Nomenclature Revisited

“…Jan F. A. Hendrickx and Andre M. De Wolf explicate the foundations of MAC, the underlying physiology and pharmacology, the clinical application, and the terminology in a Clinical Focus Review. 3 They explore definitions and determination of MAC, types of MAC (MAC awake , MAC unconsciousness , MAC immobility , MAC BAR ), factors affecting MAC, fraction of a MAC delivered to a patient (fMAC), relationship between fMAC and clinical effect, and drug interactions or other factors affecting fMAC. They also present pragmatic approaches to using MAC and fMAC in clinical care.…”

“…Hendrickx and De Wolf identify that the term “MAC” is thus plagued with semantic issues. 3 Should the “M” in MAC refer to “minimal” or “median”? In addition, while alveolar and end-tidal terms have been used interchangeably, they also point out that alveolar and end-tidal anesthetic concentrations (what we actually measure) may not be the same.…”