Blood–gas partition coefficient
Blood–gas partition coefficient, also known as Ostwald coefficient for blood–gas,
It is inversely related to
Newer anesthetics (such as desflurane) typically have smaller blood–gas partition coefficients than older ones (such as ether); this leads to faster onset of anesthesia and faster emergence from anesthesia once application of the anesthetic is stopped, which may be preferable in certain clinical scenarios.[3][4] If an anesthetic has a high coefficient, then a large amount of it will have to be taken up in the body's blood before being passed on to the fatty (lipid) tissues of the brain where it can exert its effect.
The potency of an anesthetic is associated with its lipid solubility, which is measured by its oil/gas partition coefficient.[5]
Minimum alveolar concentration (MAC) is defined as the alveolar concentration of anesthetic gas that prevents a movement response in half of subjects undergoing a painful (surgical) stimulus; simplified, it is the exhaled gas concentration required to produce anaesthetic effects – an inverse indicator of anesthetic gas potency.
Inhalational anaesthetics
| Partition coefficients at 37 °C[6][7] | ||||||
|---|---|---|---|---|---|---|
| Anesthetic | MAC (%) | Blood/gas | Oil/gas | Brain/blood | Muscle/blood | Fat/blood |
| Nitrous oxide | 105 | 0.47 | 1.4 | 1.1 | 1.2 | 2.3 |
| Halothane | 0.74 | 2.4 | 224 | 2.9 | 3.5 | 60 |
| Isoflurane | 1.15 | 1.4 | 97 | 2.6 | 4.0 | 45 |
| Sevoflurane | 2 | 0.65 | 42 | 1.7 | 3.1 | 48 |
| Desflurane | 5.8 | 0.45 | 18.7 | 1.3 | 2.0 | 27 |
| Methoxyflurane | 0.2 | 12 | ||||
| Enflurane | 1.58 | 1.9 | ||||
References
- ^ "Ostwald solubility coefficient". Medical Dictionary.com. Retrieved 14 February 2020.
- ISBN 978-0-19-959515-0.
- S2CID 205462293.
- PMID 12878628.
- .
- ^ Nagelhout, J. J. (2014). Pharmacokinetics of Inhalation Anesthetics. Nurse anesthesia (5th ed.). p. 79.
- ^ Morgan, G. E. (2013). Clinical Anesthesiology (5th ed.). p. 156.
