Blood–gas partition coefficient

Blood–gas partition coefficient, also known as Ostwald coefficient for blood–gas,^[1] is a term used in pharmacology to describe the solubility of inhaled general anesthetics in blood.^[2] The coefficient is defined as the ratio of the concentration in blood to the concentration in gas that is in contact with that blood, when the partial pressure in both compartments is equal. The coefficient, thence, has no units. The concentration of the anesthetic in blood includes the portion that is undissolved in plasma and the portion that is dissolved (bound to plasma proteins). The more soluble the inhaled anesthetic is in blood compared to in air, the more it binds to plasma proteins in the blood and the higher the blood–gas partition coefficient.

It is inversely related to induction rate.

Newer anesthetics (such as desflurane) typically have smaller blood-gas partition coefficients than older ones (such as ether); these are preferred because they lead to faster onset of anesthesia and faster emergence from anesthesia once application of the anesthetic is stopped.^[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 the concentration required to produce anaesthetic effects - an inverse indicator of anaesthetic potency.

Inhalational anaesthetics

^[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 (Forane)	1.15	1.4	97	2.6	4.0	45
Sevoflurane (Ultane)	2	0.65	42	1.7	3.1	48
Desflurane (Suprane)	5.8	0.42	18.7	1.3	2.0	27

Partition coefficients at 37° C.

References

↑ "Ostwald solubility coefficient". Drugs.com. Retrieved 1 February 2014.
↑ Magee, Patrick; Tooley, Mark (22 September 2011). The Physics, Clinical Measurement and Equipment of Anaesthetic Practice for the FRCA. Oxford University Press. p. 133. ISBN 978-0-19-959515-0.
↑ Grossherr, M; Hengstenberg, A; Dibbelt, L; Igl, BW; Noel, R; Knesebeck, Av; Schmucker, P; Gehring, H (Oct 2009). "Blood gas partition coefficient and pulmonary extraction ratio for propofol in goats and pigs.". Xenobiotica 39 (10): 782–7. doi:10.1080/00498250903056109. PMID 19548775.
↑ Bergadano, A; Lauber, R; Zbinden, A; Schatzmann, U; Moens, Y (Aug 2003). "Blood/gas partition coefficients of halothane, isoflurane and sevoflurane in horse blood". British journal of anaesthesia 91 (2): 276–8. doi:10.1093/bja/aeg151. PMID 12878628.
↑ Battino, Rubin (1984). "The Ostwald coefficient of gas solubility". Fluid Phase Equilibria 15 (3): 231–240. doi:10.1016/0378-3812(84)87009-0.
↑ Nagelhout, J.J. (2014). Pharmacokinetics of Inhalation Anesthetics. Nurse anesthesia (5th ed., ). p. 79.
↑ Morgan, G.E. (2013). Clinical Anesthesiology (5th ed., ). p. 156.

Anesthesia (outline)

Types	General Spinal Epidural Conduction anesthesia Local Topical Intercostal nerve block Sedation / Twilight anesthesia Dental (Inferior alveolar nerve) Neuroleptanalgesic anesthesia

Techniques	Airway management Anesthesia provision in the US Arterial catheter Bronchoscopy Capnography Dogliotti's principle Drug-induced amnesia Intraoperative neurophysiological monitoring Nerve block Penthrox inhaler Tracheal intubation

Scientific Principles	Blood–gas partition coefficient Concentration effect Fink effect Minimum alveolar concentration Second gas effect

Measurements	ASA physical status classification system Baricity Bispectral index Direct Fick method Entropy monitoring Fick principle Goldman index Guedel's classification Mallampati score Neuromuscular monitoring Thyromental distance

Instruments	Anaesthetic machine Anesthesia cart Boyle's machine Gas cylinder Laryngeal mask airway Laryngeal tube Medical monitor Odom's indicator Relative analgesia machine Vaporiser Double-lumen endotracheal tube Endobronchial blocker

Drugs	Benzodiazepine Etomidate General anaesthetic Inhalational anaesthetic Infiltration analgesia Ketamine Local anesthetic Methohexital Methoxyflurane Midazolam Neuraxial blockade Opiate Propofol Thiopental Thiopentone

Complications	Emergence delirium Allergic reactions Anesthesia awareness Local anesthetic toxicity Malignant hyperthermia Perioperative mortality Postanesthetic shivering Postoperative nausea and vomiting Postoperative residual curarization

Fields of study	Cardiothoracic Geriatric Oral sedation dentistry

Professions	Anesthesiologist Anesthesiologist assistant Nurse anesthetist Operating Department Practitioners Certified Anesthesia Technician Certified Anesthesia Technologist Anaesthetic technician

History	A.C.E. mixture Helsinki Declaration for Patient Safety in Anaesthesiology History of general anesthesia History of neuraxial anesthesia History of tracheal intubation

Organizations	American Association of Nurse Anesthetists American Society of Anesthesia Technologists & Technicians American Society of Anesthesiologists Anaesthesia Trauma and Critical Care Association of Anaesthetists of Great Britain and Ireland Association of Veterinary Anaesthetists Australian and New Zealand College of Anaesthetists Australian Society of Anaesthetists International Anesthesia Research Society

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