Fink Effect

Short description: Changes of oxygen partial pressure in the pulmonary alveoli caused by a soluble anesthetic gas

The Fink effect, also known as "diffusion anoxia",^[1] "diffusion hypoxia",^[2] or the "second gas effect",^[3] is a factor that influences the pO₂ (partial pressure of oxygen) within the pulmonary alveoli. When water-soluble gases such as anesthetic agent N₂O (nitrous oxide) are breathed in large quantities they can be dissolved in body fluids rapidly. This leads to a temporary increase^{[clarification needed]} in both the concentrations and partial pressures of oxygen and carbon dioxide in the alveoli.

The effect is named for Bernard Raymond Fink (1914–2000), whose 1955 paper first explained it.^[1]^[4] When a patient is recovering from N₂O anaesthesia, large quantities of this gas cross from the blood into the alveoli (down its concentration gradient) and so for a short period of time, the O₂ and CO₂ in the alveoli are diluted by this gas. A sufficiently large decrease in the partial pressure of oxygen leads to hypoxia, especially if the patient hypoventilates (which allows more time for evolving nitrous to dilute alveolar oxygen each breath).^[5] Nonetheless, this effect only lasts a couple of minutes and hypoxia can be avoided by increasing the fractional inspired oxygen concentration when recovering from N₂O administration.^[6] It is for this reason that Entonox, a 50:50 gaseous mixture of nitrous oxide and oxygen, is suitable for use by para-medical staff such as ambulance officers: it provides sufficient nitrous oxide for pain relief with sufficient oxygen to avoid hypoxia.^[7]^[8]

References

↑ ^1.0 ^1.1 J. Roger Maltby (2002). Notable Names in Anaesthesia. Royal Society of Medicine Press. p. 63. ISBN 978-1-85315-512-3. https://books.google.com/books?id=Yc4_uLDkzgAC&q=Fink-effect nitrous&pg=PA63.
↑ S. Ahanatha Pillai (2007). Understanding Anaesthesiology. Jaypee Brothers Publishers. p. 101. ISBN 978-81-8448-169-3. https://books.google.com/books?id=rCvEJibQstcC&q=Fink-effect hypoxia&pg=PA101.
↑ Steven M. Yentis; Nicholas P. Hirsch; Gary B. Smith (2009). Anaesthesia and Intensive Care A–Z: An Encyclopedia of Principles and Practice. Elsevier Health Sciences. ISBN 978-0-443-06785-3. https://books.google.com/books?id=kxxDYTV7DqUC&q="third gas effect" fink&pg=PT534.
↑ Bernard R. Fink (1955). "Diffusion Anoxia". Anesthesiology 16 (4): 511–519. doi:10.1097/00000542-195507000-00007. PMID 13238868.
↑ S. EINARSSON (1993). "Nitrous Oxide Elimination and Diffusion Hypoxia During Normo- and Hypoventilation". British Journal of Anaesthesia 71 (2): 189–93. doi:10.1093/bja/71.2.189. PMID 8123390.
↑ Andrew B. Lumb; John F. Nunn (2005). Nunn's Applied Respiratory Physiology (6th ed.). Elsevier/Butterworth Heinemann. p. 169. ISBN 978-0-7506-8791-1. https://books.google.com/books?id=29hqAAAAMAAJ&q=Fink-effect++intitle:Respiratory+intitle:Physiology+inauthor:Nunn.
↑ "Entonox". 26 January 2009. http://www.frca.co.uk/article.aspx?articleid=100364.
↑ Joanne D. Fisher; Simon N. Brown; Matthew W. Cooke (October 2006). UK Ambulance Service Clinical Practice Guidelines (2006). Joint Royal Colleges Ambulance Liaison Committee. ISBN 1-84690-060-3. http://www2.warwick.ac.uk/fac/med/research/hsri/emergencycare/prehospitalcare/jrcalcstakeholderwebsite/guidelines/clinical_guidelines_2006.pdf. Retrieved 27 February 2018.

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[maltby-1] 1.0 ^1.1 J. Roger Maltby (2002). Notable Names in Anaesthesia. Royal Society of Medicine Press. p. 63. ISBN 978-1-85315-512-3. https://books.google.com/books?id=Yc4_uLDkzgAC&q=Fink-effect nitrous&pg=PA63.

[2] S. Ahanatha Pillai (2007). Understanding Anaesthesiology. Jaypee Brothers Publishers. p. 101. ISBN 978-81-8448-169-3. https://books.google.com/books?id=rCvEJibQstcC&q=Fink-effect hypoxia&pg=PA101.

[3] Steven M. Yentis; Nicholas P. Hirsch; Gary B. Smith (2009). Anaesthesia and Intensive Care A–Z: An Encyclopedia of Principles and Practice. Elsevier Health Sciences. ISBN 978-0-443-06785-3. https://books.google.com/books?id=kxxDYTV7DqUC&q="third gas effect" fink&pg=PT534.

[4] Bernard R. Fink (1955). "Diffusion Anoxia". Anesthesiology 16 (4): 511–519. doi:10.1097/00000542-195507000-00007. PMID 13238868.

[5] S. EINARSSON (1993). "Nitrous Oxide Elimination and Diffusion Hypoxia During Normo- and Hypoventilation". British Journal of Anaesthesia 71 (2): 189–93. doi:10.1093/bja/71.2.189. PMID 8123390.

[6] Andrew B. Lumb; John F. Nunn (2005). Nunn's Applied Respiratory Physiology (6th ed.). Elsevier/Butterworth Heinemann. p. 169. ISBN 978-0-7506-8791-1. https://books.google.com/books?id=29hqAAAAMAAJ&q=Fink-effect++intitle:Respiratory+intitle:Physiology+inauthor:Nunn.

[7] "Entonox". 26 January 2009. http://www.frca.co.uk/article.aspx?articleid=100364.

[8] Joanne D. Fisher; Simon N. Brown; Matthew W. Cooke (October 2006). UK Ambulance Service Clinical Practice Guidelines (2006). Joint Royal Colleges Ambulance Liaison Committee. ISBN 1-84690-060-3. http://www2.warwick.ac.uk/fac/med/research/hsri/emergencycare/prehospitalcare/jrcalcstakeholderwebsite/guidelines/clinical_guidelines_2006.pdf. Retrieved 27 February 2018.

v t e Anesthesia and anesthesiology
Types	General Sedation Twilight anesthesia Local Topical Intercostal nerve block Neuraxial blockade Spinal Epidural Dental Inferior alveolar nerve
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
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History	ACE 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 Royal College of Anaesthetists Association of Veterinary Anaesthetists Australian and New Zealand College of Anaesthetists Australian Society of Anaesthetists International Anesthesia Research Society
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Fink Effect

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