Changes in blood flow distribution in equine lungs induced by anaesthesia.
Abstract: The distribution of blood flow to the lungs was measured with labelled microspheres injected into horses before and during anaesthesia. Anaesthesia was induced with glycerol guaiacolate ether and ketamine, and maintained with the spontaneous breathing of halothane in oxygen. In a preliminary group of six horses, flow distribution was observed during anaesthesia in sternal, dorsal and right lateral recumbency. In two other groups, each of four horses, the flow distribution with time during either sternal or right lateral recumbency was observed. A small, constant proportion of the 15 micron diameter microspheres bypassed the lungs. No increase in shunting with anaesthesia was detected. Blood flow distributed predominantly cranioventrally in the conscious horse in concordance with the expected effects of hydrostatic forces within the lung. In the anaesthetized horse a stable distribution rapidly developed whereby the flow was directed preferentially caudodorsally and evenly divided between the left and right lungs regardless of whether the horse was on its back, side or sternum. We conclude that an unidentified factor overrides gravitational effects on perfusion in the anaesthetized horse. If under anaesthesia, ventilation were distributed according to gravity, hypoxia would arise from this disassociation of ventilation from perfusion. The hypoxia would be most intense in dorsal recumbency, and least intense in sternal recumbency. This was reflected in the degree of hypoxaemia observed. A small but significant change in flow distribution with the phase of the respiratory cycle was detected in the conscious, standing horse.
Publication Date: 1985-04-01 PubMed ID: 3925493DOI: 10.1113/expphysiol.1985.sp002909Google Scholar: Lookup
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- Comparative Study
- Journal Article
- Research Support
- Non-U.S. Gov't
- Research Support
- U.S. Gov't
- Non-P.H.S.
Summary
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The research article is a study of how anesthesia changes blood flow distribution in horses’ lungs. It observes how these changes may potentially induce hypoxia, contributing to hypoxaemia under various anaesthetized conditions.
Methodology
- The study involved injecting labelled microspheres into horses to measure blood flow distribution in the lungs both before and during anaesthesia.
- Two different positions were observed for the anaesthetized horses: sternal (on their chest) and right lateral recumbency (on their right side).
- The anesthetic agents used were glycerol guaiacolate ether for induction, ketamine, and halothane in oxygen for maintenance.
- The process was observed in two groups of four horses and a preliminary group of six horses for comparison
Findings
- While a small, constant proportion of the injected microspheres bypassed the lungs, there was no detected increase in shunting due to anaesthesia.
- Under normal conditions, blood flow was predominantly cranioventral (toward the head and ventral side).
- Upon anaesthesia, the blood flow quickly adapted a new pattern. Flow primarily moved caudodorsal (toward the tail and dorsal side), with an even distribution between left and right lungs irrespective of the horse’s position.
- The change in blood flow suggests that an unknown factor overrides gravity’s effect on lung perfusion under anaesthesia.
Implications
- If ventilation were to follow gravity’s pull during anaesthesia, hypoxia, or the lack of sufficient oxygen, may occur due to this disconnection between ventilation and perfusion.
- The intensity of hypoxia depends on the position of the anaesthetized horse, being most severe in dorsal recumbency and least severe in sternal recumbency. This observation matches the level of hypoxaemia found in these conditions.
- A small but significant change in flow distribution was detected according to the respiratory cycle phase in conscious, standing horses, which might luminate further research on breathing pattern effects on blood flow distribution.
Cite This Article
APA
Dobson A, Gleed RD, Meyer RE, Stewart BJ.
(1985).
Changes in blood flow distribution in equine lungs induced by anaesthesia.
Q J Exp Physiol, 70(2), 283-297.
https://doi.org/10.1113/expphysiol.1985.sp002909 Publication
Researcher Affiliations
MeSH Terms
- Anesthesia, General
- Animals
- Carbon Dioxide / blood
- Cardiac Output
- Horses / physiology
- Oxygen / blood
- Posture
- Pulmonary Circulation
- Respiration
- Time Factors
Citations
This article has been cited 9 times.- Stefanik E, Drewnowska O, Lisowska B, Turek B. Causes, Effects and Methods of Monitoring Gas Exchange Disturbances during Equine General Anaesthesia.. Animals (Basel) 2021 Jul 9;11(7).
- Cerullo M, Driessen B, Douglas H, Hopster K. Changes in Arterial Blood Pressure and Oxygen Tension as a Result of Hoisting in Isoflurane Anesthetized Healthy Adult Horses.. Front Vet Sci 2020;7:601326.
- Youngblood CD, Hodgson DS, Beard WL, Song Y, Prakash P, Heflin LV. Effect of position on transdiaphragmatic pressure and hemodynamic variables in anesthetized horses.. Can J Vet Res 2020 Jul;84(3):205-211.
- Dupont J, Serteyn D, Sandersen C. Prolonged Recovery From General Anesthesia Possibly Related to Persistent Hypoxemia in a Draft Horse.. Front Vet Sci 2018;5:235.
- Niyom S, Mama KR, King M, Contino E, Ferris D, Valdes-Martinez A, Frisbie DD, McIlwraith W, Zumbrunnen J. Influence of changing lateral recumbency and mode of ventilation on the alveolar-arterial oxygen tension gradient and selected laboratory analytes in adult isoflurane anesthetized horses.. J Vet Med Sci 2018 Nov 1;80(10):1584-1589.
- Mosing M, Waldmann AD, MacFarlane P, Iff S, Auer U, Bohm SH, Bettschart-Wolfensberger R, Bardell D. Horses Auto-Recruit Their Lungs by Inspiratory Breath Holding Following Recovery from General Anaesthesia.. PLoS One 2016;11(6):e0158080.
- Karrasch NM, Hubbell JA, Aarnes TK, Bednarski RM, Lerche P. Comparison of cardiorespiratory variables in dorsally recumbent horses anesthetized with guaifenesin-ketamine-xylazine spontaneously breathing 50% or maximal oxygen concentrations.. Can Vet J 2015 Apr;56(4):387-92.
- Hubbell JA, Aarnes TK, Bednarski RM, Lerche P, Muir WW. Effect of 50% and maximal inspired oxygen concentrations on respiratory variables in isoflurane-anesthetized horses.. BMC Vet Res 2011 Jun 3;7:23.
- Donaldson LL. A review of the pathophysiology of exercise-induced pulmonary haemorrhage in the equine athlete.. Vet Res Commun 1991;15(3):211-26.
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