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The Journal of veterinary medical science2018; 80(10); 1584-1589; doi: 10.1292/jvms.18-0032

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.

Abstract: This study investigated the influence of changing recumbency and mode of ventilation over repeated anesthesias on the alveolar to arterial oxygen tension gradient (PO) and laboratory analytes in eight horses during a year-long imaging study. Anesthesia was induced with xylazine, diazepam or guaifenesin, and ketamine and maintained with isoflurane. Horses were positioned in right or left lateral recumbency for computed tomography. Ventilation was controlled during 47% of the anesthetics. Blood was sampled from an arterial catheter prior to (30 ± 5 min from connection to anesthetic circuit), within 5 min of changing lateral recumbency, and prior to circuit disconnection (24 ± 6 min after second sample) for measurement of pH, partial pressure of arterial oxygen (PaO) and partial pressure of arterial carbon dioxide, blood glucose and electrolytes. PO was calculated. Data from five anesthetic episodes for each horse were summarized as mean ± standard error and analyzed using a mixed-model ANOVA. t tests were used for pairwise comparisons (P<0.05). PaO decreased after turning (198 vs. 347 mmHg), then increased to 291 mmHg prior to disconnection. Correspondingly, PO was wider (252 vs.120 mmHg), and improved before disconnection (190 mmHg). Body temperature, ionized-Ca and blood glucose were lower, and Na was higher at the last time point. In conclusion, turning anesthetized horses decreases PaO and results in a widening PO suggesting a cautious approach in animals with pre-existing hypoxemia.
Publication Date: 2018-09-03 PubMed ID: 30175753PubMed Central: PMC6207512DOI: 10.1292/jvms.18-0032Google Scholar: Lookup
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  • Clinical Trial
  • Veterinary
  • Journal Article

Summary

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The research article discusses the impact that shifting recumbency (lying position) and variation in ventilation methods have on the alveolar-arterial oxygen tension gradient and laboratory markers in adult horses that are anesthetized using isoflurane over multiple sessions of anesthesia in a one-year study.

Study Setup and Procedure

  • The subjects of the study were eight horses that underwent repeated anesthesia within a year for imaging purposes.
  • The anesthesia procedure involved the use of xylazine, diazepam or guaifenesin, and ketamine for the induction, and isoflurane for maintenance throughout.
  • During the Computed Tomography (CT) scans, horses were positioned either in a right or a left lateral recumbency.
  • About 47% of the anesthetic sessions were controlled for ventilation.

Data Collection and Evaluation

  • Blood samples were taken prior to and after the change in lateral recumbency and before disconnecting the anesthetic circuit for measurement of various analytical factors, namely pH, partial pressure of arterial oxygen (PaO), partial pressure of arterial carbon dioxide, glucose levels in the blood and electrolytes.
  • The researchers calculated the alveolar-arterial oxygen tension gradient (PO), a marker of the efficiency of oxygen exchange from the lungs to the blood, from the collected information.
  • Data from five separate anesthetic episodes for each horse were averaged and standard errors were calculated.

Statistical Analysis

  • An advanced statistical method, the mixed-model ANOVA, was employed to analyze the gathered data, corroborating the results via t-tests, standard tests of statistical significance.

Key Findings

  • Following a change in recumbency, the researchers observed a decrease in pressure of arterial oxygen (PaO), followed by an increase prior to disconnecting the circuit.
  • Correspondingly, the PO widened, indicating decreased oxygen exchange efficiency, but improved before the disconnection of the anesthetic circuit.
  • The last point of the study saw lower body temperature, reduced ionized-Ca, and blood glucose levels, while an increase in Na was observed.

Conclusions

  • Overall, the results suggest that turning anesthetized horses can decrease the pressure of arterial oxygen and widen the alveolar-arterial oxygen tension gradient, indicating potential issues in oxygen transport from the lungs to the blood. This finding highlights the need for a cautious approach when working with animals that already suffer from low oxygen levels in the blood (hypoxemia).

Cite This Article

APA
Niyom S, Mama KR, King M, Contino E, Ferris D, Valdes-Martinez A, Frisbie DD, McIlwraith W, Zumbrunnen J. (2018). 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, 80(10), 1584-1589. https://doi.org/10.1292/jvms.18-0032

Publication

ISSN: 1347-7439
NlmUniqueID: 9105360
Country: Japan
Language: English
Volume: 80
Issue: 10
Pages: 1584-1589

Researcher Affiliations

Niyom, Sirirat
  • Department of Companion Animal Clinical Sciences, Faculty of Veterinary Medicine, Kasetsart University, Bangkok 10900, Thailand.
Mama, Khursheed R
  • Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO 80523, U.S.A.
King, Melissa
  • Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO 80523, U.S.A.
Contino, Erin
  • Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO 80523, U.S.A.
Ferris, Dora
  • Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO 80523, U.S.A.
Valdes-Martinez, Alex
  • Department of Environmental & Radiological Health Sciences, Colorado State University, Fort Collins, CO 80523, U.S.A.
Frisbie, David D
  • Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO 80523, U.S.A.
McIlwraith, Wayne
  • Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO 80523, U.S.A.
Zumbrunnen, James
  • Department of Statistics, Colorado State University, Fort Collins, CO 80523, U.S.A.

MeSH Terms

  • Anesthesia / veterinary
  • Anesthetics, Inhalation
  • Animals
  • Blood Gas Analysis / veterinary
  • Female
  • Horses
  • Isoflurane
  • Male
  • Oxygen / blood
  • Posture
  • Pulmonary Alveoli / metabolism
  • Respiration, Artificial / methods
  • Respiration, Artificial / veterinary

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