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BMC veterinary research2017; 13(1); 361; doi: 10.1186/s12917-017-1265-3

Effects of controlled hypoxemia or hypovolemia on global and intestinal oxygenation and perfusion in isoflurane anesthetized horses receiving an alpha-2-agonist infusion.

Abstract: Aim of this prospective experimental study was to assess effects of systemic hypoxemia and hypovolemia on global and gastrointestinal oxygenation and perfusion in anesthetized horses. Therefore, we anesthetized twelve systemically healthy warmblood horses using either xylazine or dexmedetomidine for premedication and midazolam and ketamine for induction. Anesthesia was maintained using isoflurane in oxygen with either xylazine or dexmedetomidine and horses were ventilated to normocapnia. During part A arterial oxygen saturation (SaO) was reduced by reducing inspiratory oxygen fraction in steps of 5%. In part B hypovolemia was induced by controlled arterial exsanguination via roller pump (rate: 38 ml/kg/h). Mean arterial blood pressure (MAP), heart rate, pulmonary artery pressure, arterial and central venous blood gases and cardiac output were measured, cardiac index (CI) was calculated. Intestinal microperfusion and oxygenation were measured using laser Doppler flowmetry and white-light spectrophotometry. Surface probes were placed via median laparotomy on the stomach, jejunum and colon. Results: Part A: Reduction in arterial oxygenation resulted in a sigmoid decrease in central venous oxygen partial pressure. At SaO < 80% no further decrease in central venous oxygen partial pressure occurred. Intestinal oxygenation remained unchanged until SaO of 80% and then decreased. Heart rate and pulmonary artery pressure increased significantly during hypoxemia. Part B: Progressive reduction in circulating blood volume resulted in a linear decrease in MAP and CI. Intestinal perfusion was preserved until blood loss resulted in MAP and CI lower 51 ± 5 mmHg and 40 ± 3 mL/kg/min, respectively, and then decreased rapidly. Conclusions: Under isoflurane, intestinal tissue oxygenation remained at baseline when arterial oxygenation exceeded 80% and intestinal perfusion remained at baseline when MAP exceeded 51 mmHg and CI exceeded 40 mL/kg/min in this group of horses. Unassigned: 33.14-42,502-04-14/1547.
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Publication Date: 2017-11-28 PubMed ID: 29183321PubMed Central: PMC5706348DOI: 10.1186/s12917-017-1265-3Google Scholar: Lookup
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Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

The research article discusses an investigation into the effects of systemic hypoxemia (low oxygen in the blood) and hypovolemia (decreased blood volume) on the overall and gastrointestinal oxygenation and blood flow in anesthetized horses. Twelve healthy warmblood horses were used for the study, which revealed that intestinal tissue oxygenation remained normal when arterial oxygenation was above 80%, and intestinal blood flow was normal when Mean Arterial Pressure was above 51 mmHg.

Research Methodology

  • The researchers carried out a prospective experimental study using 12 healthy warmblood horses.
  • These horses were anesthetized with xylazine or dexmedetomidine for premedication and midazolam and ketamine for induction.
  • Anesthesia was maintained using isoflurane in oxygen with xylazine or dexmedetomidine. The horses were ventilated to maintain normocapnia (normal carbon dioxide level in the bloodstream).
  • During the first part of the procedure, the team reduced arterial oxygen saturation (SaO) by reducing the fraction of inspired oxygen in 5% increments. In the second part, they induced hypovolemia via controlled arterial exsanguination using a roller pump at a rate of 38 ml/kg/h.

Measurements and Observations

  • The team monitored several variables including Mean Arterial Pressure (MAP), heart rate, pulmonary artery pressure, arterial and central venous blood gases, and cardiac output. The cardiac index was also calculated.
  • Intestinal microperfusion and oxygenation were determined using advanced techniques like laser Doppler flowmetry and white-light spectrophotometry. Surface probes were used for this measurement which were placed on the stomach, jejunum, and colon of the horses through a median laparotomy.

Results

  • In Part A of the experiment, reduction in arterial oxygenation resulted in a sigmoid decrease in central venous oxygen partial pressure. When arterial oxygen saturation fell below 80%, there was no further decrease observed in central venous oxygen partial pressure. Until the arterial blood oxygen saturation was 80%, the blood oxygen in the intestine didn’t decrease. Heart rate and pulmonary artery pressure increased significantly during periods of low arterial oxygen.
  • In Part B, a reduction in blood volume caused a linear decrease in Mean Arterial Pressure and Cardiac Index. Intestinal blood flow was preserved until blood loss led to a decrease in Mean Arterial Pressure and Cardiac Index below certain levels, following which it decreased rapidly.

Conclusions

  • The research concluded that when horses are under isoflurane anesthesia, their intestinal tissue oxygen stays normal if arterial oxygen is above 80%. Similarly, intestinal blood flow remains normal if Mean Arterial Pressure is over 51 mmHg and Cardiac Index is over 40 mL/kg/min.

Cite This Article

APA
Hopster K, Wittenberg-Voges L, Geburek F, Hopster-Iversen C, Kästner SBR. (2017). Effects of controlled hypoxemia or hypovolemia on global and intestinal oxygenation and perfusion in isoflurane anesthetized horses receiving an alpha-2-agonist infusion. BMC Vet Res, 13(1), 361. https://doi.org/10.1186/s12917-017-1265-3

Publication

BMC veterinary research
ISSN: 1746-6148
NlmUniqueID: 101249759
Country: England
Language: English
Volume: 13
Issue: 1
Pages: 361
PII: 361

Researcher Affiliations

Hopster, Klaus
  • Equine Clinic, University of Veterinary Medicine Hanover, Foundation, Bünteweg 9, D-30559, Hanover, Germany. Klaus.hopster@gmx.de.
  • Department of Clinical Studies-NBC, School of Veterinary Medicine, University of Pennsylvania, 382 West Street Road, Kennett Square, PA, 19348, USA. Klaus.hopster@gmx.de.
Wittenberg-Voges, Liza
  • Equine Clinic, University of Veterinary Medicine Hanover, Foundation, Bünteweg 9, D-30559, Hanover, Germany.
Geburek, Florian
  • Equine Clinic, University of Veterinary Medicine Hanover, Foundation, Bünteweg 9, D-30559, Hanover, Germany.
Hopster-Iversen, Charlotte
  • Equine Clinic, University of Veterinary Medicine Hanover, Foundation, Bünteweg 9, D-30559, Hanover, Germany.
Kästner, Sabine B R
  • Equine Clinic, University of Veterinary Medicine Hanover, Foundation, Bünteweg 9, D-30559, Hanover, Germany.

MeSH Terms

  • Anesthesia, Inhalation / veterinary
  • Anesthetics, Inhalation / administration & dosage
  • Anesthetics, Inhalation / pharmacology
  • Animals
  • Dexmedetomidine / administration & dosage
  • Dexmedetomidine / pharmacology
  • Female
  • Heart Rate
  • Horses
  • Hypovolemia / veterinary
  • Hypoxia / veterinary
  • Intestinal Mucosa / metabolism
  • Intestines / drug effects
  • Isoflurane / administration & dosage
  • Isoflurane / pharmacology
  • Laser-Doppler Flowmetry
  • Male
  • Oxygen / metabolism
  • Prospective Studies
  • Spectrophotometry
  • Xylazine / administration & dosage
  • Xylazine / pharmacology

Conflict of Interest Statement

ETHICS APPROVAL: The study was approved by the Ethics Committee for Animal Experiments of Lower Saxony, Germany, number 33.14-42502-04- 14/1547. CONSENT FOR PUBLICATION: Not applicable as the manuscript does not contain data from any individual person. COMPETING INTERESTS: The authors declare that they have no competing interests. PUBLISHER’S NOTE: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

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Citations

This article has been cited 3 times.
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  2. Song HL, Wang R, Shi TY, Wang AM, Xia Q. Machine learning-based mortality risk prediction model for elderly diabetic patients with non-ST-segment elevation myocardial infarction using MIMIC-IV database. Sci Rep 2025 Dec 15;15(1):43796.
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