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Home / Equine Research Bank / Animals (Basel) / Effect of 15° Reverse Trendelenburg Position on Arteria...
Animals : an open access journal from MDPI2022; 12(3); 353; doi: 10.3390/ani12030353

Effect of 15° Reverse Trendelenburg Position on Arterial Oxygen Tension during Isoflurane Anesthesia in Horses.

Abstract: Lower than expected arterial oxygen tension (PaO) continues to be an unresolved problem in equine anesthesia. The aim of this randomized, crossover, and prospective study using six adult horses is to determine if a 15° reverse Trendelenburg position (RTP) increases PaO during inhalation anesthesia. Under constant-dose isoflurane anesthesia, dorsally recumbent horses were positioned either horizontally (HP) or in a 15° RTP for 2 h. Lungs were mechanically ventilated (15 mL/kg, 6 breaths/min). Arterial carbon dioxide tension (PaCO), PaO, inspired oxygen fraction (FiO), and end-tidal carbon dioxide tension (EtCO) were determined every 30 min during anesthesia. Indices of dead-space ventilation (Vd/Vt), oxygenation (P-F ratio), and perfusion (F-shunt) were calculated. Dobutamine and phenylephrine were used to support mean arterial pressure (MAP). Data are presented as median and range. In one horse, which was deemed an outlier due to its thoracic dimensions and body conformation, indices of oxygenation worsened in RTP compared to HP (median PaO 438 vs. 568 mmHg; P-F ratio 454 vs. 586 mmHg, and F-shunt 13.0 vs. 5.7 mmHg). This horse was excluded from calculations. In the remaining five horses they were significantly better with RTP compared to HP. Results in remaining five horses showed that PaO (502, 467-575 vs. 437, 395-445 mmHg), P-F ratio (518, 484-598 vs. 455, 407-458 mmHg), and F-shunt (10.1, 4.2-11.7 vs. 14.2, 13.8-16.0 mmHg) were significantly different between RTP and HP ( = 0.03). Other variables were not significantly different. In conclusion, the 15° RTP resulted in better oxygenation than HP in dorsally recumbent, isoflurane-anesthetized horses, although worsening of oxygenation may occur in individual horses. A study detailing the cardiovascular consequences of RTP is necessary before it can be recommended for clinical practice.
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Publication Date: 2022-02-01 PubMed ID: 35158676PubMed Central: PMC8833611DOI: 10.3390/ani12030353Google 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 study investigates whether positioning horses in a 15° reverse Trendelenburg position (RTP) during inhalation anesthesia improves arterial oxygen tension (PaO) compared to a horizontal position (HP). The research shows that oxygenation was generally better in RTP than HP for anesthetized horses, but potential negative effects on individual horses suggest that further study is needed before RTP can be clinically recommended.

Overall study design and method

  • This research is a randomized, crossover, and prospective study involving six adult horses.
  • The impact of horse positioning on arterial oxygen tension during inhalation anesthesia was assessed.
  • Horses under constant-dose isoflurane anesthesia were positioned either horizontally (HP) or in a 15° reverse Trendelenburg position (RTP) for two hours.
  • Horses’ lungs were mechanically ventilated at a rate of 15 mL/kg for six breaths per minute.

Data collection and variables

  • Arterial carbon dioxide tension (PaCO), arterial oxygen tension (PaO), inspired oxygen fraction (FiO), and end-tidal carbon dioxide tension (EtCO) were measured every 30 minutes during anesthesia.
  • Indices of dead-space ventilation (Vd/Vt), oxygenation (P-F ratio) and perfusion (F-shunt) were calculated.
  • Dobutamine and phenylephrine were applied to support mean arterial pressure (MAP).

Results and findings

  • In one horse, considered an outlier due to its thoracic dimensions and body conformation, oxygenation was worse in RTP compared to HP. This horse was excluded from the final calculation.
  • In the remaining five horses, oxygenation was significantly better in RTP than HP.
  • Specifically, PaO, P-F ratio and F-shunt were significantly better in RTP, indicating improved oxygenation. Other variables showed no significant difference between RTP and HP.

Conclusion and future work

  • The 15° RTP resulted in overall better oxygenation than HP in dorsally recumbent, isoflurane-anesthetized horses.
  • However, worsening of oxygenation may occur in individual horses, implying a need for additional studies to clarify the effect on other physiological characteristics.
  • Before RTP can be recommended for clinical practice, a more thorough examination of its cardiovascular effects is needed.

Cite This Article

APA
Tucker L, Almeida D, Wendt-Hornickle E, Baldo CF, Allweiler S, Guedes AGP. (2022). Effect of 15° Reverse Trendelenburg Position on Arterial Oxygen Tension during Isoflurane Anesthesia in Horses. Animals (Basel), 12(3), 353. https://doi.org/10.3390/ani12030353

Publication

Animals : an open access journal from MDPI
ISSN: 2076-2615
NlmUniqueID: 101635614
Country: Switzerland
Language: English
Volume: 12
Issue: 3
PII: 353

Researcher Affiliations

Tucker, Laura
  • Veterinary Clinical Sciences Department, College of Veterinary Medicine, University of Minnesota, St. Paul, MN 55108, USA.
  • Department of Clinical Studies, Ontario Veterinary College, University of Guelph, Guelph, ON N1G 2W1, Canada.
Almeida, Daniel
  • Veterinary Clinical Sciences Department, College of Veterinary Medicine, University of Minnesota, St. Paul, MN 55108, USA.
Wendt-Hornickle, Erin
  • Veterinary Clinical Sciences Department, College of Veterinary Medicine, University of Minnesota, St. Paul, MN 55108, USA.
Baldo, Caroline F
  • Veterinary Clinical Sciences Department, College of Veterinary Medicine, University of Minnesota, St. Paul, MN 55108, USA.
  • Boston Scientific, Research and Technology Center, Arden Hills, MN 55112, USA.
Allweiler, Sandra
  • Veterinary Clinical Sciences Department, College of Veterinary Medicine, University of Minnesota, St. Paul, MN 55108, USA.
Guedes, Alonso G P
  • Veterinary Clinical Sciences Department, College of Veterinary Medicine, University of Minnesota, St. Paul, MN 55108, USA.

Conflict of Interest Statement

The authors declare no conflict of interest.

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