Retrospective comparison of equine hemoglobin oxygen saturation measured by a human-specific co-oximeter, or derived from an algorithm using temperature-corrected and -uncorrected oxygen tension.
Abstract: Hemoglobin oxygen saturation (SO) is measured by co-oximetry (SO) or calculated from partial pressure of oxygen (PO) using algorithms (SO). To compare venous and systemic arterial blood sample data retrospectively and to examine whether temperature correction of PO is important. Methods: Retrospective study. Methods: A group of 21 healthy, adult, sedated or anesthetized horses. Methods: Mixed-venous and systemic arterial blood samples (1 mL) were anaerobically collected using commercial preheparinized syringes from the right ventricle and facial artery, respectively. Blood was analyzed using a commercial gas analyzer and human-specific co-oximeter within 10 minutes of collection or stored on ice and analyzed within 30 minutes. PO was measured at 37 °C and corrected using body temperature (T) from a pulmonary artery catheter thermistor. SO and hemoglobin subtypes were measured by co-oximetry (37 °C). An algorithm developed for Thoroughbred horse blood was used to calculate SO using PO at 37 °C and SO with PO corrected to T. SO and SO were each paired with SO using Bland-Altman (repeated measures) ratio of SO/SO (204 samples). Results: SO overestimated SO when PO was <80 mmHg (10.7 kPa); ratio and limits of agreement: 1.2 (0.9-1.6) but became accurate when PO was ≥80 mmHg: 1.0 (1.0-1.0). With all data, SO did not differ from SO:1.1 (0.8-1.4). Methemoglobin (FMetHb) and carboxyhemoglobin (FCOHb) were significantly higher in venous [FMetHb: median (range): 1.8 (0-2.9)%; FCOHb: 0.1 (0-2)%] than in arterial blood [FMetHb: 0.5 (0-2.2)%; FCOHb: 0 (0-0.3)%]. Conclusions: The algorithm appeared robust when PO was ≥80 mmHg (10.7 kPa) but overestimated when PO was lower. Temperature correction was not important within 34.9-37.3 °C. Conclusions: SO overestimation in venous blood can result in calculation of higher intrapulmonary shunt fraction than SO values.
Copyright © 2019 Association of Veterinary Anaesthetists and American College of Veterinary Anesthesia and Analgesia. Published by Elsevier Ltd. All rights reserved.
Publication Date: 2019-06-12 PubMed ID: 31377121DOI: 10.1016/j.vaa.2019.05.011Google Scholar: Lookup
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- Comparative Study
- Journal Article
Summary
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The study compares two methods for measuring hemoglobin oxygen saturation (SO) in horses, using a human-specific co-oximeter and an algorithmic calculation, to understand the importance of temperature correction. The comparison was made using blood samples from healthy adult horses. Findings suggest the algorithmic approach is accurate when oxygen pressure (PO) is at or above 80 mmHg, but overestimates when it’s lower. Temperature correction did not appear to be crucial within the range of 34.9-37.3 degrees Celsius.
Experiment Overview
- The research was a retrospective study conducted with 21 healthy, adult, sedated or anesthetized horses.
- Blood samples were taken from two types of locations: the right ventricle (mixed-venous) and the facial artery (systemic arterial).
- Blood was collected using preheparinized syringes and was analyzed within 10-30 minutes of collection using a gas analyzer and a human-specific co-oximeter.
- Oxygen pressure was measured at a constant temperature (37°C) and also adjusted according to the horse’s body temperature.
- An algorithm created for thoroughbred horse blood was used to calculate oxygen saturation using temperature-corrected and -uncorrected oxygen tension.
Results and Observations
- Findings showed that the algorithm overestimated oxygen saturation when the oxygen pressure was less than 80 mmHg, but was accurate when the pressure was 80 mmHg or more.
- There were no noticeable differences between temperature-corrected and -uncorrected calculations.
- Higher levels of methemoglobin and carboxyhemoglobin were found in venous blood sampling than in arterial blood sampling.
- Data was evaluated using the Bland-Altman method, a statistical process used to compare two different ways of measuring something.
Conclusions and Implications
- The algorithm was most reliable when calculating oxygen saturation at higher oxygen pressures. At lower pressure levels, the method overestimated oxygen saturation.
- Temperature correction between the range of 34.9-37.3 degrees Celsius didn’t significantly impact the results.
- The research concludes that overestimation of oxygen saturation in venous blood can lead to miscalculations of the intrapulmonary shunt fraction.
Cite This Article
APA
Duke-Novakovski T.
(2019).
Retrospective comparison of equine hemoglobin oxygen saturation measured by a human-specific co-oximeter, or derived from an algorithm using temperature-corrected and -uncorrected oxygen tension.
Vet Anaesth Analg, 46(5), 636-642.
https://doi.org/10.1016/j.vaa.2019.05.011 Publication
Researcher Affiliations
- Department of Small Animal Clinical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, SK, Canada.
MeSH Terms
- Algorithms
- Animals
- Hemoglobins / metabolism
- Horses / blood
- Humans
- Oximetry / instrumentation
- Oximetry / veterinary
- Oxygen / blood
- Predictive Value of Tests
- Pulmonary Gas Exchange
- Respiratory Physiological Phenomena
- Retrospective Studies
- Temperature
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