Haemoglobin concentration measurement agreement obtained from three different devices in anaesthetised horses.
Authors: Santos Luiz Cesar Pereira, Werfel Kate, Ferlini-Agne Gustavo
Journal: Veterinary journal (London, England : 1997)
Summary
# Editorial Summary Maintaining accurate haemoglobin measurements during equine anaesthesia is essential for assessing oxygen delivery and managing intraoperative complications, yet the reliability of non-invasive point-of-care devices in horses remains poorly characterised. This prospective trial evaluated agreement between three methods—the SpHb pulse co-oximeter, an Epoc® blood gas analyser, and haemoglobin estimation from packed cell volume (PCV) via microhaematocrit—across 34 horses undergoing elective surgery, using PCV-derived values as the reference standard and accepting a maximum 7% variance as clinically acceptable. Both devices substantially underestimated haemoglobin: SpHb readings were 4.96 g/dL lower and Epoc® readings 3.6 g/dL lower than PCV-estimated values (mean reference 14.6 g/dL), with weak concordance correlations of 0.08 and 0.14 respectively, and bias exceeding acceptable thresholds on Bland-Altman analysis. These findings suggest that neither the SpHb Radical-7® nor the Epoc® should currently be relied upon as substitutes for laboratory-based haemoglobin assessment in anaesthetised horses, and practitioners requiring accurate haemoglobin data during surgery should continue using traditional microhaematocrit or venous blood gas analysis rather than non-invasive alternatives. The authors appropriately highlight that species-specific device calibration and larger validation studies are necessary before clinical adoption can be recommended for equine anaesthetic monitoring.
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Practical Takeaways
- •SpHb pulse co-oximetry and Epoc® blood gas analysis cannot be reliably used as substitutes for traditional haemoglobin measurement methods in anaesthetised horses; neither device provides clinically acceptable accuracy for monitoring oxygen-carrying capacity during surgery
- •If using these devices intraoperatively, be aware they will significantly underestimate actual haemoglobin levels—do not rely on their readings for transfusion decisions without corroborating laboratory confirmation
- •Stick with PCV-based haemoglobin estimation or direct laboratory analysis via traditional microhaematocrit methods until device calibration improves for equine patients
Key Findings
- •SpHb pulse co-oximeter underestimated haemoglobin by an average of 4.96 g/dL compared to PCV-derived values, with weak concordance (CCC 0.08)
- •Epoc® blood gas analyser underestimated haemoglobin by 3.6 g/dL with weak concordance (CCC 0.14)
- •Both devices demonstrated significant biases exceeding the acceptable 7% threshold with wide limits of agreement in Bland-Altman analysis
- •Mean haemoglobin concentrations differed substantially: [Hb]PCV_est 14.6±1.8 g/dL, Epoc® 11.0±1.8 g/dL, SpHb® 9.6±1.5 g/dL