Agreement of a veterinary-specific oscillometric noninvasive arterial blood pressure monitor (SunTech Vet30) with invasive arterial blood pressure in anaesthetised horses.

Objective Overview

• This study assessed how well a veterinary-specific oscillometric blood pressure monitor (SunTech Vet30) agrees with the gold standard invasive arterial blood pressure (IBP) method in anesthetized horses.

Introduction and Purpose

• Monitoring arterial blood pressure (ABP) during anesthesia in horses is critical for detecting hypotension and maintaining adequate organ perfusion.
• Invasive arterial blood pressure (IBP) measurement via arterial catheter is the gold standard but can be technically challenging or not always feasible in clinical settings.
• Oscillometric noninvasive blood pressure monitors offer an easier alternative but their accuracy and agreement with IBP in horses, especially under anesthesia, needed evaluation.
• This study aimed to compare readings from the SunTech Vet30 oscillometric monitor, designed for veterinary use, against invasive measurements in anesthetized horses to determine their agreement and reliability.

Methodology

• A prospective clinical method-comparison study was conducted involving 46 horses undergoing general anesthesia in dorsal recumbency.
• Paired invasive and oscillometric blood pressure measurements were recorded every 15 minutes throughout anesthesia.
• Invasive arterial pressure (systolic – SAP, diastolic – DAP, mean – MAP) was measured via a catheter placed in the facial artery, considered a reliable site for IBP in horses.
• The oscillometric blood pressure was obtained with the SunTech Vet30 monitor using cuffs positioned either at the tail base or on the distal thoracic limb, depending on clinical access.
• All oscillometric measurements were hydrostatically corrected relative to the level of the IBP transducer to reduce positional bias.
• Agreement between methods was statistically analyzed using Bland-Altman plots for repeated measures, with differences modeled as oscillometric values minus invasive values, accounting for individual horse variability.

Results

• A total of 311 paired blood pressure measurements were analyzed.
• Bias (mean difference) between oscillometric and invasive methods was found to be:
  • SAP: +3.1 mmHg (oscillometric values slightly higher)
  • DAP: -0.4 mmHg (very close)
  • MAP: -4.5 mmHg (oscillometric values slightly lower)
• The limits of agreement, which describe the range within which 95% of differences fall, were wide:
  • SAP: -24.6 to +30.8 mmHg
  • DAP: -24.5 to +23.7 mmHg
  • MAP: -30.9 to +21.9 mmHg
• There was proportional bias observed for DAP and MAP, meaning that the differences between the two measurement methods depended on the actual blood pressure level.
• For clinical detection of hypotension (defined as IBP MAP < 70 mmHg), an oscillometric MAP cutoff of < 70 mmHg produced:
  • Sensitivity: 77.4% (ability to correctly identify hypotensive cases)
  • Specificity: 63.4% (ability to correctly identify non-hypotensive cases)
  • The area under the curve (AUC) for this test was 0.753, indicating moderate overall accuracy.

Conclusions and Clinical Implications

• The SunTech Vet30 oscillometric monitor showed a substantial amount of variability compared to invasive measurements, with wide limits of agreement.
• This indicates it should not be used as a direct substitute for invasive blood pressure measurement in anesthetized horses.
• Although oscillometric measurements can provide helpful supplementary physiological information when IBP monitoring isn’t feasible, they must be interpreted with caution.
• Care should be taken when using oscillometric blood pressure readings for critical clinical decisions, such as identifying hypotension or adjusting therapy during anesthesia, due to variable accuracy.
• Overall, invasive blood pressure monitoring remains the preferred method for precise and reliable blood pressure assessment in anesthetized horses whenever possible.