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Agreement between invasive and oscillometric blood pressure measurements during controlled haemorrhage in
Colleen Hickey1, Alonso Guedes1, Jessica Byrne1
1Department of Veterinary Clinical Sciences, College of Veterinary Medicine, University of Minnesota, St. Paul, Minnesota, USA.
Background:
Defining the reliability of oscillometry (NIBP) for measuring mean arterial pressure (MAP) during normotension and hypovolaemic hypotension could help with cardiovascular monitoring and management in horses anaesthetised in dorsal recumbency.
Objectives:
To assess agreement between NIBP and invasive MAP during normotension and hypovolaemic hypotension in dorsally-recumbent, anaesthetised horses.
Study Design:
Prospective experimental study using 11 horses.
Methods:
Under isoflurane anaesthesia, blood was removed at 5 mL/kg bwt increments up to 25 mL/kg bwt and returned in a similar fashion. Paired NIBP (from the tail base with a cuff width-to-tail circumference ratio of 0.25) and invasive MAP measurements (metatarsal, facial, and transverse facial arteries; MT, FA, TFA) were obtained before and during blood removal/return and analysed using a Bland-Altman analysis for repeated measurements. Sensitivity and specificity of NIBP to detect hypotension (MAP <70 mmHg) were calculated, and an optimum NIBP MAP cut-off for hypotension was estimated.
Results:
A total of 280 paired NIBP and invasive MAP were compared. The ACVIM validation criteria were met for bias, precision, and limits of agreement (LoA) for all peripheral arterial locations. Correlations between paired measurements, which just fell short of the 0.9 required, were 0.888, 0.887, and 0.856 for the MT, FA, and TFA, respectively. Oscillometric technique underestimated invasive mean arterial pressure by an average of -2.5 mmHg (LoA -23 to 19), -1.3 mmHg (LoA -22 to 19), and -4.7 mmHg (LoA -27 to 18) when compared to the MT, FA, and TFA, respectively.
Main Limitations:
Only adult horses in dorsal recumbency were studied.
Conclusions:
NIBP, as studied here, was deemed acceptable compared to invasive MAP in the MT, FA, and TFA under normotension and hypovolaemic hypotension but not a replacement for invasive blood pressure monitoring in horses.
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