Equine veterinary journal2026; doi: 10.1002/evj.70324

Agreement between invasive and oscillometric blood pressure measurements during controlled haemorrhage in anaesthetised horses.

Hickey, C
·
Guedes, A
·
Byrne, J
·
Hatschbach, E
·
Walters, B
·
Rendahl, A
·
Tearney, C

Abstract: 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. Objective: To assess agreement between NIBP and invasive MAP during normotension and hypovolaemic hypotension in dorsally-recumbent, anaesthetised horses. Methods: 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. Conclusions: 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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Publication Date: 2026-08-31 PubMed ID: 42670298DOI: 10.1002/evj.70324Google Scholar: Lookup

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Overview

This study evaluated how well non-invasive oscillometric blood pressure measurements (NIBP) agree with invasive mean arterial pressure (MAP) measurements in anesthetised horses, especially during normal blood pressure and controlled blood loss conditions.
The goal was to determine if oscillometric methods can reliably monitor cardiovascular status during anesthesia when horses are in dorsal recumbency (lying on their back).

Background and Purpose

Monitoring blood pressure accurately in anesthetised horses is crucial for managing their cardiovascular health and ensuring safety during procedures.
Invasive blood pressure measurement, involving arterial catheterization, is the gold standard but can be technically difficult and carries risks.
Oscillometric devices offer a non-invasive alternative by measuring blood pressure at a peripheral site using a cuff, but their accuracy during low blood volume (hypovolaemic hypotension) states in horses is unclear.
The study aimed to compare oscillometric (non-invasive) mean arterial pressure (MAP) readings with invasive MAP readings from different arteries to assess agreement under both normal and blood loss conditions in anesthetised horses positioned on their backs.

Study Design and Methods

Eleven adult horses anesthetised with isoflurane gas and positioned in dorsal recumbency were used.
Controlled hemorrhage was induced by removing blood incrementally in steps of 5 mL per kg body weight up to a total of 25 mL/kg to create hypovolaemic hypotension.
Blood was then returned to reverse the hypovolemia in similar increments.
Paired blood pressure measurements were taken before, during, and after blood removal/return:

Non-invasive oscillometric blood pressure (NIBP) measured using a cuff placed at the tail base with a cuff width-to-tail circumference ratio of 0.25.
Invasive MAP measured directly in three arterial sites: metatarsal artery (MT), facial artery (FA), and transverse facial artery (TFA).

Data analysis included Bland-Altman methods for agreement to compare paired measurements and evaluation against ACVIM (American College of Veterinary Internal Medicine) validation criteria.
Sensitivity and specificity of NIBP to detect hypotension (MAP < 70 mmHg) were also calculated, along with an optimum cutoff for NIBP MAP to identify hypotension.

Key Results

A total of 280 paired invasive and non-invasive MAP measurements were compared.
Oscillometric measurements met ACVIM criteria regarding bias (average difference), precision (standard deviation of differences), and limits of agreement (LoA) for all arterial sites.
Correlation coefficients between paired invasive and oscillometric measurements were high but slightly below the ideal threshold of 0.9:

Metatarsal artery (MT): 0.888
Facial artery (FA): 0.887
Transverse facial artery (TFA): 0.856

Oscillometric readings tended to underestimate invasive MAP values by a small amount:

MT: -2.5 mmHg average difference (with limits of agreement from -23 to +19 mmHg)
FA: -1.3 mmHg average difference (LoA -22 to +19 mmHg)
TFA: -4.7 mmHg average difference (LoA -27 to +18 mmHg)

The non-invasive method showed acceptable accuracy under both normal blood pressure and controlled blood loss conditions but with some variability.

Conclusions and Implications

The oscillometric NIBP technique is an acceptable method to estimate MAP in adult horses under anesthesia in dorsal recumbency.
Although not a perfect substitute for invasive arterial blood pressure monitoring, NIBP is a useful non-invasive alternative that can help in cardiovascular monitoring during both normal and hypovolaemic hypotensive states.
Clinicians should be aware that oscillometric readings may slightly underestimate true MAP and variability is notable, so invasive monitoring remains preferable when precise blood pressure measurement is critical.
This study only tested adult horses positioned dorsally and under general anesthesia with isoflurane; results may differ with other positions, horse populations, or anesthetics.
Further research could evaluate other patient positions, longer anesthesia durations, and different clinical scenarios to generalize findings.

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APA

Hickey C, Guedes A, Byrne J, Hatschbach E, Walters B, Rendahl A, Tearney C. (2026). Agreement between invasive and oscillometric blood pressure measurements during controlled haemorrhage in anaesthetised horses. Equine Vet J. https://doi.org/10.1002/evj.70324

Publication

Equine veterinary journal

ISSN: 2042-3306

NlmUniqueID: 0173320

Country: United States

Language: English

Researcher Affiliations

Hickey, Colleen

Department of Veterinary Clinical Sciences, College of Veterinary Medicine, University of Minnesota, St. Paul, Minnesota, USA.

Guedes, Alonso

Department of Veterinary Clinical Sciences, College of Veterinary Medicine, University of Minnesota, St. Paul, Minnesota, USA.

Byrne, Jessica

Department of Veterinary Clinical Sciences, College of Veterinary Medicine, University of Minnesota, St. Paul, Minnesota, USA.

Hatschbach, Eduardo

Department of Veterinary Clinical Sciences, College of Veterinary Medicine, University of Minnesota, St. Paul, Minnesota, USA.

Walters, Brian

Department of Veterinary Clinical Sciences, College of Veterinary Medicine, University of Minnesota, St. Paul, Minnesota, USA.

Rendahl, Aaron

Department of Veterinary and Biomedical Sciences, College of Veterinary Medicine, University of Minnesota, St. Paul, Minnesota, USA.

Tearney, Caitlin

Department of Veterinary Clinical Sciences, College of Veterinary Medicine, University of Minnesota, St. Paul, Minnesota, USA.

Grant Funding

MINV-67-004 / U.S. Department of Agriculture

References

This article includes 30 references

Gozalo‐Marcilla M, Redondo JI, Bettschart‐Wolfensberger R, Domenech L, Domenech J, Johnston GM. The confidential enquiry into perioperative equine fatalities: phase 4 (CEPEF4) ‐ a worldwide observational, prospective, multicentre cohort study in 2025. Vet Anaesth Analg 2025;52(5):525–538.
Young SS, Taylor PM. Factors influencing the outcome of equine anaesthesia: a review of 1,314 cases. Equine Vet J 1993;25(2):147–151.
Voulgaris DA, Hofmeister EH. Multivariate analysis of factors associated with post‐anesthetic times to standing in isoflurane‐anesthetized horses: 381 cases. Vet Anaesth Analg 2009;36(5):414–420.
Meidert AS, Dolch ME, Mühlbauer K, Zwissler B, Klein M, Briegle J. Oscillometric versus invasive blood pressure measurement in patients with shock: a prospective observational study in the emergency department. J Clin Monit Comput 2021;35(2):387–393.
Beringer R, Keith A, Jones E, Murphy T, White P. A prospective comparison of invasive and non‐invasive blood pressure in children undergoing cardiac catheterization. Paediatr Anaesth 2023;33(10):816–822.
Kouz K, Wegge M, Flick M, Bergholz A, Moll‐Khosrawi P, Nitzschke R. Continuous intra‐arterial versus intermittent oscillometric arterial pressure monitoring and hypotension during induction of anaesthesia: the AWAKE randomised trial. Br J Anaesth 2022;129(4):478–486.
Radhakrishnan S, Lorenzutti AM, Araos JD, Martin‐Flores M. Evaluation of noninvasive blood pressure in anesthetized horses: bias, limits of agreement, and comparative detection of a predetermined mean blood pressure warranting treatment. Can Vet J 2021;62(9):994–998.
Twele L, Neudeck S, Delarocque J, Verhaar N, Reiners J, Noll M. Agreement of high‐definition oscillometry (HDO) and invasive blood pressure measurements at a metatarsal artery in isoflurane‐anaesthetised horses. Animals (Basel) 2022;12(3):363.
Pratt S, Barnes TS, Cowling N, de Klerk K, Rainger J, Sole‐Guitart A. Bias associated with peripheral non‐invasive compared to invasive arterial blood pressure monitoring in healthy anaesthetised and standing horses using the Bionet BM7Vet. Vet Sci 2022;9(2):52.
Heliczer N, Lorello O, Casoni D, Navas de Solis C. Accuracy and precision of noninvasive blood pressure in normo‐, hyper‐, and hypotensive standing and anesthetized adult horses. J Vet Intern Med 2016;30(3):866–872.
Midon M, Yamada DI, Zangirolami FD, Simionato GC, Feringer Junior WH, Conde G. Comparison of four arteries for invasive blood pressure measurements and Dixtal 2010 oscillometric values in horses anesthetized with isoflurane: does the artery matter?. J Equine Vet Sci 2023;121:104219.
Tünsmeyer J, Hopster K, Feige K, Kästner SBR. Agreement of high definition oscillometry with direct arterial blood pressure measurement at different blood pressure ranges in horses under general anaesthesia. Vet Anaesth Analg 2015;42(3):286–291.
Olsen E, Skovgaard Pedersen TL, Robinson R, Haubro Andersen P. Accuracy and precision of oscillometric blood pressure in standing conscious horses. J Vet Emerg Crit Care (San Antonio) 2016;26(1):85–92.
Tearney CC, Guedes AGP, Brosnan RJ. Equivalence between invasive and oscillometric blood pressures at different anatomic locations in healthy normotensive anesthetized horses. Equine Vet J 2016;48(3):357–361.
Geddes LA, Chaffee V, Whistler SJ, Bourland JD, Tacker WA. Indirect mean blood pressure in the anesthetized pony. Am J Vet Res 1977;38(12):2055–2057.
Latshaw H, Fessler JF, Whistler SJ, Geddes LA. Indirect measurement of mean blood pressure in the normotensive and hypotensive horse.. Equine Vet J 1979;11(3):191–194.
Acierno MJ, Brown S, Coleman AE, Jepson RE, Papich M, Stepien RL. ACVIM consensus statement: guidelines for the identification, evaluation, and management of systemic hypertension in dogs and cats.. J Vet Intern Med 2018;32(6):1803–1822.
Drynan EA, Schier M, Raisis AL. Comparison of invasive and noninvasive blood pressure measurements in anesthetized horses using the Surgivet V9203.. Vet Anaesth Analg 2016;43(3):301–308.
Aleman M, Davis E, Williams DC, Madigan JE, Smith F, Guedes A. Electrophysiologic study of a method of euthanasia using intrathecal lidocaine hydrochloride administered during intravenous anesthesia in horses.. J Vet Intern Med 2015;29(6):1676–1682.
Bland JM, Altman DG. Agreement between methods of measurements with observations per individual.. J Biopharm Stat 2007;17(4):571–582.
Brown S, Atkins C, Bagley R, Carr A, Cowgill L, Davidson M. Guidelines for the identification, evaluation and management of systemic hypertension in dogs and cats.. J Vet Intern Med 2007;21:542–558.
Ying GS, Maguire MG, Glynn RJ, Rosner B. Calculating sensitivity, specificity, and predictive values for correlated eye data.. Investig Ophthalmol Vis Sci 2020;61:29.
Parry BW, McCarthy MA, Anderson GA, Gay CC. Correct occlusive bladder width for indirect blood pressure measurements in horses.. Am J Vet Res 1982;43(1):50–54.
Roach JK, Thiele RH. Perioperative blood pressure monitoring.. Best Pract Res Clin Anaesthesiol 2019;33(2):127–138.
Campitelli R, Ferrario M, Su F, Creteur J, Herpain A, Carrara M. Pulse wave analysis as a tool for the evaluation of resuscitation therapy in septic shock.. Physiol Meas 2023;44(10):105002.
Saugel B, Buhre W, Chew MS, Cholley B, Coburn M, Cohen B. Intra‐operative haemodynamic monitoring and management of adults having noncardiac surgery: a statement from the European Society of Anaesthesiology and Intensive Care.. Eur J Anaesthesiol 2025;42(6):543–556.
Papaioannou V, Papaioannou T. Rethinking fluid responsiveness during septic shock: ameliorate accuracy of noninvasive cardiac output measurements through evaluation of arterial biomechanical properties.. J Pers Med 2024;14(1):70.
Wilson KAT, Raisis AL, Drynan EA, Mosing M, Lester GD, Hayman J. Agreement between invasive blood pressure measured in centrally and peripherally in anesthetized horses.. Vet Anaesth Analg 2018;45(4):467–476.
Wilson KAT, Raisis AL, Drynan EA, Lester GD, Hosgood GL. Agreement between invasive blood pressures measured in three peripheral arteries in anaesthetized horses under clinical conditions.. Vet Anaesth Analg 2018;45(3):338–344.
Lindsay WA, Robinson GM, Brunson DB, Majors LJ. Induction of equine postanesthetic myositis after halothane‐induced hypotension.. Am J Vet Res 1989;50(3):404–410.