Agreement of Doppler Ultrasound and Visual Sphygmomanometer Needle Oscillation with Invasive Blood Pressure in Anaesthetised Dogs

Visual sphygmomanometer needle oscillation (SNO) can occur before audible return of pulsatile flow (ARPF) when measuring blood pressure by Doppler ultrasound. The aim was to assess the agreement of SNO and ARPF with invasive blood pressure (iABP) in a clinical population of anaesthetised dogs. A total of 35 dogs undergoing surgery in dorsal recumbency necessitating arterial cannulation were included. Paired measurements of iABP and SNO, and iABP and ARPF, were collected. The agreement of non-invasive blood pressure (NIBP) and iABP measurements was analysed with concordance correlation coefficients (CCCs) and Bland–Altman plots. The proportions of SNO and ARPF measurements between 10 and 20 mmHg of iABP were compared. Both SNO and ARPF demonstrated greater agreement with invasive systolic (iSAP) than invasive mean (iMAP) pressures, and SNO demonstrated greater agreement with iSAP than ARPF measurements. The mean differences (95% limits of agreement) for SNO and APRF were −9.7 mmHg (−51.3–31.9) and −13.1 mmHg (−62.2–35.9), respectively. The CCC (95% CI) for SNO was 0.5 (0.36–0.64) and ARPF was 0.4 (0.26–0.54). A significantly greater proportion of SNO measurements were within 20 mmHg of iSAP compared to ARPF. Both NIBP techniques performed more poorly than veterinary consensus recommendations for device validation. Caution should be used clinically when interpreting values obtained by Doppler ultrasound in anaesthetised dogs.