Portal vein velocity (PVV) is a useful indirect indicator of portal pressure. Reference values for PVV have been previously established in healthy, non-sedated dogs with reported ranges of 14.7 ± 2.5 and 18.1 ± 7.6 cm/s. PVV may be influenced by physiological and pathological factors; for example, a correlation between body weight and PVV has been documented; however, the effect of other factors is unknown. The primary aims of this prospective comparative study were to investigate the effect of standardized intravenous sedation protocol of medetomidine (2-3 µg/kg) and butorphanol (0.3 mg/kg) on PVV and to determine whether post-sedation PVV results would fall below the portal hypertension threshold of 10 cm/s. Six triplex-Doppler PVV measurements were obtained pre- and post-sedation on 15 client-owned dogs undergoing abdominal ultrasonography for conditions unrelated to primary liver disease. The mean PVV pre-sedation was 14.9 ± 3.98 cm/s and 3-min post-sedation was 10.4 ± 3.73 cm/s, representing a statistically significant reduction in PVV (p < 0.001). The mean PVV was below 10 cm/s in 3/15 (20%) dogs pre-sedation and below 10 cm/s in 9/15 (60%) dogs post-sedation. There was no effect of age, sex, or weight on PVV before and/or after sedation. Sedation with medetomidine and butorphanol caused a significant reduction in PVV at 3-min post-administration. This finding should be considered when evaluating hepatic and portal hemodynamics in dogs, as 60% (9/15) of the sedated cases with presumed normal hepatic function exhibited post-sedation PVV at levels seen with portal hypertension.
Jamont et al. (Mon,) studied this question.