Survey of resting blood pressure values in clinically normal horses

Resting coccygeal blood pressure values were measured, indirectly, on 296 horses (97 Thoroughbreds, 97 Standardbreds and 102 hacks). Blood pressure was found to vary with the class of horse examined; on average Thoroughbreds had significantly higher values than Standardbreds and hacks, whereas blood pressures of the last two groups were not significantly different. There was no demonstrable effect of sex, height or heart rate on blood pressure, but temperature and age did influence the value recorded. Mean (+/- sd) (n = 296) coccygeal uncorrected values (systolic pressure/diastolic pressure) were 112.1 +/- 16.5/77.3 +/- 14.3 mmHg. Allowing for bladder width to tail girth ratios used in each measurement, actual coccygeal pressures of 122.8 +/- 18.6/71.0 +/- 13.4 mmHg were determined. The latter corresponded to values of 149.4 +/- 19.0/97.6 +/- 14.0 mmHg, when corrected to heart (shoulder) level. Normal limits (defined as within 2.5th and 97.5th percentiles) for all horses, regardless of class, were 80 to 144 mmHg/49 to 105 mmHg for coccygeal uncorrected values and 86 to 159 mmHg/45 to 97 mmHg adjusted for bladder width to tail girth ratio.