The lack of a sensitive, practical bedside test for hypovolemia has rekindled interest in the shock index (heart rate divided by systolic blood pressure). Here, we compare the effect of blood donation on standing shock index values with its effect on values for the supine shock index and orthostatic change in shock indicies (OCSI).Methods:
This is a re-analysis of data collected for an earlier report. Data were available from 292 adults below age 65 and 44 adults ages 65 and over, donating 450 mL of blood. We obtained supine and standing vital signs before and after donation and then calculated 95% confidence intervals for differences based on the t-distribution.Results:
Blood donation resulted in a mean increase in the standing shock index of 0.09 [95% CI, 0.08–0.11] in younger adults and 0.08 [95% CI, 0.05–0.11] in older adults. These changes were similar to those noted for OCSI (young, 95% CI, 0.08–0.10; old, 95% CI, 0.04–0.10). Supine shock index values did not change with donation in younger donors (mean difference 0.0 [95% CI, 0.0–0.01]) or older donors (mean difference 0.0 [95% CI, − 0.01–0.03]).Conclusion:
Blood donation does not affect the supine shock index, but it does result in changes in standing shock index that are similar to changes in more complicated orthostatic vital signs.