The effect of hypertension on uncontrolled hemorrhage in a Rodent model

Patients with essential hypertension (EH) have higher mortality rates from hemorrhage. How the complex physiologic changes seen in EH affect the response to uncontrolled hemorrhage has yet to be adequately described. Objective: To test the null hypothesis that there would be no difference in the hemorrhage volumes and hemodynamic responses to uncontrolled hemorrhage between hypertensive rats (SHRs) and normotensive rats (WKYs). Methods: Twenty-four adult rats (12 WKYs and 12 SHRs) were anesthetized with althesin via the intraperitoneal route. The femoral artery was cannulated by cutdown for mean arterial pressure (MAP) measurement and blood gas sampling. Twelve rats (6 WKYs and 6 SHRs) underwent uncontrolled hemorrhage by 50% tail amputation. Twelve rats (6 WKYs and 6 SHRs) served as non-hemorrhage controls. The MAP, base excess (BE), and cumulative blood loss were measured pre-hemorrhage and then every 15 minutes post-hemorrhage for 90 minutes. Data were reported as mean ± standard error of the mean. Comparisons between control and uncontrolled hemorrhage groups were analyzed by analysis of variance (ANOVA) with repeated-measures post-hoc testing by Bonferroni. Statistical significance was defined by an alpha = 0.05. Results: Mortality rates were significantly higher (p < 0.05) for the SHRs (100%) as compared with the WKYs (33%). Changes in time-averaged MAP post-hemorrhage were significantly greater (p < 0.001) in the SHR group (88 ± 10 mm Hg) as compared with the WKY group (48 ± 4 mm Hg). Hemorrhage volume was significantly lower (p = 0.02) in the SHR group (3.7 ± 0.5 mL) as compared with the WKY group (6.1 ± 0.7 mL). Conclusions: Hypertensive rats had a higher mortality rate than normotensives from a comparable vascular injury with lower hemorrhage volumes.