Effects of hypertension on hemodynamic response and serum nitrite concentration during graded hemorrhagic shock in rats

BACKGROUND: Hypertensive patients have higher morbidity and mortality from hemorrhage. In this study, we investigated hemodynamic responses and serum nitrite concentrations during graded hemorrhagic shock and resuscitation in hypertensive (HT) and normotensive (NT) rats. METHODS: Thirteen male rats were divided into two groups, namely HT (n = 6) and NT (n = 7). Hypertension was induced by deoxycorticosterone acetate (DOCA)-salt method in uninephrectomized rats. After 8 weeks, graded hemorrhagic shock was induced during 34 minutes in four steps separated by 8-minute intervals (totally 16 ml/kg). The animals were kept in this condition for 120 minutes (shock period). Then, they were resuscitated with blood withdrawal. Mean arterial pressure (MAP) and heart rate (HR) were measured throughout the experiment. Blood samples were taken before and after shock induction and at the end of the shock period. RESULTS: HT rats experienced more MAP and HR reduction during the shock period and less improvement of hemodynamic response after resuscitation compared with the NT group (p < 0.05). The survival rate 72 hours post-hemorrhage in the HT group was significantly lower than the NT group (16.7% vs. 71.4%, respectively) (p < 0.05). Serum nitrite level in HT animals was lower than the NT group (2.45 ± 0.18 vs. 3.35 ± 0.26 ΅mol/lit, respectively; p < 0.05). In addition, it increased during the shock period in both NT and HT groups (p > 0.05). CONCLUSIONS: More reduction of MAP after hemorrhagic shock, less improvement of MAP and HR after resuscitation and low survival rate in HT animals suggested the impairment of cardiovascular system adaptation of HT animals during blood loss and it should be considered in management of hypertensive subjects.