The Effect of Hypertension on the Response to Blood Loss in a Rodent Model

Abstract

Abstract.Objective: Hypertensive patients having higher baseline peripheral resistance and sympathetic tone than normotensive patients may have aberrant responses to hemorrhage. In an attempt to further characterize this clinical observation, the authors compared the hemodynamic and metabolic responses to hemorrhage between spontaneously hypertensive rats (SHR) and normotensive rats (NTR). Methods: Twenty adult rats (10 NTR and 10 SHR) were anesthetized with althesin via the intraperitoneal route. Femoral arteries were cannulated by cutdown. Twelve (6 SHR and 6 NTR) rats underwent controlled catheter hemorrhage of 25% of their total blood volumes. Eight rats (4 SHR and 4 NTR) served as nonhemorrhage controls. Mean arterial pressure (MAP) and base excess (BE) were measured prehemorrhage and then every 15 minutes for the next 120 minutes. Data were reported as mean Ϯ standard error of the mean (SEM). Group comparisons were analyzed by ANOVA with repeated values post-hoc by Bonferroni. Statistical significance was defined by an alpha = 0.05. Results: Immediately after hemorrhage, the SHR group experienced a significantly (p < 0.001) greater drop in MAP of 70 Ϯ 4% in the SHR vs 40 Ϯ 6% in the NTR. Blood pressure in the NTR returned to control values 15 minutes after hemorrhage, but the SHR remained relatively hypotensive for the entire length of the experiment. Base excess in the SHR decreased significantly (p < 0.004) by 8.2 Ϯ 2 mmol/L from control values, as compared with no changes in BE for the NTR. Conclusions: The authors observed significant differences in the response to hemorrhage between hypertensive and normotensive rats. Hypertensive rats experienced a more profound hemorrhagic shock insult than normotensives for the same degree of blood loss.

The Effect of Hypertension on Uncontrolled Hemorrhage in a Rodent Model

“…[4][5][6][7][8] At the level of vascular injury, hemorrhage volume may be limited in hypertensives by their higher vascular resistance 19 and a hypercoagulable state. 20 Higher vascular resistance and increases in coagulation may also explain hypertensives' greater sensitivity to blood loss.…”

The Effect of Hypertension on Uncontrolled Hemorrhage in a Rodent Model

“…A defect in the both the afferent and efferent limbs of the baroreflex response to blood loss has been documented in the SHR. [4][5][6][7][8] At the level of vascular injury, hemorrhage volume may be limited in hypertensives by their higher vascular resistance 19 and a hypercoagulable state. 20 Higher vascular resistance and increases in coagulation may also explain hypertensives' greater sensitivity to blood loss.…”

“…5 A recent experiment in our laboratory using a catheter-controlled hemorrhage model showed a more profound hemorrhagic shock insult in the SHR group as compared with normotensive Wistar-Kyoto rats (WKYs) after the same volume of blood loss. 6 A catheter-controlled hemorrhage model cannot completely describe hemorrhage from a vascular injury. Unlike a catheter-controlled hemorrhage, a vascular injury results in an uncontrolled hemorrhage with the potential for continued blood loss.…”

Hemodynamic responses and serum nitrite concentration during uncontrolled hemorrhagic shock in normotensive and hypertensive rats

“…Another study also demonstrated that hypertensive animals experienced more profound hemorrhagic shock compared with nor-motensive animals 15 . In this study, we used uncontrolled hemorrhagic shock model.…”

“…Experimental and clinical studies indicated that there is a defect in hemodynamic and baroreflex responses after hemorrhage in hypertensive subjects 6 . Furthermore, hypertensive animals have greater tissue ischemia such as liver, skeletal muscles and brain than normotensive 15 . Several circulating factors such as NO are involved in modulation of cardiovascular response to hemorrhagic shock 7 .…”