Enteral gabexate mesilate improves volume requirements and autonomic cardiovascular function after experimental trauma/hemorrhagic shock in the absence of blood reperfusion

Abstract

The standard of care for fluid resuscitation of trauma/hemorrhagic shock (T/HS) is the infusion of blood. However, in many instances, blood product transfusion may not be feasible. Consequently, crystalloid solutions may be utilized as temporizing cost-effective resuscitation fluids. In this study, we explored an alternative therapeutic strategy of enteral protease inhibition adjunctive to intravenous Lactated Ringer's (LR) reperfusion after T/HS. Male Wistar rats underwent midline laparotomy (trauma) and an enteral catheter was inserted orally and positioned post-pyloric for the infusion of vehicle (Golytely®) with or without the serine protease inhibitor gabexate mesilate (GM) (n=8/group). Hemorrhagic shock was induced by blood removal to reduce the mean arterial blood pressure (MAP) to 35-40 mmHg for 90 minutes, before resuscitation with LR. Animals treated with enteral GM required significantly less crystalloid volume to achieve hemodynamic stability and displayed improvements in both blood pressure and autonomic function (via increased baroreflex sensitivity to vasopressors, heightened vascular sympathetic modulation, elevated levels of circulating catecholamines, and increased α1-adrenergic receptor density) compared to untreated (control) shocked animals. Resistance arteries isolated from healthy donor animals and perfused with plasma from untreated T/HS animals revealed impaired vascular response to the α1 adrenergic agonist phenylephrine and decreased reactivity to sodium nitroprusside that was preserved in the GM-treated group. These findings suggest that blockade of serine proteases within the intestinal lumen in non-blood resuscitated experimental T/HS preserves and enhances peripheral sympathetic modulation, improving hemodynamics. Enteral infusion of gabexate mesilate may be a new and promising approach to the management of trauma/hemorrhagic shock.

Keywords: Trauma/hemorrhagic shock; autonomic cardiovascular function; enteral protease inhibition; gabexate mesilate.

Figure 1

Hemodynamics. Time-course of arterial blood pressure (A-systolic, B-diastolic, and C-mean) and heart rate (D) of enteral GM-treated group (GM) and untreated shock group (Untreated). ***P<0.0001 GM vs. Untreated at the same time-point by two-way ANOVA.

Figure 2

Baroreflex sensitivity. Comparison of blood pressure increases at baseline and 120 minutes after reperfusion (r120) in response to in vivo phenylephrine (Phe) infusion (A) and subsequent bradycardic response index mediated by baroreflex (B). Comparison of blood pressure decreases in response to in vivo sodium nitroprusside (SNP) infusion (C) and subsequent tachycardic response index mediated by baroreflex (D) in the enteral GM-treated (GM) and the untreated groups (Untreated). *P<0.01 GM vs. Untreated at the same time-point, #P<0.01, ##P<0.001, and ###P<0.0001, r120 vs. baseline in the same group by two-way ANOVA.

Figure 3

Blood pressure variability and catecholamines level. Time course of systolic arterial pressure variability (A), sympathetic modulation (B), and plasma catecholamine levels: epinephrine (C) and norepinephrine (D) at baseline, after the hypotensive period (shock), 30 minutes after reperfusion (r30), and 120 minutes after reperfusion (r120) in enteral GM-treated (GM) and Untreated groups. *P<0.01 and ***P<0.0001 GM vs. Untreated at the same time-point by two-way ANOVA.

Figure 4

Vascular reactivity. Concentration response curves in ex vivo isolated mesenteric artery segments after T/HS. Phenylephrine (Phe) induced contraction of arteries from shocked animals incubated with Krebs solution (A) or healthy donor arteries incubated with plasma from shocked animals (B); Sodium Nitroprusside (SNP) induced relaxation of arteries from shocked animal in Krebs solution (C) and healthy donor arteries incubated with plasma from shocked animals (D) in the enteral GM-treated (GM) and Untreated groups. The dotted lines represent the normal behavior of a healthy vessel in Krebs solution (A and C) or incubated with healthy plasma (B and D) (not included in the statistical analysis). Note that in general, there is an improved vascular response to stimuli in the presence of plasma compared to Krebs solution. *P<0.01, **P<0.001, and ***P<0.0001 GM vs. Untreated at the same concentration by two-way ANOVA.

Figure 5

Immunofluorescence for α1-adrenergic receptor. Representative images of α1-adrenergic receptor fluorescence on pulmonary artery smooth muscle cells incubated with plasma from healthy animals (Healthy Control), hemorrhagic shock (Untreated), and enteral GM-treated (GM) groups (A). Average fluorescence intensities (B) and fluorescence intensity normalized to Healthy control (C). The dotted line represents 100% intensity in the Healthy Control. #P<0.01 Untreated vs. Healthy Control, *P<0.01 GM vs. Untreated by one-way ANOVA, and **P<0.001 GM vs. Untreated by unpaired t-test.