Effects of primary resuscitation from shock on distribution of myocardial blood flow

Exogenous nitric oxide induces protection during hemorrhagic shock

INTRODUCTION

This study analyzed the systemic and microvascular hemodynamic changes related to increased nitric oxide (NO) availability during the early phase of hemorrhagic shock. Hemodynamic responses to hemorrhagic shock were studied in the hamster window chamber.

MATERIALS AND METHODS

Exogenous NO was administered in the form of nitrosothiols (nitrosylated glutathione, GSNO) and was given prior the onset of hemorrhage. Moderate hemorrhage was induced by arterial controlled bleeding of 50% of the blood volume, and the hypovolemic shock was followed over 90 min.

RESULTS

Animals pre-treated with GSNO maintained systemic and microvascular conditions during hypovolemic hemorrhagic shock, when compared to animal treated with glutathione (GSH) or the Sham group. Low concentrations of NO released during the early phase of hypovolemic shock from GSNO mitigated arteriolar vasoconstriction, increased capillary perfusion and venous return, and improved cardiac function (recovered of blood pressure and stabilized heart rate). GSNO's effect on resistance vessels influenced intravascular pressure redistribution and blood flow, preventing tissue ischemia.

DISCUSSION

Increases in NO availability during the early phase of hypovolemic shock could preserve cardiac function and microvascular perfusion, sustaining organ function. Direct translation into a clinical scenario may be limited, although the pathophysiological importance of NO in the early phase of hypovolemia is clearly highlighted here.

Fluid resuscitation from severe hemorrhagic shock using diaspirin cross-linked hemoglobin fails to improve pancreatic and renal perfusion

BACKGROUND

Fluid resuscitation from hemorrhagic shock is intended to abolish microcirculatory disorders and to restore adequate tissue oxygenation. Diaspirin cross-linked hemoglobin (DCLHb) is a hemoglobin-based oxygen carrier (HBOC) with vasoconstrictive properties. Therefore, fluid resuscitation from severe hemorrhagic shock using DCLHb was expected to improve perfusion pressure and tissue perfusion of kidneys and pancreas.

METHODS

In 20 anesthetized domestic pigs with an experimentally induced coronary stenosis, shock (mean arterial pressure 45 mmHg) was induced by controlled withdrawal of blood and maintained for 60 min. Fluid resuscitation (replacement of the plasma volume withdrawn during hemorrhage) was performed with either 10% DCLHb (DCLHb group, n = 10) or 8% human serum albumin (HSA) oncotically matched to DCLHb (HSA group, n = 10). Completion of resuscitation was followed by a 60-min observation period. Regional blood flow to the kidneys and the pancreas was measured by use of the radioactive microspheres method at baseline, after shock and 60 min after fluid resuscitation.

RESULTS

All animals (10/10) resuscitated with DCLHb survived the 60-min observation period, while 5/10 control animals died within 20 min due to persisting subendocardial ischemia. In contrast to HSA survivors, pancreas and kidneys of DCLHb-treated animals revealed lower total and regional organ perfusion and regional oxygen delivery. Renal and pancreatic blood flow heterogeneity was higher in the DCLHb group.

CONCLUSION

DCLHb-induced vasoconstriction afforded superior myocardial perfusion, but impaired regional perfusion of the kidneys and the pancreas.

Hemoglobin-based oxygen carrier provides heterogeneous microvascular oxygenation in heart and gut after hemorrhage in pigs

BACKGROUND

In this study, the hypothesis was tested that resuscitation with hemoglobin-based oxygen carriers (HBOCs) affects the oxygenation of the microcirculation differently between and within organs. To this end, we tested the influence of the volume of an HBOC on the microcirculatory oxygenation of the heart and the gut serosa and mucosa in a porcine model of hemorrhage.

METHODS

In anesthetized open-chested pigs (n = 24), a controlled hemorrhage (30 mL/kg over 1 hour) was followed by resuscitation with 10, 20, or 30 mL/kg diaspirin-crosslinked hemoglobin (DCLHb) or isovolemic resuscitation with 30 mL/kg of a 6% hydroxyethyl starch solution (HAES). Measurements included systemic and regional hemodynamic and oxygenation parameters. Microvascular oxygen pressures (microPO2) of the epicardium and the serosa and mucosa of the ileum were measured simultaneously by the palladium-porphyrin phosphorescence technique. Measurements were obtained up to 120 minutes after resuscitation.

RESULTS

After hemorrhage, a low volume of DCLHb restored both cardiac and intestinal microPO2. Resuscitation of gut microPO2 with a low volume of DCLHb was as effective as isovolemic resuscitation with HAES. Higher volumes of DCLHb did not restore cardiac microPO2, as did isovolemic resuscitation with HAES, but increased gut microPO2 to hyperoxic values, dose-dependently. Effects were similar for the serosal and mucosal microPo2. In contrast to a sustained hypertensive effect after resuscitation with DCLHb, effects of DCLHb on regional oxygenation and hemodynamics were transient.

CONCLUSION

This study showed that a low volume of DCLHb was effective in resuscitation of the microcirculatory oxygenation of the heart and gut back to control levels. Increasing the volume of DCLHb did not cause an additional increase in heart microPO2, but caused hyperoxic microvascular values in the gut to be attained. It is concluded that microcirculatory monitoring in this way elucidates the regional behavior of oxygen transport to the tissue by HBOCs, whereas systemic variables were ineffective in describing their response.

Progesterone administration after trauma and hemorrhagic shock improves cardiovascular responses

OBJECTIVE

Studies have shown that female rats during the proestrus stage have significantly improved cell and organ functions after trauma-hemorrhage compared with male and ovariectomized females. This study investigated the hypothesis that progesterone can improve the depressed cardiovascular function in sex steroid-deficient female rats (i.e., ovariectomized females) after trauma-hemorrhage and resuscitation.

DESIGN

Prospective study.

SETTING

University laboratory.

SUBJECTS

Ovariectomized female Sprague-Dawley rats (weight, 250-300 g).

INTERVENTIONS

Rats underwent a 5-cm midline laparotomy (i.e., soft-tissue trauma), were bled to a mean arterial pressure of 35 mm Hg for approximately 90 mins, and were then resuscitated using Ringer's lactate. A single dose of progesterone (25 mg/kg of body weight) or vehicle was administered subcutaneously during resuscitation.

MEASUREMENTS

At 20 hrs after trauma-hemorrhage or sham operation, cardiac output and heart performance and the circulating blood volume were assessed using the indocyanine green dilution technique and a left ventricular catheter. Furthermore, the binding activity of progesterone receptors in nuclear extracts of left ventricular tissue was determined.

RESULTS

Cardiac output, heart performance, and circulating blood volume were significantly decreased in vehicle-treated animals after trauma-hemorrhage. Administration of progesterone significantly improved cardiac output and heart performance and increased the circulating blood volume. This was associated with an increased progesterone receptor activity in the left ventricular nuclear extracts.

CONCLUSION

Because administration of progesterone after trauma-hemorrhage in sex steroid-deficient females improved cardiovascular responses, this hormone seems to be a useful adjunct for the treatment of cardiovascular depression in postmenopausal and ovariectomized female trauma patients.

Haemodynamic and volumetric monitoring during haemorrhagic shock in swine

Various studies have been performed concerning haemodynamics in the shock state. The aim of this study was to examine if a haemodynamic approach based on volumetric indices can offer a new method of evaluation. Volumetric measurements of ventricular filling and cardiac function were compared with classical haemodynamic variables during induced haemorrhagic shock in swine. Twelve hybrid swine were anaesthetized and underwent arteriectomy to induce haemorrhagic shock. Blood was collected in ACD treated bags and reinfused via the same vein after a shock period of 90 min. Haemodynamic and volume measurements were evaluated. Seven swine survived to complete the protocol and reached the final experimental time (90 min after reinfusion), while the remaining five died 1 h after reinfusion. Concerning the haemodynamics, afterload changes characterized the haemorrhagic shock period, while blood volume distribution dictated ventricular filling and ventricular kinetics during the post-reinfusion period. Systemic vascular resistance was different in the two groups. This study suggests that blood volumetric evaluations can offer better comparative data than pulmonary catheterisation for a precise assessment of cardiac output. Preload values have turned out to be of greater relevance than traditional pressure variables.