Do different rates of fluid resuscitation adversely or beneficially influence immune responses after trauma-hemorrhage?

Fluid restriction reduces pulmonary edema in a model of acute lung injury in mechanically ventilated rats

Experimental acute lung injury models are often used to increase our knowledge on the acute respiratory distress syndrome (ARDS), however, existing animal models often do not take into account the impact of specific fluid strategies on the development of lung injury. In contrast, the current literature strongly suggests that fluid management strategies have a significant impact on clinical outcome of patients with ARDS. Thus, it is important to characterize the role of fluid management strategies in experimental models of lung injury. In this study we investigated the effect of two different fluid strategies on commonly used outcome variables in a short-term model of acute lung injury, in relation to age. Infant (2–3 weeks) and adult (3–4 months) Wistar rats received intratracheal instillations of lipopolysaccharide and 24 hours later were mechanically ventilated for 6 hours. During mechanical ventilation, rats from both age groups were randomized to either a standard or conservative intravenous fluid strategy. We found that the hemodynamic response in infant and adult rats was similar in both fluid strategies. Lung wet-to-dry ratios were lower in adult, but not in infant rats receiving the conservative fluid strategy as compared to the standard fluid strategy. There were age-related differences in markers of alveolar capillary barrier disruption and alveolar fluid clearance, yet these were unaffected by fluid strategy. Finally, we found significantly higher IL-1β and TNF-α concentrations in the adult rats treated with the conservative as compared to the standard fluid regimen. In conclusion, the choice of fluid strategy in mechanically ventilated rats with experimental LPS-induced acute lung injury has a significant effect on pulmonary extravascular water, an important and well-recognized lung injury marker, and on the local pro-inflammatory cytokine profiles. We advocate the use of a more uniform, conservative, fluid strategy regimen in experimental models of acute lung injury.

Does the infusion rate of fluid affect rapidity of mean arterial pressure restoration during controlled hemorrhage

OBJECTIVE

This study aimed to compare 2 fluid infusion rates of lactated Ringer (LR) and hydroxyethyl starch (HES) 130/0.4 on hemodynamic restoration at the early phase of controlled hemorrhagic shock.

METHODS

Fifty-six anesthetized and ventilated piglets were bled until mean arterial pressure (MAP) reached 40 mm Hg. Controlled hemorrhage was maintained for 30 minutes. After this period, 4 resuscitation groups were studied (n=14 for each group): HES infused at 1 or 4mL/kg per minute or LR1 infused at 1 or 4mL/kg per minute until baseline MAP was restored. Hemodynamic assessment using PiCCO monitoring and biological data were collected.

RESULTS

Time to restore baseline MAP ±10% was significantly lower in LR4 group (11±11 minutes) compared to LR1 group (41±25 minutes) (P=.0004). Time to restore baseline MAP ±10% was significantly lower in HES4 group (4±3 minutes) compared to HES1 (11±4 minutes) (P=.0003). Time to restore baseline MAP ±10% was significantly lower with HES vs LR whatever the infusion rate. No statistically significant difference was observed in cardiac output, central venous saturation, extravascular lung water, and arterial lactate between 4 and 1 mL/kg per minute groups.

CONCLUSIONS

In this controlled hemorrhagic shock model, a faster infusion rate (4 vs 1mL/kg per minute) significantly decreased the time for restoring baseline MAP, regardless of the type of infused fluid. The time for MAP restoration was significantly shorter for HES as compared to LR whatever the fluid infusion rate.

Effects of volume and composition of the resuscitative fluids in the treatment of hemorrhagic shock

Objectives:

To evaluate the effectiveness of normal saline, hypertonic saline, and Ringer's lactate solution followed by blood infusion in ameliorating the physiological, biochemical, and organ functions following hemorrhagic shock (HS) in rats.

Materials and Methods:

Anesthetized, male Sprague-Dawley rats underwent computer-controlled HS, and were randomly divided into five groups consisting of (1) sham, (2) HS without resuscitation, (3) resuscitation with normal saline, (4) resuscitation with hypertonic saline, and (5) resuscitation with Ringer's lactate solution. All resuscitated animals were infused with subsequent infusion of shed blood. Animals were continuously monitored for physiological, hemodynamic, biochemical parameters, and organ dysfunctions.

Results:

Non-resuscitated animals were unable to survive due to hypotension, poor oxygen metabolism, and lactic acidosis. Although these HS related parameters were corrected by all the fluids used in this study, additional blood infusion was more effective than fluid resuscitation alone. Also, hypertonic saline was more effective than Ringer's lactate solution, and normal saline was the least effective in preserving the liver and kidney functions and muscle damage.

Conclusions:

All crystalloid fluids were significantly more effective in reversing the HS outcome when used with blood infusion, but hypertonic salinewith blood was more effective in preventing the organ damage than Lactated Ringers solutions or normal saline in the treatment of HS.

Role of hemorrhage in the induction of systemic inflammation and remote organ damage: analysis of combined pseudo-fracture and hemorrhagic shock

This study was performed to analyze the role of hemorrhage-induced hypotension in the induction of systemic inflammation and remote organ dysfunction. Male C57/BL6 mice (6- to 10-week old and 20-30 g) were used. Animals were either subjected to pseudo-fracture [PF; standardized soft-tissue injury and injection of crushed bone, PF group: n = 9], or PF combined with hemorrhagic shock (HS + PF group: n = 6). Endpoint was 6 h. Systemic inflammation was assessed by IL-6 and IL-10 levels. Myeloperoxidase (MPO) and NF-κB activity in the lung and liver tissue were obtained to assess remote organ damage. The increases of systemic cytokines are similar for animals subjected to PF and PF + HS (IL-6: 189 pg/ml ± 32.5 vs. 160 pg/ml ± 5.3; IL-10: 60.3 pg/ml ± 15.8 vs. 88 pg/ml ± 32.4). Furthermore, the features (ALT; NF-κB) of liver injury are equally elevated in mice subjected to PF (76.9 U/L ± 4.5) and HS + PF (80 U/L ± 5.5). Lung injury, addressed by MPO activity was more severe in group HS + PF (2.95 ng/ml ± 0.32) than in group PF (1.21 ng/ml ± 0.2). Both PF and additional HS cause a systemic inflammatory response. In addition, hemorrhage seems to be associated with remote affects on the lung.

Hypertonic sodium pyruvate solution is more effective than Ringer's ethyl pyruvate in the treatment of hemorrhagic shock

Hypertonic sodium pyruvate (HSP), as well as ethyl pyruvate solutions, has been proposed as resuscitative fluids in the treatment of hemorrhagic shock (HS) because of their anti-inflammatory and antioxidant properties. The effectiveness of one pyruvate preparation over the other in the treatment of HS has not been evaluated. The authors aimed to compare two pyruvate solutions for resuscitation and their mechanisms of action in rats during HS. The effects of infusion of low-volume HSP were compared against high-volume Ringer's ethyl pyruvate on hemodynamic parameters, inflammatory cascade, and regulation of stress and apoptosis-related proteins in the liver. Sprague-Dawley rats were either treated as sham animals or subjected to computer-controlled arterial hemorrhage (40 mmHg) for 60 min followed by resuscitation with isotonic sodium chloride solution, hypertonic saline, Ringer's lactate solution, Ringer's ethyl pyruvate, or HSP for 60 min. Animals were continuously monitored for hemodynamic and biochemical parameters in blood. At the end of the experiment, animals were killed, and liver samples were taken for the evaluation of inflammatory and anti-inflammatory markers and mediators of oxidative stress, liver injury, and expression of apoptotic signaling proteins. In comparison with Ringer's ethyl pyruvate, HSP administration after hemorrhage reduced liver injury, which was associated with increased levels of serum and tissue inflammatory cytokines, inflammatory mediators such as NOS and cyclooxygenase 2, lipid peroxidation, and higher hepatocellular adenosine triphosphate. Cellular apoptotic events related to the activation of caspase-3 and poly(ADP-ribose)polymerase cleavage were also decreased by sodium pyruvate. Resuscitation with small-volume HSP offers significant protection against inflammatory and oxidative stress and in preventing liver injury compared with large-volume Ringer's ethyl pyruvate.

Advances in resuscitation strategies

Shock, regardless of etiology is characterized by decreased delivery of oxygen and nutrients to the tissues and our interventions are directed towards reversing the cellular ischemia and preventing its consequences. The treatment strategies that are most effective in achieving this goal obviously depend upon the different types of shock (hemorrhagic, septic, neurogenic and cardiogenic). This brief review focuses on the two leading etiologies of shock in the surgical patients: bleeding and sepsis, and addresses a number of new developments that have profoundly altered the treatment paradigms. The emphasis here is on new research that has dramatically altered our treatment strategies rather than the basic pathophysiology of shock.

Fluid resuscitation: past, present, and the future

Hemorrhage remains a major cause of preventable death following both civilian and military trauma. The goals of resuscitation in the face of hemorrhagic shock are restoring end-organ perfusion and maintaining tissue oxygenation while attempting definitive control of bleeding. However, if not performed properly, resuscitation can actually exacerbate cellular injury caused by hemorrhagic shock, and the type of fluid used for resuscitation plays an important role in this injury pattern. This article reviews the historical development and scientific underpinnings of modern resuscitation techniques. We summarized data from a number of studies to illustrate the differential effects of commonly used resuscitation fluids, including isotonic crystalloids, natural and artificial colloids, hypertonic and hyperoncotic solutions, and artificial oxygen carriers, on cellular injury and how these relate to clinical practice. The data reveal that a uniformly safe, effective, and practical resuscitation fluid when blood products are unavailable and direct hemorrhage control is delayed has been elusive. Yet, it is logical to prevent this cellular injury through wiser resuscitation strategies than attempting immunomodulation after the damage has already occurred. Thus, we describe how some novel resuscitation strategies aimed at preventing or ameliorating cellular injury may become clinically available in the future.

Controversies in Fluid Resuscitation

The optimal degree of resuscitation in the initial control and resuscitative phase of trauma care remains unclear. Many attempts have been made with animal studies to determine the optimal degree and method of resuscitation. Human studies were first conducted in 1994 and the results were inconclusive and have not been replicated. The question of the volume, rate, and type of fluid to be infused for initial control and adequate resuscitation of the trauma patient remains to be answered.

Delayed fluid resuscitation in hemorrhagic shock induces proinflammatory cytokine response

STUDY OBJECTIVE

This study is designed to determine the effects of delayed fluid resuscitation on the hemodynamic changes and cytokine responses in a rat model of hemorrhagic shock.

METHODS

Wistar male rats (n=40; 8/group) were subjected to a volume-controlled hemorrhagic shock for 30 minutes and received lactated Ringer's solution resuscitation as follows: (1) immediate resuscitation, (2) delayed resuscitation begun 30 minutes after hemorrhage (delayed resuscitation 30), (3) delayed resuscitation begun 45 minutes after hemorrhage (delayed resuscitation 45), (4) delayed resuscitation begun 60 minutes after hemorrhage (delayed resuscitation 60), or (5) unresuscitated group, induction of hemorrhagic shock without resuscitation. Hemodynamic parameters were recorded and blood samples were collected at 0 minutes and at 30, 90, 150, 210, 270, and 330 minutes after hemorrhage for plasma levels of interleukin (IL) 6, IL-10 and tumor necrosis factor alpha (TNF-alpha). Repeated-measurement analysis of variance was used for within- and between-groups comparisons.

RESULTS

Final mean blood pressure, serum levels of lactate, and hematocrit levels after immediate resuscitation were not different from those in the delayed resuscitation groups. Comparing with the unresuscitated group, TNF-alpha and IL-6 concentrations were significantly higher, whereas IL-10 concentrations were significantly lower in the 4 resuscitation groups. Circulating concentrations of IL-6 were significantly higher in the delayed resuscitation 45 (P<.001) and delayed resuscitation 60 (P<.001) groups. Circulating concentrations of TNF-alpha and IL-10 in the 4 resuscitation groups were comparable throughout the experimental period.

CONCLUSION

Delayed fluid resuscitation in hemorrhagic shock induces increased production of proinflammatory cytokines, and the release of cytokine was correlated with the time delayed for resuscitation.

Differential fluid regulation during and after soft tissue trauma and hemorrhagic shock in males and proestrus females

Gender differences in immune and organ functions have been described in different rodent models of trauma- and pressure-controlled hemorrhagic shock. We hypothesized that gender influences the regulation of plasma and tissue fluids in rats under such conditions. To study this we used male and weight matched proestrus female Sprague-Dawley rats, which were assigned to three groups (n = 7/group): sham, maximal bleedout (trauma and 45 min of blood pressure at 35 mmHg without resuscitation), or 5 h after completion of trauma-hemorrhage and resuscitation. Trauma-hemorrhage involved midline laparotomy and approx. 90 min of hemorrhagic shock (35 mmHg), followed by fluid resuscitation (4x the shed blood volume with Ringers lactate). (51)Cr-EDTA, (125)I-albumin distribution, and wet weight/dry weight were used to calculate plasma volume and extracellular fluid volume and cellular water content. Proestrus female rats showed significantly higher plasma volumes compared with weight-matched males. The volume of blood withdrawn in the first 15 min of hemorrhagic shock was significantly less in proestrus females compared with males; however, there was no significant difference in the total shed blood volume. Moreover, proestrus females showed less interstitial edema formation compared with male rats at 5 h after resuscitation. We conclude that differences in the regulation of plasma and tissue volumes exist between males and proestrus females during and after trauma-hemorrhage. The increased circulating blood volume could contribute the improved immune and organ functions in proestrus females under those conditions.

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.

The association between gender and mortality among trauma patients as modified by age

BACKGROUND

Several studies have reported a null association between gender and mortality after traumatic injury, whereas others found an age-specific association between male gender and increased mortality. Relatively small sample sizes may have contributed to the heterogeneity among existing studies; therefore, a large-sample-size study was undertaken.

METHODS

The National Trauma Data Bank was queried, yielding data for over 150,000 patients involved in blunt or penetrating trauma. Crude and adjusted odds ratios (ORs) and 95% confidence intervals (CIs) were calculated for the association between gender and mortality, both overall and according to mechanism of injury and age categories.

RESULTS

Among those who sustained blunt trauma, male patients had a significant increase in the risk of death compared with female patients (OR, 1.49; 95% CI, 1.39-1.59) that was most apparent for those > or = 50 years of age (OR, 1.97; 95% CI, 1.84-2.11). For penetrating trauma patients, essentially no significant association, either overall (OR, 1.03; 95% CI, 0.91-1.17) or by age category, was apparent.

CONCLUSION

This study found an association between gender and mortality among blunt trauma patients, particularly those aged > or = 50 years. Animal studies demonstrate that the sex hormones influence the inflammatory response to injury. These results may highlight the importance of sex hormones in traumatic injury outcomes.

Effects of colloidal resuscitation fluids on the neutrophil respiratory burst

BACKGROUND

Experimental studies have revealed that gelatin and HES produce increased neutrophil respiratory burst activity. It was investigated whether 3-percent gelatin (MW 35,000) and three types of 6-percent HES (MW 70,000; degree of substitution, 0.5; 200,000/0.5; 450,000/0.7) preparations can influence superoxide anion production during respiratory burst under clinical conditions.

STUDY DESIGN AND METHODS

Blood samples were obtained from 40 patients before and 1 hour after the infusion, before anesthesia and surgical treatment. After stimulation with bacteria (Escherichia coli), the respiratory burst was measured by oxidation of nonfluorescent dihydrorhodamine 123 to the fluorescent rhodamine 123 by the use of flow cytometry.

RESULTS

Respiratory burst activity decreased significantly (p = 0.004) from the baseline (60.0 +/- 6.5%) to 1 hour after the administration of the low-molecular-weight HES preparation (55.0 +/- 6.8%). No significant differences in respiratory burst activity could be found after the administration of gelatin or medium-molecular-weight or high- molecular-weight HES solution.

CONCLUSION

The investigated administration of gelatin and medium- and high-molecular-weight HES preparations did not influence respiratory burst activity under clinical conditions. However, the neutrophil respiratory burst was impaired after the administration of low-molecular-weight HES. Neutrophil respiratory burst activity may vary according to the type of colloidal plasma substitutes administered.

Insight into the mechanism by which metoclopramide improves immune functions after trauma-hemorrhage

Although studies have shown that prolactin (Prl) and metoclopramide (Mcp) administration restores the depressed cell-mediated immune functions after hemorrhage, the underlying mechanism responsible for the immunostimulatory effects of Mcp remains unknown. We hypothesized that Mcp improves immune responses by upregulating the secretion of Prl. To test this hypothesis, male C3H/HeN mice were subjected to sham operation or laparotomy (i.e., soft tissue trauma) and hemorrhagic shock (Hem; 35 +/- 5 mmHg for 90 min) and then resuscitated. Plasma Prl levels were determined 30 min after Mcp (1 microgram/g body wt sc at end of Hem) or vehicle (Veh) treatment in sham and Hem mice. The results indicate that plasma Prl levels increased significantly in Mcp-treated mice (sham-Veh 249.9 +/- 5.3, Hem-Veh 229.9 +/- 7.6, Hem-Mcp 596.9 +/- 73.1 ng/ml, one-way ANOVA, P < 0.05 vs. Veh). To determine whether Mcp produces its salutary effects directly or indirectly via increased Prl secretion, splenocyte proliferation and splenocyte interleukin (IL)-2 and IL-3 release from untreated sham or Hem mice were determined in the presence of increasing concentrations of mouse Prl or Mcp. The addition of Mcp had no effect on splenocyte immune functions in vitro. However, the addition of Prl restored the hemorrhage-induced depressed splenocyte proliferation as well as splenocyte IL-2 and IL-3 release in vitro in a dose-dependent manner. Thus the beneficial effects of Mcp on immune functions after Hem appear to be mediated by Prl. Because Mcp increases plasma levels of the immunoenhancing hormone Prl, this agent should be considered a useful adjunct for the treatment of immunodepression in trauma victims.

Prehospital trauma care

Concepts regarding uniform reporting of data after trauma and regarding treatment of brain trauma patients at the scene have recently been agreed upon in consensus processes. Endotracheal intubation and alternatives are as controversially discussed as fluid resuscitation and helicopter transport of trauma victims. Long-term outcomes of trauma patients should more frequently be studied using the Quality of Wellbeing Scale.

[Vascular loading in the first 24 hours following severe head injuries]

The main goal at the acute phase of head injury is to prevent a decrease in blood pressure, which promotes cerebral ischemia. Volume loading is therefore frequently indicated. A normal or increased plasma osmolarity should be maintained. Thus hypotonic fluids should be avoided. Hyperglycaemia is also a risk factor for brain injury and glucose use has to be restricted in the first hours after trauma. Isotonic saline 0.9% is the first solution to be infused. Lactated Ringer solutions are mildly hypotonic as approximately 114 mL of free water is contained in each litre of the solution. Isotonic colloids are indicated to replace blood losses, but have no advantage over cristalloids, concerning the development of cerebral oedema. Fluid restriction minimally affects cerebral edema. Because of the severe consequences of hypovolaemia and hypotension, fluids should not be restricted until haemodynamic stability is achieved. Hypertonic fluids rapidly restore intravascular volume and decrease intracranial pressure. Although they probably have a place in prehospital intensive therapy, the demonstration of their benefit is still lacking. Monitoring of intravascular volume is essential. Continuous arterial pressure and central venous pressure monitoring are mandatory. New monitoring techniques as the measurement of systolic pressure variations or transoesophageal Doppler echocardiography will probably find a place in the management of trauma patients in the near future.

End-points of resuscitation how much is enough?

Fluid resuscitation after traumatic hemorrhage has historically been instituted as soon after injury as possible. Patients suffering from hemorrhagic shock may receive several liters of crystalloid, in addition to colloid solutions, in an attempt to normalize blood pressure, heart rate, urine output, and mental status, which are the traditional end-points of resuscitation. Current theory and recent investigations have questioned this dogma. Resuscitation goals may be different between when the patient is actively hemorrhaging, and once bleeding has been controlled. Newer markers of tissue and organ system perfusion may allow a more precise determination of adequate resuscitation.