Effects of different resuscitation fluids on acute lung injury in a rat model of uncontrolled hemorrhagic shock and infection

Colloids and the Microcirculation

Colloid solutions have been advocated for use in treating hypovolemia due to their expected effect on improving intravascular retention compared with crystalloid solutions. Because the ultimate desired effect of fluid resuscitation is the improvement of microcirculatory perfusion and tissue oxygenation, it is of interest to study the effects of colloids and crystalloids at the level of microcirculation under conditions of shock and fluid resuscitation, and to explore the potential benefits of using colloids in terms of recruiting the microcirculation under conditions of hypovolemia. This article reviews the physiochemical properties of the various types of colloid solutions (eg, gelatin, dextrans, hydroxyethyl starches, and albumin) and the effects that they have under various conditions of hypovolemia in experimental and clinical scenarios.

Immune recovery after fluid resuscitation in rats with severe hemorrhagic shock

OBJECTIVE

To investigate the effects of resuscitation with normal saline (NS), hypertonic saline (HTS), and hydroxyethyl starch (HES) on regulatory T cells (Tregs), helper T 1 (Th1)/Th2 and cytotoxic T 1 (Tc1)/Tc2 profiles in the treatment of hemorrhagic shock.

METHODS

Rats subjected to severe hemorrhagic shock were resuscitated for 30 min with NS (n=8), HTS (n=8), or HES (n=8); sham (n=8) and naive control (n=8) groups were used for comparison. Following fluid resuscitation, the whole shed blood was reinfused for 30 min, and the rats were observed with continuous hemodynamic monitoring for 120 min. CD4⁺CD25⁺Foxp3⁺ Treg proportions, Th1/Th2 and Tc1/Tc2 profiles in spleen were analyzed by three-color flow cytometry.

RESULTS

The proportion of CD4⁺CD25⁺Foxp3⁺ Tregs and ratios of Th1/Th2 and Tc1/Tc2 did not differ among control, sham, and HTS groups, but were significantly lower in NS and HES groups (both P<0.05 vs. sham); NS and HES levels were similar. The level of Tc1 was significantly increased in HTS (P<0.05 vs. sham), and levels of Tc2 were increased in NS, HES, and HTS groups compared to sham (all P<0.05), but did not differ from each other.

CONCLUSIONS

HTS resuscitation has a greater impact on immune system recovery than NS or HES by preserving the proportion of Tregs and maintaining the balance between Th1/Th2 and Tc1/Tc2 cells in the spleen. Thus, HTS resuscitation provides potential immunomodulatory activity in the early stage after hemorrhagic shock.

Acute high-altitude exposure shortens survival after uncontrolled hemorrhagic shock in rats

BACKGROUND

Uncontrolled hemorrhage (UH) remains the most common cause of death on the battlefield. This study examined the pathophysiological characteristics of UH in rats acutely exposed to high altitude.

MATERIAL AND METHODS

Rats raised at sea level were randomly divided into two groups. Rats in the high-altitude group were exposed to hypobaric hypoxia in a hypobaric chamber (simulating 4000 m above sea level) for 2 d and then were performed a hemorrhagic shock protocol in the hypobaric chamber. Rats that underwent the same hemorrhage procedure at sea level were used as control. Anesthetized rats were bled to maintain their mean arterial pressure at 45 mmHg for 1 h. The distal quarter of the tail was amputated to allow free blood loss. After 1 h, the tail cut was ligated to induce hemostasis. mean arterial pressure, acid-base balance, blood loss, and survival were recorded. Rats were killed, and tissues were obtained for histological analysis.

RESULTS

Rats in the high-altitude group suffered less uncontrolled blood loss, more severe acidosis (lower pH and base excess), and inferior tissue oxygen supply (lower oxygen saturation and higher arterial lactate concentration) during the hemorrhage periods compared with the control group. Survival rates were significantly lower in the high-altitude group than those in the control group (P < 0.05), which was consistent with the results of pathological tissue injury.

CONCLUSIONS

In this rat model of hemorrhagic shock, acute high-altitude exposure resulted in decreased UH but more serious hemorrhagic shock injuries than that at sea level.

G-CSF Administration after the Intraosseous Infusion of Hypertonic Hydroxyethyl Starches Accelerating Wound Healing Combined with Hemorrhagic Shock

Objective. To evaluate the therapeutic effects of G-CSF administration after intraosseous (IO) resuscitation in hemorrhagic shock (HS) combined with cutaneous injury rats. Methods. The rats were randomly divided into four groups: (1) HS with resuscitation (blank), (2) HS with resuscitation + G-CSF (G-CSF, 200 μg/kg body weight, subcutaneous injection), (3) HS with resuscitation + normal saline solution injection (normal saline), and (4) HS + G-CSF injection without resuscitation (Unres/G-CSF). To estimate the treatment effects, the vital signs of alteration were first evaluated, and then wound closure rates and homing of MSCs and EPCs to the wound skins and vasculogenesis were measured. Besides, inflammation and vasculogenesis related mRNA expressions were also examined. Results. IO infusion hypertonic hydroxyethyl starch (HHES) exhibited beneficial volume expansion roles and G-CSF administration accelerated wound healing 3 days ahead of other groups under hemorrhagic shock. Circulating and the homing of MSCs and EPCs at wound skins were significantly elevated at 6 h after G-CSF treatment. Inflammation was declined since 3 d while angiogenesis was more obvious in G-CSF treated group on day 9. Conclusions. These results suggested that the synergistical application of HHES and G-CSF has life-saving effects and is beneficial for improving wound healing in HS combined with cutaneous injury rats.

Effects of different resuscitation fluids on pulmonary expression of aquaporin1 and aquaporin5 in a rat model of uncontrolled hemorrhagic shock and infection

BACKGROUND

To investigate the effects of fluids resuscitation on pulmonary expression of aquaporin1 and aquaporin5 in a rat model of uncontrolled hemorrhagic shock and infection.

METHODS

Sixty Sprague-Dawley rats were randomly assigned to five groups, sham operation group (Group C) and four treated groups: no fluid resuscitation group (Group NF), groups resuscitated with Lactated Ringer's (LR),7.5% NaCl (HTS) and Hydroxyl ethyl starch (HES) respectively. Three-phased uncontrolled hemorrhagic shock and infection model was used. Phase I: Massive hemorrhage with a mean arterial pressure of 35-40 mmHg for 60 min, and followed by infection of lipopolysaccharide. Then some animals were resuscitated with solutions mentioned above, until 90 min. Phase II: At hemorrhagic shock 90 minutes, phase II of 60 minutes began with hemostasis and returning of all the initial shed blood. Phase III: Observation phase for 3.5 hours. After phase III, arterial blood gas analysis and the survival rates of the rats were recorded, Wet-to-dry lung weight ratio, BALF protein, pulmonary permeability index, and expressions of aquaporin1 and aquaporin5 were tested.

RESULTS

The expressions of aquaporin1 and aquaporin5 were decreased in treatment groups comparing with sham operation group. Group HES and Group HTS decreased pulmonary vascular permeability and Wet-to-dry lung weight ratio, improved arterial blood gas analysis and survival rates, and attenuated the decreased pulmonary expression of aquaporin1 and aquaporin5 after the "two-hit", comparing with groups NF and LR,but these beneficial effects were blunted in group HTS.

CONCLUSION

The expression of aquaporin1 and aquaporin5 may play important roles in formation of pulmonary edema. Resuscitation with HTS and HES, especially HES can reduce lung injury after hemorrhagic shock, partly by up-regulating the expressions of aquaporin1 and aquaporin5.

The effectiveness of hypertonic saline and pentoxifylline (HTS-PTX) resuscitation in haemorrhagic shock and sepsis tissue injury: comparison with LR, HES, and LR-PTX treatments

PURPOSE

To compare lung and liver injury and laboratory results in haemorrhagic shock and sepsis models treated with combinations of lactated Ringer's solution (LR), 7.5% hypertonic saline (HTS), hydroxyethyl starch (HES), and pentoxifylline (PTX).

METHODS

Male Sprague-Dawley rats (200-290 g) were assigned randomly to one of four treatment groups (n=16 per group): (1) LR; (2) HES; (3) LR-PTX; and (4) HTS-PTX. Each group was subdivided into (1) haemorrhagic shock (n=8) and (2) sepsis (n=8) model groups. A venous catheter was used to inject resuscitation fluids, and an arterial catheter was used to withdraw blood and monitor mean arterial pressure (MAP). Lung and liver histology, bronchoalveolar lavage (BAL) fluid, and cytokine levels were evaluated.

RESULTS

The mean lung injury score was 1.7. At 24h after treatment, the total leucocyte count in the BAL fluid was significantly (p<0.05) higher with LR treatment (10 × 10(6) ± 0.8) than with other treatments in the sepsis model groups (HES, 6 × 10(6) ± 1.2; LR-PTX, 5 × 10(6) ± 1.5; HTS-PTX, 5 × 10(6) ± 0.6). The higher total leucocyte count after LR treatment was attributable to a greater increase in the number of neutrophils (17 ± 1.5%) compared with increases after the other treatments (HES, 6 ± 0.8%; LR-PTX, 10 ± 1.3%; HTS-PTX, 5 ± 0.4%). In the sepsis model groups, the total hepatic injury score was also significantly (p<0.05) higher with LR treatment (9.9 ± 0.5) than with the other treatments (HES, 6.7 ± 0.8; LR-PTX, 5.6 ± 0.7; HTS-PTX, 3.1 ± 0.9). This also occurred in the shock model (LR, 10.6 ± 2.1; HES, 5.8 ± 0.9; LR-PTX, 7.3 ± 0.9; HTS-PTX, 3.5 ± 0.9). As compared with LR treatment, HTS-PTX resuscitation resulted in a 49% decrease in TNF-α, 29% decrease in IL-1β, and 58% decrease in IL-6 in the shock model at 24h (p<0.05), and the respective decreases were 45, 24, and 35% in the sepsis model (p<0.05).

CONCLUSION

HTS-PTX was superior to HES, LR-PTX, and LR for treating shock and sepsis, and LR-PTX and HES gave better results than LR therapy alone.

Place of the colloids in fluid resuscitation of the traumatized patient

PURPOSE OF REVIEW

The examination of the recent literature aimed at analysing the most recent data that could affect decisions regarding the use of colloids in trauma resuscitation.

RECENT FINDINGS

Animal data have generally shown a beneficial effect of colloids in trauma resuscitation, with improvements in capillary leak demonstrated in lung, intestine and brain. In most studies, hydroxyethyl starch resuscitation was more effective than crystalloid and decreased markers of inflammatory processes were observed. Brain injury in animals was attenuated with colloids. In uncontrolled haemorrhage, resuscitation with colloid increased bleeding and mortality.Human studies have also failed to confirm the suggestion that albumin resuscitation may be associated with a worse outcome in head injury. However, there is a strong suggestion that aggressive prehospital resuscitation, particularly with colloid, may be harmful. Studies in burns have consistently shown an improvement in the tendency to fluid overload with the inclusion of colloid in the resuscitation strategy, but so far no outcome benefit has been shown.Two studies of general trauma resuscitation have shown apparent benefit from the use of HES in early resuscitation with reductions in mortality and in renal injury.

SUMMARY

Recent trauma studies provide ongoing, but not conclusive, evidence of a benefit from colloid resuscitation in trauma.

Fixed volume or fixed pressure: a murine model of hemorrhagic shock

It is common knowledge that severe blood loss and traumatic injury can lead to a cascade of detrimental signaling events often resulting in mortality. ^{1, 2, 3, 4, 5} These signaling events can also lead to sepsis and/or multiple organ dysfunction (MOD). ^{6, 7, 8, 9} It is critical then to investigate the causes of suppressed immune function and detrimental signaling cascades in order to develop more effective ways to help patients who suffer from traumatic injuries. ¹⁰ This fixed pressure Hemorrhagic Shock (HS) procedure, although technically challenging, is an excellent resource for investigation of these pathophysiologic conditions. ^{11, 12, 13} Advances in the assessment of biological systems, i.e. Systems Biology have enabled the scientific community to further understand complex physiologic networks and cellular communication patterns. ¹⁴ Hemorrhagic Shock has proven to be a vital tool for unveiling these cellular communication patterns as they relate to immune function. ^{15, 16, 17, 18} This procedure can be mastered! This procedure can also be used as either a fixed volume or fixed pressure approach. We adapted this technique in the murine model to enhance research in innate and adaptive immune function. ^{19, 20, 21} Due to their small size HS in mice presents unique challenges. However due to the many available mouse strains, this species represents an unparalleled resource for the study of the biologic responses. The HS model is an important model for studying cellular communication patterns and the responses of systems such as hormonal and inflammatory mediator systems, and danger signals, i.e. DAMP and PAMP upregulation as it elicits distinct responses that differ from other forms of shock. ^{22, 23, 24, 25} The development of transgenic murine strains and the induction of biologic agents to inhibit specific signaling have presented valuable opportunities to further elucidate our understanding of the up and down regulation of signal transduction after severe blood loss, i.e. HS and trauma ^{26, 27, 28, 29, 30}.

There are numerous resuscitation methods (R) in association with HS and trauma. ^{31, 32, 33, 34} A fixed volume resuscitation method of solely lactated ringer solution (LR), equal to three times the shed blood volume, is used in this model to study endogenous mechanisms such as remote organ injury and systemic inflammation. ^{35, 36, 38} This method of resuscitation is proven to be effective in evaluating the effects of HS and trauma ^{38, 39}.