PentaLyte decreases lung injury after aortic occlusion-reperfusion

Comparison of Hb-200 and 6% hetastarch 450/0.7 during initial fluid resuscitation of 20 dogs with gastric dilatation-volvulus

OBJECTIVE

To compare the use of polymerized stroma-free bovine hemoglobin (Hb-200) and 6% hetastarch 450/0.7 (HES 450/0.7) in 0.9% saline during fluid resuscitation of dogs with gastric dilatation-volvulus (GDV).

DESIGN

Prospective, randomized clinical case series.

SETTING

Private specialty and referral clinic.

ANIMALS

Twenty client-owned dogs presenting with GDV.

INTERVENTIONS

Dogs presenting with GDV and abnormal perfusion parameters first received rapid IV infusion of a buffered isotonic replacement crystalloid (15 mL/kg) and IV opioids. Patients were then randomized to receive either Hb-200 (N = 10) or HES 450/0.7 (N = 10). Balanced isotonic replacement crystalloids (10-20 mL/kg IV) were rapidly infused along with either Hb-200 or HES in 5 mL/kg IV aliquots to meet resuscitation end points.

MEASUREMENTS AND MAIN RESULTS

Resuscitation was defined as meeting at least 2 of 3 criteria: (1) capillary refill time 1-2 seconds, pink mucous membrane color, strong femoral pulse quality; (2) heart rate (HR) ≤ 150/min; or (3) indirect arterial systolic blood pressure (SBP) > 90 mm Hg. HR, SBP, packed cell volume, hemoglobin, glucose, venous pH, bicarbonate, base excess, anion gap, and colloid osmotic pressure were compared at hospital entry and within 30 minutes post-resuscitation. Compared to the HES group, the Hb-200 group required significantly less colloid (4.2 versus 18.4 mL/kg) and crystalloid (31.3 versus 48.1 mL/kg) to reach resuscitation end points (P = 0.001). Time to resuscitation was significantly shorter in the Hb-200 group (12.5 versus 52.5 min).

CONCLUSIONS

Dogs with GDV receiving Hb-200 during initial resuscitation required smaller volumes of both crystalloid and colloid fluids and reached resuscitation end points faster than dogs receiving HES 450/0.7 (P = 0.02).

Lung ischemia-reperfusion injury: a molecular and clinical view on a complex pathophysiological process

Lung ischemia-reperfusion injury remains one of the major complications after cardiac bypass surgery and lung transplantation. Due to its dual blood supply system and the availability of oxygen from alveolar ventilation, the pathogenetic mechanisms of ischemia-reperfusion injury in the lungs are more complicated than in other organs, where loss of blood flow automatically leads to hypoxia. In this review, an extensive overview is given of the molecular and cellular mechanisms that are involved in the pathogenesis of lung ischemia-reperfusion injury and the possible therapeutic strategies to reduce or prevent it. In addition, the roles of neutrophils, alveolar macrophages, cytokines, and chemokines, as well as the alterations in the cell-death related pathways, are described in detail.

Combined therapy of pentastarch, dexamethasone, and dibutyryl-cAMP or beta 2-agonist attenuates ischaemia/reperfusion injury of rat lung

We hypothesised that combined therapy with macromolecules that seal endothelial damage [pentastarch (Penta)], an anti-inflammatory agent [dexamethasone (Dex)], and an agent that reabsorbs alveolar fluid [beta(2)-agonist or dibutyryl-cAMP (Bt(2)-cAMP)] would have additive ameliorating effects on ischaemia/reperfusion (I/R) injury of the lung. We perfused one of the following solutions into isolated rat lungs in a closed circulating system, either prior to I/R injury (groups 1-5) or following 60 min of ischaemia (groups 6-10): (1) 0.9% normal saline (NS), (2) Penta, (3) Penta+Dex, (4) Penta+Bt(2)-cAMP, (5) Penta+beta(2)-agonist inhalation, (6) Penta+Dex, (7) Penta+Bt(2)-cAMP, (8) Penta+beta(2)-agonist inhalation, (9) Penta+Dex+Bt(2)-cAMP, or (10) Penta+Dex+beta(2)-agonist inhalation. Haemodynamics, lung weight gain (LWG), capillary filtration coefficient (K(fc)), cytokine mRNA levels, and lung pathology were assessed. Results showed that Dex, Bt(2)-cAMP, or beta(2)-agonist as an additive to Penta decreased K(fc) and LWG below values seen with Penta alone. Furthermore, LWG and K(fc) values in groups with three protective agents were lower than those in groups with two protective agents. Significantly lower levels of TNF-alpha and IL-1 mRNAs were observed in groups treated with Dex. Histopathological studies showed decreased injury profiles for all combined therapy groups. We conclude that the addition of Dex, Bt(2)-cAMP, or beta(2)-adrenergic agonist to Penta solution promoted attenuation of I/R injury. Furthermore, combination therapy with three protective agents (Penta+Dex+beta(2)-adrenergic agonist) caused the greatest attenuation of I/R.

Animal models of acute lung injury

Acute lung injury in humans is characterized histopathologically by neutrophilic alveolitis, injury of the alveolar epithelium and endothelium, hyaline membrane formation, and microvascular thrombi. Different animal models of experimental lung injury have been used to investigate mechanisms of lung injury. Most are based on reproducing in animals known risk factors for ARDS, such as sepsis, lipid embolism secondary to bone fracture, acid aspiration, ischemia-reperfusion of pulmonary or distal vascular beds, and other clinical risks. However, none of these models fully reproduces the features of human lung injury. The goal of this review is to summarize the strengths and weaknesses of existing models of lung injury. We review the specific features of human ARDS that should be modeled in experimental lung injury and then discuss specific characteristics of animal species that may affect the pulmonary host response to noxious stimuli. We emphasize those models of lung injury that are based on reproducing risk factors for human ARDS in animals and discuss the advantages and disadvantages of each model and the extent to which each model reproduces human ARDS. The present review will help guide investigators in the design and interpretation of animal studies of acute lung injury.

d-Lactate is not a reliable marker of gut ischemia–reperfusion in a rat model of supraceliac aortic clamping*

OBJECTIVE

D-lactate is the dextrorotatory form of L-lactate. L-lactate is the isomer routinely tested in clinical practice to assess cell hypoxemia. D-lactate has been recently proposed as a specific marker of gut ischemia-reperfusion (IR), particularly after surgery for ruptured aortic aneurysms. We sought to assess D-lactate as a reliable marker of gut IR in a rat model of supraceliac aortic clamping.

DESIGN

Prospective, randomized trial.

SETTING

Animal research center.

SUBJECTS

Male Wistar rats.

INTERVENTIONS

After general anesthesia, rats were randomized into two groups (n = 8 in each). The IR group underwent a laparotomy, aortic clamping for 40 mins, and 1 hr of reperfusion. The control group underwent the same procedure, except for aortic clamping.

MEASUREMENTS AND MAIN RESULTS

The following variables were tested after 1 hr of reperfusion (IR group) or after the equivalent time (control group): 1) tissue and cell insult via ileum morphometry and electron microscopy, serum glutamic transaminases (serum glutamic-oxaloacetic transaminase and serum glutamic-pyruvic transaminase), pH, and L-lactate; 2) systemic inflammatory response via tumor necrosis factor-alpha; and 3) D-lactate levels. After IR, mucous membrane thickness and villi height decreased significantly, respectively by 30% and 45%, and electron-microscopic examination showed typical IR mucous membrane cell insult. IR also caused lactic acidosis (pH = 7.16 +/- 0.05 vs. 7.31 +/- 0.02, p < .01; L-lactate = 7.1 +/- 1.6 vs. 1.6 +/- 0.4 mmol/L, p = .001) and increased blood levels of transaminases. Concurrently, the inflammatory response was characterized by an increase in tumor necrosis factor-alpha (213 +/- 129 vs. 47 +/- 32 pg/mL, p < .05). However, blood levels of D-lactate never increased after IR.

CONCLUSIONS

D-lactate is not a reliable marker of gut IR in our model of supraceliac aortic clamping in rats.

DO PLASMA SUBSTITUTES HAVE ADDITIONAL PROPERTIES BEYOND CORRECTING VOLUME DEFICITS?

The best strategy for volume therapy has been the focus of debate and there are still no unique accepted guidelines. There is increasing evidence that some plasma substitutes possess additional effects on organ perfusion, microcirculation, tissue oxygenation, inflammation, endothelial activation, capillary leakage, and tissue edema that are beyond their volume replacing properties. Whether the different plasma substitutes differ with regard this additional effects was reviewed. The additional effects of plasma substitutes have mostly been studied experimentally or in animals, much less results are available in humans. The results are not uniform ranging from beneficial to even detrimental effects of a certain volume replacement strategy. Some important results from the literature are not reflected in the actual recommendations for treating volume deficits in the critically ill: although crystalloids have been shown to have considerable negative effects on microcirculation, organ perfusion, tissue oxygenation, and endothelial integrity, they are still often recommended as first choice volume replacement strategy. In several experimental studies hypertonic solutions have been shown to have various beneficial effects, they have not been, however, translated into humans. In future, the choice of the ideal volume replacement regimen should not only be focused on its volume restoring properties, but additional effects (e.g. on organ perfusion on, tissue oxygenation, inflammation, endothelial activation, capillary leakage) should also be taken into account when treating hypovolemia in the critically ill.

Effect of fluid loading with saline or colloids on pulmonary permeability, oedema and lung injury score after cardiac and major vascular surgery

BACKGROUND

The optimal type of fluid for treating hypovolaemia without evoking pulmonary oedema is still unclear, particularly in the presence of pulmonary vascular injury, as may occur after cardiac and major vascular surgery.

METHODS

In a single-centre, prospective, single-blinded clinical trial 67 mechanically ventilated patients were randomly assigned to receive saline, gelatin 4%, HES 6% or albumin 5%, according to a 90 min fluid loading protocol with target central venous pressure of 13 and pulmonary capillary wedge pressure of 15 mm Hg, within 3 h after cardiac or major vascular surgery. Before and after the protocol, we recorded haemodynamics and ventilatory variables and took chest radiographs. The pulmonary vascular injury was evaluated using the 67Ga-transferrin pulmonary leak index (PLI) and extravascular lung water (EVLW). Plasma colloid osmotic pressure (COP) was determined and the lung injury score (LIS) was calculated.

RESULTS

More saline was infused than colloid solutions (P<0.005). The COP increased in the colloid groups and decreased in patients receiving saline. Cardiac output increased more in the colloid groups. At baseline, PLI and EVLW were above normal in 60 and 30% of the patients, with no changes after fluid loading, except for a greater PLI decrease in HES than in gelatin-loaded patients. The oxygenation ratio improved in all groups. In the colloid groups, the LIS increased, because of a decrease in total respiratory compliance, probably associated with an increase in intrathoracic plasma volume.

CONCLUSIONS

Provided that fluid overloading is prevented, the type of fluid used for volume loading does not affect pulmonary permeability and oedema, in patients with acute lung injury after cardiac or major vascular surgery, except for HES that may ameliorate increased permeability. During fluid loading, changes in LIS (and respiratory compliance) do not represent changes in pulmonary permeability or oedema.

Lung injury after aortic occlusion-reperfusion in rats: the role of gadolinium chloride

Aortic ischemia-reperfusion (AIR) induced lung injury has already been documented. Kupffer cell blockage (KCB) with gadolinium chloride (GdCl3) has also been shown to attenuate remote organ damage caused by ischemia reperfusion. The present study was designed to examine the effect of GdCl3 in lung ischemia-reperfusion injury induced by aortic occlusion. Thirty-two rats were randomly allocated to four groups as follows: SHAM (Sham Laparotomy), SHAM+KCB, AIR, and AIR+KCB. An atraumatic microvascular clamp was placed across the infrarenal abdominal aorta just after its origin from the aorta for 30 minutes. The microvascular clamp on the infrarenal abdominal aorta was removed and reperfused for 60 minutes. GdCl3 was given 24 hours prior to the experiment. Malondialdehyde (MDA) level and myeloperoxidase (MPO) activity were assayed in lung tissues. MDA level and MPO activity in the AIR group were significantly higher than those in the other groups. When compared to AIR group, KCB with GdCl3 significantly decreased MDA level and MPO activity in the AIR+KCB group. These results suggest that GdCl3 attenuates the lung injury caused by AIR. The effects of GdCl3 on reduced lung damage may be mediated through significant decreases in both MDA level and MPO activity.

Pulmonary responses of acute exposure to ultrafine iron particles in healthy adult rats

As critical constituents of ambient particulate matter, transition metals such as iron may play an important role in health outcomes associated with air pollution. The purpose of this study was to determine the respiratory effects of inhaled ultrafine iron particles in rats. Sprague Dawley rats 10-12 weeks of age were exposed by inhalation to iron particles (57 and 90 microg/m(3), respectively) or filtered air (FA) for 6 h/day for 3 days. The median diameter of particles generated was 72 nm. Exposure to iron particles at a concentration of 90 microg/m(3) resulted in a significant decrease in total antioxidant power along with a significant induction in ferritin expression, GST activity, and IL-1beta levels in lungs compared with lungs of the FA control or of animals exposed to iron particles at 57 microg/m(3). NFkappaB-DNA binding activity was elevated 1.3-fold compared with that of control animals following exposure to 90 microg/m(3) of iron, but this change was not statistically significant. We concluded that inhalation of iron particles leads to oxidative stress associated with a proinflammatory response in a dose-dependent manner. The activation of NFkappaB may be involved in iron-induced respiratory responses, but further studies are merited.

Resuscitation with Hextend decreases endogenous circulating heparin activity and accelerates clot initiation after hemorrhage in the rabbit

Hemorrhagic shock can result in a hypercoagulable state and has been associated with both hemorrhagic and thrombotic complications in the perioperative period. The author hypothesized that hemorrhage and resuscitation could result in a hypercoagulable state via changes in the heparin-antithrombin III anticoagulant mechanism in rabbits. Rabbits sedated with ketamine underwent sham operation (n = 8) or hemorrhage (25 mL/kg blood shed) for 60 min, followed by resuscitation with an equal volume of 5% human albumin (n = 8) or Hextend (n = 8). Coagulation analysis with the Thrombelastograph analyzer and determination of endogenous heparin and antithrombin III activity were performed on arterial blood samples obtained before hemorrhage and 30 min after resuscitation. The reaction time significantly decreased by 34% after hemorrhage and resuscitation with Hextend, whereas no other significant changes in Thrombelastograph variables were noted. Antithrombin III activity was significantly less in the Albumin (83% +/- 8% of control, mean +/- SD) and Hextend (88% +/- 8%) Resuscitated groups compared with the Sham-Operated animals. Of interest, only the Hextend-Resuscitated animals demonstrated a significant decrease in heparin activity (53.4 +/- 13.6 mU/mL before hemorrhage, 42.3 +/- 5.6 mU/mL after resuscitation). A Hextend)-mediated decrease of both heparin and antithrombin III activity may explain the acceleration of clot initiation compared with albumin administration after hemorrhage in the rabbit.

IMPLICATIONS

Hemorrhage may result in a hypercoagulable state after resuscitation. Decreases in both endogenous heparin and antithrombin III activity after hemorrhage and Hextend resuscitation in rabbits resulted in a significantly decreased time to clot coagulation analysis initiation without a significant change in the rate of clot formation or final clot strength.

Pentalyte does not decrease heparinoid release but does decrease circulating thrombotic mediator activity associated with aortic occlusion-reperfusion in rabbits

Hemorrhage and thrombosis are associated with major vascular and trauma surgery. Release of heparinoids and thrombotic mediators may contribute to these complications and have been described in rabbits after aortic occlusion-reperfusion. We hypothesized that the resuscitative fluid used could reduce heparinoid and thrombotic mediator release after aortic occlusion-reperfusion in rabbits as assessed by thromboelastographic variables (R, reaction time; alpha, angle; and G, a measure of clot strength). Anesthetized rabbits were administered lactated Ringer's solution (n = 8) or PentaLyte (n = 8) at reperfusion after 30 min of ischemia. Blood was obtained before ischemia and after 30 min of reperfusion for thromboelastography under four conditions: 1) unmodified sample, 2) platelet inhibition, 3) heparinase, and 4) platelet inhibition and heparinase. During reperfusion, unmodified samples demonstrated a significant increase in R and decrease in alpha and G that was not affected by PentaLyte. In the presence of heparinase, no significant fluid-specific thromboelastographic differences were noted. However, thrombotic mediator release (discerned by a decrease in R and an increase in alpha) during reperfusion in samples with platelet inhibition and heparinase was significantly attenuated by PentaLyte. PentaLyte administration does not decrease heparinoid release but does decrease thrombotic mediator release after aortic occlusion-reperfusion.

Hepatoenteric ischemia-reperfusion increases circulating heparinoid activity in rabbits

PURPOSE

The purpose of this study was to determine if an increase in circulating heparinoid activity contributes to the hemostatic abnormalities associated with hepatoenteric ischemia-reperfusion.

MATERIALS AND METHODS

Anesthetized rabbit (n = 18) underwent thoracic aorta occlusion for 30 minutes with a balloon catheter, followed by 30 minutes of reperfusion. Blood samples were obtained after 30 minutes of equilibration and 30 minutes of reperfusion. Hemostatic function was assessed by changes in the thrombelastographic variables R (reaction time), alpha (a measure of the speed of clot formation), and G (a measure of clot strength). Thrombelastography was performed on blood without platelet inhibition in the presence or absence of heparinase (n = 9 rabbits). Additional samples (n = 9) were exposed to cytochalasin D (platelet inhibitor) with or without heparinase.

RESULTS

Compared with preischemic values, blood samples with intact platelet function obtained during reperfusion demonstrated a decrease in hemostatic function evidenced by a significant (P<.05) increase in R, decrease in alpha, and decrease in G. R, alpha, and G values of samples without platelet inhibition exposed to heparinase did not significantly change after ischemia. Blood samples exposed to cytochalasin D displayed a similar pattern.

CONCLUSION

An increase in circulating heparinoid activity significantly contributes to the hemostatic disorder associated with hepatoenteric ischemia-reperfusion in rabbits.