Comparing High-Frequency With Monophasic Electroporation Protocols in an In Vivo Beating Heart Model

This study compared monophasic 100-μs pulses with high-frequency electroporation (HF-EP) bursts using an in vivo animal model. Myocardial damage was evaluated by histologic analysis. Compared with 10 monophasic pulses, 20 bursts of HF-EP at 100 and 150 kHz were associated with less damage. However, when the number of HF-EP bursts was increased to 60, myocardial damage was comparable to that of the monophasic group. HF-EP protocols were associated with attenuated collateral muscle contractions. This study shows that HF-EP is feasible and effective and that pulse frequency has a significant effect on extent of ablation.

Pulmonary TNFα is a critical mediator in Adult Respiratory Distress Syndrome

The development of effective pharmacotherapies to combat the Adult Respiratory Distress Syndrome (ARDS) is critically dependent upon: (1) the development of clinically-relevant animal models; (2) identification of inflammatory mediators centrally involved in eliciting lung injury; (3) understanding the inter-relationships or 'cross-talk' between pro and anti-inflammatory mediators which modulate the lung inflammation; and (4) the application of molecular techniques to isolate potentially novel genes involved in the development of ARDS. In this paper, we will present evidence from a rat model of microvascular lung injury produced by interleukin-2 (IL-2), that pulmonary TNFα is a primary and pivotal mediator of lung injury and that different modes of TNFα inhibition may represent feasible strategies to prevent ARDS. Furthermore, we will describe how the application of Differential Display Reverse Transcriptase Polymerase Chain Reaction (DDRT-PCR) can allow the rapid isolation of partial fragments of potentially new genes involved in ARDS. The products of such genes could represent future target sites for pharmacotherapeutic intervention.

Sixty-Seven Consecutive Resuscitative Thoracotomies by A Single Surgeon

Background:

Resuscitative thoracotomy is a dramatic operation performed in otherwise unsalvageable trauma patients. Analysis of its efficacy is based mostly on institutional series compiling the experience of multiple surgeons. This study aimed to report more consistent information by describing the resuscitative thoracotomy practice of a single surgeon and its evolution during more than two decades.

Methods:

A retrospective review of consecutive patients who underwent resuscitative thoracotomy in July 1990 to December 2012. Demographics, mechanism of injury, signs of life, injuries, and outcomes were analyzed. Comparisons were made between penetrating and blunt trauma patients and between pre- and post-introduction of a selective resuscitative thoracotomy protocol.

Results:

Sixty-seven resuscitative thoracotomies were performed. Most patients were males (84%), and mean age was 38 years. Mechanism of injury was stab wounds (54%, 36), blunt force (25%, 17), and gunshot wounds (21%, 14). Survival was 22% (8/36), 0% (0/17), and 7% (1/14), respectively. All nine survivors had signs of life upon admission, and survival in patients with signs of life on admission was 25% (8/32) in the stab wounds group and 8% (1/12) in the gunshot wounds group. Seven of the nine survivors (78%) were discharged neurologically intact. The most common injury in survivors was cardiac laceration with tamponade (6/9) and lung injury (3/9). Three survivors had a cardiac and lung injury, one had a lung hilum injury, and one had an abdominal inferior vena cava laceration. The switch to resuscitative thoracotomy protocol (2002) improved overall (31 vs 8%, p < 0.05) and penetrating trauma (45 vs 10%, p < 0.05) survival, eliminated resuscitative thoracotomy in patients presenting with no signs of life, and tended to reduce resuscitative thoracotomy utilization in blunt trauma patients.

Conclusion:

This single-surgeon series supports that resuscitative thoracotomy can be lifesaving in selected penetrating trauma patients in extremis. A switch to a selective evidence-based protocol increased overall and penetrating resuscitative thoracotomy survival and limited resuscitative thoracotomy performance to patients arriving with signs of life.

Resuscitative Thoracotomy: An Update

BACKGROUND

Resuscitative thoracotomy is a heroic procedure that may offer the only survival hope for trauma patients in extremis. However, this operation has been the subject of much debate and its use, feasibility, outcomes, and cost are being continuously re-evaluated.

METHODS

This is a review of the most current (after 2000) literature on resuscitative thoracotomy, based on computer database searches for studies on resuscitative thoracotomy, emergency department thoracotomy, and emergency thoracotomy. Studies were selected for inclusion in this review based on their relevance and contribution to our understanding of resuscitative thoracotomy.

RESULTS

A total of 37 studies were included, and the following resuscitative thoracotomy-related topics were critically discussed: indications, biochemical profile, long-term outcome, organ donation, pre-hospital use, military use, international aspects, intra-aortic balloon occlusion, suspended animation, and cost and occupational exposure.

CONCLUSIONS

This review demonstrates that the indications for resuscitative thoracotomy become clearer and that new information is available regarding its use in the pre-hospital urban environment and military settings. Furthermore, it points to new strategies to supplement resuscitative thoracotomy including intra-aortic balloon occlusion and suspended animation. Finally, it sheds light on the long-term outcomes, organ donation, and cost and occupational exposure following resuscitative thoracotomy.

The status of hemoglobin-based red cell substitutes

Red cell substitutes are currently under development for use in a variety of surgery and trauma-related clinical conditions. The need for artificial oxygen-carrying fluids continues to be driven by the shortage of donor blood, the complex logistics of blood banking, the risk of virally transmitted diseases, current transfusion practices, and the projected increased demand for blood products in the future. The effort to develop a replacement for the red cell component has evolved over the last century and has presented a number of significant challenges including safety and efficacy concerns. Recent progress in understanding the fundamental interactions of hemoglobin with the body at the molecular, cellular and tissue levels has led to the production of improved red cell substitutes suitable for clinical testing. Currently, seven products are being tested for a variety of applications including trauma, surgery, sepsis, cancer and anemia. Although some of these trials were unsuccessful, the majority of the available products exert no toxicity or only low level side effects. Encouraging results in early clinical trials with oxygen-carrying fluids support further development of these products and have increased the hope that a usable oxygen-carrying fluid will soon be available in the clinic. The purpose of this review is to provide up-to-date information on the status of these products with special emphasis on pre-clinical and clinical experience.

ADAR1 Is Involved in the Development of Microvascular Lung Injury

Abstract —Deamination of adenosine on pre-mRNA to inosine is a recently discovered process of posttranscription modification of pre-mRNA, termed A-to-I RNA editing, which results in the production of proteins not inherent in the genome. The present study aimed to identify a role for A-to-I RNA editing in the development of microvascular lung injury. To that end, the pulmonary expression and activity of the RNA editase ADAR1 were evaluated in a mouse model of endotoxin (15 mg/kg IP)–induced microvascular lung injury (n=5) as well as in cultured alveolar macrophages stimulated with endotoxin, live bacteria, or interferon. ADAR1 expression and activity were identified in sham lungs that were upregulated in lungs from endotoxin-treated mice (at 2 hours). Expression was localized to polymorphonuclear and monocytic cells. These events preceded the development of pulmonary edema and leukocyte accumulation in lung tissue and followed the local production of interferon-γ, a known inducer of ADAR1 in other cell systems. ADAR1 was found to be upregulated in alveolar macrophages (MH-S cells) stimulated with endotoxin (1 to 100 μg/mL), live Escherichia coli (5×10 7 colony-forming units), or interferon-γ (1000 U/mL). Taken together, these data suggest that ADAR1 may play a role in the pathogenesis of microvascular lung injury possibly through induction by interferon.

Chest tube removal: end-inspiration or end-expiration?

BACKGROUND

Recurrent pneumothorax is the most significant complication after discontinuation of thoracostomy tubes. The primary objective of the present study was to determine which method of tube removal, at the end of inspiration or at the end of expiration, is associated with a lesser risk of developing a recurrent pneumothorax. A secondary objective was to identify potential risk factors for developing recurrence.

METHODS

A prospective study of 102 chest tubes in 69 trauma patients (1.5 tubes per patient) randomly assigned to removal at the end of inspiration (n = 52) or the end of expiration (n = 50).

RESULTS

Recurrent pneumothorax or enlargement of a small but stable pneumothorax was observed after the removal of four chest tubes in the end-inspiration group (8%) and after discontinuation of three chest tubes (6%) in the end-expiration group (p = 1.0). Of those, only two tubes in the end-inspiration group and 1 tube in the end-expiration group required repeat closed thoracostomy. Multiple factors were analyzed that did not adversely affect outcome. These included patient age, Injury Severity Score, Revised Trauma Score, mechanism of injury, hemothorax, thoracotomy, thoracostomy, previous lung disease, chest tube duration, the presence of more than one thoracostomy tube in the same hemithorax, or a small (but stable) pneumothorax at the time of tube removal.

CONCLUSIONS

Discontinuation of chest tubes at the end of inspiration or at the end of expiration has a similar rate of post-removal pneumothorax. Both methods are equally safe.

Trovafloxacin-associated leukopenia

OBJECTIVE

To report a case of trovafloxacin-associated leukopenia, which occurred in a trauma patient shortly after administration and resolved following discontinuation of the drug.

CASE SUMMARY

A 79-year-old white man was admitted to Yale New Haven Hospital after sustaining partial amputation of his right lower leg by an industrial lawn mower. After successful resuscitation, he underwent complete right lower amputation and was treated with intravenous alatrofloxacin mesylate. He developed leukopenia that resolved after discontinuation of the drug.

DISCUSSION

Trovafloxacin is a broad-spectrum synthetic fluoroquinolone used for a wide variety of bacterial infections. We report, for the first time in the English-language literature, a case of trovafloxacin-associated leukopenia. The leukopenia resolved promptly after discontinuation of the drug. This association is further supported by the exclusion of other potential causes for this adverse effect.

CONCLUSIONS

Leukopenia is a well-recognized adverse effect of several drugs. We report a case of trovafloxacin-associated leukopenia during treatment of a trauma patient. Healthcare personnel should be aware of this possible adverse reaction in patients treated with trovafloxacin.

Liposome-encapsulated hemoglobin does not exacerbate endotoxin-induced lung injury

OBJECTIVE

To test the hypothesis that liposome encapsulated hemoglobin (LEH), an experimental oxygen-carrying fluid, exacerbates endotoxin-induced lung injury in the rat.

DESIGN

Prospective, randomized animal study.

SETTING

University animal laboratory.

METHODS

Anesthetized Sprague-Dawley rats (n = 8-13) were infused with LEH (10% of estimated total blood volume) or vehicle (0.9% NaCl). Thirty minutes later, Escherichia coli endotoxin (3.6 mg/kg, i.v.) or vehicle (0.9% NaCl) was administered, and skeletal muscle oxygen tension as well as lung injury were assessed at 2, 4, and 8 hrs. Oxygen tension was measured using a miniaturized thin film oxygen sensor placed in the rectus abdominis muscle, and lung injury was evaluated by determining lung weights, lung myeloperoxidase activity, lung tissue tumor necrosis factor-alpha level, and protein concentration in bronchoalveolar lavage fluid.

RESULTS

The intravenous bolus injection of E. coli endotoxin elevated lung water content (33% +/- 5%; p < .01 vs. sham controls), myeloperoxidase activity (56% +/- 6%; p < .01), and tumor necrosis factor-alpha production (1320 +/- 154 pg/g lung tissue; p < .05 vs. undetected levels in sham controls), as well as induced protein accumulation in bronchoalveolar lavage fluid (258% +/- 38%; p < .01) and skeletal muscle hypoxia (52 +/- 8 mm Hg; p < .05). Pretreatment with LEH, which when infused alone did not induce lung injury, had no effect on these responses.

CONCLUSION

In this specific model of endotoxin-induced lung injury, LEH does not exacerbate microvascular leakage and leukosequestration, the hallmarks of adult respiratory distress syndrome.

An improved clinically relevant sepsis model in the conscious rat

OBJECTIVE

To develop an improved small animal experimental paradigm that more closely mimics human sepsis.

DESIGN

Prospective, randomized, controlled animal study.

SETTING

Medical school research laboratory.

SUBJECTS

Male Sprague-Dawley rats (280-320 g).

INTERVENTIONS

We monitored the hemodynamic, hematologic, and biochemical consequences of abdominal sepsis produced by intraperitoneal implantation of a fibrin clot containing Escherichia coli in conscious, antibiotic-treated, rats.

MEASUREMENTS AND MAIN RESULTS

Similar to human sepsis, the implanted, infected clot (LD50 = 5-7 x 10(8) colony forming units/mL, n = 6) elevated cardiac index (>7% vs. sterile clot, p < .05, at 4 hrs), whereas mean arterial pressure and heart rate remained unaffected. The total peripheral resistance index and stroke volume index tended to decrease and increase, respectively. In contrast, an intravenous bolus injection of endotoxin (LD50 of E. coli lipopolysaccharide = 5.6 mg/kg, n = 7), the most commonly used sepsis model, induced profound hypodynamic responses manifested by a 27% decrease (vs. endotoxin vehicle, p < .01) in cardiac index, a 28% increase in the total peripheral resistance index (p < .01), and a 33% decrease in the stroke volume index (P < .01). The infectious peritonitis model also displayed dose-dependent thrombocytopenia (<61%, p < .05), leukopenia (<60%, p < .05), and mortality rate (50% at 5-7 x 10(8) colony forming units/mL, p < .05) with a minimally elevated serum tumor necrosis factor-alpha level (145 vs. 12 +/- 6 pg/mL in controls, p < .05).

CONCLUSION

This rodent model of antibiotic-treated, intra-abdominal infection features key characteristics of clinical sepsis. Although the hyperdynamic response observed in septic patients undergoing resuscitation was not clearly elicited, this paradigm better mimics clinical sepsis compared with the commonly used endotoxin model. Thus, utilization of this paradigm may provide additional opportunities to explore mechanisms of sepsis and to examine novel therapeutics.

Admission patterns of an urban level I trauma center

Because trauma admission and hospitalization patterns have profound effects on the organization and utilization of urban trauma-care systems, the objective of this study was to identify and analyze these patterns. As an example, admissions to an urban Level I trauma center were reviewed. Retrospective review of all 2029 trauma admissions to a Level I trauma center was conducted from 1993 to 1996. The result was that most trauma patients were young (40% < 30 years of age) and male (74%). Mechanisms of injury were motor vehicle accident (36%), fall (27%), gunshot (17%), stab (7%), assault (6%), and swimming or diving accident (3%). Half of the patients were directly admitted from the scene. Injury Severity Score, length of stay, and mortality were 14.1 +/- 0.3, 10.5 +/- 0.3 days, and 5.1%, respectively. Admissions tended to occur more frequently between 4:00 PM and midnight (46%), between Friday and Sunday (52%), and between July and October (41%). The following patterns were identified: admissions per year decreased (-21%) because of reduced penetrating trauma (-43%, P < .01); pediatric patients (< 15 years) had similar incidence of penetrating trauma as adults (ages 15-45). Length of stay for all mechanisms of injury was not statistically different; most mortalities occurred within the first day (33%, P < .01) or after 6 days (36%, P < .01); early mortality was mainly due to penetrating injury (74%, P < .01), whereas late mortality was related to blunt trauma (92%, P < .01). The conclusion was that admission and demographic patterns were identified, which may be useful in the utilization, modification, and future design of trauma systems.

Abdominal injuries associated with lumbar spine fractures in blunt trauma

BACKGROUND

Specific analysis of the relationship between abdominal injuries and lumbar spine fractures has not yet been reported.

METHODS

A retrospective review of 258 blunt trauma patients with lumbar spine fractures treated between 1991 and 1996.

RESULTS

26 patients sustained concomitant lumbar spine fractures and abdominal injuries. The mechanism of injury was motor vehicle collision (73%), pedestrian-struck (11%), fall (8%) and assault (8%) resulting in ISS, RTS and mortality of 27 +/- 4, 6.5 +/- 0.4 and 8%, respectively. Forty-four lumbar spine fractures were identified (1.7/pt) in association with splenic (54%), renal (41%), hepatic (32%) and small bowel (23%) injuries and no retroperitoneal involvement. Multilevel lumbar spine fractures were associated with a higher organ injury/fracture ratio compared with single level fractures (p < 0.01) including a twofold higher incidence of solid organ (spleen, liver and kidney) injury (p < 0.01). The level and type of fracture did not affect the incidence of total and individual organ injury. Patients with abdominal injuries were more severely injured mainly due to increased incidence of associated thoracic injuries although no significant difference in mortality was observed.

CONCLUSION

Abdominal injuries occurred only in the minority of blunt trauma patients with lumbar spine fractures. These injuries, which followed a similar distribution pattern as in blunt trauma in general, occurred most commonly due to motor vehicle collisions and in association with multilevel vertebral fractures. No correlation with fracture type or level was identified.

Effect of liposome-encapsulated hemoglobin on the development of endotoxin-induced shock in the rat

Liposome-encapsulated hemoglobin (LEH) is an experimental oxygen-carrying resuscitation fluid. Because LEH is cleared from the circulation primarily by the reticuloendothelial system, its effect on the development of sepsis remains a major concern. Thus, the present study aimed to evaluate whether LEH modifies consequences of endotoxemia in the conscious normovolemic rat. LEH infusion at 10% of estimated blood volume (n = 10) did not affect mortality (30%, p < .05) and serum tumor necrosis factor-alpha levels (6204 +/- 414, p < .05) induced by 3.6 mg/kg Escherichia coli endotoxin administered (intravenous bolus) 22 h later. In contrast, when a shorter LEH-endotoxin time interval (<12 h, n = 10) or a higher dose of endotoxin (14.4 mg/kg, n = 20) was tested, LEH enhanced endotoxin-induced mortality (90% and 100%, respectively, p < .05) and broadened serum tumor necrosis factor-alpha response without modifying its peak levels. LEH (n = 20) did not exacerbate the endotoxin-induced tachycardia, leukopenia, and thrombocytopenia. Therefore, in this model, the effect of LEH on endotoxin-induced responses was dependent on the time interval between LEH and endotoxin administration as well as the endotoxin dose. The clinical relevance of these results should be further investigated.

The novel chemokine mob-1: involvement in adult respiratory distress syndrome

BACKGROUND

Using differential display reverse transcriptase-polymerase chain reaction we have recently identified mob-1, the novel rat homologue of the human alpha-chemokine IP-10, as a highly inducible gene in adult respiratory distress syndrome (ARDS) lungs. The present study aimed to further implicate mob-1 in the pathogenesis of ARDS.

METHODS

Pulmonary mob-1 mRNA up-regulation was confirmed by Northern blot analysis in three different rat models of ARDS-like lung injury and localized to pulmonary macrophages by using in situ hybridization. Also, Escherichia coli-derived recombinant mob-1 (rmob-1) was tested for its properties in relationship to lung injury.

RESULTS

In vivo, intratracheal injection of rmob-1 (50 micrograms/rat) induced pulmonary leukosequestration (myeloperoxidase +93% +/- 8% versus control, p < 0.05) with preferential accumulation of neutrophils in bronchoalveolar lavage fluid (36.0% +/- 1.0% versus 0.1% +/- 0.1% in controls, p < 0.01). In vitro, transwell migration studies demonstrated chemotactic activity of rmob-1 (50 to 100 ng/ml) toward human monocytes (+151% +/- 34% versus rmob-1 vehicle, p < 0.01) and only weak chemotaxis for human neutrophils (+15% +/- 0% versus rmob-1 vehicle, p < 0.01). Utilizing a rat aortic ring model ex vivo, rmob-1 at 100 ng/ml exerted a very potent inhibitory effect on angiogenesis (-78.7% +/- 6.3% versus rmob-1 vehicle, p < 0.01), a major component of the resolution phase of ARDS.

CONCLUSIONS

Taken together, these data support the involvement of mob-1 in the pathogenic mechanisms of ARDS possibly through chemotaclic actions on inflammatory cells and modulation of angiogenesis in the recovery phase of the disease.

Platelet-activating factor (PAF) in experimental and clinical sepsis

Despite considerable progress in understanding the pathogenic mechanisms of Gram-negative sepsis, the outcome of septic patients has not significantly improved. There are ample data that support a role for inflammatory mediators in sepsis that act in synergy with infectious agents to initiate and propagate the disease process. One such mediator is the glycerophospholipid platelet-activating factor (PAF). The objective of the present review is to summarize experimental and clinical evidence implicating PAF as a mediator in the pathomechanism of sepsis. This review is timely because many potent and selective PAF antagonists have matured for clinical development and a careful analysis of the data that support or refute the merit of clinical trials with such compounds may be important for both academic and pharmaceutical applications.

Effect of liposome-encapsulated hemoglobin on triglyceride, total cholesterol, low-density lipoprotein, and high-density lipoprotein cholesterol measurements

The present study investigated the effect of liposome-encapsulated hemoglobin (LEH), an experimental oxygen-carrying resuscitation fluid, on triglyceride, total cholesterol, and low density lipoprotein (LDL), and high density lipoprotein (HDL) cholesterol measurements. In vivo, the intravenous infusion of LEH (5.6 mL/kg, n = 6) elevated serum triglycerides (+92% vs. baseline, P < .05), total cholesterol (+25% vs. baseline, P < .01), LDL cholesterol (+72% vs. baseline, P < .01) and had no effect on serum HDL cholesterol. In addition, LEH did not alter the elevation in serum triglycerides (+302% vs. baseline, P < .01) and LDL cholesterol (+86% vs. baseline, P < .01) induced by lipopolysaccharide (3.6 mg/kg, i.v., n = 6. Ex vivo, measurements of triglycerides and total cholesterol as well as LDL and HDL cholesterol in whole blood from naive rats were not changed by the addition of LEH (0-50%, n = 6). In vitro, the addition of a fixed concentration of LEH (50%, n = 6) to varying concentrations of cholesterol solution (0-50%), or vice versa, had no effect on cholesterol determination. It is therefore concluded that LEH only minimally affects serum levels of triglycerides, total cholesterol, LDL cholesterol, and HDL cholesterol and does not interfere with their measurement.

Candida pericarditis: clinical profile and treatment

BACKGROUND

Candida pericarditis is a rare medical and surgical emergency which, unless treated, leads to impaired cardiac function and death. To facilitate early diagnosis, the clinical features of this condition should be identified.

METHODS

Twenty-five cases of Candida pericarditis reported in the last 30 years along with 1 new case were reviewed with regard to demographics, precipitating factors, diagnosis, treatment, and outcome.

RESULTS

The syndrome occurred in immunocompromised (73%), antibiotic-treated (62%), or postpericardiotomy (54%) patients. The clinical presentation was frequently subtle and nonspecific. Nevertheless, unexplained fever, an increasing cardiac shadow on chest roentgenogram, or the development of cardiac tamponade may be suggestive. Positive culture for Candida in pericardial fluid or histologic evidence of yeast forms in pericardial tissue establishes the diagnosis. A combination of pericardiocentesis followed by operative drainage and antifungal agents is the usual treatment. Untreated, Candida pericarditis is 100% lethal, whereas prompt diagnosis and treatment lead to cure (mean follow-up, 19 months).

CONCLUSIONS

Fever and evolving cardiac tamponade in immunocompromised or postpericardiotomy patients may be suggestive of Candida pericarditis; the presence of organisms in pericardial fluid is diagnostic. Pericardiocentesis followed by operative drainage and antifungal agents appears to be the treatment that is most likely to be curative.

Platelet-activating factor and cardiac diseases: therapeutic potential for PAF inhibitors

Platelet-activating factor (PAF) is a potent phospholipid mediator released from inflammatory cells in response to diverse immunologic and non-immunologic stimuli. Animal studies have implicated PAF as a major mediator involved in coronary artery constriction, modulation of myocardial contractility and the generation of arrhythmias which may bear on cardiac disorders such as ischemia, infarction and sudden cardiac death. PAF effects are induced by direct actions of PAF on cardiac tissue to modify chronotropic and inotropic activity, or indirectly via the release of eicosanoids such as thromboxane A2 (TXA2), leukotrienes (LT) or cytokines (TNF alpha). The development of selective, high affinity PAF receptor antagonists has permitted investigations on the role of PAF in experimental animal models of cardiac injury. In vivo and in vitro studies strongly suggest that PAF receptor antagonists might convey therapeutic benefits in ischemic conditions and certain arrhythmias. In addition, PAF antagonists might have a cardiac allograft-preservation effect. Although clinical studies with PAF receptor antagonists in patients with cardiac diseases have not yet been reported, the experimental results to date suggest that PAF receptor antagonists might be useful in some specific cardiac disorders in humans.

Liposome-encapsulated hemoglobin modulates lipopolysaccharide-induced tumor necrosis factor-alpha production in mice

OBJECTIVE

To investigate the effect of liposome-encapsulated hemoglobin, an experimental blood substitute, on the function of the mononuclear phagocytic system in normovolemic mic, in ex vivo murine splenocytes and in a transformed murine monocytic cell line, RAW 264.7.

DESIGN

Prospective, randomized trial.

SETTING

Center for Biomolecular Science and Engineering, Naval Research Laboratory, and the Thomas Jefferson University.

SUBJECTS

Female Balb/c mice (n = 27).

INTERVENTIONS

Mice were injected into the tail vein with liposome-encapsulated hemoglobin or liposome vehicle and were killed at varying time points for blood sampling and splenocyte isolation and culture.

MEASUREMENTS AND MAIN RESULTS

Injection of liposome-encapsulated hemoglobin in mice (2.2 of lipid/kg and 0.56 g of hemoglobin/kg, n = 9) did not increase serum tumor necrosis factor (TNF)-alpha concentrations at 2, 8, 15, and 24 hrs after administration. In the ex vivo procedure, lipopolysaccharide (1 microgram/mL)-induced TNF-alpha production by splenocytes from mice injected with liposome-encapsulated hemoglobin was attenuated at 2 and 4 hrs (73%, p = .002 at 2 hrs), compared with TNF-alpha production by splenocytes from sham animals challenged with the same concentration of lipopolysaccharide. In the in vitro procedure, simultaneous exposure of liposome-encapsulated hemoglobin (0.88 to 8.8 mg/mL) and lipopolysaccharide (0.125 to 1 microgram/mL) to the murine-derived, peritoneal monocytic RAW 264.7 cell line showed significantly reduced TNF-alpha peptide, but not messenger RNA, 1 to 4 hrs after exposure as compared with cells challenged with lipopolysaccharide alone. This effect correlated with the rapid phagocytosis (1 hr to 4 hrs) of liposome-encapsulated hemoglobin by RAW 264.7 cells. Phagocytic activity in RAW 264.7 cells exposed to both liposome-encapsulated hemoglobin and lipopolysaccharide showed reduced uptake compared with uptake of liposome-encapsulated hemoglobin. The liposome-induced reduction in TNF-alpha peptide production elicited by lipopolysaccharide was countered by extending the time period to an overnight delay between liposome-encapsulated hemoglobin exposure and lipopolysaccharide challenge. Liposome-encapsulated hemoglobin incubated with lipopolysaccharide in vitro, and subsequently washed to remove free lipopolysaccharide, stimulated TNF-alpha expressed by RAW 264.7 cells. Incubation with liposome-encapsulated hemoglobin alone did not evoke TNF-alpha production in these cells.

CONCLUSIONS

These data suggest that liposome-encapsulated hemoglobin modulates the response of the mononuclear phagocyte system to endotoxin, possibly through binding of lipopolysaccharide, presentation to macrophages with subsequent phagocytosis, and modulation of cytokine response by a posttranscriptional mechanism. This effect is attenuated by extending the period between exposure to liposome-encapsulated hemoglobin and endotoxin. The clinical relevance of these findings awaits further investigation.

Locally produced tumor necrosis factor-alpha mediates interleukin-2-induced lung injury

Interleukin (IL)-2-induced microvascular lung injury is an experimental paradigm commonly used to investigate the pathogenesis of the adult respiratory distress syndrome. Since tumor necrosis factor-alpha (TNF-alpha) is known to induce such an injury in vivo and since TNF-alpha is involved in other models of lung injury, we postulated that it might also mediate pulmonary toxicity after IL-2 administration. The present study tested this hypothesis by evaluating the effect of TNF-alpha inhibition on IL-2-induced lung injury in the rat. Recombinant human IL-2 (10(6) U IV per rat, n = 6) elevated lung water, myeloperoxidase activity, and protein accumulation in bronchoalveolar lavage fluid and induced tissue hypoxia. Also, IL-2 enhanced lung tissue TNF-alpha mRNA and peptide (1543 +/- 496 pg/g lung wet weight) localized to alveolar macrophages by in situ hybridization. In marked contrast, IL-2 failed to affect serum TNF-alpha, which remained at undetectable levels. Pretreatment with anti-TNF-alpha monoclonal antibody (25 mg/kg IV, n = 7) or the TNF-alpha synthesis inhibitor rolipram (200 micrograms/kg IV, n = 7) attenuated lung injury and reverted tissue hypoxia. Furthermore, TNF-alpha inhibition prevented the upregulation of lung tissue IL-1 beta, IL-6, cytokine-induced neutrophil chemoattractant, and E-selectin (ELAM-1) but not intercellular adhesion molecule-1 mRNAs in response to IL-2. These data imply that locally produced TNF-alpha mediates IL-2-induced lung inflammation and tissue injury and point to the potential utilization of TNF-alpha inhibitors in treating the pulmonary toxicity of IL-2 immunotherapy.

Hypertonic saline treatment of acid aspiration-induced lung injury

Airway acid aspiration leads to severe microvascular lung injury and pulmonary edema. Recent studies have demonstrated that other conditions associated with microvascular injury such as sepsis and burns can be effectively treated with low-volume hypertonic saline (HTS). Thus, the present study aimed to test whether HTS attenuates aspiration-induced lung injury in the rat. Intratracheal administration of 0.2 ml of 0.1 N HCl (n = 7) induced pulmonary leukosequestration [myeloperoxidase (MPO) activity +446 +/- 34%, P < 0.05; bronchoalveolar lavage (BAL) fluid neutrophil count + 178 +/- 23%, P < 0.05], edema (division 43 +/- 6%, P < 0.01), and microvascular permeability defect (BAL protein concentration +675 +/- 34%, P < 0.01). These changes were associated with tissue hypoxia (skeletal muscle PO2, 49 +/- 8 mm Hg, P < 0.05) and elevated serum TNF alpha (750 +/- 38 pg/ml, P < 0.01). HTS (2400 mosmole/liter) at 5 ml/kg, administered 20 min after aspiration (n = 7), reduced lung pulmonary edema by 58 +/- 7% (P < 0.05) and improved tissue oxygen tension (PO2, 85 +/- 7 mm Hg, P < 0.05) but failed to alter lung MPO and BAL fluid protein and leukocyte count response. Also, HTS did not reduce TNF alpha response to aspiration. These data point to a potential therapeutic role for low-volume HTS in treating aspiration-induced lung injury. In addition, our data suggest that HTS is acting by rapidly shifting fluid from the pulmonary interstitium to the intravascular compartment because it did not inhibit the inflammatory response to aspiration.

Thoracic duct injury in penetrating neck trauma

Thoracic duct laceration from penetrating neck trauma is a rare injury associated with significant morbidity. Seventy-one cases published in the English literature in the last 50 years, along with one new case, were reviewed in an attempt to characterize the clinical profile, treatment, and outcome.

Mob-1 expression in IL-2-induced ARDS: regulation by TNF-alpha

We have recently established an animal model of adult respiratory distress syndrome (ARDS)-like microvascular lung injury elicited by infusion of human interleukin-2 (IL-2). Based on the pronounced, transcriptional upregulation of multiple pro-inflammatory mediators in IL-2-induced ARDS, differential display was applied to search for potentially novel genes in this paradigm of lung injury. Differential display on total lung RNA derived from IL-2-challenged rats presented a highly reproducible 3'-UTR fragment profile in which a band (approximately 250 bp), termed B1, was strongly induced. B1 cDNA sequence exhibited 99.14% homology to the 3'-UTR of mob-1, a recently cloned gene belonging to the C-X-C chemokine superfamily. Furthermore, Northern blot analysis showed that IL-2-induced pulmonary mob-1 mRNA was expressed at time points before the onset of lung injury and suppressed after TNF-alpha inhibition. These data imply that lung mob-1 is a novel, highly inducible gene in a clinically relevant model of ARDS and, based on its identification as a chemokine, could participate in the development of lung injury.

Aspiration-induced lung injury: role of complement

OBJECTIVES

To examine the role of complement in the development of acid aspiration-induced lung injury in the rat. It was postulated that inhibition or depletion of complement attenuates aspiration-induced lung injury.

DESIGN

Controlled animal trial.

SETTING

Animal Laboratory, Jefferson Medical College, Philadelphia, PA.

SUBJECTS

Anesthetized rats.

INTERVENTIONS

Aspiration was induced by the intratracheal administration of 0.2 mL of 0.1 N hydrochloric acid (n = 7) and lung injury was evaluated by determining water content, myeloperoxidase activity, protein concentration, and leukocyte count in bronchoalveolar lavage fluid. Muscle PO2 was directly measured using a thin-film chamber oxygen sensor and serum tumor necrosis factor-alpha was assayed by enzyme-linked immunosorbent assay. The effect of complement inhibition by recombinant human soluble complement receptor type 1 (n = 8) or complement depletion by cobra venom factor (n = 7) on lung injury was evaluated.

MEASUREMENTS AND MAIN RESULTS

Acid aspiration induced pulmonary leukosequestration, edema, and a microvascular permeability defect, along with tissue hypoxia. Pretreatment with soluble complement receptor type 1 (complement inhibition) or cobra venom factor (complement depletion) significantly reduced lung edema (-61 +/- 7%; p < .05), eliminated protein accumulation in bronchoalveolar lavage fluid (p < .01), and improved (p < .05) tissue oxygenation. In contrast, there was no effect of soluble complement receptor type 1 or of cobra venom factor on leukosequestration.

CONCLUSIONS

Acid aspiration induces lung injury through a complement-dependent mechanism that leads to microvascular permeability defects. Therefore, the possibility that complement inhibitors may have a salutary effect in humans with aspiration-induced lung injury should be investigated.

Lyophilized liposome encapsulated hemoglobin: evaluation of hemodynamic, biochemical, and hematologic responses

OBJECTIVE

To characterize the hemodynamic, biochemical, and hematologic responses to the administration of the oxygen-carrying fluid lyophilized liposome-encapsulated hemoglobin in the conscious, normovolemic rat.

DESIGN

Prospective, randomized trial.

SETTING

Animal laboratory, Jefferson Medical College.

SUBJECTS

Eighty-four male Sprague-Dawley rats.

INTERVENTIONS

Catheters were introduced into the right atrium (through the jugular vein) and both femoral arteries of test animals, and a thermistor was placed in the ascending aorta through the left common carotid artery for infusion of lyophilized liposome-encapsulated hemoglobin, blood collection, and blood pressure (BP) and cardiac output determinations.

MEASUREMENTS AND MAIN RESULTS

Lyophilized liposome-encapsulated hemoglobin (n = 8) infusion (1 mL/min iv) at 1 or 6 mL/kg (10% of estimated blood volume) had no detectable effect on BP, cardiac output, total peripheral resistance, and heart rate during the 5-hr observation period. The infusion also had no effect on hematocrit, leukocyte count, and serum tumor necrosis factor-alpha concentrations. Survival at 7 days was 100% (n = 20). Lyophilized liposome-encapsulated hemoglobin caused transient (2-hr) thrombocytopenia (-24 +/- 9% vs. a Ringer's lactate control group, p < .01), and marginally increased serum thromboxane B2 concentrations (14.6 +/- 6 pg/100 microL, p < .01).

CONCLUSIONS

These data suggest that lyophilized liposome-encapsulated hemoglobin can be safely administered to conscious rats, supporting the development of this substance as a potential blood substitute.

Interleukin-2-induced lung injury. The role of complement

Pulmonary edema and sepsis-like syndrome are grave complications of interleukin-2 (IL-2) therapy. Recent animal studies have suggested IL-2-induced microvascular injury as the underlying mechanism. Since complement factors have been shown to mediate increased vascular permeability in diverse conditions that lead to pulmonary injury and recombinant human IL-2 is known to activate the complement system in patients undergoing IL-2 therapy, we hypothesized that complement factors play a pivotal role in the development of increased vascular permeability after IL-2 treatment. To test this hypothesis, we evaluated the capacity of recombinant soluble human complement receptor type 1 (sCR1, BRL 55730), a new highly specific complement inhibitor, to attenuate IL-2-induced lung injury in the rat. Recombinant human IL-2 (intravenously for 60 minutes) at 10(6) U per rat (n = 4) elevated lung water content (37 +/- 6%, P < .05), myeloperoxidase activity (162 +/- 49%, P < .05), and serum thromboxane B2 (30 +/- 1 pg/100 microL, P < .01) and had no effect on serum tumor necrosis factor-alpha sCR-1 at 30 mg/kg (n = 5), but not at 10 mg/kg (n = 6), attenuated the elevation of lung water content (18 +/- 2%, P < .05) and myeloperoxidase activity (42 +/- 9%, P < .05) but failed to alter serum thromboxane B2 response to IL-2. These data suggest the involvement of complement in the pathogenesis of IL-2-induced pulmonary microvascular injury and point to the potential therapeutic capacity of complement inhibitors in combating this toxic effect of IL-2 therapy.

Tumor necrosis factor-alpha mediates endotoxin-induced lung injury in platelet activating factor-primed rats

We have reported recently that lipopolysaccharide endotoxin and platelet activating factor cooperate in priming relationships to elicit lung microvascular injury. Lung injury was associated with elevated serum levels of tumor necrosis factor-alpha (TNF alpha) and histological findings highly reminiscent of the adult respiratory distress syndrome. The present study was designed to examine the role of TNF alpha in lipopolysaccharide/platelet activating factor-induced lung injury by utilizing a highly specific monoclonal antibody which block TNF alpha actions (anti-TNF alpha monoclonal antibody). Pretreatment with anti-TNF alpha monoclonal antibody (2.5-25 mg/kg i.v., n = 5-9) dose-dependently prevented the lipopolysaccharide/platelet activating factor-induced histopathological changes, lung edema (P < .01), lung myeloperoxidase activity (P < .01), elevation of neutrophil count in bronchoalveolar lavage fluid (P < .01) and increased serum thromboxane B2 (P < .01). Indomethacin (6 mg/kg i.v., n = 5) failed to modify the lung injury despite complete inhibition of thromboxane B2 formation (P < .05). These data suggest that TNF alpha might play a key role in initiation of the early inflammatory changes which lead to adult respiratory distress syndrome.

Serum tumor necrosis factor-alpha profile in trauma patients

Tumor necrosis factor-alpha (TNF-alpha) has been implicated in several late consequences of trauma such as sepsis, multiple organ failure, and ischemia-reperfusion injury. However, no data are available to indicate whether TNF-alpha is involved in the initial pathophysiologic response to trauma. To address this issue, serum TNF-alpha was determined (by ELISA) longitudinally (first blood sample on admission) in 100 randomly selected trauma patients admitted to the emergency department and trauma division at Jefferson Medical Center, Philadelphia. The TNF-alpha levels were detectable at one or more time points in 35 patients. Mean values tended to be elevated (50.3 +/- 11.5 pg/mL) during the first 5 days, but this trend did not differ statistically from that in healthy controls (n = 12) and did not correlate with the severity of injury (Injury Severity Score and Glasgow Coma Scale score). The TNF-alpha response was not dependent on the mechanism and site of injury, the presence of shock (systolic blood pressure < 90 mm Hg), and the need for emergent surgery. Also, serum TNF-alpha levels were not significantly elevated in patients who subsequently developed multiple organ failure (n = 4), septic shock (n = 5), or both (n = 3). Taken together, these data do not support a role for circulating TNF-alpha in the initial acute inflammatory response to trauma.

A new salutary resuscitative fluid: liposome encapsulated hemoglobin/hypertonic saline solution

Low-volume resuscitation with hypertonic (7.5%) saline (HTS) is an evolving therapeutic modality for patients with hemorrhagic shock. This solution has been shown to exert protective hemodynamic effects in models of controlled hemorrhagic shock and in several clinical trials. However, HTS has no oxygen-carrying capacity and therefore does not improve oxygen delivery directly. One of the leading strategies in developing an oxygen-carrying resuscitative fluid is the encapsulation of hemoglobin within phospholipid vesicles (LEH). This preparation has the advantage of being blood type and antigen free, easily adaptable to scale-up production, and remarkably stable with a long shelf life. We therefore tested the hypothesis that lyophilized LEH reconstituted with HTS will improve tissue oxygenation and survival in rats exposed to a lethal controlled hemorrhagic shock. Shock was induced by withdrawal of 70% of blood volume and therapy (n = 10-16) with HTS (5 mL/kg), LEH (5 mL/kg), lactated Ringer's solution (vol:vol = 1:3), LEH-HTS (5 mL/kg), or oxygen (100%) was initiated 15 minutes later. The LEH-HTS improved skeletal muscle oxygen tension directly measured using a thin-film chamber oxygen sensor (PO2 87 +/- 13 mm Hg vs. 40-50 mm Hg in other groups, p < 0.05). This was associated with improved blood pressure, reduced acidosis, and increased survival at 24 hours (75% vs. 6%-25% in other groups, p < 0.05). In conclusion, the study demonstrates a remarkably salutary effect of LEH reconstituted with HTS as a blood substitute in the treatment of hemorrhagic shock.

ARDS-like lung injury produced by endotoxin in platelet-activating factor-primed rats

We recently reported that the combined administration of lipopolysaccharide (LPS) and platelet-activating factor (PAF) in rats, at doses that are completely devoid of any effect when given alone, caused lung injury characterized by neutrophil adhesion to lung capillaries and postcapillary venules, neutrophil accumulation in the lung parenchyma, platelet-fibrin deposits in postcapillary venules, and pulmonary edema. A marked increase in lung myeloperoxidase activity and an elevation of serum tumor necrosis factor-alpha and thromboxane B2, along with leukopenia and thrombocytopenia, were also noticed. The present study aimed to examine whether repeated LPS-PAF stimulus can cause progressive lung injury reminiscent of adult respiratory distress syndrome (ARDS). A second LPS-PAF challenge, 4 h (n = 11) after the original challenge, induced mortality (69% at 24 h, P < 0.01) and some of the pathological changes seen in clinical ARDS, including severe pulmonary edema, alveolar proteinaceous exudates, monocytic infiltration, and a further increase in lung myeloperoxidase activity (700%, P < 0.01). Repeated LPS-PAF dosing also resulted in sustained increased serum tumor necrosis factor-alpha levels (1,610 +/- 470 pg/ml, P < 0.01) and further exacerbation of the leukopenia (-68 +/- 6%, P < 0.01) and thrombocytopenia (-65 +/- 8%, P < 0.01). These data suggest that repeated LPS-PAF actions are sufficient to elicit pathophysiology of ARDS-like lung injury.

Hemodynamic, hematologic and eicosanoid mediated mechanisms in 7.5 percent sodium chloride treatment of uncontrolled hemorrhagic shock

Hypertonic saline solution (HTS) (7.5 percent sodium chloride [NaCl]) treatment (5 milliliters per kilogram) of rats subjected to uncontrolled hemorrhagic shock (n = 7) caused an initial partial recovery of blood pressure (+38 +/- 5 percent, p<0.05) and cardiac index (+48 +/- 6 percent, p<0.01) followed by increased bleeding (+53 +/- 5 percent versus rats treated with 0.9 percent NaCl, p<0.05), secondary shock (mean arterial pressure [MAP] 23 +/- 7 millimeters of mercury, p<0.01) and decreased survival (-54 +/- 15 minutes versus control, p<0.05). The increased blood loss resulted from: 1, increased vascular pressure and vasodilatation (total peripheral resistance index -27 +/- 5 percent, p<0.05), as initial bleeding occurred when MAP and cardiac index are increased compared with the control group (+88 +/- 10 percent, p<0.05 and +82 +/- 7 percent, p<0.01, respectively) and as the concomitant infusion of angiotensin II, a potent vasoconstrictor, delayed the HTS-induced bleeding (resumed at 60 minutes), and 2, a defect in platelet aggregation reflected by decreased adenosine diphosphate (ADP)-induced maximal aggregation (-79 percent versus rats treated with 0.9 percent NaCl, p<0.05) and increased EC50 of ADP (+159 percent, p<0.05). These hemodynamic and hematologic responses might be mediated at least in part by prostacyclin, a vasodilator and antiplatelet aggregator, as HTS-treated rats markedly elevated the 6-keto-PGF1 alpha per thromboxane B2 ratio (+140 +/- 12 percent, p<0.01) and pretreatment with indomethacin decreased blood loss and improved MAP and survival. These data point out potential untoward hemodynamic and hematologic consequences of HTS treatment in traumatic injury in which control of bleeding cannot be confirmed.

Role of complement in endotoxin/platelet-activating factor-induced lung injury

C receptor-1 is a protein involved in the regulation of C3 and C5-convertases. Recombinant human soluble C receptor-1 has recently been produced and shown to reduce infarct size in a rat model of myocardial ischemia/reperfusion injury. The present study aimed to investigate whether recombinant human soluble C receptor-1 exerts any protective effect on pulmonary injury produced in a rodent model of adult respiratory distress syndrome. In this model, Escherichia coli endotoxin (LPS, 0.1 microgram/kg) combined with platelet-activating factor (1 pmol/kg/min over 60 min, n = 10) caused microvascular lung injury characterized by elevation of myeloperoxidase activity, deposition of C3 and C5b-9 on the endothelium of pulmonary vessels, and pulmonary edema. Furthermore, bronchoalveolar lavage revealed increased neutrophil count and elevated protein concentration. These pulmonary responses were associated with elevated serum TNF-alpha. Pretreatment (10 min, i.v.) with recombinant human soluble C receptor-1 at 10 mg/kg (n = 13), but not at 1 mg/kg, prevented the LPS/platelet-activating factor-induced pulmonary edema (p less than 0.01) and changes in the bronchoalveolar lavage fluid cell count (p less than 0.01) and protein concentration (p less than 0.05), and attenuated the deposition of C3 and C5b-9 to lung vessels. There was no effect on lung myeloperoxidase activity and serum TNF-alpha. Also, C depletion by cobra venom factor (500 U/kg, i.v.) eliminated the pulmonary edema and elevated leukocyte count in bronchoalveolar lavage fluid, but had no effect on lung myeloperoxidase activity and serum TNF-alpha. These data suggest that C factors may play an important role in the pathophysiology of adult respiratory distress syndrome.

Role of complement in endotoxin/platelet-activating factor-induced lung injury

C receptor-1 is a protein involved in the regulation of C3 and C5-convertases. Recombinant human soluble C receptor-1 has recently been produced and shown to reduce infarct size in a rat model of myocardial ischemia/reperfusion injury. The present study aimed to investigate whether recombinant human soluble C receptor-1 exerts any protective effect on pulmonary injury produced in a rodent model of adult respiratory distress syndrome. In this model, Escherichia coli endotoxin (LPS, 0.1 microgram/kg) combined with platelet-activating factor (1 pmol/kg/min over 60 min, n = 10) caused microvascular lung injury characterized by elevation of myeloperoxidase activity, deposition of C3 and C5b-9 on the endothelium of pulmonary vessels, and pulmonary edema. Furthermore, bronchoalveolar lavage revealed increased neutrophil count and elevated protein concentration. These pulmonary responses were associated with elevated serum TNF-alpha. Pretreatment (10 min, i.v.) with recombinant human soluble C receptor-1 at 10 mg/kg (n = 13), but not at 1 mg/kg, prevented the LPS/platelet-activating factor-induced pulmonary edema (p less than 0.01) and changes in the bronchoalveolar lavage fluid cell count (p less than 0.01) and protein concentration (p less than 0.05), and attenuated the deposition of C3 and C5b-9 to lung vessels. There was no effect on lung myeloperoxidase activity and serum TNF-alpha. Also, C depletion by cobra venom factor (500 U/kg, i.v.) eliminated the pulmonary edema and elevated leukocyte count in bronchoalveolar lavage fluid, but had no effect on lung myeloperoxidase activity and serum TNF-alpha. These data suggest that C factors may play an important role in the pathophysiology of adult respiratory distress syndrome.

"Scoop and run" or stabilize hemorrhagic shock with normal saline or small-volume hypertonic saline?

The controversy over a policy of "scoop and run" or stabilizing hemorrhagic shock when evacuation time is short has not yet been settled. Small volumes of hypertonic saline have been suggested as effective therapy when the scoop-and-run policy is adopted. In the present study small-volume hypertonic saline treatment and normal saline treatment of "uncontrolled" hemorrhagic shock (UCHS) in rats were compared with no treatment, which best simulates the scoop-and-run policy. The rats were randomly assigned to three groups. Uncontrolled hemorrhagic shock was induced by 12% resection of the terminal portion of the rats' tails. In group I (n = 13) the animals were untreated. In group II (n = 6) UCHS was treated by administering 41.5 mL/kg 0.9% NaCl (NS). In group III (n = 6) UCHS was treated by administering 5 mL/kg 7.5% NaCl (HTS). Resection of the rats' tails in group I was followed by bleeding of 3.3 +/- 0.3 mL in 15 minutes with a fall in mean arterial pressure (MAP) from 100.9 +/- 7 to 63.5 +/- 5 mm Hg (p less than 0.001). The early bleeding and hemodynamic responses were similar in all three groups. Further blood loss in the first hour in group I was 0.5 +/- 0.2 mL, and MAP rose spontaneously to 73.2 +/- 6 mm Hg (p less than 0.05). The NS infusion in group II was followed by further bleeding of 4.1 +/- 0.9 mL (p less than 0.01) and a further fall in MAP to 53.8 +/- 7 mm Hg (p less than 0.01) after 60 minutes.(ABSTRACT TRUNCATED AT 250 WORDS)

Pharmacological profile of G619, a new platelet aggregation inhibitor

G619, a 4-OH-isophthalic acid derivative, was studied for its capacity to inhibit platelet aggregation. G619 dose-dependently inhibited U46619, collagen, ADP, PAF, thrombin and epinephrine-induced platelet aggregation in vitro. The IC50 values for inhibition of U46619-induced human and rabbit platelet aggregation were 39 and 43 microM, respectively. G619, at 100 microM, inhibited high concentration collagen (10 micrograms/ml)-induced aggregation of rabbit platelets pretreated with indomethacin and increased the level of cAMP in washed rabbit platelets by 30% (p less than 0.01 vs basal). However, G619, did not inhibit fibrinogen binding to GPIIb/IIIa receptor, phosphodiesterase, U46619-induced contractile responses on canine saphenous vein or rabbit aorta, calcium-induced vasoconstriction and thrombin or PAF-induced elevation of [Ca++]i in platelets in vitro. In vivo, the U46619-induced maximal thrombocytopenia in rats was reduced from 40% (vehicle) to 22% and 18% by 10 and 30 mg/kg of G619 i.v., respectively. G619 (30 mg/kg) had no effect on the U46619-induced vasopressor response or sudden death in rats, and had no effect on TxB2 formation. Our results indicate that G619 is a broad-spectrum platelet aggregation inhibitor and may have its effect on a common mechanism for platelet aggregation besides an effect on the thromboxane A2 receptor.

Platelet activating factor mediates interleukin-2-induced lung injury in the rat

Interleukin-2 was recently shown to cause acute lung injury characterized by microvascular permeability defect, interstitial edema, and leukosequestration. Similar responses can also be produced by platelet activating factor (PAF). Thus, the present study aimed to examine whether PAF plays a key role in the development of IL-2-induced lung injury in the anesthetized rat. Intravenous infusion (60 min) of recombinant human IL-2 at 10(5)-10(6) U/rat (n = 7-9) dose-dependently elevated lung water content (27 +/- 1%, P less than 0.01), myeloperoxidase activity (+84 +/- 23%, P less than 0.05), and serum thromboxane B2 (990 +/- 70%, P less than 0.01), but failed to alter blood pressure, hematocrit, serum tumor necrosis factor-alpha, and circulating leukocytes and platelets. Pretreatment (-30 min) with a potent and specific PAF antagonist, BN 50739 (10 mg/kg, intraperitoneally, n = 6) prevented the pulmonary edema (P less than 0.05) and thromboxane B2 production (P less than 0.01), and attenuated the elevation of lung myeloperoxidase activity (+18 +/- 16%, P less than 0.05) induced by IL-2. These data suggest that PAF is involved in the pathophysiological processes leading to IL-2-induced lung injury, and point to the potential therapeutic capacity of PAF antagonists in preventing pulmonary edema during IL-2 therapy.

Platelet-activating factor in cardiovascular stress situations

Since the elucidation of its chemical structure two decades ago, platelet-activating factor (PAF) has emerged as an important mediator of various cardiovascular stress situations. Most notably, PAF was implicated as a key factor in the septic shock syndrome, based on the similarities between endotoxin and PAF biological effects, the elevation of circulating and tissue levels of PAF during endotoxemia, and the protective effect of PAF antagonists in the septic state. In addition, accumulating data suggest the involvement of PAF in the pathophysiological processes associated with ischemia, hemorrhage and trauma, where PAF exerts its effects directly on cells and blood elements or indirectly through interactions with other mediators such as cytokines and prostaglandins. Nevertheless, the relative contribution of PAF to the pathophysiological processes in endotoxemia is still unknown and should await further investigations. The primary aims of this chapter are: to delineate the effects of PAF on the cardiovascular system, to summarize the data which suggest the involvement of PAF in stress situations of the cardiovascular system, and to identify areas where future experimental efforts should be focused.

Effect of injured vessel size on bleeding following hypertonic saline infusion in "uncontrolled" hemorrhagic shock in anesthetized rats

Hypertonic saline (HTS) infusion in "uncontrolled" hemorrhagic shock (UCHS) leads to increased bleeding from injured vessels, fall in mean arterial pressure (MAP), and early mortality. The effect of injured vessel size on blood loss in response to HTS treatment was studied in Neurolidal Ketalar anesthetized Hebrew University strain rats. The animals were randomly assorted into 4 groups: In group I (n = 8) UCHS was induced by resection of 8% of the terminal portion of the rats' tail and the animals were untreated. In group II (n = 8) UCHS was induced as in group I and the animals were treated with 5 ml/kg NaCl 7.5% (HTS). In group III (n = 9) UCHS was induced by 50% resection of the animal's tail, and the animals were untreated. In group IV (n = 12) UCHS was induced as in group III and the animals were treated with 5 ml/kg HTS Resection of 8% of the animal's tail was followed by bleeding of 2.6 +/- 0.3 ml and fall in MAP from 107 +/- 7 to 80 +/- 10 torr (P less than .005) within 5 min. Resection of 50% of the animal's tail was followed by bleeding of 4.3 +/- 0.4 ml (P less than .01) and fall in MAP to 41 +/- 6 torr (P less than .001) after 5 min. Infusion of HTS in group II was followed by further blood loss of 4.9 +/- 07 ml within 4 hr while in untreated group I, blood loss was only 3.4 +/- 0.4 ml (P less than .05), MAP remained unchanged, and there was no mortality.(ABSTRACT TRUNCATED AT 250 WORDS)

Control of bleeding is essential for a successful treatment of hemorrhagic shock with 7.5 per cent sodium chloride solution

Small volume hypertonic saline (HTS) solution resuscitation has been shown to restore hemodynamic derangements and to protect against mortality in "controlled" hemorrhagic shock (CHS), but it exacerbates the shock state in "uncontrolled" hemorrhagic shock (UCHS). To study the mechanisms associated with the divergent outcome of HTS treatment in CHS versus UCHS, HTS was administered to anesthetized rats (n = 7) subjected to 15 per cent resection of the tail followed by controlled or uncontrolled bleeding. HTS treatment of UCHS increased bleeding (13.3 +/- 1.6 milliliters, p less than 0.05), dropped mean arterial pressure (MAP) (-84.5 +/- 8.9 millimeters of mercury, p less than 0.001), central venous pressure (zero millimeters of mercury, p less than 0.001) and cardiac index (CI) (41 per cent of basal value, p less than 0.001) and increased acidosis (pH 7.23 +/- 0.12, p less than 0.05) and mortality (mean survival time 75 +/- 15 minutes versus 122 +/- 23 minutes of untreated rats, p less than 0.05). In contrast, when administered after application of a ligature proximal to the resection site (at 15 minutes), HTS completely reversed the changes in MAP, CI and total peripheral resistance index (TPRI), and improved mean survival time (172 +/- 7 minutes, p less than 0.05). These data support the assumption that HTS should be used in the treatment of hemorrhagic shock only after bleeding was controlled.

Priming by platelet-activating factor of endotoxin-induced lung injury and cardiovascular shock

Platelet-activating factor (PAF) is a glycerophospholipid known for its unusual potent vasoactive and proinflammatory activities. The present study examined whether PAF might serve as a priming factor in endotoxin-induced tumor necrosis factor-alpha (TNF alpha) synthesis, cardiovascular shock, and lung injury in anesthetized rats. Intravenous infusion of PAF (1 pmol/kg/min for 60 minutes, n = 5) alone or endotoxin (0.1 micrograms/kg i.v. bolus, n = 5) failed to alter blood pressure, serum TNF alpha and thromboxane B2, platelet and leukocyte count, and hematocrit, nor was lung histology, myeloperoxidase activity, and water content changed. In contrast, the combined administration of PAF and endotoxin markedly elevated serum TNF alpha (1,359 +/- 362 pg/ml, n = 5, p less than 0.01) and thromboxane B2 (43 +/- 5 pg/100 microliters, n = 8, p less than 0.01) along with hypotension, hemoconcentration, leukopenia, and thrombocytopenia. Most notably, the combined regimen caused neutrophil aggregation, adhesion, and accumulation into the lung parenchyma along with platelet-fibrin deposits in postcapillary venules, pulmonary edema, and increased lung myeloperoxidase activity. The role of PAF in this process was confirmed by 1) the prevention of the priming effect by pretreatment with the PAF antagonist BN 50739 (n = 5), and 2) the failure of lyso-PAF, the cardinal nonactive PAF-metabolite, to prime for endotoxin-induced production of TNF alpha (n = 4). These data suggest that PAF could serve as a key mediator in priming for endotoxin-induced tissue injury, especially the typical pulmonary pathophysiology of adult respiratory distress syndrome, a severe pathological outcome of septic shock, burns, and multiple organ injury.