The complexity of the anatomic pelvis presents a unique diagnostic challenge after injury from gunshot wounds. The purposes of this study were: (1) to determine the clinical utility of pelvic CT in identifying injuries and determining need for operative intervention, and (2) to determine if pelvic CT obviates the need for adjunct diagnostic studies such as rigid sigmoidoscopy and cystography. We hypothesized that pelvic CT is a reliable diagnostic tool and may obviate the need for additional diagnostic studies.

Introduction: Phosphatidylserine (PS) is a membrane phospholipid, whose orientation is usually maintained facing intracellularly via an energy dependent process in the unstressed cell. Cellular injury results in exteriorization of PS to the outer cell membrane and PS extracellular exposure provides a signal for the initiation of inflammatory cascades and cellular dysfunction. As such phosphatidylserine may be a key lipid signal during sepsis. Our hypothesis was that PS signaling mediates gut and renal dysfunction during sepsis. Methods: Anesthetized adult female Sprague-Dawley rats were infused for 4 hours with: 1) lactated ringers (control), 2) 0.65mg/hour of lipopolysaccharide (sepsis), or 3) 0.65mg/hour of lipopolysaccharide + diannexin 400mcg/kg (sepsis+PS blockade). PS signaling was blocked with diannexin, which has a high binding affinity for PS and prevents the signaling interactions of PS. to evaluate gut dysfunction, a mesenteric post-capillary venule was cannulated to measure microvascular leak (Lp) throughout the infusion period. to evaluate renal dysfunction, blood samples were taken for creatinine analysis. Lp units are listed as x10−7 cm*s−1*cmH2O−1. Data is presented as mean ± standard error of the mean, statistical analysis was performed with analysis of variance. Results: Microvascular leak remained stable throughout the study in controls (Lp=1.08–1.11) . Microvascular leak increased by more than 2-fold during sepsis from a baseline of 1.12± 0.04 to a peak of 2.56 ± 0.13, (p< 0.01). During the first two hours of sepsis+PS blockade, microvascular leak was similar to that of sepsis alone (peak Lp=1.52 ± 0.01), however after the two hour time point, PS blockade reduced Lp to control levels (Lp=1.13 ± .02, p < 0.01, Fig 1). Throughout the study period, creatinine in controls remained stable, while during sepsis alone creatinine increased 40% and during sepsis+PS blockade this effect was attenuated as creatinine increased by only 20%. Conclusions: Phosphatidylserine blockade had a protective effect on gut and renal end organ dysfunction during sepsis. Phosphatidylserine may be a key cellular signal of cellular dysfunction during sepsis and this may provide insights into novel treatment options for septic patients.

Introduction: Lysophosphatidic Acid (LPA) is a lipid mediator that disturbs endothelial barrier function and can precipitate endothelial cell loss. LPA is synthesized through the conversion of lysophosphatidylcholine to LPA catalyzed by the enzyme autotaxin (ATX). LPA initiates intracellular cascades by binding G-protein receptors on endothelial cells which leads to deterioration of endothelial barrier function. Our hypothesis was that LPA governs microvascular fluid leak and plays a critical role during ischemia-reperfusion injury (IRI). Our specific aims were: 1) to determine the effect of LPA on microvascular fluid leak, 2) to evaluate the impact of inhibiting LPA synthesis on endothelial cell monolayer permeability during anoxia/reoxygenation and on microvascular fluid leak during IRI, and 3) to evaluate the impact of LPA receptor blockade on microvascular fluid leak during IRI. Methods: in vivo mesenteric venular microvascular fluid leak (Lp) was examined using an intra-vital micro-occlusion technique in rats. First, Lp was analyzed in rats treated with increasing doses of LPA as well LPA + L-NAPSA, a selective LPA receptor antagonist. Next, in vitro monolayer permeability to biotinylated albumin in cultured bovine pulmonary artery endothelial cells was assessed using an absorbance assay during anoxia/reoxygenation with and without H2L9098, a selective inhibitor of ATX that prevents LPA synthesis. in vivo, Lp was analyzed in rats treated with and without H2L9098 during IRI. Finally, we treated rats with L-NAPSA, the selective LPA receptor antagonist, during the reperfusion phase of IRI and Lp was measured throughout IRI for each group as well as for controls. Results: In vivo, LPA increased Lp up to 4-fold in a dose dependent manner (p<0.001) and the LPA receptor antagonist completely blocked this response. Preventing LPA synthesis by ATX inhibition in vitro attenuated a 4.4-fold increase in monolayer permeability induced by anoxia/reoxygenation and returned monolayer permeability back to control levels (p<0.01). in vivo, IRI increased Lp approximately 8-fold. This increase was attenuated 37% by preventing LPA synthesis via ATX inhibition prior to and during IRI (p<0.05). Lp during IRI was decreased by 78% with the LPA receptor antagonist given during reperfusion (p<0.01). Conclusions: LPA governs microvascular fluid leak and plays a critical role during IRI. LPA induces microvascular fluid leak in a dose dependent manner. Preventing LPA synthesis through ATX inhibition attenuates microvascular permeability increases due to IRI. Additionally, LPA receptor antagonism decreases the microvascular fluid leak during IRI. the LPA cell surface receptor is an early common pathway for LPA induced endothelial barrier dysfunction and is a potential therapeutic target for treating microvascular fluid leak observed during IRI.

Introduction: Airway management is the number one priority in trauma resuscitation. Patients in cardiopulmonary distress or with airway protection issues clearly need immediate intubation. Despite relatively standard indications for acute post-trauma intubation, there may be a subset of patients who appear clinically stable upon presentation but later deteriorate and require immediate intubation. We sought to determine whether less severely injured patients with delayed intubation have worse outcomes, and to determine any potential risk factors that may predict the need for earlier intubation in this patient population. Our hypothesis was that less severely injured trauma patients with a delay in intubation have higher mortality than those patients intubated earlier with similar injury severity. Methods: Medical records of trauma patients who were endotracheally intubated in the emergency department were reviewed at our university-based trauma center. Our analysis included: time to intubation, ventilator days, length of stay, injury severity score (ISS), and mortality. Further analysis included potential contributing injuries including rib fractures, pulmonary contusions, facial fractures, hemothorax, and pneumothorax. Early intubation was defined as less than 30 minutes while delayed intubation was greater than or equal to 30 minutes between arrival and intubation. Less severely injured patients were defined as an ISS <=20. Results: We evaluated 127 consecutive trauma patients who were intubated in the emergency room. Patients with an ISS <=20 had a greater mortality with delayed intubation versus early intubation (14% versus 2%, respectively). When we excluded early traumatic deaths (<20 minutes) and compared those intubated at later time intervals, overall mortality was greater in patients intubated >59 minutes from arrival (29%) versus those intubated 20-59 minutes from arrival (12%). This difference in mortality was magnified when we looked exclusively at patients with an ISS<=20 (40% vs. 8%). Patients with an ISS<=20 who had a delayed intubation were more frequently associated with the diagnosis of pulmonary contusion (6% vs. 2%), rib fractures (17% vs. 4%), facial fractures (33% vs. 25%), and pneumonia (11% vs. 7%) compared to their early intubation counterparts. Conclusions: These findings suggest that specific injuries can potentially predict the need for earlier intubation. Identifying this subgroup of less severely injured trauma patients who are at risk of airway compromise may prevent the higher mortality associated with delayed intubation.

Introduction: Phospholipid Scramblase-1 (PLSCR-1) is a calcium-dependent plasma membrane protein responsible for the asymmetric distribution of phospholipids in endothelial cell membranes. Central to its activity is the ability to rapidly translocate phosphatidylserine from the inner leaflet of the plasma membrane to the outer leaflet. Exposure of phosphatidylserine on the cell surface is a signal for phagocytes to engulf endothelial cells undergoing apoptosis, which is one mechanism responsible for endothelial damage during ischemia-reperfusion injury (IRI). We have found that there is a bimodal increase in microvascular permeability during IRI. Our hypothesis was that PLSCR-1 inhibition would attenuate the bimodal increase in microvascular permeability (Lp) during IRI. Methods: A micro-occlusion technique was used to measure mesenteric microvascular permeability (Lp) in rats subjected to IRI induced by superior mesenteric artery occlusion. Rats undergoing IRI were pretreated with dithioerythritol (DTE), an inhibitor that reacts with the thiol moiety of PLSCR-1 (n=3) and 4,4'-diisothiocyano-stilbene-2,2'-disulfonic acid (DIDS), an inhibitor of the calcium-activated phospholipase translocation activity of PLSCR-1 (n=3). Finally, RNA interference was used to knock down PLSCR-1 expression using small-interfering RNA (siRNA) and the Lp measured during IRI (n=3). Results: Compared to controls, DTE inhibition attenuated Lp 35% during the 1st peak and 46% during the 2nd peak of IRI (p<0.0001). DIDS inhibition attenuated Lp 50% (p<0.0001) during the 1st peak and 23% during the 2nd peak of IRI (p<0.05). RNA interference had the most robust inhibition as siRNA knockdown of PLSCR-1 attenuated Lp 67% during the 1st peak and 74% during the 2nd peak of IRI (p<0.0001). (See Figure 1) Conclusion: These results suggest that scramblase is a key enzyme that regulates microvascular permeability during IRI. The results also suggest that inhibition is mechanism-dependent and phase-selective. Inhibition of scramblase, depending on reagent and mode of activity, may have therapeutic value at different times in the two-phase IRI model. Based on mechanism we may target different phases of IRI and help attenuate the increased endothelial microvascular permeability observed during IRI.

Microvascular fluid leak increases in the presence of the lipid mediator, lysophosphatidic acid (LPA). We hypothesized that phosphatidyl serine (PS) shifts from the inner to the outer endothelial cell membrane, that exposed PS stimulates formation of LPA by secretory phospholipase A2 (sPLA2), and that phospholipid scramblase 1 (PLSCR1) regulates the shift of PS from the inner to the outer cell membrane during ischemia reperfusion (IR). Our specific aims were: 1) to examine if PS shifts from the inner to the outer endothelial cell membrane, 2) to determine if PS-exposing cells in combination with sPLA2 exacerbates microvascular fluid leak, and 3) to inhibit the shift of PS to the outer membrane by using RNA interference (RNAi) to knockdown PLSCR1 and measure the effect on microvascular fluid leak during IR.

INTRODUCTIONThe conventional view that admission lactate levels predict outcome in trauma patients stems from simple comparisons of mean blood levels between groups and small sample sizes. To better address this question, we performed more rigorous statistical analyses of lactate in a larger patient sample.METHODSWe prospectively collected data on admission lactate and outcomes in 5,995 patients admitted to an urban, university-based trauma center. The ability of admission lactate to predict mortality was assessed by logistic regression, calculation of positive predictive values (PPV), and measurement of areas under receiver operating characteristic (ROC) curves.RESULTSDifferences between survivors and nonsurvivors in means of most proposed prognosticators was again demonstrated. However, the large overlap in these variables between survivors and nonsurvivors prevented clinically useful predictions. The overall PPV of elevated lactate was only 5.4%. Even in severely injured patients (Injury Severity Score >20; mortality 23%), elevated admission lactate level was a poor predictor of outcome. ROC analyses found no useful sensitivity threshold overall or after stratification by age, sex, Glasgow Coma Scale score, revised trauma score, or mechanism of injury.CONCLUSIONSThis large retrospective examination of admission lactate levels failed to show useful predictive accuracy for hospital death. Serum lactate levels need not be obtained routinely but can be reserved for patients who will be admitted to the intensive care unit and/or require an emergency operation.

Introduction. Angiotensin II receptor subtypes (AT1 and AT2) have been shown to modulate microvascular fluid leak. However, their intracellular signal transduction pathways have not been elucidated. We hypothesized that AT1 activation exerts its permeability-increasing effect by provoking cGMP synthesis and inducing cAMP degradation and that AT2 activation decreases fluid leak by stimulating cAMP synthesis and enhancing cGMP degradation.Methods. Using a microcannulation technique, hydraulic permeability (L-p) was measured in rat mesenteric venules. The messenger signal transduction of AT1 was studied during continuous perfusion with the AT1 agonist, Sar1 plus either 1) a cGMP synthesis inhibitor, LY83583, or 2) an inhibitor of cAMP degradation, Rolipram. Likewise, AT2 signal transduction was studied with the AT2 agonist, CGP42112A, plus either 1) a cAMP synthesis inhibitor, dideoxyadenosine, or 2) an inhibitor of cGMP degradation, Zaprinast. L, values are represented as mean +/- SEM x10(-7) cm/s/cm. H2O. For each group n = 6.Results. Inhibition of cGMP synthesis blunted the permeability-increasing effect of AT1 agonism and decreased the peak L-p from 4.91 +/- 0.25 to 2.30 +/- 0.10 (P < 0.001). Inhibition of cAMP degradation also reduced the effect of AT1 agonism. on peak L-p from 2.25 +/- 0.22 to 1.30 +/- 0.13 (P < 0.001). Meanwhile, cAMP synthesis inhibition completely blocked the permeability-decreasing effect of AT2 agonism during which L-p increased from a baseline of 0.92 +/- 0.08 to a peak of 4.38 +/- 0.20 (P < 0.001). During inhibition of cGMP degradation, AT2 activation was able to decrease peak L-p from 2.26 +/- 0.15 to 1.46 +/- 0.05 (P < 0.001).Conclusions. When cGMP synthesis and cAMP degradation were inhibited, the effect on fluid leak by AT1 activation was blunted. Inhibition of cAMP synthesis completely blocked the effect of AT2 activation on fluid leak, while AT2 activation continued to decrease fluid leak despite inhibition of cGMP degradation. The AT1 receptor appears to increase fluid leak by stimulating both cGMP synthesis and cAMP degradation, while the AT2 receptor decreases fluid leak by stimulating cAMP synthesis, but not cGMP degradation. (c) 2005 Elsevier Inc. All rights reserved.

Introduction: Intravascular volume loss from ischemia-reperfusion injury is a major clinical concern. We hypothesize that angiotensin II influences the ischemia-reperfusion-associated microvascular fluid leak through cyclic nucleotide second messenger signal transduction mechanisms. The purposes are to determine hydraulic permeability after ischemia-reperfusion of venules treated with 1) angiotensin II, 2) a cAMP synthesis inhibitor, 3) a cGMP inhibitor, and 4) simultaneous administration of angiotensin II and either a cAMP synthesis inhibitor or a cGMP synthesis inhibitor. Methods: Rat mesenteric postcapillary venules were micro-cannulated to measure hydraulic permeability (Lp). Ischemia-reperfusion was achieved by placing animals in a 5% oxygen environment and preventing venular flow followed by allowing blood flow to resume. Lp was measured after ischemia-reperfusion and treatment with 1) angiotensin II (20nM), 2) cAMP synthesis inhibitor (DDA,10uM), 3) cGMP synthesis inhibitor (LY83583, 10uM), and 4) angiotensin II plus either cAMP inhibition or cGMP inhibition, (n=6 in each group). Results: Compared to the 7-fold increase in Lp due to ischemia-reperfusion alone: 1) angiotensin II attenuated the 7-fold increase by 50% (p<0.001), 2) cAMP inhibition attenuated the 7-fold increase by 45% (p<0.001), 3) cGMP inhibition completed blocked any elevation in Lp due to ischemia-reperfusion (p<0.001), and 4) angiotensin II + cAMP inhibition was not statistically different from angiotensin II alone (p=0.16) while angiotensin II + cGMP inhibition attenuated the 7-fold increase in Lp due to ischemia-reperfusion by 65% (p<0.001). Conclusion: Treatment with angiotensin II attenuated increases in hydraulic permeability due to ischemia-reperfusion by 50%. Inhibition of cGMP synthesis completely blocked any increase in permeability due to ischemia-reperfusion while cAMP inhibition appears to play a lesser role. This emphasizes the major impact that cyclic nucleotide second messengers play in ischemia-reperfusion. A better understanding of mediators that reduce intravascular fluid loss from IR-induced microvascular dysfunction may help clinicians treat uncontrolled fluid extravasation that occurs during shock and sepsis.

Introduction. Surgical resident stress includes psychological and physiological components which relate linearly to heart rate (HR), oxygen consumption (VO2), and neutrophil demargination. The purposes of this series of experiments were (1) To relate HR to VO2 in surgical residents during exercise; (2) to monitor HR as a measure of stress on call; (3) to relate maximum HR on call by surgical resident training level; and (4) to monitor white blood cell (WBC) count as a measure of stress during call. Methods. HR and VO2 were monitored in surgeons (n = 5) during bicycle ergometry. HR was continuously monitored (Holter) for 24 h on call for interns (n = 6), and junior (n = 5) and chief residents (n = 5). WBC counts were obtained from residents off and on call (n = 6). Results. HR (72 ± 5 to 124 ± 4 BPM) correlates with VO2 (273 ± 24 to 1535 ± 103 mlO2/min) R2 = 0.843. Control maximal HR was 110 ± 3. Compared to controls, on call maximal HR was elevated for interns and junior residents to 149 ± 6 (P = 0.0003) and 136 ± 6 (P = 0.009), respectively, but was unchanged in chief residents at 116 ± 3 (P = 0.5). There were no 1-h time periods during which the HR was above 120 bpm in controls. This number of 1-h time periods increased to 7 ± 1 in the interns (P = 0.01) and 6 ± 3 in the junior residents (P = 0.03), but was unchanged in senior residents, 0.4 ± 0.2 (P = 0.8). WBC increased from 5.7 ± 0.4 to on call values of 7.2 ± 0.6 (p = 0.04). Neutrophils decreased from 58 to 49% (P = 0.005). This was offset by an increase in lymphocytes from 33 to 40% (P = 0.009). Conclusion. We conclude that HR correlates with VO2 as an objective measure of stress. Surgical residents achieve stress levels of tachycardia during on-call periods that inversely reflect the training level of the residents. Phenotypic change was documented as an increase in leukocyte count. The stress of being “on call” is substantial enough to provoke measurable physiologic and phenotypic changes in surgery residents.

Editor: A 66-year-old man with severe comorbidities underwent open abdominal aortic aneurysm repair. The patient had a complicated postoperative course with respiratory failure eventually requiring a tracheostomy. Seven days after placement of a right subclavian central venous catheter (Cordis, Miami Lakes, FL) the patient developed severe respiratory distress. Fiberoptic bronchoscopy revealed extraluminal compression of the retrosternal trachea requiring passage of a 6.0-mm endotracheal tube through the tracheostomy. Computed tomography of the thorax demonstrated a right subclavian pseudoaneurysm extending into the mediastinum and compressing the trachea. An angiogram confirmed a large subclavian pseudoaneurysm at the level of the origin of the right vertebral artery. As a result of the patient's high surgical risk and history of median sternotomy, the traditional open operative repair, which would require another thoracotomy for proximal control, was not selected. Instead, endovascular repair with a covered stent was considered. However, the close proximity of the vertebral artery origin prohibited immediate intervention. To protect the vertebral artery from being occluded in the planned implantation of a covered stent, the origin of the right vertebral artery from the subclavian artery was transposed approximately 3 cm distal to the pseudoaneurysm neck. After ligation of the vertebral artery stump, a polytetrafluoroethylene graft from the transposed distal vertebral artery origin was anastomosed to the distal end of the vertebral artery with use of a standard supraclavicular approach (Figure, part a). This transposition allowed for the subsequent placement (at postoperative day 7) of a 4-cmlong Fluency self expanding polytetrafluoroethylene nitinolcovered stent (CR Bard, Murray Hill, NJ) between the origins of the right carotid artery and the bypass graft. From a left common femoral artery access, the right common carotid artery was initially catheterized with a 5-F Davis catheter (Merit Medical, South Jordan, UT) and 0.035-inch Bentson wire (Cook, Bloomington, IN) with subsequent wire removal and catheter connection to a pressurized drip to mark the right internal carotid artery position for subsequent covered stent deployment and to avoid inadvertent coverage of its origin. The right brachial artery was subsequently accessed and the 10-mm × 40-mm stent was then deployed to cover the pseudoaneurysm neck. On angiography at the conclusion of the procedure, there was successful exclusion of the pseudoaneurysm from the arterial circulation without compromising flow to the right vertebral or right carotid arteries (Figure, part b). Five days after stent implantation, a right anterior lateral thoracotomy was performed to drain the residual mediastinal hematoma that had caused marked narrowing of the trachea. The patient underwent successful extubation on postoperative day 4. The patient died in an automobile accident 5 months after the initial transposition procedure. Iatrogenic subclavian artery pseudoaneurysms are a known complication of subclavian or internal jugular central venous catheter placement (1Mansfield PF Hohn DC Fornage BD et al.Complications and failures of subclavian-vein catheterization.N Engl J Med. 1994; 331: 1735-1738Crossref PubMed Scopus (711) Google Scholar). Because of the potential expansion and mass effect of a subclavian artery pseudoaneurysm on adjacent structures, as well as the potential for embolic events, pseudoaneurysms of the subclavian artery are routinely repaired. Traditionally, such injuries are repaired with use of open surgical approaches. However, significant morbidity and mortality is associated with the open techniques of pseudoaneurysm repair. A large series of covered stent–treated arterial lesions was reported by Parodi et al (2Parodi JC Schonholz C Ferreira LM et al.Endovascular stentgraft treatment of traumatic arterial lesions.Ann Vasc Surg. 1999; 13: 121-129Abstract Full Text PDF PubMed Scopus (226) Google Scholar) in 1999 that included 29 cases of traumatic false aneurysms or arteriovenous fistulas (of which nine involved the subclavian artery). Patients were followed for a mean of 24 months and 96% had immediate successful results. With a history of coronary artery bypass grafting adding to an already difficult surgical procedure in this case, we chose an interdisciplinary approach for treatment. The anatomic proximity of the right vertebral artery origin to the neck of the pseudoaneurysm (ie, directly opposite) would have resulted in vertebral artery origin occlusion by the covered stent (Figure, part a). A vertebral artery origin transposition from a supraclavicular approach protected the vertebral artery from potential occlusion during covered stent placement for the pseudoaneurysm and allowed us to take advantage of the endovascular approach, avoiding a median sternotomy. Without transposition, we would have risked vertebral artery occlusion or incomplete coverage of the pseudoaneurysm neck, as described by Watelet et al (3Watelet J Clavier E Reix T et al.Traumatic subclavian artery pseudoaneurysm: periprocedural salvage of failed stent-graft exclusion using coil embolization.J Endovasc Ther. 2001; 8: 197-201Crossref PubMed Scopus (19) Google Scholar). Additional salvage procedures such as coil embolization of the pseudoaneurysm may be required (3Watelet J Clavier E Reix T et al.Traumatic subclavian artery pseudoaneurysm: periprocedural salvage of failed stent-graft exclusion using coil embolization.J Endovasc Ther. 2001; 8: 197-201Crossref PubMed Scopus (19) Google Scholar). A transbrachial approach, instead of a femoral approach, was used for covered stent deployment in our case to provide a more direct access route to the pseudoaneurysm neck, as described by Patel et al (4Patel AV Marin ML Veith FJ et al.Endovascular graft repair of penetrating subclavian artery injuries.J Endovasc Surg. 1996; 3: 382-388Crossref PubMed Scopus (137) Google Scholar). In our experience, the transbrachial approach is safe, but we believe it is prudent to perform surgical closure of the brachial artery puncture site for sheath sizes greater than 7 F, as in our case. Other minimally invasive options include placement of an uncovered stent with wide interstices (eg, Symphony stent; Boston Scientific, Natick, MA) with subsequent coil embolization through the interstices. Risk of this procedure include inability to deliver the coils accurately, requiring additional interventions. Another minimally invasive option is inflation of occlusion balloon across the aneurysm neck and subsequent percutaneous thrombin injection of the pseudoaneurysm (5Criado E Gasparis A Transluminal thrombin injection and exclusion of a paramesenteric abdominal aortic aneurysm.J Vasc Surg. 2004; 39: 1118-1121Abstract Full Text Full Text PDF PubMed Scopus (9) Google Scholar). Thrombin "escape" through the aneurysm neck and embolization into the supraaortic branches would increase the risk of procedure-induced stroke. To our knowledge, long-term studies are not currently available comparing the various minimally invasive approaches.

Secretory phospholipase A2 (sPLA2) type IIa, elevated in inflammation, breaks down membrane phospholipids and generates arachidonic acid. We hypothesized that sPLA2 will hydrolyze red blood cells that expose phosphatidylserine (PS) and generate lysophosphatidic acid (LPA) from phosphatidic acid that is elevated in PS-exposing red blood cells. In turn, LPA, a powerful lipid mediator, could affect vascular endothelial cell function. Although normal red blood cells were not affected by sPLA2, at levels of sPLA2 observed under inflammatory conditions (100 ng/ml) PS-exposing red blood cells hemolyzed and generated LPA (1.2 nm/108 RBC). When endothelial cell monolayers were incubated in vitro with LPA, a loss of confluence was noted. Moreover, a dose-dependent increase in hydraulic conductivity was identified in rat mesenteric venules in vivo with 5 μm LPA, and the combination of PS-exposing red blood cells with PLA2 caused a similar increase in permeability. In the presence of N-palmitoyl l-serine phosphoric acid, a competitive inhibitor for the endothelial LPA receptor, loss of confluence in vitro and the hydraulic permeability caused by 5 μm LPA in vivo were abolished. The present study demonstrates that increased sPLA2 activity in inflammation in the presence of cells that have lost their membrane phospholipid asymmetry can lead to LPA-mediated endothelial dysfunction and loss of vascular integrity.

BACKGROUND Endothelin-1 (ET-1) is a potent vasoconstrictor that is released during shock and sepsis. We hypothesized that ET-1 plays a role in the modulation of the elevated microvascular permeability state of the activated endothelium. METHODS Hydraulic permeability (Lp) was measured using the modified Landis micro-occlusion technique. The effect of different ET-1 doses on Lp was determined by obtaining paired measures of Lp at baseline and after the vessels were perfused with ET-1 at doses of 2.0 pg/mL (n = 6), 20 pg/mL (n = 6), 200 pg/mL (n = 6), or 2,000 pg/mL (n = 6). To evaluate the effects of ET-1 in the activated endothelium, additional vessels were perfused with either 10 micromol/L adenosine triphosphate (ATP) (n = 6) or 1 nmol/L bradykinin (n = 6). The vessels were then perfused with 200 pg/mL ET-1 followed by the final L determination. RESULTS ET-1 significantly decreased Lp at doses of 20 pg/mL (p = 0.03), 200 pg/mL (p = 0.03), and 2,000 pg/mL (p = 0.01). Endothelial activation with ATP and bradykinin increased Lp to 4.21 +/- 0.39 (p < 0.0001) and 2.72 +/- 0.24 (p = 0.001), respectively. ET-1 significantly decreased the Lp to 1.99 +/- 0.48 after activation with ATP (p = 0.004). ET-1 also decreased the Lp to 1.10 +/- 0.19 after activation with bradykinin (p = 0.001). Units for Lp are x10(-7) cm x s(-1) x cm H2O(-1). CONCLUSION In this model, ET-1 attenuated the increase in microvascular permeability that can be seen in inflamed vessels. In addition to its vasopressor function, ET-1 may be of benefit in pathophysiologic states by decreasing third-space fluid loss. This receptor-mediated function of ET-1 may be amenable to pharmacologic manipulation.