The bio-sonographic index. A novel modality for early detection of acute kidney injury after complex vascular surgery. A protocol for an exploratory prospective study.

OBJECTIVE: Acute kidney injury (AKI) is a common complication of complex aortic surgery with high mortality, morbidity and health care expense. The current definition of AKI does not allow for structural characterization of the kidneys and utilizes functional indices with substantial limitations leading to delayed diagnosis and ineffective interventions. The aim of this study is to develop a method of early detection of structural renal abnormalities that can precede and predict the occurrence of AKI in this population. We propose a novel combined index of ultrasonography (shear wave elastography), biomarkers of renal stress (urinary insulin growth factor binding protein-7, IGFBP-7 and inhibitor of tissue metalloproteinase-2, TIMP-2) and renal injury markers (urinary neutrophil gelatinase-associated lipocalin -NGAL)- the bio-sonographic index (BSI). METHODS: A prospective observational study at a tertiary referral center will be performed enrolling 80 patients undergoing elective open and endovascular repair of the visceral aorta. The BSI will be evaluated at baseline, and at 6 and 24 hours after the procedure. The primary outcome is the occurrence of AKI according to the Kidney Disease Improving Global Outcomes (KDIGO) criteria. Each patient will be his/her own control. A reference group of 15 healthy volunteers who are not undergoing interventions will be enrolled to test the feasibility of and to refine the novel SWE protocol. The BSI will be tested for its predictability of the occurrence of AKI. Comparisons will be made between individual and combined components of the BSI and traditional markers used in the KDIGO definition; serum creatinine and urine output in terms of baseline status of the kidney. Correlations will be made between the BSI and conventional indices of AKI and exploratory analyses will be conducted to identify individual disease patterns using the BSI. DISCUSSION: We hypothesize that the BSI will be a sensitive index of early structural abnormalities that precede and predict the occurrence of AKI as defined by KDIGO in complex vascular surgery. TRIAL REGISTRATION: ClinicalTrials.gov NCT04144894. Registered 1/6/2020.

Increased platelet:RBC ratios are associated with improved survival after massive transfusion.

BACKGROUND: Several recent military and civilian trauma studies demonstrate that improved outcomes are associated with early and increased use of plasma-based resuscitation strategies. However, outcomes associated with platelet transfusions are poorly characterized. We hypothesized that increased platelet:red blood cells (RBC) ratios would decrease hemorrhagic death and improve survival after massive transfusion (MT). METHODS: A transfusion database of patients transported from the scene to 22 Level I Trauma Centers over 12 months in 2005 to 2006 was reviewed. MT was defined as receiving ≥ 10 RBC units within 24 hours of admission. To mitigate survival bias, 25 patients who died within 60 minutes of arrival were excluded from analysis. Six random donor platelet units were considered equal to a single apheresis platelet unit. Admission and outcome data associated with the low (>1:20), medium (1:2), and high (1:1) platelet:RBC ratios were examined. These groups were based on the median value of the tertiles for the ratio of platelets:RBC units. RESULTS: Two thousand three hundred twelve patients received at least one unit of blood and 643 received an MT. Admission vital signs, INR, temperature, pH, Glasgow Coma Scale, Injury Severity Score, and age were similar between platelet ratio groups. The average admission platelet counts were lower in the patients who received the high platelet:RBC ratio versus the low ratio (192 vs. 216, p = 0.03). Patients who received MT were severely injured, with a mean (± standard deviation) Injury Severity Score of 33 ± 16 and received 22 ± 15 RBCs and 11 ± 14 platelets within 24 hours of injury. Increased platelet ratios were associated with improved survival at 24 hours and 30 days (p < 0.001 for both). Truncal hemorrhage as a cause of death was decreased (low: 67%, medium: 60%, high: 47%, p = 0.04). Multiple organ failure mortality was increased (low: 7%, medium: 16%, high: 27%, p = 0.003), but overall 30-day survival was improved (low: 52%, medium: 57%, high: 70%) in the high ratio group (medium vs. high: p = 0.008; low vs. high: p = 0.007). CONCLUSION: Similar to recently published military data, transfusion of platelet:RBC ratios of 1:1 was associated with improved early and late survival, decreased hemorrhagic death and a concomitant increase in multiple organ failure-related mortality. Based on this large retrospective study, increased and early use of platelets may be justified, pending the results of prospective randomized transfusion data.

High ratios of plasma and platelets to packed red blood cells do not affect mortality in nonmassively transfused patients.

BACKGROUND: Administration of high transfusion ratios in patients not requiring massive transfusion might be harmful. We aimed to determine the effect of high ratios of fresh frozen plasma (FFP) and platelets (PLT) to packed red blood cells (PRBC) in nonmassively transfused patients. METHODS: Records of 1,788 transfused trauma patients who received <10 units of PRBC in 24 hours at 23 United States Level I trauma centers were reviewed. The relationship between ratio category (low and high) and in-hospital mortality was assessed with propensity-adjusted multivariate proportional hazards models. RESULTS: At baseline, patients transfused with a high FFP:PRBC ratio were younger, had a lower Glasgow Coma Scale score, and a higher Injury Severity Score. Those receiving a high PLT:PRBC ratio were older. The risk of in-hospital mortality did not vary significantly with FFP:PRBC ratio category. Intensive care unit (ICU)-free days, hospital-free days, and ventilator-free days did not vary significantly with FFP:PRBC ratio category. ICU-free days and ventilator-free days were significantly decreased among patients in the high (≥1:1) PLT:PRBC category, and hospital-free days did not vary significantly with PLT:PRBC ratio category. The analysis was repeated using 1:2 as the cutoff for high and low ratios. Using this cutoff, there was still no difference in mortality with either FFP:PRBC ratios or platelet:PRBC ratios. However, patients receiving a >1:2 ratio of FFP:PRBCs or a >1:2 ratio PLT:PRBCs had significantly decreased ICU-free days and ventilator-free days. CONCLUSIONS: FFP:PRBC and PLT:PRBC ratios were not associated with in-hospital mortality. Depending on the threshold analyzed, a high ratio of FFP:PRBC and PLT:PRBC transfusion was associated with fewer ICU-free days and fewer ventilator-free days, suggesting that the damage control infusion of FFP and PLT may cause increased morbidity in nonmassively transfused patients and should be rapidly terminated when it becomes clear that a massive transfusion will not be required.

A normal platelet count may not be enough: the impact of admission platelet count on mortality and transfusion in severely injured trauma patients.

BACKGROUND: Platelets play a central role in hemostasis after trauma. However, the platelet count of most trauma patients does not fall below the normal range (100-450 × 10(9)/L), and as a result, admission platelet count has not been adequately investigated as a predictor of outcome. The purpose of this study was to examine the relationship between admission platelet count and outcomes after trauma. METHODS: A retrospective cohort study of 389 massively transfused trauma patients. Regression methods and the Kruskal-Wallis test were used to test the association between admission platelet count and 24-hour mortality and units of packed red blood cells (PRBCs) transfused. RESULTS: For every 50 × 10(9)/L increase in admission platelet count, the odds of death decreased 17% at 6 hours (p = 0.03; 95% confidence interval [CI], 0.70-0.99) and 14% at 24 hours (p = 0.02; 95% CI, 0.75-0.98). The probability of death at 24 hours decreased with increasing platelet count. For every 50 × 10(9)/L increase in platelet count, patients received 0.7 fewer units of blood within the first 6 hours (p = 0.01; 95% CI, -1.3 to -0.14) and one less unit of blood within the first 24 hours (p = 0.002; 95% CI, -1.6 to -0.36). The mean number of units of PRBCs transfused within the first 6 hours and 24 hours decreased with increasing platelet count. CONCLUSIONS: Admission platelet count was inversely correlated with 24-hour mortality and transfusion of PRBCs. A normal platelet count may be insufficient after severe trauma, and as a result, these patients may benefit from a lower platelet transfusion threshold. Future studies of platelet number and function after injury are needed.

The association of blood component use ratios with the survival of massively transfused trauma patients with and without severe brain injury.

BACKGROUND: The effect of blood component ratios on the survival of patients with traumatic brain injury (TBI) has not been studied. METHODS: A database of patients transfused in the first 24 hours after admission for injury from 22 Level I trauma centers over an 18-month period was queried to find patients who (1) met different definitions of massive transfusion (5 units red blood cell [RBC] in 6 hours vs. 10 units RBC in 24 hours), (2) received high or low ratios of platelets or plasma to RBC units (<1:2 vs. ≥ 1:2), and (3) had severe TBI (head abbreviated injury score ≥ 3) (TBI+). RESULTS: Of 2,312 total patients, 850 patients were transfused with ≥ 5 RBC units in 6 hours and 807 could be classified into TBI+ (n = 281) or TBI- (n = 526). Six hundred forty-three patients were transfused with ≥ 10 RBC units in 24 hours with 622 classified into TBI+ (n = 220) and TBI- (n = 402). For both high-risk populations, a high ratio of platelets:RBCs (not plasma) was independently associated with improved 30-day survival for patients with TBI+ and a high ratio of plasma:RBCs (not platelets) was independently associated with improved 30-day survival in TBI- patients. CONCLUSIONS: High platelet ratio was associated with improved survival in TBI+ patients while a high plasma ratio was associated with improved survival in TBI- patients. Prospective studies of blood product ratios should include TBI in the analysis for determination of optimal use of ratios on outcome in injured patients.

Effect of high product ratio massive transfusion on mortality in blunt and penetrating trauma patients.

BACKGROUND: Recent data suggest that massively transfused patients have lower mortality rates when high ratios (>1:2) of plasma or platelets to red blood cells (RBCs) are used. Blunt and penetrating trauma patients have different injury patterns and may respond differently to resuscitation. This study was performed to determine whether mortality after high product ratio massive transfusion is different in blunt and penetrating trauma patients. METHODS: Patients receiving 10 or more units of RBCs in the first 24 hours after admission to one of 23 Level I trauma centers were analyzed. Baseline physiologic and biochemical data were obtained. Univariate and logistic regression analyses were performed. Adjusted mortality in patients receiving high (≥ 1:2) and low (<1:2) ratios of plasma or platelets to RBCs was calculated for blunt and penetrating trauma patients. RESULTS: The cohort contained 703 patients. Blunt injury patients receiving a high ratio of plasma or platelets to RBCs had lower 24-hour mortality (22% vs. 31% for plasma, p = 0.007; 20% vs. 30% for platelets, p = 0.032), but there was no difference in 30-day mortality (40% vs. 44% for plasma, p = 0.085; 37% vs. 44% for platelets, p = 0.063). Patients with penetrating injuries receiving a high plasma:RBC ratio had lower 24-hour mortality (21% vs. 37%, p = 0.005) and 30-day mortality (29% vs. 45%, p = 0.005). High platelet:RBC ratios did not affect mortality in penetrating patients. CONCLUSION: Use of high plasma:RBC ratios during massive transfusion may benefit penetrating trauma patients to a greater degree than blunt trauma patients. High platelet:RBC ratios did not benefit either group.

A high fresh frozen plasma: packed red blood cell transfusion ratio decreases mortality in all massively transfused trauma patients regardless of admission international normalized ratio.

BACKGROUND: Coagulopathy is present in 25% to 38% of trauma patients on arrival to the hospital, and these patients are four times more likely to die than trauma patients without coagulopathy. Recently, a high ratio of fresh frozen plasma (FFP) to packed red blood cells (PRBCs) has been shown to decrease mortality in massively transfused trauma patients. Therefore, we hypothesized that patients with elevated International Normalized Ratio (INR) on arrival to the hospital may benefit more from transfusion with a high ratio of FFP:PRBC than those with a lower INR. METHODS: Retrospective multicenter cohort study of 437 massively transfused trauma patients was conducted to determine whether the effect of the ratio of FFP:PRBC on death at 24 hours is modified by a patient's admission INR on arrival to the hospital. Contingency tables and logistic regression were used. RESULTS: Trauma patients who arrived to the hospital with an elevated INR had a greater risk of death than those with a lower INR. However, as the ratio of FFP:PRBC transfused increased, mortality decreased similarly between the INR quartiles. CONCLUSIONS: The mortality benefit from a high FFP:PRBC ratio is similar for all massively transfused trauma patients. This is contrary to the current belief that only coagulopathic trauma patients benefit from a high FFP:PRBC ratio. Furthermore, it is unnecessary to determine whether INR is elevated before transfusing a high FFP:PRBC ratio. Future studies are needed to determine the mechanism by which a high FFP:PRBC ratio decreases mortality in all massively transfused trauma patients.

Profoundly abnormal initial physiologic and biochemical data cannot be used to determine futility in massively transfused trauma patients.

BACKGROUND: Improvements in prehospital care and resuscitation have led to increases in the number of severely injured patients who are salvageable. Massive transfusion has been increasingly used. Patients often present with markedly abnormal physiologic and biochemical data. The purpose of this study was to identify objective data that can be used to identify clinical futility in massively transfused trauma patients to allow for early termination of resuscitative efforts. METHODS: A multicenter database was used. Initial physiologic and biochemical data were obtained, and mortality was determined for patients in the 5th and 10th percentiles for each variable. Raw data from the extreme outliers for each variable were also examined to determine whether a point of excessive mortality could be identified. Injury scoring data were also analyzed. A classification tree model was used to look for variable combinations that predict clinical futility. RESULTS: The cohort included 704 patients. Overall mortality was 40.2%. The highest mortality rates were seen in patients in the 10th percentile for lactate (77%) and pH (72%). Survivors at the extreme ends of the distribution curves for each variable were not uncommon. The classification tree analysis failed to identify any biochemical and physiologic variable combination predictive of >90% mortality. Patients older than 65 years with severe head injuries had 100% mortality. CONCLUSION: Consideration should be given to withholding massive transfusion for patients older than 65 years with severe head injuries. Otherwise we did not identify any objective variables that reliably predict clinical futility in individual cases. Significant survival rates can be expected even in patients with profoundly abnormal physiologic and biochemical data.

A predictive model for mortality in massively transfused trauma patients.

BACKGROUND: Improvements in trauma systems and resuscitation have increased survival in severely injured patients. Massive transfusion has been increasingly used in the civilian setting. Objective predictors of mortality have not been well described. This study examined data available in the early postinjury period to identify variables that are predictive of 24-hour- and 30-day mortality in massively transfused trauma patients. METHODS: Massively transfused trauma patients from 23 Level I centers were studied. Variables available on patient arrival that were predictive of mortality at 24 hours were entered into a logistic regression model. A second model was created adding data available 6 hours after injury. A third model evaluated mortality at 30 days. Receiver operating characteristic curves and the Hosmer-Lemeshow test were used to assess model quality. RESULTS: Seven hundred four massively transfused patients were analyzed. The model best able to predict 24-hour mortality included pH, Glasgow Coma Scale score, and heart rate, with an area under the receiver operating characteristic curve (AUROC) of 0.747. Addition of the 6-hour red blood cell requirement increased the AUROC to 0.769. The model best able to predict 30-day mortality included the above variables plus age and Injury Severity Score with an AUROC of 0.828. CONCLUSION: Glasgow Coma Scale score, pH, heart rate, age, Injury Severity Score, and 6-hour red blood cell transfusion requirement independently predict mortality in massively transfused trauma patients. Models incorporating these data have only a modest ability to predict mortality and should not be used to justify withholding massive transfusion in individual cases.

Gender-based differences in mortality in response to high product ratio massive transfusion.

BACKGROUND: Recent data suggest that patients undergoing massive transfusion have lower mortality rates when ratios of plasma and platelets to red blood cells (RBCs) of ≥ 1:2 are used. This has not been examined independently in women and men. A gender dichotomy in outcome after severe injury is known to exist. This study examined gender-related differences in mortality after high product ratio massive transfusion. METHODS: A retrospective study was conducted using a database containing massively transfused trauma patients from 23 Level I trauma centers. Baseline demographic, physiologic, and biochemical data were obtained. Univariate and logistic regression analyses were performed. Adjusted mortality in patients receiving high (≥ 1:2) or low (<1:2) ratios of plasma or platelets to RBCs was compared in women and men independently. RESULTS: Seven hundred four patients were analyzed. In males, mortality was lower for patients receiving a high plasma:RBC ratio at 24 hours (20.6% vs. 33.0% for low ratio, p = 0.005) and at 30 days (34.9% vs. 42.8%, p = 0.032). Males receiving a high platelet:RBC ratio also had lower 24-hour mortality (17.6% vs. 31.5%, p = 0.004) and 30-day mortality (32.1% vs. 42.2%, p = 0.045). Females receiving high ratios of plasma or platelets to RBCs had no improvement in 24-hour mortality (p = 0.119 and 0.329, respectively) or 30-day mortality (p = 0.199 and 0.911, respectively). Use of high product ratio transfusions did not affect 24-hour RBC requirements in males or females. CONCLUSION: Use of high plasma:RBC or platelet:RBC ratios in massive transfusion may benefit men more than women. This may be due to gender-related differences in coagulability. Further study is needed to determine whether separate protocols for women and men should be established.

Crystalloid resuscitation improves survival in trauma patients receiving low ratios of fresh frozen plasma to packed red blood cells.

BACKGROUND: Current trauma resuscitation guidelines recommend giving an initial crystalloid bolus as first line for resuscitation. Recent studies have shown a survival benefit for trauma patients resuscitated with high ratios of fresh frozen plasma (FFP) to packed red blood cells (PRBC). Our aim was to determine whether the volume of crystalloid given during resuscitation correlated with differences in morbidity or mortality based on the ratio of FFP:PRBC given. METHODS: This was a retrospective review of 2,473 transfused trauma patients at 23 Level I trauma centers from July 2005 to October 2007. Patients were separated based on the ratios of FFP:PRBC they received (<1:4, 1:4-1:1, and >1:1) and then analyzed for morbidity and mortality based on whether or not they received at least 1 L crystalloid for each unit of PRBC. Outcomes analyzed were 6-hour, 24-hour, and 30-day survival as well as intensive care unit (ICU)-free days, ventilator-free days, and hospital-free days. RESULTS: Massive transfusion patients who received <1:4 ratios of FFP:PRBC had significantly improved 6-hour, 24-hour, and 30-day mortality and significantly more ventilator-free days if they received at least 1 L of crystalloid for each unit of PRBC. Nonmassive transfusion patients who received <1:4 ratios of FFP:PRBC had significantly improved 6-hour, 24-hour, and 30-day mortality and significantly more ICU-free days, ventilator-free days, and hospital-free days if they received at least 1 L crystalloid for each unit of PRBC. In both massive and nonmassive transfusion groups, the survival benefit and morbidity benefit was progressively less for the 1:4 to 1:1 FFP:PRBC groups and >1:1 FFP:PRBC groups. CONCLUSIONS: If high ratios of FFP:PRBC are unable to be given to trauma patients, resuscitation with at least 1 L of crystalloid per unit of PRBC is associated with improved overall mortality.

Specific abbreviated injury scale values are responsible for the underestimation of mortality in penetrating trauma patients by the injury severity score.

BACKGROUND: The Injury Severity Score (ISS) is widely used as a method for rating severity of injury. The ISS is the sum of the squares of the three worst Abbreviated Injury Scale (AIS) values from three body regions. Patients with penetrating injuries tend to have higher mortality rates for a given ISS than patients with blunt injuries. This is thought to be secondary to the increased prevalence of multiple severe injuries in the same body region in patients with penetrating injuries, which the ISS does not account for. We hypothesized that the mechanism-based difference in mortality could be attributed to certain ISS ranges and specific AIS values by body region. METHODS: Outcome and injury scoring data were obtained from transfused patients admitted to 23 Level I trauma centers. ISS values were grouped into categories, and a logistic regression model was created. Mortality for each ISS category was determined and compared with the ISS 1 to 15 group. An interaction term was added to evaluate the effect of mechanism. Additional logistic regression models were created to examine each AIS category individually. RESULTS: There were 2,292 patients in the cohort. An overall interaction between ISS and mechanism was observed (p = 0.049). Mortality rates between blunt and penetrating patients with an ISS between 25 and 40 were significantly different (23.6 vs. 36.1%; p = 0.022). Within this range, the magnitude of the difference in mortality was far higher for penetrating patients with head injuries (75% vs. 37% for blunt) than truncal injuries (26% vs. 17% for blunt). Penetrating trauma patients with an AIS head of 4 or 5, AIS abdomen of 3, or AIS extremity of 3 all had adjusted mortality rates higher than blunt trauma patients with those values. CONCLUSION: Significant differences in mortality between blunt and penetrating trauma patients exist at certain ISS and AIS category values. The mortality difference is greatest for head injured patients.

Variations between level I trauma centers in 24-hour mortality in severely injured patients requiring a massive transfusion.

BACKGROUND: Significant differences in outcomes have been demonstrated between Level I trauma centers. Usually these differences are ascribed to regional or administrative differences, although the influence of variation in clinical practice is rarely considered. This study was undertaken to determine whether differences in early mortality of patients receiving a massive transfusion (MT, ≥ 10 units pf RBCs within 24 hours of admission) persist after adjustment for patient and transfusion practice differences. We hypothesized differences among centers in 24-hour mortality could predominantly be accounted for by differences in transfusion practices as well as patient characteristics. METHODS: Data were retrospectively collected over a 1-year period from 15 Level I centers on patients receiving an MT. A purposeful variable selection strategy was used to build the final multivariable logistic model to assess differences between centers in 24-hour mortality. Adjusted odds ratios for each center were calculated. RESULTS: : There were 550 patients evaluated, but only 443 patients had complete data for the set of variables included in the final model. Unadjusted mortality varied considerably across centers, ranging from 10% to 75%. Multivariable logistic regression identified injury severity score (ISS), abbreviated injury scale (AIS) of the chest, admission base deficit, admission heart rate, and total units of RBC transfused, as well as ratios of plasma:RBC and platelet:RBC to be associated with 24-hour mortality. After adjusting for severity of injury and transfusion, treatment variables between center differences were no longer significant. CONCLUSIONS: In the defined population of patients receiving an MT, between-center differences in 24-hour mortality may be accounted for by severity of injury as well as transfusion practices.

Protection from experimental ventilator-induced acute lung injury by IL-1 receptor blockade.

BACKGROUND: Clinical studies have shown that injurious mechanical ventilation is associated with increased airspace and plasma levels of interleukin-1beta (IL-1beta); however, the potential therapeutic value of IL-1 inhibition in acute lung injury has not been thoroughly investigated. A study was undertaken to determine if IL-1 signalling is a necessary early event in the pathogenesis of experimental ventilator-induced lung injury. METHODS: Mice deficient in IL-1 receptor type 1 (IL1R1) and rats treated with IL-1 receptor antagonist (IL-1Ra) were mechanically ventilated with high tidal volume (30 ml/kg) and the effect of IL-1 signalling blockade on the severity of lung injury was determined. RESULTS: Permeability, as measured by radiolabelled albumin flux, was significantly lower in IL1R1 null mice than in wild-type mice during injurious ventilation (p<0.05). IL-1Ra significantly decreased protein permeability and pulmonary oedema in rats during injurious ventilation and also decreased airspace and plasma levels of the chemokine CXCL1 and airspace neutrophils. IL-1Ra decreased expression of NOS2 and ICAM-1 mRNA in whole lung. Bronchoalveolar lavage fluid levels of RTI40, a marker of type I cell injury, were 2.5 times lower following IL-1Ra treatment (p<0.05). In isolated type II pneumocytes, IL-1beta reduced electrical resistance and increased transepithelial permeability. CONCLUSIONS: IL-1 contributes to alveolar barrier dysfunction in VILI by promoting lung neutrophil recruitment and by increasing epithelial injury and permeability. Because preserved alveolar barrier function is associated with better outcomes in patients with acute lung injury, these data support further testing of IL-1Ra for the treatment of acute lung injury.

Sevoflurane but not propofol increases interstitial glycolysis metabolites availability during tourniquet-induced ischaemia-reperfusion.

BACKGROUND: Ischaemia/reperfusion (I/R) is one of the main pathophysiological phenomena involved in the anaesthetic practice. The authors hypothesized that anaesthetic regimens can influence skeletal muscle tolerance to tourniquet-induced I/R that should be reflected by the interstitial metabolite levels of anaerobic glycolysis. METHODS: Microdialysis probes were implanted in three groups of 10 patients each receiving either sevoflurane (SEVO), propofol (PRO), or spinal (SA) anaesthesia (for induction and maintenance). SA group was considered as a control group. Interstitial fluid was obtained during tourniquet-induced I/R and was analysed for interstitial glucose, lactate, pyruvate, and glycerol. RESULTS: The microdialysis flow rate was 0.5 microl min(-1). Compared with the control group, the SEVO group had a higher level of both lactate and pyruvate and an increase in glucose during ischaemia. In contrast, the PRO group had a lower level of pyruvate, resulting in a significant higher increase (eight times from baseline) of the lactate pyruvate ratio. Glucose level remained low in this group. During reperfusion, lactate, pyruvate, and glucose remained at a significantly higher level in the SEVO group. In the PRO group, there was no difference in lactate, pyruvate, and glucose levels compared with the control group. The interstitial level of glycerol exhibits only few and comparable changes during I/R between the groups. CONCLUSIONS: Our results indicate that there is a better availability of interstitial glycolysis metabolites (glucose, lactate, and pyruvate) in the skeletal muscle during ischaemia and reperfusion after sevoflurane exposure than after propofol, suggesting a potential preconditioning effect of sevoflurane on tourniquet-induced skeletal muscle I/R.

Activation of the stress protein response prevents the development of pulmonary edema by inhibiting VEGF cell signaling in a model of lung ischemia-reperfusion injury in rats.

Lung endothelial damage is a characteristic morphological feature of ischemia-reperfusion (I/R) injury, although the molecular steps involved in the loss of endothelial integrity are still poorly understood. We tested the hypothesis that the activation of vascular endothelial growth factor (VEGF) cell signaling would be responsible for the increase in lung vascular permeability seen early after the onset of I/R in rats. Furthermore, we hypothesized that the I/R-induced pulmonary edema would be significantly attenuated in rats by the activation of the stress protein response. Pretreatment with Ad Flk-1, an adenovirus encoding for the soluble VEGF receptor type II, prevented I/R-mediated increase in lung vascular permeability in rats. Furthermore, the I/R-induced lung injury was significantly decreased by prior activation of the stress protein response with geldanamycin or pyrrolidine dithiocarbamate. In vitro studies demonstrated that VEGF caused an increase in protein permeability across primary cultures of bovine macro- and microvascular lung endothelial cell monolayers that were associated with a phosphorylation of VE- and E-cadherin and the formation of actin stress fibers. Activation of the stress protein response prevented the VEGF-mediated changes in protein permeability across these cell monolayers and reduced the phosphorylation of VE-and E-cadherins, as well as the formation of actin stress fibers in these cells.

HO-1 induction restores c-AMP-dependent lung epithelial fluid transport following severe hemorrhage in rats.

Inhibition of cAMP-dependent stimulation of the vectorial fluid transport across the lung epithelium following hemorrhagic shock is mediated by NO released within the airspaces of the lung. We tested here the hypothesis that prior induction of HO-1 would attenuate the release of NO in the airspaces, thus preventing the inhibition of the c-AMP stimulation of alveolar fluid clearance (ALC) in rats. Indeed, HO-1 induction restored the cAMP-mediated up-regulation of ALC after hemorrhage by decreasing NO released within the airspaces of the lung. In vitro studies demonstrated that HO-1 induction significantly reduced the iNOS-mediated release of NO by alveolar macrophages stimulated with endotoxin for 24 h. This effect is explained in part by a HO-1-dependent attenuation of the LPS-mediated nuclear translocation of NF-kappaB. In addition, HO-1 induction also significantly reduced the iNOS-mediated release of NO by MH-S cells that were stimulated with interferon-gamma by decreasing the phosphorylation of STAT 1, another transcription factor important for the activation of the iNOS promoter. In contrast, HO-1 induction did not affect the production of NO by rat alveolar epithelial type II cells that were stimulated with cytomix (a mixture of TNF-alpha, IL-1beta, and IFN-gamma) for 24 h. In summary, these results provide the first in vivo evidence that the induction of HO-1 in the lung restores a normal fluid transport capacity of the alveolar epithelium following hemorrhagic shock by inhibiting the iNOS-mediated release of NO by alveolar macrophages.

Standard preoxygenation technique versus two rapid techniques in pregnant patients.

The aim of this study was to compare three different preoxygenation techniques in pregnant women by measuring end-tidal fractional oxygen concentration (FETO2): the traditional technique of 3min tidal volume breathing (VT x 3 min), 8 deep breaths (8 DB) and 4 deep breaths (4 DB). Twenty pregnant volunteers without pulmonary diseases were studied during the third trimester (36-38 weeks' gestation). Women were preoxygentated using a non-rebreathing respiratory circuit with a 3-L reservoir bag and a Capnomac Ultima calibrated before each patient to monitor FETO2 continuously. The three preoxygenation techniques were investigated in random order: VT x 3 min using an oxygen flow of 9 L min-1, 4 DB within 30s using an oxygen flow of 9 L min-1, and 8 DB within one minute using an oxygen flow of 15 L min-1. Between each technique, 5-min room air breathing was allowed to return to baseline FETO2 assessed by the Capnomac Ultima. An FETO2 >/= 90% was achieved more frequently with the VT x 3 min and the 8 DB techniques (76%) than with the 4 DB technique (18%) (P < 0.05). The average time required for obtaining an FETO2 >/= 90% was 107+/-37s. Both the VT x 3 min and the 8 DB techniques are therefore more effective for preoxygenation in pregnant patients than the 4 DB technique. In an acute obstetric emergency before rapid-sequence induction of general anaesthesia, 8 DB preoxygenation technique could be recommended.

Stress preconditioning attenuates oxidative injury to the alveolar epithelium of the lung following haemorrhage in rats.

Inhibition of cAMP-dependent stimulation of vectorial fluid transport across the alveolar epithelium following haemorrhagic shock is mediated by reactive nitrogen species released within the airspaces of the lung. We tested here the hypothesis that the prior activation of the cellular heat shock or stress response, via exposure to either heat or geldanamycin, would attenuate the release of airspace nitric oxide (NO) responsible for the shock-mediated failure of the alveolar epithelium to respond to catecholamines in rats. Rats were haemorrhaged to a mean arterial pressure of 30-35 mmHg for 60 min, and then resuscitated with a 4 % albumin solution. Alveolar fluid clearance was measured by change in concentration of a protein solution instilled into the airspaces 5 h after the onset of haemorrhage. Stress preconditioning restored the cAMP-mediated upregulation of alveolar liquid clearance after haemorrhage. The protective effect of stress preconditioning was mediated in part by a decrease in the expression of iNOS in the lung. Specifically, stress preconditioning decreased the production of nitrite by endotoxin-stimulated alveolar macrophages removed from haemorrhaged rats or by A549 and rat alveolar epithelial type II cell monolayers stimulated with cytomix (a mixture of TNF-alpha, IL-1beta and IFN-gamma) for 24 h. In summary, these results provide the first in vivo evidence that stress preconditioning restores a normal fluid transport capacity of the alveolar epithelium in the early phase following haemorrhagic shock by attenuating NO-mediated oxidative stress to the lung epithelium.