Improving outcomes for hospital patients with critical bleeding requiring massive transfusion: the Australian and New Zealand Massive Transfusion Registry study methodology.

BACKGROUND: The Australian and New Zealand (ANZ) Massive Transfusion (MT) Registry (MTR) has been established to improve the quality of care of patients with critical bleeding (CB) requiring MT (≥ 5 units red blood cells (RBC) over 4 h). The MTR is providing data to: (1) improve the evidence base for transfusion practice by systematically collecting data on transfusion practice and clinical outcomes; (2) monitor variations in practice and provide an opportunity for benchmarking, and feedback on practice/blood product use; (3) inform blood supply planning, inventory management and development of future clinical trials; and (4) measure and enhance translation of evidence into policy and patient blood management guidelines. The MTR commenced in 2011. At each participating site, all eligible patients aged ≥18 years with CB from any clinical context receiving MT are included using a waived consent model. Patient information and clinical coding, transfusion history, and laboratory test results are extracted for each patient's hospital admission at the episode level. RESULTS: Thirty-two hospitals have enrolled and 3566 MT patients have been identified across Australia and New Zealand between 2011 and 2015. The majority of CB contexts are surgical, followed by trauma and gastrointestinal haemorrhage. Validation studies have verified that the definition of MT used in the registry correctly identifies 94 % of CB events, and that the median time of transfusion for the majority of fresh products is the 'product event issue time' from the hospital blood bank plus 20 min. Data linkage between the MTR and mortality databases in Australia and New Zealand will allow comparisons of risk-adjusted mortality estimates across different bleeding contexts, and between countries. Data extracts will be examined to determine if there are differences in patient outcomes according to transfusion practice. The ratios of blood components (e.g. FFP:RBC) used in different types of critical bleeding will also be investigated. CONCLUSIONS: The MTR is generating data with the potential to have an impact on management and policy decision-making in CB and MT and provide benchmarking and monitoring tools for immediate application.

Endothelial cationic amino acid transporter-1 overexpression can prevent oxidative stress and increases in arterial pressure in response to superoxide dismutase inhibition in mice.

AIM: Oxidative stress may play an important role in the pathogenesis of hypertension. The aim of our study is to examine whether increased expression of the predominant endothelial l-arginine transporter, cationic amino acid transporter-1 (CAT1), can prevent oxidative stress-induced hypertension. METHODS: Wild-type mice (WT; n = 9) and endothelial CAT1 overexpressing (CAT+) mice (n = 6) had telemetry probes implanted for the measurement of mean arterial pressure (MAP), heart rate (HR) and locomotor activity. Minipumps were implanted for infusion of the superoxide dismutase inhibitor diethyldithiocarbamic acid (DETCA; 30 mg kg(-1) day(-1) ; 14 days) or its saline vehicle. Baseline levels of MAP, HR and locomotor activity were determined before and during chronic DETCA administration. Mice were then killed, and their plasma and kidneys collected for analysis of F2 -isoprostane levels. RESULTS: Basal MAP was less in CAT+ (92 ± 2 mmHg; n = 6) than in WT (98 ± 2 mmHg; n = 9; P < 0.001). During DETCA infusion, MAP was increased in WT (by 4.2 ± 0.5%; P < 0.001) but not in CAT+, when compared to appropriate controls (PDETCA*genotype = 0.006). DETCA infusion increased total plasma F2 -isoprostane levels (by 67 ± 11%; P = 0.05) in WT but not in CAT+. Total renal F2 -isoprostane levels were greater during DETCA infusion in WT (by 72%; P < 0.001), but not in CAT+, compared to appropriate controls. CONCLUSION: Augmented endothelial l-arginine transport attenuated the prohypertensive effects of systemic and renal oxidative stress, suggesting that manipulation of endothelial CAT1 may provide a new therapeutic approach for the treatment of cardiovascular disease associated with oxidative stress.

Evidence that renal arginine transport is impaired in spontaneously hypertensive rats.

Low renal nitric oxide (NO) bioavailability contributes to the development and maintenance of chronic hypertension. We investigated whether impaired l-arginine transport contributes to low renal NO bioavailability in hypertension. Responses of renal medullary perfusion and NO concentration to renal arterial infusions of the l-arginine transport inhibitor l-lysine (10 µmol·kg(-1)·min(-1); 30 min) and subsequent superimposition of l-arginine (100 µmol·kg(-1)·min(-1); 30 min), the NO synthase inhibitor N(G)-nitro-l-arginine (2.4 mg/kg; iv bolus), and the NO donor sodium nitroprusside (0.24 µg·kg(-1)·min(-1)) were examined in Sprague-Dawley rats (SD) and spontaneously hypertensive rats (SHR). Renal medullary perfusion and NO concentration were measured by laser-Doppler flowmetry and polarographically, respectively, 5.5 mm below the kidney surface. Renal medullary NO concentration was less in SHR (53 ± 3 nM) compared with SD rats (108 ± 12 nM; P = 0.004). l-Lysine tended to reduce medullary perfusion (-15 ± 7%; P = 0.07) and reduced medullary NO concentration (-9 ± 3%; P = 0.03) while subsequent superimposition of l-arginine reversed these effects of l-lysine in SD rats. In SHR, l-lysine and subsequent superimposition of l-arginine did not significantly alter medullary perfusion or NO concentration. Collectively, these data suggest that renal l-arginine transport is impaired in SHR. Renal l-[(3)H]arginine transport was less in SHR compared with SD rats (P = 0.01). Accordingly, we conclude that impaired arginine transport contributes to low renal NO bioavailability observed in the SHR kidney.

Arginase II inhibition prevents nitrate tolerance.

BACKGROUND AND PURPOSE: Nitrate tolerance, the loss of vascular responsiveness with continued use of nitrates, remains incompletely understood and is a limitation of these therapeutic agents. Vascular superoxide, generated by uncoupled endothelial NOS (eNOS), may play a role. As arginase competes with eNOS for L-arginine and may exacerbate the production of reactive oxygen species (ROS), we hypothesized that arginase inhibition might reduce nitrate tolerance. EXPERIMENTAL APPROACH: Vasodilator responses were measured in aorta from C57Bl/6 and arginase II knockout (argII -/-) mice using myography. Uncoupling of eNOS, determined as eNOS monomer : dimer ratio, was assessed using low-temperature SDS-PAGE and ROS levels were measured using L-012 and lucigenin-enhanced chemiluminescence. KEY RESULTS: Repeated application of glyceryl trinitrate (GTN) on aorta isolated from C57Bl/6 mice produced a 32-fold rightward shift of the concentration-response curve. However this rightward shift (or resultant tolerance) was not observed in the presence of the arginase inhibitor (s)-(2-boronethyl)-L-cysteine HCl (BEC; 100 µM) nor in aorta isolated from argII -/- mice. Similar findings were obtained after inducing nitrate tolerance in vivo. Repeated administration of GTN in human umbilical vein endothelial cells induced uncoupling of eNOS from its dimeric state and increased ROS levels, which were reduced with arginase inhibition and exogenous L-arginine. Aortae from GTN tolerant C57Bl/6 mice exhibited increased arginase activity and ROS production, whereas vessels from argII -/- mice did not. CONCLUSION AND IMPLICATIONS: Arginase II removal prevents nitrate tolerance. This may be due to decreased uncoupling of eNOS and consequent ROS production.

Increased biological oxidation and reduced anti-oxidant enzyme activity in pre-eclamptic placentae.

Oxidative stress occurs when cellular levels of reactive oxygen species exceed anti-oxidant capabilities and has been implicated in the pathogenesis of pre-eclampsia. In this study we have examined the tissue levels of endogenous anti-oxidant proteins (superoxide dismutase, glutathione peroxidase, thioredoxin reductase and thioredoxin) and the level of lipid and protein oxidation in placental samples from normal and pre-eclamptic pregnancies. Pre-eclamptic tissue homogenates demonstrated significantly increased levels of lipid peroxidation (20.68 +/- 7.811 microM protein versus 5.33 +/- 4.03 microM/mg protein, P < 0.001) and a trended increase in protein carbonyl concentration (248.1 +/- 97.71 units/mg protein versus 209.7 +/- 82.6 U/mg protein) when compared to controls. The levels and activities of the anti-oxidant proteins superoxide dismutase (2.48 +/- 0.6 U/mg protein versus 2.02 +/- 0.51 U/mg protein, P <0.02), thioredoxin reductase (19.25 +/- 9.81 U/mg protein versus 13.02 +/- 5.66 U/mg protein,P = 0.02), thioredoxin (107.00 +/- 18.11 ng/mg protein versus 91.12 +/- 21.18 ng/mg protein, P = 0.02) and glutathione peroxidase (17.33 +/- 6.63 mmol/min/mg protein versus 11.50 +/- 3.11 mmol/min/mg, P < 0.02) were all found to be significantly reduced when comparing pre-eclamptic placental tissue homogenates to gestational age-matched control placentae from non-pre-eclamptic pregnancies. The results of this study demonstrate a decreased enzymatic anti-oxidant capacity and increased oxidation in placental tissue from pre-eclamptic women, which may contribute to the pathogenesis of this complex disorder.

Selenium deficiency as a model of experimental pre-eclampsia in rats.

Epidemiological studies and in vitro analysis demonstrate correlations between selenium status and human pre-eclampsia (PET). Selenium is an essential component in the anti-oxidant proteins glutathione peroxidase and thioredoxin reductase, which are produced in lower amounts in pre-eclamptic placenta. This study examined the effect of modulating dietary selenium content in pregnant rats. Rats were fed diets containing no selenium, 239 microg/kg selenium or 1000 microg/kg selenium, four weeks prior to and following conception. Significant pregnancy-specific increases in systolic blood pressure (116.4 +/- 5.2 mmHg vs 108 +/- 6.8 mmHg vs 111.4 +/- 4.7 mmHg) and proteinuria (9.68 +/- 2.12 microg/ml vs 5.93 +/- 1.59 microg/ml vs 4.43 +/- 0.96 microg/ml) were demonstrated in animals fed a selenium free-diet when compared with normal or high selenium diets. Placental weight and pup number were not affected by selenium deprivation, however a significant decrease in the pup weight was evident. Selenium deprivation caused dose-dependent decreases in liver glutathione peroxidase (28.55 +/- 3.82 mmoles/min/mg vs 34.68 +/- 8.64 mmoles/min/mg) and thioredoxin reductase (2.37 +/- 1.25 U/mg vs 6.68 +/- 1.82 U/mg) activity, whereas superoxide dismutase activity remained constant. Placental activity of these enzymes also decreased leading to oxidative stress as measured by increased lipid peroxides (17.92 +/- 1.78 micromoles/mg vs 8.30 +/- 5.52 micromoles/mg) and protein carbonyls in tissue extracts from selenium-free animals. These results suggest that selenium deficiency in pregnant rats leads to symptoms similar to those seen in human PET and may provide an experimental model for studying this complex disease.