Comparison of arterial versus venous parameters of Rotational thromboelastometry and multiple platelet function analyzer: results of a pilot study.

BACKGROUND: In the operating room and at the ICU, Rotational thromboelastometry (ROTEM) and multiple platelet function analyzer (Multiplate) are frequently performed on arterial blood samples while known reference ranges refer to venous blood only. To evaluate whether there are clinical important differences between parameters measured in arterial and venous blood, we performed a prospective study in patients undergoing orthopedic surgery. METHODS: Arterial and venous blood samples were drawn simultaneously after line insertion (T0), intraoperatively (T1), at the end of surgery (T2) and the INTEM, EXTEM and FIBTEM ROTEM assays, as well as the ASPI, ADP and TRAP assays were performed in arterial and venous samples using the ROTEM and the Multiplate device, respectively. RESULTS: After informed consent, 52 patients were enrolled and data of 50 patients remained for final analysis. Venous and arterial measurement results correlated significantly with a coefficient of 0.519-0.977. At the three measurement points only a few statistically significant deviations were detected for some of the ROTEM and Multiplate parameters. The magnitude of differences was small and most likely without clinical relevance. Pathological conditions were detected with similar frequency regardless of the sampling site. Only Multiplate TRAP at T0 indicated low platelet aggregation more frequently in venous than in arterial samples (p = 0.0455); however, values were only narrow below reference range. CONCLUSION: The observed differences between arterial and venous results were within the range of variability of the methods reported for venous blood. Pathological values that might be clinically relevant could be detected at similar rates regardless of the sampling site.

Recombinant angiotensin-converting enzyme 2 improves pulmonary blood flow and oxygenation in lipopolysaccharide-induced lung injury in piglets.

OBJECTIVE: To study angiotensin-converting enzyme 2 in a piglet model with acute respiratory distress syndrome and to evaluate the therapeutic potential of this substance in a preclinical setting, as this model allows the assessment of the same parameters required for monitoring the disease in human intensive care medicine. The acute respiratory distress syndrome is the most severe form of acute lung injury with a high mortality rate. As yet, there is no specific therapy for improving the clinical outcome. Recently, angiotensin-converting enzyme 2, which inactivates angiotensin II, has been shown to ameliorate acute lung injury in mice. DESIGN: Prospective, randomized, double-blinded animal study. SETTING: Animal research laboratory. SUBJECTS: Fifteen anesthetized and mechanically ventilated piglets. INTERVENTIONS: Acute respiratory distress syndrome was induced by lipopolysaccharide infusion. Thereafter, six animals were assigned randomly into angiotensin-converting enzyme 2 group, whereas another six animals served as control. Three animals received angiotensin-converting enzyme 2 without lipopolysaccharide pretreatment. MEASUREMENTS AND MAIN RESULTS: Systemic and pulmonary hemodynamics, blood gas exchange parameters, tumor necrosis factor-alpha, and angiotensin II levels were examined before acute respiratory distress syndrome induction and at various time points after administering angiotensin-converting enzyme 2 or saline. In addition, ventilation-perfusion distribution of the lung tissue was assessed by the multiple inert gas elimination technique. Animals treated with angiotensin-converting enzyme 2 maintained significantly higher PaO2 than the control group, and pulmonary hypertension was less pronounced. Furthermore, angiotensin II and tumor necrosis factor-alpha levels, both of which were substantially increased, returned to basal values. Multiple inert gas elimination technique revealed a more homogeneous pulmonary blood flow after treatment with angiotensin-converting enzyme 2. In intergroup comparisons, there were no differences in pulmonary blood flow to lung units with subnormal ventilation/perfusion ratios. CONCLUSIONS: Angiotensin-converting enzyme 2 attenuates arterial hypoxemia, pulmonary hypertension, and redistribution of pulmonary blood flow in a piglet model of acute respiratory distress syndrome, and may be a promising substance for clinical use.