Gross Primary Productivity of Four European Ecosystems Constrained by Joint CO2 and COS Flux Measurements

Gross primary productivity (GPP), the gross uptake of carbon dioxide (CO2) by plant photosynthesis, is the primary driver of the land carbon sink, which presently removes around one quarter of the anthropogenic CO2 emissions each year. GPP, however, cannot be measured directly and the resulting uncertainty undermines our ability to project the magnitude of the future land carbon sink. Carbonyl sulfide (COS) has been proposed as an independent proxy for GPP as it diffuses into leaves in a fashion very similar to CO2, but in contrast to the latter is generally not emitted. Here we use concurrent ecosystem-scale flux measurements of CO2 and COS at four European biomes for a joint constraint on CO2 flux partitioning. The resulting GPP estimates generally agree with classical approaches relying exclusively on CO2 fluxes but indicate a systematic underestimation under low light conditions, demonstrating the importance of using multiple approaches for constraining present-day GPP.

Urban eddy covariance measurements reveal significant missing NOx emissions in Central Europe

Nitrogen oxide (NO_x) pollution is emerging as a primary environmental concern across Europe. While some large European metropolitan areas are already in breach of EU safety limits for NO₂, this phenomenon does not seem to be only restricted to large industrialized areas anymore. Many smaller scale populated agglomerations including their surrounding rural areas are seeing frequent NO₂ concentration violations. The question of a quantitative understanding of different NO_x emission sources is therefore of immanent relevance for climate and air chemistry models as well as air pollution management and health. Here we report simultaneous eddy covariance flux measurements of NO_x, CO₂, CO and non methane volatile organic compound tracers in a city that might be considered representative for Central Europe and the greater Alpine region. Our data show that NO_x fluxes are largely at variance with modelled emission projections, suggesting an appreciable underestimation of the traffic related atmospheric NO_x input in Europe, comparable to the weekend-weekday effect, which locally changes ozone production rates by 40%.

Estimating carbon dioxide fluxes from temperate mountain grasslands using broad-band vegetation indices

The broad-band normalised difference vegetation index (NDVI) and the simple ratio (SR) were calculated from measurements of reflectance of photosynthetically active and short-wave radiation at two temperate mountain grasslands in Austria and related to the net ecosystem CO₂ exchange (NEE) measured concurrently by means of the eddy covariance method. There was no significant statistical difference between the relationships of midday mean NEE with narrow- and broad-band NDVI and SR, measured during and calculated for that same time window, respectively. The skill of broad-band NDVI and SR in predicting CO₂ fluxes was higher for metrics dominated by gross photosynthesis and lowest for ecosystem respiration, with NEE in between. A method based on a simple light response model whose parameters were parameterised based on broad-band NDVI allowed to improve predictions of daily NEE and is suggested to hold promise for filling gaps in the NEE time series. Relationships of CO₂ flux metrics with broad-band NDVI and SR however generally differed between the two studied grassland sites indicting an influence of additional factors not yet accounted for.

Summertime elemental mercury exchange of temperate grasslands on an ecosystem-scale

In order to estimate the air-surface mercury exchange of grasslands in temperate climate regions, fluxes of gaseous elemental mercury (GEM) were measured at two sites in Switzerland and one in Austria during summer 2006. Two classic micrometeorological methods (aerodynamic and modified Bowen ratio) have been applied to estimate net GEM exchange rates and to determine the response of the GEM flux to changes in environmental conditions (e.g. heavy rain, summer ozone) on an ecosystem-scale. Both methods proved to be appropriate to estimate fluxes on time scales of a few hours and longer. Average dry deposition rates up to 4.3 ng m^-2 h^-1 and mean deposition velocities up to 0.10 cm s^-1 were measured, which indicates that during the active vegetation period temperate grasslands are a small net sink for atmospheric mercury. With increasing ozone concentrations depletion of GEM was observed, but could not be quantified from the flux signal. Night-time deposition fluxes of GEM were measured and seem to be the result of mercury co-deposition with condensing water. Effects of grass cuts could also be observed, but were of minor magnitude.

Leaf area controls on energy partitioning of a temperate mountain grassland

Using a six year data set of eddy covariance flux measurements of sensible and latent heat, soil heat flux, net radiation, above-ground phytomass and meteorological driving forces energy partitioning was investigated at a temperate mountain grassland managed as a hay meadow in the Stubai Valley (Austria). The main findings of the study were: (i) Energy partitioning was dominated by latent heat, followed by sensible heat and the soil heat flux; (ii) When compared to standard environmental forcings, the amount of green plant matter, which due to three cuts varied considerably during the vegetation period, explained similar, and partially larger, fractions of the variability in energy partitioning; (iii) There were little, if any, indications of water stress effects on energy partitioning, despite reductions in soil water availability in combination with high evaporative demand, e.g. during the summer drought of 2003.

Effects of pentoxifylline on hemodynamics and oxygenation in septic and nonseptic patients

OBJECTIVE

To evaluate the effects of pentoxifylline on hemodynamics and systemic oxygenation in septic and nonseptic critically ill patients.

DESIGN

Prospective clinical investigation.

SETTING

Intensive care unit (ICU) of a university hospital.

PATIENTS

Nineteen critically ill patients were included in the study 1 to 4 days after their admission to the ICU. A systemic inflammatory response syndrome was present in 12 patients, fulfilling at least two of the American College of Chest Physicians/ Society of Critical Care Medicine Consensus Conference criteria. The other seven patients did not fulfill these criteria and were classified as nonseptic.

INTERVENTIONS

All patients were mechanically ventilated. The dosage of catecholamines was kept constant during the entire study period and at least during 15 mins before the start of the study. In both study groups, pulmonary and radial artery catheters were inserted and 5 mg/kg of pentoxifylline (diluted in 300 mL of physiologic saline) was intravenously administered over a period of 180 mins at a rate of 100 mL/hr.

MEASUREMENTS AND MAIN RESULTS

Hemodynamic variables, oxygen transport (DO2), oxygen uptake (VO2), and oxygen extraction ratio were determined before pentoxifylline, after 2.5 mg/kg of pentoxifylline, after 5 mg/kg of pentoxifylline, and 60 mins after the termination of pentoxifylline. Repeated-measures analysis of variance and Mann-Whitney test were used for statistical analysis. At baseline, there were significant differences between the septic and the nonseptic groups in mean pulmonary arterial pressure (septic: 31 +/- 5 mm Hg; nonseptic: 26 +/- 7 mm Hg, p < .05), and pulmonary vascular resistance index (PVRI) (septic: 344 +/- 121 dyne.sec/ cm5.m2; nonseptic: 233 +/- 100 dyne.sec/cm5.m2, p < .05). In the septic group, significant increases in heart rate and cardiac index were observed. Systemic vascular resistance index and PVRI decreased. No significant changes in hemodynamic variables occurred in the nonseptic group. In both groups, DO2 and VO2 increased significantly, while oxygen extraction ratio remained unchanged.

CONCLUSIONS

The administration of pentoxifylline to septic patients results in a significant improvement in hemodynamic performance compared with critically ill nonseptic patients. The better hemodynamic state is accompanied by an increase in DO2 and VO2 with unchanged oxygen extraction ratio.

The clinical application of two newly developed lipid emulsions (Solipid 20% S&E) in critically ill patients

OBJECTIVE

The clinical compatibility of two newly developed lipid emulsions based on soy oil (20%) emulsified with egg lecithin (12 g/l) or soy lecithin (15 g/l) (Solipid 20% E&S) has been compared.

DESIGN

Double-blind prospective randomized study.

SETTING

Intensive care unit of a university hospital.

PATIENTS

20 patients (16 men, 4 women, age 20-59 years) were entered into the study.

INTERVENTIONS

One g of lipids/kg body weight per day was administered on day 1 and subsequently 2 g/kg/day on days 2-5. Blood was drawn once a day, lipids, lipoproteins, apoproteins and other routine clinical chemistry parameters were determined.

RESULTS

No significant increase of total triglycerides could be observed. Total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, apolipoproteins A I and B usually remained below the reference ranges. Electrolytes, uric acid and glucose, blood cells, parameters of liver and kidney function, coagulation and protein metabolism did not show relevant changes; only the activity of gamma-GT in both groups--independent of the sort of lecithin--increased significantly.

CONCLUSION

The results indicate adequate elimination of both tested lipid emulsions from the plasma at usual clinical conditions. Therefore Solipid 20% S&E can be used in critically ill patients.

Resistance of nitrogen metabolism to growth hormone treatment in the early phase after injury of patients with multiple injuries

OBJECTIVES AND DESIGN

Several studies have shown an anticatabolic effect of recombinant human growth hormone (rhGH) in surgical patients. We investigated, in a prospective, randomized, double blind, and placebo-controlled study, the effect of r-hGH on hormone and nitrogen metabolism in 14 patients with multiple injuries in the early phase of injury.

MATERIALS AND METHODS

All patients were treated in the intensive care unit, had mechanical ventilation, and were highly catabolic, with a mean daily nitrogen loss of 13.2 +/- 1.8 g. r-hGH was given subcutaneously (once a day, at 8 PM) in a dosage of 0.2 IU/kg.d for seven days, starting on the second day after injury.

RESULTS

Administration of r-hGH evoked a significant increase in plasma concentrations of GH, insulin-like growth factor-I (IGF-I), and insulin-like growth factor binding-protein-3 (IGFBP-3). No significant differences were found for either daily or cumulative nitrogen balances (-103.1 +/- 14 g for patients receiving r-hGH and -92.1 +/- 18.1 for those with placebo). r-hGH therapy did not affect skeletal muscle extracellular water, nor did it affect plasma or muscle concentrations of total free amino acids or glutamine. Plasma albumin, prealbumin, and retinol-binding protein concentrations were also unchanged by r-hGH therapy, as were the urinary excretion of potassium and urea.

CONCLUSIONS

We conclude that elevated plasma levels of GH, insulin, and IGF-I are unable to effect a protein anabolic drive in patients with multiple injuries during the early postinjury phase and assume that this r-hGH resistance to nitrogen metabolism takes place at the level distal to IGF-I.

Endothelin-1 in adult respiratory distress syndrome

Endothelin-1 (ET-1), a potent vasoconstrictor peptide produced by endothelial cells and degraded predominantly in the pulmonary vasculature, has been implicated in the development of various organ dysfunctions. To determine the pathophysiologic role of ET-1 in adult respiratory distress syndrome (ARDS) and the impact of impaired lung function on transpulmonary peptide handling, we compared plasma levels and pulmonary ET-1 balance in 14 patients with ARDS and in seven healthy control subjects. To obtain comparable conditions in both groups, the ET-1 level was raised in the control group by exogenous infusion (0.4 pmol/kg/min) to 9.4 +/- 0.8 pmol/L. ARDS was accompanied by a hyperdynamic circulatory pattern with increased cardiac output and depressed total vascular resistance but, simultaneously, pulmonary hypertension. Venous ET-1 concentration was massively increased in ARDS (9.8 +/- 1.2 versus 2.1 +/- 0.2 pmol/L, p < 0.001). In control subjects, the lung cleared the major fraction of ET-1 (fractional extraction 43 +/- 8.8%, uptake 12.5 +/- 2.5 pmol/min). In contrast, in ARDS there was a pronounced pulmonary releases into the circulation (32.8 +/- 10.3 pmol/min). We conclude that ET-1 concentrations are elevated in ARDS as the result of both increased formation and decreased disposal. Lung failure affects not only gas exchange but also nonrespiratory, metabolic pulmonary functions.

Continuous spinal anesthesia with a microcatheter and low-dose bupivacaine decreases the hemodynamic effects of centroneuraxis blocks in elderly patients

This prospective randomized study was designed to investigate the hemodynamic effects and quality of continuous spinal anesthesia (CSA) after rapid injection of a low dose of 0.5% bupivacaine through a 32-gauge microcatheter. The method was compared with continuous epidural (CEA) and single-dose spinal anesthesia (SSA). Seventy-seven elderly patients (ASA II-III) ranging from 57 to 94 yr old and undergoing lower limb surgery were assigned to CSA (n = 26), CEA (n = 26), and SSA groups (n = 25). In all three groups, mean arterial pressure (MAP) and heart rate (HR) were assessed continuously for 30 min after initial injection, as well as after every reinjection of local anesthetic in the CSA and CEA groups. Bupivacaine (0.5%) was used as a local anesthetic. The initial doses were 1 mL of CSA, 10 mL of CEA, and 3 mL of SSA. The reinjection doses were 1 mL of CSA and 5 mL of CEA. In the CSA group, MAP did not decrease, whereas in the CEA group, the maximum decrease was 15% +/- 3% (mean +/- SEM) for the initial injection, 12% +/- 2% for the first repetition, and 13% +/- 2% for the second repetition. In the SSA group, the largest decrease of MAP was 19% +/- 2%. All changes of MAP in the CEA and SSA groups were significantly larger compared with CSA group (P < 0.05). A total of seven patients in these two groups needed vasopressors due to a decrease of MAP of more than 30% from baseline values. Heart rate did not change.(ABSTRACT TRUNCATED AT 250 WORDS)

[Obstetric management of patients with HELLP syndrome]

The syndrome of haemolysis, elevated liver enzymes and low platelet count (HELLP-Syndrome) is a severe form of preeclampsia and eclampsia. The clinical course is characterized by right upper quadrant and epigastric pain, hypertension, proteinuria and edema. Maternal and neonatal morbidity are high. The underlying cause for this pregnancy-related syndrome is still unclear. As soon as a reliable diagnosis is established handling of patients suffering from HELLP-Syndrome is ambivalent: Immediate termination of pregnancy, however, poses a problem at early gestational age. Therefore some authors have advocated a conservative management. At our department active management and delivery by Caesarean section as soon as possible has gained acceptance in the past 5 years. We report our experience with 23 patients over a 12 year period, and with 4 patients from the intensive care unit (N = 27). Mean gestational age was 33.5 weeks (+/- 4.8) and the mean birthweight was 1922.5 g (+/- 971.5). 19 patients were delivered by Caesarean section. Most complications were based on a delayed delivery and subsequent deterioration of maternal condition. Reduction of the time interval between establishment of diagnosis and termination of pregnancy (1980-1985-3 days; 1986-1992-12 hours) resulted in a better outcome. We recommend intensive laboratory screening and exact clinical examination since missed or delayed diagnosis as well as delayed delivery are life threatening for mother and child. Only prompt delivery yields an improvement of prognosis.

Right ventricular function in early septic shock states

OBJECTIVES

To define a variable which could reliably predict when fluid resuscitation as monotherapy is not expected to improve organ perfusion pressure, owing to limitations in cardiac output responsiveness in patients with severe sepsis.

DESIGN

Prospective controlled trial.

SETTING

Anesthesiological ICU in a university hospital.

PATIENTS

Twenty seven patients in early septic shock states (MAP < 60 mmHg).

INTERVENTIONS

Infusion therapy was titrated until no further increase in cardiac index and mean arterial pressure could be achieved. Fluid resuscitation as monotherapy was deemed unsuccessful at the end of 2 h if inotropic or vasoactive pharmacologic support was required to maintain a mean arterial pressure > 60 mmHg.

MEASUREMENTS AND RESULTS

We investigated the hemodynamic course during fluid resuscitation (2850 +/- 210 ml crystalloids) with special emphasis on right heart function using the thermodilution technique. Eleven patients (group A) had a right ventricular (RV) ejection fraction below 45%. In this group positive inotropic and/or vasoactive drugs were obligatory to achieve and maintain a sufficient perfusion pressure (MAP > 60 mmHg) after fluid challenge.

CONCLUSIONS

In 27 septic shock patients investigated, we diagnosed right ventricular dysfunction in 41%. In this specific patient population fluid replacement alone did not succeed in stabilizing hemodynamic variables, therefore necessitating catecholamine therapy.

Whole blood aggregometry and platelet adenine nucleotides during cardiac surgery

The influence of extracorporeal circulation (ECC) on human platelet adenine nucleotides has been studied in 28 coronary bypass patients before, during and after operation. An oscillating pattern of transient increases and decreases in total platelet ATP was observed following the sternotomy until the end of the operation. A highly significant increase in platelet ATP (20% +/- 14 of the pre-anaesthesia values) occurred during the first 24 h after surgery. Total platelet ADP however, did not show this oscillation nor was there any significant release of ADP from the platelets during ECC. Following collagen activation, increased amounts of 'releaseable ATP' were found after protaminization (124% +/- 38 of pre-anaesthesia values) (p less than 0.05), although whole blood aggregability was slightly reduced (89% +/- 18 of pre-anaesthesia values). This study indicates that 1) the metabolic ATP pool of circulating platelets underwent rapid changes during open heart surgery; 2) the majority of platelets did not release inert ADP during ECC; 3) there may be a compensatory enhancement of platelet function by other blood cells, which could explain the discrepancy between our aggregatory results in whole blood and those reported in platelet rich plasma (PRP) aggregometry.

Endothelial cell seeding of polytetrafluoroethylene vascular grafts in humans: a preliminary report

The importance of initial human trials with autologous endothelial seeding lies not only in the implementation of a promising idea but also in the fact that canine data are only partially applicable to humans. The surface area of jugular veins in humans is much smaller than in dogs and considerably longer grafts are needed. Moreover, the reproductive capacity of adult human endothelial cells under in vivo conditions, which probably determines the success of seeding more than the seeding density, is also uncertain. Therefore the efficiency of autologous endothelial seeding in humans was investigated in 18 patients undergoing distal femoropopliteal bypass surgery. The average surface area of the jugular veins was 4.9 +/- 1.7 cm2 with an average cell yield of 32.6 +/- 18.0 x 10(4). The mean number of seeded cells per square centimeter of graft surface was 3.1 x 10(3). In a follow-up extending for 14 weeks, plasma levels of platelet factor 4 and beta-thromboglobulin as well as the platelet function in the whole blood aggregometer showed significantly better results in the seeded group. Plasma thromboxane B2, uptake and survival of indium 111-labeled platelets, and Doppler ultrasound investigations also favored the seeded group, but the results were statistically insignificant. No difference at all was found for the platelet dense granule compounds, releasable adenosine triphosphate and platelet serotonin. Thus our findings did not indicate the development of a closed endothelialized surface after 14 weeks, which is a period three times as long as the one required for confluent endothelial cell coverage in dogs.(ABSTRACT TRUNCATED AT 250 WORDS)

Scanning electron microscopy of circulating platelets reveals new aspects of platelet alteration during cardiopulmonary bypass operations

Seventeen male patients undergoing cardiopulmonary bypass (CPBP) surgery for aorto-coronary bypass grafting were investigated by scanning electron microscopy (SEM) for alterations of the surface morphology of circulating platelets. An initial decline in the percentage of unactivated smooth discocytes (SD) to 87 +/- 12% was found after thoracotomy. Three minutes after the onset of CPBP, the percentage of SD had dropped drastically to 59 +/- 13%, and by the 8th minute of CPBP it had dropped to its lowest point (49 +/- 19%). On the other hand, the percentage of shape-changed platelets (SC) increased to 17 +/- 9% after 3 minutes, and the percentage of pseudopod discocytes (PD) to 25 +/- 13% after 8 minutes. Surprisingly, a remarkable recovery of platelet morphology could be observed after even 15 minutes of CPBP, and by the end of bypass 78 +/- 15% of the circulating platelets had regained the smooth discoid (SD) appearance of unactivated platelets. We conclude that this recovery of platelet morphology is due to an increasing insensitivity of the platelets to activating stimuli during the course of CPBP. Our study provides evidence that the only major platelet activation occurs during the first minutes of CPBP, and that CPBP-caused platelet activation is much less pronounced than generally believed.

Role of beta-endorphins in silent myocardial ischemia

The reason for the absence of pain perception in silent myocardial ischemia is unknown. A role of increased endorphinic activity in patients with silent ischemia has been postulated. To further investigate this hypothesis, 10 men with documented coronary artery disease and previous positive electrocardiographic findings during exercise without anginal pain were studied. Six healthy volunteers served as control subjects. The protocol included 2 bicycle exercise tests, the first test serving as baseline and the second performed after administration of naloxone, a specific opiate antagonist. Plasma beta-endorphin levels were measured by radioimmunoassay in both tests at rest, at peak exercise level and after recovery. All patients underwent thallium-201 scintigraphy after coronary vasodilation to provide an additional independent marker of ischemia. All patients showed stress-induced reversible perfusion abnormalities. No patient reported pain after naloxone application. Exercise duration, blood pressure and heart rate were not significantly altered by naloxone. Plasma beta-endorphin levels ranged from 18 +/- 6 pg/100 microliters (mean +/- standard deviation) at rest to 22 +/- 6 pg/100 microliters during exercise in the patient group and from 20 +/- 5 to 27 +/- 9 pg/100 microliters in the control subjects. Thus, there was no significant increase of plasma beta-endorphins during exercise or after naloxone administration, nor was there any difference observed between patients and control group. These data support the view that endorphinic activity does not play an essential role in the pathophysiology of silent myocardial ischemia.