Comparison of cardiac,hepatic, and renal effects of arginine vasopressin and noradrenaline during porcine fecal peritonitis: a randomized controlled trial

Introduction

Infusing arginine vasopressin (AVP) in vasodilatory shock usually decreases cardiac output and thus systemic oxygen transport. It is still a matter of debate whether this vasoconstriction impedes visceral organ blood flow and thereby causes organ dysfunction and injury. Therefore, we tested the hypothesis whether low-dose AVP is safe with respect to liver, kidney, and heart function and organ injury during resuscitated septic shock.

Methods

After intraperitoneal inoculation of autologous feces, 24 anesthetized, mechanically ventilated, and instrumented pigs were randomly assigned to noradrenaline alone (increments of 0.05 μg/kg/min until maximal heart rate of 160 beats/min; n = 12) or AVP (1 to 5 ng/kg/min; supplemented by noradrenaline if the maximal AVP dosage failed to maintain mean blood pressure; n = 12) to treat sepsis-associated hypotension. Parameters of systemic and regional hemodynamics (ultrasound flow probes on the portal vein and hepatic artery), oxygen transport, metabolism (endogenous glucose production and whole body glucose oxidation derived from blood glucose isotope and expiratory ¹³CO₂/¹²CO₂ enrichment during 1,2,3,4,5,6-¹³C₆-glucose infusion), visceral organ function (blood transaminase activities, bilirubin and creatinine concentrations, creatinine clearance, fractional Na⁺ excretion), nitric oxide (exhaled NO and blood nitrate + nitrite levels) and cytokine production (interleukin-6 and tumor necrosis factor-α blood levels), and myocardial function (left ventricular dp/dt_max and dp/dt_min) and injury (troponin I blood levels) were measured before and 12, 18, and 24 hours after peritonitis induction. Immediate post mortem liver and kidney biopsies were analysed for histomorphology (hematoxylin eosin staining) and apoptosis (TUNEL staining).

Results

AVP decreased heart rate and cardiac output without otherwise affecting heart function and significantly decreased troponin I blood levels. AVP increased the rate of direct, aerobic glucose oxidation and reduced hyperlactatemia, which coincided with less severe kidney dysfunction and liver injury, attenuated systemic inflammation, and decreased kidney tubular apoptosis.

Conclusions

During well-resuscitated septic shock low-dose AVP appears to be safe with respect to myocardial function and heart injury and reduces kidney and liver damage. It remains to be elucidated whether this is due to the treatment per se and/or to the decreased exogenous catecholamine requirements.     

Vasopressin impairs brain, heart and kidney perfusion: an experimental study in pigs after transient myocardial ischemia

Introduction

Arginine vasopressin (AVP) is increasingly used to restore mean arterial pressure (MAP) in low-pressure shock states unresponsive to conventional inotropes. This is potentially deleterious since AVP is also known to reduce cardiac output by increasing vascular resistance. The effects of AVP on blood flow to vital organs and cardiac performance in a circulation altered by cardiac ischemia are still not sufficiently clarified. We hypothesised that restoring MAP by low dose, therapeutic level AVP would reduce vital organ blood flow in a setting of experimental acute left ventricular dysfunction.

Methods

Cardiac output (CO) and arterial blood flow to the brain, heart, kidney and liver were measured in nine pigs using transit-time flow probes. Left ventricular pressure-volume catheter and central arterial and venous catheters were used for haemodynamic recordings and blood sampling. Transient left ventricular ischemia was induced by intermittent left coronary occlusions resulting in a 17% reduction in cardiac output and a drop in MAP from 87 ± 3 to 67 ± 4 mmHg (p < 0.001). A low-dose therapeutic level of AVP (0.005 U/kg/min) was used to restore MAP to pre-ischemic values (93 ± 4 mmHg).

Results

AVP further impaired systemic perfusion (CO and brain, heart and kidney blood flow reduced by 29, 18, 23 and 34%, respectively) due to a 2.0-, 2.2-, 1.9- and 2.1-fold increase in systemic, brain, heart and kidney specific vascular resistances. The hypoperfusion induced by AVP was associated with an increased systemic oxygen extraction. Oxygen saturation in blood drawn from the great cardiac vein fell from 29 ± 1 to 21 ± 3% (p = 0.01). Finally, these effects were reversed 40 min after AVP was withdrawn.

Conclusion

Low dose AVP induced a pronounced reduction in vital organ blood flow in pigs after transient cardiac ischemia. This indicates a potentially deleterious effect of AVP in patients with heart failure or cardiogenic shock due to impaired coronary perfusion.     

Comparing two different arginine vasopressin doses in advanced vasodilatory shock: a randomized, controlled, open-label trial

Purpose

To compare the effects of two arginine vasopressin (AVP) dose regimens on the hemodynamic response, catecholamine requirements, AVP plasma concentrations, organ function and adverse events in advanced vasodilatory shock.

Methods

In this prospective, controlled, open-label trial, patients with vasodilatory shock due to sepsis, systemic inflammatory response syndrome or after cardiac surgery requiring norepinephrine >0.6???g/kg/min were randomized to receive a supplementary AVP infusion either at 0.033?IU/min (n?=?25) or 0.067?IU/min (n?=?25). The hemodynamic response, catecholamine doses, laboratory and organ function variables as well as adverse events (decrease in cardiac index or platelet count, increase in liver enzymes or bilirubin) were recorded before, 1, 12, 24 and 48?h after randomization. A linear mixed effects model was used for statistical analysis in order to account for drop-outs during the observation period.

Results

Heart rate and norepinephrine requirements decreased while MAP increased in both groups. Patients receiving AVP at 0.067?IU/min required less norepinephrine (P?=?0.006) than those infused with AVP at 0.033?IU/min. Arterial lactate and base deficit decreased while arterial pH increased in both groups. During the observation period, AVP plasma levels increased in both groups (both P?<?0.001), but were higher in the 0.067?IU/min group (P?<?0.001) and in patients on concomitant hydrocortisone. The rate of adverse events and intensive care unit mortality was comparable between groups (0.033?IU/min, 52%; 0.067?IU/min, 52%; P?=?1).

Conclusions

A supplementary AVP infusion of 0.067?IU/min restores cardiovascular function in patients with advanced vasodilatory shock more effectively than AVP at 0.033?IU/min.     

Role of selective V2-receptor-antagonism in septic shock: a randomized, controlled, experimental study

Introduction

V₂-receptor (V₂R) stimulation potentially aggravates sepsis-induced vasodilation, fluid accumulation and microvascular thrombosis. Therefore, the present study was performed to determine the effects of a first-line therapy with the selective V₂R-antagonist (Propionyl₁-D-Tyr(Et)₂-Val₄-Abu₆-Arg_8,9)-Vasopressin on cardiopulmonary hemodynamics and organ function vs. the mixed V_1aR/V₂R-agonist arginine vasopressin (AVP) or placebo in an established ovine model of septic shock.

Methods

After the onset of septic shock, chronically instrumented sheep were randomly assigned to receive first-line treatment with the selective V₂R-antagonist (1 μg/kg per hour), AVP (0.05 μg/kg per hour), or normal saline (placebo, each n = 7). In all groups, open-label norepinephrine was additionally titrated up to 1 μg/kg per minute to maintain mean arterial pressure at 70 ± 5 mmHg, if necessary.

Results

Compared to AVP- and placebo-treated animals, the selective V₂R-antagonist stabilized cardiopulmonary hemodynamics (mean arterial and pulmonary artery pressure, cardiac index) as effectively and increased intravascular volume as suggested by higher cardiac filling pressures. Furthermore, left ventricular stroke work index was higher in the V₂R-antagonist group than in the AVP group. Notably, metabolic (pH, base excess, lactate concentrations), liver (transaminases, bilirubin) and renal (creatinine and blood urea nitrogen plasma levels, urinary output, creatinine clearance) dysfunctions were attenuated by the V₂R-antagonist when compared with AVP and placebo. The onset of septic shock was associated with an increase in AVP plasma levels as compared to baseline in all groups. Whereas AVP plasma levels remained constant in the placebo group, infusion of AVP increased AVP plasma levels up to 149 ± 21 pg/mL. Notably, treatment with the selective V₂R-antagonist led to a significant decrease of AVP plasma levels as compared to shock time (P < 0.001) and to both other groups (P < 0.05 vs. placebo; P < 0.001 vs. AVP). Immunohistochemical analyses of lung tissue revealed higher hemeoxygenase-1 (vs. placebo) and lower 3-nitrotyrosine concentrations (vs. AVP) in the V₂R-antagonist group. In addition, the selective V₂R-antagonist slightly prolonged survival (14 ± 1 hour) when compared to AVP (11 ± 1 hour, P = 0.007) and placebo (11 ± 1 hour, P = 0.025).

Conclusions

Selective V₂R-antagonism may represent an innovative therapeutic approach to attenuate multiple organ dysfunction in early septic shock.     

Effects of hydrogen sulfide on hemodynamics, inflammatory response and oxidative stress during resuscitated hemorrhagic shock in rats

Introduction

Hydrogen sulfide (H₂S) has been shown to improve survival in rodent models of lethal hemorrhage. Conversely, other authors have reported that inhibition of endogenous H₂S production improves hemodynamics and reduces organ injury after hemorrhagic shock. Since all of these data originate from unresuscitated models and/or the use of a pre-treatment design, we therefore tested the hypothesis that the H₂S donor, sodium hydrosulfide (NaHS), may improve hemodynamics in resuscitated hemorrhagic shock and attenuate oxidative and nitrosative stresses.

Methods

Thirty-two rats were mechanically ventilated and instrumented to measure mean arterial pressure (MAP) and carotid blood flow (CBF). Animals were bled during 60 minutes in order to maintain MAP at 40 ± 2 mm Hg. Ten minutes prior to retransfusion of shed blood, rats randomly received either an intravenous bolus of NaHS (0.2 mg/kg) or vehicle (0.9% NaCl). At the end of the experiment (T = 300 minutes), blood, aorta and heart were harvested for Western blot (inductible Nitric Oxyde Synthase (iNOS), Nuclear factor-κB (NF-κB), phosphorylated Inhibitor κB (P-IκB), Inter-Cellular Adhesion Molecule (I-CAM), Heme oxygenase 1(HO-1), Heme oxygenase 2(HO-2), as well as nuclear respiratory factor 2 (Nrf2)). Nitric oxide (NO) and superoxide anion (O₂ ^-) were also measured by electron paramagnetic resonance.

Results

At the end of the experiment, control rats exhibited a decrease in MAP which was attenuated by NaHS (65 ± 32 versus 101 ± 17 mmHg, P < 0.05). CBF was better maintained in NaHS-treated rats (1.9 ± 1.6 versus 4.4 ± 1.9 ml/minute P < 0.05). NaHS significantly limited shock-induced metabolic acidosis. NaHS also prevented iNOS expression and NO production in the heart and aorta while significantly reducing NF-kB, P-IκB and I-CAM in the aorta. Compared to the control group, NaHS significantly increased Nrf2, HO-1 and HO-2 and limited O₂ ^- release in both aorta and heart (P < 0.05).

Conclusions

NaHS is protective against the effects of ischemia reperfusion induced by controlled hemorrhage in rats. NaHS also improves hemodynamics in the early resuscitation phase after hemorrhagic shock, most likely as a result of attenuated oxidative stress. The use of NaHS hence appears promising in limiting the consequences of ischemia reperfusion (IR).     

Evaluation of [18F]Mefway Biodistribution and Dosimetry Based on Whole-Body PET Imaging of Mice

Purpose

[¹⁸F]Mefway is a novel radiotracer specific to the serotonin 5-HT_1A receptor class. In preparation for using this tracer in humans, we have performed whole-body PET studies in mice to evaluate the biodistribution and dosimetry of [¹⁸F]Mefway.

Methods

Six mice (three females and three males) received IV injections of [¹⁸F]Mefway and were scanned for 2 h in an Inveon-dedicated PET scanner. Each animal also received a high-resolution CT scan using an Inveon CT. The CT images were used to draw volume of interest on the following organs: the brain, large intestine, stomach, heart, kidneys, liver, lungs, pancreas, bone, spleen, testes, thymus, gallbladder, uterus, and urinary bladder. All organ time-activity curves without decay correction were normalized to the injected activity. The area under the normalized curves was then used to compute the residence times in each organ. Data were analyzed using PMOD and Matlab software. The absorbed doses in mouse organs were computed using the RAdiation Dose Assessment Resource animal models for dose assessment. The residence times in mouse organs were converted to human values using scale factors based on differences between organ and body weights. OLINDA/EXM 1.1 software was used to compute the absorbed human doses in multiple organs for both female and male phantoms.

Results

The highest mouse residence times were found in the liver, urinary bladder, and kidneys. The largest doses in mice were found in the urinary bladder (critical organ), kidney, and liver for both females and males, indicating primary elimination via urinary system. The projected human effective doses were 1.21E???02 mSv/MBq for the adult female model and 1.13E???02 mSv/MBq for the adult male model. The estimated human biodistribution of [¹⁸F]Mefway was similar to that of [¹¹C]WAY 100,635, a 5-HT_1A tracer for which dosimetry has been evaluated in humans.

Conclusions

The elimination of radiotracer was primarily via the kidney and urinary bladder with the urinary bladder being the critical organ. Whole-body mouse imaging can be used as a preclinical tool to provide initial estimates of the absorbed doses of [¹⁸F]Mefway in humans.     

Cutaneous vascular reactivity and flow motion response to vasopressin in advanced vasodilatory shock and severe postoperative multiple organ dysfunction syndrome

Introduction

Disturbances in microcirculatory homeostasis have been hypothesized to play a key role in the pathophysiology of multiple organ dysfunction syndrome and vasopressor-associated ischemic skin lesions. The effects of a supplementary arginine vasopressin (AVP) infusion on microcirculation in vasodilatory shock and postoperative multiple organ dysfunction syndrome are unknown.

Method

Included in the study were 18 patients who had undergone cardiac or major surgery and had a mean arterial blood pressure below 65 mmHg, despite infusion of more than 0.5 μg/kg per min norepinephrine. Patients were randomly assigned to receive a combined infusion of AVP/norepinephrine or norepinephrine alone. Demographic and clinical data were recorded at study entry and after 1 hour. A laser Doppler flowmeter was used to measure the cutaneous microcirculatory response at randomization and after 1 hour. Reactive hyperaemia and oscillatory changes in the Doppler signal were measured during the 3 minutes before and after a 5-minute period of forearm ischaemia.

Results

Patients receiving AVP/norepinephrine had a significantly higher mean arterial pressure (P = 0.047) and higher milrinone requirements (P = 0.025) than did the patients who received norepinephrine only at baseline. Mean arterial blood pressure significantly increased (P < 0.001) and norepinephrine requirements significantly decreased (P < 0.001) in the AVP/norepinephrine group. Patients in the AVP/norepinephrine group exhibited a significantly higher oscillation frequency of the Doppler signal before ischaemia and during reperfusion at randomization. During the study period, there were no differences in either cutaneous reactive hyperaemia or the oscillatory pattern of vascular tone between groups.

Conclusion

Supplementary AVP infusion in patients with advanced vasodilatory shock and severe postoperative multiple organ dysfunction syndrome did not compromise cutaneous reactive hyperaemia and flowmotion when compared with norepinephrine infusion alone.     

Association between length of storage of red blood cell units and outcome of critically ill children: a prospective observational study

Introduction

Acute kidney injury (AKI) in the ICU is associated with poorer prognosis. Hydroxyethylstarch (HES) solutions are fluid resuscitation colloids frequently used in the ICU with controversial nephrotoxic adverse effects. Our study objective was to evaluate HES impact on renal function and organ failures.

Methods

This observational retrospective study included 363 patients hospitalized for more than 72 hours in our ICU. A hundred and sixty eight patients received HES during their stay and 195 did not. We recorded patients' baseline characteristics on admission and type and volume of fluid resuscitation during the first 3 weeks of ICU stay. We also noted the evolution of urine output, the risk of renal dysfunction, injury to the kidney, failure of kidney function, loss of kidney function and end-stage kidney disease (RIFLE) classification and sepsis related organ failure assessment (SOFA) score over 3 weeks.

Results

Patients in the HES group were more severely ill on admission but AKI incidence was similar, as well as ICU mortality. The evolution of urine output (P = 0.74), RIFLE classification (P = 0.44) and SOFA score (P = 0.23) was not different. However, HES volumes administered were low (763+/-593 ml during the first 48 hours).

Conclusions

Volume expansion with low volume HES 130 kDa/0.4 was not associated with AKI.     

Dobutamine reverses the vasopressin-associated impairment in cardiac index and systemic oxygen supply in ovine endotoxemia

Introduction

Arginine vasopressin (AVP) is increasingly used to treat sepsis-related vasodilation and to decrease catecholamine requirements. However, AVP infusion may be associated with a marked decrease in systemic blood flow and oxygen transport. The purpose of the present study was to evaluate whether dobutamine may be titrated to reverse the AVP-related decrease in cardiac index (CI) and systemic oxygen delivery index (DO₂I) in an established model of ovine endotoxemia.

Methods

Twenty-four adult ewes were chronically instrumented to determine cardiopulmonary hemodynamics and global oxygen transport. All ewes received a continuous endotoxin infusion that contributed to a hypotensive-hyperdynamic circulation and death of five sheep. After 16 hours of endotoxemia, the surviving ewes (n = 19; weight 35.6 ± 1.5 kg (mean ± SEM)) were randomized to receive either AVP (0.04 Umin^-1) and dobutamine (n = 8) or the vehicle (normal saline; n = 6) and compared with a third group treated with AVP infusion alone (n = 5). Dobutamine infusion was started at an initial rate of 2 μg kg^-1min^-1 and was increased to 5 and 10 μg kg^-1 min^-1 after 30 and 60 minutes, respectively.

Results

AVP infusion increased mean arterial pressure (MAP) and systemic vascular resistance index at the expense of a markedly decreased CI (4.1 ± 0.5 versus 8.2 ± 0.3 l min^-1 m^-2), DO₂I (577 ± 68 versus 1,150 ± 50 ml min^-1 m^-2) and mixed-venous oxygen saturation (S_vO₂; 54.5 ± 1.8% versus 69.4 ± 1.0%; all p < 0.001 versus control). Dobutamine dose-dependently reversed the decrease in CI (8.8 ± 0.7 l min^-1 m^-2 versus 4.4 ± 0.5 l min^-1 m^-2), DO₂I (1323 ± 102 versus 633 ± 61 ml min^-1 m^-2) and S_vO₂ (72.2 ± 1.7% versus 56.5 ± 2.0%, all p < 0.001 at dobutamine 10 μg kg^-1 min^-1 versus AVP group) and further increased MAP.

Conclusion

This study provides evidence that dobutamine is a useful agent for reversing the AVP-associated impairment in systemic blood flow and global oxygen transport.     

Effects of vasopressinergic receptor agonists on sublingual microcirculation in norepinephrine-dependent septic shock

Introduction

The present study was designed to determine the effects of continuously infused norepinephrine (NE) plus (1) terlipressin (TP) or (2) arginine vasopressin (AVP) or (3) placebo on sublingual microcirculation in septic shock patients. The primary study end point was a difference of ≥ 20% in the microvascular flow index of small vessels among groups.

Methods

The design of the study was a prospective, randomized, double-blind clinical trial. NE was titrated to maintain mean arterial pressure (MAP) between 65 and 75 mmHg after establishment of normovolemia in 60 septic shock patients. Thereafter patients (n = 20 per group) were randomized to receive continuous infusions of either TP (1 μg/kg/hour), AVP (0.04 U/minute) or placebo (isotonic saline). In all groups, open-label NE was adjusted to maintain MAP within threshold values if needed. The sublingual microcirculatory blood flow of small vessels was assessed by sidestream dark-field imaging. All measurements, including data from right heart catheterization and norepinephrine requirements, were obtained at baseline and 6 hours after randomization.

Results

TP and AVP decreased NE requirements at the end of the 6-hour study period. The data are medians (25th and 75th interquartile ranges (IQRs)): 0.57 μg/kg/minute (0.29 to 1.04) vs. 0.16 μg/kg/minute (0.03 to 0.37) for TP and 0.40 μg/kg/minute (0.20 to 1.05) vs. 0.23 μg/kg/minute (0.03 to 0.77) for AVP, with statistical significance of P < 0.05 vs. baseline and vs. placebo. There were no differences in sublingual microcirculatory variables, systemic hemodynamics, oxygen transport and acid-base homeostasis among the three study groups during the entire observation period. The proportions of perfused vessels increased in relation to baseline within all study groups, and there were no significant differences between groups. The specific data were as follows (median (IQR)): 9.7% (2.6 to 19.8) for TP, 8.9% (0.0 to 17.8) for AVP, and 6.9% (3.5 to 10.1) for placebo (P < 0.05 vs. baseline for each comparison), as well as perfused vessel density 18.6% (8.6 to 36.9) for TP, 20.2% (-3.0 to 37.2) for AVP, and 11.4% (-3.0 to 19.4) for placebo (P < 0.05 vs. baseline for each comparison).

Conclusions

The present study suggests that to achieve a MAP of 65 to 75 mmHg in septic patients treated with NE, the addition of continuously infused low-dose TP or AVP does not affect sublingual microcirculatory blood flow. In addition, our results suggest that microcirculatory flow abnormalities are mainly related to other factors (for example, volume status, timing, hemodynamics and progression of the disease) rather than to the vasopressor per se.

Trial registration

ClinicalTrial.gov NCT00995839     

Vasopressin or norepinephrine in early hyperdynamic septic shock: a randomized clinical trial

Objective To compare the effects of arginine-vasopressin (AVP) and norepinephrine (NE) on hemodynamic variables, organ dysfunction, and adverse events in early hyperdynamic septic shock.Design and setting Randomized, controlled, open-label trial.Patients and participants Twenty-three patients with early (12 h) hyperdynamic septic shock in two teaching hospitals.Interventions AVP (0.04–0.20 U min^–1, n = 13) as a single agent or NE (0.1–2.8 μg kg^–1 min^–1, n = 10) infusion for 48 h to achieve mean arterial pressure at or above 70 mmHg.Measurements and results Hemodynamic parameters and Sequential Organ Failure Assessment (SOFA) score were measured. AVP and NE equally increased mean arterial pressure over 48 h, but NE was required in 36% of AVP patients at 48 h. Compared to baseline, AVP increased systemic vascular resistance, decreased exposure to NE, decreased cardiac output by decreasing heart rate, increased creatinine clearance, and improved SOFA score. The PrCO₂ – PaCO₂ difference remained stable throughout the study. One AVP patient developed acute coronary syndrome with dose-dependent ECG changes. Three patients in both groups died during their ICU stay.Conclusion In early hyperdynamic septic shock, the administration of high-dose AVP as a single agent fails to increase mean arterial pressure in the first hour but maintains it above 70 mmHg in two-thirds of patients at 48 h. AVP decreases NE exposure, has no effect on the PrCO₂ – PaCO₂ difference, and improves renal function and SOFA score.This work was supported by the Cardiovascular Critical Care research Network FRSQ and departmental funding.     

The effects of vasopressin on acute kidney injury in septic shock

Objective

To compare the effects of vasopressin versus norepinephrine infusion on the outcome of kidney injury in septic shock.

Design and setting

Post-hoc analysis of the multi-center double-blind randomized controlled trial of vasopressin versus norepinephrine in adult patients who had septic shock (VASST).

Patients and intervention

Seven hundred seventy-eight patients were randomized to receive a blinded infusion of either low-dose vasopressin (0.01–0.03 U/min) or norepinephrine infusion (5–15 μg/min) in addition to open-label vasopressors and were included in the outcome analysis. All vasopressors were titrated and weaned to maintain a target blood pressure.

Measurement and results

RIFLE criteria for acute kidney injury were used to compare the effects of vasopressin versus norepinephrine. In view of multiple simultaneous comparisons, a p value of 0.01 was considered statistically significant. Kidney injury was present in 464 patients (59.6%) at study entry. In patients in the RIFLE “Risk” category (n = 106), vasopressin as compared with norepinephrine was associated with a trend to a lower rate of progression to renal “Failure” or “Loss” categories (20.8 vs. 39.6%, respectively, p = 0.03), and a lower rate of use of renal replacement therapy (17.0 vs. 37.7%, p = 0.02). Mortality rates in the “Risk” category patients treated with vasopressin compared to norepinephrine were 30.8 versus 54.7%, p = 0.01, but this did not reach significance in a multiple logistic regression analysis (OR = 0.33, 99% CI 0.10–1.09, p = 0.02). The interaction of treatment group and RIFLE category was significant in predicting mortality.

Conclusions

Vasopressin may reduce progression to renal failure and mortality in patients at risk of kidney injury who have septic shock.     

Impairment of bacterial clearance induced by norepinephrine infusion in rabbits

Objective

Purpose of the study was to investigate the potential influence of norepinephrine (NE) on immune functions in terms of systemic and organ-specific bacterial clearance in rabbits.

Design

To enable quantification of the clearance process, defined numbers of exogenousEscherichia coli (1.3×10⁸ CFU) were injected intravenously 60 min after starting the NE infusion at a low dose (1 μg/kg per min,n=6), causing an increase (30 mmHg) in mean arterial pressure without affecting the oxygen uptake, and at a higher dose (7.5 μg/kg per min,n=6), resulting in a marked decrease (20%) in oxygen uptake, after infusion of NaCl solution (control,n=6). In additional experiments (n=6) NE (1 μg/kg per min) was tested in endotoxemia induced by simultaneous infusion of endotoxin (40 μg/kg per h). Parameters monitored were arterial pressure, oxygen uptake, and rates of bacterial elimination from the blood. At 180 min afterE. coli injection, the animals were sacrificed, and tissue samples of liver, kidney, spleen, and lung were collected for bacterial counts.

Results

NE infusion resulted in a dose-dependent prolonged elimination of the injectedE. coli from the blood and in significantly higher (p<0.05) numbers of CFU in liver and lung compared to the controls. Significant impairment of bacterial clearance was found after shockproducing endotoxemia, whereas simultaneous infusion of NE and endotoxin caused only a slightly delayed blood clearance of the injected bacteria.

Conclusion

NE dose dependently affected bacterial clearance, which might be due to ischemia-derived hypoxic impairment of the phagocytosis and lysis function of the reticuloendothelial system, whereas NE improved elimination of bacteria in a state of endotoxic shock.     

Exploring the Effect of Asclepias curassavica on Markers of Oxidative Stress in Rats

Objective

Extract of the aerial part of Asclepias curassavica L. (Asclepiadaceae family) was screened for both in vitro and in vivo antioxidant activity.

Methods

Different concentrations of different extracts (chloroform, ethyl acetate, methanol and hydroalcohol) of A. curassavica were investigated for in vitro antioxidant activity using the thiocyanate method. The hydroalcoholic extract exhibited the highest inhibitory activity on peroxidation, over the other organic extracts, and was subjected to further in vivo antioxidant activity. Hydroalcoholic extract was administered to rats at two different doses of 250 and 500 mg/kg for 14 days to evaluate oxidative stress parameters such as ferric reducing ability of plasma (FRAP), thiobarbituric acid reactive substance (TBARS) and reduced glutathione (GSH) and to evaluate antioxidant enzyme levels of Superoxide dismutase (SOD) and catalase (CAT).

Results and Discussion

The IC₅₀ value (31.2 µg/mL) of hydroalcoholic extract was found to be less than the standard, α-tocopherol (IC₅₀ value 66.1 µg/mL). The hydroalcoholic extract significantly (p < 0.05) increased the FRAP on days 7 and 14 of treatment. Significant (p < 0.05) reduction of TBARS along with an increase in the SOD enzyme level in the liver and kidney at two different doses was observed. Treatment at a 500 mg/kg bodyweight dose caused a significant increase only in the level of CAT in the liver and kidney. However, there was no significant effect of TBARS, SOD and CAT in the heart, and the GSH level in liver, heart and kidney.

Conclusion

It can be concluded that the hydroalcoholic extract of A. curassavica had significant antioxidant activity, which might be helpful in preventing (or slowing) various oxidative stress-related diseases.     

High-volume versus standard-volume haemofiltration for septic shock patients with acute kidney injury (IVOIRE study): a multicentre randomized controlled trial

Purpose

Septic shock is a leading cause of death among critically ill patients, in particular when complicated by acute kidney injury (AKI). Small experimental and human clinical studies have suggested that high-volume haemofiltration (HVHF) may improve haemodynamic profile and mortality. We sought to determine the impact of HVHF on 28-day mortality in critically ill patients with septic shock and AKI.

Methods

This was a prospective, randomized, open, multicentre clinical trial conducted at 18 intensive care units in France, Belgium and the Netherlands. A total of 140 critically ill patients with septic shock and AKI for less than 24 h were enrolled from October 2005 through March 2010. Patients were randomized to either HVHF at 70 mL/kg/h or standard-volume haemofiltration (SVHF) at 35 mL/kg/h, for a 96-h period.

Results

Primary endpoint was 28-day mortality. The trial was stopped prematurely after enrolment of 140 patients because of slow patient accrual and resources no longer being available. A total of 137 patients were analysed (two withdrew consent, one was excluded); 66 patients in the HVHF group and 71 in the SVHF group. Mortality at 28 days was lower than expected but not different between groups (HVHF 37.9 % vs. SVHF 40.8 %, log-rank test p = 0.94). There were no statistically significant differences in any of the secondary endpoints between treatment groups.

Conclusions

In the IVOIRE trial, there was no evidence that HVHF at 70 mL/kg/h, when compared with contemporary SVHF at 35 mL/kg/h, leads to a reduction of 28-day mortality or contributes to early improvements in haemodynamic profile or organ function. HVHF, as applied in this trial, cannot be recommended for treatment of septic shock complicated by AKI.     

Carbamylated erythropoietin-FC fusion protein and recombinant human erythropoietin during porcine kidney ischemia/reperfusion injury

Purpose

To test the hypothesis that a carbamylated EPO-FC fusion protein (cEPO-FC) or recombinant human erythropoietin (rhEPO) would protect against kidney ischemia/reperfusion (I/R) injury in pigs with atherosclerosis.

Methods

Anesthetized and mechanically ventilated animals received cEPO-FC (50 μg kg^?1), rhEPO (5,000 IU kg^?1), or vehicle (n = 9 per group) prior to 120 min of aortic occlusion and over 4 h of reperfusion. During aortic occlusion, mean arterial pressure (MAP) was maintained at 80–120 % of baseline values by esmolol, nitroglycerin, and ATP. During reperfusion, noradrenaline was titrated to keep MAP at pre-ischemic levels. Blood creatinine and neutrophil gelatinase-associated lipocalin (NGAL) levels, creatinine clearance, fractional Na⁺ excretion, and HE and PAS staining were used to assess kidney function and histological damage. Plasma interleukin-6, tumor necrosis factor-α, nitrate + nitrite and 8-isoprostane levels were measured to assess systemic inflammation, and nitrosative and oxidative stress.

Results

I/R caused acute kidney injury with reduced creatinine clearance, increased fractional Na⁺ excretion and NGAL levels, moderate to severe glomerular and tubular damage and apoptosis, systemic inflammation and oxidative and nitrosative stress, but there were no differences between the treatment groups. Pre-ischemia nitrate + nitrite and 8-isoprostanes levels were lower and higher, respectively, than in healthy animals of a previous study, and immune histochemistry showed higher endothelial nitric oxide synthase and lower EPO receptor expression in pre-ischemia kidney biopsies than in biopsies from healthy animals.

Conclusions

In swine with atherosclerosis, rhEPO and cEPO-FC failed to attenuate prolonged ischemia-induced kidney injury within an 8-h reperfusion period, possibly due to reduced EPO receptor expression resulting from pre-existing oxidative stress and/or reduced NO release.     

Vasopressin in vasodilatory shock: hemodynamic stabilization at the cost of the liver and the kidney?

Infusing arginine vasopressin (AVP) in advanced vasodilatory shock is usually accompanied by a decrease in cardiac index and systemic oxygen transport. Whether or not such a vasoconstriction impedes regional blood flow and thus visceral organ function, even when low AVP is used, is still a matter of debate. Krejci and colleagues now report, in this issue of Critical Care, that infusing 'low-dose' AVP during early, short-term, normotensive and normodynamic fecal peritonitis-induced porcine septicemia markedly reduced both renal and portal blood flow, and consequently total hepatic blood flow, whereas hepatic arterial flow was not affected. This macrocirculatory response was concomitant with reduced kidney microcirculatory perfusion, whereas liver micro-circulation remained unchanged. From these findings the authors conclude that the use of AVP to treat hypotension should be cautioned against in patients with septic shock. Undoubtedly, given its powerful vasoconstrictor properties, which are not accompanied by positive inotropic qualities (in contrast with most of the equally potent standard care 'competitors', namely catecholamines), the safety of AVP is still a matter of concern. Nevertheless, the findings reported by Krejci and colleagues need to be discussed in the context of the model design, the timing and dosing of AVP as well as the complex interaction between visceral organ perfusion and function.     

Intravenous glutamine decreases lung and distal organ injury in an experimental model of abdominal sepsis

Introduction

The protective effect of glutamine, as a pharmacological agent against lung injury, has been reported in experimental sepsis; however, its efficacy at improving oxygenation and lung mechanics, attenuating diaphragm and distal organ injury has to be better elucidated. In the present study, we tested the hypothesis that a single early intravenous dose of glutamine was associated not only with the improvement of lung morpho-function, but also the reduction of the inflammatory process and epithelial cell apoptosis in kidney, liver, and intestine villi.

Methods

Seventy-two Wistar rats were randomly assigned into four groups. Sepsis was induced by cecal ligation and puncture surgery (CLP), while a sham operated group was used as control (C). One hour after surgery, C and CLP groups were further randomized into subgroups receiving intravenous saline (1 ml, SAL) or glutamine (0.75 g/kg, Gln). At 48 hours, animals were anesthetized, and the following parameters were measured: arterial oxygenation, pulmonary mechanics, and diaphragm, lung, kidney, liver, and small intestine villi histology. At 18 and 48 hours, Cytokine-Induced Neutrophil Chemoattractant (CINC)-1, interleukin (IL)-6 and 10 were quantified in bronchoalveolar and peritoneal lavage fluids (BALF and PLF, respectively).

Results

CLP induced: a) deterioration of lung mechanics and gas exchange; b) ultrastructural changes of lung parenchyma and diaphragm; and c) lung and distal organ epithelial cell apoptosis. Glutamine improved survival rate, oxygenation and lung mechanics, minimized pulmonary and diaphragmatic changes, attenuating lung and distal organ epithelial cell apoptosis. Glutamine increased IL-10 in peritoneal lavage fluid at 18 hours and bronchoalveolar lavage fluid at 48 hours, but decreased CINC-1 and IL-6 in BALF and PLF only at 18 hours.

Conclusions

In an experimental model of abdominal sepsis, a single intravenous dose of glutamine administered after sepsis induction may modulate the inflammatory process reducing not only the risk of lung injury, but also distal organ impairment. These results suggest that intravenous glutamine may be a potentially beneficial therapy for abdominal sepsis.     

In Vivo Magnetic Resonance Imaging of Transgenic Mice Expressing Human Ferritin

Objective

This study aims to produce the transgenic mice (TG) engineered for magnetic resonance imaging (MRI) studies based on the ubiquitous expression of ferritin MRI reporter gene in diverse tissues.

Procedures

Transgenic mice (TG) expressing myc-tagged human heavy chain ferritin (myc-hFTH) under the control of a ubiquitous CAG promoter were produced. The expression of myc-hFTH in diverse tissues of the myc-hFTH TG was assessed by RT-PCR, Western blotting, and immunohistochemistry. The iron accumulation and the deposition of ferritin aggregates in tissues of myc-hFTH TG and WT were analyzed by Prussian blue staining and transmission electron microscopy. The myc-hFTH TG (n?=?9) and wild-type mice (WT) (n?=?4) were subjected to MRI on 9.4 T MR scanner. An eight-point T ₂ ^* mapping was performed using a multiple gradient echo sequence, and T ₂ ^* value was estimated pixel by pixel by using a routine least-squares fitting algorithm.

Results

We generated the myc-hFTH TG expressing myc-hFTH in brain, heart, liver, lung, spleen, pancreas, kidney, and intestine. The myc-hFTH TG showed no apparent pathological symptoms and no histological changes compared to WT. The expression of myc-hFTH in the brain and liver tissues of myc-hFTH TG led to a significant decrease in T₂* values, as shown by noninvasive MRI, compared to WT (P?<?0.05, TG vs. WT).

Conclusions

This study demonstrates that the novel myc-hFTH TG, which expresses an MRI reporter in many tissues, would be a valuable animal model of FTH-based molecular imaging in which to study potential therapies for cell and tissue grafting using an MRI technique. These mice could also serve to study disease related with iron metabolism.     

Effects of different tidal volumes in pulmonary and extrapulmonary lung injury with or without intraabdominal hypertension

Purpose

We hypothesized that: (1) intraabdominal hypertension increases pulmonary inflammatory and fibrogenic responses in acute lung injury (ALI); (2) in the presence of intraabdominal hypertension, higher tidal volume reduces lung damage in extrapulmonary ALI, but not in pulmonary ALI.

Methods

Wistar rats were randomly allocated to receive Escherichia coli lipopolysaccharide intratracheally (pulmonary ALI) or intraperitoneally (extrapulmonary ALI). After 24?h, animals were randomized into subgroups without or with intraabdominal hypertension (15?mmHg) and ventilated with positive end expiratory pressure?=?5?cmH₂O and tidal volume of 6 or 10?ml/kg during 1?h. Lung and chest wall mechanics, arterial blood gases, lung and distal organ histology, and interleukin (IL)-1??, IL-6, caspase-3 and type III procollagen (PCIII) mRNA expressions in lung tissue were analyzed.

Results

With intraabdominal hypertension, (1) chest-wall static elastance increased, and PCIII, IL-1??, IL-6, and caspase-3 expressions were more pronounced than in animals with normal intraabdominal pressure in both ALI groups; (2) in extrapulmonary ALI, higher tidal volume was associated with decreased atelectasis, and lower IL-6 and caspase-3 expressions; (3) in pulmonary ALI, higher tidal volume led to higher IL-6 expression; and (4) in pulmonary ALI, liver, kidney, and villi cell apoptosis was increased, but not affected by tidal volume.

Conclusions

Intraabdominal hypertension increased inflammation and fibrogenesis in the lung independent of ALI etiology. In extrapulmonary ALI associated with intraabdominal hypertension, higher tidal volume improved lung morphometry with lower inflammation in lung tissue. Conversely, in pulmonary ALI associated with intraabdominal hypertension, higher tidal volume increased IL-6 expression.