Fluids in acute respiratory distress syndrome: pros and cons

Kidney-lung connections in acute and chronic diseases: current perspectives

Lung and kidney functions are intimately related in both health and disease. The regulation of acid-base equilibrium, modification of partial pressure of carbon dioxide and bicarbonate concentration, and the control of blood pressure and fluid homeostasis all closely depend on renal and pulmonary activities. These interactions begin in fetal age and are often responsible for the genesis and progression of diseases. In gestational age, urine is a fundamental component of the amniotic fluid, acting on pulmonary maturation and growth. Moreover, in the first trimester of pregnancy, kidney is the main source of proline, contributing to collagen synthesis and lung parenchyma maturation. Pathologically speaking, the kidneys could become damaged by mediators of inflammation or immuno-mediated factors related to a primary lung pathology or, on the contrary, it could be the renal disease that determines a consecutive pulmonary damage. Furthermore, non immunological mechanisms are frequently involved in renal and pulmonary diseases, as observed in chronic pathologies such as sleep apnea syndrome, pulmonary hypertension, progressive renal disease and hemodialysis. Kidney damage has also been related to mechanical ventilation. The aim of this review is to describe pulmonary-renal interactions and their related pathologies, underscoring the need for a close collaboration between intensivists, pneumologists and nephrologists.

Regulation of inflammatory biomarkers by intravenous methylprednisolone in pediatric ARDS patients: Results from a double-blind, placebo-controlled randomized pilot trial

OBJECTIVE

A double-blind, randomized controlled trial showed that low-dose glucocorticoid therapy in pediatric ARDS patients is feasible and may improve both ventilation and oxygenation indices in these patients. However, the molecular mechanisms underlying potential changes in outcomes remain unclear. Based on these clinical findings, this study was designed to examine the effects of intravenous methylprednisolone on circulating inflammatory biomarkers in pediatric ARDS patients.

DESIGN

Double-blind, placebo-controlled randomized trial with blood collection on study entry and day 7.

SETTING

Tertiary care children's hospital.

PATIENTS

Children (0-18years) with ARDS undergoing mechanical ventilation.

INTERVENTIONS

35 children were randomized within 72h of mechanical ventilation. The glucocorticoid group received methylprednisolone 2mg/kg loading dose followed by 1mg/kg/day continuous infusion from days 1 to 7. Both groups were ventilated following the ARDSnet recommendations. WBC and differential cell counts, plasma cytokines and CRP levels, and coagulation parameters were analyzed on days 0 and 7.

RESULTS

At study entry, the placebo group had higher IL-15 and basophil levels. On day 7, in comparison to study entry, the placebo group had lower IL-1α, IFN-γ and IL-10 levels. The glucocorticoid group had lower INF-α, IL-6, IL-10, MCP-1, G-CSF and GM-CSF levels, and higher IL-17α levels on day 7 in comparison to study entry. Total and differential cell counts remained unchanged within the placebo group between days 0 and 7, whereas in the glucocorticoid group total WBC and platelets counts were increased on day 7. Pearson's correlation studies within the placebo and glucocorticoid groups revealed positive and negative correlations between cytokine levels, cell counts, coagulation parameters and relevant clinical parameters of disease severity identified in our previous study. Multiple regression models identified several cytokines as predictors for alterations in clinical parameters of disease severity.

CONCLUSION

This pilot study shows the feasibility of simultaneously measuring multiple inflammatory cytokines, cell counts and coagulation parameters in pediatric ARDS patients. We report statistical models that may be useful for future, larger trials to predict ARDS severity and outcomes.

Restrictive Fluid Resuscitation Leads to Better Oxygenation than Non-Restrictive Fluid Resuscitation in Piglets with Pulmonary or Extrapulmonary Acute Respiratory Distress Syndrome

BACKGROUND

Early goal-directed therapy (EGDT) is used to reduce mortality from septic shock and could be used in early fluid resuscitation of acute respiratory distress syndrome (ARDS). The aim of the present study was to assess the effects of restrictive (RFR) and nonrestrictive fluid resuscitation (NRFR) on hemodynamics, oxygenation, pulmonary function, tissue perfusion, and inflammation in piglets with pulmonary or extrapulmonary ARDS (ARDSp and ARDSexp).

MATERIAL AND METHODS

Chinese miniature piglets (6-8 weeks; 15 ± 1 kg) were randomly divided into 2 groups (n=12/group) for establishing ARDSp and ARDSexp models, and were further divided into 2 subgroups (n=6/subgroup) for performing RFR and NRFR. Piglets were anesthetized and hemodynamic, pulmonary, and oxygenation indicators were collected at different time points for 6 hours. The goal of EGDT was set for PiCCO parameters (mean arterial pressure (MAP), urine output and cardiac index (CI), and central venous oxygen saturation (ScvO2).

RESULTS

Piglets under RFR had lower urine output compared with NRFR, as well as lower total fluid volume (P<0.05). EVLW was decreased in ARDSp+RFR and NRFR, as well as in ARDSexp+RFR, but EVLW increased in ARDSexp+NRFR (P<0.05). PaO2/FiO2 decreased in ARDSp using both methods, but was higher with RFR (P<0.05), and was increased in ARDSexp+RFR. Other pulmonary indicators were comparable. The anti-inflammatory cytokines IL-10 and LXA4 were increased in ARDSexp after RFR (P<0.05), but not in the other groups.

CONCLUSIONS

RFR led to better oxygenation in ARDSp and ARDSexp compared with NRFR, but fluid restriction improved oxygenation in ARDSexp only.