Circulatory failure in critically ill children is a common pathophysiological state.Timely identification of its causes,hemodynamic monitoring and appropriate intervention are essential to block the process of circulatory failure and reduce mortality.In this review,some of the most important hemodynamic parameters that can be obtained by the bedside echocardiography were described and some important issues during the application of bedside echocardiography were discussed.

Pediatric viral encephalitis is very common,and one of the important causes of death in PICU. Timely and appropriate diagnosis,empiric and supportive treatments are the key in reducing mortality of this diseases. We reviewed the epidemiology,diagnosis,reasons for PICU admission and treatments in this article.

The pathology, clinical manifestation, radiologic changes and pulmonary mechanics are more complicated in pneumonia induced ARDS than in other extrapulmonary origins. Heterogeneity is obvi-ous with increased respiratory tract resistance and decline of lung compliance. The injury of both tract and alveoli is more severe including airleak,pulmonary hemorrhage,pulmonary edema etc. Lung protective strate-gy should be followed in ventilatory support,but in some cases this will not work,thus individual treatment should be performed accordingly. In addition,clinical diagnosis of ARDS according to Berlin definition is not real ARDS pathologically, some cases are simply pneumonia, therefore treatment for ARDS is not always working. Integrity treatment is needed in pneumonia induced ARDS including antibiotics and other organ sup-port.

Acute respiratory distress syndrome(ARDS) is a disease of acute onset characterized by hypoxemia and infiltrates on chest radiographs that affects both adults and children of all ages.This article reviewed the evolution of the definition of ARDS over nearly five decades,with a special focus on the new pediatric definition,also discuss recommendations for future definition of this syndrome.

Sepsis is one of leading cause of death in children.Consistent high morat lity is associated with unclear understanding of pathophysiology of sepsis.Low sensitivity and specificity have been encoun-tered in definition of sepsis.Therefore,new defin ition will be developed which defines sepsis as infection plus organ dysfunction.

The causes of heart failure(HF) are significantly different from adults in children,and the management of children with HF uausally follows the results of researches in adults.Attention should be payed to the developments of diagnosis and management in the field of HF,especially treatment strategy has been changed from hymodynamic to nuroendocrinology modulation.In addition,device therapy in HF predominantly including pacemaker therapy,cardiac resynchronization therapy,continuous renal replacement therapy and mechanical circulatory support is recommended in severe cases.

Pneumonia is a common morbidity and a leading cause of death of measles.Severe measles pneumonia is often complicated with acute respiratory distress syndrome,air-leak and bronchitis obliterans.Appropriate respiratory support and other supportive treatment are important in reducing mortality of measles.

Severe hand,foot and mouth disease has emerged as the important threat to lives of children in China in recent years. Enterovirus especially EV 71 is neurotropic pathogen, can cause encephalitis,brainstem encephalitis, which are considered to be related to some severe complications such as pulmonary edema and cardiovascular failure. Autonomic nervous system dysregulation and secondary excessive catecholamine release are thought to be the main mechanism. The key measures for decreasing mortality include optimal ventilatory and cardiovascular support as well as prevention of further brain injuries. The guideline should be used with cautions and clinical practice should be based on patient's conditions.

Ventilator has been playing very important role in reducing morbidity and mortality of patients with respiratory failure.Physician should not only be familiar with ventilator,but have good knowledge about lung mechanics and pathophysiology of various diseases,and use the ventilator effectively accordingly.

Septic shock may have a lasting effect on all human endocrinologic, coagulatory and metabolic regulatory circuits with the consequence of severe dysregulation of homoeostasis.Adjunctive therapeutic options like correction of metabolic acidosis, intensive insulin therapy, and modulation of coagulation by drotrecogin alfa (activated) are still controversial.However, these adjunctive therapeutic options should be selected according to the national and international guidelines.