Secondary end points: infection during admission, mortality rate within 28 days. Definition of infection: 1) bacteremia：positive blood culture, but no definite focus indentified, 2) spontaneous bacterial peritonitis : ascites routine: PMN> 250/mm3, 3)urinary tract infection: U/A WBC > 15/HPF and positive urine culture, 4)other infections: suspected by clinical, radiological or other bacterialogical examination, 5)respiratory tract infection:CXR changes with clinical evidence, 6)possible infection: fever (>37.5。C more than 6 hours) and leucocytosis,WBC > 15000 mm3 ，but with negative blood culture