PiCCO has been widely used in critical care settings for several decades. Together with pulmonary artery catheter, it is regarded as the important tool for guiding fluid management in patients with shock or acute respiratory distress syndrome. However, its effects on patients' outcome remain untested. The investigators study is a pilot study that is designed to test whether the use of PiCCO will improve patients' outcome, as compared to those without PiCCO monitoring.

PiCCO comprises techniques of pulse contour analysis and transpulmonary thermodilution, and can provide important information on hemodynamics and pulmonary functions. It has been widely used in critical care settings for several decades. Together with pulmonary artery catheter (PAC), it is regarded as the important tool for guiding fluid management in patients with shock or acute respiratory distress syndrome. During last two decades, many well designed clinical trials have been conducted to see whether the use of PAC would benefit patient outcome. The result consistently showed that PAC added no benefit in terms of mortality, ICU length of stay, organ failure free survival days, and the length of mechanical ventilation. Since PiCCO is relatively new to PAC, and its effects on patients' outcome remain untested. The investigators study is a pilot study that is designed to test whether the use of PiCCO will improve patients' outcome, as compared to those without PiCCO monitoring.

Inclusion Criteria:

Patients were included if they were diagnosed with Shock, Acute respiratory distress syndrome (ARDS), or both.

Shock was defined by the presence 4 criteria:

• Heart rate of at least 90/min;
• A respiratory rate of at least 20/min or a PaCO2 of 32mmHg or lower or the use of mechanical ventilation;
• The use of vasopressors to maintain a systolic blood pressure of at least 90mmHg despite fluid resuscitation, low dose of dopamine (≤ 5 μg/kg per minute), or dobutamine;
• at least 1 of 3 signs of hypoperfusion (urine output < 0.5mL/kg of body weight per hour for 1 hour or more; neurologic dysfunction defined by confusion, psychosis, or a Glasgow coma scale score of ≤ 6; plasma lactate higher than the upper limit of the normal value).

Acute respiratory distress syndrome：

• the presence of acute decrease in PaO2/FIO2 to 200mmHg or lower,
• bilateral pulmonary infiltrates or a chest radiograph consistent with edema;
• no clinical evidence of left atrial hypertension; and requirement for positive pressure ventilation.

Exclusion Criteria:

• Patients were moribund.
• signed do-not-resuscitation odor.