 We propose to conduct this prospective observational study in the surgical and medical ICUs of 2 hospitals in Singapore. Singapore General Hospital and Changi General Hospital We aim to enrol 112 of you admitted to the ICU with shock of any etiology. Shock is defined as persistence of arterial hypotension despite adequate volume resuscitation. Hypotension is defined as systolic pressure 90mmHg, Mean arterial pressure MAP70 mmHg or drop in SBP 40 mmHg from baseline. 30mlkg of fluid is considered as the threshold for adequate volume resuscitation. 