Assessment and monitoring of cardiac function in the pediatric intensive care unit (PICU) is an integral part of hemodynamic monitoring of critically ill patients whether it is done directly or indirectly. Measurement of cardiac output (CO) can specifically guide therapies to support the cardiovascular system in critically ill children with multi organ dysfunction. Because of the side effects involved in measuring cardiac output directly, intensive monitoring of patients is currently limited to an integrated assessment of tissue perfusion, oxygen delivery and cellular health both at regional and global levels. Currently available methods of measuring CO have their limitations and complications, and are not used routinely for bedside monitoring. Therefore, the investigators propose to use a newly developed method, termed COstatus for the monitoring of CO in patients admitted to PICU.

Inclusion Criteria:

1. Patients under 21 years
2. Presence of compensated or decompensated shock irrespective of etiology
3. Presence of an existing peripheral arterial and central venous catheters

Exclusion Criteria:

1. Patients allergic to heparin

Pediatric Patients (under 21 years of age) in the ICU