This prospective observational study aims to (i) asses intensive care doctors trigger for and the expected physiological response to a fluid bolus and (ii) evaluate the patient's actual physiological response to a single fluid bolus at one hour post-bolus for 100 adult patients admitted to the intensive care unit will be included in the study.

Intensive care unit patients often receive a fluid bolus during their ICU-stay. ICU doctors use a variety of clinical triggers when deciding whether or not to give a fluid bolus. However, the type of physiological triggers used and their correlation to the anticipated physiological response of the patient to an administered fluid bolus is not entirely clear.

The investigators will perform a prospective observational study to evaluate the triggers for, expected physiological and actual physiological response to fluid bolus therapy in the intensive care unit. Specifically, the investigators will assess which of the the physiological trigger(s) intensive care doctors use when deciding to give a fluid bolus; the expected physiological response to the fluid bolus by intensive care doctors; and, to what degree the patients actual physiological response 1 hour after a fluid bolus correlate with expectations.

This study will involve a survey of ICU physicians to determine the physiological trigger and expectations and a medical audit to ascertain the physiological response to a fluid bolus. The investigators will evaluate a single fluid bolus in 100 separate intensive care unit patients.

Inclusion Criteria:

• Patients admitted to the intensive care unit and prescribed a fluid bolus.

Exclusion Criteria:

• The intensive care physician declines to participate.
• Expected survival < 24h

Hypovolemic critically ill patients in the intensive care unit.