Nutrition and vasoactive substances in the critically ill patient

Background The most common cause of haemodynamic instability (a disturbance of the forces involved in circulating blood through the body) in the critically ill patient is a state of shock, whether it is hypovolaemic, cardiogenic or distributive (septic, anaphylactic or neurogenic) shock. Although the causes of the state of shock differ, the result is the same: decrease in cardiac output and insufficient tissue perfusion; hence haemodynamic instability. Interventions, including fluid therapy and the administration of vasoactive substances like vasopressors (increase in the vascular tone) and inotropic substances (increase in myocardial contraction) to restore homeostasis (haemodynamic stability), are of critical importance to prevent further deterioration.