From the Guidelines
Haemodynamics in critical care is the study and management of blood flow throughout the cardiovascular system in critically ill patients, with the primary goal of ensuring adequate tissue perfusion and oxygen delivery while preventing organ dysfunction. This involves monitoring and optimizing key parameters such as blood pressure, cardiac output, heart rate, stroke volume, systemic vascular resistance, and oxygen delivery to tissues 1. Critical care clinicians use various tools to assess haemodynamic status, including invasive monitoring techniques like arterial lines, central venous catheters, and pulmonary artery catheters, as well as non-invasive methods such as echocardiography and pulse contour analysis.
The management of haemodynamics in critical care often requires careful fluid administration, vasopressor medications, inotropes, or vasodilators depending on the patient's specific haemodynamic derangements 1. For example, norepinephrine is recommended as the first-line vasopressor agent to maintain adequate organ perfusion pressure in patients with septic shock, with a dose range of 0.01-0.5 μg/kg/min 1. The optimal approach is to use an individualized mean arterial pressure (MAP) target based on frequent assessment of end-organ perfusion, with a recommended target of 65 mm Hg in septic shock and general ICU patients 1.
Key parameters to monitor in haemodynamic management include:
- Blood pressure
- Cardiac output
- Heart rate
- Stroke volume
- Systemic vascular resistance
- Oxygen delivery to tissues
- Urine output
- Serum lactate clearance
- Mixed or central venous oxygen saturations
- Skin perfusion
- Renal and liver function tests
- Mental status
Understanding haemodynamics is crucial because it guides treatment decisions in conditions like septic shock, cardiogenic shock, hypovolemia, and other critical illnesses where cardiovascular compromise threatens organ function and patient survival 1. The use of vasoactive drugs titrated to specific targets, such as mean arterial pressure and lactate clearance, can help optimize perfusion to vital organs and ensure adequate cellular delivery of oxygen 1.
From the Research
Definition of Haemodynamics in Critical Care
Haemodynamics in critical care refers to the study of blood flow, blood pressure, and the circulatory system's function in critically ill patients. It involves evaluating and managing circulatory failure, which is one of the most challenging tasks for medical practitioners in critical care medicine 2. Understanding haemodynamics is crucial in critical care as it helps in assessing and managing patients with failing circulation.
Key Concepts in Haemodynamics
Some key concepts in haemodynamics include:
- Organ blood flow: measuring the blood flow to different organs in the body
- Circulating volume: measuring the amount of blood in the circulatory system
- Hemodynamic biomarkers of shock: measuring indicators of shock, such as blood pressure and lactate levels
- Tissue oxygenation: measuring the amount of oxygen being delivered to tissues
Monitoring Haemodynamics in Critical Care
Haemodynamic monitoring is essential in critical care, and various techniques are used, including:
- Clinical signs of hypoperfusion and arterial pressure
- Echocardiography
- Noninvasive and minimally invasive tools, such as transpulmonary thermodilution and pulmonary arterial catheter
- Tissue perfusion pressure (TPP) measurement, which provides unique information compared to other hemodynamic parameters 3
Management of Haemodynamic Shock
Managing haemodynamic shock involves using vasopressors and inotropes to increase systemic vascular resistance and cardiac contractility, respectively 4. The choice of technique for assessing preload, afterload, cardiac output, and global systemic perfusion should be guided by specific evidence and local expertise 5. Advanced hemodynamic monitoring can help establish goals that take into account cerebral blood flow and oxygenation, which vary depending on diagnosis and disease stage.
Importance of Haemodynamics in Critical Care
Haemodynamics plays a critical role in critical care, as it helps in assessing and managing patients with circulatory failure. Understanding haemodynamics is essential for medical practitioners to make informed decisions about patient care and to improve patient outcomes 6. Further research is needed to understand the potential of haemodynamic monitoring for therapeutic interventions and prognostication 5.