Haemodynamic Monitoring
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Top Contributors - Narayani Nagare, Rachael Lowe, Rana Muhammad Tahir Aslam and Mahbubur Rahman
Haemodynamic Monitoring
Haemodynamics refers to the study of dynamics of blood flow. Monitoring of haemodynamics is a cornerstone in managing critically ill patients, particularly those with cardiovascular instability. It involves the measurement and interpretation of physiological parameters that reflect cardiovascular function such as cardiac output, blood pressure, and vascular resistance. This information helps clinicians optimise oxygen delivery and tissue perfusion, guiding therapeutic decisions in real-time. Advancements in technology have widened haemodynamic monitoring from conventional invasive to non-invasive and minimal invasive approaches, thereby widening the scope of applicability for these procedures across different clinical settings.[1][2]
Principles of Haemodynamic Monitoring
Haemodynamic monitoring focuses on three fundamental components of the cardiovascular system:
Preload: The volume of blood returning to the heart, which influences end-diastolic volume.
Afterload: The resistance the heart must work against to pump blood.
Contractility: The inherent force of heart muscle contraction independent of preload and afterload.
These principles of understanding and managing conditions as hypovolemia, heart failure, and shock work as a framework [2]. Monitoring is effective when based on parameters such as stroke volume, cardiac output, and systemic vascular resistance because it guides therapeutic interventions adjusted to the patient's status.
Techniques of Haemodynamic Monitoring
Non-Invasive Monitoring
Low-risk, easy-to-apply methods are increasingly applied:
Blood Pressure Measurement: Routine measurement is provided by automated oscillometric devices that are widely used in clinical practice [1].
Doppler Ultrasound: Measures blood flow velocity and estimates stroke volume. Portable devices can assess cardiac output and detect abnormalities in real time [3].
Bioimpedance and Bioreactance: It calculates cardiac output by detecting thoracic electrical conductivity variations associated with the cardiac cycle [4].
Minimally Invasive Monitoring
Minimally invasive monitoring balances the advantages of accuracy with the benefits of reducing the risk to patients:
Arterial Pressure Waveform Analysis: It monitors cardiac output and stroke volume through arterial line waveforms in high-risk surgery settings [5].
Esophageal Doppler: This probe inserted in the esophagus assesses blood flow in the descending aorta and offers valid stroke volume estimates [6].
Invasive Monitoring
Invasive monitoring is still the gold standard, but at a greater risk:
Pulmonary Artery Catheter (PAC): Pulmonary artery pressure, cardiac output, and mixed venous oxygen saturation can be measured with this catheter. Even though it is an invasive monitoring tool, it still finds great utility in complex cases like cardiogenic shock and multi-organ failure [7].
Central Venous Catheter (CVC): Studies central venous pressure (CVP) and central venous oxygen saturation (ScvO2), which steer fluid therapy and optimize the delivery of oxygen [8].
For more information on the central venous catheter watch this Video:
Clinical Applications
Septic Shock
Haemodynamic monitoring is an essential part of managing septic shock, in which impaired perfusion leads to organ dysfunction. Techniques such as ScvO2 monitoring and dynamic indices like pulse pressure variation guide fluid resuscitation and vasopressor administration [9].
Heart Failure
In acute decompensated heart failure, monitoring cardiac output and preload helps in assessing fluid status and the need for inotropic support. PAC can be used in advanced cases to guide therapy [10].
Surgical and Perioperative Care
Monitoring ensures hemodynamic stability during high-risk surgeries and in the postoperative period. Arterial waveform analysis and esophageal Doppler are common tools in perioperative settings [5].
Trauma and Hemorrhagic Shock
In trauma patients, hemodynamic monitoring detects hypovolemia which guides fluid and blood product delivery. Some useful techniques employed for the prediction of the fluid responsiveness are passive leg rising tests among others [11].
Limitations and Challenges
Despite its advantages, there are challenges to haemodynamic monitoring. Invasive procedures lead to complications such as infection, thrombosis, and pneumothorax. In unstable or obese patients, it lacks precision with the non-invasive methods. Clinical skill is also needed for its interpretation because the parameters may be confounded by many variables including the comorbidities and medication of the patient. [4][8]
References
- ↑ 1.0 1.1 Cecconi M, De Backer D, Antonelli M, et al. Consensus on circulatory shock and haemodynamic monitoring. Intensive Care Med. (2014)
- ↑ 2.0 2.1 Vincent JL, De Backer D. Circulatory shock. N Engl J Med. 2013;369(18):1726-1734.
- ↑ Monnet X, Teboul JL. Assessment of volume responsiveness during mechanical ventilation: trends in critical care. Crit Care. 2010.
- ↑ 4.0 4.1 Funk DJ, Parrillo JE, Kumar A. Sepsis and septic shock: a history. Crit Care Clin. 2009
- ↑ 5.0 5.1 Thiele RH, Bartels K, Gan TJ. Cardiac output monitoring: a contemporary assessment and review. Crit Care Med. 2015;43(1):177-185.
- ↑ Singer M, Deutschman CS, Seymour CW, et al. The third international consensus definitions for sepsis and septic shock (Sepsis-3). JAMA. 2016;315(8):801-810.
- ↑ Pulido JN, Krishnan SJ, Gilbertson DT, et al. The role of pulmonary artery catheters in contemporary clinical practice. Ann Card Anaesth. 2013
- ↑ 8.0 8.1 Teboul JL, Monnet X. Assessing fluid responsiveness in septic shock: don't let the easy stuff fool you! Crit Care. 2009
- ↑ Rhodes A, Evans LE, Alhazzani W, et al. Surviving Sepsis Campaign: international guidelines for management of sepsis and septic shock 2016. Intensive Care Med. 2017
- ↑ Gheorghiade M, Pang PS. Acute heart failure syndromes. J Am Coll Cardiol. 2009
- ↑ Marik PE, Cavallazzi R. Does the central venous pressure predict fluid responsiveness? A systematic review of the literature and the tale of seven mares. Chest. 2008