Hemodynamics: Why Is It Important in Surgery?

Hemodynamics, or the measure of blood flow throughout the body, plays a significant role in surgical outcomes. Hemodynamic problems can result in complications such as hypertension, hypotension, and irregular heartbeat [1]. Unfortunately, surgery can trigger hemodynamic issues and, thus, endanger patients’ lives. Surgery’s impact on hemodynamics contributes to the 1 to 4% postoperative mortality rate reported in developed countries [2]. The postoperative mortality rate is even more striking among high-risk patients. Although they represent just 10% of surgical procedures performed under anesthesia, high-risk patients suffer 80% of perioperative deaths [3]. Research indicates that hemodynamic optimization could lower the death rate among high-risk patients [3].

Various aspects of surgery impact hemodynamics. For instance, anesthetic agents can be of particular concern because they lower heart rate and blood pressure [4]. This can be true regardless of whether patients receive reduced levels of anesthetic agents [4]. Even at lower doses, anesthesia can still impair peripheral neural function and have profound effects on the body’s hemodynamic responses [4]. Therefore, anesthesiologists are forced to strike a difficult balance between pain management and hemodynamic stability — both of which are crucial to a successful operation.

Another way that surgery can impact hemodynamics comes in the form of preoperative anxiety. Such anxiety is characterized by feelings of apprehension, nervousness, tension, fear, and discomfort before an operation [5]. Studies have found that high preoperative anxiety can affect hemodynamics by increasing mean heart rate, arterial pressure, and systolic blood pressure [5]. Helping patients control high preoperative anxiety is thus a way to ensure better hemodynamics during a procedure.

Lastly, the technique that a surgeon opts to use can also have significant implications for a patient’s hemodynamics. For instance, Parachuri and colleagues found that modified linear endoventricular patch plasty contributes to marked improvements in hemodynamic performance during surgical ventricular restoration, compared to another common technique, endoventricular circular patch plasty [6]. Surgeons should consider hemodynamics as early as the preoperative phase when they are weighing different surgical methods.

There are other ways that surgery can affect hemodynamics as well. Thus, it is clear that medical professionals must be proactive in addressing hemodynamic issues. One cornerstone of surgery is hemodynamic monitoring. Specifically, medical professionals should track articular and ventricular blood pressure every five minutes [7]. While non-intensive monitoring in the form of a blood pressure cuff is standard practice, high-risk patients may require more intensive monitoring techniques, such as arterial lines and Swan-Ganz catheters [Blair]. Providers should also use vasoconstrictors and fluids to maintain blood flow and perfusion pressure in safe zones, but in doing so, they should similarly make sure to avoid volume overload [2].

Admittedly, there continues to be significant disagreement among medical practitioners about the best way to optimize hemodynamics [2]. Nevertheless, hemodynamic optimization is associated with decreased time in the intensive care unit, increased cost-effectiveness, and better patient outcomes [3, 8]. Therefore, taking steps before and during surgery to properly manage hemodynamics is of the utmost importance.

References

[1] M. J. London, “Hemodynamic Management During Anesthesia in Adults,” UpToDate, Updated July 13, 2023. [Online]. Available: https://www.uptodate.com/contents/hemodynamic-management-during-anesthesia-in-adults.

[2] J. Fellahi et al., “Perioperative Hemodynamic Optimization: From Guidelines to Implementation—An Experts’ Opinion Paper,” Annals of Intensive Care, vol. 11, no. 58, pp. 1-10, April 2021. [Online]. Available: https://doi.org/10.1186/s13613-021-00845-1.

[3] M. Cannesson et al., “Hemodynamic monitoring and management in patients undergoing high risk surgery: a survey among North American and European anesthesiologists,” Critical Care, vol. 15, no. R197, pp. 1-11, August 2011. [Online]. Available: https://doi.org/10.1186/cc10364.

[4] T. Abbott and G. L. Ackland, “The Relationships between Anesthesia Hemodynamics and Outcomes,” in Perioperative Hemodynamic Monitoring and Goal Directed Therapy. Cambridge, United Kingdom: Cambridge University Press, 2014, ch.26, pp. 224-30. Accessed October 4, 2023. [Online]. Available: https://www.cambridge.org/core/books/perioperative-hemodynamic-monitoring-and-goal-directed-therapy/relationships-between-anesthesia-hemodynamics-and-outcome/E013D60714A976C872D32261CFD7DFA4.

[5] M. Tadesse et al., “The hemodynamic impacts of preoperative anxiety among patients undergoing elective surgery: An institution-based prospective cohort study,” International Journal of Surgery Open, vol. 42, pp. 1-11, June 2022. [Online]. Available: https://doi.org/10.1016/j.ijso.2022.100490.

[6] V. Rao Parachuri & S. M. Adhyapak, “The Impact of Surgical Technique on Cardiac Hemodynamics Following Surgical Ventricular Restoration,” in Ventricular Geometry in Post-Myocardial Infarction Aneurysms. London: Springer-Verlag, 2012, ch.9, pp. 95-111. Accessed October 4, 2023. [Online]. Available: https://doi.org/10.1007/978-1-4471-2861-8_9.

[7] G. J. Blair, “Hemodynamic Monitoring in the Operating Room,” Medscape, Updated March 11, 2022. [Online]. Available: https://emedicine.medscape.com/article/2500066-overview.

[8] J. M. Silva-Jr. et al., “Impact of perioperative hemodynamic optimization therapies in surgical patients: economic study and meta-analysis,” BMC Anesthesiology, vol. 20, no. 71, pp. 1-12, 2020. [Online]. Available: https://doi.org/10.1186%2Fs12871-020-00987-y.

Hemodynamics: What Does It Mean?

There are two common meanings of hemodynamics. Sometimes, when they say “hemodynamics,” people are referring to the fundamental measures of cardiovascular function [1]. Other times, it describes how well the blood flows through the veins and arteries of the body [1, 2]. As the latter definition is the more technical one and, thus, more consistent with professional usage, this article will center on hemodynamics as the description of blood flow.

How Does Blood Flow Through the Body?

As the heart beats, it pushes blood into the vessels, which creates a pressure difference between the atrial inlet and the ventricular outlet [3, 4, 5]. As occurs with all fluids, blood moves from high-pressure to low-pressure zones [6]. Therefore, as pressure increases in a given area, blood flow away from that area increases [4]. This is how blood flows from the heart to the arteries, capillaries, veins, and the heart once more [6].

Along with pressure, systemic resistance also affects hemodynamics [4]. The more resistance that blood vessels pose to the blood, the more difficult it will be for blood to pass through those vessels [4]. Consequently, the shape and size of vessels can impede or promote hemodynamic stability as well [4].

What Conditions Affect Hemodynamics?

Many medical conditions can impact hemodynamic stability. Cardiovascular conditions, such as age-related vascular disease and pulmonary hypertension, can impede blood flow [4]. Anxiety and stress can also have a negative effect on the body’s hemodynamics, given how these conditions are often associated with elevated blood pressure which, in turn, increases the load borne by the heart [4]. Substances that affect blood pressure, like aldosterone and angiotensin (I and II), may have an effect as well [4].

That said, it is important to dispel a common misconception. While high blood pressure can compromise hemodynamic instability, the measure of hemodynamics depends on more than just blood pressure [1, 2]. Therefore, the two concepts —blood pressure and hemodynamics— are not synonymous and should not be conflated [2].

What Are the Symptoms of Hemodynamic Instability?

The cardiovascular system is vital to the body and is linked to several other organ systems as well. Hemodynamic instability is a potentially dangerous situation that must be monitored and treated as best as possible. Common symptoms of hemodynamic instability include decreased urine output; cold or blue legs, feet, arms, or hands; chest pain; shortness of breath; restlessness; low blood pressure; abnormal heart rate; confusion; and loss of consciousness [7]. Because many of these symptoms are associated with other medical conditions as well, medical professionals may use hemodynamic monitoring tests to verify whether hemodynamic

instability is the true cause of their patient’s symptoms [8]. It is a non-invasive procedure that can be done in around three hours and permits professionals to identify and address problem areas [8].

Why Are Hemodynamics Important?

Blood plays several key roles in the body. It regulates metabolism, enables the immune system to protect against foreign bodies, and boosts energy [5]. Hemodynamic instability compromises the blood’s ability to supply these benefits [2]. As a result, it is a serious condition that warrants treatment.

References

[1] J. Fletcher, “What to Know About Hemodynamic Instability,” Medical News Today, Updated March 29, 2023. [Online]. Available: https://www.medicalnewstoday.com/articles/hemodynamic-instability.

[2] “Hemodynamics,” Cleveland Clinic, Updated August 9, 2022. [Online]. Available: https://my.clevelandclinic.org/health/body/24013-hemodynamics.

[3] “How Does Blood Flow Through Your Body,” Cleveland Clinic, Updated April 30, 2019. [Online]. Available: https://my.clevelandclinic.org/health/articles/17059-how-does-blood-flow-through-your-body.

[4] J. D. Pollock et al., “Physiology, Cardiovascular Hemodynamics,” StatPearls, Updated March 13, 2023. [Online]. Available: https://www.ncbi.nlm.nih.gov/books/NBK470310/.

[5] M. Thiriet, “Hemodynamics: An Introduction,” in PanVascular Medicine. Berlin, Germany: Springer-Verlag Berlin Heidelberg, 2015, ch.14, pp. 413-83. Accessed September 26, 2023. [Online]. Available: https://doi.org/10.1007/978-3-319-50610-4_3.

[6] “Physiology of Circulation,” National Cancer Institute. [Online]. Available: https://training.seer.cancer.gov/anatomy/cardiovascular/blood/physiology.html.

[7] “Hemodynamic Instability,” University of Miami Health System. [Online]. Available: https://umiamihealth.org/en/treatments-and-services/pediatrics/critical-care-(pediatrics)/hemodynamic-instability.

[8] “Hemodynamics Test,” Cleveland Clinic, Updated August 10, 2022. [Online]. Available: https://my.clevelandclinic.org/health/diagnostics/17094-hemodynamic-test.