Heart Rate Variability (HRV): Health, Stress and Anesthetic Implications

Heart rate variability (HRV) represents the changes in intervals between consecutive heartbeats, as well as the changes in intervals between heart rates.¹ According to contemporary research, HRV is related to heart and brain health, including psychological stress, neurological function, physical reactions and cardiac activity.² HRV interacts with these processes in a variety of ways, often becoming part of a feedback loop.² Not only do changes in HRV represent changes in various bodily systems, but they also have implications for diagnoses and prognoses.³ Specifically, HRV plays a role in anesthesia induction and perioperative care.⁴ HRV is related to overall health, as well as stressors both outside and inside the operating room.

HRV represents the complexity of systems biology, which is an interdisciplinary field focusing on the interactions within and between biological systems.² Through these interactions come alterations in HRV, which may cause further changes in bodily systems.² Many researchers have studied the relationship between HRV and various body health factors. For example, HRV decreases with aging.⁵ Faster heart rates are also related to lower HRV, as a reduction in time between beats allows for less variation in inter-beat intervals.⁶ Low HRV is associated with numerous health issues, including inflammation, chronic pain, diabetes, concussion, asthma, insomnia and fatigue, all of which indicate imbalances in the autonomic nervous system (ANS).⁶ On the other hand, increased HRV is related to better aerobic fitness⁷ and reduced cardiovascular disease risk.⁸ Though HRV has clear links to the heart, it is also closely related to other body systems.

The relationship between HRV and physical health is not straightforward, but rather tied to psychological and neurological health.² Modern systems biology theories suggest a close connection between psychologically and emotionally stressful events, ANS dysfunction and HRV.² The polyvagal theory, for example, suggests that stressful events cause altered physiological states (i.e., issues with the ANS), which then affect behaviors and psychological experiences that perpetuate the cycle.² Meanwhile, the neurovisceral integration model proposes that HRV represents the functionality of neurological systems implicated in emotion–cognition interactions.² Both theories suggest that physical health, emotional stressors and HRV are related. According to two meta-analyses on the neurobiology of HRV, HRV is impacted by stress⁹ and serves as a proxy of the brain’s response to threat.¹⁰ A study by Delaney and Brodie found that short-term psychological stress changed the time and frequency domains of HRV.¹¹ Another study by Kang et al. showed that male shipyard workers who felt high job strain had decreased HRV compared to the low strain group.¹² Three more studies found that difficult mental tasks and stressful computer work temporarily decreased HRV.^13-15 In a treatment study, Satyapriya et al. found that women who did one hour of daily yoga throughout their pregnancies had lower perceived stress and higher HRV than women who did not.¹⁶ Research shows there are concrete associations between stress and HRV, though the long-term implications remain unclear.

Because of its ties to the ANS, general health and psychological stress, HRV may be a useful indicator for anesthesia providers. ANS dysfunction may complicate the perioperative period by reducing homeostasis and increasing morbidity and mortality.³ Given research relating ANS dysfunction and low HRV, anesthesiology practitioners may use HRV to assess a patient’s risk for ANS-related complications.⁶ For example, Hanss et al. found that ratios of high- to low-frequency HRV predicted severe hypotension after spinal anesthesia in 100 male patients.¹⁷ HRV may also change based on type of anesthesia, indicating that certain anesthetic drugs may cause less ANS stress during surgery.¹⁸ HRV plays a role in health and bodily responses, so it may be a helpful tool for preventing complications or reducing stress.

There is a complex interaction between bodily systems and HRV. Systems biology shows us that HRV is related to a variety of physical health conditions, as well as psychological and emotional stress. Anesthesia providers can use this relationship between HRV, stress and health to their advantage throughout the perioperative period. Future research should explore the long-term conditions associated with temporary changes in HRV, along with the types of anesthesia that have fewer intraoperative effects on HRV.

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3.         Mazzeo AT, La Monaca E, Di Leo R, Vita G, Santamaria LB. Heart rate variability: A diagnostic and prognostic tool in anesthesia and intensive care. Acta Anaesthesiologica Scandinavica. 2011;55(7):797–811.

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11.       Delaney JPA, Brodie DA. Effects of Short-Term Psychological Stress on the Time and Frequency Domains of Heart-Rate Variability. Perceptual and Motor Skills. 2000;91(2):515–524.

12.       Kang MG, Koh SB, Cha BS, Park JK, Woo JM, Chang SJ. Association between Job Stress on Heart Rate Variability and Metabolic Syndrome in Shipyard Male Workers. Yonsei Medical Journal. 2004;45(5):838–846.

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17.       Hanss R, M.D., Bein B, M.D., Weseloh H, M.S., et al. Heart Rate Variability Predicts Severe Hypotension after Spinal Anesthesia. Anesthesiology: The Journal of the American Society of Anesthesiologists. 2006;104(3):537–545.

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