Anesthesia-Associated Relative Hypovolemia: Mechanisms, Monitoring, and Treatment Considerations

Abstract

Although the utility and benefits of anesthesia and analgesia are irrefutable, their practice is not void of risks. Almost all drugs that produce anesthesia endanger cardiovascular stability by producing dose-dependent impairment of cardiac function, vascular reactivity, and compensatory autoregulatory responses. Whereas anesthesia-related depression of cardiac performance and arterial vasodilation are well recognized adverse effects contributing to anesthetic risk, far less emphasis has been placed on effects impacting venous physiology and venous return. The venous circulation, containing about 65–70% of the total blood volume, is a pivotal contributor to stroke volume and cardiac output. Vasodilation, particularly venodilation, is the primary cause of relative hypovolemia produced by anesthetic drugs and is often associated with increased venous compliance, decreased venous return, and reduced response to vasoactive substances. Depending on factors such as patient status and monitoring, a state of relative hypovolemia may remain clinically undetected, with impending consequences owing to impaired oxygen delivery and tissue perfusion. Concurrent processes related to comorbidities, hypothermia, inflammation, trauma, sepsis, or other causes of hemodynamic or metabolic compromise, may further exacerbate the condition. Despite scientific and technological advances, clinical monitoring and treatment of relative hypovolemia still pose relevant challenges to the anesthesiologist. This short perspective seeks to define relative hypovolemia, describe the venous system’s role in supporting normal cardiovascular function, characterize effects of anesthetic drugs on venous physiology, and address current considerations and challenges for monitoring and treatment of relative hypovolemia, with focus on insights for future therapies.

Terms, Definitions, Nomenclature, and Routes of Fluid Administration

“…A reduction in total circulating blood volume. Absolute hypovolemia can be caused by dehydration (i.e., water and electrolyte loss) or the loss of blood from the body or into a body cavity (e.g., abdomen) ( 1 , 2 ).…”

Rebound hypothermia after cytoreductive surgery with hyperthermic intraperitoneal chemotherapy (CRS-HIPEC) and cardiac arrest in immediate postoperative period: a report of two cases and review of literature

“…With active rewarming measures, it is a possibility that the subsequent vasodilatation caused could have unmasked an underlying hypovolemia which further exacerbated the hemodynamic instability [15]. Relative hypovolemia caused due to vasodilatation primarily, venodilation, encountered during anesthesia has been attributed to multiple factors, such as the effect of anesthetic agents, loss of compensatory mechanisms, metabolic or respiratory acidosis, traumatic or surgically mediated inflammation and sepsis [16]. Kim et al in their study showed an increase in one year mortality in post-operative patients having an increase or decrease in axillary temperatures (taking median temperature as 36.6 degree Celsius) on admission to the ICU [17].…”

Síndrome de baja gasto cardíaco en el posoperatorio de cirugía cardíaca

“…Si bien esta última definición es útil, ya que acepta el término de SBGC en pacientes en los que no conocemos el GC, (muy frecuente en la práctica clínica habitual) incluye el concepto de "hipovolemia relativa". Según la literatura, esta se define como la incapacidad del volumen sanguíneo de llenar el compartimiento vascular por disminución de las resistencias vasculares sistémicas (RVS) (7,8) . Sin embargo, la definición de la SEMICYUC se refiere a una PCP <15 mmHg.…”