Intraoperative hypotension (IOH) is a common complication during surgical procedures under anesthesia . IOH can lead to adverse outcomes, including organ dysfunction, increased morbidity, and longer hospital stays. Studies have shown IOH during noncardiac surgery is associated with an increased risk of 30-day major adverse cardiac or cerebrovascular events . The definition of IOH has long been debated, but a recent systematic review found that when mean arterial pressure (MAP) falls under 80 mmHg for greater than 10 minutes, end-organ injury can occur . Identifying and understanding the associated risk factors for IOH is crucial for preventing and managing intraoperative hypotension effectively.
The choice of anesthetic agents and techniques can significantly influence the risk of intraoperative hypotension. Certain drugs, such as volatile anesthetics, induction agents, and opioids, can cause dose-dependent hypotension . Additionally, regional anesthesia techniques, such as epidurals and spinal blocks, which cause a sympathetic blockade, can lead to IOH. Anesthesiologists should carefully select anesthetic agents and techniques, considering the patient’s overall health, surgical requirements, and risk factors for hypotension. Some of these risk factors include older aged patients who may be more susceptible to IOH due to decreased cardiovascular reserve and altered baroreceptor function. Furthermore, those with comorbidities like hypertension, diabetes, and cardiovascular diseases are at higher risk for IOH. Certain medications, such as beta-blockers, alpha-2 agonists, and angiotensin-converting enzyme inhibitors, can impact blood pressure regulation intraoperatively, and careful monitoring of patients on these agents is warranted .
Intraoperative hypotension must be treated based upon the underlying etiology. Thus, determining the underlying cause of hypotension is essential in management . One important step in management is assessment of volume status for hypovolemia, whether due to preoperative fasting, blood loss, or inadequate fluid replacement. The duration of surgery and type of surgery are also variables that can affect hemodynamics. Longer surgeries and those involving significant blood loss such as vascular or orthopedic surgeries are associated with a higher risk of intraoperative hypotension. Prolonged exposure to anesthetic agents and mechanical ventilation causing high intrathoracic pressure can also affect hemodynamics during surgery . Additionally, the position a patient is in during surgery can affect venous return and cardiac output. The use of advanced monitoring techniques, such as arterial line and cardiac output monitoring, can help detect IOH early . Continuous monitoring allows for prompt adjustments and interventions, fluid administration, or use of first-line vasopressors like ephedrine, phenylephrine, and norepinephrine .
Overall, intraoperative hypotension is a common and potentially serious complication during surgery. Identifying and mitigating risk factors is crucial for ensuring patient safety and positive outcomes. An individualized approach that includes optimizing preoperative conditions, selecting appropriate anesthetic agents, and vigilant monitoring during surgery is essential in minimizing the risk of IOH and optimizing perioperative care.
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