From the Guidelines
Postoperative hypotension is most commonly caused by hypovolemia, bleeding, vasodilation from anesthetics or sepsis, cardiac dysfunction, and medication effects, and its management should prioritize identifying and treating the underlying cause while maintaining adequate organ perfusion, as supported by the most recent evidence 1.
Causes of Postoperative Hypotension
The causes of postoperative hypotension can be multifactorial and include:
- Hypovolemia: This is one of the most frequent causes and can be due to blood loss, fluid shifts, or inadequate fluid replacement.
- Bleeding: Either overt or covert bleeding can lead to significant hypovolemia and hypotension.
- Vasodilation: Anesthetics, sepsis, or systemic inflammatory response syndrome (SIRS) can cause vasodilation, leading to decreased peripheral resistance and hypotension.
- Cardiac dysfunction: Pre-existing cardiac conditions or those acquired during surgery can impair cardiac function, leading to hypotension.
- Medication effects: Certain medications, such as anesthetics, sedatives, or antihypertensives, can cause or exacerbate hypotension.
Management of Postoperative Hypotension
Management should start with a thorough assessment to identify the underlying cause. A fluid challenge of 500-1000 mL of crystalloids over 15-30 minutes is recommended as the initial step, as hypovolemia is a common cause 2. If hypotension persists, vasopressors such as norepinephrine or phenylephrine may be necessary. Continuous hemodynamic monitoring, including blood pressure, heart rate, urine output, and possibly central venous pressure, is essential for guiding treatment.
Importance of Prompt Recognition and Treatment
Prompt recognition and treatment of postoperative hypotension are crucial to prevent organ ischemia, particularly affecting the kidneys, brain, and heart, which can lead to multiorgan failure if left untreated. The latest guidelines emphasize the importance of managing postoperative blood pressure to minimize risks and improve outcomes 1.
Future Research Directions
Further research is needed to define the optimal levels of postoperative blood pressure, the best methods and timing of blood pressure measurement, and the optimal strategies for resuming chronic antihypertensive therapy, as highlighted in recent consensus statements 3, 4. However, based on the current evidence, the priority should be to identify and treat the underlying cause of hypotension while maintaining adequate organ perfusion, with a focus on minimizing morbidity, mortality, and improving quality of life 1.
From the FDA Drug Label
For blood pressure control in certain acute hypotensive states (e.g., pheochromocytomectomy, sympathectomy, poliomyelitis, spinal anesthesia, myocardial infarction, septicemia, blood transfusion, and drug reactions) The causes of postoperative hypotension include:
- Surgical procedures such as pheochromocytomectomy and sympathectomy
- Spinal anesthesia
- Myocardial infarction
- Septicemia
- Blood transfusion
- Drug reactions 5 Note that these are not exhaustive and the label does not provide a comprehensive list of causes of postoperative hypotension.
From the Research
Causes of Postoperative Hypotension
The causes of postoperative hypotension are multifactorial and can be attributed to various factors, including:
- Vasodilation, which is the most common suggested physiological disturbance 6
- Intraoperative hypotension, which can lead to postoperative complications such as acute kidney injury, myocardial injury, and death 7
- Hypovolemia, which can occur due to blood loss or fluid shifts during surgery
- Anesthetic effects, which can cause vasodilation and decreased cardiac output
Physiological Disturbances
Physiological disturbances that can contribute to postoperative hypotension include:
- Vasodilation, which can lead to decreased peripheral resistance and decreased blood pressure 6
- Decreased cardiac output, which can occur due to anesthetic effects, hypovolemia, or cardiac dysfunction
- Increased vascular capacitance, which can lead to decreased venous return and decreased cardiac output
Clinical Relevance
Postoperative hypotension is associated with major postoperative complications, including:
- Myocardial injury, which can occur due to prolonged exposure to hypotension 8
- Acute kidney injury, which can occur due to decreased renal perfusion 7
- Death, which can occur due to severe postoperative complications 7
Therapeutic Approaches
Therapeutic approaches to postoperative hypotension include: