Vasoplegic Syndrome

Overview

Vasoplegic syndrome is a severe form of vasodilatory shock characterized by profound and persistent low blood pressure (hypotension) despite normal or increased cardiac output and adequate fluid resuscitation. It is often seen in the context of cardiac surgery, particularly following cardiopulmonary bypass (CPB), and can lead to multi-organ dysfunction if not promptly managed. The syndrome is marked by a loss of vascular tone and resistance, resulting in systemic hypotension that is unresponsive to conventional vasopressors.

Causes

Vasoplegic syndrome typically occurs as a complication of major surgery or critical illness. The most common triggers include:

• Cardiopulmonary bypass (CPB): Seen in a significant subset of patients undergoing cardiac surgery, particularly valve replacements or heart transplants

• Systemic inflammatory response: Triggered by surgery, trauma, sepsis, or transfusions

• Use of ACE inhibitors or angiotensin receptor blockers (ARBs) prior to surgery

• Sepsis or severe infection: Can lead to a similar vasodilatory shock state

• Anaphylaxis or other inflammatory reactions

Symptoms

Symptoms of vasoplegic syndrome are primarily related to severe hypotension and inadequate tissue perfusion. Key clinical features include:

• Persistent low blood pressure despite adequate fluid and cardiac output

• Warm extremities due to vasodilation (in contrast to cold shock)

• Tachycardia (elevated heart rate)

• Low systemic vascular resistance (SVR) and high or normal cardiac output

• Signs of organ hypoperfusion, such as altered mental status, oliguria, or lactic acidosis

Diagnosis

Diagnosis of vasoplegic syndrome is clinical, often made in the intensive care setting following cardiac surgery. It is based on hemodynamic monitoring and the exclusion of other causes of shock. Diagnostic criteria and tools include:

• Hemodynamic parameters: Low mean arterial pressure (MAP), low SVR, and high or normal cardiac output

• Response to fluid resuscitation: Minimal or no improvement in blood pressure despite volume expansion

• Invasive monitoring: Pulmonary artery catheter or arterial line to assess cardiac output and vascular resistance

• Exclusion of other causes: Rule out hypovolemia, myocardial dysfunction, hemorrhage, and obstructive shock

Treatment

Treatment of vasoplegic syndrome requires prompt hemodynamic stabilization and reversal of the vasodilatory state. Management strategies include:

• Vasopressors: High doses of norepinephrine, vasopressin, or phenylephrine are typically used

• Methylene blue: A selective inhibitor of nitric oxide synthase and guanylate cyclase, often effective in refractory cases

• Hydrocortisone: May be administered for its vasoconstrictive and anti-inflammatory effects

• Fluid resuscitation: To ensure adequate preload, though overhydration should be avoided

• Hemodynamic monitoring: Continuous assessment to guide therapy and adjust medications

Prognosis

The prognosis of vasoplegic syndrome depends on the severity of hypotension, the timing of intervention, and the patient’s underlying health status. With prompt recognition and aggressive management, many patients recover fully. However, prolonged hypotension and delayed treatment can lead to multi-organ failure and increased mortality. Patients undergoing cardiac surgery who are at high risk for vasoplegia may benefit from prophylactic strategies, including methylene blue administration or adjustment of preoperative medications.