Vasoplegia Syndrome
Vasoplegia syndrome is a rare but life-threatening condition where blood vessels lose their normal ability to contract, causing dangerously low blood pressure despite the heart pumping normally or even harder than usual. With mortality rates as high as 25%, understanding this condition is crucial for patients and families facing cardiac surgery or serious illness.
Table of contents
- What is vasoplegia syndrome?
- What causes vasoplegia syndrome?
- When does vasoplegia syndrome occur?
- How is vasoplegia syndrome diagnosed?
- What happens in the body?
- How is vasoplegia syndrome treated?
- What are the outcomes?
What is vasoplegia syndrome?
Vasoplegia syndrome is a medical condition characterized by severe, uncontrolled widening of blood vessels throughout the body. This causes profound low blood pressure even though the heart is pumping blood normally or at higher than normal levels[1][2]. The main problem is that the blood vessels lose their ability to tighten or constrict properly, which is necessary to maintain healthy blood pressure.
In medical terms, this condition involves abnormally low systemic vascular resistance (the resistance blood encounters as it flows through blood vessels) combined with a normal or increased cardiac output (the amount of blood the heart pumps)[4]. The condition is also sometimes called vasodilatory shock or vasoplegic shock.
vasoplegic shock, vasodilatory shock, postoperative vasoplegic syndrome
What causes vasoplegia syndrome?
Vasoplegia syndrome can occur due to various medical conditions and situations. The most common causes include responses to infection or medical procedures that trigger widespread inflammation in the body[2].
The condition most frequently occurs during and after cardiac surgery, particularly when a heart-lung bypass machine is used. In fact, it can affect up to 25% of patients undergoing cardiac surgery[4][6]. The risk increases with longer time spent on the bypass machine and longer periods when blood flow to the heart is stopped during surgery[1].
Other situations where vasoplegia syndrome may develop include:
- Septic shock (severe infection spreading through the bloodstream)
- Organ transplantation, especially liver transplantation[1]
- Kidney, heart, and lung transplants[1]
- Severe allergic reactions (anaphylaxis)
- Major trauma or burns[2]
- Severe bleeding
Several patient characteristics and medications can increase the risk of developing vasoplegia syndrome during surgery. These include older age, taking certain blood pressure medications before surgery (particularly angiotensin-converting enzyme inhibitors or ACE inhibitors, which are medications that help relax blood vessels), using diuretics (water pills), having diabetes, heart failure, kidney disease, and receiving blood transfusions[1][4].
When does vasoplegia syndrome occur?
The timing of vasoplegia syndrome depends on the underlying cause. When related to cardiac surgery, it typically develops within the first 4 to 24 hours after the operation[3][10]. In septic shock, vasoplegia is often the dominant feature of the condition and can develop as the infection progresses[4].
During cardiac surgery, exposure of blood to the artificial surfaces inside the heart-lung bypass machine triggers an inflammatory response that can lead to vasoplegia[10]. The longer the surgery and the more time spent on bypass, the greater the risk of developing this complication[1].
How is vasoplegia syndrome diagnosed?
Doctors diagnose vasoplegia syndrome based on specific measurements of heart function and blood pressure. The typical definition includes low systemic vascular resistance combined with normal or high cardiac output, along with dangerously low blood pressure that requires aggressive treatment[5].
Specific diagnostic criteria often used include a systemic vascular resistance index less than 1,600 dyn·sec/cm5/m2 and a cardiac index greater than 2.5 L/min/m2 within the first 4 hours after surgery[3]. In practical terms, this means the heart is pumping enough blood, but the blood vessels are so relaxed that blood pressure drops dangerously low.
Other signs include systolic blood pressure below 90 mmHg or mean arterial pressure below 60 mmHg despite receiving medications to raise blood pressure[5]. The condition is particularly notable because standard blood pressure medications may not work as well as expected.
What happens in the body?
The development of vasoplegia syndrome involves complex changes in how blood vessels function. Multiple biological pathways contribute to the excessive widening of blood vessels and their reduced response to normal signals that should cause them to constrict.
One major factor is increased production of nitric oxide, a substance that causes blood vessels to relax and widen[4][8]. During cardiac surgery with a bypass machine, or during severe infections, the body produces excessive amounts of nitric oxide, leading to uncontrolled blood vessel widening.
The body also experiences deficiency of vasopressin, a hormone that normally helps maintain blood pressure by constricting blood vessels[4][10]. This deficiency makes it harder for the body to maintain adequate blood pressure.
Other contributing factors include:
- Widespread inflammation triggered by exposure to foreign surfaces (like bypass machine tubing) or infection[1][10]
- Changes in how smooth muscle cells in blood vessel walls respond to chemical signals
- Production of hydrogen sulfide, another substance that causes blood vessels to relax[4]
- Alterations in various hormone systems that normally regulate blood pressure, including the renin-angiotensin-aldosterone system[4]
- Reduced responsiveness to the body’s own stress hormones (catecholamines)[8]
The pathophysiology is similar across different causes of vasoplegia, whether from surgery, infection, or other conditions, though the triggering events differ[2][8].
How is vasoplegia syndrome treated?
Treatment of vasoplegia syndrome focuses on restoring normal blood pressure and ensuring adequate blood flow to vital organs. The approach typically involves giving fluids and medications that constrict blood vessels, called vasopressors.
Catecholamines (medications similar to the body’s stress hormones) are the traditional first-line treatment. The most commonly used catecholamine is norepinephrine[4][8]. Other catecholamines that may be used include dopamine, epinephrine, and phenylephrine[4].
When catecholamines alone are not effective, doctors may add other medications that work through different mechanisms:
Vasopressin is a hormone that helps restore blood vessel tone and is often added when standard vasopressors are insufficient[1][4]. Recent guidelines suggest adding vasopressin early in treatment to limit the need for high doses of catecholamines[8].
Methylene blue is a medication that works by blocking some of the pathways that cause excessive blood vessel relaxation, particularly those involving nitric oxide. There is evidence supporting its use in vasoplegia syndrome, especially after cardiac surgery[1][3][4].
Angiotensin II is a newer treatment option that works through the body’s natural blood pressure regulation system. It has shown promise in treating vasoplegia resistant to other treatments[1][4].
Hydroxocobalamin, a form of vitamin B12, can help by blocking nitric oxide and hydrogen sulfide, both of which contribute to blood vessel widening[1][4][9]. Studies have shown it can reduce the need for other vasopressor medications[9].
Vitamin C (ascorbic acid) and thiamine have also been studied as potential treatments, as they may help restore normal blood vessel function[1][4].
Corticosteroids, such as hydrocortisone, may be helpful in some cases, particularly when the body’s stress response system is not functioning properly[4][8].
The goal of treatment is to maintain a mean arterial pressure of at least 65 mmHg to ensure adequate blood flow to vital organs[9]. Treatment requires close monitoring in an intensive care unit, and the specific combination of medications is tailored to each patient’s response.
What are the outcomes?
Vasoplegia syndrome is a serious condition with significant risks. Mortality rates can reach 25% or higher, making prompt recognition and treatment essential[1][4].
The condition is associated with increased complications beyond mortality. Patients who develop vasoplegia syndrome have higher rates of kidney failure, longer stays in intensive care units and hospitals, and increased risk of other organ complications[4]. Some patients may develop catecholamine-resistant vasoplegia, where standard vasopressor medications become ineffective, which carries particularly high mortality risk[4].
The severity of vasoplegia also correlates with worse outcomes. More severe cases requiring higher doses of vasopressor medications are associated with increased rates of multi-organ failure, significant bleeding, and respiratory failure[4][6].
Despite these serious risks, many patients do recover with appropriate and timely treatment. The key to improving outcomes is early recognition of the syndrome, prompt initiation of treatment, and close monitoring by experienced healthcare teams. Research continues to explore better treatment strategies and ways to predict which patients are at highest risk, with the goal of improving survival and reducing complications.
