Vasoplegia is a state of pathological vasodilation, meaning the blood vessels lose their ability to constrict properly, causing dangerously low blood pressure even when the heart is pumping normally or even harder than usual. It shows up most often after cardiac surgery involving cardiopulmonary bypass, during septic shock, or after organ transplantation. Despite being a well-recognized clinical emergency, there is no universally agreed-upon definition, which has made studying and treating it surprisingly difficult.
What Vasoplegia Looks Like
The hallmark of vasoplegia is a disconnect between what the heart is doing and what the blood pressure is showing. The heart keeps pumping adequate or even elevated volumes of blood, but systemic vascular resistance, the degree of “squeeze” the blood vessels provide, drops so low that blood pressure plummets. Fluids do not fix it. Standard doses of vasopressors, the drugs that normally tighten blood vessels, barely move the needle. The result is organ malperfusion: the kidneys, brain, gut, and other tissues are not getting enough pressure-driven blood flow even though the heart itself is working fine.1PubMed. Vasoplegic Syndrome in Cardiac Surgery: A Narrative Review of Etiologic Mechanisms and Therapeutic Options
One of the persistent frustrations in this area is that clinicians and researchers do not share a single definition. A systematic review of studies on vasoplegia after cardiac surgery found that blood pressure thresholds appeared in about 84% of definitions and cardiac output criteria in about 74%, but the specific cutoff values varied widely from study to study.2Critical Care Explorations. Definitions for Vasoplegia Associated With On-Pump Cardiac Surgery: A Systematic Review With Meta-Analysis Some definitions require vasopressor dependence for a set number of hours. Others look at the ratio of vasopressor dose to blood pressure response. This inconsistency makes it hard to compare research across institutions and has slowed the development of standardized treatment protocols.3PubMed Central. Definitions and pathophysiology of vasoplegic shock
Why Blood Vessels Stop Responding
The physiology behind vasoplegia involves several overlapping mechanisms, and their relative importance shifts depending on the clinical trigger. In broad terms, the smooth muscle cells that line blood vessels and normally contract to maintain vascular tone become unable to do so. Three processes tend to dominate.
First, nitric oxide production goes into overdrive. Normally, nitric oxide is a useful signaling molecule that helps regulate blood flow. But in vasoplegia, an inducible form of the enzyme that makes nitric oxide gets switched on by inflammation, flooding the vascular smooth muscle with far more nitric oxide than it can handle. The result is persistent relaxation of the vessel walls.4PubMed Central. Vasoplegia: Mechanism and Management Following Cardiopulmonary Bypass
Second, vasopressin, one of the body’s key hormones for maintaining blood pressure, becomes depleted. Under normal stress, the pituitary gland releases vasopressin to help tighten blood vessels. During prolonged shock or after cardiopulmonary bypass, the body’s stores of vasopressin run dry, removing one of the backup mechanisms that would ordinarily keep vascular tone intact.5PubMed Central. Vasoplegia: Mechanism and Management Following Cardiopulmonary Bypass
Third, the receptors that vasopressors bind to become desensitized. Norepinephrine, the workhorse vasopressor in critical care, acts on adrenergic receptors on blood vessel walls. In vasoplegia, these receptors get downregulated or chemically uncoupled from their signaling pathways, so pumping in more norepinephrine produces diminishing returns. The same desensitization can hit vasopressin receptors and angiotensin receptors, essentially blunting the effect of every major class of blood-pressure-raising drug at once.6PubMed Central. Vasoplegia treatments: the past, the present, and the future Other mediators, including adenosine, prostanoids, endothelins, and hydrogen sulfide, also play roles, though their relative contributions are still being sorted out.7PubMed Central. Vasoplegia: A Review
Where Vasoplegia Shows Up
Cardiac surgery using cardiopulmonary bypass is the most studied trigger. When blood circulates through an external machine during open-heart procedures, it contacts foreign surfaces that ignite a systemic inflammatory response. That inflammation drives the nitric oxide overproduction and vasopressin depletion described above. Longer time on the bypass machine correlates directly with higher vasoplegia risk: one meta-analysis found that each additional minute of bypass time slightly but significantly increased the odds of developing post-surgical shock.8PubMed Central. Effect of preoperative renin-angiotensin system blockade on vasoplegia after cardiac surgery: A systematic review with meta-analysis
Sepsis is the other major setting. In septic shock, the body’s inflammatory response to infection triggers many of the same vascular mechanisms, with nitric oxide overproduction being especially prominent. Liver transplantation is another well-documented context, partly because the reperfusion of a new liver dumps inflammatory mediators into the circulation in a single bolus.9Advances in Anesthesia. Vasoplegic Syndrome: An Update on Perioperative Considerations Lung transplantation carries similar risks. Burns, major trauma, and even certain drug overdoses can also precipitate the syndrome, though these scenarios are studied less extensively.
Who Is Most at Risk
Several patient-level and procedural factors raise the odds of developing vasoplegia, particularly in the cardiac surgery population where most of the research has been done.
Preoperative use of medications that affect the renin-angiotensin system stands out. Patients taking ACE inhibitors before cardiac surgery face roughly double the odds of developing vasoplegia compared with those not on these drugs, according to a meta-analysis that pooled adjusted results from multiple studies.10PubMed Central. Effect of preoperative renin-angiotensin system blockade on vasoplegia after cardiac surgery: A systematic review with meta-analysis Angiotensin receptor blockers carry a similar association. Other independent risk factors identified in surgical cohorts include chronic kidney disease, longer aortic cross-clamp time, and higher preoperative severity scores.11PubMed. Risk factors for vasoplegia after coronary artery bypass and valve surgery Blood transfusions, heparin, amiodarone, and protamine have also been flagged as potential contributors.12PubMed. Vasoplegic syndrome: An update on perioperative considerations
Whether to stop ACE inhibitors before planned cardiac surgery has become one of the more debated questions in perioperative medicine. Continuing them risks vasoplegia; stopping them risks uncontrolled hypertension or renal complications leading up to the procedure. Different surgical centers handle this differently, and no large randomized trial has definitively settled the question.
Identifying Vasoplegia at the Bedside
Diagnosis is primarily clinical. In practice, the critical care team recognizes vasoplegia when a patient has low blood pressure that does not respond to fluids, rising vasopressor requirements, and evidence that the heart itself is pumping adequately. Echocardiography, particularly bedside point-of-care ultrasound, plays an increasingly important role. A preserved or even hyperdynamic heart on echo in the setting of profound hypotension essentially confirms that the problem is in the blood vessels, not the heart muscle.13PubMed Central. Proposed echocardiography-guided flowchart for calcium channel blocker overdose: distinguishing vasoplegia from cardiogenic shock This distinction matters because treating cardiogenic shock with vasopressor strategies designed for vasoplegia, or vice versa, can be harmful.
Researchers have also been investigating circulating biomarkers that could predict vasoplegia before it develops or identify it earlier. One systematic review found that adrenomedullin, a peptide involved in vasodilation, showed particular promise: higher baseline levels predicted subsequent development of shock and were associated with prolonged vasopressor dependence after surgery.14PubMed Central. Circulating biomarkers of vasoplegia: a systematic review These biomarkers are not yet standard clinical tools, but they represent one of the more active areas of translational research.
First-Line Treatment
When vasoplegia develops, the initial response follows a predictable escalation. Norepinephrine is the typical first-line vasopressor, but as noted, vasoplegia is often defined by its resistance to norepinephrine. The adrenergic receptors that norepinephrine targets become desensitized, so escalating the dose hits a ceiling and starts to cause problems of its own: excessive heart rate, arrhythmias, and worsening tissue oxygen delivery.15PubMed Central. Vasoplegia treatments: the past, the present, and the future
Vasopressin is typically added early as a second agent. Because it works through a completely different set of receptors than norepinephrine, it bypasses the desensitized adrenergic pathway. In post-bypass vasoplegia, vasopressin has been shown to significantly improve blood pressure and systemic vascular resistance. One study documented that systolic blood pressure rose from roughly 90 mmHg to about 120 mmHg after vasopressin was started, and urine output nearly doubled, suggesting improved kidney perfusion.16PubMed. Vasopressin therapy for vasoplegic syndrome following cardiopulmonary bypass The rationale is straightforward: if the body’s own vasopressin stores are depleted, replacing them addresses a root cause rather than just pushing harder on the same broken pathway.
The broader therapeutic philosophy in vasoplegia has shifted toward a multimodal, “receptor-sparing” approach. Rather than cranking up a single vasopressor until it either works or causes toxicity, clinicians layer agents that act on different receptor systems simultaneously. This strategy limits the desensitization of any one receptor type and keeps the total dose of each drug lower.
Rescue Therapies for Refractory Cases
When norepinephrine and vasopressin are not enough, several second-tier agents enter the picture, each targeting a different piece of the vasoplegic puzzle.
Methylene blue works as a nitric oxide scavenger and inhibitor of the enzyme that produces the vasodilatory signaling molecule cyclic GMP. A meta-analysis of studies involving over 400 patients found that methylene blue significantly reduced vasopressor requirements compared with controls.17PubMed Central. Efficacy and safety of methylene blue in patients with vasodilatory shock: A systematic review and meta-analysis It is one of the more established rescue agents, though there are caveats: it can interfere with pulse oximetry readings and is contraindicated in patients taking serotonergic medications due to the risk of serotonin syndrome.
Angiotensin II, approved in some countries as a vasopressor, targets yet another receptor pathway. In a post-hoc analysis of patients with vasoplegia after cardiac surgery, nearly 90% of those receiving angiotensin II achieved a target blood pressure response, compared with none in the placebo group.18PubMed. Treatment With Angiotensin II Is Associated With Rapid Blood Pressure Response and Vasopressor Sparing in Patients With Vasoplegia After Cardiac Surgery That striking difference came from a small subgroup, so the numbers should be interpreted with appropriate caution, but it illustrates the potential benefit of reaching for an entirely different receptor system when the standard ones are exhausted.
Hydroxocobalamin, a form of vitamin B12 traditionally used to treat cyanide poisoning, has emerged as a newer rescue therapy. It appears to scavenge nitric oxide and hydrogen sulfide, two of the key vasodilatory mediators in vasoplegia. Case series have documented improvements in blood pressure and reductions in vasopressor requirements after hydroxocobalamin administration, with sustained effects and no attributable adverse events in small cohorts.19PubMed Central. High-Dose Hydroxocobalamin for Refractory Vasoplegia Post Cardiac Surgery It has been reported in use across cardiac surgery, liver transplantation, and septic shock settings.20International Journal of Surgery Case Reports. Hydroxocobalamin for treatment of catecholamine-resistant vasoplegia during liver transplantation: A single-center series of 20 cases Randomized controlled trials are still lacking, which means the evidence is promising but preliminary.
Corticosteroids also play a role, particularly in cases where relative adrenal insufficiency is suspected. Critical illness can impair the adrenal glands’ ability to produce cortisol, and low-dose hydrocortisone has been part of septic shock management for years. The same logic extends to post-surgical vasoplegia, though the evidence base is thinner in that context.
Extracorporeal Blood Purification
An emerging and more experimental strategy involves physically removing inflammatory mediators from the bloodstream using hemoadsorption devices. The idea is that if the inflammatory cascade is driving vasoplegia, pulling those molecules out of circulation might restore vascular tone. A hemoadsorption device called CytoSorb has generated interest in patients with septic or vasoplegic shock by broadly and non-selectively removing cytokines and other inflammatory mediators.21PubMed Central. Adjunctive Hemoadsorption Therapy with CytoSorb in Patients with Septic/Vasoplegic Shock: A Best Practice Consensus Statement Results have been described as promising in consensus statements and case series, but large randomized trials demonstrating clear survival benefit remain to be published. It represents one of the frontiers of vasoplegia management: attacking the upstream cause rather than just fighting the downstream blood pressure consequence.
What Vasoplegia Means for Outcomes
Vasoplegia is not a minor hemodynamic hiccup. When it develops, it substantially worsens outcomes. A retrospective study of lung transplant recipients found that those who developed vasoplegia had nearly double the rate of renal replacement therapy, stayed in the ICU about twice as long, and had 30-day mortality of about 11% compared with roughly 6% in non-vasoplegic patients. At one year, the mortality gap was even wider: about 21% versus 12%.22PubMed. Postoperative vasoplegia in lung transplantation: incidence and relation to outcome in a single-centre retrospective study Kidney injury was more common, ventilator times were longer, and the rate of delayed chest closure was higher in the vasoplegia group.
These outcome differences are not entirely surprising. Prolonged hypotension means prolonged organ underperfusion, and the kidneys are among the most vulnerable. But the data underscores why aggressive and early treatment of vasoplegia matters. The syndrome is not self-limiting in many patients: without effective vasopressor strategies, the low-resistance state can persist for hours or days, accumulating organ damage with each passing hour.
Research Gaps and the Road Ahead
Much of what clinicians know about treating vasoplegia has been extrapolated from septic shock research, even though the two conditions, while overlapping mechanistically, are not identical. In sepsis, the trigger is ongoing infection and its associated inflammatory load. In post-bypass vasoplegia, the trigger is the sterile inflammatory response to cardiopulmonary bypass. The inflammatory pathways overlap but are not perfectly congruent, which means a drug that works well in one context may not perform equally in the other.
The lack of a consensus definition remains a practical obstacle. When researchers at different institutions use different blood pressure thresholds, different vasopressor dose cutoffs, and different time windows to define vasoplegia, meta-analyses and cross-study comparisons become unreliable. Efforts are underway to standardize diagnostic criteria, but the field has not yet coalesced around a single framework.23Critical Care Explorations. Definitions for Vasoplegia Associated With On-Pump Cardiac Surgery: A Systematic Review With Meta-Analysis
Receptor desensitization is another area ripe for targeted investigation. Animal research has shown that compounds capable of blocking a specific enzyme called GRK2, which drives adrenergic receptor desensitization, can restore norepinephrine’s ability to constrict blood vessels during sepsis.24PubMed. Erythropoietin Reverses Sepsis-Induced Vasoplegia to Norepinephrine Through Preservation of α1D-Adrenoceptor mRNA Expression and Inhibition of GRK2-Mediated Desensitization in Mouse Aorta Translating that finding from mouse aortas to human intensive care units remains a long road, but it points toward a future where treatments could be tailored to the specific molecular defect driving each patient’s vasoplegia, rather than simply layering additional vasopressors and hoping one of them works.
The biomarker work mentioned earlier also holds real potential. If clinicians could identify, through a blood test drawn before or shortly after surgery, which patients are heading toward vasoplegia, they could pre-treat or intervene earlier rather than waiting until the blood pressure has already collapsed. Adrenomedullin levels are the closest candidate to clinical use, but validation in large prospective studies is still needed.25PubMed Central. Circulating biomarkers of vasoplegia: a systematic review