Fact-checked by Grok 2 weeks ago

Distributive shock

Distributive shock, also known as vasodilatory shock, is one of the four primary classifications of shock syndromes characterized by inadequate tissue perfusion resulting from systemic vasodilation and maldistribution of blood flow, leading to decreased delivery of oxygen and nutrients to vital organs such as the brain, heart, and kidneys. This condition often involves relative hypovolemia due to pathological redistribution of intravascular volume, stemming from either loss of vascular tone regulation or increased vascular permeability, which shifts blood away from central circulation. The most common etiologies of distributive shock include , , from or , , and capillary leak syndromes. , the leading cause, arises from a dysregulated host to , triggering widespread release of inflammatory cytokines that promote and . involves IgE-mediated degranulation and release, causing rapid-onset and , while results from interruption of outflow, leading to unopposed parasympathetic activity and profound . Epidemiologically, distributive shock accounts for approximately 60% of cases in intensive care settings, with affecting at least 1.7 million adults annually in the United States and carrying a of up to 50%. Pathophysiologically, distributive shock features a hyperdynamic circulatory state in early phases, with low systemic , normal or increased , and warm extremities due to peripheral , but it progresses to myocardial depression and multiorgan failure if untreated. Inflammatory mediators like and cytokines exacerbate capillary leakage, further reducing effective circulating volume and impairing oxygen extraction at the level. Clinical presentation typically includes ( <65 mmHg), tachycardia, altered mental status, oliguria, and elevated serum lactate levels (>2 mmol/L), distinguishing it from other types like hypovolemic or , where predominates. Management prioritizes rapid with intravenous boluses (e.g., 250-500 mL crystalloids) to restore intravascular , followed by vasopressor support such as norepinephrine to maintain above 65 mmHg and improve organ perfusion. Etiology-specific interventions are crucial: antibiotics and source control for , epinephrine and antihistamines for , and high-dose corticosteroids for . varies widely, with overall mortality ranging from 20% to 80%, influenced by factors like age, comorbidities, levels, and the presence of positive blood cultures; early recognition and multidisciplinary care in an interprofessional team setting significantly enhance outcomes.

Definition and Classification

Definition

Distributive shock is a medical condition characterized by inadequate tissue resulting from the maldistribution of flow, primarily due to widespread systemic that causes relative despite normal or increased total . This leads to a decrease in systemic , impairing the delivery of oxygen and nutrients to vital organs while potentially increasing in the early stages. Unlike other forms of shock, distributive shock arises from vascular dysregulation rather than absolute volume depletion, pump failure, or mechanical obstruction. involves direct loss of intravascular volume, such as from hemorrhage or ; stems from primary cardiac dysfunction reducing output; and results from physical barriers to blood flow, like or . In contrast, distributive shock's hallmark is the pathological redistribution of existing away from peripheral tissues. The concept of distributive shock, initially termed vasodilatory shock, emerged in the amid efforts to classify shock beyond traumatic hemorrhage, with early distinctions recognizing up to five types based on . By the , refined understanding led to the widely adopted four-category framework—hypovolemic, cardiogenic, distributive, and obstructive—emphasizing distributive shock's role in conditions like , which remains its most common subtype. Clinically, distributive shock presents with a distinctive hemodynamic profile: due to low systemic , often accompanied by normal or elevated and . This pattern underscores the need for targeted interventions focusing on vascular tone restoration rather than solely volume expansion.

Types

Distributive shock is categorized into four primary subtypes based on the underlying mechanisms leading to and maldistribution of blood flow: , anaphylactic shock, , and endocrinologic shock. arises from severe infection, such as , resulting in and vascular leakage. Anaphylactic shock occurs due to an acute allergic reaction, triggering massive release and widespread . stems from disruption of the , often following , leading to loss of sympathetic tone and . Endocrinologic shock, exemplified by , involves hormone deficiencies that impair vascular responsiveness and fluid balance. At the microcirculatory level, distributive shock involves maldistribution of blood flow characterized by arteriolar , which reduces systemic ; increased venous , causing venous pooling and relative ; and , which promotes capillary leak and heterogeneous . These mechanisms contribute to inadequate tissue oxygenation despite normal or elevated . Septic shock represents the most prevalent subtype, accounting for 55-62% of distributive shock cases in intensive care units (ICUs), while is rare but presents acutely with rapid onset. Neurogenic and endocrinologic forms are less common, often comprising under 10% combined in ICU settings. Mixed forms of shock involving distributive features occur in approximately 25% of cases in cardiac intensive care units, according to 2025 data.

Etiology

Infectious causes

Distributive shock most commonly arises from infectious etiologies, with representing the predominant subtype triggered by systemic infections that provoke a dysregulated . develops when an escalates beyond local containment, leading to widespread and vascular dysfunction. The primary infectious agents include bacteria, viruses, fungi, and parasites, though bacteria account for the majority of cases. Gram-negative bacteria such as and , often originating from urinary or gastrointestinal sources, are frequent culprits, while Gram-positive organisms like and species, commonly from skin or respiratory infections, also play a significant role. Fungal infections, such as those caused by species, and parasitic invasions like severe malaria from , contribute less commonly but can precipitate in vulnerable populations; viral pathogens, including severe cases of or , are rarer triggers. These agents release toxins or directly activate immune pathways, amplifying the inflammatory cascade. Sepsis is defined as life-threatening caused by a dysregulated host response to . is a life-threatening condition that is a subset of in which circulatory and cellular/metabolic abnormalities are associated with a greater of mortality, typically characterized by persistent requiring vasopressors to maintain ≥65 mmHg and serum lactate >2 mmol/L despite adequate volume resuscitation. Risk factors that heighten susceptibility to infectious distributive shock include from conditions like , malignancy, or corticosteroid use; chronic diseases such as , , and ; and invasive procedures like , central lines, or urinary catheters that facilitate entry. Advanced age over 65 years and infancy further increase vulnerability due to immune senescence or immaturity. In the United States, sepsis affects approximately 1.7 million individuals annually, underscoring its substantial burden. The progression typically begins with a localized infection, such as or a , which, if untreated, leads to bacteremia or as pathogens enter the bloodstream. This dissemination triggers endothelial damage and cytokine release, culminating in , capillary leak, and multi-organ dysfunction syndrome (MODS), where vital organs like the kidneys, lungs, and heart fail due to hypoperfusion. Without , this cascade rapidly advances to refractory and high mortality rates exceeding 40%.

Non-infectious causes

Non-infectious causes of distributive shock encompass a range of sterile inflammatory, allergic, neurologic, and endocrine disruptions that lead to profound and relative without involvement. These etiologies often result from reactions, failure, or hormonal deficiencies, distinguishing them from infectious triggers by their non-microbial origins. Other non-infectious causes include severe burns, , and systemic , which trigger distributive shock through inflammatory mechanisms leading to and increased . Common examples include , , , and iatrogenic factors, each presenting with rapid hemodynamic instability requiring prompt recognition. Anaphylactic shock arises from IgE-mediated reactions to allergens such as foods (e.g., , ), medications (e.g., antibiotics like penicillin), or insect stings, triggering massive and systemic within minutes of exposure. This leads to widespread capillary leakage and , often accompanied by and urticaria. The incidence of , which can progress to shock, is estimated at approximately 210 per 100,000 person-years (2.1 per 1,000 person-years) , based on data from 2004 to 2016, particularly in individuals with prior sensitization or atopic conditions like . Neurogenic shock results from disruption of outflow, causing unopposed parasympathetic activity, profound , and , typically following acute above the T6 level, such as in from motor vehicle accidents or falls. Other contributors include Guillain-Barré syndrome or autonomic dysfunction from spinal anesthesia, leading to loss of vascular tone and without compensatory . This condition affects 20-50% of patients with injuries, with incidence rates reported as high as 19.3% in isolated injuries and 7% in thoracic or cases, emphasizing its prevalence in settings. Adrenal insufficiency contributes to distributive shock through cortisol deficiency, impairing vascular responsiveness to catecholamines via reduced alpha-1 receptor expression on arterioles, resulting in refractory . Absolute insufficiency, as in , or relative forms like critical illness-related insufficiency can be precipitated by non-infectious stressors such as abrupt withdrawal of chronic glucocorticoids, hemorrhage, or drugs like that suppress adrenal function. This is considered in up to 20-60% of critically ill patients with vasodilatory shock unresponsive to fluids and vasopressors, though exact incidence varies by population. Additional non-infectious causes include post-cardiopulmonary bypass (CPB) vasoplegia, an iatrogenic inflammatory response triggered by CPB during , leading to overproduction and profound in 5-44% of cases, often requiring prolonged vasopressor support. Iatrogenic vasodilation from drug overdoses, such as or nitroprusside, can similarly induce distributive shock by direct arteriolar relaxation, highlighting the role of therapeutic interventions in this pathology.

Pathophysiology

Hemodynamic alterations

Distributive shock is characterized by profound , which leads to a significant reduction in (), resulting in with a () typically below 65 mmHg, despite preserved or hyperdynamic . This impairs the vascular smooth muscle's response to vasoconstrictive agents, causing maldistribution of blood flow and inadequate even when total circulating volume is normal. The vasodilation increases venous capacitance, pooling blood in the peripheral venous system and creating relative hypovolemia that reduces cardiac preload. This relative hypovolemia exacerbates hypotension by limiting venous return to the heart. SVR can be quantified using the formula SVR = [(MAP - CVP) / CO] × 80, where MAP is mean arterial pressure in mmHg, CVP is central venous pressure in mmHg, and CO is cardiac output in L/min; the factor of 80 converts units to dynes·s·cm⁻⁵, highlighting how low SVR directly contributes to low MAP in the face of adequate CO. Consequently, organ perfusion is compromised, with reduced blood flow to critical organs such as the brain, heart, and kidneys, leading to potential ischemic damage. In the early hyperdynamic phase, extremities may appear warm due to peripheral vasodilation and high cardiac output, but as shock progresses, perfusion deficits cause mottling and cooling of the skin. The body mounts compensatory responses, including to maintain and to enhance oxygen delivery and compensate for . If these mechanisms fail, tissue hypoperfusion results in , with serum lactate levels exceeding 2 mmol/L indicating inadequate oxygen utilization and worsening prognosis.

Molecular mechanisms

Distributive shock is characterized by profound and vascular hyporeactivity at the cellular level, primarily driven by the overproduction of vasodilatory mediators such as (NO), prostaglandins, and . In , a major form of distributive shock, inducible (iNOS) is upregulated in vascular cells and endothelial cells in response to inflammatory stimuli, leading to excessive NO production. This reaction is catalyzed by iNOS as follows: \text{L-arginine} + \text{O}_2 + \text{NADPH} \xrightarrow{\text{iNOS}} \text{NO} + \text{citrulline} + \text{NADP}^+ The resulting NO diffuses into vascular smooth muscle cells, activating soluble guanylate cyclase to increase cyclic GMP levels, which promotes dephosphorylation of myosin light chains and subsequent vasodilation. Prostaglandins, particularly prostacyclin (PGI2), are released from endothelial cells via cyclooxygenase-2 (COX-2) induction, further contributing to vasodilation by relaxing vascular smooth muscle through cAMP elevation. Bradykinin, generated from the kinin-kallikrein system during inflammation, binds to B2 receptors on endothelial cells, stimulating NO and prostacyclin release while also increasing vascular permeability. The inflammatory cascade in distributive shock involves the release of pro-inflammatory cytokines such as tumor necrosis factor-alpha (TNF-α), interleukin-1 (IL-1), and interleukin-6 (IL-6) from activated macrophages and other immune cells in response to pathogens or tissue injury. These cytokines induce iNOS expression through nuclear factor-kappa B (NF-κB) pathway activation in endothelial and smooth muscle cells, perpetuating vasodilation and hyporeactivity. TNF-α and IL-1 also disrupt endothelial tight junctions by downregulating occludin and claudin-5, leading to increased capillary permeability and fluid extravasation into tissues, which exacerbates hypovolemia. IL-6 amplifies this response by stimulating further cytokine production and acute-phase reactants, creating a feedback loop that sustains endothelial dysfunction. Endothelial and mitochondrial dysfunction play central roles in the progression of distributive shock, impairing cellular energy production and increasing . -mediated endothelial damage reduces ATP-dependent ion pumps, leading to impaired vascular tone regulation and NO uncoupling, which shifts NO production toward generation. This results in elevated (ROS) levels, such as and , that nitrate proteins and lipids, further disrupting mitochondrial function and reducing ATP synthesis. In parallel, relative arises from suppression of hypothalamic-pituitary-adrenal axis activity, leading to inadequate production and diminished vascular responsiveness to catecholamines. also inhibit key enzymes like , compounding cellular hypoperfusion at the biochemical level. Mechanisms vary by subtype of distributive shock. In anaphylactic shock, IgE-mediated mast cell degranulation releases , which binds H1 receptors on vascular to induce rapid via increased intracellular calcium and NO release, alongside leukotrienes that promote further permeability. In neurogenic shock, causes sympathetic denervation, reducing norepinephrine release and unopposing parasympathetic tone, which leads to through decreased alpha-1 adrenergic signaling in vascular .

Clinical Presentation and Diagnosis

Signs and symptoms

Distributive shock manifests through a range of clinical signs reflecting widespread and relative , leading to inadequate tissue despite normal or increased initially. Common general signs include that is refractory to fluid resuscitation, ( often exceeding 100 beats per minute), warm and flushed skin due to peripheral , and altered mental status ranging from confusion to lethargy. In , however, may occur instead of due to loss of sympathetic tone. Type-specific symptoms vary by but share the core hemodynamic instability. In , patients often present with fever, chills, and rigors alongside the general signs, reflecting the inflammatory response to infection. Anaphylactic shock typically features urticaria, wheezing, , and from acute allergic reactions. , often following , is characterized by without compensatory , accompanied by below the injury level. , a form of distributive shock, may include , , , and electrolyte disturbances like . The condition can progress through stages, beginning with a hyperdynamic "warm " phase marked by bounding pulses, low systemic , and increased , which may transition to "cold " as compensatory mechanisms fail, leading to , cool extremities, (urine output less than 0.5 mL/kg/hour), and dyspnea from pulmonary congestion. This progression underscores the need for vigilant monitoring, as delayed recognition can exacerbate . Severity assessment often incorporates the Sequential Organ Failure Assessment (SOFA) score (updated as SOFA-2 in October 2025), which evaluates six organ systems to quantify shock acuity. Key components relevant to distributive shock include: respiratory (e.g., PaO2/FiO2 ratio <400 indicating mild dysfunction); coagulation (platelets <150 × 10^9/L); liver (bilirubin >1.2 mg/dL); cardiovascular (hypotension requiring vasopressors, with SOFA-2 scoring: 2 for low-dose norepinephrine equivalents ≤0.2 μg/kg/min, 3 for medium-dose >0.2 to ≤0.4 μg/kg/min, 4 for high-dose >0.4 μg/kg/min or with additional inotropes/mechanical support, to maintain ≥65 mmHg); ( <15); and renal (creatinine >1.2 mg/dL or urine output <500 mL/day). A SOFA score increase of 2 or more points during the first 48 hours is associated with higher mortality risk in septic and distributive shocks.

Diagnostic approaches

Diagnosis of distributive shock relies on clinical assessment to identify hypotension and signs of inadequate tissue perfusion, often using the quick Sequential Organ Failure Assessment (qSOFA) score for suspected septic cases, where a score of ≥2 (systolic blood pressure ≤100 mmHg, respiratory rate ≥22 breaths per minute, or altered mentation) indicates high risk for poor outcomes and prompts further evaluation. This bedside tool helps stratify patients with infection outside intensive care settings, though it is not specific to distributive shock subtypes. Laboratory tests are essential to confirm hypoperfusion and identify underlying causes. Elevated serum lactate levels greater than 2 mmol/L signal tissue hypoxia and guide resuscitation efforts in distributive shock. Blood cultures should be obtained prior to antibiotics to detect infectious etiologies, particularly in septic shock. Procalcitonin levels exceeding 2 ng/mL support a bacterial infection diagnosis, aiding differentiation from viral or non-infectious causes. A complete blood count (CBC) may reveal eosinophilia in anaphylactic shock, while low cortisol levels indicate possible adrenal insufficiency. Hemodynamic monitoring distinguishes distributive shock from other forms by revealing characteristic patterns, such as high cardiac output with low systemic vascular resistance via echocardiography. Central venous pressure (CVP) may be measured but is not recommended as a target for guiding fluid therapy; dynamic parameters such as passive leg raise or stroke volume variation are preferred to assess preload and fluid responsiveness. Resuscitation is guided toward normalizing serum lactate levels. These parameters help tailor fluid and vasopressor therapy without invasive pulmonary artery catheterization in most cases. Differential diagnosis involves excluding other shock types through targeted tests. Cardiac troponin and B-type natriuretic peptide (BNP) levels are measured to rule out cardiogenic shock, where elevations suggest myocardial injury or heart failure. Imaging, such as computed tomography (CT) scans, identifies infection sources like abscesses or sources of anaphylaxis. Bedside ultrasound, including the Rapid Ultrasound for Shock and Hypotension (RUSH) protocol, further evaluates cardiac function and volume status to confirm distributive physiology.

Management

Initial resuscitation

Initial resuscitation in distributive shock focuses on rapidly restoring tissue perfusion by addressing the underlying vasodilation and relative hypovolemia, primarily through aggressive fluid administration and vasopressor support to counteract low systemic vascular resistance. Fluid therapy begins with an intravenous bolus of crystalloids at a dose of at least 30 mL/kg body weight within the first 3 hours to expand intravascular volume and improve cardiac output. Balanced crystalloids, such as , are preferred over normal saline to minimize risks like hyperchloremic acidosis. To avoid over-resuscitation, which can lead to pulmonary edema or abdominal compartment syndrome, dynamic measures of fluid responsiveness should guide further boluses; examples include stroke volume variation greater than 10-13% in mechanically ventilated patients or a positive response to passive leg raising. If hypotension persists after adequate fluid resuscitation, vasopressors are initiated promptly, with norepinephrine as the first-line agent due to its potent alpha-adrenergic effects that increase vascular tone without significant tachycardia. The initial target is a mean arterial pressure (MAP) of at least 65 mmHg to ensure coronary and cerebral perfusion. Norepinephrine is typically infused at 0.01-0.5 mcg/kg/min, titrated based on response, with higher doses up to 3 mcg/kg/min possible in refractory cases. The infusion rate can be calculated using the formula: infusion rate (mL/hr) = [desired dose (mcg/kg/min) × patient weight (kg) × 60] / solution concentration (mcg/mL), where a common preparation is 4 mg norepinephrine in 250 mL of 5% dextrose (16 mcg/mL). Airway and ventilation management are critical if respiratory compromise accompanies hemodynamic instability, as hypoxemia exacerbates shock. Supplemental oxygen should be administered to maintain peripheral oxygen saturation (SpO2) above 94%, using nasal cannula, face mask, or high-flow systems as needed. Endotracheal intubation is indicated for patients with a Glasgow Coma Scale (GCS) score less than 8, severe respiratory failure (e.g., PaO2/FiO2 ratio <150), or inability to protect the airway, often requiring rapid sequence induction to minimize desaturation risks. Monitoring is established early to guide therapy, including placement of an arterial line for continuous blood pressure measurement and a central venous catheter for vasopressor administration and assessment of central venous pressure or oxygen saturation if indicated. These align with the Surviving Sepsis Campaign's 2021 updates on early goal-directed therapy, emphasizing serial lactate measurements (target normalization <2 mmol/L) and reassessment of perfusion markers like urine output (>0.5 mL/kg/hr) and mental status over rigid protocols.

Targeted therapies

Targeted therapies for distributive shock address the underlying to reverse and improve hemodynamic stability, following initial . In , prompt administration of broad-spectrum antibiotics within the first hour of recognition is essential to target the infectious source and halt progression. Source control measures, such as surgical drainage of abscesses or removal of infected devices, are critical to eliminate the nidus of and support efficacy. For refractory , defined as persistent despite adequate fluid and vasopressors, intravenous at a dose of 200 mg per day is recommended to address potential relative and enhance vascular responsiveness. In anaphylactic shock, intramuscular epinephrine remains the cornerstone of therapy, administered at a dose of 0.3 to 0.5 mg (1:1000 dilution) into the anterolateral thigh to rapidly counteract and . Adjunctive treatments include antihistamines such as diphenhydramine (25-50 mg IV) to block histamine-mediated effects and supplemental intravenous fluids to restore intravascular volume. Patients require monitoring for biphasic reactions, which occur in up to 20% of cases and may necessitate repeat epinephrine dosing within 1-72 hours. For , typically resulting from acute , atropine (0.5-1 mg IV, repeatable up to 3 mg) is used to treat associated by blocking vagal tone and improving . Vasopressors such as norepinephrine are titrated to maintain above 85-90 mmHg, countering the loss of sympathetic tone. Early spinal stabilization, including and surgical if indicated, prevents further neurological deterioration and supports recovery of vascular tone. In leading to distributive shock from primary , immediate replacement at 100 mg intravenously or intramuscularly, followed by 200 mg continuously over 24 hours, restores levels and stabilizes . If deficiency contributes, as in , at 0.1 mg orally daily is added once stable to address aldosterone deficiency and prevent imbalances. Recent advances include the use of as an adjunctive vasopressor in catecholamine-refractory distributive shock. The ATHOS-3 trial demonstrated that angiotensin II infusion (starting at 20 ng/kg/min) significantly increased in patients with vasodilatory shock compared to , reducing the need for other vasopressors. A 2024 expert consensus supports its role in high-dose vasopressor scenarios, particularly when renin levels are elevated, emphasizing its activation of the renin-angiotensin-aldosterone system to restore vascular tone.

Outcomes

Prognosis

The prognosis of distributive shock varies widely depending on the underlying , with overall mortality rates ranging from 20% to 50%. In , a common form of distributive shock, mortality exceeds 40%, with 30-day rates averaging 34.7% and 90-day rates at 38.5% across multiple international studies. Anaphylactic shock carries a much lower mortality risk of less than 10% when treated promptly, with case fatality rates typically around 0.3% for presentations. , often associated with , has reported in-hospital mortality rates of 10% to 20%. Several factors predict poorer outcomes in distributive shock. Advanced age greater than 65 years is associated with higher mortality, particularly in sepsis-related cases. Comorbidities, such as chronic , further elevate risk. Elevated serum levels above 4 mmol/L serve as an independent predictor of mortality, outperforming some clinical scores in discriminative accuracy. A Sequential Organ Failure Assessment () score greater than 6 indicates severe and correlates with increased death rates. The presence of multi-organ failure approximately doubles the mortality risk compared to single-organ involvement. Mortality trends in distributive shock, particularly , have improved over time due to standardized protocols and early interventions. Rates declined from approximately 50% in the early to around 30% in the . As of 2025, ICU mortality for remains around 30-40% in high-income countries, with some analyses reporting up to 49.7% in major markets, highlighting ongoing challenges and the need for to address global disparities. is generally better for reversible causes, such as , compared to progressive conditions like , where delayed treatment amplifies fatality.

Complications

Distributive shock can lead to a range of acute complications due to profound and hypoperfusion, resulting in . (AKI) occurs in approximately 50% of critically ill patients with associated conditions like (ARDS), often classified using the criteria which define risk, injury, and failure stages based on changes in serum creatinine or urine output. ARDS, characterized by acute hypoxemic and bilateral pulmonary infiltrates, frequently complicates distributive shock, particularly septic forms, with reported incidence rates of 20-50% in patients; among ARDS cases, moderate severity accounts for approximately 47%. (DIC), involving widespread microvascular and consumption of clotting factors, is a common in , exacerbating multi-organ hypoperfusion. Myocardial dysfunction, manifesting as biventricular dilatation and reduced , further impairs despite initial hyperdynamic response in . Multi-organ dysfunction syndrome (MODS) develops in over 30% of cases, involving progressive failure of two or more organ systems due to and endothelial injury. Within MODS, presents as shocked liver with elevated enzymes, , and , while , though less frequent, arises from tissue hypoperfusion and cytokine-mediated muscle breakdown, leading to release and potential renal . Chronic sequelae are prominent in survivors, particularly from septic distributive shock. Post-sepsis syndrome affects up to 50% of survivors, encompassing persistent fatigue, muscle weakness, and cognitive impairments such as memory deficits and that can endure for years. In neurogenic shock, often secondary to , chronic neuropathy may emerge from prolonged autonomic imbalance and nerve ischemia, contributing to sensory and motor deficits. Iatrogenic complications arise from aggressive management strategies. Fluid overload during resuscitation can precipitate , with radiographic evidence of interstitial fluid and in susceptible patients. Vasopressor , essential for maintaining , carries a risk of induced ischemia, particularly digital or limb in 1.8-6% of cases due to .

Research Directions

Current studies

Recent clinical trials have advanced the understanding of management in distributive shock, particularly in cases. The Crystalloid Liberal or Vasopressors Early in (CLOVERS) trial, conducted across 60 centers and involving 1,563 patients with -induced , compared a restrictive strategy—emphasizing early vasopressor initiation—with a approach prioritizing expansion. Published in 2023, the study reported no significant difference in the primary outcome of 90-day mortality (14.0% in the restrictive group versus 14.9% in the liberal group), nor in secondary outcomes such as cardiovascular events or replacement needs. These findings suggest that both strategies are comparably safe in early , challenging prior observational data favoring restrictive approaches. The ANDROMEDA-SHOCK-2 trial, a multicenter randomized conducted from March 2022 to April 2025 across 86 ICUs in 19 countries and involving 1,467 patients with early , compared time (CRT)-targeted personalized hemodynamic to usual care. Published in October 2025, the trial found no significant difference in the hierarchical composite primary outcome of mortality, duration of vital support, and hospital stay at 28 days. The CRT group received less fluid (mean 595 mL vs. 847 mL). Results were consistent across subgroups, including baseline CRT and levels. In vasopressor optimization for distributive shock, a 2024 systematic review and of 10 clinical studies encompassing 1,555 patients examined angiotensin II (ATII) as an adjunctive . The analysis found no overall reduction in mortality with ATII compared to standard catecholamine-based regimens (RR 1.02, 95% CI 0.89-1.16); however, in cases—defined as persistent despite high-dose norepinephrine—ATII enabled a significant reduction in norepinephrine-equivalent dose (mean difference -0.06 μg/kg/min, 95% CI -0.11 to -0.02) at 3 hours of initiation, without increasing adverse events like . This supports ATII's role in weaning vasopressors rather than as a primary mortality-modifying agent in distributive shock. Biomarker-driven has gained traction for in -related distributive shock. The 2025 ADAPT- , a randomized controlled study in critically ill patients with suspected across 41 intensive care units, tested (PCT)-guided protocols for duration against standard care. Involving 2,760 participants, the demonstrated that PCT guidance reduced mean duration by 0.88 days (9.8 days vs. 10.7 days) without increasing 28-day mortality (20.9% vs. 19.4%) or affecting safety outcomes. These results highlight PCT's utility in safely curtailing unnecessary exposure, potentially mitigating and side effects in distributive shock . A 2025 review on distributive shock in cardiac intensive care units (CICUs) indicated that mixed shock—combining distributive (e.g., vasoplegia) and cardiogenic elements—occurs in approximately 24.5% of cardiogenic shock cases, often linked to sepsis or post-cardiac surgery inflammation.

Emerging treatments

Emerging treatments for distributive shock focus on novel strategies to counteract refractory vasodilation, immune dysregulation, and metabolic disruptions, with several investigational approaches advancing through preclinical and early clinical stages. Nitric oxide (NO) scavengers, such as methylene blue and hydroxocobalamin, are under evaluation for their potential to mitigate persistent vasodilation in septic shock. A phase II randomized controlled trial demonstrated that high-dose intravenous hydroxocobalamin improved hemodynamics in patients with septic shock compared to placebo, by scavenging NO and hydrogen sulfide to restore vascular tone. Similarly, a 2024 meta-analysis of randomized controlled trials indicated that methylene blue administration in distributive shock patients shortened mechanical ventilation duration, ICU length of stay, and hospital length of stay, though it did not reduce mortality. Immunomodulatory therapies targeting excessive responses represent another promising avenue, particularly in -induced distributive shock. Preclinical studies in 2025 have shown that PD-1 and IL-6 blockade reduce infiltration, , and bacterial burden in models while preserving tissue integrity and lowering pro-inflammatory . These findings suggest potential for reversing -associated , though human trials are needed to confirm efficacy. Mitochondrial-targeted therapies aim to address cellular energy deficits by modulating succinate metabolism, which accumulates during ischemia-reperfusion in shock states. In animal models of hemorrhagic shock, succinate dehydrogenase inhibitors like dimethyl malonate have slowed succinate buildup, preserved cardiac function, and reduced organ damage by limiting reactive oxygen species production and restoring ATP levels. While human trials are anticipated to begin in 2026, current evidence from swine and rodent models supports their role in mitigating distributive shock's metabolic consequences. Artificial intelligence-driven approaches are enhancing early detection to enable timely intervention in distributive shock. Machine learning models developed in 2025 studies have improved septic shock prediction accuracy, with explainable algorithms achieving superior performance over traditional methods in identifying at-risk ICU patients using and routine data. High-dose therapy, previously explored for its antioxidant effects, has been revisited following the 2023 LOVIT trial, which reported mixed results including a higher of death or persistent at six months in septic patients receiving intravenous . These developments underscore the shift toward precision and multimodal strategies in managing distributive shock.

References

  1. [1]
    Distributive Shock - StatPearls - NCBI Bookshelf - NIH
    Distributive shock, also known as vasodilatory shock, is one of the four broad classifications of disorders that cause inadequate tissue perfusion.Etiology · Epidemiology · Pathophysiology · Treatment / Management
  2. [2]
    Shock - StatPearls - NCBI Bookshelf - NIH
    In distributive shock, there is decreased peripheral vascular resistance and abnormal oxygen extraction. Excitement is a spectrum of physiologic changes, ...
  3. [3]
    classifying microcirculatory flow abnormalities in distributive shock
    Distributive shock, such as occurs during sepsis and septic shock, however ... definition. The clinical introduction of new microcirculatory imaging ...
  4. [4]
    Undifferentiated Hypotension and Shock - Approach to the Patient
    Jul 26, 2024 · Distributive shock is reported in 59%-66%, with about 55%-62% septic shock and about 4% anaphylactic and neurogenic shock. Cardiogenic shock is ...
  5. [5]
    Distributive Shock in Cardiac Intensive Care Unit Patients
    Sep 30, 2025 · Types of Shock · 1. Hypovolemic. Circulatory failure due to loss of adequate circulatory volume. · 2. Cardiogenic · 3. Distributive (Vasodilatory).Types Of Shock · Pathophysiological Insights · Therapeutic Options
  6. [6]
    Definition, classification, etiology, and pathophysiology of shock in ...
    Aug 12, 2025 · Distributive · - Septic shock · - Systemic inflammatory response syndrome (SIRS) · - Neurogenic shock · - Anaphylactic shock · - Drug and toxin- ...<|control11|><|separator|>
  7. [7]
    Septic Shock - StatPearls - NCBI Bookshelf
    Septic shock occurs in response to an inciting agent, which causes both pro-inflammatory and anti-inflammatory immune system activation. This occurs in concert ...Etiology · Pathophysiology · History and Physical · Treatment / Management
  8. [8]
    Sepsis and Septic Shock - Critical Care Medicine - Merck Manuals
    Nov 21, 2014 · Most cases of septic shock are caused by hospital-acquired gram-negative bacilli or gram-positive cocci and often occur in patients who are ...
  9. [9]
    Septic shock: MedlinePlus Medical Encyclopedia
    Nov 25, 2023 · Any type of bacteria can cause septic shock. Fungi and (rarely) viruses may also cause the condition. Toxins released by the bacteria or fungi ...
  10. [10]
    Systemic Inflammatory Response Syndrome - StatPearls - NCBI - NIH
    Jun 20, 2025 · SIRS is diagnosed when ≥2 specific criteria—alterations in temperature, heart rate, respiratory rate, or white blood cell count—are present.
  11. [11]
    Sepsis - Symptoms & causes - Mayo Clinic
    Risk factors · People over age 65. · Infancy. · People with lower immune response, such as those being treated for cancer or people with human immunodeficiency ...
  12. [12]
    Sepsis is the third leading cause of death in U.S. hospitals. But quick ...
    Oct 10, 2023 · Sepsis is the third most common cause of death in US hospitals and affects 1.7 million people nationwide each year, according to the Centers for Disease ...
  13. [13]
    Sepsis and Septic Shock | New England Journal of Medicine
    Dec 4, 2024 · ... sepsis is a dysregulated immune response resulting in organ dysfunction. Progression to sepsis is influenced by pathogen virulence and ...Global Epidemiology · Biologic Features · Immune Dysregulation
  14. [14]
    Anaphylaxis: Recognition and Management - AAFP
    Sep 15, 2020 · The incidence of anaphylaxis in the United States is 2.1 per 1,000 person-years. Most anaphylactic reactions occur outside the hospital setting.
  15. [15]
    Neurogenic Shock - StatPearls - NCBI Bookshelf
    Oct 29, 2023 · Although rare, other potential causes of neurogenic shock include spinal anesthesia, Guillain-Barre syndrome, toxins affecting the autonomic ...
  16. [16]
    The incidence of neurogenic shock in patients with isolated spinal ...
    The incidence of neurogenic shock in cervical cord injuries was 19.3% (95% CI 14.8-23.7%). The incidence in thoracic and lumbar cord injuries was 7% (3-11.1%) ...
  17. [17]
    Adrenal Crisis - StatPearls - NCBI Bookshelf
    An adrenal crisis should be suspected in patients who exhibit acute refractory shock despite receiving adequate fluid resuscitation and vasopressor support.Introduction · Pathophysiology · History and Physical · Differential Diagnosis
  18. [18]
    Adrenal gland & steroid pharmacology - EMCrit Project
    Sep 23, 2025 · Adrenal crisis is usually caused by chronic adrenal insufficiency plus an acute stressor (trigger). Rarely, an adrenal crisis may be caused ...
  19. [19]
    Vasoplegic Syndrome after Cardiopulmonary Bypass in ...
    Vasoplegic syndrome (VS) is a common complication following cardiovascular surgery with cardiopulmonary bypass (CPB), and its incidence varies from 5 to 44%.
  20. [20]
    Distributive Shock: Practice Essentials, Pathophysiology, Etiology
    Jul 21, 2024 · Types of shock · Distributive shock (vasodilation), which is a hyperdynamic process · Cardiogenic shock (pump failure) · Hypovolemic shock ( ...
  21. [21]
    Shock - Critical Care Medicine - Merck Manual Professional Edition
    Cardiogenic shock is a relative or absolute reduction in cardiac output due to a primary cardiac disorder. Obstructive shock is caused by mechanical factors ...
  22. [22]
    Systemic Vascular Resistance - CV Physiology
    SVR can be calculated if cardiac output (CO), mean arterial pressure (MAP), and central venous pressure (CVP) are known. SVR = (MAP - CVP) ÷ CO. Because CVP is ...
  23. [23]
    Shock - Knowledge @ AMBOSS
    May 12, 2025 · Lactate ≤ 2 mEq/L: can be considered normal; Lactate > 2 mEq/L: possibly tissue hypoxia resulting from sepsis, or microcirculatory alterations.
  24. [24]
    qSOFA (Quick SOFA) Score for Sepsis - MDCalc
    The qSOFA (Quick SOFA) Score for Sepsis identifies high-risk patients for in-hospital mortality with suspected infection outside the ICU.
  25. [25]
    Consensus Definitions for Sepsis and Septic Shock - JAMA Network
    Patients with a SOFA score of 2 or more had an overall mortality risk of approximately 10% in a general hospital population with presumed infection. This is ...
  26. [26]
    Septic Shock - EMCrit Project
    Jul 30, 2024 · The most common cause of distributive shock is septic shock. DIC ... Severe infection anywhere in the body can cause septic shock.<|control11|><|separator|>
  27. [27]
    A Physiologic Approach to Hemodynamic Monitoring and Optimizing ...
    Once we have optimized SV and CO to the plateau region of the Frank–Starling curve, then low MAP must indicate low SVR. Therefore, in cases of septic shock, ...2.3. Central Venous Pressure... · 3.6. Stroke Volume Variation... · 9. Svo And Lactate As...<|control11|><|separator|>
  28. [28]
    Venous Oxygen Saturation - StatPearls - NCBI Bookshelf - NIH
    It is a valuable diagnostic and hemodynamic monitoring tool that provides data on mixed venous oxygen saturation, cardiac chamber pressures, CO, and more.
  29. [29]
    Surviving Sepsis Campaign Guidelines 2021 | SCCM
    Oct 3, 2021 · For adults with septic shock on vasopressors, we recommend an initial target mean arterial pressure (MAP) of 65 mm Hg over higher MAP targets.Missing: distributive | Show results with:distributive
  30. [30]
    Norepinephrine - StatPearls - NCBI Bookshelf - NIH
    The average maintenance dose is around 2 to 4 μg/min.[14] Extravasation into local tissue can cause significant ischemia and subsequent necrosis. Should ...Missing: formula | Show results with:formula
  31. [31]
    Septic Shock Treatment & Management - Medscape Reference
    Jun 26, 2024 · The Surviving Sepsis Campaign guidelines emphasize that steroids should not be administered to patients with septic shock unless hemodynamic ...Fluid Resuscitation · Vasopressor Therapy · Corticosteroid Therapy
  32. [32]
    international guidelines for management of sepsis and septic shock ...
    Surviving sepsis campaign: international guidelines for management of sepsis and septic shock 2021. Intensive Care Med. 2021 Nov;47(11):1181-1247.Missing: targeted | Show results with:targeted
  33. [33]
    Anaphylaxis: Emergency treatment - UpToDate
    Aug 12, 2025 · Intramuscular epinephrine injection (preferred) · IV epinephrine by slow bolus (use with caution) · IV epinephrine continuous infusion ...
  34. [34]
    Anaphylaxis: A 2023 practice parameter update
    Dec 17, 2023 · The current standard practice is to treat anaphylaxis with a dosage of epinephrine of 0.01 mg/kg, up to a maximum of 0.3 mg for children and ...
  35. [35]
    Traumatic Spinal Cord Injury (SCI) - EMCrit Project
    Jun 22, 2022 · Guidelines recommend maintaining a MAP of >85-90 mm. Don't delay vasopressor initiation among patients with marked hypotension, particularly in ...
  36. [36]
    Spinal Cord Injuries Treatment & Management - Medscape Reference
    Mar 4, 2024 · Once occult sources of hemorrhage have been excluded, initial treatment of neurogenic shock focuses on fluid resuscitation. Judicious fluid ...
  37. [37]
    Diagnosis and Treatment of Primary Adrenal Insufficiency
    We recommend once-daily fludrocortisone (median, 0.1 mg) and hydrocortisone (15–25 mg/d) or cortisone acetate replacement (20–35 mg/d) applied in two to three ...<|control11|><|separator|>
  38. [38]
    The use of angiotensin II for the management of distributive shock
    Aug 16, 2024 · Overall, a wide consensus was reached on the opinion that combined treatment with drugs with different mechanisms of action may be effective in ...
  39. [39]
    Mortality in sepsis and septic shock in Europe, North America and ...
    May 19, 2020 · Average 30-day septic shock mortality was 34.7% (95% CI 32.6–36.9%), and 90-day septic shock mortality was 38.5% (95% CI 35.4–41.5%).<|control11|><|separator|>
  40. [40]
    217: the significance of neurogenic shock and acute spinal cord injury
    Neurogenic shock occurred in 15% of cases. 43% of cases received high dose steroids. Mortality was 16% and median LOS was 8 days (q1-q3 4–17).
  41. [41]
    Sepsis-related Mortality Among Adults Aged 65 and Over - CDC
    Nov 10, 2021 · Sepsis-related death rates for adults aged 65 and over declined between 2000 (298.8 per 100,000) and 2019 (277.4), with periods of both decline ...
  42. [42]
    Prognostic accuracy of serum lactate, SOFA, qSOFA for mortality
    Apr 30, 2019 · Lactate is an independent prognostic predictor of mortality for patients with sepsis. It has superior discriminative power to qSOFA, and shows discriminative ...
  43. [43]
    Serum Lactate with SOFA Score to Predict Sepsis Mortality
    Apr 18, 2023 · We evaluated a novel scoring system that used serial SOFA scores and serum lactate levels to predict mortality in patients with sepsis.
  44. [44]
    Cardiopulmonary Monitoring of Shock - PMC - PubMed Central - NIH
    Distributive shock is defined by severe vasodilatation of the peripheral vasculature and includes septic, anaphylactic, drug or toxin-induced, and neurogenic ...
  45. [45]
    The Global Burden of Sepsis and Septic Shock - MDPI
    Sepsis death rates in the US have decreased recently, from over 35% in the early 2000s to 15–20% [30,31]. Comparable patterns have been seen in European nations ...
  46. [46]
    Why Has Biomarker-Guided Fluid Resuscitation for Sepsis Not Been ...
    Jun 9, 2025 · Liberal Fluid Therapy in Septic Shock (CLOVERS) involving patients with sepsis-induced hypotension found no significant difference in mortality ...
  47. [47]
    Factors associated with acute kidney injury in acute respiratory ...
    Jul 1, 2019 · Acute kidney injury (AKI) is the most frequent extra-pulmonary organ dysfunction associated with ARDS and affects almost 50% of the patients.Data Collection And... · Statistical Analysis · Aki And Patient Outcomes
  48. [48]
    Epidemiology, Patterns of Care, and Mortality for Patients With Acute ...
    Feb 23, 2016 · The period prevalence of mild ARDS was 30.0% (95% CI, 28.2%-31.9%); of moderate ARDS, 46.6% (95% CI, 44.5%-48.6%); and of severe ARDS, 23.4% (95 ...
  49. [49]
    Disseminated intravascular coagulation is strongly associated with ...
    Dec 1, 2023 · Disseminated intravascular coagulation (DIC) worsens the prognosis of septic shock and contributes to multiple organ failure.
  50. [50]
    Sepsis-induced myocardial dysfunction: pathophysiology and ...
    Mar 23, 2016 · However, despite increased cardiac output and a normal stroke volume, myocardial dysfunction is significant in patients with septic shock.
  51. [51]
    Sepsis-induced multi-organ dysfunction syndrome—a mechanistic ...
    Oct 11, 2017 · ... 30% incidence of MODS (86). Another hypothesis suggests a relationship between MODS following a critical insult, including sepsis, and the ...
  52. [52]
    Multiple Organ Dysfunction Syndrome in Sepsis
    Oct 8, 2024 · Liver failure (“shocked liver”) can be manifested by elevations in liver enzymes and bilirubin, coagulation defects, and failure to excrete ...
  53. [53]
    Post-Sepsis Syndrome
    Post-sepsis syndrome (PSS) is a condition that affects up to 50% of sepsis survivors. It includes physical and/or psychological long-term effects.
  54. [54]
    Fluid overload in the ICU: evaluation and management
    Aug 2, 2016 · In critically ill patients, fluid overload is related to increased mortality and also lead to several complications like pulmonary edema, cardiac failure, ...
  55. [55]
    Limb Loss after Vasopressor Use | PSNet
    Jun 28, 2023 · Limb ischemia is a rare but potentially disabling complication that occurs in 1.8-6% of patients with septic shock.
  56. [56]
    Early Restrictive or Liberal Fluid Management for Sepsis-Induced ...
    However, intravenous fluid resuscitation can create dilutional coagulopathy, fluid overload, and pathogenic edema in the lungs and other organs.
  57. [57]
    Critical Care ATLAS: CLOVERS - ScienceDirect.com
    The CLOVERS trial found a lack of a difference between liberal and restrictive approaches for fluid administration in a 24-h period in patients with sepsis who ...
  58. [58]
    the ANDROMEDA-SHOCK-2 randomized clinical trial - PMC
    Our primary objective is to determine whether capillary refill time (CRT)-targeted resuscitation based on clinical hemodynamic phenotyping is associated with a ...
  59. [59]
    the fundamentals of ANDROMEDA-SHOCK-2 trial - ScienceDirect
    The ANDROMEDA-SHOCK-2 trial will test a multidimensional strategy to personalize early septic shock resuscitation by using simple bedside available tools.
  60. [60]
    ANGIOTENSIN II IN THE TREATMENT OF DISTRIBUTIVE SHOCK
    Aug 1, 2024 · Conclusions: While ATII did not reduce mortality among distributive shock patients, it allowed for significant adjunctive vasopressor reduction ...
  61. [61]
    ANGIOTENSIN II IN THE TREATMENT OF DISTRIBUTIVE SHOCK
    Adverse event rates in the ATHOS-3 trial were similar between both study arms, with thromboembolism being reported in 1.8% of patients receiving ATII.
  62. [62]
    KInetics of Procalcitonin to Reduce Unnecessary aNtibiotic Use
    The study aims to compare the efficacy and safety of an absolute procalcitonin (PCT) value-guided antibiotic initiation protocol and a protocol using the ...
  63. [63]
    Biomarker-Guided Antibiotic Duration for Hospitalized Patients With ...
    Feb 25, 2025 · Conclusions and relevance: Care guided by measurement of PCT reduces antibiotic duration safely compared with standard care, but CRP does not.
  64. [64]
    Distributive Shock in Cardiac Intensive Care Unit Patients - PubMed
    Mixed shock is observed in approximately 24.5% of patients with cardiogenic shock. In cases of out-of-hospital cardiac arrest, outcomes are ...Missing: prevalence | Show results with:prevalence
  65. [65]
    Is Hydroxocobalamin the New Vitamin C? A Budding Strategy to ...
    A recent phase II randomized controlled trial showed an improvement in the hemodynamics of patients with septic shock randomized to hydroxocobalamin compared to ...
  66. [66]
    Effect of methylene blue on outcomes in patients with distributive ...
    Jan 12, 2024 · The use of MB may not reduce mortality in patients with distributive shock, but may shorten the duration of mechanical ventilation, ICU LOS and hospital LOS.Missing: phase II
  67. [67]
    IL-6 and PD-1 antibody blockade combination therapy regulate ...
    Jan 14, 2025 · IL-6/PD-1 dual blockade reduces neutrophil infiltration, lymphocyte apoptosis, and bacterial burden while preserving tissue integrity in sepsis.<|separator|>
  68. [68]
    Dimethyl Malonate Slows Succinate Accumulation and Preserves ...
    Mar 1, 2022 · We hypothesized that DMM would prevent SI buildup during resuscitation in a swine model of hemorrhagic shock, leading to better physiological ...
  69. [69]
    Dimethyl Malonate Slows Succinate Accumulation and Preserves ...
    Jul 9, 2025 · Inhibition of succinate dehydrogenase, which is responsible for the accumulation of succinate in the first (ischemic) phase of shock, e.g., ...
  70. [70]
    Explainable machine learning model for predicting septic shock in ...
    Mar 27, 2025 · The objective of this study is to evaluate and compare the performance of 5 ML algorithms with 1 traditional statistical algorithm in predicting septic shock ...
  71. [71]
    LOVIT Trial - The Bottom Line
    Aug 12, 2022 · The LOVIT trial including 57 patients in the IVC group that were transferred from another ICU where they had already been in for an average of 49 hours.