Distributive Shock


Article Author:
Nicholas Smith
Richard Lopez


Article Editor:
Michael Silberman


Editors In Chief:
Dustin Constant
Donald Kushner


Managing Editors:
Avais Raja
Orawan Chaigasame
Carrie Smith
Abdul Waheed
Khalid Alsayouri
Trevor Nezwek
Radia Jamil
Erin Hughes
Patrick Le
Anoosh Zafar Gondal
Saad Nazir
William Gossman
Hassam Zulfiqar
Hussain Sajjad
Steve Bhimji
Muhammad Hashmi
John Shell
Matthew Varacallo
Heba Mahdy
Ahmad Malik
Sarosh Vaqar
Mark Pellegrini
James Hughes
Beata Beatty
Beenish Sohail
Nazia Sadiq
Hajira Basit
Phillip Hynes


Updated:
7/29/2019 7:40:14 PM

Introduction

Distributive shock, also known as vasodilatory shock, is one of the four broad classifications of disorders that cause inadequate tissue perfusion. Systemic vasodilation leads to decreased blood flow to the brain, heart, and kidneys causing damage to vital organs. Distributive shock also leads to leakage of fluid from capillaries into the surrounding tissues, further complicating the clinical picture. Due to the complexities of this disease, the causes and treatments for distributive shock are multimodal.[1][2][3]

Etiology

The most common causes of distributive shock in the emergency department are sepsis and anaphylaxis. In cases of trauma, the neurogenic shock should also be on the differential. Other less common causes of distributive shock include adrenal insufficiency and capillary leak syndrome. Drug overdose or toxicity should always be considered, particularly potent vasodilators such as calcium channel blockers and hydralazine.[4][5][6]

Distributive shock as a result of sepsis occurs due to a dysregulated immune response to infection that leads to systemic cytokine release and resultant vasodilation and fluid leak from capillaries. These inflammatory cytokines can also cause some cardiac dysfunction, called septic cardiomyopathy, which can contribute to the shock state.

A common cause is the systemic inflammatory response syndrome due to noninfectious causes such as pancreatitis and burns.

In anaphylaxis, the patient typically has a history of previous exposure to an antigen, although this is not required, with resulting IgE formation to that antigen. These IgE molecules then attach to the surface of mast cells in the tissues and basophils in blood. Consequent exposure to the same antigen results in the IgE-mediated release of histamine from mast cells and basophils, leading to systemic vasodilation and capillary fluid leak.

Toxic shock syndrome should be considered in distributive shock. This disease is caused by Staphylococcus aureus and group A streptococci exotoxins that stimulate systemic cytokine release with resulting vasodilation and capillary leak. Historically, this is associated with both vaginal and nasal tampon use.

Neurogenic shock classically occurs in cases of trauma involving the cervical spinal cord. The sympathetic nervous system is damaged resulting in a decreased adrenergic input to the blood vessels and heart, causing vasodilation with resultant hypotension and paradoxical bradycardia.

The distributive shock from adrenal insufficiency occurs due to decreased alpha-1 receptor expression on arterioles secondary to cortisol deficiency, which results in vasodilation. This is seen in patients on chronic steroids that are stopped suddenly.

Capillary leak syndrome, while rare, should be considered in the edematous patient with distributive shock. It occurs due to low blood albumin. Decreased oncotic pressure leads to fluid loss from the blood into the interstitium.[7][8][9]

Epidemiology

Septic shock is the most common cause of distributive shock seen in the emergency department. The number of patients admitted with severe sepsis now approaches one million per year with mortality rates extending 50%. It’s crucial to note that nearly 50% of septic patients that present with some degree of end-organ damage will have a cryptic shock, meaning they have inadequate tissue perfusion despite a normal blood pressure reading. Anaphylaxis, likely the second leading etiology of distributive shock, can occur at any age regardless of prior history. Nut allergy and history of asthma have been identified as independent predictors of mortality in patients with anaphylaxis, and great care should be taken when monitoring this subset of patients.[10]

Pathophysiology

In most cases, inflammatory mediators play a major role in the development of distributive shock. Inflammatory cytokines released in both sepsis and toxic shock syndrome induce systemic vasodilation and capillary leak, as well as cardiomyopathy. The systemic release of histamine in anaphylaxis results in similar effects.

Interactions between catecholamines and adrenergic receptors in the blood vessels are crucial in other causes of distributive shock. Both norepinephrine and epinephrine stimulate alpha-1 receptors on arterioles to cause vasoconstriction and regulate blood pressure. In the case of neurogenic shock, the sympathetic nervous system is compromised, leading to reduced catecholamine delivery to these receptors. Cortisol is a key regulator of the expression of alpha-1 receptors on the arteriolar surface, but this becomes compromised in patients with adrenal insufficiency.

In effect, the factors leading to vasodilation and shock are multimodal and complex. This necessitates a careful history and physical examination to elucidate the underlying cause and a multi-system approach to treatment.

History and Physical

If possible, a careful and directed history should be taken directly from the patient. Often this is not possible, and information should be collected from the emergency management service, family members, or other witnesses of the inciting event. Symptoms of infection, like shortness of breath, cough, fever, chills, nausea, vomiting, abdominal pain, and dysuria, as well as an immunocompromised status and recent hospitalizations, should be noted as this information may point to sepsis. Additionally, identifying known allergies and a history of anaphylaxis as well as possible.

Exposures to known allergens can aid the identification of the cause of the patient’s presentation. Review the patient’s medications, particularly steroids and anti-hypertensives, and illicit drug use to determine if overdose or intoxication could be contributing to the clinical picture.

While the physical exam is unreliable in determining the source of shock, some findings can be suggestive of underlying etiology. Warm extremities can point to vasodilation as the cause of shock. A careful skin exam should be completed to identify a cutaneous source of infection such as cellulitis, ulcers, or abscess. Urticaria strongly suggests anaphylaxis.

Always consider adrenal insufficiency in a patient with hypotension, no signs of an infection and showing resistance to usual methods of resuscitation.

The physical exam will reveal:

  • Altered mental status
  • Tachycardia and tachypnea
  • Hypotension
  • Warm extremities with bounding pulses in early shock
  • Hypo or hyperthermia
  • Decreased urine output
  • Low oxygen saturation

Evaluation

In undifferentiated patients that present to the emergency department with shock, the exact etiology is often unclear. As always, the evaluation should begin with a primary survey evaluating the airway, breathing, and circulation as well as establishing adequate intravenous (IV) access and hemodynamic monitoring. The patient should be fully exposed and a rapid head to toe examination performed. While definitive airway management is needed in many of these patients, efforts should be made to optimize hemodynamics before intubation to avoid precipitating cardiac arrest. ECG should be obtained rapidly to identify arrhythmias or ischemia which can mimic the clinical picture of distributive shock. Obtain a portable chest x-ray to identify pneumonia, pulmonary edema, or pneumothorax. Bedside ultrasound utilizing the RUSH (Rapid Ultrasound for Shock) exam allows rapid evaluation of global cardiac function and fluid status and helps to identify pericardial tamponade, pulmonary edema, pneumothorax, or occult intra-abdominal hemorrhage. Collect a full spectrum of labs, including lactate, blood and urine cultures, blood gas, and a pregnancy test in females of reproductive age.

Treatment / Management

Regardless of the type of shock, the majority of patients will tolerate and benefit from an initial fluid bolus of 250-500 mL. Patients with distributive shock are significantly more likely to require vasopressor support. The ultimate goal is to achieve adequate tissue perfusion utilizing fluid resuscitation and vasopressors. This can be achieved by targeting a mean arterial pressure of greater than 65 mmHg, which is the approximate critical perfusion pressure for both the heart and kidneys. Adequacy of tissue perfusion can be monitored with multiple modalities, including physical exam, Scv02 greater than or equal to 70%, and laboratory parameters including lactate and base deficit. The pressor choice will vary depending on the suspected etiology of distributive shock.[11][12][13]

In septic shock, the initial pressor of choice is norepinephrine (2 mcg/min to 20 mcg/min), as this offers both alpha-1 and beta-1 stimulation, which will increase peripheral vasoconstriction without significantly compromising cardiac output. Vasopressin (0.03 U/min to 0.04 U/min) is a second-line agent which acts primarily as a vasoconstrictor by binding to V1 receptors. Attention should also be given to aggressive fluid resuscitation (Per the surviving sepsis campaign, 30 mL/kg in the first 3 hours), early antibiotic administration, and source control.

For cases of anaphylactic shock, epinephrine is the pressor of choice, as it offers alpha-1 and beta-1 stimulation similar to norepinephrine but also provides beta-2 stimulation, which stimulates bronchodilation and stabilization of mast cells and basophils. Adjunct interventions will include both H1 and H2 antihistamines, steroids, albuterol, fluids, and potentially glucagon for those using beta-blockers.

The shock that is unresponsive to both fluids and vasopressors may indicate adrenal insufficiency. In such cases, steroids can be given to the increased arteriolar expression of alpha-1 receptors. Hydrocortisone 100 mg is the typical treatment.

In cases where vasopressor drips are not immediately available, and the patient has critically low perfusion pressure (particularly MAP less than 50 mmHg, the critical perfusion pressure to the brain), push dose vasopressors can be utilized. Epinephrine and phenylephrine are common agents of choice for this purpose.

Soon after resuscitation consider diet. Some patients may require tube feedings and others may require parenteral feeding.

Differential Diagnosis

  • Anaphylaxis
  • CO poisoning
  • Adverse drug reaction
  • Neurogenic shock
  • Toxic shock syndrome
  • Cyanide poisoning
  • Cardiogenic shock
  • Hemorrhagic shock
  • Tamponade

Pertinent Studies and Ongoing Trials

Current Guidelines on Resuscitation

  • Initial resuscitation with crystalloid at 30 ml/kg for first 3 hours
  • Screen for sepsis and start antimicrobial therapy for 7-10 days
  • Control source of infection
  • Use vasoactive medications- norepinephrine is first choice and add vasopressin if needed. Dobutamine is also recommneded if hypoperfusion continues
  • Corticosteroids are not recommended is patients adequaely resusciated
  • Blood transfusion should be given if Hb is less than 7g/dl
  • USe of immunoglobulins not recommended
  • Do Not use of anticoagulants
  • Mechanical ventilation at tidal volume of 6 ml/kg or 12 ml/kg in adults with ARDs
  • Glucose control is essential if the blood glucose if more than 180 mg/dl
  • Rebal replacement theraot to maintain fluid balance
  • If acidemia is less than 7.15, administer bicarbnate
  • Start DVT and stress ulcer prophylaxis
  • Consider strating early nutrition
  • Set goals of care

Prognosis

The mortality from distributive shock varies on the cause and can range from 20-80%. Early recognition is the key to improved survival. Higher mortality rates are linked to:

  • Positive blood cultures
  • Advanced age
  • Elevated serum lactate
  • Infection due to pseudomonas
  • Alcohol use
  • Immunocompromised state
  • Poor functional status prior to the event

Pearls and Other Issues

The approach to the distributive shock patient begins with attaining adequate perfusion pressure to vital organs with fluids and vasopressors. Definitive airway management is often necessary but should not precede some degree of hemodynamic stabilization. Rapid identification of the underlying etiology with appropriate treatment is crucial to resolving the cause of pathologic vasodilation and ultimate patient recovery.

Enhancing Healthcare Team Outcomes

Distributive shock is very common in clinical practice and carries high morbidity and mortality.  To improve outcomes, the distributive shock is best managed by an interprofessional team that includes ICU nurses, internists, and physicians from many specialties. The majority of these patients require ICU care and thus the role of the nurse cannot be overstated. The key is to maintain a perfusion pressure of at least 65 mmHg. Fluids are usually the first choice treatment followed by the use of vasopressors. The primary cause of distributive shock must be identified and treated if the outcome is to be improved. Nurses have to monitor the patient for urine output, hemodynamic stability, oxygenation, ventilation and provide prophylaxis against DVT and stress ulcers. The dietitian should be involved early as evidence shows that early enteral nutrition results in better outcomes. The infectious disease consultant and nurse should make recommendations on antibiotics and control of sepsis. The pharmacist should ensure that the patient is on the right antibiotics; in addition, drugs that harm the kidney should be avoided. Clinical rounds must be made by the interprofessional team on a daily basis to make goal care plans and communicate any problems with others.

Outcomes

Patients who do respond to a fluid challenge and have no organ failure have good outcomes. Patients with multiple organ dysfunction and the need for high doses of vasopressors usually have a poor outcome.[14][15] (Level V)


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Distributive Shock - Questions

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A 67-year-old male patient in the cardiac intensive care unit who is two days post coronary artery bypass grafting begins to deteriorate clinically. The bedside nurse tells you that the patient has become hypotensive and tachycardic. His blood pressure is currently 70/40 mmHg, temperature 37.0 C (98.6 F), heart rate of 120 beats per minute and respiratory rate of 20 breaths per minute and is over-breathing the ventilator which is set for 12 breaths per minute. Review of the pulmonary artery catheter reveals the following: cardiac output: 3 liters per minute, cardiac index: 1.8 liters/minute/meter squared, pulmonary capillary wedge pressure: 8 mmHg, and systemic vascular resistance of 2000 dynes-sec/cm. Which of the following is the most likely diagnosis?



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A 73-year-old female with dementia is brought in from a local nursing home with a fever. Initial vital signs reveal temperature 100.0F, heart rate 70 bpm, respiratory rate 16/min, oxygen saturation 93%, and blood pressure 100/64 mmHg. At baseline, the patient is oriented in person and place. However, she is currently confused about her location. Her extremities are warm. The exam is otherwise unrevealing. Her medications include donepezil, memantine, metoprolol, atorvastatin, and lisinopril. Initial laboratory evaluation reveals a creatinine of 1.9 mg/dL with a baseline of 1.0 mg/dL, lactic acid of 4.5 mmol/L, WBC 14000/uL, urinalysis revealing positive nitrite and leukocyte esterase along with WBC count of 120 and too many bacteria to count. Which of the following best describes the patient's current condition?



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An 18-year-old female presents to the emergency department complaining of dyspnea and pruritis. Her heart rate is 130/min, the blood pressure is 95/55 mmHg, and the respiratory rate is 38/min. The patient has wheezes noted in multiple lung fields, and her skin has a diffuse macular rash. The patient's mother informs you that the symptoms suddenly start while they were eating at a restaurant. What is the next best step in the management of this patient?



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A 25-year-old stuntman presents from the set of a movie being filmed nearby complaining that he is unable to move his arms or his legs. He reports that he was supposed to dive into a pool of deep water but missed his jump cue and struck his head on the bottom of the shallow section of the pool. After being rescued by the film crew, he was transported to the emergency department. The patient's vital signs are currently HR 65/min, BP 70/35 mmHg, RR 18/min, and a temperature of 98.4 degrees F. Which of the following is the most likely etiology of this patient's abnormal vital signs?



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An 86-year-old female presents from a nursing home with a "positive UTI" report from a urine sample sent several days ago. On physical exam, the patient is poorly responsive but does open her eyes to commands. She is currently maintaining her airway, with vital signs revealing a heart rate of 142/min, blood pressure of 70/30 mmHg, respiratory rate of 30/min, and temperature of 102.8 degrees F. What would be the next best intervention for this patient?



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An 80-year-old female with a past medical history of rheumatoid arthritis is brought in by her family. They report she has been getting weaker over the last several days. She lives alone and generally does not require help in the house, but when they checked on her today, they noticed she was lethargic, and it appears she has not taken any of her medications for several days. Upon evaluation, the patient is noted to have a heart rate of 120/min, blood pressure of 85/35 mmHg, respiratory rate of 22/min, and temperature of 99.6 degrees F. Lab tests show lactic acid of 4.6 mmol/L and urinalysis reveals too numerous to count bacteria. Resuscitation with a 30cc/kg fluid bolus is initiated along with IV broad-spectrum antibiotics. The patient's blood pressure does not change, and she is given norepinephrine and vasopressin, which results in no change in blood pressure as well. A review of the patient's home medications is done. Which of the following medications is likely responsible for this patient's lack of response to fluid and vasopressor therapy?



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Distributive Shock - References

References

Asmundsson ASE,Bjorklund AR,Fisher GA, Diagnosis of Systemic Capillary Leak Syndrome in a Young Child Treated with Intravenous Immunoglobulin in the Acute Phase. Journal of pediatric intensive care. 2018 Jun;     [PubMed]
Rahulkumar HH,Bhavin PR,Shreyas KP,Krunalkumar HP,Atulkumar S,Bansari C, Utility of Point-of-Care Ultrasound in Differentiating Causes of Shock in Resource-Limited Setup. Journal of emergencies, trauma, and shock. 2019 Jan-Mar;     [PubMed]
Berg DD,Bohula EA,van Diepen S,Katz JN,Alviar CL,Baird-Zars VM,Barnett CF,Barsness GW,Burke JA,Cremer PC,Cruz J,Daniels LB,DeFilippis AP,Haleem A,Hollenberg SM,Horowitz JM,Keller N,Kontos MC,Lawler PR,Menon V,Metkus TS,Ng J,Orgel R,Overgaard CB,Park JG,Phreaner N,Roswell RO,Schulman SP,Jeffrey Snell R,Solomon MA,Ternus B,Tymchak W,Vikram F,Morrow DA, Epidemiology of Shock in Contemporary Cardiac Intensive Care Units. Circulation. Cardiovascular quality and outcomes. 2019 Mar;     [PubMed]
Standl T,Annecke T,Cascorbi I,Heller AR,Sabashnikov A,Teske W, The Nomenclature, Definition and Distinction of Types of Shock. Deutsches Arzteblatt international. 2018 Nov 9;     [PubMed]
Gabbay U,Carmi D,Birk E,Dagan D,Shatz A,Kidron D, The Sudden Infant Death Syndrome mechanism of death may be a non-septic hyper-dynamic shock. Medical hypotheses. 2019 Jan;     [PubMed]
Smith MD,Maani CV, Norepinephrine 2019 Jan;     [PubMed]
Casey JD,Brown RM,Semler MW, Resuscitation fluids. Current opinion in critical care. 2018 Dec;     [PubMed]
Mendelson J, Emergency Department Management of Pediatric Shock. Emergency medicine clinics of North America. 2018 May;     [PubMed]
Silva J,Gonçalves L,Sousa PP, Fluid therapy and shock: an integrative literature review. British journal of nursing (Mark Allen Publishing). 2018 Apr 26;     [PubMed]
Hooper N,Armstrong TJ, Hemorrhagic Shock 2019 Jan;     [PubMed]
Vincent JL,Leone M, Optimum treatment of vasopressor-dependent distributive shock. Expert review of anti-infective therapy. 2017 Jan;     [PubMed]
Ince C, The rationale for microcirculatory guided fluid therapy. Current opinion in critical care. 2014 Jun;     [PubMed]
Lodha R,Kapoor V, Peripheral circulatory failure. Indian journal of pediatrics. 2003 Feb;     [PubMed]
Roumpf SK,Hunter BR, Does the Addition of Vasopressin to Catecholamine Vasopressors Affect Outcomes in Patients With Distributive Shock? Annals of emergency medicine. 2018 Nov 13;     [PubMed]
Nedel WL,Rech TH,Ribeiro RA,Pellegrini JAS,Moraes RB, Renal Outcomes of Vasopressin and Its Analogs in Distributive Shock: A Systematic Review and Meta-Analysis of Randomized Trials. Critical care medicine. 2019 Jan;     [PubMed]

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