Shock (circulatory)
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Shock | |
---|---|
vasopressors[2] | |
Prognosis | Risk of death 20 to 50%[3] |
Frequency | 1.2 million per year (US)[3] |
Shock is the state of insufficient
Shock is divided into four main types based on the underlying cause:
The diagnosis is generally based on a combination of symptoms,
Treatment of shock is based on the likely underlying cause.
Signs and symptoms
The presentation of shock is variable, with some people having only minimal symptoms such as confusion and weakness.
Dry
Low volume
Class | Blood loss (liters) | Response | Treatment |
---|---|---|---|
I | <15% (0.75 L) | min. fast heart rate, normal blood pressure | minimal |
II | 15–30% (0.75–1.5 L) | fast heart rate, min. low blood pressure | intravenous fluids |
III | 30–40% (1.5–2 L) | very fast heart rate, low blood pressure, confusion | fluids and packed RBCs |
IV | >40% (>2 L) | critical blood pressure and heart rate | aggressive interventions |
Signs and symptoms of hypovolemic shock include:
- A rapid, weak, thready pulse due to decreased blood flow combined with tachycardia
- Cool skin due to vasoconstriction and stimulation of vasoconstriction
- Rapid and shallow breathing due to sympathetic nervous system stimulation and acidosis
- Hypothermia due to decreased perfusion and evaporation of sweat
- Thirst and dry mouth, due to fluid depletion
- Cold and mottled skin (livedo reticularis), especially extremities, due to insufficient perfusion of the skin
The severity of hemorrhagic shock can be graded on a 1–4 scale on the physical signs. The
Cardiogenic
Symptoms of cardiogenic shock include:
- Distended jugular veins due to increased jugular venous pressure
- Weak or absent pulse
- Abnormal heart rhythms, often a fast heart rate
- Pulsus paradoxus in case of tamponade
- Reduced blood pressure
- pulmonary congestion
Obstructive
Obstructive shock is a form of shock associated with physical obstruction of the great vessels of the systemic or pulmonary circulation.[13] Several conditions can result in this form of shock.
- Cardiac tamponade[10] in which fluid in the pericardium prevents inflow of blood into the heart (venous return).
- Constrictive pericarditis, in which the pericardium shrinks and hardens, is similar in presentation.
- Tension pneumothorax[10]Through increased intrathoracic pressure, bloodflow to the heart is prevented (venous return).
- Pulmonary embolism is the result of a thromboembolic incident in the blood vessels of the lungs and hinders the return of blood to the heart.
- Aortic stenosis hinders circulation by obstructing the ventricular outflow tract
- Hypertrophic sub-aortic stenosis is overly thick ventricular muscle that dynamically occludes the ventricular outflow tract.
- Abdominal compartment syndrome defined as an increase in intra-abdominal pressure to > 20 mmHg with organ dysfunction.[14] Increased intraabdominal pressure can be due to sepsis and severe abdominal trauma. This increased pressure reduces blood flow back to the heart, thereby reducing blood flow to the body and resulting in signs and symptoms of shock.[15]
Many of the signs of obstructive shock are similar to cardiogenic shock, however treatments differ. Symptoms of obstructive shock include:
- Abnormal heart rhythms, often a fast heart rate.
- Reduced blood pressure.
- Cool, clammy, mottled skin, often due to low blood pressure and vasoconstriction.
- Decreased urine output.
Distributive
Finding | Value |
---|---|
Temperature |
<36 °C (96.8 °F) or >38 °C (100.4 °F) |
Heart rate | >90/min |
Respiratory rate | >20/min or PaCO2 <32 mmHg (4.3 kPa)
|
WBC |
<4x109/L (<4000/mm3), >12x109/L (>12,000/mm3), or ≥10% bands
|
Distributive shock is low blood pressure due to a dilation of blood vessels within the body.[7][17] This can be caused by systemic infection (septic shock), a severe allergic reaction (anaphylaxis), or spinal cord injury (neurogenic shock).
- neutrophils[18]
- The main manifestations of septic shock are due to the massive release of histamine which causes intense dilation of the blood vessels. People with septic shock will also likely be positive for SIRS criteria. The most generally accepted treatment for these patients is early recognition of symptoms, and early administration of broad spectrum and organism specific antibiotics.[19]
- Signs of septic shock include:
- Abnormal heart rhythms, often a fast heart rate
- Reduced blood pressure
- Decreased urine output
- Altered mental status
- capillary permeability.
Signs of anaphylaxis Signs typically occur after exposure to an allergen and may include:- Skin changes, such as hives, itching, flushing, and swelling.
- Wheezing and shortness of breath.
- Abdominal pain, diarrhea, and vomiting.
- Lightheadedness, loss of consciousness.
- High spinal injuries may cause neurogenic shock, which is commonly classified as a subset of distributive shock.[20] The classic symptoms include a slow heart rate due to loss of cardiac sympathetic tone and warm skin due to dilation of the peripheral blood vessels.[20] (This term can be confused with spinal shock which is a recoverable loss of function of the spinal cord after injury and does not refer to the hemodynamic instability.)
Endocrine
Although not officially classified as a subcategory of shock, many endocrinology disturbances in their severe form can result in shock.[citation needed]
- Hypothyroidism (can be considered a form of cardiogenic shock) in people who are critically ill patients, reduces cardiac output and can lead to hypotension and respiratory insufficiency.
- Thyrotoxicosis (cardiogenic shock) may induce a reversible cardiomyopathy.
- Acute adrenal insufficiency (distributive shock) is frequently the result of discontinuing corticosteroid treatment without tapering the dosage. However, surgery and intercurrent disease in patients on corticosteroid therapy without adjusting the dosage to accommodate for increased requirements may also result in this condition.
- Relative adrenal insufficiency (distributive shock) in critically ill patients where present hormone levels are insufficient to meet the higher demands.
Cause
Type | Cause |
---|---|
Low volume | Fluid loss such as bleeding or diarrhea |
Cardiogenic | Ineffective pumping due to heart damage |
Obstructive | Blood flow to or from the heart is blocked |
Distributive | Abnormal flow within the small blood vessels[21] |
Shock is a common end point of many medical conditions.
Pathophysiology
There are four stages of shock. Shock is a complex and continuous condition, and there is no sudden transition from one stage to the next.[24] At a cellular level, shock is the process of oxygen demand becoming greater than oxygen supply.[7]
One of the key dangers of shock is that it progresses by a positive feedback loop. Poor blood supply leads to cellular damage, which results in an inflammatory response to increase blood flow to the affected area. Normally, this causes the blood supply level to match with tissue demand for nutrients. However, if there is enough increased demand in some areas, it can deprive other areas of sufficient supply, which then start demanding more. This then leads to an ever escalating cascade.
As such, shock is a runaway condition of homeostatic failure, where the usual corrective mechanisms relating to oxygenation of the body no longer function in a stable way. When it occurs, immediate treatment is critical in order to return an individual's metabolism into a stable, self-correcting trajectory. Otherwise the condition can become increasingly difficult to correct, surprisingly quickly, and then progress to a fatal outcome. In the particular case of anaphylactic shock, progression to death might take just a few minutes.[6]
Initial
During the Initial stage (Stage 1), the state of
Compensatory
The Compensatory stage (Stage 2) is characterised by the body employing physiological mechanisms, including neural, hormonal, and bio-chemical mechanisms, in an attempt to reverse the condition. As a result of the
Progressive/decompensated
The Progressive stage (stage 3) results if the underlying cause of the shock is not successfully treated. During this stage, compensatory mechanisms begin to fail. Due to the decreased perfusion of the cells in the body,
Refractory
At Refractory stage (stage 4), the vital
Diagnosis
The diagnosis of shock is commonly based on a combination of symptoms, physical examination, and laboratory tests. Many signs and symptoms are not sensitive or specific for shock, thus many clinical decision-making tools have been developed to identify shock at an early stage.[25] A high degree of suspicion is necessary for the proper diagnosis of shock.
The first change seen in shock is increased
Management
The best evidence exists for the treatment of
Fluids
Aggressive intravenous fluids are recommended in most types of shock (e.g. 1–2 liter
For those with hemorrhagic shock, the current evidence supports limiting the use of fluids for penetrating thorax and abdominal injuries allowing mild
Medications
There is no evidence of substantial benefit of one vasopressor over another;
People with anaphylactic shock are commonly treated with
Mechanical support
- Intra-aortic balloon pump (IABP) – a device inserted into the aorta that mechanically raises the blood pressure. Use of Intra-aortic balloon pumps is not recommended in cardiogenic shock.[40]
- Ventricular assist device (VAD) – A mechanical pump that helps pump blood throughout the body. Commonly used in short term cases of refractory primary cardiogenic shock.
- Artificial heart (TAH)
- Extracorporeal membrane oxygenation (ECMO) – an external device that completely replaces the work of the heart.
Treatment goals
The goal of treatment is to achieve a urine output of greater than 0.5 mL/kg/h, a central venous pressure of 8–12 mmHg and a mean arterial pressure of 65–95 mmHg. In trauma the goal is to stop the bleeding which in many cases requires surgical interventions. A good urine output indicates that the kidneys are getting enough blood flow.
Epidemiology
Septic shock (a form of distributive shock), is the most common form of shock. Shock from blood loss occurs in about 1–2% of trauma cases.[33] Overall, up to one-third of people admitted to the intensive care unit (ICU) are in circulatory shock.[41] Of these, cardiogenic shock accounts for approximately 20%, hypovolemic about 20%, and septic shock about 60% of cases.[42]
Prognosis
The prognosis of shock depends on the underlying cause and the nature and extent of concurrent problems. Low volume, anaphylactic, and neurogenic shock are readily treatable and respond well to medical therapy. Septic shock, especially septic shock where treatment is delayed or the antimicrobial drugs are ineffective, however has a mortality rate between 30% and 80%; cardiogenic shock has a mortality rate of up to 70% to 90%, though quick treatment with vasopressors and inotropic drugs, cardiac surgery, and the use of assistive devices can lower the mortality.[43]
History
There is no evidence of the word shock being used in its modern-day form prior to 1743. However, there is evidence that Hippocrates used the word exemia to signify a state of being "drained of blood".[44] Shock or "choc" was first described in a trauma victim in the English translation of Henri-François LeDran's 1740 text, Traité ou Reflexions Tire'es de la Pratique sur les Playes d'armes à feu (A treatise, or reflections, drawn from practice on gun-shot wounds.)[45] In this text he describes "choc" as a reaction to the sudden impact of a missile. However, the first English writer to use the word shock in its modern-day connotation was James Latta, in 1795.
Prior to
References
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- ^ ISBN 978-0-07-148480-0.
- ^ Assessing dehydration and shock. National Collaborating Centre for Women's and Children's Health (UK). April 2009. Retrieved 2019-05-09.
{{cite book}}
:|website=
ignored (help) - ^ a b c d e f g h i Silverman, Adam (Oct 2005). "Shock: A Common Pathway For Life-Threatening Pediatric Illnesses And Injuries". Pediatric Emergency Medicine Practice. 2 (10).
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- ^ "Surviving Sepsis Campaign Responds to ProCESS Trial" (PDF). Surviving Sepsis Campaign. Survivingsepsis.org. Archived from the original (PDF) on 2015-09-24. Retrieved 2015-03-25.
- ^ PMID 17826209.
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- ^ a b "Definition, classification, etiology, and pathophysiology of shock in adults". UpToDate. Retrieved 2019-02-22.
- ISBN 978-0-07-148480-0.
- ^ Armstrong, D.J. (2004). Shock (2nd ed.). In: Alexander, M.F., Fawcett, J.N., Runciman, P.J. Nursing Practice. Hospital and Home. The Adult.: Edinburgh: Churchill Livingstone.
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- ^ Cannon, Walter Bradford (1918). The Nature and Treatment of Wound Shock and Allied Conditions. American Medical Association.
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- ^ Cannon, W. B.; Bayliss, W. M. (1919). "Note on Muscle Injury in Relation to Shock". Special Report Series, Medical Research Council, London. 26 (8). Medical Research Committee, Special Investigation Committee on Surgical Shock and Allied Conditions: 19.
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External links
Classification | |
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External resources |
Distributive |
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Obstructive | |
Low-volume |
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Other |
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Signs and symptoms relating to the circulatory system | |
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Chest pain | |
Auscultation |
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Pulse | |
Other | |
Shock |
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Aortic insufficiency | |
Other endocardium | |
Pericardium | |
Other |
Arterial | |
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Venous |