Evaluation of shock

Overview 
Theory 
Emergencies 
Diagnosis 
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See Differentials for more details

Hypovolemic shock

Loss of body fluid volume due to forms of dehydration such as hyperthermia, burns, excess diuresis, prolonged diarrhea, or lack of usual physiologic oral fluid replacement requires fluid replacement either orally or intravenously.

The intravenous use of a balanced crystalloid solution (e.g., lactated Ringer's [also known as Hartmann solution]) or normal saline is appropriate for resuscitation in a patient with hypovolemic shock. Compared with normal saline, balanced crystalloids were associated with a modestly reduced rate of a composite outcome (of death from any cause, new renal replacement therapy, persistent renal dysfunction) in one randomized trial of critically ill patients.[17] Colloid solutions are more expensive than crystalloid solutions and, for vascular volume replacement, have not shown superiority over crystalloids.[18] [ ]

Bleeding from any cause requires immediate measures to control the source of the bleeding. Volume resuscitation in the form of blood and fluid needs to be instituted immediately.[19] Bleeding following major trauma requires coagulation support and monitoring, and the appropriate use of local hemostatic measures, tourniquets, calcium, desmopressin, and consideration for tranexamic acid.[20] When indicated, appropriate and immediate surgical intervention to control hemorrhage is associated with increased survival and less disability.[20][21]

Tranexamic acid has been shown to reduce mortality in trauma patients with hemorrhage when given within 3 hours of injury.[22][23] One meta-analysis found that delays in administration of tranexamic acid were associated with reduced survival (survival benefit decreasing by about 10% for every 15 minutes of treatment delay until 3 hours, after which there was no benefit) in patients with traumatic bleeding or postpartum hemorrhage.[24]

Some patients may require embolization of bleeding vessels by interventional radiology or exploratory surgery to accomplish hemostasis. Coagulopathies may result due to high-volume blood transfusion (deficient in clotting factors) or consumption of clotting factors due to continued bleeding. This can be corrected with fresh frozen plasma and platelets according to local guidelines.

Cardiogenic shock

Immediate management of myocardial infarction includes revascularization and anticoagulation, either by primary angioplasty or, where these modalities are not available, by thrombolysis and immediate transport to a facility with revascularization capability.[25][26][27]

In primary angioplasty, drug-eluting stents reduce target vessel revascularization compared with bare metal stents.[28] A subanalysis of the SHOCK trial comparing patients treated with coronary artery bypass grafting versus primary angioplasty found no difference in survival or disability outcome.[26]

Acute heart failure may necessitate respiratory support, such as noninvasive or invasive mechanical ventilation, and urgent diuresis or nitrate therapy. Inotropic agents and vasodilator strategies may be used in the appropriate setting. [ ] Pure inotropes are not mandatory in this case, unless significant cardiac hypocontractility is demonstrated or suspected.[29]

Mechanical measures such as inserting an intra-aortic balloon pump may also be considered in patients who are unstable following myocardial infarction or cardiac surgery. The intra-aortic balloon pump augments blood pressure and coronary perfusion by inflating during diastole and deflating during systole.

Extracorporeal membrane oxygenation (ECMO) may be considered for the management of appropriately selected patients with cardiogenic shock.[25][30]

Obstructive shock

Tension pneumothorax is a possible diagnosis in patients with chest trauma, young people with a previous history of pneumothorax, or patients who exhibit signs of hypotension and hypoxia with unilaterally decreased breath sounds. These findings usually mandate immediate needle thoracostomy drainage followed by a formal chest drain.

Patients with hemodynamic compromise and clinical findings suggestive of pericardial tamponade (Beck triad of muffled heart sounds, jugular venous distention, and bradycardia) need urgent evaluation with echocardiography and pericardiocentesis.

Pulmonary embolism is a consideration in patients with recent surgery and immobilization; treatment usually includes anticoagulation, thrombolysis (if there are no absolute contraindications), or rarely surgical or mechanical clot removal.

Distributive shock

Results in inadequate tissue perfusion; comprises anaphylaxis, septic shock, and neurogenic shock.

Anaphylactic shock

May present after exposure to new foods, drugs, blood transfusions, rashes, bites, and stings, and is often associated with bronchospasm. All potentially offending agents should be stopped. In patients with hypotension and signs of anaphylactic shock, intramuscular epinephrine should be given immediately.[31][32][33]

Septic shock

Sepsis is a spectrum of disease, where there is a systemic and dysregulated host response to an infection.[34] Presentation may range from subtle, nonspecific symptoms (e.g., feeling unwell with a normal temperature), to severe symptoms with evidence of multiorgan dysfunction and septic shock. Patients may have signs of tachycardia, tachypnea, hypotension, fever or hypothermia, poor capillary refill, mottled or ashen skin, cyanosis, newly altered mental state, or reduced urine output.[35] Sepsis and septic shock are medical emergencies.

The Third International Consensus Group (Sepsis-3) defines septic shock as a subset of sepsis in which profound circulatory, cellular, and metabolic abnormalities are associated with a greater risk of mortality than with sepsis alone. Both of the following criteria should be present (despite adequate volume resuscitation):[34]

Persistent hypotension requiring vasopressors to maintain mean arterial pressure (MAP) ≥65 mmHg, and
serum lactate >18 mg/dL (>2 mmol/L).

Risk factors for sepsis include: age under 1 year, age over 75 years, frailty, impaired immunity (e.g., due to illness or drugs), recent surgery, or other invasive procedures, any breach of skin integrity (e.g., cuts, burns), intravenous drug misuse, indwelling lines or catheters, and pregnancy or recent pregnancy.[35]

Early recognition of sepsis is essential because early treatment improves outcomes.[35][36][Evidence C][Evidence C] However, detection can be challenging because the clinical presentation of sepsis can be subtle and nonspecific. A low threshold for suspecting sepsis is therefore important. The key to early recognition is the systematic identification of any patient who has signs or symptoms suggestive of infection and who is at risk of deterioration due to organ dysfunction.

Several risk stratification approaches have been proposed. All rely on a structured clinical assessment and recording of the patient’s vital signs.[35][37][38][39] It is important to check local guidance for information on which approach your institution recommends. The timeline of ensuing investigations and treatment should be guided by this early assessment.[39]

Sepsis screening tools are designed to promote the early identification of sepsis and consist of manual methods or automated use of the electronic health record (EHR). These include the Sequential (or Sepsis-related) Organ Failure Assessment (SOFA) score, the quick SOFA (qSOFA) criteria, National Early Warning Score (NEWS), and Modified Early Warning Score (MEWS). There is wide variation in the diagnostic accuracy of these tools, but they are an important component of identifying sepsis early for timely intervention.[36]

The Third International Consensus Group (Sepsis-3) recommends using the SOFA score (primarily validated in patients in intensive care), with a score ≥2 in a patient with a suspected infection being suggestive of sepsis.[34]

[Figure caption and citation for the preceding image starts]: Sequential (or Sepsis-related) Organ Failure Assessment (SOFA) criteriaCreated by BMJ, adapted from Vincent JL, Moreno R, Takala J, et al. The SOFA (Sepsis-related Organ Failure Assessment) score to describe organ dysfunction/failure. On behalf of the Working Group on Sepsis-Related Problems of the European Society of Intensive Care Medicine. Intensive Care Med. 1996;22:707-710. [Citation ends]. com.bmj.content.model.assessment.Caption@6ef4c033

SOFA criteria

Although the presence of a positive qSOFA should alert the clinician to the possibility of sepsis in all resource settings, its poor sensitivity has led the Surviving Sepsis Campaign to advise against using the qSOFA, compared with NEWS or MEWS, as a single screening tool for sepsis or septic shock.[36]

The National Institute for Health and Care Excellence (NICE) UK guideline on sepsis emphasizes the need to "think sepsis" in any patient presenting with possible infection. It recommends structured vital signs monitoring and stratification of risk of severe illness and death according to patient age and setting.[35]

Treatment guidelines have been produced by the Surviving Sepsis campaign and remain the most widely accepted treatment standards.[36][40]

Recommended treatment of patients with suspected sepsis is:

Measure lactate level, and remeasure if initial lactate is elevated (>18 mg/dL [>2 mmol/L]).
Obtain blood cultures before administering antibiotics.
Administer broad-spectrum antibiotics (with methicillin-resistant Staphylococcus aureus [MRSA] coverage if there is high risk of MRSA) for adults with possible septic shock or a high likelihood for sepsis.
For adults with sepsis or septic shock at high risk of fungal infection, empiric antifungal therapy should be administered.
Begin rapid administration of crystalloid fluids for hypotension or lactate level ≥36 mg/dL (≥4 mmol/L). Consult local protocols.
Administer vasopressors peripherally if hypotensive during, or after, fluid resuscitation to maintain MAP ≥65 mmHg, rather than delaying initiation until central venous access is secured. Norepinephrine is the vasopressor of choice.
For adults with sepsis-induced hypoxemic respiratory failure, high-flow nasal oxygen should be given.

Ideally, these interventions should all begin within the first hour following sepsis recognition.[40]

For adults with possible sepsis without shock, where concern for infection persists, antibiotics should be given as soon as possible (within 3 hours) from the time when sepsis was first recognized.[36]

For adults with a low likelihood of infection and without shock, antibiotics can be deferred while continuing to closely monitor the patient.[36]

Patients with severe septic shock may develop corticosteroid insufficiency, diagnosed by adrenocorticotropic hormone stimulation test, or simply based on high vasopressor requirement. Current guidelines recommend that low-dose corticosteroids are given only to adults with septic shock and ongoing requirement for vasopressor therapy (defined as a dose of epinephrine or norepinephrine [adrenaline or noradrenaline] ≥0.25 mcg/kg/min for at least 4 hours after initiation to maintain the target MAP).[36]

ECMO may be considered in carefully selected patients with refractory septic shock.[41][42][43]

For more information on sepsis, please see Sepsis in adults and Sepsis in children.

Neurogenic shock

Patients with suspected neurogenic shock require immediate imaging and possible intervention to reverse potentially reversible deficits, as well as fluid resuscitation to maintain vascular volume and cardiac output.

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