Shock
last authored: April 2012, David LaPierre
last reviewed:
Shock describes a body state in which tissues receive an inadequate supply of oxygen and nutrients, leading to massive cellular injury and systemic organ dysfunction.
Shock, which is a common end point of many disease processes, is therefore a life-threatening medical emergency, and must be promptly recognized and treated to attain good outcomes.
Shock is most commonly manifest by hypotension, hypoxia, acidosis, and symptoms of organ failure, including altered mental status and decreased renal, liver, and gastrointestinal function.
Brief section on epidemiology: over 50% of people in an ICU are in shock. Over 1 million/year in ED.
Types of Shock
As described, shock is the manifestation of poor tissue perfusion. It can be caused by disturbances in blood volume, blood flow, or distribution/utilization.
Remembering sites of bleeding:
On the floor, plus four more:
- chest
- abdomen
- pelvis
- extremities
hypovolemic shock
main article: hemorrhage
Hypovolemia describes a loss of circulating blood volume. It often results from hemorrhage secondary to injury or gastrointestinal bleeding, though internal hemorrhage can also result in hypovolemia. Other causes include:
- poor fluid intake
- massive diarrhea
- burns
- peritonitis
- pancreatitis
- renal loss
septic/distributive shock
main article: sepsis
Sepsis, or overwhelming bacterial infection, leads to a decreased systemic vascular resistance secondary to toxin release.
anaphylactic shock
main article: anaphylaxis
Anaphylaxis is a systemic allergic reaction in which histamine and other cytokines lead to massive vasodilation and precipitous hypotension.
cardiogenic shock
Cardiogenic shock occurs due to insufficient cardiac output to pump blood through the body. Causes include:
- acute coronary syndrome/myocardial infarction (heart attack)
- congestive heart failure
- arrhythmia
- valvular insufficiency
obstructive shock
Obstructive shock occurs due to decreased blood flow following obstruction to blood flow. Common causes include:
- pulmonary embolism
- cardiac tamponade
- tension pneumothorax or hemothorax
- status asthmaticus
- vascular compression
- increased thoracic pressure
spinal/neurogenic/vasomotor shock
Injury or compression of the spinal cord, especially in the cervical or upper thoracic regions, can lead to loss of systemic vascular tone and subsequent hypotension.
patient is pink and warm following circulatory collapse.
cellular toxin: cyanide, carbon monoxide.
endocrine - hypoglycemia, adrenal insufficiency, myxedema
Approach to Shock
- initial stabilization
- history
- physical exam
- Diagnosing Shock
- Further Investigations
- Differential
Initial stabilization
As with all medical emergencies, it is critical to focus on the ABC's of the patient before moving forward. This includes:
Airway: ensure there is clear passage of air from the mouth to the lungs; this is especially important if the patient has a decreased level of consciousness. Intubation may be required.
Breathing: ensure the patient is adequately breathing and ventilating. Provide supplemental oxygen as needed. Consider positive pressure ventilation.
Circulation: Ensure the patient has adequate IV access; this is normally two large-bore peripheral IVs. Initiate IV fluid resuscitation.
Ensure the ABC's are being effectively managed before moving forward.
History
While assessing a patient in shock, attempt to rapidly understand the events and symptoms leading to their condition. Questions should flow from the clinical presentation. Important potential symptoms include:
- chest pain
- shortness of breath
- trauma
- gastrointestinal bleeding
- fever
- potential sources of infection
Risk factors for causes of shock should also be explored, given diagnostic suspicion. These include:
past medical history
- cardiac disease, risk factors
- coagulopathy
- previous infections
- immunosuppressed states
medications
- anticoagulants
- oral contraceptives (increased risk of blood clot)
Physical Exam
General assessment:
- agitation, confusion
- decreased level of consciousness
- air hunger, respiratory distress
Vital signs:
- tachycardia, including at rest; weak pulses
- bradycardia
- hypotension, decreased pulse pressure
- tachypnea
- fever, or hypothermia
- hypoxia
Skin:
- diaphoresis
- coolness
- pallor
- decreased turgor pressure
Volume status
- jugular venous pressure
- lung crackles
- decreased urine output
- poor peropheral pulses
- delayed capillary refill
In the setting of trauma, a full, head-to-toe examination should be carried out in order to identify hidden injuries and sources of bleeding.
A full examination should also be done to look for potential sources of infection.
Diagnosing Shock
Early shockL inc HR, narrow pulse pressure, anxiety, peripheral vasoconstriction
High output shock |
Low output shock |
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cardiogenic shock |
hypovolemic shock |
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High output hypotension
- lungs, lines, gut, urinary tract
- sinusitis, endocarditis, pancreatitis
sepsis: 1/3 mortality. Incidence is increasing, while
traumatic non-hemorrhagic shock
- tamponade, tension pneumothorax
tamponade: sub-xyphoid
Further Investigations
Initial bloodwork should be as follows:
- CBC
- electrolytes
- blood glucose
- urea and creatinine
- INR, PTT
- liver enzymes
- lactate
- D-dimer
- TSK
- troponin
- urinalysis
- arterial blood gases
- ? extended electrolytes, CK
Other blood tests to consider include:
- blood and urine cultures (if sepsis is suspected)
- blood group and screen (if hemorrhage is suspected)
- ethanol level
Imaging tests include:
- ECG (MI, arrythmia)
- chest X-ray (pneumothorax, pulmonary edema)
- echocardiogram (heart failure)
CT if occult hemorrhage or infection are suspected.
Other invasive tests can include:
- pulmonary artery catheterization
- central venous pressure monitoring
Differential
- thyroid storm
- liver failure
- pancreatitis
- AV ifstula
- trauma
- paget's disease
- analynoss
- adrenal insufficiency
Managing Shock
As described above, immediately assess and treat the ABC's.
Call for help early. Do not send the patient for tests or transfer until initial stabilization is complete.
Airway and breathing
Supplemental oxygen is usually given. Intubation and positive pressure ventilation should be considered and initiated as warranted, especially if transfer is pending.
Circulation
Agressive fluid resuscitation, normally beginning with 1-2L saline, is imperative. However, be cautious in patients with heart failure. Peripheral IVs are frequently sufficient, though central line placement can facilitate administration of fluids and medications, as well as assist with central pressure monitoring.
Frequently reassess vital signs, mental status, and urine output (the best indicator of adequacy of resuscitation).
Inotropes and vasopressors
If the patient's condition does not improve with IV fluids, inotropes or vasopressors should be considered and initiated. Different medications include:
- norepinephrine
- vasopressin
- epinephrine
- phenylephrine
- dobutamine
- dopamine
Reduce oxygen consumption
- reduce hyper-adrenergic state
- analgesia/sedation/muscle relaxation
- reduce temperature
Treating the underlying cause
As resuscitation continues, attempt to identify the underlying cause through further history, physical exam, and investigations.
Sepsis should be treated with antibiotics and drainage of any infected spaces. Give an effective antibiotics within 1 hour. A decrease in survial of % with every ensuing hour.
Obstructive shock should be evaluated for potentially reversible blockages, as in the case of massive PE. Treatment with thrombolytics can be useful in this situation.
Shock + trauma = surgeon
D: deliver oxygen adequately
- follow sats above 92%
- ? transfusion: (Hgb >80-100)
- follow lactate - good serum marker for illness
E: extraction: rule out cyanide, metHgb
Pathophysiology
Blood pressure is a function of cardiac output x systemic vascular resistance. Cardiac output, in turn, is mediated by stroke volume x heart rate.
Stroke volume can be decreased by hypovolemia, heart pump failure, obstruction to flow, adrenal insufficiency, and hypothyroidism.
Systemic vascular resistance, can be reduced in sepsis, anaphylaxis, and neurogenic shock.
for basic homeostasis at the cellular level, leading to systemic organ hypoperfusion, usually due to hypotension.
Pulse pressure is narrowed because of increased diastolic pressure.
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