History and exam
Key diagnostic factors
common
hypotension
Defined as a systolic blood pressure of <90 mmHg, or a mean arterial pressure of <65 mmHg, or a decrease of ≥40 mmHg from baseline.[2]
Occurs in most patients but a normal blood pressure does not rule out shock.
Blood pressure may be normal because compensatory mechanisms may preserve blood pressure through vasoconstriction, even though tissue perfusion and oxygenation are already decreased significantly.[2]
A low diastolic blood pressure suggests arterial vasodilation (such as in anaphylaxis or sepsis).[26]
A narrowed pulse pressure (the difference between systolic and diastolic pressures; normally 35–45 mmHg) suggests arterial vasoconstriction (such as in cardiogenic shock or hypovolaemia) and may occur with rapid tachyarrhythmias.[26]
Hypotension and the resulting stress response will be reflected in a raised lactate, which is a key diagnostic criterion for shock.[2][32]
Practical tip
Older patients can have shock at a normal systolic blood pressure of 110 to 120 mmHg due to atherosclerosis, hypertension, and less functional reflexes.[40]
Evidence: A normal blood pressure does not rule out shock
A systolic blood pressure of >95 mmHg is not a sensitive measure for ruling out moderate or significant blood loss in haemorrhagic shock.
The diagnostic accuracy of a systolic blood pressure of <95 mmHg associated with shock secondary to acute blood loss was assessed in a systematic review of physical findings in patients with hypovolaemia.[41] A random effects model produced a sensitivity of 13% for moderate blood loss and 33% for severe blood loss. A decrease in cardiac output is associated with significant vasoconstriction, leading to decreased peripheral perfusion to maintain arterial pressure.[42]
Several studies show that a normal blood pressure can be associated with markers of inadequate tissue perfusion.[43][44]
These include decreased central venous oxygen saturation (ScvO 2) and significantly increased concentrations of blood lactate.
Persistent hypotension in patients with septic shock without increased lactate levels may only have limited impact on mortality.[45]
tachycardia
Tachycardia may be an earlier sign of shock than hypotension as compensatory mechanisms can maintain cardiac output.[25]
The baseline heart rate may be lower in:[24][25]
Young people and fit adults
Older people
If there is infection, they may not develop an increased heart rate
They may develop a new arrhythmia in response to shock (particularly in septic shock) rather than an increased heart rate.
Patients who are taking certain medications that affect the heart rate response, such as beta-blockers.
The baseline heart rate may be higher in pregnancy.
This is usually 10-15 beats per minute more than normal.
skin changes
Feel for cool, clammy peripheries. Look for a mottled, ashen appearance and sweating.[2][24]
Look for cyanosis of the skin, lips, or tongue.
Practical tip
In early sepsis the skin may be warm. This may become cooler if the patient deteriorates due to reduced peripheral perfusion.[46]
In anaphylaxis there may be patchy/generalised erythema, urticaria, and angio-oedema. These may be absent in 20% of patients with anaphylaxis.[47]
In neurogenic shock the skin may be warm and dry. Loss of sympathetic tone from spinal cord injury leads to vasodilation and no sweating.[35]
oliguria
mental state changes
Assess the patient’s mental status using the Glasgow Coma Scale.[2] [ Glasgow Coma Scale Opens in new window ]
Agitation, confusion, and distress occur early. Unresponsiveness indicates severe and advanced shock.
Confusion is a common and sensitive sign of shock.
Practical tip
Altered cognition is the most sensitive and universal sign of hypoperfusion.[2]
presence of risk factors
Take a history to identify risk factors for shock. The underlying cause must be treated as soon as possible.
Common causes include:
History of sepsis
Recent myocardial infarction
Surgery, trauma, haemorrhage (e.g., ruptured aortic aneurysm, upper gastrointestinal bleed, ectopic pregnancy)
Exposure to known allergens or change in medication (important in suspected anaphylactic shock)
Significant comorbidities (e.g., chronic lung, liver, or kidney disease; ischaemic heart disease; diabetes).
fever
chest pain
Anterior crushing chest pain and ST elevation suggests ST-elevation myocardial infarction. Most commonly present with myocardial infarction.[3][29][36]
Searing chest/back pain with hypertension suggests aortic dissection.
Other causes of chest pain are tension pneumothorax, trauma, pulmonary embolism, cardiac ischaemia , empyema, or oesphageal rupture.
dyspnoea
Look for tachypnoea and increased work of breathing.
Respiratory rate may be increased because of hypoxia (e.g., in pneumonia) but will often remain elevated despite correction of PaO 2 as worsening perfusion generates a metabolic acidosis requiring respiratory compensation.[2]
Never ignore tachypnoea. Respiratory rate is an excellent marker of physiological compromise that is poorly utilised and often overlooked.
uncommon
hypothermia
Persistent hypothermia that is resistant to treatment is rare but is the most obvious clinical sign of end-stage irreversible shock of any cause.[25]
Hypothermia may be due to vasoconstriction and can also be seen in patients with trauma.
Other diagnostic factors
uncommon
abdominal pain
May be due to the underlying cause, which includes the following.[1]
Ruptured abdominal aortic aneurysm, which classically presents with loin pain and is associated with haemorrhagic shock.
Sepsis with a pelvic or abdominal source of infection, which is associated with distributive shock.
Ruptured ectopic pregnancy or ovarian cyst, or postpartum bleeding secondary to a placenta praevia or placental abruption, which are associated with haemorrhagic shock. Anaphylaxis can less commonly cause abdominal pain, vomiting, or incontinence and is associated with distributive shock.
Diabetic ketoacidosis (hypovolaemic shock) is also associated with abdominal pain.
peripheral oedema
raised jugular venous pressure (JVP)
Examine the JVP with the patient lying ideally at 45° to 60° with the neck extended to the opposite side. Measure the vertical height from the sternal angle.
In normal healthy people this should be less than 3 cm.
Marked distention suggests cardiac tamponade, tension pneumothorax, or right heart failure (e.g., massive pulmonary embolism or myocardial infarction).
muffled or quiet heart sounds
This is a typical finding in cardiac tamponade (obstructive shock), especially when there is concurrent raised JVP.[71]
arrhythmia
Examples include fast atrial fibrillation, ventricular tachycardia, and bradyarrhythmias. These are causes of cardiogenic shock.
petechial rash
A classic finding in meningococcal sepsis.
urticarial rash
Look for weals that may be pale, pink, or red, and may look like nettle stings and are usually itchy.
Associated with anaphylaxis, which causes distributive shock.
angio-oedema
Look for swelling that most commonly affects the eyelids and lips, and sometimes in the mouth and throat.[47]
Assess for signs of stridor or bronchospasm.
The patient may have a hoarse voice.
Immediate treatment is needed if the airway is compromised.
Associated with anaphylaxis.
reduced breath sounds on one side of the chest
Indicates a pneumothorax but not necessarily a tension pneumothorax.[103]
Could indicate pneumonia or large pleural effusion.
tracheal deviation
Late sign of a tension pneumothorax.[103]
Tension pneumothorax is associated with obstructive shock.
See Tension pneumothorax.
distended bladder
This is a feature of neurogenic shock.
Neurogenic shock is a type of distributive shock.
A bladder scan can assess the volume of urine.
flaccid paralysis of the limbs
This supports a diagnosis of neurogenic shock.
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