Trauma

Trauma is a pertinent feature in the history, as haemorrhage invariably accompanies penetrating trauma. The site and approximate amount of blood loss should be assessed. Blunt trauma to the chest is associated with tension pneumothorax, myocardial contusion and cardiac tamponade. Trauma to the pelvis and long bones can result in closed fractures, causing significant haemorrhage that may not always be apparent to the observer. Thermal injury can occur with patients involved in fires, water-heater explosions and gas explosions. Acute onset of paralysis following trauma may be due to spinal or peripheral nerve injury. Disruption to the descending sympathetic pathways with spinal injuries, results in loss of vasomotor tone and consequently hypotension.

Dyspnoea

Although tachypnoea is a physiological accompaniment to blood loss, when dyspnoea is the predominant symptom you should consider pulmonary oedema from the causes of cardiogenic shock. In addition, dyspnoea is also a prominent feature of all the causes of obstructive shock.

Chest pain

The consequences of blunt trauma to the chest have been described above. In the absence of trauma, the presence of chest pain should lead you to consider myocardial infarction (central crushing) and pulmonary embolism (pleuritic).

Precipitating factors

Occasionally patients may be aware of allergens that provoke anaphylaxis. In the community, food products (shellfish, eggs, peanuts) and insect venom (bees, wasps) are common causes. In hospital, penicillin, anaesthetic agents and intravenous contrast media are the major provoking factors. Detailed systemic enquiry for presence of infection may elucidate the offending focus for patients in septic shock. A history of profuse vomiting, diarrhoea or intestinal obstruction (vomiting, constipation, colicky abdominal pain and distension) would indicate gastrointestinal losses as the cause for hypovolaemia.

Inspection

A thorough systematic inspection should be undertaken; burns and sites of bleeding from penetrating trauma may be obvious. Cyanosis is a feature of large pulmonary emboli and tension pneumothoraces. Patients with anaphylaxis often exhibit angio-oedema and urticaria.

Temperature

Patients in shock are generally cold and clammy. With septic shock, however, the skin is warm to the touch and the patient is usually pyrexial.

Pulse

A tachycardia is the earliest measurable indicator of shock; however, it may not be elevated in cases of neurogenic shock. The character of the pulse is usually weak. The rhythm may suggest an arrhythmia as the precipitating factor in cardiogenic shock. Pulsus paradoxus (decrease in amplitude of the pulse on inspiration) is consistent with cardiac tamponade.

JVP

A low JVP is a useful discriminator for hypovolaemic shock, as it will usually be elevated with all causes of cardiogenic and obstructive shock.

Auscultation

Bronchospasm, and consequently wheezing, may be prominent in anaphylactic shock. Unilateral absent breath sounds indicate a pneumothorax, while muffled heart sounds are features of cardiac tamponade. The presence of a new murmur can be due to acute valvular insufficiency as a cause for cardiogenic shock.

■ Pulse oximetry
Although low saturation per se is not very discriminatory, severe impairment of oxygen saturation is associated with pulmonary embolus and pneumothorax. This may be confirmed with ABGs.

■ FBC
With blood loss, a low Hb may be noted, although this will not be evident immediately. A raised WCC occurs with infection. Unfortunately, it will also be raised in most causes of acute physiological stress.

■ U&Es
With significant gastrointestinal losses, low serum sodium and potassium accompanied by raised urea and creatinine are the usual abnormalities.

■ ECG
The ECG may reveal myocardial infarction or the presence of an arrhythmia as the precipitating aetiology. Electrical alternans (alternating large and small QRS complexes) is a specific indicator of pericardial tamponade. Widespread low-amplitude complexes are common in significant pericardial effusion.

■ CXR
May reveal a pneumothorax with deviation of the trachea (although the diagnosis of a tension pneumothorax should be clinical and relieved before a chest X-ray is performed). The cardiac silhouette may be globular in the presence of a pericardial effusion; however, tamponade is still possible with a normal-appearing chest film.

■ Blood cultures
Blood and site-specific cultures are essential in suspected septic shock. The underlying organism may be isolated.

■ Echocardiography
An echocardiogram will be able to demonstrate valvular dysfunction, the presence of tamponade and massive pulmonary embolism (when right heart failure is present).

■ CT pulmonary angiography
For the diagnosis of pulmonary embolism in the presence of shock. Emergency therapeutic measures (such as thrombolysis) may require a formal contrast pulmonary angiogram.

■ CT/MRI spine
May be required to assess the extent and confirm the level of injury.