Surgery - Circulation

Shock

Shock is a clinical state in which the circulation is inadequate to maintain sufficient tissue perfusion.

As a result, the metabolic demands of the body are not met, oxygen delivery to tissues becomes inadequate, and abnormal cellular and organ physiology develops.

Types of Shock

Hypovolaemic shock occurs when there is a reduction in intravascular volume, most commonly due to haemorrhage.

Cardiogenic shock occurs when the heart fails as an effective pumping mechanism. This may result from primary cardiac damage or secondary causes such as cardiac tamponade.

Septic shock results from infection and the release of inflammatory mediators, causing vasodilatation and abnormal distribution of intravascular volume.

Neurogenic shock results from loss of sympathetic vascular tone due to disruption of neurological pathways, such as following spinal cord injury.

Anaphylactic shock results from a severe allergic reaction with mediator release, causing vasodilatation, increased vascular permeability, and maldistribution of circulating volume.

Common Feature of Shock

All forms of shock ultimately result in inadequate effective circulation and insufficient delivery of oxygen to tissues for cellular uptake and aerobic metabolism.

Shock in Trauma

In a shocked trauma patient, hypovolaemic shock secondary to haemorrhage should be assumed until proven otherwise.

Obvious Haemorrhage

Obvious external haemorrhage may occur with open or compound fractures.

Digital or limb amputation may cause severe visible blood loss.

Arterial puncture wounds may also produce rapid and potentially life-threatening haemorrhage.

Hidden Haemorrhage

Closed long-bone fractures may conceal a considerable volume of blood within the surrounding tissues.

Thoracic trauma may result in blood accumulating within the pleural or thoracic cavity.

Abdominal trauma may produce significant intraperitoneal or retroperitoneal haemorrhage.

Closed pelvic fractures can cause massive concealed haemorrhage within the pelvis and retroperitoneum.

Penetrating Wounds

Penetrating wounds involving the neck or mediastinum should be treated with a high index of suspicion.

These injuries may damage major blood vessels or penetrate the heart, potentially producing severe haemorrhage, cardiac tamponade, or cardiogenic shock.

Clinical Assessment of Shock

Clinical assessment of shock should be systematic and include inspection, auscultation, palpation, and bedside monitoring.

Inspection

Peripheral or central cyanosis may indicate inadequate oxygenation or poor tissue perfusion.

A shocked patient may appear cold and clammy because sympathetic activation causes peripheral vasoconstriction and reduced skin perfusion.

Distended jugular veins may suggest an obstructive or cardiogenic cause of shock, such as cardiac tamponade.

Visible trauma should be assessed for evidence of active or previous haemorrhage.

Respiratory rate should be assessed. A normal adult respiratory rate is approximately 12–20 breaths per minute, and tachypnoea may be an early feature of shock.

Confusion, agitation, aggression, drowsiness, or coma may develop as a result of reduced cerebral perfusion or hypoxia.

The jugular venous pressure may provide additional information, although it may be difficult to assess reliably during the rapid evaluation of a trauma patient.

Auscultation

Muffled heart sounds may suggest cardiac tamponade in the appropriate clinical setting.

Pulse Assessment

The pulse should be assessed for rate, rhythm, and volume.

A normal resting adult pulse is approximately 60–100 beats per minute.

The pulse may be bounding, weak or thready, irregular, or absent depending on the patient’s condition.

If a radial pulse cannot be palpated, the carotid and femoral pulses should be assessed.

If no central pulse is present, cardiac arrest should be recognised and appropriate resuscitation commenced immediately.

Capillary Refill Time

Capillary refill time provides a rapid estimate of peripheral perfusion.

Pressure may be applied to the sternum or another appropriate site until the area blanches.

Normal colour should generally return within approximately 2 seconds.

A prolonged capillary refill time may suggest impaired peripheral perfusion and shock.

Bedside Investigations and Monitoring

Blood pressure should be measured and monitored.

Oxygen saturation should be assessed using pulse oximetry.

Continuous cardiac monitoring and an ECG rhythm trace should be obtained where appropriate.

Urine output should be monitored as an important marker of organ perfusion, usually after urinary catheterisation when appropriate during the subsequent trauma assessment.

Estimation of Blood Loss

The clinical findings of pulse, blood pressure, respiratory rate, mental status, and urine output can be used together to estimate the severity of haemorrhagic shock.

Traditional haemorrhagic shock classifications are based on an average 70-kg adult with an estimated circulating blood volume of approximately 5 litres.

Initial Management of Shock

In trauma, shock should initially be treated as haemorrhagic hypovolaemia until another cause has been established.

Management focuses on restoring effective circulation while identifying and controlling the source of bleeding.

Intravenous Access

Two large-bore peripheral intravenous cannulae should be inserted, preferably into the antecubital veins.

Large-bore access, such as 14–16G cannulae, allows rapid administration of fluids and blood products.

If antecubital access cannot be obtained, other accessible peripheral veins should be cannulated using the largest practical bore.

If peripheral venous access is unsuccessful, alternative access such as intraosseous access or central venous access may be required depending on the patient’s age, condition, and available expertise.

A surgical venous cut-down involves direct surgical exposure and cannulation of a vein, traditionally the great saphenous vein, although this is now much less commonly required.

Intraosseous access can provide rapid vascular access in both children and adults when conventional intravenous access cannot be established promptly.

Central venous access using a large-bore catheter or the Seldinger technique may be used by experienced clinicians when indicated.

Initial Fluid Resuscitation

Initial fluid resuscitation should use warmed fluids when appropriate, while avoiding unnecessary large-volume crystalloid administration in actively bleeding trauma patients.

Fluid or blood products may be administered rapidly using pressure-assisted systems when clinically indicated.

Balanced crystalloid solutions such as Hartmann’s solution, also known as Ringer’s lactate, may be used when crystalloid resuscitation is required.

Seldinger Technique

The Seldinger technique is used to insert a catheter into a blood vessel.

A needle is inserted into the desired vessel, and a guidewire is passed through the needle.

The needle is then removed while the guidewire remains in place.

A dilator and catheter are subsequently passed over the guidewire into the vessel, after which the wire is removed and the catheter is secured.

Blood Sampling During Cannulation

Blood should ideally be collected when intravenous access is obtained and before large-volume fluid administration.

A sample should be sent for group and save or group and cross-match, depending on the severity of bleeding and anticipated transfusion requirements.

A full blood count should be obtained to provide baseline haemoglobin, haematocrit, platelet count, and other haematological information.

Urea, electrolytes, and creatinine should be measured as baseline investigations.

Blood glucose should also be checked, either using a bedside glucose meter or laboratory testing.

Additional serum samples may be stored if further investigations are likely to be required.

Adjunctive Measures

Adequate oxygenation and ventilation must be ensured because restoring circulation alone will not correct tissue hypoxia if oxygenation remains inadequate.

Supplemental oxygen should be provided when indicated, and airway protection with intubation may be necessary in severely injured or unconscious patients.

External haemorrhage should be controlled promptly using direct pressure over the bleeding site.

Elevation of an injured limb may occasionally help reduce venous bleeding where appropriate, although direct pressure and definitive haemorrhage control remain more important.

Fluids and Blood Products

Hartmann’s solution or Ringer’s lactate is a balanced crystalloid that may be used for volume replacement.

Other crystalloids, such as normal saline, are also available, although large-volume administration may have disadvantages.

Colloid solutions have historically been used for intravascular volume expansion, but they have a limited role in modern trauma resuscitation.

Blood products provide both circulating volume and, in the case of red blood cells, oxygen-carrying capacity.

Indications for Blood Transfusion

Blood products are indicated when there is significant or ongoing haemorrhage, particularly when the patient shows evidence of severe haemorrhagic shock.

Patients with substantial blood loss may require activation of a major haemorrhage or massive transfusion protocol.

Emergency Blood

When blood is required immediately and the patient’s blood group is unknown, group O red blood cells may be used.

Group O negative red cells are traditionally regarded as universal donor red cells and are commonly prioritised for certain patients, although institutional emergency transfusion protocols may also use group O positive blood in selected circumstances.

Emergency uncross-matched blood can be given without waiting for full compatibility testing when life-threatening haemorrhage is present.

Type-Specific Blood

Type-specific blood can usually be provided once the patient’s ABO and Rh blood group has been determined.

This blood is matched to the recipient’s major blood group but may be issued before full cross-matching is complete when urgent transfusion is required.

Fully Cross-Matched Blood

Fully cross-matched blood undergoes ABO typing, antibody screening, and compatibility testing to maximise compatibility with the recipient.

A patient blood sample must be sent to the laboratory before fully cross-matched blood can be prepared.

Definitive Treatment of Shock

Once initial resuscitation has begun, management should focus on identifying and treating the specific underlying cause of shock.

In haemorrhagic shock, definitive haemorrhage control may require surgery, interventional radiology, endoscopy, fracture stabilisation, or other targeted treatment.

Cardiac Tamponade

Cardiac tamponade is a life-threatening circulatory problem that must be recognised during the primary survey.

It occurs when blood or other fluid accumulates within the pericardial sac and exerts pressure on the heart.

This pressure interferes with diastolic filling, reduces stroke volume, and may result in obstructive shock and cardiovascular collapse.

Traumatic cardiac tamponade most commonly follows penetrating or blunt cardiac injury.

Recognition of Cardiac Tamponade

Beck’s triad consists of hypotension, muffled heart sounds, and raised jugular venous pressure.

These classical findings may not all be present in a trauma patient, particularly in the presence of significant blood loss.

Bedside ultrasound, particularly the FAST or eFAST examination, can rapidly identify pericardial fluid in an unstable trauma patient.

Kussmaul’s Sign

Kussmaul’s sign refers to a paradoxical rise or failure of the jugular venous pressure to fall during inspiration.

Although it may occur in disorders that impair right ventricular filling, it is not a reliable classical sign of acute traumatic cardiac tamponade.

Management of Cardiac Tamponade

Management begins with the ABCDE approach and simultaneous resuscitation.

Definitive treatment requires urgent relief of pericardial pressure and control of the underlying cardiac injury.

Pericardiocentesis may be used as a temporary emergency measure in selected situations when definitive surgical treatment is not immediately available.

In traumatic tamponade, emergency thoracotomy or operative pericardial decompression may be required, particularly when penetrating cardiac injury is suspected.

Emergency Department Thoracotomy

Emergency department thoracotomy may be considered in selected patients with penetrating thoracic trauma who initially had signs of life and then deteriorate into profound shock or cardiac arrest.

It may also be used in exceptional circumstances to control catastrophic intrathoracic haemorrhage, relieve cardiac tamponade, perform open cardiac massage, or temporarily cross-clamp the descending thoracic aorta.

The procedure should only be undertaken in appropriately selected patients by teams with the necessary trauma and surgical expertise.

Situations Where Emergency Thoracotomy Is Unlikely to Be Beneficial

Emergency thoracotomy has a very poor outcome after prolonged cardiac arrest without signs of life.

Outcomes are particularly poor following severe blunt trauma with prolonged absence of vital signs.

The decision depends on the mechanism of injury, duration of resuscitation, presence or absence of signs of life, available expertise, and local trauma protocols.