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Chapter 8: Burns and Shock

Learning objectives for this chapter

By the end of this chapter, we would like you:

-To describe the pathophysiology, classification and typical emergency presentation of burn injuries and shock. 

-To explain how to rapidly and accurately assess a patient presenting with burn injury and / or shock in the emergency care setting.

-To explain how to effectively manage a patient presenting with burn injury and / or shock in the emergency care setting.

Introduction to burn injury

Burns are a common reason people present to emergency care. A burn occurs when the tissues of the body are injured by one or more of the following:

  • Heat - thermal burns a caused by flame, flash, scale or direct contact with a hot object. These are the most common types of burns seen in emergency care settings.
  • Smoke inhalation - the inhalation of hot air and noxious chemicals produced by a fire can cause significant damage to the delicate tissues of the respiratory tract. There are three primary types of smoke and inhalational injury: (1) carbon monoxide (CO) poisoning; (2) inhalation injury above the epiglottis; (3) inhalation injury below the glottis, including in the deep tissues of the lungs, the signs of which may take some time to manifest. Smoke inhalation injuries are a significant predictor of mortality.
  • Chemical burns - chemical burns are caused by contact with either an acid, an alkali or an organic compound. Management of burns caused by alkalis is particularly complex, because alkalis are not neutralised by the body's tissue fluids. Many patients who present with chemical burns are unaware of the nature of the substance that caused the burn.
  • Electrical burns - these are caused by the intense heat generated by an electrical current passing through the body's tissues. The severity of an electrical burn depends on the voltage, the resistance of the tissues, the pathway the current took through the body, the body surface area in contact with the current, and the length of time the current flow was sustained. Electrical burns are predominately internal; therefore, a patient is at risk of complications such as dysrhythmia, cardiac arrest, severe metabolic acidosis and / or myoglobinuria leading to acute renal failure.
  • Exposure to extreme cold - this results in cold burns, including frostbite. Frostbite occurs when the tissues freeze. Deep frostbite - which involves acute peripheral vasoconstriction, the formation of ice crystals in the intracellular spaces of the deep tissues and the destruction of cell membranes - may result in tissue death, and amputation may be required.

The severity of a burn depends on: (1) the temperature of the burning agent, (2) the duration of its contact time, and (3) the type of tissue that is injured. 

Assessment and classification of burn injury

There are a variety of different ways in which burns injuries may be classified and described. During the assessment burns are generally classified according to:

  • The depth of the burn:

Classification

Structures Involved

Clinical Appearance

Example Causes

Superficial ('first degree')

Epidermis only

Erythema; mild pain; mild swelling; no vesicles or blisters

Minor sunburn, quick heat flash burns, etc.

Deep ('second degree')

Epidermis and dermis (shallow)

Shiny, fluid-filled vesicles; severe pain; mild to moderate oedema

Flame burn, scald, chemical burn, etc.

Full thickness ('third degree' or 'fourth degree')

Epidermis and dermis (deep); all nerves, glands, hair follicles and re-epithelialising cells

Dry, waxy, black and / or white tissue; visible vessels / muscles / tendons / bones; little pain

Severe flame burn, severe chemical burn, electrical burn, etc.

  • The extent of the burn - the extent of a burn may be measured using the: (1) Lund-Browder chart, or (2) the 'rule of nines'. Both measure the total body surface area affected. Although the Lund-Browder chart is considered more accurate, the rule of nines is often used in emergency care.
  • The location of the burn - this also determines its classification and severity. In the short-term, burns affecting the face and neck, and circumferential burns to the chest and back, are considered the most severe. Face and neck burns also indicate the possibility of inhalational injuries, and circumferential burns often interfere with circulatory function.

Most patients who have sustained a burn are conscious and alert. They are able to participate in the assessment by providing information about the cause of the burn and the symptoms they are experiencing. Unless a burn is very severe and death is imminent, unconsciousness or altered mental status is usually not a result of the burn.

In addition to the actual burn injury, patients may present with a variety of other injuries. These include:

  • Secondary injuries.
  • Gastrointestinal ileus.
  • Shock, including hypovolaemic shock.
  • Hypothermia. 

Emergency management of burn injury

In the management of a burn injury, the priority must be to stabilise the patient's airway, breathing and circulation. Nurses must remove the person from the source of the burn to stop the burning process; often this involves flushing the burn with bags of normal saline. The saline should be warmed, as patients with large burns are prone to rapid heat loss and hypothermia. Patients who have experienced burns generally have all their clothing removed, in an attempt to stop the burning process, and to help preserve the cleanliness of the burn.

The most significant threat to the wellbeing of a patient with a major burn in the emergency care setting involves the massive shift of fluid and electrolytes out of the blood vessels. The net result is volume depletion - which may manifest as hypovolaemic shock. However, there are a number of other immediate complications associated with burn injuries, including those affecting:

  • The cardiovascular system - usually underpinned by circulatory disturbances. In circumferential burns which result in eschar, severe oedema may also obstruct blood supply to the tissues; this is often managed using an escharotomy.
  • The respiratory system - usually due to the inhalational burns. Circumferential burns to the neck and chest which result in eschar may physically restrict the patient's capacity to breathe. Oedema of the airways may also result in their mechanical obstruction.
  • The renal system - usually secondary to hypovolaemia, resulting in renal ischaemia and acute tubular necrosis. With severe burns, myoglobin and haemoglobin may contribute to acute tubular necrosis.

A variety of strategies are used to manage burns and their complications. The goal of these interventions is to stabilise the patient whilst planning for further interventions is undertaken. Common interventions are described following:

  • For severe burns, early intubation is often indicated as a strategy to manage the airways. For more minor burns involving inhalational injury, humidified oxygen and bronchodilators may also be used.
  • All patients with moderate to severe burns are given intravenous fluid therapy. For patients with burns to >15% body surface area, fluid therapy is aggressive.
  • Care of the burn wound begins in the emergency care setting. It initially involves flushing the wound. Burns, particularly when they are large, may be temporarily dressed, using moist sterile gauze. 
  • For severe burns, analgesics are administered, alongside prophylactic intravenous antibiotics. Patients may also be prescribed sedatives, as the experience of major burns can be very psychologically traumatic. 

The psychosocial care of a patient with burns is a particularly important consideration. Burns can significantly and irreversibly alter a person's physical image. Additionally, the situation which caused the burn, and a sudden and painful systemic injury, can be very upsetting. Burns often require long-term management beyond the emergency care setting.

Introduction to shock

Shock is a disorder characterised by a combination of decreased tissue perfusion and impairments in cellular metabolism. Shock may be caused by: (1) reduced blood flow, and / or (2) the maldistribution of blood flow.

Low Blood Flow

Maldistribution of Blood Flow

  • Cardiogenic shock.
  • Hypovolaemic shock (due to absolute or relative hypovolaemia).
  • Neurogenic shock.
  • Anaphylactic shock.
  • Septic shock.

Essentially, all shock involves low blood flow. This creates an imbalance between: (1) the demand for oxygen and nutrients by the body's tissues, which exceeds (2) the supply of oxygen and nutrients to the tissues. Shock progresses through three distinct, but often overlapping, phases:

  • The compensatory stage, where the body attempts to respond to low blood flow and maintain homeostasis. Often during this stage, patients present with increased blood pressure and heart rate. The patient may also present with signs of decreased blood flow to the lungs and gastrointestinal system, and skin which is pale and cool. 
  • The progressive stage, where the body loses its ability to compensate for low blood flow. Patients often present signs of cerebral ischaemia, decreasing blood pressure, signs of decreased coronary perfusion, peripheral perfusion, renal perfusion, hepatic perfusion, acute respiratory distress syndrome, disseminated intravascular coagulation (DIC), and skin which is cold and clammy.
  • The refractory stage, where progressive pooling of the blood results in acute tissue hypoperfusion, anaerobic metabolism and accumulation of lactic acid. Patients present as unresponsive, with a loss of reflexes and unreactive, dilated pupils. Patients will have profound hypotension, severe hypoxaemia and respiratory failure, major metabolic failure, and skin which is mottled and cyanotic. Recovery from the refractory stage of shock is unlikely.

Assessment and emergency management of shock

There is no single diagnostic test which can be used to determine whether a patient is in shock. Typically, shock is diagnosed following: (1) a detailed patient history to identify possible causes of shock, in combination with (2) a critical evaluation of the results of a primary and secondary survey.

When assessing a patient who is suspected to be in shock, a nurse in an emergency care setting must assess (and continually monitor):

  • The patient's neurologic status. In particular, the patient's orientation and level of consciousness should be assessed; changes in these are the first indications of decreased cerebral perfusion.
  • The patient's cardiovascular status, including their heart rate and blood pressure.
  • The patient's respiratory status and blood oxygen saturation.
  • The patient's renal function, including hourly measurements of urine output.
  • The patient's body temperature and changes in their skin; changes in both can indicate severe peripheral vasoconstriction requiring emergency intervention.
  • The patient's gastrointestinal status; shock can lead to rapid gastrointestinal ileus, and nasogastric drainage may be required.

The different types of shock, and their management in the emergency care setting, are described following:

  • Cardiogenic shock - occurs when there is reduced cardiac output. The dysfunction in the heart may be: (1) systolic, where the heart is unable to pump blood forward to the lungs and / or the wider body, or (2) diastolic, where the left and / or right ventricles are unable to fill with blood during diastole. Management focuses on strategies to improve cardiac function. Medications may also be administered - for example, nitrates, diuretics, vasodilators, and β-adrenergic blockers.
  • Hypovolaemic shock - occurs when there is a loss of intravascular fluid volume. This may be: (1) absolute, when fluid is lost from the body directly, or (2) relative, when fluid is lost into the extravascular space. The body may compensate for hypovolaemia to some degree, however aggressive resuscitation is required if 30% of the body's fluids are lost. Management requires aggressive administration of either fluid and / or blood products.
  • Neurogenic shock - occurs (occasionally) following a spinal cord injury at or above the T5 vertebrae.
  • Anaphylactic shock - occurs (occasionally) during anaphylaxis, a severe and life-threatening allergic reaction to a substance. There is massive vasodilation and the loss of fluid into the extravascular space. Management focuses on aggressive fluid therapy.
  • Septic shock - occurs (occasionally) as an acute inflammatory response in patients with sepsis, involving vasodilation and loss of fluid into the extravascular space. The management of septic shock focuses on aggressive fluid therapy and must also include aggressive antibiotic therapy. Other medications, including vasopressors and ionotropic agents, may also be used.

There are a number of general management strategies used for patients who present to emergency care settings in shock. Key interventions for the management of all types of shock in the emergency care setting include:

  • Supplemental oxygen and, in severe shock, mechanical ventilation; the goal is to maintain a blood oxygen saturation of >90% and so avoid hypoxaemia.
  • Resuscitation, via the aggressive administration of either fluid and / or blood products. Patients in shock who are administered fluid and / or blood products are at risk of coagulopathy; they may also be administered with clotting factors.
  • Intravenous drug therapy, to correct decreased tissue perfusion. Drugs administered may include: (1) sympathomimetic drugs, or (2) vasodilator drugs.

Patients with shock can develop two other complex, interrelated problems; (1) systemic inflammatory response syndrome (SIRS), which involves general inflammation of the organs, and / or (2) multiple organ dysfunction syndrome (MODS), which involves the failure of two or more organ systems. Patients with shock and SIRS and / or MODS may present with the signs of shock, as well signs of organ impairment. Management focuses on supporting the failing organ systems. SIRS and MODS can be longer-term conditions which persist beyond the resolution of shock.

Conclusion

Burn injuries and shock are commonly seen in emergency care, and both are a major cause of disability and death. This chapter has described the pathophysiology and classification of burn injuries, their rapid assessment and their management in the emergency care setting. It has also explained the pathophysiology and classification of shock, and how to assess and manage a patient with shock in the emergency care setting.


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