Critical care management of patients with severe burns and inhalational injury

Abstract

Anaesthetists and critical care physicians involved in emergency care provision must be equipped with the adequate knowledge and skills to accurately assess and manage patients with severe burns. This summary aims to review the key principles in managing patients with severe burns including airway management, fluid resuscitation, sedation, burn care, analgesia and nutrition.

Learning objectives

After reading this article, you should be able to:

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list clinical features that indicate the presence of an inhalational injury
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identify risk factors for and signs of noxious agent involvement in a severe burn
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outline the key aspects of severe burn pathophysiology including burn shock
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describe evidence based practice to commence resuscitation of severe burns patients
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discuss the role of the multi-disciplinary team in burns patient care

Introduction

In the UK, approximately 175,000 patients with burn injuries present to emergency departments each year. In England, 12,375 patients required admission and inpatient management during the financial year 2016/17. Burn injuries account for 180,000 deaths worldwide each year. A specialized multidisciplinary team with a comprehensive understanding of severe burns pathophysiology can ensure the delivery of safe and high quality care to these patients.

There are multiple factors to consider when determining prognosis, including gender, age, size and depth of burn. Up to 35% of burns patients suffer inhalational injury, which is associated with significant complications. A coordinated approach via a strategically developed burns network, is fundamental to reducing morbidity and mortality, while promoting high quality specialist care.

Pathophysiology

A severe burn injury is a significant and life-threatening physiological insult. The resulting tissue trauma triggers local and systemic effects, initiating a profound inflammatory, hypermetabolic and immunological response that can be more severe and persistent than that seen with other types of insults such as trauma, surgery and sepsis. Concomitant inhalational injury can result in direct thermal injury to supraglottic airway structures, leading to mucosal oedema and stridor. Subglottic injury causes chemical pneumonitis, pulmonary infection and acute respiratory distress syndrome (ARDS).

The effects on the cardiovascular system in response to burns are divided into acute and hypermetabolic phases. Hypovolaemia dominates the acute phase, generated by increased capillary permeability resulting in fluid shifts. The hypermetabolic phase results in hypoproteinaemia causing gross tissue oedema, while excess catecholamine synthesis precipitates cardiac dysfunction and acute kidney injury secondary to ischaemia.

Thermal injury can trigger multiple gastrointestinal tract complications. Reduced nutritional intake, increased incidence of gastric mucosal ulceration and bowel wall ischaemia may all result in gastrointestinal haemorrhage. Bacterial translocation across the mucosal wall may also result in sepsis.

Assessment and management

Assessment and management of any trauma patient should follow the principles of Advanced Trauma Life Support teaching. The approach to a burns patient should be no different. Basic initial measures include high flow oxygen, basic monitoring and intravenous access. Following stabilization, transfer to a regional burns unit can be considered based upon locally agreed criteria for referral ( Table 1 ).

Table 1

British Burns Association referral criteria for patients with burn injuries

Extremes of age	<5 years or >60 years
Site	Face Hands or Feet Perineum Flexures Circumferential or full-thickness burns
Inhalation injury	Excluding pure carbon monoxide poisoning
Mechanism of injury	Chemical injury Radiation injury High pressure steam injury Electrical injury Suspicion of non-accidental injury
Size of skin injury	<16 years with >5% TBSA 16 years or over with >10% TBSA
Comorbidities	Cardiorespiratory disease Diabetes mellitus Pregnancy Immunosuppression Hepatic impairment
Associated injuries	Crush injuries Head injury Penetrating injury

Airway

Cervical spine immobilization is essential if there is a significant mechanism of injury to warrant concern until it can be cleared clinically and/or radiologically. Immediate administration of high flow supplemental oxygen therapy to prevent tissue hypoxia and treat smoke inhalation is vital. Mechanism and risk factors for inhalational injury should be identified promptly ( Table 2 ).

Table 2

Risk factors and clinical signs that indicate inhalational injury

Mechanisms	Risk Factors	Clinical signs
Heat Particulate matter deposition and respiratory irritants Asphyxiation and systemic toxicity	Exposure to smoke, flames or chemicals and whether these were either industrial or household Duration of time exposed and whether this was in an enclosed space Burning substances such as plastics or fabrics Obtunded consciousness at scene At scene fatalities or cardiac arrests	Carbonaceous sputum Evidence of burns to the face or neck Oropharyngeal burns (e.g. bulla and/or erythema) Respiratory embarrassment Singed facial or nasal hair Added sounds (wheeze or stridor) Haemoptysis Altered voice Odynophagia or dysphagia Reduced Glasgow Coma Scale (GCS)

Patients with inhalational injury affecting the upper airway are at risk of airway compromise due to supraglottic oedema. Repeated assessment of the airway using clinical features and flexible naseondoscopy (FNE) is essential. Patients with no signs of significant airway oedema who are clinically stable do not necessarily require emergent intubation. However, within this stable group, it may be reasonable to intubate semi-electively if inter-hospital transfer is necessary. Serial clinical and FNE assessments can aid decision making. If features of airway injury are present accompanied by non-reassuring FNE assessment, intubation should be undertaken promptly by a senior clinician with advanced airway skills. In addition to airway compromise, patients may require intubation for respiratory failure, depressed consciousness and facilitation of radiological imaging.

When undertaking emergency tracheal intubation, a clearly devised airway plan should be communicated to the team. In the setting of major burns and likely unfasted patient, it is important to have high levels of preparedness, skilled assistance, equipment, monitoring and clear communication regarding initial airway and rescue airway plans. The technique for intubation will depend on patient factors, urgency, airway skills and equipment availability. The modes of intubation in this scenario include rapid sequence induction, awake fibreoptic intubation and inhalational induction. The use of a small endotracheal tube may be required.

The use of suxamethonium should be limited to within the first 24 hours, due to the risk of hyperkalaemia caused by the increase in extra-junctional nicotinic acetylcholine receptors. Increased receptor numbers can also promote a resistance to non-depolarizing agents, therefore requiring higher doses.

Breathing

A lung protective ventilatory (LPV) strategy ( Table 3 ) should be implemented in those who require intubation. Between 40% and 54% of patients requiring mechanical ventilation will develop ARDS. Rescue interventions, including neuromuscular blocker infusions, prone positioning and extracorporeal membrane oxygenation (ECMO), may be required in cases of severe hypoxaemia.

Table 3

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