Diffuse axonal injury (DAI) is one of the most serious forms of primary neuronal injury and is associated with high mortality and neurodisability. It results in widespread injury in the brain, not in just one specific area, and occurs as a result of traumatic shearing forces due to rapid acceleration, deceleration and/or rotation of the brain (Fig. 7.2). As the brain moves rapidly backwards and forwards within the skull, the axons are disrupted, particularly at the grey–white matter junction. The clinical manifestations of this will depend on the site and severity of axonal damage, but loss of consciousness is a predominant feature. DAI is typically not demonstrated by computerized tomography (CT) but requires magnetic resonance imaging (MRI).

Despite the seriousness of paediatric head trauma, the vast majority of head injuries in children are mild. Determining which children require neuroimaging is difficult. Various criteria, related to both the history and examination, are used to try to predict the likelihood of intracranial pathology. The current recommendations from the National Institute for Health and Care Excellence (NICE) are found in Box 7.2. These criteria display excellent sensitivity but poor specificity and result in a significant number of normal scans.

Outcome

Although children sustaining a severe traumatic brain injury are likely to have a very long period of recovery, with intensive rehabilitation therapy they can make good progress and recover some function. Cognitive, behavioural and psychiatric problems are the most common long-term sequelae. Cognitive problems result in difficulty with memory, learning and language, while behavioural and psychiatric complications include personality changes, lack of inhibition and depression. These outcomes vary according to the severity of the injury, the age of the child and the pre-morbid condition.

Spinal cord injury

Spinal cord injury is rare in the paediatric age group, occurring most commonly as the result of road traffic collisions. The most common cervical fracture involves the first two vertebrae. In addition, spinal cord injury without radiologic abnormality (SCIWORA) is almost exclusively a paediatric problem. This occurs as a result of the elasticity of the cervical spine allowing significant cord injury in absence of X-ray changes.

Thoracic injury

The most common causes of thoracic injury in children are road accidents and falls. Chest injuries are mostly caused by blunt trauma with only a very few due to penetrating injury, and usually occur in conjunction with trauma to other body parts. The chest wall of children is much more compliant than adults, leading to transfer of impact energy to underlying organs and structures with minimal, if any, external sign of injury or fracture. The presence of rib fractures or mediastinal injury indicates very significant and high energy impact. Common underlying injuries include lung contusions, which develop as energy is transferred rapidly to the lungs causing haemorrhage and oedema in the lung tissue, and pneumothoraces. Great vessel trauma is very rare.

Abdominal injury

Children are more vulnerable to major abdominal injuries as a result of pliable rib cages, which provide little protection to solid organs, which are proportionally larger than in adults. In addition, their abdominal wall is thin and provides less impact absorption.

Most abdominal injuries are caused by blunt trauma, often due to road traffic collisions, seat belt restraint and handlebar injury. The pancreas is particularly at risk from handlebar injury. Intra-abdominal organs bleed readily, resulting in hypovolaemia and circulatory collapse. Acceleration and deceleration forces cause injury to organs, which are moved rapidly and may come into contact with the spine. Abdominal injury can be life-threatening and difficult to diagnose quickly in the absence of external signs. Injury to organs such as the spleen and liver manifest themselves rapidly, while bowel or pancreatic injuries may not become clinically evident for several days. A pro­active approach to identifying abdominal injury is needed, especially in high mechanism injuries. Although focused abdominal sonography for trauma (FAST) is a useful tool, it can miss major solid organ injury and it must be combined with clinical judgement.

Burns and scalds

Burns are injuries to tissues usually caused by heat, but also by friction, electricity, radiation (from the sun, for example) or chemicals. Scalds are caused by contact with hot liquid or steam. They are among the most common of childhood accidents. The vast majority of childhood burns and scalds occur within the home.

Pathophysiology

The severity of burns and scalds is determined by two main factors – the length of contact and the temperature:

Contact temperature (°C)	Duration of contact required to result in epidermal injury
44	6 hours
54	30 seconds
70	<1 second

Burns are classified according to the depth and severity of the tissue damage and extent of body surface area. Previously, burns were described as first, second or third degree, but this has been replaced with the classification shown in Table 7.3.

Question 7.1

Burns

When calculating fluid requirements in children with burns, which ONE of the following statements is correct?

A. 4 mL/kg × % of total body surface area affected should be given within the first 8 hours

B. 0.9% sodium chloride is the preferred intravenous fluid

C. Maintenance requirements are given in addition to resuscitation fluid

D. The volume of resuscitation fluid required is determined by the depth of the burn

E. Urine output is a poor way to monitor adequacy of fluid replacement

Answer 7.1

C. Maintenance requirements are given in addition to resuscitation fluid

Table 7.3

Burn classification

Type of burn	Description
Superficial – simple erythema	Painful, reversible redness of the skin, such as in milder cases of sunburn. Only affects the epidermis so there is no blistering of the skin. Takes several days to heal and may result in peeling over the following days.
Superficial – partial thickness	Involves only the upper layers of the skin (epidermis and into the dermis) and usually heals within two weeks with minimal or no scarring. It appears as erythema with blistering and is painful.
Deep – partial thickness	Extends into the deeper layers of the dermis. The burn will be more yellow or white in colour and there may be blistering. These burns may require surgery such as skin grafting to aid healing. Without surgery, they will usually be associated with delayed healing and risk of significant scarring.
Full thickness	Involves all layers of skin and extends through the entire dermis. As the nerve endings have been fully damaged, these burns are painless and white or brown in colour. Healing takes many months and there is a high risk of complications such as contractures if the burn occurs across a joint. Surgery is usually indicated.

Burn injuries produce both local and systemic reactions. In small burns, the body’s response is localized to the site of the burn. In larger burns affecting over 30% of the total body surface area, and also in deeper dermal burns, a systemic inflammatory response is seen with inflammatory mediators such as cytokines, prostaglandins, histamine and complement being released into the circulation. Capillary leak increases, leading to oedema in the soft tissues and intravascular fluid depletion. Hypovolaemia then results in hypo­perfusion. Myocardial contractility can be reduced by the presence of tumour necrosis factor alpha. Intra-abdominal vasoconstriction occurs, potentially compromising blood flow to organs such as the spleen, kidneys and bowel. Fluid, including electrolytes, is also lost through evaporation from the burn itself and all these changes combine to produce systemic hypotension and end organ hypoperfusion. Catabolism is marked after major burns and early nutritional input is necessary to aid recovery. Infection risk is increased significantly due to direct entry of micro-organisms through the damaged area and because the local immune response is compromised.

As intravascular fluid depletion is a major complication of burns, adequate fluid resuscitation is important. Shock in burn is the result of a combination of factors, including hypovolaemia, microcirculatory injury and the release of local and systemic inflammatory mediators. The foundation of early burn management is the treatment and prevention of shock with intravenous fluid resuscitation.

The heterogeneous nature of children with burns, in terms of their varying size and burn area, has led to the exploration of a number of formulae to guide fluid resuscitation. The most widely accepted version is the Parkland formula:

Volume required over first 24 hours in mL =4×% body surface area of burn×body weight

50% of this volume is administered over the first 8 hours with the remainder administered over the subsequent 16 hours. This mimics the physiological situation as plasma losses are greatest in the first 6–8 hours after a burn with ongoing slower capillary leakage thereafter. As a corollary, the 24-hour period therefore begins from the time of the burn, not the time of initiation of fluid resuscitation. The recommended fluid is crystalloid and, in general, Hartmann’s solution is used as this has the closest electrolyte composition to plasma. Maintenance fluid requirements should be administered in addition to these volumes. The Parkland formula, and others like it, provide only a guide to fluid requirements and clinical response is the final arbiter of adequacy of fluid resuscitation. In particular, maintenance of urine output of 1.0 mL/kg/hour is generally accepted as evidence of euvolaemia in patients with burns.

Adequate analgesia is an essential element of the acute and ongoing management of burns with intravenous opiates often required for most significant burn injuries.

It is generally accepted that burns involving more than 5–7% of the body surface area and certain other burns should be cared for in a specialist burns unit (where possible) (Box 7.3), as these burns are more likely to require surgical input (e.g. skin grafting) and/or specialist monitoring of longer term complications (e.g. contractures).

Box 7.3

Sample criteria for referral to specialist burns unit

Burns greater than 5–7% total body surface area

Burns to face, hands, feet, genitalia, perineum, across major joints

Full thickness burns

Electrical burns

Chemical burns

Inhalation burns

Circumferential burns

Suspicious burns