In the news this week … voice fire alarms

In the news this week a study in the US has found that firm alarms with that play the voice of a child’s mother will wake the child more effectively than conventional alarms, saving valuable seconds in escaping burning buildings. This study included children between the ages of 5 and 12 years old. This research is now going forward to test whether it is only the mother’s voice that provokes this early more effective waking or if it is any voice.

With this in mind and bonfire night soon approaching, this week we will be covering burns and how these can be managed. Burns are responsible for over 175,000 A&E attendances in the UK every year and result in over 1,000 deaths.

Direct thermal injury causes progressive cell death with temperatures over 45 degrees Celsius, at temperatures over 60 degrees Celsius the cells are killed instantly. The heat is also conducted into surrounding tissue where it causes progressive inflammation injury which increases the capillary permeability and fluid is lost into the extracellular space.

Burns are classified depending on depth, also the depth doesn’t necessarily affect initial management it might dictate later management.

When evaluating a burn it is important to consider the TBSAB percentage (total body surface area burned), think of the area of the palmar surface of the patients hand as 1% of their TBSA, or use the rule of 9s shown in this image.

In full thickness burns the necrotic layer of skin is firm and unyielding. As oedema forms in the deeper tissues, this necrotic tissue resists the swelling and the tissue pressure rises. If the necrotic tissue covers the circumference of a limb for example this can compromise perfusion or if in the torso could restrict ventilation. This can indicate that a surgical division of the tissue (escharotomy) is needed.

Immediately though the priority is to stop the burning process. This is best done with dousing the affected area in cold water and removing smouldering clothes and all constricting items such as jewellery and watches, unless stuck to the skin. After stopping the burning process further cooling can help reduce the local inflammation and also has an analgesic effect, this time with cool water preferably running. Do not use very cold water as prolonged cooling may lead to systemic hypothermia especially if cooling a large area. If available clingfilm should be laid onto the burn wound as soon as possible, but NOT in chemical burns and do NOT wrap the clingfilm around the burn as this can constrict when there is secondary oedema. Cooling can be continued with cool dressings on the cling film. Place burnt hands prehospitally in plastic bags. This can help prevent infection and fluid loss.

When dealing with burns it is important to use an ABCDE approach, being aware that burns can cause hypovolaemic shock due to the amount of fluid exiting the capillaries.

Type of burns

Thermal burns – amount of damage depends on

- The agents heat capacity. Specific heat of water is higher than that of most gases, metals and solids

- Agent’s temperature

- Duration of contact

- Transfer coefficient of the agent and the tissue, steam has a greater heat coefficient than water so steam causes a more severe thermal injury than heated water when the length of exposure is identical

- Conductivity of the tissues in contact with the agent

Flame burns

- If the patients clothes have caught fire the burn will be full thickness


- Low voltage (<1000V – normal main charge) small and full thickness at the point of contact, can cause myocardial damage and arrhythmias so requires and ECG

- High voltage (>1000V) – are extensive and cause widespread tissue damage. Maybe multiple entry and exit wounds as the current can arc across joints. Muscle damage can release myoglobin resulting in renal failure


- Avoid contamination while treating

- Remove clothing

- Irrigate copiously with water for 20 mins or more, saline is more effective if available

- Acids – produce coagulative necrosis and the eschar helps reduce penetration

- Alkalis – cause liquefaction and penetration into deeper tissues is more significant

- Do not cover with clingfilm as it can trap chemicals against skin.

Inhalation injury

This consists of a combination of the following

- Airway burn – inhalation of hot gases (flame, smoke and steam). Normally confined to the upper airway and lead to oedema and risk of obstruction. Swelling develops over several hours and is maximal between 6-24 hours. If this is a concern, securing the airway needs to take priority especially in the emergency department

- Lung injury – occurs if the products of combustion are inhaled into the lower airway where they dissolve in the fluid lining the bronchial tree and alveoli. This leads to chemical lung injury and varying degree of respiratory failure often delayed by hours of even days.

- Systemic toxicity – occurs from absorption of inhaled products of combustion. Most common cause of death due to fire in enclosed spaces. Most important agents are carbon monoxide and cyanides.

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