Burn injuries can result from exposure to heat (including flames, hot liquids or objects; referred to as thermal burns), chemicals, electricity or radiation. The International Burn Injury Database recorded that 81,181 patients attended specialist burn services for assessment and admission in England and Wales between 2003 and 2011 (Stylianou et al. 2014).

Appropriate burn injury assessment and management is critical to ensure the best outcomes for patients. The severity of a burn injury is assessed by its depth, extent and location, the patient's age and the presence of other injuries or diseases. The extent of a burn is expressed as the percentage of the body surface area affected. This is referred to as the total burn surface area (TBSA). There are several standard methods for estimating TBSA: the Lund and Browder chart; Wallace's Rule of Nines; and the Rule of Palm (Hettiaratchy and Papini, 2004).

The Lund and Browder method is a paper chart with an outline of a person divided into several regions, each represented by a number. The chart is shaded to show the burned area and the TBSA is calculated by adding the numbers for each affected region. In babies and children, the head and legs make up different proportions of the body surface area, so the chart includes age‑related numbers for these areas (Hettiaratchy and Papini, 2004). Wallace's Rule of Nines estimates the affected body surface area of an adult using multiples of 9 representing different areas of the body. Different calculations are used for children and infants. The Rule of Palm assumes that the palm (including the fingers) of the person who is burned is about 1% of the body. This can be used to calculate the body surface area burned. However, all of these methods are reported to provide inaccurate estimates of TBSA (Giretzlehner et al. 2013; Parvizi et al. 2014).

One of the major complications associated with severe burns is fluid loss, so replacing lost fluids (fluid resuscitation) is important. The amount of resuscitation fluid needed in the first 24 hours after the burn injury is based on the TBSA and the person's body weight. There are several formulae to calculate fluid requirements; the most commonly used one in the UK is the Parkland formula, devised at the Parkland Memorial Hospital in the USA (Baker et al. 2007). Half of the fluid needed is infused intravenously over the first 8 hours after the burn injury, and the second half is given over the next 16 hours. Children may need additional intravenous background (maintenance) fluids, which also need to be calculated.

Because several calculations are needed to devise a fluid resuscitation protocol, there is potential for error. Inaccuracies in TBSA estimates can have a profound impact on fluid resuscitation outcome, morbidity and mortality (Parvizi et al. 2014). As appropriate fluid resuscitation is essential, physiological parameters are also monitored to assess the patient's response and to help avoid complications. Giving too much fluid can give rise to cardiac failure, an increased risk of infectious complications, acute respiratory distress syndrome, abdominal compartment syndrome, and even death. Giving too little fluid can lead to hypovolaemic shock, organ failure and systemic inflammatory response syndrome (Luo et al. 2015).