Case Report #40: Managing Pain in Adult Burns by Dr Harriet Scott and Dr Joe Hussey

How is the severity of burns assessed?

How is the total body surface area affected assessed?

What is the relevance of the depth of the burn on the perception of pain?

As a trauma injury, patients should be assessed in an ATLS approach before evaluating the burns. A burn is a classic “distracting injury” and therefore possible to miss other significant injuries.

Estimation of the severity of the burn includes the area and the depth of the burn, presence of inhalational injury, patient’s age and co-morbidities.¹

There are several methods for estimating size:

• The rule of nines - area of body regions represent 9% of the total body surface area. This is less commonly used now due to the difference in body proportions with age, although there is an adjusted body map for children to account for altered proportions.
• For smaller burns, the 1% rule - estimating the area of the burn using the area of the patient’s palm and digits which represent 1% total body surface area. In very large burns, this can be used to subtract the areas of unburnt skin from the total body surface area.
• The most commonly used modality is the Lund and Browder chart – a body map allowing for shading of burnt area with adjustment for age. Apps exist for easy calculation.

Estimating depth:

According to their clinical appearance, burn wounds can be assessed as superficial, mid dermal, deep dermal or full thickness. Wounds are often mixed depth. The depth of the wounds has implications on the surgical decisions about excision and skin grafting and, for the interest of the pain physician, impacts the patient’s pain due to the location of nociceptors within the patient’s skin.

• Superficial wounds are confined to the outer strata of the epidermis and are painful. They heal within a few days and do not cause scarring.
• Mid dermal wounds (‘superficial partial thickness’) affect the epidermis and outer layers of dermis with necrosis and inflammation. They are extremely painful. Healing occurs by migration of epidermal cells from wound edges and hair follicles, sweat and sebaceous glands from the deeper dermis.
• Deep dermal wounds (‘deep partial thickness’) extend to the reticular dermis, destroying all superficial skin appendages except a few deep hair follicles. They are less painful, although patients may experience pain from the wound edges. They heal with scarring over a very long time and risk infection. These wounds are often managed with surgical excision and skin grafting.
• Full thickness wounds affect the full thickness of the epidermis and dermis, forming eschar. There is also potential damage to the subcutaneous fat, muscle (causing rhabdomyolysis) or bone. They are less painful* as nociceptors have been functionally compromised or lost. They need surgical excision unless very small.¹

*it is important to appreciate that there is often a mixture of injury depths in a burn wound which may not be evident on macroscopic evaluation. In addition, locally released substances from deeper wounds act to sensitize adjacent superficial areas to nociceptive stimulus. Essentially, the idea that full thickness burns are painless is wrong.

The patient is kept sedated, intubated and ventilated on the BICU. His sedation is managed with infusions of Propofol and Alfentanil. His physiological parameters are optimised by careful management of fluid resuscitation, ventilation, management of inhalational injury with inhaled heparin, salbutamol, acetylcysteine, chest physiotherapy and respiratory toilet. Pressure area care is provided with frequent repositioning, but he is noted to grimace during rolls.

How can pain be assessed in the intensive care population?

What types of pain are experienced in patients with burns?

How can you manage incident pain?

Full discussion about assessment of pain in the intensive care is beyond the scope of this article, but in summary:

• Self-report tools if the patient is able e.g. verbal description scale, visual analogue scale, numeric rating scale
• Observational behavioural scales e.g. critical care pain observation tool (CPOT), behavioural pain scale
• Physiological parameters related to sympathetic-parasympathetic responses e.g. heart rate, blood pressure, respiratory rate, sweating²

Causes of pain in patients with burns can be summarised as:

• Pain from the burn itself
• Pain from other injuries e.g. fractures sustained during patient’s escape from burn environment
• Pain from surgical management of burns - autograft donor sites, escharotomy, fasciotomy and amputation
• Pain from intensive care - tracheal tubes, invasive lines, catheters, pressures areas, position changes, washes and dressing changes