18 | companion AUGUST 2014 | BSAVA 2014

How to deal with a patient with thermal burns

Immediate first aidSince the skin is very slow to cool, it is possible for the burning process to continue for some time after removal of the patient from the heat source. Thus, the first treatment consideration should be to stop the burning process. The recommendation is that the burned areas should be cooled with running tap water (15C/59F) for 2030 minutes. The use of wet compress towels is not as effective at reducing burn depth. Similarly, iced water is also not recommended as this can rapidly decrease the patients core body temperature, causing vasoconstriction, thereby contributing to increased wound depth and reducing circulation to the immediate area. Owners should be advised to avoid hypothermia during transport, by wrapping the patient in clean, dry sheets or blankets. The patients temperature should be carefully monitored to ensure hypothermia does not occur; if the patients temperature drops below 38C active warming will be required to prevent any further drop.

Infection control considerationsBurns patients are at high risk of sepsis, therefore, it is recommended that all personnel wear examination gloves when handling the patient and strict aseptic technique (including sterile gloves, sterile swabs, etc.) must be used when performing any invasive procedure (e.g. placing catheters or collecting blood).

Louise ODwyer, Clinical Director of the PetMedics Veterinary Hospital, helps us approach the patient with thermal burns

Pain managementA multimodal analgesic protocol is recommended for the management of pain. In the acute phase of burn injuries, intravenous opioids should be the primary method of analgesia. The degree of pain associated with burn wounds is incredibly varied, and the use of pain scoring systems, such as the Glasgow Composite Measure Pain Score, is highly recommended. Pure opioid agonists such as methadone (0.10.25 mg/kg i.v. q26h) or morphine (0.10.5 mg/kg s.q. q26h) are recommended for veterinary patients with moderate to severe pain. Ketamine is reported to be useful for the treatment of somatic pain and can be used in conjunction with opioids as a constant rate infusion at 0.150.6 mg/kg/hr. Lidocaine may provide additional analgesia and may also have free radical scavenging properties. Lidocaine is used at a rate of 1.53 mg/kg/hr, but should be used with caution in feline patients. If using a constant rate infusion, a loading dose equal to the hourly rate should initially be administered. Each patient should be evaluated individually for optimal analgesia, again using a pain scoring system to ensure that ongoing analgesia is adequate.

Primary surveyAs with any emergency patient, on initial presentation the burns patient will require a primary survey in order determine the extent of the injury and to commence treatment as required. Priorities include ensuring the patient has a patent airway, and assessing the requirement for ventilatory support, followed by fluid therapy to treat hypovolaemic shock. Oxygen (100%) should be administered to any patient suspected to have smoke inhalation injury to accelerate the elimination of carbon monoxide. Intubation

Thankfully thermal burns are an uncommon presentation in small animal practice; however, dealing with these injuries can be challenging. This article provides a review and logical approach to the assessment and management of a patient with thermal burns.

Extent of burnsIn human medicine thermal burns historically have been classified according to the extent (expressed as a percentage) of the body surface involved and the depth of injury to the skin. The most common scale used for humans is the rule of nines, whereby the adult human body is divided into areas corresponding to 9% of the total body surface area, or multiples of 9%. For example, individual thoracic limbs comprise approximately 9% of the total body surface area; each lower limb, 18%; the head and neck, 9%; the chest and abdomen, 18%; the back, 18%; and the perineum, 1%. The modern burn classification system also classifies burns according to their depth as superficial, superficial partial-thickness, deep partial-thickness or full thickness.

In veterinary patients there is often difficulty in assessing the depth of the injury at initial presentation, and serial examinations over the first 24 hours are usually required to determine the extent of the injury. For some local burn wounds the injury may not be immediately evident to the owner, with the patient being presented 2448 hours post-injury.

18-22 How To.indd 18 21/07/2014 11:00

BSAVA 2014 | companion AUGUST 2014 | 19

or emergency tracheostomy may be required if the airway oedema is severe. In the event of orotracheal injury, endotracheal tubes should be carefully secured, as progressive oedema may make emergency re-intubation more demanding.

In patients injured during house fires, the effects of smoke inhalation will be evident on the upper respiratory tract within the first 24 hours and occur as a result of direct thermal injury. The adherence of irritants to the upper respiratory tract results in the release of inflammatory mediators and reactive oxygen species (by-products of respiration, which can cause damage to cell DNA), increased vascular permeability and oedema formation. This oedema can progress to airway obstruction and bronchospasm that generally peaks at around 24 hours post-injury, and subsequently resolves over the following days. Haemorrhage, mucosal congestion, ulceration and laryngospasm may also occur within the first 24 hours. Additional complications occur due to the adherence of soot to the respiratory mucosa, which allows other irritants to bind to the mucosa.

Vascular access can be complex in the hypovolemic, burnt patient. Ideally, short peripheral catheters should be placed in non-burnt areas. Burnt areas may be used in the first 24 hours; however, dressing the catheters may be complex in these locations, and the sites also become rapidly colonized with bacteria, thus catheters need to be removed within 2448 hours. Intraosseous catheters are an alternative for patients where vascular access is difficult, but this technique can be difficult in adults . Where burns over a large surface area have been sustained, central catheters may be the most suitable option, as these patients may require parenteral nutrition or central venous pressure monitoring. However, the use of central catheters should be avoided

whenever possible due to the risks associated with hypercoagulability in patients with extensive burns.

Fluid therapyFluid resuscitation is a vitally important step in the treatment of severely burnt patients. The aim of fluid resuscitation is to maintain organ perfusion and avoid tissue ischemia using the least amount of fluid required. In most burns cases, there is little change in intravascular volume or haemodynamics for the first 12 hours following the injury, but a delay in fluid resuscitation beyond 2 hours of the burn injury reportedly results in complications in resuscitation and an increase in mortality. In patients with severe burns, after 12 hours there is generally a period of haemodynamic instability (for 2448

hours) despite fluid resuscitation. During this period neither preload nor cardiac output can be normalized using fluid resuscitation until 24 hours after the injury. Severely burnt patients that also have concurrent inhalation injuries, commonly have a marked increase in haemodynamic instability, with a 3050% increase in initial fluid requirements being seen when compared with patients with burn injuries alone.

In human medicine the consensus formula (formerly referred to as the Parkland formula) has become the most widely used resuscitation guideline and is used to calculate the volume of crystalloids required within the first 24 hours following severe burn injury. The formula recommends the administration of isotonic crystalloids at a rate of 4 ml/kg per

Figure 1: Nasal oxygen catheter placed in a bulldog. Oxygen saturation monitoring is also being performed using a pulse oximeter

18-22 How To.indd 19 21/07/2014 11:00

20 | companion AUGUST 2014 | BSAVA 2014

How to deal with a patient with thermal burns

percentage of total body surface area affected in the first 24 hours, with half of this volume being administered over the first 8 hours after presentation. The remaining fluid is administered over the following 16 hours. However, recent studies have found that average fluid volumes administered to burns patients significantly surpass the formula predictions, frequently exceeding 67 ml/kg per percentage of total body surface area affected.

The use of both natural (e.g. albumin) and synthetic (e.g. hydroxyethyl starches) colloids in the resuscitation of burns patients is controversial. This concern is due to the potential for leakage of proteins and large molecules through compromised capillary membranes. The current recommendation is to wait at least 812 hours post-injury before utilizing colloids. The use of colloids may increase colloid osmotic pressure (COP), which has been reported to reduce oedema formation in non-burnt tissue (but not in the burn wound itself).

Secondary surveyFollowing initial stabilization of the patient, a secondary survey should be performed to identify any concurrent injuries. Patients

should be assessed for neurological injuries secondary to trauma, hypoxaemia and carbon monoxide poisoning; ideally this should be performed once the patient is normovolaemic. The airways and thorax require auscultation for stridor, crackles or wheezes, and the adequacy of ventilation should be assessed, ideally via blood gas analysis. The face, oral cavity and pharynx should be examined for the presence of burns or debris that may suggest inhalation injury has occurred.

The eyes should be assessed for conjunctivitis, particulate material and corneal ulceration. Corneal ulcers commonly occur secondary to thermal injury or abrasion by particulate material, so fluorescein staining should always be performed. Topical anaesthetics such as proxymetacaine should be used to facilitate examination behind the third eyelids for foreign material, and the eyes should be copiously flushed with sterile saline. Baseline radiographs ideally should be obtained to assess for any changes as a result of smoke inhalation or traumatic injury. It should be remembered that thoracic radiographs may be normal initially, although bronchial markings may be present.

The development of pulmonary infiltrates or lobar consolidation may suggest pneumonia. Arterial blood gas evaluation is useful to determine parameters related to ventilation, oxygenation and perfusion. However, it should be remembered that both the partial pressure of oxygen (pO2) and oxygen saturation (SpO2) can be misleading in the presence of carbon monoxide inhalation. In this situation pulse oximetry will misread carboxyhaemoglobin as oxyhaemoglobin; co-oximetry should be performed, if available, to determine carboxyhaemoglobin levels as co-oximeters will directly measure carboxyhaemoglobin and oxyhaemoglobin.

Baseline complete blood count, serum biochemistry panel and urinalysis should be performed on admission. If myoglobinuria is noted, this may indicate a need for higher fluid rates to avoid renal tubular damage. Coagulation testing is recommended, as burnt patients may suffer from hyper- or hypocoagulable states. The abdomen should be assessed for compartment syndrome (increased intra-abdominal pressure due to underlying disease processes), gastric distension and other traumatic injuries.

Carbon monoxide toxicityCarbon monoxide is the most commonly inhaled agent producing complications in smoke inhalation patients. The severity of the injury secondary to carbon monoxide toxicity is directly dependent on the concentration of inhaled carbon monoxide, the duration of exposure and the underlying health status of the patient. Carbon monoxide is rapidly absorbed across the alveolar membrane, binding to haemoglobin with an affinity 200 to 250 times greater than that of oxygen. This binding of carbon monoxide prevents the binding of oxygen to haemoglobin molecules, resulting in a functional anaemia. Additional detrimental effects of carbon monoxide toxicity include induction of lipid peroxidation, direct cellular

Figure 2: Partial-thickness burn, involving loss of the epidermis and part of the dermis, due to a wet burn

Figure 3: The patient in Figure 2 demonstrated a good recovery from the injury with no scarring

18-22 How To.indd 20 21/07/2014 11:00

BSAVA 2014 | companion AUGUST 2014 | 21

damage, reperfusion injury and central nervous system demyelination. The administration of supplemental oxygen improves oxygen saturation and decreases the half-life of carboxyhaemoglobin (CO-Hgb). The elimination half-life of carbon monoxide is 5 hours at 21% oxygen or 1 hour at 100% oxygen. Oxygen may be delivered by a variety of routes (e.g. face mask, nasal cannula, oxygen hood, oxygen cage or via intubation), depending on the severity of the respiratory compromise and patient tolerance of the technique (Figure 1). Nasopharyngeal burns may hinder oxygen supplementation via nasal cannula.

MonitoringSevere burns patients may require continuous ECG, direct blood pressure measurement, pulse oximetry, frequent arterial blood gases, electrolytes and lactate (to assess and monitor perfusion), biochemical profiles (to monitor liver and kidney parameters) and complete blood counts (to assess for infection, anaemia, low platelets, etc.), as well as coagulation profiles and a closed urine collection system with a urinary catheter placed aseptically (i.e. using sterile gloves and sterile technique). Urinary catheterization may be useful to allow urine output to be measured, as this is commonly used in patients with severe burn injuries to guide fluid therapy and resuscitation.

Figure 4: Full-thickness burn due to a dry burn (contact with a radiator pipe)

Figure 5: Extensive full-thickness burns in a German Shepherd Dog involved in a house fire

An aseptic peripheral intravenous catheter should be placed as the first choice in burns patients. Another option, in severe cases, would be the placement of a central venous catheter; however, this is often associated with a high incidence of thrombosis and infection in these patients. Serial central venous pressure (CVP) measurements can also be performed when a central venous catheter is placed, and can be used to guide fluid therapy, allowing assessment of volume status and right-sided cardiac function. When CVP cannot be used, lactate can help guide therapy, as lactate values increase as anaerobic metabolism increases, and, as it is a marker of perfusion, will decrease as perfusion increases. Once no longer required, central lines should be removed as early as possible.

Wound managementAs mentioned, one of the priorities in burnt patients is to minimize contamination of the damaged skin. It is vital that the handling of these patients, including for wound management, is performed correctly on every occasion. Hands should be thoroughly washed, using an appropriate antimicrobial detergent, and examination gloves worn, particularly when dealing with superficial burns and partial-thickness superficial burns (Figures 2 and 3). If the patient has

sustained deep partial-thickness or full-thickness burns then sterile gloves should be worn (Figures 4 and 5).

The underlying cause of the injury will determine the initial type of wound management required. Burns arising due to scalds from hot liquids (wet burns) or contact with a heat source (dry burns) generally result in minimal contamination, and therefore require standard lavage procedures. Chemical burns (e.g. from caustic liquids) may require very extensive lavage, to remove the contaminant.

A standard flush can be set up using a litre of warmed lactated Ringers solution (LRS), a fluid administration set and a stopcock with a 35 or 50 ml syringe and an 18 G needle attached, or alternatively a litre of warmed LRS, an administration set and an 18 G needle and be placed into a fluid pressure bag and then the bag inflated. This allows for the optimal pressure (~8 psi) to be used to irrigate the wound. With burns wounds, since they are generally not heavily contaminated with organic matter, the volume of fluid is required to reduce bacterial contamination of the wound surface. Following lavage, the wound requires debridement. This procedure may need to wait until the patient has been stabilized, as it is likely that sedation or general anaesthesia will be required. So interim dressings may be applied (see below).

18-22 How To.indd 21 21/07/2014 11:00

22 | companion AUGUST 2014 | BSAVA 2014

How to deal with a patient with thermal burns

The eschar, the blackened, dead layer of skin seen following a burn, should be removed via debridement (Figure 6) and this can be carried out using a variety of techniques: surgical debridement or application of debridement dressings (e.g. wet-to-dry dressings) are commonly performed techniques. Following debridement, open wound management will generally be performed before the wound is closed surgically, if this is possible. Research has indicated that an earlier and more aggressive surgical approach to debridement results in attenuation of the hypermetabolic response and reduced infection rates. The increased permeability of the burn eschar causes excessive fluid, protein, immunoglobulin and electrolyte loss. In addition, the eschar promotes bacterial growth. Escharectomy is the best means of preventing bacterial infections and sepsis, and exposes a viable bed of tissue for skin grafting or permanent wound closure; this is generally carried out as part of the surgical debridement process.

The most common topical agents used in the UK for the treatment of burn wounds include silver sulfadiazine and honey. Silver sulfadiazine (SSD), a water-soluble cream synthesized from silver nitrate and sodium sulfadiazine, has long been considered the gold standard in topical burn treatment. Silver sulfadiazine has a broad antimicrobial spectrum and fair to good eschar penetration with minimal adverse

side effects in people. Recently, sustained silver-releasing products have been developed that combine a silver agent with a carrier dressing (e.g. a foam dressing). Such products can be applied to partial-thickness burns and can remain in place for 37 days. This eliminates manipulation of the burn site and the pain associated with dressing changes. Care should be taken not to use silver sulfadiazine in patients with kidney or liver failure, as it has been shown to cause a transient leucopenia in human burns patients, which resolves with discontinuation. It is recommended to change to another topical medication if the white blood count begins to fall.

Honey has been used for the treatment of wounds for many years due to its antimicrobial properties, but limited information is available regarding its utility in burn wounds. Antimicrobial properties arise due to its low pH, high osmolarity and the production of hydrogen peroxide. Honey acts by providing a physical barrier to invading organisms and also provides a moist environment for wound healing. The use of honey in open wound management has demonstrated an improved healing rate, reduced contracture, reduction in over-granulation, improved wound strength and a more sterile environment when compared with SSD. Medical grade manuka honey is the authors topical treatment of choice for burn wounds.

Figure 6: Full-thickness burn as a result of contact with a heat mat. The blackened eschar is clearly visible

Nutritional support considerationsNutritional support is an important consideration for the burns patient. Burn patients experience increased muscle catabolism and a negative nitrogen balance, resulting in the loss of lean body mass and often severe muscle wasting, so nutritional support should be addressed as early as possible, ideally within 2448 hours post-injury. Enteral nutrition is recommended over parenteral nutrition as it helps maintain gut motility, decreases plasma endotoxin and inflammatory mediators, preserves first pass nutrient delivery to the liver and decreases intestinal ischemia and reperfusion injury. Parenteral nutrition is only recommended as a consideration in patients that do not tolerate enteral nutrition due to vomiting, oral ulceration, prolonged ileus or during the perioperative period. Even in these situations, enteral nutrition may be provided via oesophagostomy or gastrostomy tubes.

ConclusionBurn patients can be very challenging, from initial management through to their longer term nursing care, because of the complexity of the multifactorial effects on the major body systems. Despite these challenges, they are highly rewarding as they allow us to put all our knowledge into action. Almost every aspect of the patients management needs to be considered from fluid therapy, analgesia, nutrition and wound management, through to respiratory and cardiovascular considerations. Although demanding from initial presentation to recovery, with good nursing and appropriate treatment these cases should have a rewarding outcome.

References are available online and in e-companion

MORE ONLINE

18-22 How To.indd 22 21/07/2014 11:00