VOL: 101, ISSUE: 46, PAGE NO: 52
Angela Davies, BSc, RGN, DipHE, is clinical nurse specialist - tissue viability, Pennine Acute NHS Trust, North Manchester General Hospital
Frostbite can be defined as acute freezing of the tissues as a result of exposure to low environmental temperatures below the freezing point of intact skin (Strohecker and Parulski, 1997). Research has found that the inflammatory process that occurs with frostbite is similar to that after a thermal burn. (Thermal burns occur when hot metals, scalding liquids, steam, or flames come in contact with a person’s skin.) The severity of a frostbite injury depends on the environmental temperature to which the skin is exposed, and to how long it is exposed to a low temperature.
Any part of the body can be affected by frostbite, but the extremities, such as the feet, ears or hands are the more common sites for it to occur.
The ischaemic damage associated with frostbite is similar to that seen in a thermal burn injury. If the only affected area is the tissue at the surface of the skin, a complete recovery is expected. However, if the blood vessels are affected the damage is likely to be permanent, and gangrene can develop, which can lead to sepsis and even amputation.
As in other types of thermal burns, frostbite injuries can be classified to indicate their severity (Box 1).
Risk factors associated with frostbite
Common risk factors for frostbite include activities such as winter sports, fatigue, smoking, and alcohol intake (Rintamaki, 2000). Because of the increasing popularity of outdoor activities such as hiking and skiing, there has been an increase in cases of frostbite among the general population (Bird, 1999). The use of drugs and alcohol is associated with the increasing number of people with frostbite being diagnosed in urban hospitals (Richard and Staley, 1994).
Pinzur and Weaver (1997) reviewed 20 patients in an urban area with a diagnosis of frostbite and found that, in addition to their thermal injury, all had an overt or covert psychiatric condition. They recommended that patients admitted to an urban hospital with a diagnosis of frostbite should be carefully screened for a psychiatric disorder.
Mr Jones is 36-years-old and has a past medical history of schizophrenia. He was known to the community team and was taking medication. He had been admitted to hospital via the A&E department with necrosis to the dorsum of the right foot, to its plantar aspect (sole), and to the heel and toes (Fig 1).
A week before his admission to hospital he had been assaulted as he walked home from a pub and, during the fight, lost his shoe. He subsequently walked home without the shoe and fell asleep outdoors as he had lost the key to his flat. It was the middle of February and the night was very cold and there was heavy snow. The following morning he woke up and felt well but had no feeling in his right foot. He attended A&E six days later, as his foot had turned black and sensation in it was still diminished.
Mr Jones was reviewed by the orthopaedic surgeon, who diagnosed frostbite, whereupon it was agreed to admit Mr Jones to hospital for surgical debridement, or even amputation, depending on the severity of the injury.
The tissue viability nurse assessed Mr Jones on his admission to hospital to identify any actual and potential problems that would affect the planning and effective delivery of care to his wound.
A physical examination assessed the percentage of skin loss, tissue type, exudate levels, pain, degree of mobility and whether or not there were peripheral foot pulses. The examination gave a clear indication of the extent of tissue damage, and the results were used to guide subsequent management. This holistic assessment was carried out using the trust’s wound care assessment chart.
Assessment of circulation
Assessment of Mr Jones’ circulation using Doppler ultrasound revealed no significant arterial impairment (Baker, 1999), but because of the amount of pain he was experiencing, a full ankle brachial pressure index was not completed. His foot was warm, but because of extensive tissue necrosis, tissue perfusion could not be assessed.
Problems identified during the assessment
The wound: The plantar aspect of the right foot was completely necrotic. The tissue on the great toe and subsequent three toes was hard and also necrotic. The heel had a blister of approximately 8cm x 8cm, 80 per cent of which was necrotic tissue and 20 per cent slough (Fig 1). A blister filled with blood-stained fluid covered the dorsum of Mr Jones’ foot. The frostbites were classified as being third degree injuries (Box 1).
The main concern at this stage was the risk of infection owing to the presence of necrotic devitalised tissue, which is also a major barrier to healing (Hack, 2003).
As Mr Jones had presented to hospital a week after the injury had occurred, his foot was heavily colonised with bacteria. He was therefore treated empirically with intravenous antibiotics - benzylpenicillin and flucloxacillin - before swab results were available.
Odour: This was offensive and was attributed to infection and the presence of devitalised tissue. The severity of wound odour is believed to be associated with the types of micro-organisms colonising the wound - aerobic or anaerobic. Bowler et al (1999) highlighted that, although most aerobic organisms produce a characteristic odour, rarely is it offensive. The putrid odour associated with Mr Jones’ necrotic foot wound suggested that it was infected with anaerobic micro-organisms, therefore a swab was taken as part of the assessment.
The swab report came back positive for Staphylococcus aureus and mixed bacterial skin flora, which was sensitive to flucloxacillin. This was currently being administered intravenously, so the course was completed and no changes were required in the plan of care.
Pain: Mr Jones was reluctant to allow any practitioner to assess his foot fully because of the pain. It was assessed using a visual analogue scale ruler, which identified that the pain was severe. Mr Jones was unwilling to allow any dressings to touch his foot. Health-related quality of life studies have shown consistently that pain improves significantly with effective treatment, which promotes healing (Franks and Moffatt, 1998). Following the assessment, the tissue viability nurse referred Mr Jones to the pain team to ensure that he received adequate pain relief.
Exudate: The amount of exudate from Mr Jones’ foot was a problem. Although a large area of the wound contained hard, black eschar, the blister on the dorsum of his foot was oozing, and there was some softening of the necrotic tissue at the base of the toes.
At the time of his assessment, Mr Jones’ wound was being managed with a silicone non-adherent dressing and a simple dressing pad with orthopaedic wool and a bandage to secure it. However, this was not managing the exudate effectively, as the outer bandage was wet. This inappropriate selection of dressings was contributing to the odour that was associated with Mr Jones’ wound.
Challenges Following Mr Jones’ holistic assessment, the challenge for the tissue viability nurse and the nursing staff was to select a dressing that would address the following issues:
- Odour control;
- Effective debridement of devitalised tissue;
- Exudate management;
- Control of infection;
- Acceptability for the patient.
Bird (1999) recommended that the initial management of a frostbite injury should be based on salvaging damaged tissue, preventing further tissue loss and restoring function. It was decided to use the Kerraboot to treat Mr Jones’ foot. This is a boot-shaped plastic film that covers the foot and leg and has an absorbent pad inside (Fig 2).
Velcro fasteners at the top of the boot ensure that it is held in place. In addition, it has a textured base, and this helps the patient walk around without the risk of slipping.
The Kerraboot was chosen because it provides a warm, moist and protected wound healing environment. This in turn helps to remove devitalised tissue, and promotes the formation of granulation tissue and healing. The absorbent pad is able to absorb excess moisture and contain odour.
Barker et al (2001) found that the Kerraboot dressing was comfortable and convenient to wear which, in turn, reduced pain at dressing change. According to Barker et al (2001) the Kerraboot encourages granulation and keeps superficial infection localised. They also found that the dressing helped to eliminate odour, reduced time for the dressing change and allowed easy visualisation of the wound.
Mr Jones’ Kerraboot was changed every 24 hours until the odour and exudate began to reduce. When the dressing was changed it was completely saturated and there appeared to be condensation inside the plastic boot, which is normal.
After the first week the boot was changed twice weekly. At each dressing change, loose, devitalised tissue was removed by sharp debridement. The blister to the dorsum of the foot was completely deroofed.
Mr Jones found the Kerraboot comfortable to wear and had no problem covering it with his tracksuit trousers. This allowed him to walk around and he was therefore able to carry out an exercise programme with the physiotherapist. Mr Jones found that he had less pain when his dressing was being changed, so it was easy to remove and apply a new one. He also felt that the wound odour was being managed effectively using this treatment.
One month after starting the treatment with the Kerraboot, the tissue on the whole wound was granulating. Understandably, Mr Jones was desperate to go home by now, so outpatient physiotherapy was arranged to prevent flexion deformity and the district nurse agreed to continue the prescribed treatment.
The following month, Mr Jones had granulation tissue on the dorsum of his foot, on his heel and on his great toe. There were still small amounts of necrotic tissue on his second and third toes, but this was separating to reveal granulation tissue underneath. The wound could now be managed with simple dressings, and it continued to improve.
Frostbite is not usually seen in inner city hospitals, but it is becoming more common. As with other thermal injuries, frostbite causes damage to the tissues and, if it is not managed effectively, in extreme cases it can lead to cell death and amputation.
Careful assessment of Mr Jones was crucial to his care. The Kerraboot dressing proved to be the most appropriate management strategy, as it kept his wound moist and allowed granulation tissue to develop. It also controlled the odour that was emanating from the wound and, along with antibiotics, the infection was controlled. The treatment improved Mr Jones’ quality of life, as he was soon able to move around the ward without being in pain.