Environmental Emergencies
Question 144 of 180
A 34 year old man is brought to the Emergency Department after becoming lost on a mountain. He spent 3 days without shelter prior to being rescued. On examination he has frostbite to both hands. Which of the following statements regarding management of frostbite is FALSE?
Answer:
Excessive dry heat can cause a burn injury, as the limb is usually insensate. Do not rub or massage the area.Cold Injuries and Frostbite
Environmental Emergencies
Last Updated: 12th February 2021
The severity of cold injury depends on temperature, duration of exposure, environmental conditions, amount of protective clothing, and the patient’s general state of health. Lower temperatures, immobilisation, prolonged exposure, moisture, the presence of peripheral vascular disease, and open wounds all increase the severity of the injury.
Types of cold injury
Two types of cold injury are seen in trauma patients: frostbite and non-freezing injury.
Frostbite
- Damage from frostbite can be due to freezing of tissue, ice crystal formation causing cell membrane injury, microvascular occlusion, and subsequent tissue anoxia. Some of the tissue damage also can result from reperfusion injury that occurs on rewarming.
- Frostbite is classified into first-degree, second-degree, third-degree, and fourth-degree according to depth of involvement:
- First-degree frostbite: Hyperaemia and oedema are present without skin necrosis.
- Second-degree frostbite: Large, clear vesicle formation accompanies the hyperaemia and oedema with partial-thickness skin necrosis.
- Third-degree frostbite: Full-thickness and subcutaneous tissue necrosis occurs, commonly with haemorrhagic vesicle formation.
- Fourth-degree frostbite: Full-thickness skin necrosis occurs, including muscle and bone with later necrosis.
- Although the affected body part is typically hard, cold, white, and numb initially, the appearance of the lesion changes during the course of treatment as the area warms up and becomes perfused. The initial treatment regimen applies to all degrees of insult, and the initial classification is often not prognostically accurate. The final surgical management of frostbite depends on the level of demarcation of the perfused tissue. This demarcation may take from weeks to months to reach a final stage.
Non-freezing injury
- Non-freezing injury is due to microvascular endothelial damage, stasis, and vascular occlusion.
- Trench foot or cold immersion foot (or hand) describes a non-freezing injury of the hands or feet—typically in soldiers, sailors, fishermen, and the homeless—resulting from long-term exposure to wet conditions and temperatures just above freezing (1.6°C to 10°C). Although the entire foot can appear black, deep tissue destruction may not be present.
- Alternating arterial vasospasm and vasodilation occur, with the affected tissue first cold and numb, and then progress to hyperaemia in 24 to 48 hours. With hyperaemia comes intense, painful burning and dysaesthesia, as well as tissue damage characterised by oedema, blistering,
redness, ecchymosis, and ulcerations. - Complications of local infection, cellulitis, lymphangitis, and gangrene can occur. Proper attention to foot hygiene can prevent the occurrence of most such complications.
Management of frostbite and non-freezing cold injuries
- General management
- Treatment should begin immediately to decrease the duration of tissue freezing. Do not attempt rewarming if there is a risk of refreezing.
- Replace constricting, damp clothing with warm blankets, and give the patient hot fluids by mouth, if he or she is able to drink.
- Place the injured part in circulating water at a constant 40°C until pink color and perfusion return (usually within 20 to 30 minutes). This treatment is best accomplished in an inpatient setting in a large tank, or by placing the injured limb into a bucket with warm water running in.
- Excessive dry heat can cause a burn injury, as the limb is usually insensate. Do not rub or massage the area.
- Rewarming can be extremely painful, and adequate analgesics (intravenous opioids) are essential.
- Warming of large areas can result in reperfusion syndrome, with acidosis, hyperkalaemia, and local swelling; therefore, monitor the patient’s cardiac status and peripheral perfusion during rewarming.
- Local wound care
- The goal of wound care for frostbite is to preserve damaged tissue by preventing infection, avoiding opening uninfected vesicles, and elevating the injured area.
- Protect the affected tissue by a tent or cradle, and avoid pressure to the injured tissue.
- Only rarely is fluid loss massive enough to require resuscitation with intravenous fluids, although patients may be dehydrated.
- Tetanus prophylaxis depends on the patient’s tetanus immunisation status.
- Systemic antibiotics are not indicated prophylactically, but are reserved for identified infections.
- Keep the wounds clean, and leave uninfected non-haemorrhagic blisters intact for 7 to 10 days to provide a sterile biologic dressing to protect underlying epithelialisation.
- Tobacco, nicotine, and other vasoconstrictive agents must be withheld.
- Instruct the patient to minimise weight bearing until oedema is resolved.
- Numerous adjuvants have been attempted in an effort to restore blood supply to cold-injured tissue. Unfortunately, most are ineffective. Sympathetic blockade (e.g. sympathectomy or drugs) and vasodilating agents have generally not proven helpful in altering the progression of acute cold injury. Heparin and hyperbaric oxygen also have failed to demonstrate substantial treatment benefit. Retrospective case series have suggested that thrombolytic agents may show some promise, but only when thrombolytic therapy was administered within 23 hours of the frostbite injury.
- Occasionally patients arrive at the ED several days after suffering frostbite, presenting with black, clearly dead toes, fingers, hands, or feet. In this circumstance, rewarming of the tissue is not necessary.
- With all cold injuries, estimations of depth of injury and extent of tissue damage are not usually accurate until demarcation is evident. This often requires several weeks or months of observation.
- Dress these wounds regularly with a local topical antiseptic to help prevent bacterial colonisation, and debride them once demarcation between live and dead tissue has developed. Early surgical debridement or amputation is seldom necessary, unless infection occurs.
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- Biochemistry
- Blood Gases
- Haematology
| Biochemistry | Normal Value |
|---|---|
| Sodium | 135 – 145 mmol/l |
| Potassium | 3.0 – 4.5 mmol/l |
| Urea | 2.5 – 7.5 mmol/l |
| Glucose | 3.5 – 5.0 mmol/l |
| Creatinine | 35 – 135 μmol/l |
| Alanine Aminotransferase (ALT) | 5 – 35 U/l |
| Gamma-glutamyl Transferase (GGT) | < 65 U/l |
| Alkaline Phosphatase (ALP) | 30 – 135 U/l |
| Aspartate Aminotransferase (AST) | < 40 U/l |
| Total Protein | 60 – 80 g/l |
| Albumin | 35 – 50 g/l |
| Globulin | 2.4 – 3.5 g/dl |
| Amylase | < 70 U/l |
| Total Bilirubin | 3 – 17 μmol/l |
| Calcium | 2.1 – 2.5 mmol/l |
| Chloride | 95 – 105 mmol/l |
| Phosphate | 0.8 – 1.4 mmol/l |
| Haematology | Normal Value |
|---|---|
| Haemoglobin | 11.5 – 16.6 g/dl |
| White Blood Cells | 4.0 – 11.0 x 109/l |
| Platelets | 150 – 450 x 109/l |
| MCV | 80 – 96 fl |
| MCHC | 32 – 36 g/dl |
| Neutrophils | 2.0 – 7.5 x 109/l |
| Lymphocytes | 1.5 – 4.0 x 109/l |
| Monocytes | 0.3 – 1.0 x 109/l |
| Eosinophils | 0.1 – 0.5 x 109/l |
| Basophils | < 0.2 x 109/l |
| Reticulocytes | < 2% |
| Haematocrit | 0.35 – 0.49 |
| Red Cell Distribution Width | 11 – 15% |
| Blood Gases | Normal Value |
|---|---|
| pH | 7.35 – 7.45 |
| pO2 | 11 – 14 kPa |
| pCO2 | 4.5 – 6.0 kPa |
| Base Excess | -2 – +2 mmol/l |
| Bicarbonate | 24 – 30 mmol/l |
| Lactate | < 2 mmol/l |
