CONSIDER THIS SCENARIO: On a bitter cold day, it's snowing heavily. The outside temperature is -5.6[degrees] C (22[degrees] F); the wind is blowing at 20 to 25 miles per hour. While a man, age 67, is driving home from the office, his car slides off a rural road into a snow-filled ditch. He's wearing a business suit, trench-style raincoat, and no gloves. After several unsuccessful attempts to dig out his car with ungloved hands, he tries to call a tow truck but can't get a cell phone signal. He decides to walk to a convenience store about 2 miles away. Slipping and falling frequently on the snow-covered road, he reaches the store more than an hour later and pulls the door open with difficulty. With help from the store clerk, he removes his frozen shoes and finds his feet as well as his hands are pale, waxy, and numb. Alarmed, he asks the clerk to call an ambulance. (See Auto safety kit for some items that would have helped in this scenario.)
Cold hard facts
Cold injuries span the gamut from minor to life threatening, and can kill or cause permanent injury. Frostbite is a severe cold-induced injury in which freezing at the tissue level produces minor to major damage. In the severest forms, it leads to gangrene and amputation. Although no comprehensive source provides incidence rates, people at highest risk are those who participate in outdoor recreational events or military operations, work in cold temperatures, are accidentally or unexpectedly caught outside in freezing conditions, or are homeless.1
Knowing how to recognize and intervene to competently treat frostbite is key to the best possible outcomes. This article reviews the pathophysiology of frostbite, prehospital and hospital management of a patient with frostbite, and prevention strategies for personal preparedness and patient education.
Pathophysiology
The primary cause of frostbite is exposure to freezing temperatures. Because the cutaneous circulation plays a primary role in thermoregulation and the subsequent development of frostbite, the most vulnerable areas of the body are those with the most variable blood flow. Although virtually any body part can be affected, the areas most often involved are the hands, feet, nose, and ears.1
Frostbite can develop in areas covered by clothing that offers inadequate protection from environmental conditions or is so tight it impairs circulation. Wearing very snug boots or multiple pairs of socks, for example, can increase the risk of frostbite in the feet. Other well-known contributing factors include wind chill, exposed skin, wetness, peripheral vascular disease or other causes of circulatory impairment, fatigue, substance misuse or abuse, altered consciousness or judgment, inadequate clothing or shelter, dehydration, smoking or nicotine use, immobility, and prior frostbite injury.1
Because adequate cutaneous blood flow is critical to maintaining warmth, any pathophysiologic condition associated with lack of blood flow or vasoconstriction contributes to the development of frostbite. Vasoconstriction begins when skin temperature falls below 15[degrees] C (59[degrees] F); as blood flow continues to decrease, skin temperature also drops accordingly.2 When someone's skin temperature decreases enough that the skin loses normal sensation, the person may not perceive that tissue freezing is starting and may not take appropriate preventive measures to arrest the early stages of frostbite.
After tissue temperature drops far enough for freezing to occur, a cascade of pathophysiologic processes begins. These include extracellular and intracellular ice crystal formation, cellular dehydration and shrinkage, derangement of intracellular electrolyte concentrations, endothelial damage, vasoconstriction, thrombosis, ischemia-reperfusion injury, and ultimately tissue necrosis.1,3 Multiple mediators, including thromboxane A2, arachidonic acid, bradykinin, histamine, and prostaglandins, contribute to the inflammatory response at the tissue level.3
The four overlapping pathologic phases that encompass these effects are commonly identified as the prefreeze, freeze-thaw, vascular stasis, and late ischemic phases of frostbite.3 Ultimately, cold injury severity is based on the degree of tissue damage, which is a measure of how deeply the tissues have been affected by freezing. Severity ranges from mild or superficial to deep involvement of muscle and bone.
The mildest type of cold injury is frostnip, in which cold and vasoconstriction produce ice crystals only on the skin's outermost surface. Because true tissue freezing doesn't occur, frostnip isn't typically included in the spectrum of frostbite injuries. However, frostnip can be a precursor to permanent tissue injury if immediate measures aren't taken to prevent tissue freezing.4 A body part with frostnip is typically numb and appears frosted on the surface or blanched, but the overlying skin itself remains soft and pliable and isn't frozen.2
Frostnip is easily reversed if the affected person finds shelter and applies warmth to the affected area. Warming can be uncomfortable, but after warming, the condition completely resolves. Because frostnip can herald the development of frostbite, early recognition and effective strategies must be employed immediately to prevent more serious tissue injury from continued cold exposure and inadequate protection.
Degrees of damage
The depth of tissue freezing determines the degree of frostbite injury and associated signs and symptoms. Four degrees of frostbite are classically described. The first degree is the least severe and has the best prognosis, and the fourth degree is the most severe and has the worst prognosis. An alternative classification system categorizes first- and second-degree frostbite as superficial, and third- and fourth-degree frostbite as deep.3 Laypersons as well as healthcare personnel working in remote or austere settings may find this simplified classification easier to use for assessment and reporting purposes.
The following descriptions provide an overview of frostbite injury progression. (See Picturing the degrees of frostbite.)
* First-degree frostbite. Tissue freezing is only as deep as the superficial skin layers in first-degree frostbite. First-degree frostbite is characterized by a central area of pallor and anesthesia of the skin surrounded by edema.5 The area will feel firm and may indent with palpation.2 Thawing produces severe pain, erythema, or hyperemia as well as some edema within a few hours. Tissue loss doesn't typically occur after thawing, although sloughing is possible.3 Residual pain, sometimes described as burning, may occur for several weeks.1
* Second-degree frostbite. This cold injury penetrates into deeper layers of skin. The affected skin looks pale, white, waxy, blue-gray, or mottled and feels numb and firm while frozen. It becomes red and edematous upon thawing.2 Clear or milky fluid-filled blisters will develop after rewarming.1,2 Although tissue loss is possible, it's typically minimal.2
* Third-degree frostbite. This severe form of complete tissue freezing extends into the deepest dermal layers. Tissue with third-degree frostbite looks similar to that of second-degree frostbite while frozen. Hyperemia and edema also will occur with thawing, but the blisters associated with third-degree frostbite are easily differentiated because they contain dark, hemorrhagic fluid.1,2 Tissue loss is likely.2
* Fourth-degree frostbite. With the most severe form of frostbite, tissue freezing extends fully into muscle and bone. While frozen, affected body parts may have a classic "chunk of wood" consistency.6
As with burn injuries, various degrees of frostbite can be present in the same body region. After tissues have thawed, the more viable body parts can have erythema, edema, and blisters.1 If the affected areas remain dark and dusky, fail to form blisters, and develop a hard, black eschar, then tissue necrosis, gangrene, or mummification may ultimately result, requiring eventual amputation.1 An accurate prognosis about tissue viability may not be possible for several weeks or months while the freezing injury fully evolves.1
In all degrees of frostbite, pain may be extreme during and after thawing, and it can last days to months depending on the amount of tissue lost.1 Pressure from clothing or shoes as well as activity can worsen the pain; manifestations such as tingling and sensations of electric shock and burning have also been reported.2 Various intensities of sensory loss occur in the affected part for all degrees of frostbite and generally persist from 4 years to indefinitely.1
Because virtually all frostbitten body parts look similar while they're still frozen, the extent of damage can't be reliably determined until the body part thaws and the wounds evolve over time to reveal the line of demarcation between viable and necrotic tissue.1,4 This period can extend from 45 days to 3 months after the cold injury.1,3
Initial care
The basic principles of frostbite management are the same whether the patient is outdoors or in the hospital. Addressing hypothermia is the first priority, followed by evacuation to definitive care in a hospital that can provide the advanced monitoring, diagnostic studies, and interventions needed.
An interdisciplinary team approach is essential. Telemedicine, including virtual Internet-based consultation, is being used in many areas to obtain expert assistance with patient management.
When providing initial care outdoors, secure shelter for the patient as soon as possible to minimize further exposure to the elements. Reduce heat loss by immediately helping the person remove any wet clothing and change into dry, warm clothes. A warm sleeping bag or blankets can be used to more effectively insulate the person from the cold.
Assess the patient for evidence of hypothermia, illness, and injury. Management of moderate-to-severe hypothermia takes priority over management of frostbite. Frostbite should be treated only after the person's core body temperature is greater than 35[degrees] C (95[degrees] F).2
When assessing body areas for possible frostbite, inspect and palpate the skin. Observe for a yellow to white waxy or blue-gray mottled appearance and firm, numb skin. If the patient consents, taking a digital photograph of the affected areas can help to establish a baseline for trending after rewarming occurs and as the cold injury evolves. Because edema develops after thawing occurs, remove all jewelry and clothing from the frostbitten body parts before initiating rewarming efforts.2 Strongly advise the patient against smoking and drinking alcohol. Smoking promotes vasoconstriction, which further decreases tissue perfusion; alcohol increases heat loss by inducing vasodilation and can also impair judgment.1
If the patient's level of consciousness is normal, offer warm fluids to drink: Adequate hydration is an essential strategy in both the prevention and treatment of cold injuries. Supplemental oxygen, if available, is also recommended, especially if the patient is hypoxic or at high altitude.3
The definitive treatment for frostbite is rapid rewarming in a water bath, but a frostbitten area that's been thawed and then freezes again is at risk for a much poorer outcome during the healing process.2,6 If the patient faces a risk for refreezing, then the frostbitten body part shouldn't be actively rewarmed.2,3,6 Whether to employ rapid rewarming of the body part depends on the patient's risk for refreezing due to delays in evacuation from a cold environment.
Some prolonged rescues or evacuations from austere or wilderness settings require the person with frostbite to participate in a self-rescue such as by walking out. In that type of situation, don't try to keep the part from thawing because tissue destruction is related to the depth and amount of time the area has been frozen.3 Instead, pad or splint the affected area to protect it from further harm and allow the tissue to thaw slowly and spontaneously.3
Never rub a frostbitten body part with snow or massage the area because doing so will cause more tissue injury.2,6 Likewise, don't attempt to rewarm body parts using fire or external sources of dry heat.2,6 The evidence-based approach is to immerse and gently swirl the frostbitten body part in a warm water bath at a temperatures of 37[degrees] C (98.6[degrees] F) to 39[degrees] C (102.2[degrees] F) for at least 30 minutes, adding more warm water when needed to maintain the optimal temperature range, until the skin shows a blush and becomes soft and pliable.2,3,7 Although warming with water temperatures below 37[degrees] C (98.6[degrees] F) may cause less pain, more rapid rewarming with water in the recommended range results in better outcomes for tissue survival.1 Previously, warmer water (40[degrees] C to 42.2[degrees] C [104[degrees] F to 108[degrees] F]) was recommended for rapid rewarming, but lower temperatures may be associated with less pain and a lower risk of inadvertent burns.1,2
Ideally, a thermometer should be used to measure the water temperature during the duration of the rewarming bath to ensure the desired temperature range is maintained. If a thermometer isn't available, use water that's the temperature of a hot tub; to test it, you as the nurse should be able to hold your hand in it for at least 30 seconds without feeling uncomfortable before immersing the patient's body part.3 If hot water must be added to maintain the target temperature, remove the patient's body part from the water until the water temperature is retested to ensure it isn't too hot before reimmersion.2 Prevent the patient's injured extremity from resting on the bottom or touching the sides of the water bath vessel to avoid inadvertent tissue trauma from pressure while the extremity is numb.2,8
Frostbite of the ears and nose can be managed by continually applying warm, moist compresses to the affected areas until thawing occurs.9
Rewarming a frostbitten body part is extremely painful. If possible, an ibuprofen regimen should be initiated in the field setting. Besides providing a measure of pain relief, ibuprofen may support tissue viability by decreasing the production of thromboxane and other inflammatory mediators.3 Aspirin may also provide beneficial antiprostaglandin and analgesic effects for patients with frostbite.7,10 Severe pain is most effectively treated with parenteral opioid analgesics.
With adequate thawing, expect the skin to become pliable and soft as well as to change color from pale or white to red or purple.3 The return of intact sensation as well as pain and erythema after rewarming are encouraging findings that carry a better prognosis for tissue recovery; conversely, unfavorable outcomes are associated with areas that remain pale, cold, and numb.1
After the body part has been thawed in the water bath, don't dry it by rubbing the skin because this action can cause more tissue trauma; instead, permit the affected part to air dry. Applying aloe vera cream or gel inhibits thromboxane and may promote wound healing.1,3,9
Expect significant edema to develop after frostbitten areas have been thawed. Bandage the area with a loose, sterile dressing and place padding between affected digits. Elevate affected body parts to reduce edema. When frostbitten areas have been thawed in the field or prehospital setting, don't let the patient bear weight or otherwise use the involved body part to minimize the chance of further injury.2 Monitor for the development of compartment syndrome in rewarmed extremities and anticipate the need for urgent surgical evaluation and fasciotomy if compartment pressures are elevated.1 (See Signs and symptoms of acute compartment syndrome.) Tetanus prophylaxis is warranted because tetanus is a reported complication of frostbite.5
Blister debridement isn't typically performed or recommended in the prehospital setting unless it appears the blister will rupture.2 Clear fluid may be drained, but blisters with hemorrhagic fluid should be protected with padding and kept intact until they can be managed definitively in the hospital setting.3 Prompt initiation of parenteral antibiotics is indicated for evidence of infection.5
Ongoing care
In the postrewarming phase of care, diagnostic imaging and advanced interventions in the hospital setting are employed to both evaluate and treat the tissue damage associated with frostbite. Depending on the patient's clinical status, treatment options include hyperbaric oxygen therapy, hydrotherapy, sympathectomy, fasciotomy, and amputation.1
Evaluating for the presence of microvascular thrombosis in the early stages of care can help to determine possible reperfusion strategies. Imaging performed days to months later as the frostbite injury evolves can help to differentiate viable from nonviable tissue when planning surgical procedures such as debridement and amputation. The most helpful diagnostic studies for this include arteriography, technetium-99m scintigraphy (bone scan), and magnetic resonance imaging.3,7,11
I.V. or intra-arterial fibrinolytic agents may be administered to treat the microvascular thrombus associated with frostbite if the patient has no contraindications to anticoagulation. Fibrinolytic agents are best given within 24 hours of rewarming in facilities with intensive care capabilities.3
Gonzaga and colleagues reported the results of their 14-year experience with 69 patients with frostbite. They used angiography to identify perfusion deficits with subsequent catheter-directed infusion of intra-arterial fibrinolytic agents in 66 patients found to have arterial thrombosis.11 Outcome data from 62 patients included in the analysis revealed a complete digit salvage rate of 68.6%. They concluded that this treatment modality reduces the incidence of late amputations.
Another promising treatment option is the administration of vasodilators, particularly prostaglandins. For example, use of I.V. iloprost, a prostacyclin analog, demonstrated significant efficacy in long-term tissue salvage when administered for severe frostbite in a European study when compared with other methods. It's now being touted in frostbite literature as a potential new therapy.1,12,13 At the time of this writing, however, I.V. iloprost hasn't been approved by the FDA for this indication.
Nursing implications
Besides being able to provide expert clinical management immediately after this cold injury, nurses need to understand the long-term complications and how these effects impact the patient's life. The aftermath of frostbite reflects the severity of the original injury and may include changes in skin color and nail structure, hyperhidrosis, stiffness, sensory loss, pain, and neuropathy.1 Patients may need to be referred for psychosocial support or counseling as well as rehabilitation and pain management.
Perhaps the most important strategy for addressing frostbite is effective education, including hypothermia prevention. Nurses can play a fundamental role in teaching both patients and members of the general community how to stay safe in the cold. (See Tips for preventing frostbite.)
Wrapping up
The scenario described in the beginning of this article is one example of the risk inherent in cold weather. Although the circumstances may differ, frostbite threatens people living, working, or traveling in cold climates. Understanding factors that predispose people to cold injuries is essential to mitigate these risks.
As with most injuries, the critical decisions made in the initial assessment and management phases are intrinsically linked to patient outcomes.
Although the scenario involving the traveler at the beginning of this article is fictional, it's representative of very real circumstances that are common in winter environments and are associated with the development of cold injury in people at risk. In the best possible case, this traveler's treatment in the local ED would include removal of his wet clothing; the application of warm, dry blankets around his body; and immersion of his feet and hands in water baths at temperatures of 37[degrees] C to 39[degrees] C (98.6[degrees] F to 102.2[degrees] F) for at least 30 minutes. In addition, he'd be given a dose of ibuprofen by mouth, immunized against tetanus if not he's not up to date, and offered an I.V. opioid agent for pain management during the rewarming phase. Taking into account his relatively short period of cold exposure and rapid access to expert, definitive care, this patient would be expected to ultimately have a good outcome. His frostbite would likely turn out to be superficial (first or second degree). However, if he didn't make it into the convenience store until much later or not at all, the ending to this story could be a more tragic one.
Auto safety kit
All-season:
* Nonperishable ready-to-eat food or snacks such as energy bars
* Water
* Extra medications
* First-aid kit
* Fire extinguisher
* Road flares or other signaling device
* Flashlight and extra batteries
* Cell phone charger or extra battery pack
* Waterproof matches
* Pocket knife or multifunction tool
* Portable battery-powered or hand-crank radio
* Brightly colored surveyor's tape or fluorescent flag for signaling
* Booster cables
* Spare tire with jack
* Tow rope or strap.
Add for winter driving:*
* Snow shovel
* Bag of sand or cat litter for traction
* Sleeping bag(s) or blanket(s)
* Extra winter gloves, hats, and socks
* Insulated work gloves
* Windshield scraper and brush
* Metal coffee cans with long-burning candles.
*Note: Always travel with more than half a tank of gasoline in the wintertime.
Signs and symptoms of acute compartment syndrome15
The following signs and symptoms are indicative of acute compartment syndrome:
* Pain (severe, on passive motion, pressure, or stretch)
* Pallor
* Pulselessness
* Paresthesia
* Poikilothermia (skin that takes on the temperature of the environment)
* Palpation reveals a tight muscle compartment.
Tips for preventing frostbite
* Pay attention to weather forecasts. Protect exposed skin from contact with below-freezing temperatures, especially in windy conditions. Wind and moisture hasten the onset of frostbite. Covering the face, ears, hands, and feet and other exposed areas is critical. Wearing layered, properly fitting clothing that's windproof and waterproof to minimize wind chill is the best way to stay warm and dry.14
* Learn the factors that increase frostbite risk and know individual susceptibilities, such as peripheral arterial disease, alcohol abuse, nicotine use, fatigue, dehydration, medications such as beta-blockers and sedatives, or previous cold injury.4
* Ensure proper nutrition and stay hydrated. Eat and dress to maintain adequate core body temperature.
* Avoid smoking and consuming alcohol. Although alcohol may initially produce vasodilation in the extremities and provide a subjective sensation of warmth, it will increase heat loss and can lead to poor decision-making.
* In below-freezing temperatures, avoid touching metal with bare hands. Also avoid contact with liquids such as gasoline or alcohol that remain in a liquid state at subfreezing temperatures.
* If hands and feet begin to get cold, exercise can help promote peripheral circulation. Consider using electric or chemical warmers or "hot packs" to increase warmth. Don't wear multiple layers of socks or tight boots as these may impair circulation and increase the risk of frostbite.
* In a group outing, check each other periodically for early signs of frostnip so that actions can be taken to avoid the progression to frostbite. In the event of extreme conditions, seek shelter as soon as possible.
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