| Non-freezing cold injury | |
|---|---|
| Other names | NFCI |
| Usual onset | following exposure |
| Duration | indefinite |
| Causes | prolonged exposure to low temperatures above freezing |
| Risk factors | occupational, social |
| Diagnostic method | based on symptoms and history of exposure |
| Differential diagnosis | Decompression sickness, hand-arm vibration syndrome |
| Prevention | personal protective clothing |
| Treatment | rewarming |
| Medication | analgesic |
| Prognosis | variable |
Non-freezing cold injuries (NFCI) is a class of tissue damage caused by sustained exposure to low temperature without actual freezing. [1] There are several forms of NFCI, and the common names may refer to the circumstances in which they commonly occur or were first described, such as trench foot, which was named after its association with trench warfare. NFCI is caused by microvascular endothelial damage, stasis and vascular occlusion and is characterised by peripheral neuropathy. [2] [3] NFCI generally affects the hands or feet during exposure to temperatures just above freezing, often wet, and is typically found in soldiers. [2]
Development may be gradual, and it may be difficult to recognise and treat. [4] Initially the affected area is cold and numb, but this changes to hyperemia (changes to blood flow) within a day or two, along with an intense, painful, burning sensation, blisters, redness, and in some cases ulceration. It may have lifelong effects, including numbness, paraesthesia, and chronic pain, the etiology of which is not yet adequately demonstrated. Hypersensitivity to cold may also occur. [2] [1]
Strategies to reduce the impact of the condition focus on recognition of those at risk, limiting exposure, and use of suitable personal protective equipment. [5]
Symptoms may be similar to those of decompression sickness and hand-arm vibration syndrome, and NFCI may occur in conditions where these are possible or likely – diving in cold water, and logging and construction work in cold environments.
Non-freezing cold injury is a form of cold injury in which there is no freeze–thaw damage. Cold injury may be divided into local and systemic cold injury. Systemic cold injury is generally known as hypothermia. Local cold injury can be divided into freezing and non-freezing cold injury. Freezing cold injury (FCI) is generally known as frostbite. [6]
Types of NFCI:
Four distinct stages occur:
Short-term complications can include infection of the affected area and gangrene. Walking in the first few days of recovery may be affected by poor coordination of the affected limb and have a springless gait. Longer term complications may include chronic pain and temperature sensitivity. [5]
NFCI is caused by microvascular endothelial damage, stasis and vascular occlusion, and generally affects the hands or feet during exposure to temperatures just above freezing, often wet. [2]
Risk factors include exposure of the extremities to cold 0 to 15 °C (32 to 59 °F) and wet for prolonged periods, usually two to three days or longer, but the duration is relative to the temperature, and cases have been reported after immersion in cold sea water 0 to 8 °C (32 to 46 °F) after considerably shorter exposures, and higher temperatures (up to 21 °C (70 °F) for longer periods (order of 8 days). NFCI correlates with exposure to cold environment with fatigue, malnutrition, and immobility or restricted movement, poor environmental protection, inadequate fluid or caloric intake, fatigue, and stress, often while wearing constricting shoes or boots continuously for many days. [5] Pre-existing conditions that may increase susceptibility include circulatory problems, including peripheral vascular disease or Raynaud phenomenon, and diabetes. Smoking, older age, and ethnicity may have effects, but data are inconclusive. Mental illness and alcohol use may also be risk factors. [5]
The skin has an important thermoregulatory function, controlled by variation of blood flow, which can be reduced to about 10% of baseline without ischaemia, as the metabolic requirements of skin are low. Maximum skin vasoconstriction occurs in the extremities when cooled to around 15 °C (59 °F), with further cooling causing an increased perfusion due to the "hunting response", or cold-induced vasodilation, which occurs in 5 to 10 minute cycles, which may adapt in strength and cycling rate with repeated exposures. A strong response is thought to improve resistance to NFCI, but evidence is not conclusive. [5]
The mechanism of NFCI is poorly understood. Reduced control of circulation and damage to the microcirculation are characteristic. Although some authorities consider the cause to be only prolonged vasoconstriction, others think it likely to be more complex. There is evidence suggesting that extent and severity of tissue damage is due to a combination of temperature and duration, and that repeated exposures may cause more damage than a single longer exposure. Damage to nerves and to the microvascular blood supply of nerves may be reversible or irreversible. The duration of a single exposure at a given temperature that is likely to cause NFCI is not known, and the quantitative effects of multiple exposures are similarly unclear. The presence of a wet environment appears to be important, and immobility and malnutrition appear to be contributory. [5] Experimental evidence suggests a complex mode of injury with microvascular disruption, cyclic ischaemia, reperfusion injury and direct damage to nerves due to cold. [3] [9] Large, myelinated nerve fibres appear to be more susceptible. [3]
Tissue loss may occur in severe cases, but is thought to be caused by pressure injury, with or without compartment syndrome, and mechanical injury, and not by the cold. [5]
It can be difficult to distinguish FCI from NFCI and to assess the degree of injury during initial examination, as both types of local cold injury can occur on the same limb, and deep tissue damage may take weeks to manifest. [6] Frostbite can be ruled out if there was no exposure to temperatures several degrees below freezing. [5]
NFCI can occur in situations where decompression sickness is possible in underwater diving in cold water, [7] [3] and in situations where hand-arm vibration syndrome is possible in outdoor work with machinery such as chainsaws and jackhammers in cold climates, which can complicate differential diagnosis.
In underwater diving diagnosis is complicated by a significant overlap of symptoms between decompression sickness and NFCI. The symptoms of decompression sickness with a peripheral neuropathy (such as pain and numbness) may be similar to NFCI. [3] Both conditions are caused by environmental exposure, and there are no high sensitivity and specificity diagnostic tests for either condition. Diagnosis may rely on dive history, particularly water temperature, though the quality of insulation and fit of the suit will have an influence on perfusion and heat loss. [3] Definitive treatment for DCS is hyperbaric oxygen therapy, [10] which is expensive, but unlikely to aggravate NFCI, and first aid provision of 100% oxygen for suspected DCS is relatively inexpensive, often available and will do no harm, whereas over-warming of a case of DCS may cause bubble growth and aggravate the condition.
Strategies to reduce the impact of the condition focus on recognition of those at risk, limiting exposure, and use of suitable personal protective equipment. [5]
First aid treatment is similar to first aid for frostbite. [11]
Treatment should prioritise systemic cold injury, as it may be immediately life-threatening, then freezing cold injury, followed by non-freezing cold injury where combinations occur. [6]
In cases of isolated NFCI the extremities should be allowed to rewarm gradually with rest and elevation of the affected limbs. Rapid rewarming will increase pain and edema. Air drying is preferred. [5]
Persistent symptoms including increased sensitivity to cold can continue long after the original injury, and may have long term psychological and financial effects, and are the basis of a significant number of military legal claims. [12]
NFCI is known as a cause of significant morbidity in military personnel and civilians who work in cold conditions, [4] mountaineers, fishermen, homeless people, [1] and occasionally, underwater divers.
Cold injuries have long been recognised as a military problem. Early descriptions were recorded by Napoleon's chief surgeon, Dominique Jean Larrey. Trench foot was a major problem in World War I, and millions of man–days were lost in World War II to cold injury. Both Argentinian and British troops reported cold injuries in the Falklands campaign. In civilians, those affected include homeless people and the urban poor, wilderness enthusiasts and mountaineers, and people taking part in winter sports. It is often also associated with psychiatric illness and drug and alcohol abuse, [8] and occasionally with underwater diving. [3]
Other cold-related conditions:
Decompression sickness is a medical condition caused by dissolved gases emerging from solution as bubbles inside the body tissues during decompression. DCS most commonly occurs during or soon after a decompression ascent from underwater diving, but can also result from other causes of depressurisation, such as emerging from a caisson, decompression from saturation, flying in an unpressurised aircraft at high altitude, and extravehicular activity from spacecraft. DCS and arterial gas embolism are collectively referred to as decompression illness.
Hypothermia is defined as a body core temperature below 35.0 °C (95.0 °F) in humans. Symptoms depend on the temperature. In mild hypothermia, there is shivering and mental confusion. In moderate hypothermia, shivering stops and confusion increases. In severe hypothermia, there may be hallucinations and paradoxical undressing, in which a person removes their clothing, as well as an increased risk of the heart stopping.
Frostbite is a skin injury that occurs when someone is exposed to extremely low temperatures, causing the freezing of the skin or other tissues, commonly affecting the fingers, toes, nose, ears, cheeks and chin areas. Most often, frostbite occurs in the hands and feet. The initial symptoms are typically a feeling of cold and tingling or numbing. This may be followed by clumsiness with a white or bluish color to the skin. Swelling or blistering may occur following treatment. Complications may include hypothermia or compartment syndrome.
Paresthesia is an abnormal sensation of the skin with no apparent physical cause. Paresthesia may be transient or chronic, and may have many possible underlying causes. Paresthesias are usually painless and can occur anywhere on the body, but most commonly occur in the arms and legs.
Barotrauma is physical damage to body tissues caused by a difference in pressure between a gas space inside, or in contact with, the body and the surrounding gas or liquid. The initial damage is usually due to over-stretching the tissues in tension or shear, either directly by an expansion of the gas in the closed space or by pressure difference hydrostatically transmitted through the tissue. Tissue rupture may be complicated by the introduction of gas into the local tissue or circulation through the initial trauma site, which can cause blockage of circulation at distant sites or interfere with the normal function of an organ by its presence. The term is usually applied when the gas volume involved already exists prior to decompression. Barotrauma can occur during both compression and decompression events.
Decompression Illness (DCI) comprises two different conditions caused by rapid decompression of the body. These conditions present similar symptoms and require the same initial first aid. Scuba divers are trained to ascend slowly from depth to avoid DCI. Although the incidence is relatively rare, the consequences can be serious and potentially fatal, especially if untreated.
Ischemia or ischaemia is a restriction in blood supply to any tissue, muscle group, or organ of the body, causing a shortage of oxygen that is needed for cellular metabolism. Ischemia is generally caused by problems with blood vessels, with resultant damage to or dysfunction of tissue i.e. hypoxia and microvascular dysfunction. It also implies local hypoxia in a part of a body resulting from constriction.
Diabetic neuropathy includes various types of nerve damage associated with diabetes mellitus. The most common form, diabetic peripheral neuropathy, affects 30% of all diabetic patients. Symptoms depend on the site of nerve damage and can include motor changes such as weakness; sensory symptoms such as numbness, tingling, or pain; or autonomic changes such as urinary symptoms. These changes are thought to result from a microvascular injury involving small blood vessels that supply nerves. Relatively common conditions which may be associated with diabetic neuropathy include distal symmetric polyneuropathy; third, fourth, or sixth cranial nerve palsy; mononeuropathy; mononeuropathy multiplex; diabetic amyotrophy; and autonomic neuropathy.
Diving disorders, or diving related medical conditions, are conditions associated with underwater diving, and include both conditions unique to underwater diving, and those that also occur during other activities. This second group further divides conditions caused by exposure to ambient pressures significantly different from surface atmospheric pressure, and a range of conditions caused by general environment and equipment associated with diving activities.
Nerve block or regional nerve blockade is any deliberate interruption of signals traveling along a nerve, often for the purpose of pain relief. Local anesthetic nerve block is a short-term block, usually lasting hours or days, involving the injection of an anesthetic, a corticosteroid, and other agents onto or near a nerve. Neurolytic block, the deliberate temporary degeneration of nerve fibers through the application of chemicals, heat, or freezing, produces a block that may persist for weeks, months, or indefinitely. Neurectomy, the cutting through or removal of a nerve or a section of a nerve, usually produces a permanent block. Because neurectomy of a sensory nerve is often followed, months later, by the emergence of new, more intense pain, sensory nerve neurectomy is rarely performed.
Ebullism is the formation of water vapour bubbles in bodily fluids due to reduced environmental pressure, usually at extreme high altitude. It occurs because a system of liquid and gas at equilibrium will see a net conversion of liquid to gas as pressure lowers; for example, liquids reach their boiling points at lower temperatures when the pressure on them is lowered. The injuries and disorder caused by ebullism is also known as ebullism syndrome. Ebullism will expand the volume of the tissues, but the vapour pressure of water at temperatures in which a human can survive is not sufficient to rupture skin or most other tissues encased in skin. Ebullism produces predictable injuries, which may be survivable if treated soon enough, and is often accompanied by complications caused by rapid decompression, such as decompression sickness and a variety of barotrauma injuries. Persons at risk are astronauts and high altitude aviators, for whom it is an occupational hazard.
Hypoesthesia or numbness is a common side effect of various medical conditions that manifests as a reduced sense of touch or sensation, or a partial loss of sensitivity to sensory stimuli. In everyday speech this is generally referred to as numbness.
Trench foot, also known by other names, is a type of foot damage due to moisture. Initial symptoms often include tingling or itching which can progress to numbness. The feet may become red or bluish in color. As the condition worsens the feet can start to swell and smell of decay. Complications may include skin breakdown or infection.
Cold injury is damage to the body from cold exposure, including hypothermia and several skin injuries. Cold-related skin injuries are categorized into freezing and nonfreezing cold injuries. Freezing cold injuries involve tissue damage when exposed to temperatures below freezing. Nonfreezing cold injuries involve tissue damage when exposed to temperatures often between 0-15 degrees Celsius for extended periods of time. While these injuries have disproportionally affected military members, recreational winter activities have also increased the risk and incidence within civilian populations. Additional risk factors include homelessness, inadequate or wet clothing, alcohol abuse or tobacco abuse, and pre-existing medical conditions that impair blood flow.
An aerosol frostbite of the skin is an injury to the body caused by the pressurized gas within an aerosol spray cooling quickly, with the sudden drop in temperature sufficient to cause frostbite to the applied area. Medical studies have noted an increase of this practice, known as "frosting", in pediatric and teenage patients.
Decompression theory is the study and modelling of the transfer of the inert gas component of breathing gases from the gas in the lungs to the tissues and back during exposure to variations in ambient pressure. In the case of underwater diving and compressed air work, this mostly involves ambient pressures greater than the local surface pressure, but astronauts, high altitude mountaineers, and travellers in aircraft which are not pressurised to sea level pressure, are generally exposed to ambient pressures less than standard sea level atmospheric pressure. In all cases, the symptoms caused by decompression occur during or within a relatively short period of hours, or occasionally days, after a significant pressure reduction.
Cryoneurolysis, also referred to as cryoanalgesia, is a medical procedure that temporarily blocks nerve conduction along peripheral nerve pathways. The procedure, which inserts a small probe to freeze the target nerve, can facilitate complete regeneration of the structure and function of the affected nerve. Cryoneurolysis has been used to treat a variety of painful conditions.
The physiology of decompression is the aspect of physiology which is affected by exposure to large changes in ambient pressure. It involves a complex interaction of gas solubility, partial pressures and concentration gradients, diffusion, bulk transport and bubble mechanics in living tissues. Gas is breathed at ambient pressure, and some of this gas dissolves into the blood and other fluids. Inert gas continues to be taken up until the gas dissolved in the tissues is in a state of equilibrium with the gas in the lungs, or the ambient pressure is reduced until the inert gases dissolved in the tissues are at a higher concentration than the equilibrium state, and start diffusing out again.
Inner ear decompression sickness, (IEDCS) or audiovestibular decompression sickness is a medical condition of the inner ear caused by the formation of gas bubbles in the tissues or blood vessels of the inner ear. Generally referred to as a form of decompression sickness, it can also occur at constant pressure due to inert gas counterdiffusion effects.
Thermal balance of a diver occurs when the total heat exchanged between the diver and their surroundings results in a stable temperature of the diver. Ideally this is within the range of normal human body temperature. Thermal status of the diver is the temperature distribution and heat balance of the diver. The terms are frequently used as synonyms. Thermoregulation is the process by which an organism keeps its body temperature within specific bounds, even when the surrounding temperature is significantly different. The internal thermoregulation process is one aspect of homeostasis: a state of dynamic stability in an organism's internal conditions, maintained far from thermal equilibrium with its environment. If the body is unable to maintain a normal human body temperature and it increases significantly above normal, a condition known as hyperthermia occurs. The opposite condition, when body temperature decreases below normal levels, is known as hypothermia. It occurs when the body loses heat faster than producing it. The core temperature of the body normally remains steady at around 36.5–37.5 °C (97.7–99.5 °F). Only a small amount of hypothermia or hyperthermia can be tolerated before the condition becomes debilitating, further deviation can be fatal. Hypothermia does not easily occur in a diver with reasonable passive thermal insulation over a moderate exposure period, even in very cold water.
Consequences of external causes | |||||
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| Temperature |
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| Radiation |
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| Oxygen | |||||
| Pressure | |||||
| Food | |||||
| Maltreatment | |||||
| Travel | |||||
| Adverse effect | |||||
| Other | |||||
| Ungrouped skin conditions resulting from physical factors |
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