Frostbite

Overview

Definition

Frostbite is injury to tissue resulting from cold exposure at temperatures below 0°C (32°F). Frostbite exists on the severe end of a spectrum, with frostnip and pernio at the milder end.

Epidemiology

• Poor population statistics (no formal reporting) 
• Vulnerable populations:
  • Homeless
  • Military personnel
  • Children
  • Elderly
• Risk factors:
  • Low ambient temperature
  • High-velocity wind
  • Exposure to water or snow
  • Clothing that is wet, constrictive, or inadequately insulating
  • Impaired judgment Judgment The process of discovering or asserting an objective or intrinsic relation between two objects or concepts; a faculty or power that enables a person to make judgments; the process of bringing to light and asserting the implicit meaning of a concept; a critical evaluation of a person or situation. Psychiatric Assessment (ethyl alcohol, drugs, fear/panic)
  • History of peripheral vascular disease or Raynaud’s phenomenon 
• Commonly affected areas: poorly vascularized periphery
  • Fingers 
  • Toes 
  • Nose Nose The nose is the human body’s primary organ of smell and functions as part of the upper respiratory system. The nose may be best known for inhaling oxygen and exhaling carbon dioxide, but it also contributes to other important functions, such as tasting. The anatomy of the nose can be divided into the external nose and the nasal cavity. Nose and Nasal Cavity: Anatomy 
  • Ears 
  • Penis Penis The penis is the male organ of copulation and micturition. The organ is composed of a root, body, and glans. The root is attached to the pubic bone by the crura penis. The body consists of the 2 parallel corpora cavernosa and the corpus spongiosum. The glans is ensheathed by the prepuce or foreskin. Penis: Anatomy

Clinical classification

Pathophysiology

Frostbite injury results from:

• Immediate cold-induced cell death Cell death Injurious stimuli trigger the process of cellular adaptation, whereby cells respond to withstand the harmful changes in their environment. Overwhelmed adaptive mechanisms lead to cell injury. Mild stimuli produce reversible injury. If the stimulus is severe or persistent, injury becomes irreversible. Apoptosis is programmed cell death, a mechanism with both physiologic and pathologic effects. Cell Injury and Death 
  • Tissue cools below subfreezing → extra and intracellular ice crystals form
  • Fluid and electrolyte fluxes → lysis of cell membranes with subsequent cell death Cell death Injurious stimuli trigger the process of cellular adaptation, whereby cells respond to withstand the harmful changes in their environment. Overwhelmed adaptive mechanisms lead to cell injury. Mild stimuli produce reversible injury. If the stimulus is severe or persistent, injury becomes irreversible. Apoptosis is programmed cell death, a mechanism with both physiologic and pathologic effects. Cell Injury and Death
  • Inflammatory process mediated by thromboxane A2 Thromboxane A2 An unstable intermediate between the prostaglandin endoperoxides and thromboxane B2. The compound has a bicyclic oxaneoxetane structure. It is a potent inducer of platelet aggregation and causes vasoconstriction. It is the principal component of rabbit aorta contracting substance (RCS). Arterial Pressure Regulation, prostaglandin F2-alpha, bradykinins, and histamine
  • Leads to tissue ischemia Ischemia A hypoperfusion of the blood through an organ or tissue caused by a pathologic constriction or obstruction of its blood vessels, or an absence of blood circulation. Ischemic Cell Damage and necrosis Necrosis The death of cells in an organ or tissue due to disease, injury or failure of the blood supply. Ischemic Cell Damage 
  • Worsened in setting of thawing followed by refreezing 
• Tissue ischemia Ischemia A hypoperfusion of the blood through an organ or tissue caused by a pathologic constriction or obstruction of its blood vessels, or an absence of blood circulation. Ischemic Cell Damage
  • Decreased temperatures increase blood viscosity Blood viscosity The internal resistance of the blood to shear forces. The in vitro measure of whole blood viscosity is of limited clinical utility because it bears little relationship to the actual viscosity within the circulation, but an increase in the viscosity of circulating blood can contribute to morbidity in patients suffering from disorders such as sickle cell anemia and polycythemia. Vascular Resistance, Flow, and Mean Arterial Pressure → microthrombi
  • Vasodilation Vasodilation The physiological widening of blood vessels by relaxing the underlying vascular smooth muscle. Pulmonary Hypertension Drugs and stasis result in tissue hypoperfusion and ischemia Ischemia A hypoperfusion of the blood through an organ or tissue caused by a pathologic constriction or obstruction of its blood vessels, or an absence of blood circulation. Ischemic Cell Damage.
• Reperfusion-related localized inflammatory processes 
  • Caused by return of blood flow Blood flow Blood flow refers to the movement of a certain volume of blood through the vasculature over a given unit of time (e.g., mL per minute). Vascular Resistance, Flow, and Mean Arterial Pressure to ischemic areas
  • Activated endothelial cells release Release Release of a virus from the host cell following virus assembly and maturation. Egress can occur by host cell lysis, exocytosis, or budding through the plasma membrane. Virology activated oxygen species, initiating inflammatory response.
  • WBCs flood to perfused area, releasing inflammatory mediators.
  • Leads to cell death Cell death Injurious stimuli trigger the process of cellular adaptation, whereby cells respond to withstand the harmful changes in their environment. Overwhelmed adaptive mechanisms lead to cell injury. Mild stimuli produce reversible injury. If the stimulus is severe or persistent, injury becomes irreversible. Apoptosis is programmed cell death, a mechanism with both physiologic and pathologic effects. Cell Injury and Death

4 phases:

1. Pre-freeze:
   • Tissue cooling
   • Vasoconstriction Vasoconstriction The physiological narrowing of blood vessels by contraction of the vascular smooth muscle. Vascular Resistance, Flow, and Mean Arterial Pressure
   • Ischemia Ischemia A hypoperfusion of the blood through an organ or tissue caused by a pathologic constriction or obstruction of its blood vessels, or an absence of blood circulation. Ischemic Cell Damage
   • Endothelial leakage
2. Freeze-thaw:
   • Ice crystal formation
   • Cellular dehydration Dehydration The condition that results from excessive loss of water from a living organism. Volume Depletion and Dehydration and death
3. Vascular stasis: microvascular thrombus formation
4. Late progressive ischemia Ischemia A hypoperfusion of the blood through an organ or tissue caused by a pathologic constriction or obstruction of its blood vessels, or an absence of blood circulation. Ischemic Cell Damage:
   • Hypoperfusion
   • Inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body’s defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation
   • Tissue necrosis Necrosis The death of cells in an organ or tissue due to disease, injury or failure of the blood supply. Ischemic Cell Damage

Diagnosis

The diagnosis of frostbite is clinical and should be distinguished from less severe forms of cold injury (frostnip).

• Frostnip:
  • No ice formation, no tissue loss
  • Cannot clinically distinguish between frostnip and frostbite initially
  • Passive rewarming
  • If no tissue loss, frostnip
• Frostbite (severe form of injuries that may present in any of following stages):
  • Stage 1 Stage 1 Trypanosoma brucei/African trypanosomiasis: involves superficial areas of skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Skin: Structure and Functions and presents with hyperemia, itching
  • Stage 2: characterized by blisters, desquamation Desquamation Staphylococcal Scalded Skin Syndrome (SSSS), edema Edema Edema is a condition in which excess serous fluid accumulates in the body cavity or interstitial space of connective tissues. Edema is a symptom observed in several medical conditions. It can be categorized into 2 types, namely, peripheral (in the extremities) and internal (in an organ or body cavity). Edema
  • Stage 3: ulceration Ulceration Corneal Abrasions, Erosion, and Ulcers and involvement of skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Skin: Structure and Functions and subcutaneous tissue Subcutaneous tissue Loose connective tissue lying under the dermis, which binds skin loosely to subjacent tissues. It may contain a pad of adipocytes, which vary in number according to the area of the body and vary in size according to the nutritional state. Soft Tissue Abscess
  • Stage 4: deeper injury of connective tissues, muscle, and bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Bones: Structure and Types necrosis Necrosis The death of cells in an organ or tissue due to disease, injury or failure of the blood supply. Ischemic Cell Damage leading to gangrenous limbs

Management

Prehospital

• Remove any wet clothing.
• Bring patient to a warm environment.
• Do not put pressure on frostbitten extremities (e.g., rubbing frostbitten extremities or walking on feet affected by frostbite).
• Do not rewarm if there is a chance that freezing will recur.

Rewarming

• Rewarm in warm water (37–39°C (98.6°–102.2°F)) bath.
• Provide parenteral analgesia Analgesia Methods of pain relief that may be used with or in place of analgesics. Anesthesiology: History and Basic Concepts during rewarming.
• Thawing completed when tissue is red or purple and soft to the touch

Wound care

• Application of bulky dressing
• Elevation to reduce edema Edema Edema is a condition in which excess serous fluid accumulates in the body cavity or interstitial space of connective tissues. Edema is a symptom observed in several medical conditions. It can be categorized into 2 types, namely, peripheral (in the extremities) and internal (in an organ or body cavity). Edema
• Daily hydrotherapy to improve range of motion Range of motion The distance and direction to which a bone joint can be extended. Range of motion is a function of the condition of the joints, muscles, and connective tissues involved. Joint flexibility can be improved through appropriate muscle strength exercises. Examination of the Upper Limbs
• Aspirin Aspirin The prototypical analgesic used in the treatment of mild to moderate pain. It has anti-inflammatory and antipyretic properties and acts as an inhibitor of cyclooxygenase which results in the inhibition of the biosynthesis of prostaglandins. Aspirin also inhibits platelet aggregation and is used in the prevention of arterial and venous thrombosis. Nonsteroidal Antiinflammatory Drugs (NSAIDs) and nonsteroidal anti-inflammatory drugs ( NSAIDs NSAIDS Primary vs Secondary Headaches) to help reduce inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body’s defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation
• Tetanus-reported complication; prophylaxis Prophylaxis Cephalosporins recommended

Thrombolysis

• Used in severe, limb-threatening cases, presenting within 24 hours
• Options include intravenous or intra-arterial tissue plasminogen activator Tissue plasminogen activator A proteolytic enzyme in the serine protease family found in many tissues which converts plasminogen to fibrinolysin. It has fibrin-binding activity and is immunologically different from urokinase-type plasminogen activator. The primary sequence, composed of 527 amino acids, is identical in both the naturally occurring and synthetic proteases. Hemostasis ( tPA tPA Ischemic Stroke), or intravenous or intra-arterial heparin or enoxaparin Enoxaparin Low-molecular-weight fragment of heparin, having a 4-enopyranosuronate sodium structure at the non-reducing end of the chain. It is prepared by depolymerization of the benzylic ester of porcine mucosal heparin. Therapeutically, it is used as an antithrombotic agent. Anticoagulants.

Surgical management

• Initial assessment might overestimate real extent of tissue injury.
• No surgical treatment until demarcation occurs
• “Frostbite in January, amputation Amputation An amputation is the separation of a portion of the limb or the entire limb from the body, along with the bone. Amputations are generally indicated for conditions that compromise the viability of the limb or promote the spread of a local process that could manifest systemically. Amputation in July”

Clinical Relevance

• Raynaud’s phenomenon: exaggerated vascular response to cold temperatures or emotional stress causing sharply demarcated color changes of digits. Blood vessels constrict, which leads to digits turning blue. Digits return to normal color 10–20 minutes after cold is removed.
• Hypothermia Hypothermia Hypothermia can be defined as a drop in the core body temperature below 35°C (95°F) and is classified into mild, moderate, severe, and profound forms based on the degree of temperature decrease. Hypothermia: drop in core body temperature Body Temperature The measure of the level of heat of a human or animal. Heatstroke ＜ 35°C (95°F). Classified into mild, moderate, and severe forms. Management involves rewarming of patient by external or internal methods, depending on severity.