Chemical burns

Intro

• Make up only 10% of burns centre admissions but 30% of deaths
• Acids cause coagulative necrosis with protein precipitation and a tough leathery eschar that can limit deeper penetration of the agent
• Alkalis cause liquefactive necrosis with deeper, ongoing burns
• Early death is usually due to hypotension, acute renal failure and shock, however, systemic absorption of the chemical can lead to acidosis, hypotension, hyperkalaemia and dysrhythmias

General approach

• Remove patient from further exposure with universal precautions
• Aggressive irrigation with water is the cornerstone for almost all cases
  • Dry chemical particles e.g. lime should be brushed away before irrigation
  • Sodium metal and related compounds should be brushed away or covered with mineral oil or excised prior to irrigation as water induces a severe exothermic reaction
  • Dilution of phenol (carbolic acid) with water may enhance penetration
• Almost universally, early irrigation means a better prognosis
• Time to irrigation
  • If done at 3 minutes, twofold greater chance of full thickness burn than if done at 1 minute
• Irrigation should continue until pH neutral
• Then treat as for thermal burn

Factors influencing tissue damage

• Type of chemical
• Concentration of agent
• Quantity of agent
• Duration of exposure
• Mechanism of action
• Extent of penetration

Factors influencing percutaneous absorption

• Body site – Thin skin, large surface area, age
• Integrity of skin
• Nature of the chemical – Lipid solubility, pH, concentration
• Duration of contact – Inadequate irrigation, chemical-soaked clothing, occlusive garments

Classification of agents

• Acids – Coagulative necrosis via proton donation
• Alkali – Liquefactive necrosis via proton acceptance
• Organic solvents – Disruption of cellular membranes
• Inorganic solvents – Scavenge ions and salt production within tissues

Acid burns

• Factors that increase severity
  • pH
  • Concentration
  • Molarity
  • Complexing affinity for hydroxyl ions
  • Type e.g. hydrofluoric acid does not cause coagulation necrosis
• Contact time with skin is the most important feature that healthcare workers can alter

Acid burns

• Acetic acid
  • Dilute (<40%) acetic acid in chemical hair straightener is the most common chemical burn to the scalp in females
  • Prolonged contact, especially with damaged scalp skin, can cause a partial thickness burn that heals slowly and is prone to infection
  • Copious wound irrigation and oral antibiotics if open scalp wound

Acid burns

• Carbolic acid (phenol)
  • Corrosive organic acid causes relatively painless white or brown coagulum
  • Dilute phenol penetrates tissues more readily than concentrated
  • Systemic absorption can lead to dysrhythmias or seizures
  • 1-2% concentrations can cause burns if contact period is long enough
  • Cresol, creosote and cresylic acid are chemically related compounds
  • Coagulation necrosis is common with phenol trapped under eschar
    • Water lavage alone may not reach this
    • Thus can use undiluted PEG (MW 200-4oo) or gentle wash with isopropyl alcohol (equally effective)
    • Reduce cutaneous corrosion and decreases systemic toxicity

Acid burns

• Chromic acid
  • Powerful oxidisers
  • Chromate ion produces chronic penetrating ulceration
  • Also get conjunctivitis, lacrimation and ulceration of the nasal septum
  • Systemic chromium toxicity can cause liver or renal failure, GI bleeding, coagulopathy and CNS disturbances
  • 1-2% BSA can cause significant symptoms
  • 10% BSA cutaneous burn can be fatal due to systemic toxicity
  • Copious water irrigation and observation for systemic features
  • Aggressive excision of coagulum prevents absorption of chromium from burn site

Acid burns

• Formic acid
  • Coagulative necrosis
  • Reduced ventilation, HAGMA and haemolysis can all occur
  • Immediate decontamination and irrigation with water
  • IV bicarb may be required or exchange transfusions for severe haemolysis

Acid burns

• Hydrochloric and sulfuric acid
  • Burn skin dark brown or black
  • Treat as for formic acid burns
  • Copious irrigation is usually sufficient to prevent severe skin burns

Acid burns

• Hydrofluoric acid
  • Penetrates deeply unlike other acids
  • Products burns by:
    • 1) Hydro ions cause direct cellular damage
    • 2) Free fluoride ions scavenge intracellular cations, such as calcium and magnesium, disrupt cellular membranes and inhibit Na/K ATPase
  • Leads to systemic hypocalcaemia/hypomagnesaemia and hyperkalaemia
  • Free fluoride ions cause spontaneous depolarisation of nerve tissue and severe pain
  • Pain persists until all free fluoride ions neutralised
  • Initial dermal effects are minimal and are related to concentration rather than duration of exposure
    • >50% cause immediate pain and tisue damage
    • <20% no signs and symptoms until 12-24 hours later with blue-grey skin and surrounding erythema

Acid burns

• Hydrofluoric acid
  • Treatment
    • Phase 1
      • Copious water irrigation for 30 minutes
      • If <20% concentration, brief exposure and decontamination initiated rapidly this may be enough
      • Severe, persistent pain denotes more severe injury and second phase required
    • Phase 2
      • Calcium gluconate topically (25mL of 10% calcium gluconate in 75mL of water-soluble lubricant) generously applied to affected skin to replace calcium ions and detoxify the enzyme-poisoning fluoride ions
        • Limited to mild, superficial burns as will not penetrate deeper burns
      • Severe burns require intradermal and intra-arterial injections
        • 0.5mL/cm2 of 10% calcium gluconate via 27G needle intradermal injection
        • Elimination of pain can be used as a guide to therapy

Acid burns

• Hydrofluoric acid
  • Issues with intradermal injection
    • Limited delivery of calcium
    • Free calcium ions cause more pain initially
    • Vascular compromise if inject large volumes
    • Rapid penetration of hydrofluoric acid beneath nail bed requires nail removal and injection directly into nail bed
  • Contamination of hands, feet, digits or nails requires toxicology and plastics consult
  • Intra-arterial injection
    • Arterial line proximal to site involved
    • 50mL syringe with 10mL 10% calcium gluconate and 40mL 5% dextrose infused over 4 hours
    • Art line trace confirms siting in vessel as extravasation can be catastrophic
    • Can repeat if still painful at 4 hours

Acid burns

• Hydrofluoric acid
  • Inhalational injury
    • Can cause immediate or delayed pulmonary injury
    • Admit all for observation
    • Nebulised calcium gluconate 1.5mL of 10% calcium gluconate into 4.5mL of sterile water for nebulisation
  • Ocular injury
    • Water irrigation for at least 30 minutes and urgent ophthal review
    • Calcium-containing irrigating solutions may be harmful and are not recommended
    • Systemic absorption is also possible
  • Systemic toxicity
    • VF due to systemic acidosis, hyperkalaemia, hypomagnesaemia and/or hypocalcaemia
    • Administer IV calcium and magnesium in major HFl acid burns before lab results back
    • Once hypoCa or hypoMg have developed, it is very hard to remedy the situation so need to be proactive

Acid burns

• Methacrylic acid
  • Copious water irrigation
• Nitric acid
  • Oxidation with yellow skin discolouration
  • Copious water irrigation
• Oxalic acid
  • Binds calcium and prevents muscle contraction
  • Irrigate and IV calcium may be required

Alkali burns

• Penetrate deeper and greater risk of systemic toxicity
• May initially appear superficial but develop full-thickness over 2-3 days
• Combine with proteins and lipids to form soluble protein complexes and soaps that permit hydroxyl ions to penetrate tissues
• Soft, gelatinous, brownish eschars develop
• Strong alkalis have pH >12

Alkali burns

• Lyes
  • Strong, corrosive alkalis including ammonium, barium, calcium, lithium, potassium (caustic potash) and sodium (caustic soda) hydroxides
  • Immediate, voluminous and persistent irrigation is key
  • Extremely corrosive and penetrating requiring copious irrigation for long periods of time
  • Early surgical intervention and airway intervention for ingestion is key

Alkali burns

• Lime
  • Calcium oxide
  • Converted by water to alkali calcium hydroxide
  • Upon skin contact, draws water out of skin
  • All dry lime particles therefore need to be brushed off prior to irrigation
  • Even small amount of water can cause exothermic reaction and burns
  • Brisk irrigation can then lessen burn and dissipate heat

Metal burns

• When exposed to air, some elemental metal spontaneously ignite
• Water is generally contraindicated for extinguishing burning metal fragments embedded in skin due to risk of ignition, exothermic reaction and further tissue injury
• Can use class D fire extinguisher, smother with sand or cover with mineral oil
• Wound debridement should include metal FB excision and placement in mineral oil to prevent further ignition

Hydrocarbons

• Gasoline
  • Fat-dissolving corrosive injury (defatting dermatitis)
  • Resembles thermal scald
  • Can cause neurological, pulmonary, cardiovascular, GI and hepatic injuries
  • Treat by decontamination with soap and water and then as for a thermal burn
• Hot tar
  • Usually more thermal than chemical burns (260 degrees)
  • If hot, the tar should be cooled to prevent continued thermal injury
  • Polysorbate (in many topical antimicrobials), baby oil and industrial removal agents (De-Solv-It) can all help to remove solidifed tar

Vesicants

• Dimethyl sulfoxide (non-prescription topical agent for minor sprains/burns), cantharides (Spanish fly aphrodisiac) and mustard gas (chemical warfare)
• Drying agents
• Get ischaemia and anoxic necrosis at site of exposure
• Immediate copious irrigation
• Decontaminate with adsorbent agents e.g. flour, talcum powder and fuller’s earth if supply of water is limited
  • The wipe away with moist towel
• Povidone iodine may be very helpful for sulfur mustard decontamination

Potassium permanganate

• Concentrated solutions of this oxidising agents can produce dermal burns with thick, purple eschar of coagulated protein
• Copiously irrigate

Alkyl mercury compounds

• Reducing agents used in disinfectants and fungicides
• Erythematous with blistering
• Blister fluid is high in mercury content and continues the burning process
• Need blister debridement, drainage and copious irrigation

Tear gas

• Skin and mucosal irritation within 20-60 seconds of exposure
• Can cause contact dermatitis
• Inhalational and eye injuries can be severe
• Need rapid removal and copious irrigation
• Ocular irrigation is required with subsequent slit lamp exam
• Arrange ophthal follow-up within 24 hours
• Inhalational injuries require bronchodilators and oxygen therapy. No role for steroids

White phosphorous

• Used in fireworks, firearms, insecticides, rodenticides and fertiliser
• Ignites when exposed to air
• Flaming droplets may embed beneath the skin and continue to oxidise
• Copiously irrigate and immerse in water until completely debrided
• Wood’s lamp examination aids debridement as it fluoresces
• Copper sulfate solution can detoxify phosphorous but causes haemolysis and increased mortality (DO NOT USE)
• Systemic absorption can cause hypocalcaemia, hyperkalaemia, hepatic and renal injury
• Avoid direct contact with any secretions/body fluids and agent itself
• Admit all and consider transfer to burns centre

Airbag burns

• Sodium azide and cupric oxide solid propellants result in exothermic reaction and rapid inflation
• Corrosives such as sodium hydroxide, nitric oxide, ammonia and multiple hydrocarbons can result from detonation leading to friction, thermal and chemical burns
• Sodium hydroxide can cause chemical keratitis
• Need slit-lamp examination and treat any burns as for alkali burns with copious prolonged irrigation with water or saline

Ocular burns

• 30 minutes minimum water/saline irrigation
• For severe alkali burns, up to 24 hours of irrigation may be required
• Conjunctival sac pH to return to 7.4 is helpful for continuing irrigation decisions
  • However, if strong alkaline or hydrofluoric acid burns with obvious examination abnormality, should continue for at least 2-3 hours despite normal pH to ensure anterior chamber neutralisation
• Can sweep fornices with a wet cotton applicator to remove any particular matter, particularly if irrigation is not neutralising pH effectively
• IV narcotic analgesia may be required
• Emergent ophthalmology is required

Last Updated on October 9, 2020 by Andrew Crofton