Phosgene Oxime Exposure 

Updated: Apr 08, 2020
Author: Erik D Schraga, MD; Chief Editor: Zygmunt F Dembek, PhD, MPH, MS, LHD 

Overview

Practice Essentials

Phosgene oxime (CX) is an urticant or nettle agent that causes a corrosive type of skin and tissue injury. Although CX is often grouped with the vesicant chemical warfare agents, it is not a true vesicant because it does not cause blisters.[1, 2, 3, 4]  Both vapor and liquid CX cause immediate tissue damage on contact. CX in its pure form is a colorless, crystalline solid at temperatures below 95°F, but the vapor pressure of the solid is high enough to produce symptoms. As a munitions grade compound, CX is in liquid form with a yellowish brown appearance.

Although Germany and Russia both developed CX before World War II, no uses of the agent on the battlefield are known. CX is of military interest because it penetrates garments and rubber much more quickly than other chemical agents and it produces a rapid onset of severe and prolonged effects.[4, 5, 6]  For this reason, it could be produced as a weaponized mixture with other chemical warfare agents to enhance their deleterious effects. No antidotes against CX-induced injury are available; treatment is supportive.[7]

For related information, see Medscape's Disaster Preparedness and Aftermath Resource Center.

Pathophysiology

The mechanism of toxicity for CX is uncertain.[8] Possible mechanisms of toxicity include necrotizing effects of the chloride component or a direct effect of the oxime or carbonyl groups. It primarily affects the skin, eyes, respiratory system, and gastrointestinal tract. The agent seems to cause its greatest systemic effects in the first capillary bed encountered. For example, skin exposure or intravenous (IV) injection of CX causes pulmonary edema, while injection into the portal vein produces hepatic necrosis but not pulmonary edema.[8]

The acute effects of CX following its cutaneous exposure in SKH-1 hairless mice show that topical cutaneous exposure to CX vapor causes blanching of exposed skin with an erythematous ring, necrosis, edema, mild urticaria and erythema within minutes after exposure and up to 8 hours post-exposure. These clinical skin manifestations were accompanied with increases in skin thickness, apoptotic cell death, mast cell degranulation, myeloperoxidase activity indicating neutrophilinfiltration, p53 phosphorylation and accumulation, and an increase in COX-2 and TNFα levels. Topical CX-exposure also resulted in the dilatation of the peripheral vessels with a robust increase in red blood cells in vessels of the liver, spleen, kidney, lungs and heart tissues. These events could cause a drop in blood pressure leading to shock, hypoxia and death.[9]

Epidemiology

Exposures to CX result from its deliberate use as a chemical warfare agent.[1, 4, 6]   Since this chemical has no useful industrial applications, accidental exposures are extremely unlikely.

 

Prognosis

Prognosis is generally good for minimal exposures. Severe and early respiratory distress portends a poor prognosis. Morbidity and mortality for exposures to CX are dose dependent. Concentrations below 8% cause no or inconsistent effects.[10]  The estimated LCt50 (concentration-time product capable of killing 50% of exposures) for CX vapor is 1500-2000 mg·min/m3. The LD50 (lethal dose for 50% of exposures) for skin exposures is estimated at 25 mg/kg. Skin and mucous membrane irritation can begin within 12 seconds of a vapor exposure of 0.2 mg·min/m3. Unbearable pain and irritation occur within 1 minute of vapor exposure to 3 mg·min/m3.

Potential complications include the following:

  • Scarring
  • Wound infections
  • Loss of vision
  • Death from severe respiratory injury

Patient Education

Educate outpatients about the signs and symptoms of wound infection, for which they immediately should seek further medical care. For patient education information, see Chemical Warfare and Personal Protective Equipment.[1, 4]

 

Presentation

History

Important historic features of a potential toxic chemical exposure include the following:

  • Estimated time of occurrence

  • Duration and circumstances of exposure

  • Onset and time course of symptoms

  • Odor and/or color of gases or vapors

  • Protective clothing worn (if any)

  • Effects on surroundings (eg, other human or animal casualties)

CX casualties typically report unbearable pain in exposed skin and eyes; difficulty with sight or blindness after ocular exposure; and sore throat, hoarseness, dyspnea, chest pain, and cough after respiratory exposure.

Some casualties may experience a peppery or pungent odor during their initial CX vapor exposure, but this is typically lost quickly because of accommodation.

When mixed with another chemical agent (eg, VX), the rapid skin damage caused by phosgene oxime enables a greater dermal susceptibility to the second agent.[10]

Physical Examination

Skin

A blanching, grayish skin lesion surrounded by an erythematous ring can be observed within 30 seconds of exposure. A wheal develops on exposed skin within 30 minutes. The original blanched area acquires a necrotic, brown pigmentation by 24 hours. An eschar forms in the pigmented area by 1 week and sloughs after approximately 3 weeks. Healing may be incomplete 4 to 6 months post-exposure.[10]

Eyes

Eye examination typically demonstrates pain, conjunctivitis, lacrimation, lid edema, and blepharospasm after even minute exposures. More severe exposures can result in keratitis, iritis, corneal perforation, and blindness.

Respiratory

Irritation of the mucous membranes may be observed on examination of the oropharynx and nose. Evidence of pulmonary edema, including rales and wheezes, may be noted on auscultation. Necrotizing bronchiolitis and pulmonary venule thromboses are prominent features of severe CX exposure.[11]

Gastrointestinal

Some animal data suggest that CX may cause hemorrhagic inflammatory changes in the GI tract.

 

DDx

 

Workup

Approach Considerations

An arterial blood gas may be useful only in patients with significant respiratory symptoms after exposure. Order a chest radiograph to examine for evidence of pulmonary edema in patients with respiratory symptoms after exposure. A chest radiograph of a patient who developed phosgene-induced adult respiratory distress syndrome is shown below.

Anteroposterior portable chest radiograph in a mal Anteroposterior portable chest radiograph in a male patient who developed phosgene-induced adult respiratory distress syndrome. Notice the bilateral infiltrates and ground glass appearance.
 

Treatment

Prehospital Care

Removal of casualties from the source of exposure and rapid decontamination are the key aspects of prehospital care. Decontamination consists of removal of all clothing, wiping all gross materials from skin, rinsing with copious amounts of soap and water, washing with 0.5% hypochlorite solution, or use of resin compounds.

Administer oxygen to patients with significant respiratory distress. Endotracheal intubation and ventilatory support may be required for patients with severe airway exposures or progressive pulmonary symptoms.[12, 13]

Administer sufficient doses of systemic analgesics as soon as possible.

Emergency Department Care

Emergency department care is a continuation of prehospital care and is supportive in nature. No antidotes exist for phosgene oxime exposure. Although corticosteroid treatment has been given to patients exposed to chlorine gas, which causes a similar syndrome, evidence is limited on its efficacy and safety in the treatment of phosgene exposure.[5, 12, 13] Verify complete decontamination to ensure that no medical personnel become casualties.

Airway and/or pulmonary include the following:[11]

  • Be alert to the possible need for airway management in patients with severe exposure
  • Administer oxygen to patients with significant respiratory symptoms
  • Provide supportive care for noncardiogenic pulmonary edema, as required

Pain associated with CX exposure is nearly unbearable. Ensure that adequate systemic, preferably parenteral, analgesics are administered.

Apply topical antibiotics to eye lesions to reduce risk of infection and adhesions. Topical anticholinergics may reduce the risk of future synechiae formation. Eye lesions require the same care as would be done for damage from a corrosive substance.

Initiate wound management as appropriate for any other necrotic and/or ulcerated lesion. 

Admit any patients demonstrating significant respiratory symptoms for observation and supportive care. Transfer to a higher-level medical center may be required for severe pulmonary CX injuries if the initial hospital is unable to provide the necessary intensive care support. Secure the airway and initiate ventilatory support prior to transfer.

Pain associated with phosgene oxime (CX) exposure typically remains severe for several days. Consider admission for pain control. Inpatient medications include the following:

  • Parenteral analgesics (eg, morphine, meperidine)
  • Broad-spectrum ophthalmic antibiotic ointments for eye injuries
  • Broad-spectrum topical antibiotic ointments for skin burns

Patients may be treated on an outpatient basis once respiratory symptoms have resolved and nonparenteral analgesics are adequate for pain control. Outpatient medications include oral analgesics (eg, codeine, oxycodone) if continued pain management is required after discharge and continued antibiotic ointments for eye and skin injuries until full healing has occurred.

Instruct the patient on appropriate wound care techniques and provide close follow-up care to the patient to ensure adequate healing. Ophthalmology follow-up care to ensure resolution of ocular injuries also is important.

Consultations

Consult ophthalmology to provide close follow-up care for significant ocular exposures. Consult plastic surgery for severe dermal damage.

 

Medication

Medication Summary

No medications are specific to the treatment of phosgene oxime exposure. The emergency department physician should use analgesics and topical antibiotics as preferred.[12, 13]

Parenteral analgesics

Class Summary

CX injuries are extremely painful and require liberal use of parenteral analgesics. No recommendations for specific parenteral analgesics are available. Select a medication (eg, morphine, meperidine) that is readily available and provides adequate pain relief for the patient.

Morphine sulfate (Duramorph, Astramorph, MS Contin)

An alkaloid of opium and a commonly used systemic narcotic analgesic; a good first choice parenteral medication that may be titrated to patient needs.

Meperidine (Demerol)

Narcotic analgesic with multiple actions qualitatively similar to those of morphine, typically administered in conjunction with promethazine.

Topical antibiotic ointments

Class Summary

Indicated for treatment of CX injury of skin and eyes; no specific ointments are recommended; select an available broad-spectrum ophthalmic or skin preparation (eg, bacitracin, Ilotycin).

Bacitracin (AK-Tracin, Baciguent)

Broad-spectrum antibiotic topical ointment that is a good first choice for superficial wound care.

Erythromycin ophthalmic (Ilotycin, E-mycin)

Broad-spectrum macrolide antibiotic indicated in treatment or prevention of superficial ocular infections.

Oral analgesics

Class Summary

Patients may be switched from parenteral analgesics to an oral form once their injuries have improved sufficiently to tolerate alternative pain control measures; no specific recommendations are available; use a readily available product (eg, Percocet, Tylenol with codeine) that provides adequate pain relief and is well tolerated by the patient.

Oxycodone/acetaminophen (Percocet)

Semisynthetic opioid analgesic with multiple actions similar to those of morphine; acetaminophen is a nonopiate nonsalicylate analgesic and antipyretic.

Acetaminophen/codeine (Tylenol with codeine)

Combines analgesic effects of a centrally acting opium-derived alkaloid (codeine) and a peripherally acting nonopioid analgesic (acetaminophen).