Phenol is a disinfectant and chemical precursor with a variety of uses and indications. Joseph Lister introduced the concept of antiseptic surgery using phenol, then known as carbolic acid. Reports of toxicity were not far behind. Phenol remained a healthcare disinfectant through much of the 20th century, but its use in healthcare settings is now uncommon. Phenol has a long history of use in dermatology as a chemical peel and skin rejuvenator, but recently, laser treatments have surpassed it. Podiatrists use phenol for nailbed matrix ablation following ingrown toenail removal.
Phenol is still occasionally a component in some household disinfectants and a variety of gargles and ointments. Phenol-containing solutions are also home remedies for head lice. Methylated phenols, called cresols, are also found in home disinfectant products and may produce clinical toxicity similar to phenol.
Phenol is a common laboratory chemical used in the extraction of nucleic acid material from biological specimens. It also serves as a chemical precursor to many pharmaceuticals and chemicals, including acetaminophen, aspirin, levodopa, propofol, and some herbicides.
Acute phenol toxicity mainly occurs through unintentional exposure in the home or workplace; intentional exposures are much less common. Severe toxicity has occurred from accidental ingestions in healthcare settings. Recurring occupational exposures in the explosives production industry and healthcare settings resulted in a historical syndrome of malaise, fatigue, and hepatitis called “phenol marasmus.” Today, phenol exposures are more likely to result in dermal exposures following spills in the laboratory or industrial settings.
Phenol is a protoplasmic poison with myriad effects. Its dual hydrophilic and lipophilic properties allow it to easily break through cellular membranes, denaturing proteins along the way, ultimately leading to cell death and necrosis. A caustic effect resulting in coagulation necrosis can also occur. Phenol distributes widely and with severe toxicity, results in pathologic effects involving most organ systems.
Substituted phenol derivatives possess an additional mechanism of toxicity by uncoupling oxidative phosphorylation, potentially resulting in severe toxicity manifesting as hyperthermia and acidosis. Examples include 2,4-dinitrophenol (DNP), pentachlorophenol, and dinitro-ortho-cresol (DNOC).
Phenol is readily absorbed through multiple routes of exposure (ingestion, dermal, inhalational) and distributes widely through the body within minutes. It is believed to undergo hepatic metabolism similar to that of acetaminophen via glucuronidation, sulfonation, and oxidation via CYP2E1. These metabolites get excreted renally.
Efforts to obtain history should not delay the treatment of life-threatening toxicity. Furthermore, patients with severe phenol toxicity may be unable to provide a history of exposure due to depressed mental status or seizures. When appropriate, a focused history should seek to determine the toxin of concern, which includes the concentration, dose, route, and time of exposure. Questions regarding the wear of personal protective equipment (PPE) such as gloves, coveralls, or respirators may help to stratify the degree of exposure and possible routes of exposure. Following workplace and household exposures, safety data sheet (SDS) review may be helpful to identify active ingredients.
The clinician might detect the sweet, medicinal odor of phenol and provide a clue to the exposure. The onset of clinical effects vary by route of exposure but would be expected to occur within minutes to less than one hour. Examination findings may also vary by route of exposure. Central nervous system excitation or depression may occur rapidly, resulting in coma or seizures within minutes. Vomiting or other signs of gastrointestinal irritation may be presenting symptoms. White patches may be present in the oropharynx. Increased work of breathing and/or hypoxia may be a feature secondary to the development of acute respiratory distress syndrome (ARDS). Severe phenol poisonings may also result in cardiovascular instability to include ventricular arrhythmias and hypotension. Rhythmic perioral movements, the so-called “rabbit syndrome,” may occur after resolution of life-threatening toxicity.
Dermal exposure to small amounts of phenol will acutely result in a painless, white discoloration of the skin at the site of contact. Deeper burns may occur if decontamination does not occur promptly. The skin may later progress to erythema and blistering and in some cases, necrosis. Interestingly, phenol burns may also present with initial erythema at the site of contact, followed by brown staining of the skin. Of note, these lesions are frequently painless due to the anesthetic, cooling effect of topical phenol. Desquamation of skin may occur over 3 to 5 days following contact before healing begins. Dermatologists historically utilized this progression of phenol chemical burns in facial chemical peels.
Laboratory assessment of phenol exposure is not widely available, and in most cases, will not alter initial management. However, if desired, laboratory confirmation of exposure can be performed by obtaining a serum or urine phenol level. Monitoring of urine phenol levels is a common practice in workplaces with occupational benzene exposure but has no definitive role in acute phenol poisoning.
Phenol-exposed patients should receive regular monitoring of vital signs and mental status. A baseline electrocardiogram should be obtained as well as continuous cardiac monitoring to evaluate for dysrhythmias. Laboratory evaluation should focus on identifying the presence of acute kidney injury, metabolic acidosis, hepatitis, rhabdomyolysis, or methemoglobinemia. In cases of ingestion or inhalational exposure, or patients with hypoxemia or respiratory complaints, a chest radiograph should be obtained. Phenol metabolites may also produce characteristic blue-green urine that may provide a clue to the diagnosis in cases of unknown exposure.
Ingestion or dermal exposure to phenol concentrations greater than 5% should receive a referral to an emergency department for evaluation. Consultation with a regional poison control center in the United States is possible by calling 1-800-222-1222.
The clinical evaluation of a phenol poisoned patient should focus first on primary supportive measures such as ensuring a patent airway, supporting ventilation and oxygenation, and hemodynamic support as needed.
There have been proposals for a variety of decontamination agents have for external decontamination of phenol exposure. However, low molecular weight (300-400MW) polyethylene glycol (PEG) is the currently accepted decontamination fluid. It is critical to note that this is not the same as high molecular weight PEG typically used in medical settings as a bowel preparation or osmotic laxative. LMW PEG should be included in phenol exposure first aid kits in labs or worksites using phenol to provide external decontamination as soon as possible. Decontamination should take place with an LMW PEG soaked sponge or towel to wipe away residual phenol. When LMW PEG is not available, flushing the exposed area with copious amounts of water for 15 minutes may be effective. Early studies showed potentially increased absorption of phenol when using only small amounts of water. Isopropyl alcohol may also be as effective as LMW PEG for external phenol decontamination. For ocular exposure to phenol, the eyes should be flushed with copious amounts of water or saline for at least 15 minutes after exposure.
Gastrointestinal decontamination with activated charcoal is generally not recommended following phenol ingestion. The risk of aspiration in the setting of phenol induced seizures likely outweigh the potential benefit of activated charcoal. Furthermore, activated charcoal may obscure or confuse the visualization of gastrointestinal endoscopic findings. Upper endoscopy should be a consideration for patients following phenol ingestion to grade the degree of esophageal injury.
Management of extensive surface area phenol burns should take place in conjunction with a regional burn center. Extra-corporeal removal of phenol by hemodialysis is not recommended. However, hemodialysis may be necessary to manage the complications of phenol toxicity. Patients with systemic manifestations of phenol toxicity should be admitted to a monitored setting for at least 24 hours. Asymptomatic patients with normal vital signs and laboratory findings may obtain release from emergency care after 6 to 8 hours of monitoring.
The differential diagnosis of the manifestations of phenol toxicity is broad, given that phenol exerts effects on nearly all organ systems. Dermal exposure may present similar to that of other potent acid or alkali exposures, but the characteristic brown-stained skin may be a clue to phenol. Hypopigmented skin may also present with hydrofluoric acid dermal exposures. The combination of seizures and cardiovascular collapse is very non-specific and is observable with a broad range of life-threatening toxin exposures. The characteristic blue-green urine is also a possible feature with the therapeutic use of propofol, a phenol-derived pharmaceutical.
Untreated dermal exposure to phenol may result in partial or full-thickness chemical burns or necrotic soft tissue damage. The systemic complications of severe phenol toxicity are myriad. Mental status depression or seizures may result in airway compromise and respiratory failure. Acute respiratory distress syndrome (ARDS) may necessitate mechanical ventilation. Ventricular arrhythmias and/or cardiovascular collapse may occur. Acute kidney injury requiring dialysis may result from extensive rhabdomyolysis or hemoglobinuria due to intravascular hemolysis. Reports also exist of acute hepatotoxicity and methemoglobinemia.
Patients with severe phenol poisoning will require an interprofessional approach. Depending on presentation and complications, this may include team members from nursing, critical care medicine, burn surgery, gastroenterology, hepatology, nephrology, medical toxicology, or cardiology. Triage nurses should be vigilant for exposures and expedite decontamination. These patients may require extensive nursing support for a prolonged period in the hospital, and will likely require additional periods of rehabilitation following hospitalization. Toxicology pharmacists often are instrumental in selecting appropriate materials for decontamination and post-exposure medications. Wound care physicians and nurses may be needed. A close interprofessional dialogue will be necessary to ensure all team members understand treatment goals. With this team approach, most patients should be expected to make a near-full recovery. [Level 5]
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