1) Treatment of mild to moderate toxicity consists of predominantly symptomatic and supportive care. Patients with mild hypotension should be treated with IV fluid hydration.
B) MANAGEMENT OF SEVERE TOXICITY
1) Patients who develop severe hypotension should be treated first with aggressive IV fluid hydration. Vasopressors should be used with caution as they intensify the arteriolar constriction that is generated by spontaneous reflexes in the nitrite-poisoned patient, thereby further compromising tissue blood flow. METHEMOGLOBINEMIA: Symptomatic patients should be treated with methylene blue. Rarely, pediatric patients with severe methemoglobinemia not responsive to methylene blue therapy may require exchange transfusion; patients may be temporized while awaiting transfusion with hyperbaric oxygen therapy. SEIZURES: Treat seizures with benzodiazepines; add barbiturates if seizures persist.
C) DECONTAMINATION
1) PREHOSPITAL: Prehospital gastrointestinal decontamination is generally not recommended because of the potential for CNS depression or persistent seizures and subsequent aspiration.
2) HOSPITAL: Gastrointestinal decontamination with single-dose activated charcoal may be considered in patients with a recent (within 1 hour) potentially life-threatening ingestion of sodium nitrite who are awake and able to protect their airway.
D) AIRWAY MANAGEMENTS
1) Patients with nitrite toxicity may require intubation for respiratory failure associated with altered mental status due to hypotension or functional hypoxia due to methemoglobinemia.
E) ANTIDOTE
1) There is no specific antidote for treatment of nitrite toxicity. However, patients who develop significant methemoglobinemia (symptomatic patients or patients with a methemoglobin level of greater than 30%) should be treated with methylene blue. Contraindications to treatment with methylene blue include known G-6-PD deficiency (may cause hemolysis), known hypersensitivity to methylene blue, and methemoglobin reductase deficiency.
F) METHEMOGLOBINEMIA
1) Initiate oxygen therapy. Treat with methylene blue if patient is symptomatic (usually at methemoglobin concentrations greater than 20% to 30% or at lower concentrations in patients with anemia, underlying pulmonary or cardiovascular disease). METHYLENE BLUE: INITIAL DOSE/ADULT OR CHILD: 1 mg/kg IV over 5 to 30 minutes; a repeat dose of up to 1 mg/kg may be given 1 hour after the first dose if methemoglobin levels remain greater than 30% or if signs and symptoms persist. NOTE: Methylene blue is available as follows: 50 mg/10 mL (5 mg/mL or 0.5% solution) single-dose ampules and 10 mg/1 mL (1% solution) vials. Additional doses may sometimes be required. Improvement is usually noted shortly after administration if diagnosis is correct. Consider other diagnoses or treatment options if no improvement has been observed after several doses. If intravenous access cannot be established, methylene blue may also be given by intraosseous infusion. Methylene blue should not be given by subcutaneous or intrathecal injection. NEONATES: DOSE: 0.3 to 1 mg/kg.
G) ENHANCED ELIMINATION
1) Hemodialysis is typically not useful for treatment of nitrite toxicity. Exchange transfusion may be considered in severely symptomatic patients, especially neonatal and pediatric patients, if the methemoglobinemia is not responsive to methylene blue therapy. It may also be useful in patients with known G-6-PD deficiency or NADPH-dependent methemoglobin reductase deficiencies. Exchange transfusions are of limited applicability in adults due to the inherent risks of large blood volumes required in adults. Although there is limited data in humans, hyperbaric oxygen (HBO) may be considered as a supportive measure while preparations for exchange transfusion are being made. HBO may provide sufficient oxygen to maintain life with dissolved oxygen in blood, and temporarily obviates the need for functional hemoglobin.
H) PATIENT DISPOSITION
1) OBSERVATION CRITERIA: Patients with deliberate or significant exposure should be sent to a healthcare facility for evaluation, treatment, and observation. Patients who are asymptomatic with normal methemoglobin concentrations can be discharged after 6 hours of observation.
2) ADMISSION CRITERIA: Patients who develop significant hypotension, or signs and symptoms of methemoglobinemia should be admitted to an intensive care unit.
3) CONSULT CRITERIA: Contact a local poison center for a toxicology consult for any patient with suspected symptomatic nitrite toxicity.
I) PITFALLS
1) The arterial pO2 is usually normal despite significant methemoglobinemia. Pulse oximetry may overestimate oxygen saturation in patients with significant methemoglobinemia and should not be used to reflect arterial oxygen content or tissue oxygen delivery. Ongoing absorption can lead to recurrent methemoglobinemia.
J) PHARMACOKINETICS
1) Simple aliphatic nitrites such as ethyl nitrite, isobutyl nitrite, and amyl nitrite are volatile liquids readily absorbed through the lungs. Sodium nitrite is readily absorbed through the GI tract after ingestion, and is commonly given medically intravenously. Approximately 60% of nitrite ions are metabolized, with ammonia as one of the end products; 40% of nitrite is excreted unchanged in the urine.
K) DIFFERENTIAL DIAGNOSIS
1) The differential for nitrite toxicity includes other causes of vasodilatory hypotension, other causes of methemoglobinemia, and in the setting of sodium nitrite treatment for cyanide poisoning, includes the underlying cyanide toxicity.
0.4.3 INHALATION EXPOSURE
A) Move patient to fresh air. Monitor for respiratory distress. Administer oxygen and assist ventilation as required.
0.4.4 EYE EXPOSURE
A) DECONTAMINATION: Remove contact lenses and irrigate exposed eyes with copious amounts of room temperature 0.9% saline or water for at least 15 minutes. If irritation, pain, swelling, lacrimation, or photophobia persist after 15 minutes of irrigation, the patient should be seen in a healthcare facility.
0.4.5 DERMAL EXPOSURE
A) OVERVIEW
1) DECONTAMINATION: Remove contaminated clothing and jewelry and place them in plastic bags. Wash exposed areas with soap and water for 10 to 15 minutes with gentle sponging to avoid skin breakdown. A physician may need to examine the area if irritation or pain persists (Burgess et al, 1999).
2) Some chemicals can produce systemic poisoning by absorption through intact skin. Carefully observe patients with dermal exposure for the development of any systemic signs or symptoms and administer symptomatic treatment as necessary.
Rumack BH POISINDEX(R) Information System Micromedex, Inc., Englewood, CO, 2017; CCIS Volume 172, edition expires May, 2017. Hall AH & Rumack BH (Eds): TOMES(R) Information System Micromedex, Inc., Englewood, CO, 2017; CCIS Volume 172, edition expires May, 2017.
