![]() ![]() Administration of methylene blue will completely skew readings and measurements of pulse oximeters, CO-Oximeters, and many lab instruments for at least 30 minutes. Pediatric dosing (recommended only for children over 6 years old) is 1 milligram per kilo given intravenously over 5 minutes. An additional dose of 1 milligram per kilo can be given at 30 minutes if improvement is not evident. Improvement is typically seen within 30 minutes. Treatment for methemoglobinemia is intravenous methylene blue dosed at 1 to 2 milligrams per kilogram of patient weight given over 5 minutes. Unlike CO poisoned patients, MET poisoning typically results in cyanosis at levels above 15 percent. Methemoglobin is continuously produced and eliminated in the body, and normal levels should not exceed 2 – 3 percent. Untreated, methemoglobin has a half life (time for half the MET to be eliminated from the body) of roughly 55 minutes. Treatment is typically reserved for symptomatic patients with MET levels above 30 percent. Assessment of methemoglobinemia is by percentage of hemoglobin found in the ferric state. Symptoms in such cases are more likely related to methemoglobinemia than viral illness. Following an endoscopic procedure, patients may mistakenly believe they contracted a cold or flu virus while in the procedure lab. Methemoglobinemia can also occur as an inherited condition.Īssessment of methemoglobinemia Like CO, the signs and symptoms of MET poisoning are vague and appear flu-like. The gastrointestinal tract of newborns may promote growth of gram negative organisms that induce MET poisoning usually associated with prolonged (> 7 days) infantile diarrhea. Other acquired causes of MET poisoning include lidocaine and nitrates such as nitroglycerine, nitric oxide, or water sources contaminated by runoff containing nitrogen based fertilizers. Absorption of benzocaine-containing sprays through mucous membranes or skin during intubations, endoscopies, bronchoscopies, and other procedures can induce significant MET poisoning. While dapsone use is on the rise in the United States (for prevention of pneumocystis pneumonia in transplant patients on immune suppressants), the greatest cause of MET poisoning is benzocaine, a topical anesthetic agent used for numbing sensitive areas of the body. ![]() Worldwide, the leading cause of MET poisoning is the anti-malaria drug dapsone. Most cases are caused by oxidizing drugs or chemicals. Unlike CO poisoning, methemoglobinemia is relatively uncommon outside of medical settings. The result is significant oxygen deficiency (hypoxia). METHb behaves in much the same manner as carboxyhemoglobin: it cannot carry oxygen and causes oxygen already bound to blood cells not to release itself into the body. Methemoglobin is formed when iron on the hemoglobin molecule is converted from a ferrous to a ferric state through a chemical reaction known as oxidation. While many protocols exist for prehospital use and interpretation of CO levels, none have been published for prehospital evaluation of methemoglobin (METHb) levels. CO-Oximeters are pulse oximeters that utilize multiple wavelengths of light to detect not only oxygen saturated blood cells (oxyhemoglobin) but also carbon monoxide saturated blood cells (carboxyhemoglobin) and blood cells that have been chemically converted to methemoglobin. Two technologies currently exist for field measurement of CO in people: CO-Oximetry and exhaled CO breath monitors. Prehospital providers using non-invasive CO screening devices are better prepared to assess and treat CO poisoned patients who might otherwise be missed. With increased awareness and availability of devices to measure CO in patients, the challenges of detecting CO poisoning should begin to decline. CO is the leading cause of poisoning deaths in every industrialized nation.Īnd while exact mechanisms are poorly understood, long term effects in survivors of CO poisoning include up to triple the incidence of cardiovascular events and deaths as well as disabling neurologic conditions. Invisible and odorless, CO fails to produce reliable signs or symptoms in poisoned patients that might alert health care providers or even patients themselves of significant poisoning. The detection of carbon monoxide poisoning is becoming increasingly important to prehospital providers. Jake Larrabee displays a RAD-57 in February after his department secured a grant for the devices. AP Photo/Toby Talbot Montpelier, Vt., Lt. ![]()
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