Methemoglobinemia: Cyanosis and Street Methamphetamines

J Am Board Fam Pract: first published as 10.3122/jabfm.10.2.137 on 1 March 1997. Downloaded from BRIEF REPORTS Methemoglobinemia: Cyanosis and Street Methamphetamines John D. Verzosa, MD Methemoglobin is a type of hemoglobin in which and she had not gotten much sleep during the last the ferrous ion has been oxidized to the ferric couple of days. state. It is therefore incapable of combining with Her medical history was notable only for mild or transporting the oxygen molecule, which is re asthma since childhood, and she denied any placed by a hydroxyl radical. Methemoglobin breathing difficulties for the past several days. emia can be acquired or inherited. Most cases are She was a mother of two boys, worked as a secre acquired and are primarily due to exposure to cer tary, and lived with her husband of several years. tain drugs and chemicals, such as nitrates, nitrites, She denied taking any medications (over-the quinones, and chlorates. Inherited methemoglo counter or prescription) or street drugs. binemia can result from a structural abnormality Upon initial examination, although she was of the globin chains, or it can occur as a result of a . awake and alert and answered questions appropri red blood cell enzyme defect in which the methe ately, she appeared dyspneic and slightly agitated. moglobin formed cannot be converted back to Her temperature, pulse, and blood pressure were the reduced form of hemoglobin. Methemoglo normal, but her respirations were 56/min, and a bin is normally present in the blood in concentra pulse oximetry reading was 88 percent on room tions of 1 to 2 percent and its formation is re air. Her lungs were clear by auscultation, and she versible. I I came across a particularly interesting had good air exchange and appropriate thoracic case of methemoglobinemia in which the patient expansion. There was no tactile fremitus or un had acute cyanosis. usual response to percussion. Findings on a heart examination were normal except for a slight Case Report tachycardia. Her fingers were cyanotic in the nail A 31-year-old woman had brought her son, who beds, and she had perioral cyanosis. There were http://www.jabfm.org/ had nausea and vomiting, to the After-hours Ur no clubbing changes on her qistal digits. gent Care clinic, where they were triaged to the \Vhile she was being examined, the patient's urgent care section. \Vhile she was sitting in the pulse oximetry readings were gradually decreas waiting room with her son and her husband, the ing. She was given a 100 percent oxygen nonre husband noticed that his wife was looking weak breather mask, but her readings continued to fall and saw that her fingernails and lips were turning dramatically. She was told she needed to be in on 25 September 2021 by guest. Protected copyright. blue. The husband called a nurse to look at his tubated for full oxygen support, to which she wife. Immediately noticing the cyanosis, the agreed. Immediately after she was intubated, I nurse brought the patient to the emergency de was asked to help care for the patient as she was partment across the hall, where she was seen by being admitted into the hospital. the physician. The patient denied any concerns at Her arterial blood gases before intubation were the time except for feeling weak and almost faint pH 7.44, pC02 26 mmHg, and p02 109 mmHg, ing while registering her son with the clinic upon and her oxygen saturation was 52 percent. The arrival. She thought it was just because it was late, measured methemoglobin was 50.6 percent. A re peat blood gas measurement was obtained after intubation and was pH 7.45, pC02 24 mmHg, Submitted, revised, 1 October 1996. and p02 321 mmHg, with 65 percent oxygen sat From the Kaiser Fontana Residency Program, Fontana, Calif. uration, and the methemoglobin was still elevated Address reprint request to John D. Verzosa, MD, Kaiser Fontana Family Medicine Residency, 9985 Sierra Ave, Fontana, CA at 40.3 percent. \Vhen the patient had her blood 92335. drawn for both the arterial blood and peripheral Methemoglobinemia 137 J Am Board Fam Pract: first published as 10.3122/jabfm.10.2.137 on 1 March 1997. Downloaded from blood tests, it appeared to have a brown hue. The erin, amyl nitrite, isobutyl nitrite, sodium nitrite, rest of her laboratory studies were normal. She and local anesthetics (benzocaine, prilocaine).3 was given two doses of 120 mg of methylene blue dye 1 hour apart. She was then transferred to the Diagnosis intensive care unit. After methylene blue was A bluish discoloration of the skin and mucous given, her values returned to normal on the next membranes, designated cyanosis, has been recog blood gas analysis, with a methemoglobin of 2.8 nized since antiquity to be a manifestation oflung percent. She was extubated the next morning and or heart disease. Cyanosis resulting from drug ad was not given any more methylene blue dye. The ministration has also been recognized since be remainder of her hospital stay was uneventful. fore 1890.3 Toxic methemoglobinemia occurs Her oxygen saturation was 99 percent on room when various drugs or toxic substances either oxi air. Her husband called her work and apparently dize hemoglobin directly in the circulation or fa nobody else there had been ill. No one in her cilitate its oxidation by molecular oxygen.4 home had experienced similar symptoms as well. Cyanosis that is unresponsive to oxygen ther After the patient was extubated, she admitted apy,S in conjunction with a history of drug or to using some methamphetamines that her chemical exposure, should lead to the considera brother had given her the day before admission. tion of methemoglobinemia. Blood with more She did not know where he obtained the meth than 15 percent methemoglobin appears dark red amphetamines, but he had sold the same product or brown and does not become bright red on ex to other people. She did not know of anyone else posure to oxygen (representing the conversion of having a reaction similar to hers. She had used deoxyhemoglobin to oxyhemoglobin). Methemo methamphetamines occasionally in the last 2 globin levels of up to 20 percent are usually well years, but she believed her brother had used the tolerated in previously healthy adults. As levels same methamphetamines and had not had any approach 40 percent, patients complain of similar effects. She denied abusing any other headache, dizziness, fatigue, and shortness of drugs at any time. She did not smoke cigarettes or breath. Levels of 60 percent produce lethargy, abuse alcohol. stupor, and coma.6 Patients with cardiovascular compromise or anemia will manifest symptoms at Discussion lower methemoglobin levels.7,8 Methemoglobinemia decreases the oxygen-carry The definitive diagnosis is made by arterial ing capacity of blood, because the oxidized iron blood gas analysis with co-oximetry. Usually http://www.jabfm.org/ cannot reversibly bind oxygen. Moreover, when methemoglobin is seen with a normal pOz level one or more iron atoms have been oxidized, the and a low measured oxygen saturation. The pOz conformation of hemoglobin is changed to in reading is unaffected, because it is a measure of crease the oxygen affinity of the remaining fer dissolved oxygen in the plasma. S Similarly, the rous heme groups. In this way methemoglobin calculated oxygen saturation is expected to be emia exerts a dual effect in impairing the supply normal, as it is derived from the pOz. Because on 25 September 2021 by guest. Protected copyright. of oxygen to tissues.Z-4 pulse oximetry is widely used in emergency de partments, its lack of usefulness in diagnosing Toxic Metbemogloblnemill methemoglobinemia is noteworthy. Pulse oxime Hemoglobin is continuously oxidized in vivo from ters overestimate the oxygen saturation in the the ferrous to the ferric state. The rate of such ox presence of methemoglobin. They also show a di idation is accelerated by many drugs and toxic minished response to a change in oxygen satura chemicals, including sulfonamides, lidocaine and tion when methemoglobin is present.9,IO As a re other aniline derivatives, and nitrates. A great sult, arterial blood gases must be obtained in a number of chemical substances can cause methe patient with cyanosis. moglobinemia. The following are some of the agents that are responsible for clinically serious Lllboratory methemoglobinemia in current clinical practice: With methemoglobinemia, pOz levels are nor phenazopyridine, sulfamethoxazole, dapsone, ani mal, but measured oxygen saturation is reduced. line, paraquat-monolinuron, nitrate, nitroglyc- Laboratories that calculate oxygen saturation 138 JABFP March-April1997 Vol. 10 No.2 J Am Board Fam Pract: first published as 10.3122/jabfm.10.2.137 on 1 March 1997. Downloaded from from p02 levels (rather than directly measure it) and management of less severe cases are accom will report normal oxygen saturation levels.!l In plished by oral methylene blue (60 mg three or some laboratories arterial blood gas is also used to four times a day) or ascorbic acid, 300 to 600 measure the methemoglobin level in percentages, mg/d.1n patients with glucose-6-phosphate defi which should help with the diagnosis.1 2 ciency, metfieylene blue can provoke hemolysis. 16 Methemoglobinemia can be detected with a Upon resolution of the methemoglobinemia simple office test. After placing 1 drop of the pa and the improvement of oxygen saturation, the tient's blood on a piece of filter paper next to a patient should be easily extubated as sedation drop of blood from a normal individual, when wears off. In general, there is no need to give re dry, the methemoglobin-containing blood will peated doses of methylene blue once improve turn a deep chocolate-brown or slate-gray color.

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