401:
underlying medical conditions play an important role. For example, a methemoglobin concentration of 1.5 g/dL may represent a percentage of 10% in an otherwise healthy patient with a baseline hemoglobin of 15 mg/dL, whereas the presence of the same concentration of 1.5 g/dL of methemoglobin in an anemic patient with a baseline hemoglobin of 8 g/dL would represent a percentage of 18.75%. The former patient will be left with a functional hemoglobin concentration of 13.5 g/dL and potentially remain asymptomatic while the latter patient with a functional hemoglobin concentration 6.5 g/dL may be severely symptomatic with a methemoglobin of less than 20%.
20:
844:
400:
Methemoglobin is expressed as a concentration or a percentage. Percentage of methemoglobin is calculated by dividing the concentration of methemoglobin by the concentration of total hemoglobin. Percentage of methemoglobin is likely a better indicator of illness severity than overall concentration, as
671:"Drug Safety and Availability - FDA Drug Safety Communication: Reports of a rare, but serious and potentially fatal adverse effect with the use of over-the-counter (OTC) benzocaine gels and liquids applied to the gums or mouth"
95:
Normally one to two percent of a person's hemoglobin is methemoglobin; a higher percentage than this can be genetic or caused by exposure to various chemicals and depending on the level can cause health problems known as
747:
371:
737:
1611:
773:
76:
a trace amount of methemoglobin is normally produced spontaneously, but when present in excess the blood becomes abnormally dark bluish brown. The
870:
550:
Bando, S.; Takano, T.; Yubisui, T.; Shirabe, K.; Takeshita, M.; Nakagawa, A. (2004). "Structure of human erythrocyte NADH-cytochromeb5reductase".
183:
480:
This may be further compounded by the "functional hemoglobin's" decreased ability to release oxygen in the presence of methemoglobin.
680:
930:
489:
492:, and essentially any pathology that impairs the ability to deliver oxygen may worsen the symptoms of methemoglobinemia.
903:
1646:
1631:
769:
675:
794:
Vale, J. A. (2001). "Cyanide
Antidotes: from Amyl Nitrite to Hydroxocobalamin – Which Antidote is Best?".
501:
68:) of normal hemoglobin. Sometimes, it is also referred to as ferrihemoglobin. Methemoglobin cannot bind
923:
867:
193:
276:
374:. The immediate goal of forming this cyanide adduct is to prevent the binding of free cyanide to the
998:
892:
742:
485:
1076:
1020:
611:
Manassaram, D. M.; Backer, L. C.; Messing, R.; Fleming, L. E.; Luke, B.; Monteilh, C. P. (2010).
177:
174:
Pregnant women are considered vulnerable to exposure of high levels of nitrates in drinking water
81:
72:, which means it cannot carry oxygen to tissues. It is bluish chocolate-brown in color. In human
24:
1057:
254:
898:
504:
transit from bright red to dark brown, which is attributed to oxidation of oxy-hemoglobin (HbO
1641:
916:
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1187:
1173:
1159:
796:
624:
383:
188:
8:
1467:
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1003:
888:
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628:
613:"Nitrates in drinking water and methemoglobin levels in pregnancy: A longitudinal study"
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531:
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434:
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347:
105:
97:
500:
Increased levels of methemoglobin are found in blood stains. Upon exiting the body,
320:
in
Kentucky, due to a recessive gene, had blue skin from an excess of methemoglobin.
19:
1337:
1296:
1226:
717:
704:
Dela Cruz, Maricel; Glick, Joshua; Merker, Seth H.; Vearrier, David (11 May 2018).
642:
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705:
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242:
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706:"Survival after severe methemoglobinemia secondary to sodium nitrate ingestion"
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117:
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375:
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125:
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85:
43:
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Children younger than 4 months exposed to various environmental agents
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http://www.plosone.org/article/info:doi/10.1371/journal.pone.0021845
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1347:
1088:
549:
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10–20% metHb - Skin discoloration only (most notably on
100:. A higher level of methemoglobin will tend to cause a
27:, the enzyme that converts methemoglobin to hemoglobin.
854:
Creative
Commons Attribution 4.0 International License
818:
Wilkerson, Richard G.; Nappe, Thomas M. (2019-05-05).
813:
811:
104:
to read closer to 85% regardless of the true level of
88:) is responsible for converting methemoglobin back to
808:
203:Local anesthetic agents, especially prilocaine and
770:"Don't eat that! Toxicities in cats (Proceedings)"
354:to methemoglobin, which allows for the binding of
1623:
124:(meta-: behind, later, subsequent) and the word
817:
924:
793:
389:
931:
917:
1612:disorders of globin and globulin proteins
891:at the U.S. National Library of Medicine
721:
646:
636:
587:"Methemoglobin MeSH Descriptor Data 2021"
116:The word methemoglobin derives from the
18:
163:Common causes of elevated methemoglobin
1624:
767:
473:Greater than 70% metHb - High risk of
912:
904:The Blue people of Troublesome Creek
738:"Genetics Solves Blue-Tinged Mystery"
490:chronic obstructive pulmonary disease
42:) (pronounced "met-hemoglobin") is a
699:
697:
168:Reduced cellular defense mechanisms
584:
578:
338:
13:
14:
1658:
882:
694:
408:Less than 10% metHb - No symptoms
200:Various pharmaceutical compounds
135:is itself derived from the words
842:
552:Acta Crystallographica Section D
508:) to methemoglobin (met-Hb) and
860:
776:from the original on 2015-09-05
750:from the original on 2012-03-18
683:from the original on 2012-04-19
495:
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761:
730:
663:
604:
543:
1:
768:Dowers, Kirsty (2011-08-01).
723:10.1080/24734306.2018.1467532
537:
332:(i.e. acetaminophen, tylenol)
866:Bremmer et al PLoS ONE 2011
676:Food and Drug Administration
111:
7:
515:
316:Some family members of the
10:
1663:
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194:Pyruvate kinase deficiency
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710:Toxicology Communications
564:10.1107/S0907444904020645
350:. It works by converting
346:is administered to treat
893:Medical Subject Headings
486:congestive heart failure
390:Methemoglobin saturation
178:Cytochrome b5 reductase
82:methemoglobin reductase
25:cytochrome b5 reductase
1647:Respiratory physiology
852:is licensed under the
638:10.1186/1476-069X-9-60
151:of hemoglobin being a
28:
370:and the formation of
261:Environmental agents
64:) state, not the Fe (
22:
1632:Cellular respiration
617:Environmental Health
384:cytochrome c oxidase
313:Inherited disorders
189:Hemoglobin M disease
86:a type of diaphorase
60:group is in the Fe (
1468:Glycated hemoglobin
1438:Carbaminohemoglobin
820:"Methemoglobinemia"
629:2010EnvHe...9...60M
873:2014-03-26 at the
522:Blue baby syndrome
372:cyanomethemoglobin
80:-dependent enzyme
29:
16:Type of hemoglobin
1619:
1618:
1570:
1569:
1566:
1565:
1502:
1501:
1433:Carboxyhemoglobin
1421:
1420:
1314:
1313:
1128:
1127:
848:This source from
591:meshb.nlm.nih.gov
558:(11): 1929–1934.
532:Methemoglobinemia
527:Carboxyhemoglobin
396:Methemoglobinemia
348:cyanide poisoning
155:with an embedded
106:oxygen saturation
98:methemoglobinemia
23:The structure of
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413:mucous membranes
339:Therapeutic uses
153:globular protein
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1615:
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1592:Cytochrome P450
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1447:Deoxyhemoglobin
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1254:
1250:
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1211:
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1202:HbE Portland II
1197:
1193:
1183:
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1051:
982:Alpha locus on
951:
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899:MetHb Formation
885:
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875:Wayback Machine
865:
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455:50–70% metHb -
433:30–50% metHb -
418:20–30% metHb -
398:
392:
381:
341:
243:phenazopyridine
184:G6PD deficiency
165:
114:
52:, in which the
47:in the form of
17:
12:
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1494:Erythrocruorin
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1479:
1478:
1476:
1475:
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1464:
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1452:Sulfhemoglobin
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1223:
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1213:
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1191:
1188:HbE Portland I
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883:External links
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824:NCBI Bookshelf
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746:. 2012-02-22.
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102:pulse oximeter
49:metalloprotein
36:methaemoglobin
15:
9:
6:
4:
3:
2:
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1599:Methemalbumin
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1558:Leghemoglobin
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1489:Chlorocruorin
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1473:Methemoglobin
1471:
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1448:
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1443:Oxyhemoglobin
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942:that contain
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905:
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897:
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889:Methemoglobin
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331:
328:Ingestion of
327:
326:
324:
319:
318:Fugate family
315:
314:
312:
308:
305:
303:
299:
296:
294:
291:
289:
288:Chlorobenzene
286:
284:
281:
278:
274:
273:-nitroaniline
272:
267:
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262:
260:
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252:
248:
244:
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236:
235:nitroprusside
232:
231:nitroglycerin
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119:
118:Ancient Greek
109:
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83:
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67:
63:
59:
55:
51:
50:
45:
41:
37:
33:
32:Methemoglobin
26:
21:
1642:Hemoproteins
1609:
1587:Cytochrome b
1549:
1528:Metmyoglobin
1514:
1472:
1319:
1145:development:
1142:
1112:
1095:
1083:
1071:
1056:
1039:
1027:
1015:
993:
981:
948:hemoproteins
862:
847:
835:. Retrieved
823:
801:
795:
789:
778:. Retrieved
763:
752:. Retrieved
741:
732:
713:
709:
685:. Retrieved
674:
665:
620:
616:
606:
594:. Retrieved
590:
585:NIH (1966).
580:
555:
551:
545:
499:
496:Blood stains
479:
451:palpitations
399:
344:Amyl nitrite
342:
277:patient case
270:
255:sulfonamides
211:Amyl nitrite
142:
136:
132:
130:
121:
115:
94:
46:
39:
38:, shortened
35:
31:
30:
1637:Hemoglobins
1535:Neuroglobin
1461:Other human
1174:HbE Gower 2
1160:HbE Gower 1
804:(1): 37–38.
502:bloodstains
465:arrhythmias
430:on exertion
405:1–2% Normal
330:paracetamol
307:Umbellulone
215:chloroquine
1626:Categories
1582:Cytochrome
1540:Cytoglobin
1320:pathology:
1143:stages of
1058:Beta locus
966:Hemoglobin
837:2019-05-10
797:Toxicology
780:2018-11-02
754:2012-03-21
687:2012-04-12
538:References
510:hemichrome
394:See also:
376:cytochrome
352:hemoglobin
247:primaquine
239:phenacetin
205:benzocaine
180:deficiency
133:hemoglobin
126:hemoglobin
90:hemoglobin
44:hemoglobin
34:(British:
1610:see also
1523:Myoglobin
1426:Compounds
1297:HbF/Fetal
1227:HbF/Fetal
1153:Embryonic
1134:Tetramers
716:: 21–23.
623:(1): 60.
447:tachypnea
443:dizziness
439:confusion
382:group in
293:Chromates
264:Aromatic
131:The name
112:Etymology
1482:Nonhuman
974:Subunits
940:Proteins
871:Archived
832:30726002
774:Archived
748:Archived
743:ABC News
681:Archived
657:20946657
572:15502298
516:See also
469:acidosis
461:seizures
424:headache
325:In cats
302:nitrites
298:Nitrates
251:quinones
227:nitrites
223:nitrates
957:Globins
648:2967503
625:Bibcode
435:Fatigue
428:dyspnea
420:Anxiety
368:cations
356:cyanide
219:dapsone
159:group.
149:subunit
147:, each
120:prefix
66:ferrous
56:in the
1550:plant:
1515:human:
1009:pseudo
895:(MeSH)
850:PubMed
830:
655:
645:
596:7 June
570:
512:(HC).
482:Anemia
364:ferric
360:anions
283:Arsine
268:(e.g.
266:amines
144:globin
70:oxygen
62:ferric
1575:Other
1507:Other
1338:Barts
1259:Adult
1220:Fetal
475:death
366:(Fe)
358:(CN)
122:μετα-
74:blood
40:MetHb
1118:HBE1
1106:HBG2
1101:HBG1
1033:HBQ1
1004:HBA2
999:HBA1
944:heme
828:PMID
653:PMID
598:2021
568:PMID
457:Coma
253:and
157:heme
141:and
138:heme
78:NADH
58:heme
54:iron
1404:HbO
1390:HbE
1376:HbC
1362:HbS
1348:HbD
1328:HbH
1280:HbA
1266:HbA
1241:HbA
1089:HBD
1077:HBB
1060:on
1045:HBM
1021:HBZ
802:168
718:doi
643:PMC
633:doi
560:doi
362:by
1628::
1406:(α
1392:(α
1378:(α
1364:(α
1350:(α
1340:(γ
1330:(β
1299:(α
1285:(α
1268:(α
1243:(α
1229:(α
1204:(ζ
1190:(ζ
1176:(α
1162:(ζ
1062:11
984:16
826:.
822:.
810:^
800:.
772:.
740:.
712:.
708:.
696:^
679:.
673:.
651:.
641:.
631:.
619:.
615:.
589:.
566:.
556:60
554:.
488:,
484:,
467:,
463:,
459:,
449:,
445:,
441:,
437:,
426:,
422:,
386:.
275:,
249:,
245:,
241:,
237:,
233:,
229:,
225:,
221:,
217:,
213:,
128:.
108:.
92:.
1445:/
1414:)
1412:2
1410:β
1408:2
1400:)
1398:2
1396:β
1394:2
1386:)
1384:2
1382:β
1380:2
1372:)
1370:2
1368:β
1366:2
1358:)
1356:2
1354:β
1352:2
1344:)
1342:4
1334:)
1332:4
1307:)
1305:2
1303:γ
1301:2
1293:)
1291:2
1289:δ
1287:2
1282:2
1276:)
1274:2
1272:β
1270:2
1251:)
1249:2
1247:β
1245:2
1237:)
1235:2
1233:γ
1231:2
1212:)
1210:2
1208:β
1206:2
1198:)
1196:2
1194:γ
1192:2
1184:)
1182:2
1180:ε
1178:2
1170:)
1168:2
1166:ε
1164:2
1113:ε
1096:γ
1084:δ
1072:β
1064::
1040:μ
1028:θ
1016:ζ
994:α
986::
950:)
946:(
932:e
925:t
918:v
856:.
840:.
783:.
757:.
726:.
720::
714:2
690:.
659:.
635::
627::
621:9
600:.
574:.
562::
506:2
415:)
380:3
378:a
300:/
279:)
271:p
207:.
84:(
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