Methemoglobinemia laboratory findings: Difference between revisions

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*On routine [[ABG analysis]] the [[partial pressure]] of [[oxygen]] ([[PO2]]) value should in normal reference ranges in patients with [[methemoglobinemia]]. The reason lies in the fact that the [[ABG]] value represents the [[oxygen]] content in the [[plasma]], and not the [[oxygen-carrying capacity of hemoglobin]].<ref name="pmid19082413">{{cite journal| author=do Nascimento TS, Pereira RO, de Mello HL, Costa J| title=Methemoglobinemia: from diagnosis to treatment. | journal=Rev Bras Anestesiol | year= 2008 | volume= 58 | issue= 6 | pages= 651-64 | pmid=19082413 | doi= | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=19082413  }} </ref> <ref name="pmid22024786">{{cite journal| author=Skold A, Cosco DL, Klein R| title=Methemoglobinemia: pathogenesis, diagnosis, and management. | journal=South Med J | year= 2011 | volume= 104 | issue= 11 | pages= 757-61 | pmid=22024786 | doi=10.1097/SMJ.0b013e318232139f | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=22024786  }} </ref> <ref name="pmid14579544">{{cite journal| author=Bradberry SM| title=Occupational methaemoglobinaemia. Mechanisms of production, features, diagnosis and management including the use of methylene blue. | journal=Toxicol Rev | year= 2003 | volume= 22 | issue= 1 | pages= 13-27 | pmid=14579544 | doi= | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=14579544  }} </ref>
*On routine [[ABG analysis]] the [[partial pressure]] of [[oxygen]] ([[PO2]]) value should in normal reference ranges in patients with [[methemoglobinemia]]. The reason lies in the fact that the [[ABG]] value represents the [[oxygen]] content in the [[plasma]], and not the [[oxygen-carrying capacity of hemoglobin]].<ref name="pmid19082413">{{cite journal| author=do Nascimento TS, Pereira RO, de Mello HL, Costa J| title=Methemoglobinemia: from diagnosis to treatment. | journal=Rev Bras Anestesiol | year= 2008 | volume= 58 | issue= 6 | pages= 651-64 | pmid=19082413 | doi= | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=19082413  }} </ref> <ref name="pmid22024786">{{cite journal| author=Skold A, Cosco DL, Klein R| title=Methemoglobinemia: pathogenesis, diagnosis, and management. | journal=South Med J | year= 2011 | volume= 104 | issue= 11 | pages= 757-61 | pmid=22024786 | doi=10.1097/SMJ.0b013e318232139f | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=22024786  }} </ref> <ref name="pmid14579544">{{cite journal| author=Bradberry SM| title=Occupational methaemoglobinaemia. Mechanisms of production, features, diagnosis and management including the use of methylene blue. | journal=Toxicol Rev | year= 2003 | volume= 22 | issue= 1 | pages= 13-27 | pmid=14579544 | doi= | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=14579544  }} </ref>
'''Co-oximetry'''
*The [[co-oximeter]] is the most accurate device to measure [[methemoglobin]]. The newer generation devices can actually differentiate between [[methemoglobin]], [[carboxyhemoglobin]], [[oxyhemoglobin]], [[deoxyhemoglobin]], and also [[sulfhemoglobin]].<ref name="pmid20007731">{{cite journal| author=Feiner JR, Bickler PE, Mannheimer PD| title=Accuracy of methemoglobin detection by pulse CO-oximetry during hypoxia. | journal=Anesth Analg | year= 2010 | volume= 111 | issue= 1 | pages= 143-8 | pmid=20007731 | doi=10.1213/ANE.0b013e3181c91bb6 | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=20007731  }} </ref>
 
'''Pulse oximetry'''
*The [[pulse oximetry]] in [[methemoglobinemia]] patients will always show a value around  85%, regardless of the level of [[MetHb]] in the blood. This is very importan tot know as this value can be misleading especially in patients with very high [[MetHb]] levels. Fortunately new [[multiwavelength pulse oximeters]] have been developed recently and they can detect the levels of [[MetHb]] more accurately. <ref name="pmid29060914">{{cite journal| author=Van Leeuwen SR, Baranoski GVG, Kimmel BW| title=Three-wavelength method for the optical differentiation of methemoglobin and sulfhemoglobin in oxygenated blood. | journal=Conf Proc IEEE Eng Med Biol Soc | year= 2017 | volume= 2017 | issue=  | pages= 4570-4573 | pmid=29060914 | doi=10.1109/EMBC.2017.8037873 | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=29060914  }} </ref>
*In [[methemoglobinemia]] patients we often see the so called “[[saturation gap]]” which can help us diagnose the condition. The gap is calculated by subtracting the [[oxygen]] percentage from the [[ABG analysis]] (typically normal in [[methemoglobinemia]] patients 100%) from the percentage of [[oxygen saturation]] given by the [[pulse oximeter]] (always ~85% in [[methemoglobiemia]] patients). [[Saturaion gap]] more than 5% is significant.


==References==
==References==

Latest revision as of 14:03, 15 August 2018

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Aksiniya Stevasarova, M.D.

Overview

Methemoglobinemia can be diagnosed with several laboratory findings such as ABG analysis, co-oximetry and pulse oximetry.

Laboratory Findings

ABG Analysis

References

  1. do Nascimento TS, Pereira RO, de Mello HL, Costa J (2008). "Methemoglobinemia: from diagnosis to treatment". Rev Bras Anestesiol. 58 (6): 651–64. PMID 19082413.
  2. Skold A, Cosco DL, Klein R (2011). "Methemoglobinemia: pathogenesis, diagnosis, and management". South Med J. 104 (11): 757–61. doi:10.1097/SMJ.0b013e318232139f. PMID 22024786.
  3. Bradberry SM (2003). "Occupational methaemoglobinaemia. Mechanisms of production, features, diagnosis and management including the use of methylene blue". Toxicol Rev. 22 (1): 13–27. PMID 14579544.

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