Methemoglobinemia laboratory findings: Difference between revisions
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'''ABG Analysis''' | '''ABG Analysis''' | ||
*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>{{ | *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> | ||
Occupational methaemoglobinaemia. Mechanisms of production, features, diagnosis and management including the use of methylene blue. | |||
'''Co-oximetry''' | '''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>{{ Anesth Analg | *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''' | '''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>{{ Conf Proc IEEE Eng Med Biol Soc | *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. | *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== | ||
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Template:Aksiniya K. Stevasarova, M.D.
Overview
Methemoglobinemia can be diagnosed with several laboratory findings.
Laboratory Findings
ABG Analysis
- 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.[1] [2] [3]
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.[4]
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. [5]
- 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
- ↑ 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.
- ↑ 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.
- ↑ 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.
- ↑ Feiner JR, Bickler PE, Mannheimer PD (2010). "Accuracy of methemoglobin detection by pulse CO-oximetry during hypoxia". Anesth Analg. 111 (1): 143–8. doi:10.1213/ANE.0b013e3181c91bb6. PMID 20007731.
- ↑ Van Leeuwen SR, Baranoski GVG, Kimmel BW (2017). "Three-wavelength method for the optical differentiation of methemoglobin and sulfhemoglobin in oxygenated blood". Conf Proc IEEE Eng Med Biol Soc. 2017: 4570–4573. doi:10.1109/EMBC.2017.8037873. PMID 29060914.