Methemoglobinemia laboratory findings: Difference between revisions
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==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. | |||
'''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. | |||
'''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. | |||
In methemoglobinemia patients we often see the so called “saturation gap” which can help us diagnose the condition. The gap is calculated by the difference between the Oxygen value from the ABG analysis (typically normal in methemoglobinemia patients 100%) and the pulse ox -oxygen saturation (always ~85% in methemoglobiemia patients). Saturaion gap more than 5 % is significant. | |||
==References== | ==References== | ||
Revision as of 11:16, 29 April 2018
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Overview
Congenital (Hereditary) Methemoglobinemia
There are three main congenital conditions that lead to methemoglobinemia:
1. Cytochrome b5 reductase deficiency and pyruvate kinase deficiency
2. G6PD deficiency
3. Presence of abnormal hemoglobin.
Acquired or Acute Methemoglobinemia
Most common cause include different oxidant drugs, toxins or chemicals
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.
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.
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.
In methemoglobinemia patients we often see the so called “saturation gap” which can help us diagnose the condition. The gap is calculated by the difference between the Oxygen value from the ABG analysis (typically normal in methemoglobinemia patients 100%) and the pulse ox -oxygen saturation (always ~85% in methemoglobiemia patients). Saturaion gap more than 5 % is significant.