From the Research
Dehydration can indeed cause a mildly elevated Mean Corpuscular Hemoglobin (MCH) due to the hemoconcentration effect, where the concentration of hemoglobin within each red blood cell appears to increase as plasma volume decreases. This phenomenon occurs because the number of red blood cells remains constant while the plasma volume decreases, leading to an artificially increased ratio of hemoglobin to red blood cell count, which is used to calculate MCH 1.
When a person becomes dehydrated, the body loses water and electrolytes, causing a decrease in plasma volume. As a result, the red blood cells become more concentrated, leading to an increase in the MCH value. This is typically a temporary change that resolves once proper hydration is restored. To address this, adequate fluid intake should be maintained, especially during hot weather, illness with fever, or after significant fluid losses. For adults, this generally means consuming 2-3 liters of water daily, with increased amounts during illness or excessive sweating.
The complete blood count (CBC) is a commonly ordered laboratory test that provides information about the production of all blood cells, including red blood cells, and identifies the patient's oxygen-carrying capacity through the evaluation of red blood cell indices, hemoglobin, and hematocrit 2, 3. The MCH is an important component of the CBC, and its elevation can be caused by various factors, including dehydration. If dehydration is suspected as the cause of elevated MCH, rehydration and repeat testing after achieving normal hydration status would be appropriate to determine if the MCH abnormality persists.
It is essential to note that the diagnosis of dehydration requires an appraisal of the patient and laboratory testing, clinical assessment, and knowledge of the patient's history 4. In clinical practice, dehydration is rarely due to neglect from formal or informal caregivers but rather results from a combination of physiological and disease processes. Therefore, it is crucial to maintain adequate fluid intake and monitor patients for signs of dehydration, especially in high-risk individuals.
In terms of management, subcutaneous infusion of fluids (hypodermoclysis) can provide a better opportunity to treat mild to moderate dehydration in certain settings 4. However, the primary approach to addressing dehydration-induced elevated MCH is to ensure proper hydration and monitor the patient's condition closely. By prioritizing hydration and monitoring, healthcare providers can effectively manage dehydration and its effects on MCH values, ultimately improving patient outcomes.