From the Guidelines
Laboratory tests for dehydration should include serum osmolality, with an action threshold of >300 mOsm/kg to identify low-intake dehydration in older adults, as recommended by the US Panel on Dietary Reference Intakes for Electrolytes and Water 1. When assessing dehydration, it is essential to consider the patient's clinical presentation, including signs such as decreased skin turgor, dry mucous membranes, orthostatic hypotension, and tachycardia.
- A comprehensive metabolic panel (CMP) can help assess electrolyte levels, particularly sodium, potassium, chloride, and bicarbonate, which can be abnormal in dehydration.
- Blood urea nitrogen (BUN) and creatinine are crucial, as the BUN/creatinine ratio often increases above 20:1 in dehydration due to decreased kidney perfusion.
- Complete blood count (CBC) may show increased hematocrit and hemoglobin concentration due to hemoconcentration.
- Urine studies, including urine specific gravity and urine osmolality, can also be valuable in assessing hydration status. However, according to the most recent and highest quality study, serum osmolality is the primary indicator of hydration status, especially in older adults with poor renal function 1. In severe cases, arterial blood gases may be ordered to assess acid-base status, as dehydration can lead to metabolic acidosis, but this should not delay the initiation of treatment, as recommended by the Infectious Diseases Society of America 1.
From the Research
Dehydration Diagnosis
Dehydration can be diagnosed through a combination of clinical observations, laboratory values, and clinician experience 2. The following laboratory tests can be used to diagnose dehydration:
- Blood tests: osmolality and blood urea nitrogen/creatinine
- Urine tests: osmolality and specific gravity Other important information for diagnosing dehydration includes:
- Blood pressure assessment
- Clinical symptoms in the eye: tear production and palpitating pressure
- Clinical symptoms in the mouth: thirst and mucous wetness
Laboratory Values
Laboratory values such as blood urea nitrogen and creatinine can provide important information for diagnosing dehydration 2, 3. These values can reflect renal function and acid-base homeostasis. A basic metabolic panel can also be used to assess electrolyte imbalances, including potassium and chloride levels 3.
Assessment and Monitoring
Maintaining the balance of fluid and electrolytes is crucial to patient care 4. Key monitoring and assessment parameters include:
- Key electrolytes: their function, normal values, signs and symptoms of imbalances, and treatment modalities
- Fluid balance: assessment and monitoring to prevent dehydration and electrolyte imbalances By considering these factors, healthcare professionals can develop a thorough plan of care for patients with dehydration and electrolyte imbalances.