What are the initial laboratory tests and treatment for suspected hemoconcentration?

Initial Laboratory Tests and Treatment for Suspected Hemoconcentration

For suspected hemoconcentration, the initial laboratory evaluation should include complete blood count, urinalysis, serum electrolytes (including calcium and magnesium), blood urea nitrogen, serum creatinine, fasting blood glucose, lipid profile, liver function tests, and thyroid-stimulating hormone. 1

Understanding Hemoconcentration

Hemoconcentration refers to an increase in the concentration of blood components due to a reduction in plasma volume. This condition can be identified through increases in:

• Hematocrit
• Hemoglobin
• Serum total protein
• Albumin

Initial Laboratory Assessment

The following tests should be ordered when hemoconcentration is suspected:

1. Complete blood count (CBC)

   • Elevated hemoglobin and hematocrit are key indicators of hemoconcentration 2
   • Note that normal hemoglobin/hematocrit values may still represent relative hemoconcentration in malnourished patients 3

2. Basic metabolic panel

   • Serum electrolytes (including calcium and magnesium)
   • Blood urea nitrogen (BUN)
   • Serum creatinine
   • Elevated BUN/creatinine ratio >25 suggests plasma volume depletion 3

3. Additional blood tests

   • Serum total protein and albumin (elevated in hemoconcentration) 4, 5
   • Fasting blood glucose
   • Liver function tests
   • Thyroid-stimulating hormone

4. Urinalysis

   • To assess hydration status and rule out other causes

5. Volume status assessment

   • Measurement of weight
   • Orthostatic blood pressure changes 1

Diagnostic Considerations

When interpreting laboratory results in suspected hemoconcentration:

• Evaluate the BUN/creatinine ratio - a ratio >25 suggests hypovolemia 3
• Look for discordance between laboratory values and clinical assessment of volume status 2
• Consider that hemoconcentration may mask underlying anemia in malnourished patients 3
• Serial measurements are more valuable than single readings to detect trends 5

Initial Treatment Approach

Treatment should be directed at the underlying cause of hemoconcentration:

1. Volume repletion

   • Isotonic saline (0.9% NaCl) infusion at 15-20 ml/kg body weight/hour during the first hour in the absence of cardiac compromise 1
   • Subsequent fluid choice depends on electrolyte status and underlying condition

2. Monitoring response

   • Serial assessment of hemoconcentration parameters (hemoglobin, hematocrit, total protein, albumin)
   • Monitor vital signs, including orthostatic measurements
   • Track weight changes
   • Reassess electrolytes and renal function

3. Addressing underlying causes

   • If heart failure-related: appropriate heart failure therapy 1
   • If dehydration-related: ongoing fluid resuscitation with electrolyte correction
   • If medication-induced: review and adjust medications as needed

Special Considerations

• Heart failure patients: Hemoconcentration during treatment may actually indicate successful decongestion and be associated with better outcomes, even if accompanied by mild worsening renal function 5

• Malnourished patients: Standard hemoconcentration markers may appear normal despite significant plasma volume depletion 3

• Severe cases: More intensive monitoring may be required, including central venous pressure measurement in appropriate clinical settings 1

By systematically assessing these laboratory parameters and implementing appropriate fluid management, clinicians can effectively diagnose and treat hemoconcentration while addressing its underlying causes.