Assessment of Fluid Deficit
Assessing Volume Depletion
- Evaluate for postural pulse change from lying to standing (≥30 beats per minute) or severe postural dizziness resulting in inability to stand - these are 97% sensitive and 98% specific when blood loss is at least 630 mL 3
- Note that postural hypotension has limited additional predictive value beyond postural pulse changes 3
- Be aware that beta-blockers may affect the sensitivity and specificity of these measurements in older adults 3
- The American Society of Clinical Nutrition recommends assessing fluid deficit through a combination of clinical signs, with specific criteria depending on the cause of volume depletion 1, 2
Assessing Volume Depletion Following Fluid and Salt Loss
- Check for the presence of at least four of the following seven signs, which indicate moderate to severe volume depletion 1, 4:
- Additional signs that may indicate hypovolemia include 1, 5:
Categorizing Fluid Deficits
- Assess severity of dehydration based on percentage of fluid deficit 6:
Treatment Approach
- For mild to moderate volume depletion, administer isotonic fluids orally, nasogastrically, subcutaneously, or intravenously 2, 7
- Treat according to the degree of dehydration 6: