How should dehydration be managed in patients with varying severity and underlying health conditions?

Management of Dehydration

For mild to moderate dehydration, oral rehydration solution (ORS) with reduced osmolarity is the first-line treatment across all age groups, reserving intravenous fluids only for severe dehydration, inability to tolerate oral intake, or ORS failure. 1, 2

Initial Assessment by Severity

Mild to Moderate Dehydration

• Administer reduced osmolarity ORS at 100 mL/kg over 2-4 hours as primary therapy. 1
• ORS should contain 50-90 mEq/L of sodium for optimal electrolyte replacement. 1
• Reassess hydration status after 2-4 hours; if dehydration persists, reestimate the deficit and continue ORS. 1, 2
• In older adults with mild dehydration who appear well, encourage increased fluid intake with preferred beverages. 2

Severe Dehydration (≥10% fluid deficit)

• Immediately initiate IV resuscitation with isotonic crystalloid boluses of 20 mL/kg (lactated Ringer's or normal saline) until pulse, perfusion, and mental status normalize. 3, 2
• In malnourished infants, use smaller-volume frequent boluses of 10 mL/kg due to reduced cardiac capacity. 3
• Once consciousness returns and oral intake is tolerated, transition to ORS to replace remaining deficit. 3

Specific Clinical Scenarios

Volume Depletion from Blood Loss (Older Adults)

• Assess using postural pulse change ≥30 beats per minute from lying to standing, or severe postural dizziness preventing standing (97% sensitive, 98% specific for blood loss ≥630 mL). 4
• Administer isotonic fluids orally, nasogastrically, subcutaneously, or intravenously. 4

Volume Depletion from Vomiting/Diarrhea (Older Adults)

• Diagnose moderate to severe dehydration when ≥4 of these 7 signs are present: confusion, non-fluent speech, extremity weakness, dry mucous membranes, dry tongue, furrowed tongue, sunken eyes. 4, 2
• Treat with isotonic fluids via oral, nasogastric, subcutaneous, or intravenous routes. 4
• Measured serum osmolality >300 mOsm/kg confirms dehydration in older adults. 2

Geriatric Patients Who Appear Unwell

• Offer subcutaneous or intravenous fluids in parallel with oral intake. 2
• Subcutaneous dextrose infusions are effective with similar adverse effect rates as IV infusion. 2
• Parenteral hydration should be considered medical treatment rather than basic care, with careful benefit-risk assessment. 4

When IV Fluids ARE Indicated for Moderate Dehydration

Reserve IV fluids for moderate dehydration only when specific criteria are met: 1

• Patient cannot tolerate oral intake 1
• Failure of ORS therapy 1
• Presence of ileus 1
• Ketonemia requiring initial IV hydration to enable oral tolerance 1

Use isotonic crystalloid solutions (lactated Ringer's or normal saline) at appropriate rates to correct the estimated 6-9% fluid deficit. 1

Transition and Maintenance Strategy

Switching from IV to Oral

• Transition to ORS as soon as clinical improvement occurs and the patient can tolerate oral intake. 1, 3
• Continue ORS until clinical dehydration is fully corrected. 1
• Replace ongoing stool losses with ORS throughout treatment (approximately 10 mL/kg per watery stool, 2 mL/kg per vomiting episode). 3, 2

Ongoing Management

• Breastfed infants should continue nursing throughout illness. 3, 2
• Resume age-appropriate diet during or immediately after rehydration. 2
• Monitor pulse, perfusion, and mental status frequently during rehydration. 1

Critical Pitfalls to Avoid

Common Errors

• Avoid automatic use of IV fluids for moderate dehydration—this represents overtreatment when ORS is effective in most cases. 1
• Do not use apple juice, Gatorade, or commercial soft drinks for rehydration due to inappropriate electrolyte composition. 3
• Avoid delaying IV access attempts in severe dehydration, as this is a medical emergency. 3

Pediatric-Specific Warnings

• Loperamide is contraindicated in children <2 years due to risks of respiratory depression and serious cardiac adverse reactions. 5
• Dehydration in children <6 years increases variability of response to medications. 5
• Use nasogastric ORS at 15 mL/kg/hour for infants who cannot tolerate or refuse adequate oral intake. 2

Drug-Related Considerations

• Fluid and electrolyte replacement is essential in diarrheal illness and does not preclude the need for appropriate therapy even when antidiarrheal agents are used. 5
• Avoid loperamide in patients with electrolyte abnormalities or elderly patients with cardiac risk factors. 5

Red Flags Requiring Immediate Medical Attention

• Inability to keep down any fluids for >24 hours 2
• Severe postural dizziness preventing standing 4, 2
• Confusion or altered mental status 4, 2
• Persistent high fever 2
• Frank blood in vomit or stool 2
• Severe abdominal pain or distention 2