How do I treat a patient with watery diarrhea, dehydration, and metabolic acidosis (bicarbonate level of 16)?

Treatment of Watery Diarrhea with Dehydration and Metabolic Acidosis (Bicarbonate 16)

Begin immediate rehydration with oral rehydration solution (ORS) if the patient can tolerate oral intake and has no altered mental status, shock, or ileus; otherwise, initiate intravenous isotonic fluids (lactated Ringer's or normal saline) until hemodynamically stable, then transition to ORS. 1

Assess Dehydration Severity

Determine the degree of dehydration by examining:

• Skin turgor (prolonged tenting indicates severe dehydration)
• Mucous membranes (dry indicates at least moderate dehydration)
• Mental status (lethargy or altered consciousness indicates severe dehydration)
• Pulse quality and capillary refill (weak pulse and prolonged refill indicate poor perfusion)
• Urine output (oliguria suggests significant volume depletion) 2, 3

Categorize as:

• Mild dehydration: 3-5% fluid deficit, increased thirst, slightly dry mucous membranes
• Moderate dehydration: 6-9% fluid deficit, loss of skin turgor, dry mucous membranes
• Severe dehydration: ≥10% fluid deficit, severe lethargy/altered consciousness, prolonged skin tenting, shock 2, 3

Address the Metabolic Acidosis (Bicarbonate 16)

A bicarbonate of 16 mEq/L indicates moderate metabolic acidosis from bicarbonate losses in stool. 4

The acidosis will correct with adequate fluid resuscitation alone—do not routinely administer intravenous bicarbonate. 1 Studies demonstrate that bicarbonate administration in diarrheal acidosis makes no difference in resolution of acidosis or time to discharge. 1

Exception: In oliguric patients with severe acidosis and renal impairment, consider a physiological dose of bicarbonate only to correct blood pH to 7.25. 5

Rehydration Protocol Based on Severity

For Mild to Moderate Dehydration (Patient Alert, Can Tolerate Oral Intake)

Administer reduced osmolarity ORS (50-90 mEq/L sodium, total osmolarity <250 mmol/L) as first-line therapy: 1, 2, 3

• Mild dehydration (3-5% deficit): Give 50 mL/kg ORS over 2-4 hours
• Moderate dehydration (6-9% deficit): Give 100 mL/kg ORS over 2-4 hours 2, 3

Replace ongoing losses: Give 10 mL/kg ORS for each watery/loose stool. 2, 3, 6

The ORS will correct the acidosis because it contains bicarbonate or citrate base (both are equally effective at correcting acidosis). 7, 8 The sodium citrate in ORS is metabolized to bicarbonate and corrects metabolic acidosis as effectively as sodium bicarbonate-containing solutions. 7

For Severe Dehydration (Shock, Altered Mental Status, or Unable to Tolerate Oral Intake)

This is a medical emergency requiring immediate IV rehydration: 1, 3

1. Administer 20 mL/kg boluses of isotonic IV fluids (lactated Ringer's solution or 0.9% normal saline) rapidly until pulse, perfusion, and mental status normalize. 1, 3

2. Continue IV rehydration until the patient awakens, has no aspiration risk, and has no evidence of ileus. 1

3. Transition to ORS for the remaining fluid deficit once the patient is hemodynamically stable and can tolerate oral intake. 1, 3

4. Monitor serum osmolality changes: Do not exceed 3 mOsm/kg/h change during fluid replacement to avoid complications. 3

Nutritional Management

Resume age-appropriate normal diet immediately after rehydration is complete or during the rehydration process. 1, 2, 3 Early feeding improves nutritional outcomes and is as safe as delayed feeding. 2

• Breastfed infants: Continue nursing on demand throughout the illness 1, 3
• Formula-fed infants: Resume full-strength formula immediately after rehydration 3, 6

Antimicrobial Therapy Decision

Do not give empiric antibiotics for acute watery diarrhea without recent international travel. 1, 2 Empiric antimicrobial therapy is not recommended for suspected viral or non-invasive bacterial watery diarrhea. 1, 2

Exceptions where empiric antibiotics may be considered:

• Immunocompromised patients who are severely ill
• Young infants who appear ill
• Clinical features of sepsis with suspected enteric fever 1

Avoid antibiotics entirely if STEC (Shiga toxin-producing E. coli) is suspected, as they increase risk of hemolytic uremic syndrome. 1

Adjunctive Therapies

Loperamide may be given to immunocompetent adults (2 mg after each unformed stool, maximum 16 mg/day) once adequately hydrated, but avoid if fever or bloody diarrhea develops. 1, 2, 9 Do not use loperamide in children under 18 years of age. 1, 9

Probiotics may be offered to reduce symptom severity and duration in immunocompetent patients. 1, 2

Monitoring During Treatment

• Reassess hydration status every 2-4 hours by checking skin turgor, mucous membranes, mental status, pulse, and urine output 2, 3
• Monitor weight changes to ensure adequate rehydration 2
• Check electrolytes if severe dehydration or if patient has renal/cardiac compromise 3
• Watch for hypokalemia: Potassium losses are common in diarrhea and may require supplementation beyond what ORS provides 4, 5

Critical Pitfalls to Avoid

• Do not use IV bicarbonate routinely—fluid resuscitation alone corrects the acidosis 1
• Do not use antimotility drugs in children or in any patient with fever/bloody diarrhea 1, 2, 9
• Do not delay ORS transition once hemodynamically stable—ORS is as effective as IV therapy for completing rehydration 3, 10
• Do not use soft drinks or sports drinks for rehydration—they have inappropriate osmolality and electrolyte composition 3