What is the recommended initial management of parenteral diarrhoea, including fluid resuscitation, laboratory evaluation, antimicrobial therapy, and adjunctive treatments for adults and children?

Management of Parenteral Diarrhea

I believe you are asking about "parenterally-treated diarrhea" (diarrhea requiring IV fluids), not "parenteral diarrhea" which is not a standard medical term. The cornerstone of management is rapid fluid resuscitation with oral rehydration solution (ORS) for mild-to-moderate dehydration, reserving intravenous fluids for severe cases, while avoiding empiric antibiotics in most situations.

Initial Assessment and Triage

Assess hydration status immediately to determine treatment pathway:

• Mild dehydration (3-5% fluid deficit): Slightly dry mucous membranes, increased thirst, normal vital signs 1
• Moderate dehydration (6-9% fluid deficit): Sunken eyes, decreased skin turgor (tenting when pinched), dry mucous membranes, tachycardia, reduced urine output 1
• Severe dehydration (≥10% fluid deficit): Altered mental status, weak or absent pulse, prolonged capillary refill (>2 seconds), cool poorly perfused extremities, severe lethargy, prolonged skin tenting 1

Obtain accurate body weight and auscultate for bowel sounds before initiating therapy 1. Visual stool examination confirms consistency and presence of blood or mucus 1.

Fluid Resuscitation Protocol

Mild-to-Moderate Dehydration

Reduced osmolarity oral rehydration solution (ORS) is first-line therapy for all patients who can tolerate oral intake 1:

• Mild dehydration: Administer 50 mL/kg ORS over 2-4 hours 1
• Moderate dehydration: Administer 100 mL/kg ORS over 2-4 hours 1
• Adolescents and adults (≥30 kg): Give 2-4 L ORS over 3-4 hours 1

Start with small volumes (one teaspoon) using a syringe or medicine dropper, gradually increasing as tolerated 1. Reassess hydration status after 2-4 hours 1, 2.

If oral intake fails: Nasogastric administration of ORS may be used in patients with moderate dehydration who cannot drink adequately, or children with normal mental status who are too weak or refuse to drink 1, 2.

Severe Dehydration

Isotonic intravenous fluids (lactated Ringer's or normal saline) must be started immediately 1:

• Children, adolescents, and adults: Administer 20 mL/kg boluses until pulse, perfusion, and mental status normalize 1
• Malnourished infants: Use smaller-volume frequent boluses of 10 mL/kg due to reduced cardiac output capacity 1
• Continue IV therapy until clinical indicators stabilize, then transition to ORS to replace remaining fluid deficit 1, 2

In patients with ketonemia, an initial IV fluid bolus may be required before oral rehydration can be tolerated 1, 2.

Maintenance and Ongoing Loss Replacement

After rehydration, replace ongoing losses with ORS until symptoms resolve 1:

• Infants/children <10 kg: 60-120 mL ORS per diarrheal stool or vomiting episode (up to ~500 mL/day) 1
• Children >10 kg: 120-240 mL ORS per diarrheal stool or vomiting episode (up to ~1 L/day) 1
• Adolescents/adults: Ad libitum ORS up to ~2 L/day 1

Laboratory Evaluation

Routine laboratory studies are rarely needed 1. Consider serum electrolytes only when clinical signs suggest abnormal sodium or potassium concentrations 1.

Stool cultures are indicated for:

• Bloody diarrhea (dysentery) 1
• Not routinely needed for typical acute watery diarrhea in immunocompetent patients 1

Antimicrobial Therapy Decision Algorithm

Empiric antibiotics are NOT recommended for most patients with acute watery diarrhea without recent international travel 1, 3.

When to AVOID Antibiotics

Never use antimicrobials for Shiga toxin-producing E. coli (STEC O157 or other Shiga toxin 2 producers)—they increase hemolytic uremic syndrome risk by up to 50% 1, 2, 4.

Avoid empiric treatment in persistent watery diarrhea lasting ≥14 days 1, 3.

Exceptions: Consider Empiric Antibiotics ONLY When

• Immunocompromised patients with severe illness 1, 3
• Ill-appearing infants <3 months when bacterial infection suspected 2, 3
• Bloody diarrhea with fever, abdominal pain, and tenesmus suggesting shigellosis 2, 4
• Recent international travelers with fever ≥38.5°C or signs of sepsis 2, 4
• Clinical sepsis features with suspected enteric fever 2

Modify or discontinue antimicrobials once a specific pathogen is identified 1.

Nutritional Management

Resume age-appropriate normal diet immediately during or after rehydration—do not withhold food 1, 2, 3:

• Early refeeding prevents malnutrition and may reduce stool output 2
• Continue breastfeeding throughout the diarrheal episode in infants 1, 2, 3
• Previously lactose-containing formula can be tolerated in most instances 1

Zinc supplementation: In children 6 months to 5 years in zinc-deficient regions or with malnutrition, give 10-20 mg daily for 10-14 days 2, 3.

Adjunctive Treatments

Antimotility Agents

Loperamide is absolutely contraindicated in children <18 years with acute diarrhea 1, 2, 4, 3.

In immunocompetent adults with acute watery diarrhea, loperamide may be used ONLY after adequate hydration 1, 2, 3. Avoid loperamide in any patient with bloody diarrhea, fever, or suspected inflammatory diarrhea due to toxic megacolon risk 1, 2, 4.

Antiemetics

Ondansetron may be given to children >4 years and adolescents with vomiting to facilitate ORS tolerance (dose: 0.15-0.2 mg/kg oral, maximum 4 mg) 1, 2, 4, 3.

Probiotics

Probiotic preparations may be offered to immunocompetent adults and children to reduce symptom severity and duration of infectious or antibiotic-associated diarrhea 1, 2, 4, 3.

Common Pitfalls and Caveats

Do not use popular beverages (apple juice, Gatorade, commercial soft drinks) for rehydration—they lack appropriate electrolyte composition 1.

Asymptomatic contacts should NOT receive empiric or preventive antimicrobial therapy—advise appropriate hand hygiene and infection prevention measures instead 1, 3.

Hospital admission is indicated for patients with toxic appearance or altered mental status 2.