Is it appropriate to administer a 500ml Dextrose Normal Saline (DNS) IV bolus with ondansetron to a patient with vomiting and hypotension?

IV Fluid Bolus with Ondansetron for Adolescent with Vomiting

Direct Answer

Yes, administering 500mL DNS (Dextrose Normal Saline) IV bolus with ondansetron to this 15-year-old boy with vomiting and a BP of 100/60 mmHg is appropriate and recommended. This blood pressure is within normal range for an adolescent, and both interventions address the clinical presentation effectively 1.

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Blood Pressure Assessment

The blood pressure of 100/60 mmHg in a 15-year-old does not represent hypotension:

• Hypotension is defined as systolic BP <90 mmHg or a drop of ≥30 mmHg from baseline 1
• This patient's systolic pressure of 100 mmHg is above the hypotension threshold 1
• The clinical context suggests possible volume depletion from vomiting rather than true shock 1

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Fluid Resuscitation Rationale

Indication for IV Fluids

Vomiting resulting in significant fluid losses should trigger fluid replacement therapy 1:

• The patient's vomiting represents volume depletion requiring rehydration 1
• Reduced osmolarity oral rehydration solution (ORS) is first-line for mild to moderate dehydration, but isotonic IV fluids are indicated when oral intake is not tolerated 1
• A 500mL bolus is reasonable for an adolescent with ongoing vomiting 2

Fluid Choice

DNS (Dextrose Normal Saline) is acceptable, though considerations exist:

• Normal saline or lactated Ringer's are preferred crystalloids for volume resuscitation 1, 2
• Dextrose-containing solutions are rapidly extravasated from intravascular to interstitial space, making them less ideal for pure volume expansion 1
• However, for a 500mL bolus in a non-shocked patient, DNS remains clinically appropriate 2

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Ondansetron Administration

Safety and Efficacy

Ondansetron is safe and indicated for this clinical scenario 1:

• Ondansetron may be given to facilitate tolerance of oral rehydration in children >4 years of age and adolescents with acute gastroenteritis associated with vomiting 1
• The drug has a well-established favorable safety profile in adolescents and adults 3, 4
• Ondansetron reduces vomiting and decreases the need for hospitalization 1

Dosing for Adolescents

The recommended dose for a 15-year-old is 4-8 mg IV 1, 5:

• For postoperative nausea/vomiting in patients >40 kg: 4 mg IV undiluted over 2-5 minutes 5
• For chemotherapy-induced nausea: 0.15 mg/kg (maximum 16 mg per dose) diluted and infused over 15 minutes 5
• Dilution is NOT required for postoperative or acute vomiting indications 5

Safety Considerations

Monitor for rare adverse effects:

• Hypersensitivity reactions including anaphylaxis can occur but are rare 5, 6
• QT prolongation occurs in a dose-dependent manner; avoid in congenital long QT syndrome 5
• Extrapyramidal symptoms and seizures have been reported in isolated cases 7
• Ondansetron was associated with decreased 90-day mortality in critically ill patients 8

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Clinical Algorithm

Step 1: Assess Severity

• BP 100/60 mmHg = not hypotensive (no emergency intervention needed) 1
• Vomiting with likely volume depletion = moderate dehydration 1

Step 2: Initiate Treatment

• Start 500mL DNS IV bolus at appropriate rate (can run over 30-60 minutes for non-emergent rehydration) 2
• Administer ondansetron 4 mg IV undiluted over 2-5 minutes 5

Step 3: Monitor Response

• Reassess vital signs after fluid bolus 2
• Monitor for resolution of vomiting after ondansetron 1
• If vomiting persists >4 episodes in 12 hours or patient cannot keep fluids down, escalate care 1

Step 4: Transition to Oral Intake

• Once vomiting controlled, transition to oral rehydration solution 1
• Resume age-appropriate diet as tolerated 1

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Important Caveats

When to Escalate Care

Contact physician or seek higher level of care if 1:

• Vomiting >4 times in 12 hours
• Unable to keep fluids down
• Symptoms persist >72 hours
• Development of altered mental status, severe abdominal pain, or signs of severe dehydration

Antimotility Agents

Do NOT give loperamide or other antimotility drugs to this 15-year-old 1:

• Antimotility drugs should not be given to children <18 years of age with acute diarrhea 1
• These agents can mask progressive ileus 1

Volume Overload Risk

While unlikely with 500mL in an adolescent, monitor for:

• Respiratory distress
• Pulmonary edema (especially if underlying cardiac or renal disease) 1