5.3 Isotonic Fluid Bolus 10–20 mL/kg & Reassessment

AHA PALS Provider Pediatric Advanced Life Support

Track your progress as you read

Finished sections get a check mark.

1 Chapter 1: Course Overview & Exam Logistics

1.1 Current Exam Facts 1.2 Audience, Prerequisites & Study Plan

2 Chapter 2: Systematic Pediatric Assessment

2.1 Pediatric Assessment Triangle (PAT) 2.2 Evaluate–Identify–Intervene Sequence 2.3 Primary Assessment: ABCDE 2.4 Secondary Assessment, SAMPLE & Vitals by Age

3 Chapter 3: Respiratory Distress & Failure

3.1 Respiratory Distress vs Failure 3.2 Recognition & Immediate Intervention Priorities 3.3 Oxygen Delivery & Basic Airway Support

4 Chapter 4: Airway Problems & Ventilation Strategies

4.1 Upper Airway Obstruction 4.2 Lower Airway, Lung Tissue Disease & Disordered Control 4.3 Bag-Mask Ventilation & Advanced Airways During CPR

5 Chapter 5: Shock Fundamentals & Hypovolemia

5.1 Compensated vs Hypotensive (Decompensated) Shock 5.2 Hypovolemic Shock 5.3 Isotonic Fluid Bolus 10–20 mL/kg & Reassessment

6 Chapter 6: Distributive, Cardiogenic & Obstructive Shock

6.1 Distributive & Septic Shock Pathway 6.2 Cardiogenic Shock 6.3 Obstructive Shock

7 Chapter 7: Pediatric BLS & High-Quality CPR

7.1 High-Quality CPR Metrics 7.2 Compression-Ventilation Ratios 7.3 CPR Quality Monitoring: ETCO2 & Diastolic BP

8 Chapter 8: Pediatric Cardiac Arrest Algorithm

8.1 Arrest Recognition & Systematic Approach 8.2 VF/pVT & Defibrillation Energy 8.3 Asystole & PEA 8.4 Epinephrine in Arrest: Dose & Timing

9 Chapter 9: Bradycardia & Narrow-Complex Tachycardia

9.1 Bradycardia with Poor Perfusion 9.2 Sinus Tachycardia vs SVT 9.3 Stable SVT: Vagal Maneuvers & Adenosine

10 Chapter 10: Unstable Tachycardia & Wide-Complex Rhythms

10.1 Unstable Tachycardia & Synchronized Cardioversion 10.2 Wide-Complex Tachycardia & VT with Pulse 10.3 Antiarrhythmics for Tachycardia with Pulse

11 Chapter 11: Reversible Causes & Special Circumstances

11.1 Reversible Causes: The H's and T's 11.2 Special Circumstances at Exam Level 11.3 Extracorporeal CPR (ECPR) Overview

12 Chapter 12: Post–Cardiac Arrest Care

12.1 Post-ROSC Oxygenation & Ventilation 12.2 Post-Arrest Hemodynamic Support 12.3 Temperature Control & Glucose 12.4 Neuroprognostication & Transport

13 Chapter 13: Vascular Access & Core Pharmacology

13.1 IV and Intraosseous Access 13.2 Epinephrine Dosing in Depth 13.3 Amiodarone, Lidocaine & Adenosine 13.4 Weight-Based Dosing Aids & Drugs to Avoid Routinely

14 Chapter 14: Team Dynamics & Megacode Readiness

14.1 High-Performance Team Roles 14.2 Closed-Loop Communication 14.3 Constructive Intervention, Debriefing & Exam Integration

5.3 Isotonic Fluid Bolus 10–20 mL/kg & Reassessment

Key Takeaways Explain This Topic AI

Standard PALS teaching uses rapid isotonic crystalloid boluses of about 20 mL/kg for many hypovolemic and distributive shock presentations, within a 10–20 mL/kg range

Use the lower end of the range and extra caution when cardiogenic shock is possible and in some neonatal contexts

Deliver boluses rapidly through IV or IO access—do not infuse a 'bolus' slowly over a prolonged drip

Reassess mental status, heart rate, pulses, CRT, blood pressure, and overload signs (rales, hepatomegaly) after every bolus

Check glucose early; place IO access when IV attempts are delayed in the critically ill child
Last updated: August 2026

The bolus is a treatment and a test

In PALS, an isotonic fluid bolus is both therapy and diagnostic probe. You give a measured volume quickly, then ask whether perfusion improved and whether the lungs and liver are tolerating the volume. Candidates fail megacodes when they either (a) never give volume to a clearly hypovolemic child or (b) pour repeated boluses without reassessing and push a cardiogenic child into frank pulmonary edema.

Standard teaching numbers

Situation Typical isotonic crystalloid approach
Hypovolemic shock (most non-hemorrhagic) About 20 mL/kg rapid bolus; repeat as needed with reassessment

Distributive shock (e.g., septic) Often 20 mL/kg boluses with frequent reassessment; total volume may be large but is still titration, not blind continuous flooding

Cardiogenic concern / uncertain type Start with smaller boluses (often ~10 mL/kg) and reassess very carefully for rales/hepatomegaly

Neonates / some cautious contexts Teaching emphasizes the 10–20 mL/kg range with meticulous reassessment rather than automatic large undifferentiated volumes

Hemorrhagic shock Blood products prioritized; crystalloid only as a bridge—do not replace a blood problem with unlimited saline

Memorize the headline: isotonic crystalloid 10–20 mL/kg , commonly 20 mL/kg for straightforward hypovolemic/distributive shock, with reassessment after each bolus .

Which fluid?

PALS teaching centers on isotonic crystalloids for initial expansion (examples in practice include balanced crystalloids or 0.9% sodium chloride per protocol). Hypotonic fluids are not initial shock boluses. Colloid is not the routine first-line PALS exam answer for the first pediatric hypovolemic bolus. Blood products are the volume of choice when the deficit is blood.

How to deliver the bolus: rapid means rapid

A "20 mL/kg bolus" that trickles in over 45 minutes is not PALS resuscitation technique for decompensated hypovolemia.

Practical delivery points

Calculate the volume using measured or estimated weight (length-based tape if unknown): weight (kg) × 10–20 mL.

Draw up or bag the bolus so the team can push it quickly.

Use push-pull syringe technique , a pressure bag, or a rapid infuser as available and appropriate for the line.

Deliver through a working IV or IO . Confirm the line flushes and the limb/IO site is not extravasating.

Announce start and completion with closed-loop communication: "20 mL/kg isotonic crystalloid IO in now" → team member confirms when complete.

Reassess immediately after the bolus finishes—not after a coffee break.

IO when IV is delayed

If peripheral IV access is not rapidly successful in a critically ill or arresting child:

Establish intraosseous access without prolonged delay
IO routes accept crystalloid, blood, and resuscitation medications
Continue attempts at IV access in parallel once IO is working if needed for additional lines
Watch the IO site for infiltration and limb compartment issues

Exam items love the provider who keeps searching for a perfect vein while the hypotensive infant remains without volume. Timely IO is correct, not a last resort after ten failed sticks.

Loading diagram... Fluid Bolus and Reassessment Loop

Reassessment checklist after every bolus

After each 10–20 mL/kg bolus, systematically re-evaluate. This is the evaluate–identify–intervene loop applied to fluid therapy.

Perfusion response (looking for improvement)

Parameter Improving response Worrisome / inadequate response
Mental status More alert, more interactive Still lethargic or worsening
Heart rate Trend down toward age norms Persistent extreme tachycardia or new bradycardia
Pulse quality Stronger peripheral and central pulses Still thready or absent peripherally
Capillary refill Shortening toward ≤2 s (with caveats) Still markedly delayed
Blood pressure Rising if previously low; stable if compensated Falling or newly hypotensive
Skin Warmer, less mottled (in cold shock patterns) Progressive mottling/cyanosis
Urine output Improving over time if catheterized/monitored Persistent anuria/oliguria

If the child improves but still meets shock criteria, another carefully considered bolus may be appropriate. If the child does not improve, ask:

Is access actually working?

Is hemorrhage ongoing (need blood/surgery)?

Is the shock type wrong (distributive needing vasoactives, cardiogenic, obstructive)?

Is glucose low?

Has the child progressed toward arrest?

Fluid overload / cardiogenic warning signs

Stop or slow further empiric large-volume crystalloid and reconsider the diagnosis if you see:

New or worsening pulmonary rales / crackles
Increasing respiratory distress or hypoxemia after fluids
Hepatomegaly (enlarging liver span)
New gallop or marked jugular venous distention when assessable
Clinical picture increasingly consistent with cardiogenic or fluid-intolerant physiology

In those cases, smaller subsequent volumes (if any), expert pediatric critical care support, and inotropic/vasoactive strategies (Chapter 6) take priority over "another 20 mL/kg because the protocol said fluids."

Glucose: the forgotten reassessment item

Critically ill infants and children frequently have hypoglycemia or clinically important glucose abnormalities. Check bedside glucose early in shock care and treat hypoglycemia per PALS/local dosing while volume resuscitation continues. Altered mentation should never be attributed solely to hypoperfusion without considering glucose.

Putting numbers into scenarios
Scenario 1 — Straightforward hypovolemic bolus

A 15 kg toddler with gastroenteritis is in compensated hypovolemic shock. Planned bolus: 20 mL/kg × 15 kg = 300 mL isotonic crystalloid rapid IV/IO. After the bolus, heart rate falls from 180 to 150, CRT improves from 4 s to 2 s, and mentation brightens. SBP remains normal. Plan: continue monitoring; consider additional bolus if perfusion still inadequate or losses continue; start cause-specific care and maintenance planning.

Scenario 2 — Hypotensive shock needing repeated titration

A 20 kg child with septic distributive features is hypotensive. Give 20 mL/kg = 400 mL rapid crystalloid, reassess. If still hypotensive with poor perfusion and no overload signs, repeat boluses while arranging vasoactive support and antibiotics (full septic pathway in Chapter 6). Do not walk away between boluses; the reassess step is mandatory.

Scenario 3 — Cardiogenic caution

A child with known cardiomyopathy presents cool, tachycardic, with mild hepatomegaly and crackles. Shock is present, but large undifferentiated 20 mL/kg serial boluses are dangerous. Use smaller (about 10 mL/kg) cautious challenges only if hypovolemia is also suspected , reassess after each, and prioritize expert support and inotropes rather than volume loading.

Scenario 4 — Hemorrhage

A trauma patient receives a limited crystalloid bridge while blood is being prepared, then blood products and hemorrhage control—not five back-to-back 20 mL/kg saline boluses as the complete plan.

Common exam traps

Trap: "Bolus" as a slow maintenance-rate infusion. → Boluses for shock are rapid .

Trap: No reassessment language in the answer. → Correct answers usually include reassess after each bolus .

Trap: Automatic 20 mL/kg × many without considering cardiogenic signs. → Watch for rales and hepatomegaly .

Trap: Delaying all fluid until a perfect ultrasound and full lab panel return in a crashing hypotensive child. → Access and volume (or blood) while diagnostics run in parallel.

Trap: Forgetting IO when IV fails. → IO is appropriate and expected when delay is harming the child.

Trap: Forgetting glucose. → Check and treat.

Chapter 5 synthesis

You now have the foundation of pediatric shock care:

Shock is inadequate perfusion , split into compensated vs hypotensive using age-based BP thresholds and full perfusion assessment.

Hypovolemia —hemorrhagic or non-hemorrhagic—is the most common pathway; treat losses, use crystalloid or blood appropriately.

Deliver isotonic 10–20 mL/kg boluses rapidly via IV/IO , reassess every time , stop or slow for overload/cardiogenic signs, and check glucose .

Chapter 6 builds on this foundation with distributive/septic, cardiogenic, and obstructive shock pathways where vasoactives, careful fluids, and cause-specific relief dominate after the same recognition and reassessment discipline.