01Approach to the Critical Patient/attcp56

Immediate priorities

›Airway and breathing threats

›Apnea or respiratory failure risk

›Age < 2 months (high-risk cohort)

›Prematurity < 32 weeks gestation

›Prior intubation history

›Severe hypoxemia

›SpO2 < 90% on room air (OR 8.9 for need for respiratory support)

›Cyanosis or dusky discoloration

›Impending respiratory failure signs

›Silent chest or severely diminished air entry

›Head bobbing, nasal flaring, grunting

›Altered mental status or extreme lethargy

›If apnea or SpO2 < 90% unresponsive to low-flow O2, escalate immediately

›HFNC or CPAP consideration

›Pediatric intensive care consult

›Stabilization priorities

›Gentle nasal suctioning before oxygenation assessment

›Bulb syringe or suction catheter

›Avoid deep or aggressive suctioning

›Supplemental oxygen to maintain SpO2 > 90%

›Low-flow nasal cannula first line

›HFNC for moderate-severe or escalating requirement

›Position of comfort

›Semi-recumbent or caregiver-held position

›Minimize handling in moderate-severe cases

Monitoring and targets

›Monitoring parameters

02History/hx76

Presentation pattern

›Cardinal symptom sequence

›URI prodrome

›Rhinorrhea, congestion, sneezing 2-4 days prior

›Low-grade fever (present in ~15% of RSV cases)

›Lower respiratory phase

›Cough onset after prodrome

›Increased work of breathing

›Wheeze or noisy breathing

›Feeding difficulty

›Decreased oral intake (OR 1.9 for hospitalization)

›Refusal to feed due to respiratory distress

›Timeline and trajectory

›Peak severity day 3-5 of illness

›Patients presenting early may worsen before improving

›Duration 7-14 days typical

›Cough resolution within 3 weeks in 90% of cases

›Persistent symptoms beyond 3 weeks prompt reassessment

›Early presentation carries risk of clinical deterioration before peak

Alarm features

›High-risk symptoms

›Apnea or pauses in breathing

›Especially neonates and infants < 2 months

›Witnessed vs suspected

›Cyanosis or dusky coloring

›Central vs peripheral

›Transient vs persistent

›Lethargy or difficulty arousing

03Physical Exam/exam62

Vital signs and general

›Stability snapshot

›Respiratory rate (age-adjusted tachypnea thresholds)

›> 60 per minute in neonates

›> 50 per minute in infants < 2 months

›> 40 per minute in infants 2-12 months

›SpO2 on room air

›< 90% as major severity marker (OR 8.9 for respiratory support need)

›Continuous vs intermittent per severity

›Heart rate

›Tachycardia proportionate to fever vs disproportionate

›Bradycardia as ominous sign in neonates

›Temperature

›Low-grade fever typical (present in ~15% of RSV cases)

›New fever late in illness suggests bacterial superinfection

›Hydration and general status

›Fontanelle assessment

›Sunken suggests dehydration

›Bulging rare but prompts CNS consideration

›Mucous membranes and skin turgor

›Dry membranes and reduced turgor indicate dehydration

›Capillary refill > 2 seconds as perfusion marker

Respiratory exam

›Work of breathing

›Nasal flaring (OR 3.8 for hospitalization)

›Nares widening on inspiration

›More prominent in young infants

›Grunting

04Differential Diagnosis/ddx48

Life-threatening diagnoses

›Immediate threats

›Respiratory failure from any cause

›Clinical deterioration marker

›Escalation trigger

›Congenital heart disease decompensation

›ICD-10 Q20-Q26 spectrum

›Absence of URI prodrome

›Hepatomegaly, murmur, failure to thrive

›Myocarditis

›ICD-10 I40.9

›Tachycardia disproportionate to fever

›Poor perfusion and hepatomegaly

›Bacterial sepsis

›ICD-10 A41.9

›Neonates may present with bronchiolitis-like picture

›Consider in age < 28 days or ill-appearing infants

Infectious mimics

›Respiratory infections

›Pertussis

›ICD-10 A37

›Paroxysmal cough, post-tussive emesis, apnea

›Consider if severe cough or known exposure

›Bacterial pneumonia

›ICD-10 J18.9

›New fever, focal consolidation, clinical deterioration

›Outside typical bronchiolitis trajectory

›Viral pneumonia overlap

05Laboratory Tests/lt37

Routine labs

›Labs NOT routinely recommended (AAP guidelines)

›Routine CBC not indicated in typical bronchiolitis

›Does not change management

›Does not predict severity or need for admission

›RSV rapid antigen or PCR testing not routinely needed for clinical management

›May assist cohorting, antibiotic stewardship, and epidemiologic tracking

›Point-of-care RSV molecular testing: sensitivity/specificity non-inferior to PCR

›Chest radiograph not routinely recommended

›Leads to unnecessary antibiotic use without management change

›AAP Clinical Practice Guideline Level B recommendation against routine CXR

Selective laboratory testing

›When to consider labs

›Concern for bacterial co-infection

›CBC with differential (leukocytosis or left shift)

›CRP as inflammatory marker

›Blood culture prior to antibiotics

›Bacterial co-infection rate < 11%

›Dehydration assessment

›Basic metabolic panel

›Electrolytes for fluid replacement planning

›Renal function for IV fluid dosing

›Sepsis workup in neonates

›Age < 28 days: full sepsis evaluation

›Lumbar puncture consideration per clinical picture

›Cardiac laboratory evaluation

›Troponin and BNP

›Consider if cardiac involvement suspected

06Diagnostic Tests/dt65

Scoring Systems

›Severity scoring tools

›Wang Respiratory Distress Assessment Instrument (RDAI)

›Scores wheezing, retractions (inspiratory, expiratory, depth, location)

›Modest predictive ability for hospitalization

›No universally validated threshold for ED decisions

›Modified Tal Severity Score (mTAL)

›SpO2, wheezing, accessory muscle use, cyanosis

›Used in research settings and some clinical trials

›Score 0-4: mild; 5-9: moderate; 10-12: severe

›Pediatric Respiratory Assessment Measure (PRAM)

›Validated primarily for asthma; sometimes applied to wheeze

›Less validated in pure bronchiolitis

›No universally accepted severity scoring tool per AAP guidelines

›Clinical trajectory and functional assessment supersede single score

›ACEP Level C recommendation: use scoring as adjunct not replacement

MRI

›MRI role in bronchiolitis

›No routine utility in acute bronchiolitis

›Not part of standard evaluation

›Availability and motion artifact barriers

›Potential problem-solving indications

›Suspected vascular ring or airway anomaly causing recurrent wheeze

›MRI chest or MRA to delineate vascular compression without radiation

›Cardiac MRI if myocarditis suspected with non-diagnostic echo

›Practical limitations

›Requires sedation in infants

›Not appropriate in hemodynamically unstable patients

07Disposition/dispo56

Admission criteria

›Indications for inpatient admission

›Hypoxemia

›SpO2 < 90% on room air

›Escalating oxygen requirement

›Significant work of breathing

›Nasal flaring, grunting, moderate-severe retractions

›Inability to sustain adequate effort

›Apnea

›Any witnessed apnea event

›Especially in neonates or infants < 2 months

›Inadequate hydration

›Inability to maintain oral intake

›Dehydration on exam

›Age and risk factors

›Age <= 2 months (lower threshold for admission)

›Multiple risk factors present simultaneously

›Unreliable follow-up or significant caregiver concern

›ICU admission triggers

›Impending respiratory failure

›Need for HFNC beyond ward capability

›Need for CPAP or intubation

›Recurrent or prolonged apnea

›Requires continuous monitoring and rapid response capability

›Especially in neonates

›Hemodynamic instability

›Suspected myocarditis or CHD decompensation

›Shock physiology

08Treatment/t100

Supportive care

›Nasal suctioning

›Gentle nasal suction prior to feeds and assessments

›Bulb syringe or catheter at nares

›Avoid deep or aggressive suctioning

›ACEP Level B recommendation against routine deep suctioning

›Saline nasal drops may assist loosening secretions

›Prior to bulb suctioning

›Preservative-free isotonic saline preferred

›Oxygen therapy

›Low-flow nasal cannula

›Initiate for SpO2 < 90%

›Target SpO2 > 90% (AAP threshold)

›Titrate to lowest effective flow

›High-flow nasal cannula (HFNC)

›Escalate when low-flow insufficient or moderate-severe distress

›Initial flow: 1-2 L/kg/min

›FiO2 titrated to SpO2 target

›Growing evidence for ward-level HFNC use; reduces ICU transfers in some trials

›CPAP

›Reserved for HFNC failure or impending respiratory failure

›Cochrane review 2022: CPAP reduces need for intubation in severe bronchiolitis

›PEEP 5-7 cmH2O typical starting pressure

›Mechanical ventilation

›Intubation for refractory respiratory failure or apnea with hemodynamic compromise

›5-6% of hospitalized infants require ICU; small subset require mechanical ventilation

Hydration management

›Oral or enteral feeds

›Maintain feeds if tolerated

›Breastfeeding encouraged when possible

›Small, frequent feeds may be better tolerated than large volumes

›Nasogastric feeds (preferred over IV)

›When oral intake inadequate due to respiratory distress

›Two RCTs showed no outcome difference between NG and IV but NG has fewer complications

›Continuous NG feed or bolus based on tolerance

›Intravenous fluid therapy

›Isotonic IV fluids when NG not tolerated or contraindicated

›0.9% NaCl or Lactated Ringer's

›Maintenance rate based on weight: Holliday-Segar method

›For < 10 kg: 100 mL/kg/day; 10-20 kg: 1000 mL + 50 mL/kg over 10 kg

›Reassess hydration status with each clinical assessment

›Urine output target: > 1 mL/kg/hour

›Monitor electrolytes in prolonged IV administration

Treatments NOT recommended

›Evidence-based non-recommendations (AAP/NICE guidelines)

›Bronchodilators (salbutamol, ipratropium)

›Do not improve SpO2, admission rates, length of stay, or illness duration

›Cause adverse effects: tachycardia, tremor, desaturation

›ACEP Level A evidence against routine use

›Nebulized epinephrine (inpatient)

›Not recommended for inpatients per AAP guidelines

›May reduce ED admissions if given within 24 hours of outpatient presentation (NNT = 5)

›Evidence does not support inpatient use

›Corticosteroids

›Systemic or inhaled: do not reduce admissions or length of stay

›No benefit alone or combined with epinephrine (Cochrane review)

›ACEP Level A evidence against routine use

›Antibiotics

›Only if concurrent bacterial infection is documented

›Bacterial co-infection rate < 11%

›~30% of children receive unnecessary antibiotics in practice

›Nebulized hypertonic saline

›Cochrane review 2023: no reduction in hospital admission rate

›No significant reduction in length of stay

›Not recommended routinely; may consider in selected inpatients

›Chest physiotherapy

›Not recommended; no clinical benefit shown

›AAP guideline recommendation against

Antipyretics and comfort

›Fever management

›Acetaminophen (paracetamol)

›15 mg/kg/dose every 4-6 hours PO/PR

›Maximum 5 doses per 24 hours

›For comfort, not disease modification

›Ibuprofen

›10 mg/kg/dose every 6-8 hours PO

›Only for infants > 6 months

›Avoid in dehydration or renal compromise

Prevention (immunoprophylaxis)

›Nirsevimab (Beyfortus)

›Indication: all infants entering first RSV season

›Single IM dose

›50 mg if < 5 kg

›100 mg if >= 5 kg

›Efficacy

›~80% reduction in RSV hospitalization

›~90% reduction in ICU admission (JAMA Pediatrics 2025)

›ACIP recommended for all infants < 8 months entering first RSV season

›Clesrovimab (Enflonsia)

›Recently FDA-approved alternative monoclonal antibody

›For infants in first RSV season

›Non-inferior efficacy profile to nirsevimab

›Maternal RSV vaccination (Abrysvo)

›RSVpreF vaccine administered at 32-36 weeks gestation

›~82% efficacy against severe RSV LRTI through 90 days of life

›Passive antibody transfer to neonate

›SMFM 2024 clinical considerations published

›Palivizumab (Synagis)

›Reserved for high-risk infants if nirsevimab unavailable

›Monthly IM injections throughout RSV season

›15 mg/kg/dose IM monthly for up to 5 doses

›Indications (when nirsevimab not available)

›Prematurity < 29 weeks gestation

›Bronchopulmonary dysplasia requiring treatment

›Hemodynamically significant congenital heart disease

09Special Populations/sp71

Pregnancy

›Maternal RSV infection considerations

›RSV in pregnant individuals

›May present with more severe lower respiratory tract illness

›Fetal monitoring when viable gestation and maternal hypoxemia

›Maintain maternal SpO2 >= 95% when feasible for fetal wellbeing

›Neonatal RSV risk post-delivery

›Premature delivery due to maternal illness increases neonatal RSV risk

›NICU infants at elevated RSV severity risk

›Prophylaxis in pregnancy

›Maternal RSVpreF vaccine (Abrysvo) at 32-36 weeks

›82% efficacy against severe infant RSV LRTI through 90 days

›Single dose recommended per ACIP and SMFM 2024

›Drug safety in pregnancy

›Antipyretics

›Acetaminophen preferred for fever management

›Ibuprofen: avoid after 20 weeks gestation

›Antibiotics if bacterial superinfection

›Amoxicillin or amoxicillin-clavulanate generally safe

›Avoid fluoroquinolones and tetracyclines

Geriatric

›RSV in older adults

›RSV increasingly recognized as significant adult pathogen

›14,000-177,000 hospitalizations annually in adults >= 65 years (CDC)

›Associated with higher mortality than in young adults

›Clinical presentation in older adults

›May mimic influenza or exacerbation of COPD or heart failure

›Atypical presentation common: delirium, functional decline

›Cardiac complications: RSV associated with new-onset heart failure and arrhythmias

›Management considerations

›Aggressive management of underlying comorbidities

›Lower threshold for imaging and cardiac workup

›RSV vaccination available: Abrysvo or Arexvy for adults >= 60 years

›Comorbidity implications

›COPD and asthma

›RSV a leading trigger of COPD exacerbations

›Bronchodilators indicated (unlike in infant bronchiolitis)

›Heart failure

›RSV associated with decompensation

›Diuresis may be required alongside respiratory support

Pediatrics

›Age-specific severity thresholds

›Neonates (< 28 days)

›May present with sepsis-like illness or isolated apnea

›Full sepsis evaluation often required

›ICU-level monitoring threshold very low

›Young infants (< 2 months)

›Apnea risk substantially higher (OR 3.0 for apnea)

›Feeding intolerance as primary severity marker

›Age <= 2 months: OR 2.1 for hospitalization

›Infants 2-12 months

›Classic bronchiolitis presentation

›Work of breathing and SpO2 primary severity markers

›Children 12-24 months

›Recurrent wheezing consideration

›May begin to show asthma-like treatment response

›High-risk pediatric conditions

›Premature infants

›BPD patients require nirsevimab or palivizumab

›Higher rate of ICU admission and mechanical ventilation

›Down syndrome

›Increased risk for severe bronchiolitis

›Airway anatomy differences contribute

›Congenital heart disease

›Hemodynamically significant CHD: higher mortality from RSV

›Cardiology co-management

›Post-bronchiolitis long-term risk

›Recurrent wheezing

›RSV bronchiolitis associated with 2-4-fold increased recurrent wheeze risk (meta-analysis OR 3.84)

›17-60% of hospitalized children develop recurrent wheezing in subsequent years

›Association attenuates with age; causal vs shared predisposition debated

›Asthma development

›Population-based study: bronchiolitis regardless of etiology associated with increased asthma risk

›Counsel families on surveillance for asthma symptoms

10Background/b78

Epidemiology

›Disease burden

›Leading cause of infant hospitalization worldwide

›RSV accounts for 60-80% of bronchiolitis cases

›Most common lower respiratory tract infection in infants

›Hospitalization rates

›~3% of all infants hospitalized for RSV in first year of life

›Peak hospitalization rates in infants 2-3 months of age

›5-6% of hospitalized infants require ICU admission

›Seasonality

›Traditional November-April peak in northern hemisphere

›COVID-19 pandemic caused off-season surges (2021-2022)

›Danish nationwide cohort: pandemic-era changes in RSV hospitalization timing documented

›Global and demographic burden

›Risk distribution

›Male sex, Indigenous ethnicity higher risk

›Low-income countries: disproportionate mortality burden

›Australian Aboriginal, First Nations, Maori populations: elevated severe disease rates

›Nirsevimab impact (JAMA Pediatrics 2025)

›2023-2024 season: significant reduction in RSV hospitalization in infants receiving nirsevimab

›Real-world effectiveness data supporting policy implementation

Pathophysiology

›RSV biology

›Virus characteristics

›Negative-sense single-stranded RNA virus

›Paramyxoviridae family, Pneumoviridae subfamily

›Two major antigenic subtypes: RSV-A and RSV-B

›Incubation and transmission

›Incubation period 4-6 days

›Transmission via contact with infected secretions

›Fomite survival up to several hours on surfaces

›Disease mechanism in bronchiolitis

›Viral invasion of small airways (bronchioles)

›Direct cytopathic effect on airway epithelium

›Inflammatory cell infiltration

›Mucus hypersecretion and cellular debris

›Airway obstruction cascade

›Edema of bronchiolar walls

›Mucus plugging causing air trapping and atelectasis

›Ventilation-perfusion mismatch causing hypoxemia

›Hyperinflation mechanism

›Ball-valve obstruction: air enters but cannot fully exit

›Increased residual volume and functional residual capacity

›Diaphragm flattening contributing to respiratory fatigue

›Cardiac manifestations

›RSV cardiac tropism

›Sinoatrial block in 76.5% of RSV-positive infants (Holter study)

›vs 2.9% of RSV-negative controls

›Arrhythmias: ectopic atrial tachycardia, chaotic atrial tachycardia, atrial flutter, sinus arrest

›Long-term respiratory sequelae

›Early-life RSV LRTI associated with recurrent wheeze and asthma

›Lancet Respiratory Medicine 2024 review: long-term respiratory health impacts

Therapeutic Considerations

›Evidence base for supportive care

›What works: oxygen and fluid support

›SpO2 > 90% threshold supported by AAP guidelines (Level B)

›NG feeds preferred over IV in two RCTs (comparable outcomes, fewer complications with NG)

›HFNC reduces ICU admission in moderate-severe bronchiolitis in some trial data

›What does not work

›Bronchodilators: Cochrane and multiple RCTs show no benefit

›Steroids: no benefit alone or with epinephrine

›Hypertonic saline: Cochrane 2023 shows no reduction in hospitalization or LOS

›Antibiotics: unnecessary in > 30% of cases receiving them; co-infection rate < 11%

›Chest physiotherapy: no clinical benefit; guideline against

›Emerging and investigational therapies

›Magnesium sulphate

›Cochrane review 2026: insufficient evidence to support routine use in bronchiolitis

›Currently not recommended outside of trial settings

›Immunoglobulin therapy

›Cochrane review 2023: no benefit for hospitalized infants

›Not recommended

›Antiviral therapy

›No approved antiviral for RSV bronchiolitis in infants

›Ribavirin not routinely recommended; reserved for severely immunocompromised

›Prevention as cornerstone of disease management

›Nirsevimab vs maternal vaccine comparison

›JAMA 2025: nirsevimab more effective than maternal RSVpreF for preventing RSV hospitalization in newborns

›Both strategies recommended where available (complementary, not mutually exclusive)

›Antibiotic stewardship

›IDSA/ASM 2024 laboratory utilization guide: viral testing to reduce unnecessary antibiotics

›Multiplex testing for cohorting and stewardship programs

11Patient Discharge Instructions/pdi50

copy discharge instructions

›What is bronchiolitis

›A viral infection causing swelling and mucus in the small airways of the lungs

›Most commonly caused by RSV (respiratory syncytial virus)

›Very common in babies and children under 2 years of age

›Expected course

›Symptoms usually peak around days 3-5 of illness

›Most children improve gradually over 1-2 weeks

›A cough may last up to 3 weeks

›Home care instructions

›Nasal congestion

›Use saline nose drops and a bulb syringe to gently clear the nose

›Suction before feeds and sleep

›Avoid deep suction or inserting the bulb deep into the nose

›Feeding and fluids

›Offer smaller, more frequent feeds if breathing makes feeding difficult

›Breastfeeding: continue if possible

›Watch for at least 3-4 wet diapers per day as a sign of adequate hydration

›Comfort and environment

›Use a cool-mist humidifier in the child's room if available

›Keep the child away from cigarette smoke

›Avoid exposing the child to other sick contacts

›Medications

›Acetaminophen (paracetamol) for fever or comfort per weight-based dosing on the label

›Do NOT give salbutamol (ventolin), steroids, or antibiotics unless specifically prescribed

›Cough medicines are not recommended for infants

›Warning signs: return to ER immediately if

›Breathing difficulty

12References/r36

Guidelines and key sources

›AAP and major society guidelines

›American Academy of Pediatrics (AAP) Clinical Practice Guideline: Diagnosis, Management, and Prevention of Bronchiolitis (2014, reaffirmed 2021)

›Graded evidence against routine labs, imaging, bronchodilators, steroids

›Level B recommendation: SpO2 threshold > 90% for oxygen use

›ACIP: Use of Nirsevimab for Prevention of RSV Disease (MMWR 2023)

›Jones JM et al. MMWR Morb Mortal Wkly Rep 2023

›SMFM Statement: Clinical Considerations for RSV Disease Prevention in Infants (AJOG 2024)

›Joseph NT et al. Am J Obstet Gynecol 2024

›Landmark trials and systematic reviews

›Oppenlander KE et al. RSV Bronchiolitis: Rapid Evidence Review. Am Fam Physician 2023

›PMID 37440737

›Dalziel SR et al. Bronchiolitis. Lancet 2022

›PMID 35785792

›Meissner HC. Viral Bronchiolitis in Children. N Engl J Med 2016

›DOI 10.1056/NEJMra1413456

›Zhang L et al. Nebulised Hypertonic Saline for Acute Bronchiolitis. Cochrane Database 2023

›No significant reduction in hospitalization or LOS

›Jat KR et al. CPAP for Acute Bronchiolitis. Cochrane Database 2022

›CPAP reduces intubation need in severe cases

›Chandelia S et al. Magnesium Sulphate for Bronchiolitis under 2 years. Cochrane 2026

›Insufficient evidence for routine use

›Recent evidence and real-world data

›Moline HL et al. RSV Disease Burden and Nirsevimab Effectiveness 2023-2024. JAMA Pediatrics 2025

›Real-world effectiveness of nirsevimab

›Jabagi MJ et al. Nirsevimab vs RSVpreF Vaccine for RSV Hospitalization. JAMA 2025

›Nirsevimab more effective than maternal vaccine for newborn RSV hospitalization

›Halasa N et al. Infants Admitted to US ICUs for RSV 2022. JAMA Netw Open 2023

Evidence & Review