Overview
Definition:
Severe asthma in a pediatric intensive care unit (PICU) setting refers to a life-threatening exacerbation characterized by severe airflow limitation, inadequate response to standard bronchodilator therapy, and significant respiratory distress requiring intensive monitoring and advanced management strategies
These patients often present with hypoxemia, hypercapnia, and altered mental status.
Epidemiology:
Asthma is a common chronic respiratory disease in children
Severe exacerbations requiring PICU admission occur in a minority of patients, but are associated with significant morbidity and mortality
Factors predisposing to severe exacerbations include poor adherence to maintenance therapy, viral infections, environmental triggers, and underlying comorbidities.
Clinical Significance:
Effective management of severe asthma in the PICU is crucial for preventing respiratory failure, reducing length of stay, and improving outcomes
Understanding advanced therapeutic modalities like continuous albuterol and ketamine infusions is vital for pediatric critical care physicians and residents preparing for DNB and NEET SS examinations, as these strategies address refractory bronchospasm and may reduce the need for mechanical ventilation.
Clinical Presentation
Symptoms:
Severe shortness of breath
Difficulty speaking in full sentences
Accessory muscle use
Nasal flaring
Grunting
Altered mental status, including lethargy or agitation
Cyanosis
Inability to lie down (tripoding).
Signs:
Tachypnea with respiratory rates significantly above normal for age
Tachycardia
Paradoxical chest wall movements
Expiratory wheezing, which may be absent in very severe cases due to poor airflow (silent chest)
Prolonged expiratory phase
Decreased breath sounds
Decreased oxygen saturation (SpO2 < 90% on room air)
Increased end-tidal CO2 (EtCO2) or arterial PaCO2.
Diagnostic Criteria:
No single diagnostic criterion exists for "severe asthma in PICU," but it is typically characterized by a combination of: severe persistent wheezing and dyspnea
failure to respond to multiple nebulized short-acting beta-agonists (SABAs)
evidence of respiratory distress (accessory muscle use, tachypnea, tachycardia)
hypoxemia or hypercapnia
altered mental status
requirement for PICU admission and advanced interventions.
Diagnostic Approach
History Taking:
Detailed history of current exacerbation: onset, severity, previous exacerbations, triggers
Asthma severity and control at home: medications used, adherence, prior hospitalizations/intubations
History of allergies or atopic conditions
Family history of asthma or atopy
Concurrent illnesses (e.g., pneumonia, viral infections).
Physical Examination:
Systematic assessment focusing on respiratory status: airway patency, respiratory rate and effort, breath sounds, presence of wheezing or diminished air entry
Cardiovascular assessment: heart rate, blood pressure, perfusion
Neurological assessment: level of consciousness, pupillary response
Skin assessment for cyanosis.
Investigations:
Arterial blood gas (ABG) analysis: crucial for assessing oxygenation (PaO2), ventilation (PaCO2), and acid-base status
Normal or low PaCO2 initially may indicate hyperventilation, while rising PaCO2 suggests impending respiratory failure
Chest X-ray: to rule out alternative diagnoses like pneumonia, pneumothorax, or atelectasis
Complete blood count (CBC) with differential: may show eosinophilia in allergic asthma
Serum electrolytes: important for fluid balance and management
Peak expiratory flow rate (PEFR): useful if the child can cooperate, but often unreliable in severe distress
Continuous pulse oximetry: for monitoring oxygen saturation.
Differential Diagnosis:
Bronchiolitis
Pneumonia
Pneumothorax
Foreign body aspiration
Anaphylaxis
Sepsis with respiratory compromise
Congestive heart failure
Upper airway obstruction.
Management
Initial Management:
Immediate assessment of airway, breathing, and circulation (ABC)
High-flow oxygen therapy to maintain SpO2 > 90%
Frequent nebulized SABAs (e.g., albuterol) every 20 minutes for up to 3 doses, often combined with ipratropium bromide
Intravenous (IV) corticosteroids (e.g., methylprednisolone or hydrocortisone) to reduce airway inflammation
Consider magnesium sulfate infusion for severe, refractory bronchospasm
Continuous cardiorespiratory monitoring and pulse oximetry.
Medical Management:
Continuous albuterol infusion: initiated if intermittent nebulized SABAs are insufficient
Typical dose: 0.1 mg/kg/hr (or 10-20 mcg/kg/hr), titrating to response and avoiding tachycardia
Ketamine infusion: an N-methyl-D-aspartate (NMDA) receptor antagonist, may be used as an adjunct for refractory bronchospasm, particularly when airway resistance is high and ventilation is compromised
It has bronchodilatory properties and can provide sedation
Initial dose: 0.3-1 mg/kg/hr, titrating based on clinical effect and hemodynamic stability
Use with caution due to potential for increased secretions and hemodynamic effects
Systemic corticosteroids: continue IV route until patient improves, then transition to oral
Consider inhaled corticosteroids for long-term control once stable
Mechanical ventilation: considered if respiratory failure persists despite maximal medical therapy
Pressure-controlled ventilation (PCV) or assist-control ventilation (ACV) with low tidal volumes and permissive hypercapnia may be employed.
Surgical Management:
Surgical intervention is rarely indicated for severe asthma exacerbations
However, complications like tension pneumothorax may require emergent chest tube insertion.
Supportive Care:
Aggressive fluid management to maintain adequate hydration and perfusion
Nutritional support may be necessary if prolonged PICU stay is anticipated
Meticulous nursing care including frequent suctioning if needed, vigilant monitoring of vital signs and respiratory status, and prompt recognition of worsening condition
Sedation and analgesia, carefully balanced with respiratory drive.
Complications
Early Complications:
Respiratory failure requiring mechanical ventilation
Pneumothorax
Barotrauma
Ventilator-associated pneumonia (VAP)
Cardiac arrhythmias due to excessive beta-agonist stimulation
Hypokalemia
Hyperglycemia
Acute respiratory distress syndrome (ARDS).
Late Complications:
Development of chronic obstructive pulmonary disease (COPD) features in adulthood
Airway remodeling
Persistent asthma symptoms
Psychological impact of severe illness and PICU stay.
Prevention Strategies:
Ensuring adherence to maintenance asthma therapy
Identifying and avoiding triggers
Prompt recognition and aggressive treatment of early symptoms of exacerbation
Optimizing bronchodilator and corticosteroid therapy
Judicious use of mechanical ventilation and early extubation when safe
Implementing VAP prevention bundles.
Prognosis
Factors Affecting Prognosis:
Severity of initial exacerbation
Response to initial treatment
Presence of comorbidities
Degree of hypoxemia and hypercapnia
Need for mechanical ventilation
Duration of PICU stay and hospital stay
Development of complications.
Outcomes:
With optimal management, most children with severe asthma exacerbations in the PICU survive
However, prolonged recovery, recurrent exacerbations, and long-term pulmonary sequelae are possible
Early and aggressive intervention improves outcomes and reduces the risk of mortality.
Follow Up:
Close follow-up with a pediatric pulmonologist or allergist is essential after discharge
This includes medication review, education on trigger avoidance, adherence to maintenance therapy, and asthma action plan development
Regular pulmonary function testing may be indicated.
Key Points
Exam Focus:
Continuous albuterol infusion rate (mcg/kg/hr)
Ketamine use in refractory bronchospasm (mechanism, dosing, side effects)
ABG interpretation in asthma exacerbations (initial low/normal CO2 vs
rising CO2)
Steroids are essential for reducing inflammation
Magnesium sulfate as adjunct therapy
Indications for mechanical ventilation.
Clinical Pearls:
A silent chest is an ominous sign of impending respiratory arrest
Monitor for cardiac arrhythmias and electrolyte imbalances with continuous albuterol infusions
Ketamine can be a useful bronchodilator and sedative, but requires careful hemodynamic monitoring
Early initiation of systemic corticosteroids is crucial
Consider continuous albuterol infusion early if response to intermittent nebulizers is poor.
Common Mistakes:
Delaying aggressive bronchodilator or corticosteroid therapy
Over-reliance on SABAs without addressing inflammation
Inadequate monitoring of vital signs and ABGs
Failure to recognize impending respiratory failure
Inappropriate sedation leading to suppressed respiratory drive
Not optimizing post-PICU follow-up and asthma control.