Status Asthmaticus

See Also

Precautions

Severe Asthma Exacerbations are shock states
1. Airway obstruction results in air trapping and Barotrauma (risk of Pneumothorax)
2. Venous return is obstructed with Hypotension (also due to the often associated Hypovolemia)
Severe Asthma patients progress from loud (Wheezing, Tachypnea) to quiet (Respiratory Failure)
1. Do not be reassured by cessation of Wheezing (check for hypoventilation, shallow inspiration)
2. Do not be reassured by a normalizing pH or CO2
  1. May be compensated only be non-sustainable Hyperventilation, verging on Respiratory Failure
References
1. Swadron (2019) Pulmonary 1, CCME Emergency Medicine Board Review, accessed 5/28/2019

Signs
Red Flags suggestive of impending Respiratory Failure

See Asthma Exacerbation Severity Evaluation
See Status Asthmaticus
Inability to speak more than 1-2 words at a time
Increased Somnolence
Cyanosis
Wheezing paradoxically decreases (silent chest)
1. Secondary to increased airway obstruction and less air movement
Pulsus Paradoxus >25 mmHg
PaCO2 normalization or hypercapnia (ominous)
1. However other clinical findings are more reliable indicators of Respiratory Failure than pH and pCO2
2. Consider monitoring End-Tidal CO2 (ETCO2) for overall trends
Bradycardia
Severe Hypoxia

Management
Follow Initial Management per other protocols

Management
Additional Measures for Extremis

Nebulized Albuterol with Ipratropium continuously to hourly
Systemic Corticosteroid
Adrenergic Agonists
1. Epinephrine (preferred)
  1. Consider Epinephrine Autoinjector (e.g. EpiPen) in prehospital setting
  2. High dose: 0.01 mg/kg up to 0.3 mg SC and may be repeated every 5 minutes
  3. Low dose: 0.001 mg/kg (1-2 mcg/kg) IV in small push doses, titrated to effect
    1. Orman and Sloas in Herbert (2015) EM:Rap 15(6):16
2. Terbutaline (alternative)
  1. Adult: 0.25 mg SC now and repeated up to once within 15-30 min
    1. Maximum: 0.5 mg per 4 hours
  2. Child: 0.01 mg/kg (up to 0.25 mg) SC every 20 min for up to 3 doses
    1. May be repeated up to every 2-6 hours
Oxygen 100% (warm, humidified)
1. Delivery by nonrebreather mask or
2. High Flow Nasal Cannula
  1. Child: 20 L/min maximum
  2. Teen: 40 L/min maximum
Two Intravenous Lines
Hypotension
1. Hypotension is common in Severe Asthma (increased thoracic pressure prevents venous return)
2. Consider fluid bolus of Normal Saline 10-20 ml/kg IV (to 500 to 1000 ml IV)
3. Chest XRay to evaluate for Tension Pneumothorax
Consider Magnesium
1. Dose 50 mg/kg (range 25-75 mg/kg) up to 2 grams IV for 1 dose delivered over 15-20 min
2. Drug infusion rate is much faster than the typical 2 hour Magnesium infusion
3. Rapidly effective in pediatric Asthma Exacerbations
4. Also shown effective in severe adult acute Asthma
5. Some studies question benefit
6. References
  1. Silverman (2002) Chest 122:489-97 [PubMed]
  2. Hughes (2003) Lancet 361:2114-7 [PubMed]
Consider Ketamine
1. May improve Status Asthmaticus (not limited to intubation)
2. May allow patients to tolerate BiPap, as well as progress via Delayed Sequence Intubation
3. May increase airway secretions
4. Bolus: 1-2 mg/kg (consider 1 mg/kg to start)
5. Maintenance: 2-3 mg/kg/hour (consider 0.25 mg/kg/hour to start)
Consider Noninvasive Positive Pressure Ventilation (NIPPV, CPAP, BIPAP, HHFNC)
1. See High Humidity High Flow Nasal Oxygen (HHFNC)
2. See Non-Invasive Positive Pressure Ventilation (BIPAP)
3. See Delayed Sequence Intubation (e.g. Ketamine with initial BiPap)
4. NIPPV allows for diaphragmatic and other respiratory Muscle rest
  1. Respiratory muscle Fatigue results in hypercapnia and Respiratory Acidosis
  2. Acidosis results in further respiratory Muscle dysfunction and spiraling increase in hypercapnia
  3. NIPPV decreases CO2, acidosis, and respiratory Fatigue
5. Contraindications (exception: Delayed Sequence Intubation)
  1. Patient not alert or able to control their own airway (aspiration risk)
  2. Hemodynamically unstable (positive pressure reduces negative chest pressure and Preload)
  3. Cardiopulmonary arrest or significant Cardiac Arrhythmia
  4. Upper airway Trauma or obstruction (requires secure airway)
6. Starting settings (Bipap)
  1. Inspiratory pressure: 12 (10 to 15)
  2. Expiratory pressure: 5 (3 to 5)
    1. No significant PEEP is needed in Asthma
7. Consider in combination with Ketamine for sedation (often poorly tolerated otherwise)
  1. Use the lower doses listed above (1 mg/kg bolus then 0.25 mg/kg/hour)
  2. May be used as bridge to intubation (See Delayed Sequence Intubation)
8. Precautions: Severe bronchospasm is unlikely to improve with NIPPV
  1. Tight, quiet chest without excursion and trapped airway gas will not respond to more NIPPV
  2. BiPap machine estimated Tidal Volumes will be low in severe bronchospasm

Management
Measures to Avoid

Avoid Heliox (helium to oxygen 80:20 70:30 or 60:40)
1. Originally showed promise, but does not appear to improve Status Asthmaticus or COPD
  1. Appeared to reduce work of breathing and to improve Peak Flow in original studies
2. Effective in the obstruction of the larger upper airway (e.g. Airway Foreign Body)
  1. However, not effective in the obstruction of the many small to medium airways affected by Asthma
3. Risk of Hypoxemia if FIO2 of oxygen in mixture is too low
Avoid Aminophylline or Theophylline
1. Risk of adverse effects outweigh any marginal benefit
2. Rare indication may be a patient in such distress that will not tolerate the nebulizer
May continue home maintenance Asthma medications, but do not add these medications to control acute Asthma
1. Do not initiate Mast Cell Stabilizers, long acting beta Agonists or Leukotriene Modifiers to control acute Asthma

Management
Intubation and Mechanical Ventilation

Precautions: Intubation is best done semi-electively before crisis
1. Intubation criteria are based on clinical judgment (not on ABG, VBG or other lab criteria)
2. Best if intubation can be avoided due to high risk of complications in Asthma (esp. Barotrauma)
  1. Even with Pneumothorax, Barotrauma to small alveoli may have longterm remodeling effects
3. Hypercarbia in Status Asthmaticus is a failure of ventilation (not oxygenation)
  1. Hypercapnea is corrected with Respiratory Rate and Tidal Volume
  2. Respiratory Rate increases Breath Stacking and Tidal Volume increases Barotrauma
Indications (indicated in 0.5% of Asthma Exacerbations)
1. Impending or actual respiratory arrest
2. Extreme muscle Fatigue
3. Altered Mental Status
4. Significant respiratory distress
5. Severe Respiratory Acidosis and Metabolic Acidosis
6. Hemodynamic instability (e.g. Hypotension)
7. Persistent Hypoxemia and hypercapnia
  1. Arterial Blood Gas is not required as a criteria for intubation (clinical status is preferred)
  2. Arterial Blood Gas is indicated after intubation to adjust Ventilator settings
Oral intubation is preferred
1. Lower resistance and easier suctioning
2. Lower Incidence of Sinusitis
Endotracheal Tube selection
1. Choose largest cuffed Endotracheal Tube possible
Rapid Sequence Intubation
1. Sedation
  1. Ketamine (preferred in Asthma Exacerbation)
    1. Use with paralytic due to laryngospasm risk
  2. Etomidate
    1. Use as an alternative
2. Paralytic
  1. Succinylcholine (preferred due to shorter duration)
  2. Rocuronium (if Hyperkalemia risk)
3. Consider Lidocaine for pretreatment
4. Consider Normal Saline bolus (10-20 cc/kg) to prevent post-intubation Hypotension
5. Maximize preoxygenation (see Rapid Sequence Intubation for protocol)
Post-intubation Management
1. Avoid repeated Paralytic Agents after intubation if possible
2. Continue aggressive Asthma Management after intubation
  1. Duonebs
  2. Magnesium
  3. Corticosteroids
3. Ketamine may be preferred for post-intubation (Bronchodilator and mucolytic)
  1. See doses above
4. Permissive hypercapnea (allowing CO2 to rise)
  1. Preferred over aggressive Hyperventilation with risk of Barotrauma (Pneumothorax risk)
  2. Settings to prevent baratrauma
    1. Ventilator rate: Low (start at 10-12 breaths/min, or start as low as 6 breaths/min)
      1. Allow for adequate exhalation time (prevents Breath Stacking, Auto-PEEP)
    2. Tidal Volume: Low
      1. Start at 6 ml/kg
      2. May titrate to 8-10 ml/kg (but keep plateau pressure <30 cm H2O)
      3. Risk of braotrauma at higher Tidal Volumes
    3. Inspiratory Flow rate: High (start at 80-100 ml/hour)
    4. Expiratory Time: High (long)
    5. Inspiratory-Expiratory Ratio (I-E Ratio): 1 to 4
    6. FIO2: Lowest level to keep Oxygen Saturation >90%
    7. Plateau pressure: <30 cm H2O
    8. Consider PEEP 3-5
      1. Requires close observation for Auto-PEEP by patient
    9. SIMV Mode may be preferred over AC in Status Asthmaticus
      1. Allows for patient to trigger breath and prevent Breath Stacking
5. Difficult to ventilate patients
  1. Optimize pulmonary toilet
  2. Consider bronchoscopy
  3. May benefit from inhalation gasses in operating room or ECMO
6. Observe for intubation complications
  1. Barotrauma (e.g. Pneumothorax)
  2. Hemodynamic compromise (Hypotension)
  3. Pulmonary hyperinflation (Breath Stacking)

Management
Cardiac Arrest

Disconnect the Ventilator
1. Manually ventilate slowly
2. Prevents Breath Stacking
Decompress the chest manually
1. Bear hug to remove trapped air
Place bilateral Chest Tubes
1. High risk of Tension Pneumothorax
2. May temporize with bilateral needle thoracostamy
Empirically give Intravenous Fluids (1 Liter)
1. See Hypotension above
Consider other measures
1. Anesthetic gases (as bridge to ECMO)
2. ECMO

References

Serrano (2014) Crit Dec Emerg Med 28(6):2-10
Sherman (2014) Crit Dec Emerg Med 8(2): 12-18
Herbert (2012) EM:RAP-C3 2(2): 1
Weingart and Swaminathan in Swadron (2022) EM:Rap 22(5): 3-4
(1997) Management of Asthma, NIH 97-4053
(1995) Global Strategy for Asthma, NIH 95-3659
Pollart (2011) Am Fam Physician 84(1): 40-7 [PubMed]
Ciarallo (2000) Arch Pediatr Adolesc Med 154:979-83 [PubMed]
Sarfone (2000) Ann Emerg Med 36:572-8 [PubMed]