Status Asthmaticus

Question 1

Patient presents in status asthmaticus with evidence of hypercarbic respiratory failure on ABG.

What do you do?

Answer 1

1. Rapid sequence intubation and mechanical ventilation with high pressure, low volume (6 mL/kg), low PEEP (5 or less), RR 8-10/minute, P_Plateau < 30 cm H2O (when possible)
2. Aerosolized albuterol and ipratropium bromide
3. IV corticosteroids (40-60 mg methylprednisolone) and 2 g magnesium bolus over 20 minutes followed by 2-4g/hr drip
4. Sedation with bronchodilating anesthetic (IV propofol or ketamine or inhaled halothane, isoflurane, or sevoflurane)

Question 2

What is the #1 thing that can go wrong in ventilating a patient in status asthmaticus?

Answer 2

Buildup of auto-PEEP due to insufficient expiration time (aka breath stacking, aka dynamic hyperinflation)

This can result in cor pulmonale, hypotension, barotrauma, and potentially spontaneous pneumothorax.

We try to avoid this by decreasing the tidal volume and respiratory rate, increasing inspiratory flow rate as much as possible, and using sedation judiciously.

Question 3

Minimizing airway resistance in status asthmaticus

Answer 3

High airway resistance is both the primary etiology of, and major risk factor for complicatons during, status asthmaticus.

So, reducing resistance is key to therapy. This is done by:

• Inhaled and systemic bronchodilators
• Large bore endotracheal tube
• Frequent suctioning of secretions

Question 4

Vocal cord dysfunction

Answer 4

An important mimic of asthma

Can present with episodic inspiratory and expiratory wheezing, respiratory distress, and anxiety.

Features that distinguish it from asthma include sudden onset and abrupt termination, lack of response to asthma therapy, prominent neck discomfort, lack of hypoxemia, and immediate relief of wheezing upon intubation.

Question 5

Heliox

Answer 5

Mixture of helium and oxygen with a density ~1/3 that of air

Use of heliox reduces airflow resistance by reducing the gaseous viscosity.

Question 6

Ipratropium bromide in the treatment of asthma

Answer 6

An antimuscarinic

Addition of ipratropium bromide is equivalent to addition of salmeterol (LABA) to albuterol (SABA) therapy.

Question 7

Fluids in status athmaticus

Answer 7

Euvolemia should be targeted,

however aggressive fluid administration and use of mucolytics is not recommended in treating status asthmaticus.

Question 8

Best volatile ansthetic for status asthmaticus sedation

Answer 8

Isoflurane currently holds this position due to its minimal depression of cardiovascular parameters and lower risk of arrhythmias

Question 9

Permissive hypercapnia in status asthmaticus

Answer 9

In order to obtain safe ventilation pressures for a patient in status, you may need to allow hypercapnia to a blood pH of ~7.2, pCO2 < 90 mmHg. When necessary, pH can be managed pharmacologically.

As long as you are achieving good >90% oxygen saturation, this is okay in the acute setting.

The risk of barotraumatic complications in status asthmaticus outweights the risk of mild acidemia.

Question 10

Ketamine in status asthmaticus

Answer 10

Its bronchodilation makes it an attractive agent for sedation,

However, its CNS effects, tachycardia, and hypertension limit its use.

Question 11

Recommended initial ventilator settings for a patient who presents in status asthmaticus

Answer 11

TV 6 mL/kg

RR 12

Flow rate 100 mL/min

PEEP 5 cm H2O

Question 12

If vocal cord dysfunction is suspected as the etiology of respiratory distress in a patient, what is the next best step?

Answer 12

Laryngoscopy

This is the definitive diagnostic.

Question 13

Treatment of diagnosed vocal cord dysfunction

Answer 13

• Symptomatic management
  
  • Speech therapy
  • Relaxation techniques
• Treatment of underlying etiology:
  
  • SSRI for anxiety
  • Intranasal corticosteroids for postnasal drip
  • PPI for GERD