A 25 year old patient with asthma arrives at the emergency depament complaining of extreme shoness of breath. He has been compliant with his medications, which are metaproterenol and inhaled betamethasone. Over the past 6 hours, his wheezing and shoness of breath have become increasingly severe. At present, his blood pressure is 136/84 mm Hg and with deep inspiration falls to 116/56 mm Hg. His pulse is 126/min, and respirations are 32/min and labored. There is retraction of the sternocleidomastoid muscles with inspiration. There are soft wheezes and poor air movement diffusely throughout both lung fields. His peak expiratory flow rate is 60 L/min, and he is immediately staed on an albuterol nebulizer and given IV hydrocoisone. His aerial blood gas revealed a pH of 7.55, pCO2 of 21 mm Hg, and a pO2 of 60 mm Hg. Twenty minutes later, a repeat peak flow rate is still 60 L/min. A repeat aerial blood gas reveals that his pH is now 7.46, his pCO2 is now 34 mm Hg, and his pO2 is 64 mm Hg. Which of the following is the most appropriate next step in management?
This patient is having a very severe asthmatic attack, as demonstrated by his severe shoness of breath, use of accessory muscles of respiration, and variation in blood pressure with breathing (due to establishing a very negative intrathoracic pressure with forced attempts at inspiration). The initial pO2 is markedly decreased at 60 (compared to the normal 100) mm Hg. His pCO2 is also decreased at 21 mm Hg initially, due to "blowing off CO2" with his increased respirations while trying to get enough oxygen. This causes his respiratory alkalosis with pH 7.55. He is then treated, but the treatment improves his pO2 only slightly. Despite this, his pCO2 rises, and his pH returns toward normal. This does not mean he is getting better. Instead, we are seeing worsening respiratory failure as his ability to ventilate decreases, causing the inappropriate rise in pCO2 even though he is still very badly hypoxic. This patient should therefore be prepared for possible intubation if there is not immediate improvement. Epinephrine no longer is used in the management protocols of acute asthma because of its high rate of toxicity. Administering 100% oxygen may be an adjunctive therapy, but at this point the patient is probably saturating above 90% anyway. Ref: Corbridge T., Hall J.B. (2005). Chapter 40. Status Asthmaticus. In J.B. Hall, G.A. Schmidt, L.D. Wood (Eds), Principles of Critical Care, 3e.
Administer IV epinephrine
Administer 100% oxygen a tight fitting face mask
Administer subcutaneous epinephrine
Prepare for intubation