Imagine a case study where a patient experiences a severe asthma attack. Discuss the rationale behind using an Adrenergic Agonist in the management of this emergency situation. Address the pathophysiology of asthma, the mechanism of action of Adrenergic Agonists, and the potential benefits and limitations of this therapeutic approach. How might a Nurse Practitioner determine the appropriate dosage and route of administration in this critical situation?