Final answer:
In the case of a patient experiencing severe symptoms following an Adenosine IV push, immediate initiation of cardiopulmonary resuscitation (CPR) is the next step, along with preparing for advanced life support measures.
Step-by-step explanation:
If a patient who was given 12mg Adenosine rapid IV push develops severe chest pain, shows changes in rhythm, has a non-obtainable blood pressure, a weak pulse, and experiences changes in the level of consciousness (LOC), the next step should be to initiate cardiopulmonary resuscitation (CPR). This response is necessary due to the signs indicating that the patient could be in cardiac arrest. Prompt CPR can manually compress the heart to push blood through the pulmonary and systemic circuits, essential for oxygen delivery, especially to the brain.
While performing CPR, medical personnel must also ready advanced life support measures, which may include defibrillation, intubation, and the possible administration of emergency medications. Medical staff should continuously monitor the patient's cardiac rhythm and vital signs and prepare for potential further interventions based on the evolution of the clinical situation.