Final answer:
The initial nursing action for a client in a postpartum unit who presents with symptoms suggestive of a pulmonary embolism should be to call for medical assistance immediately. This is due to the life-threatening nature of a pulmonary embolism, which requires prompt diagnosis and treatment.
Step-by-step explanation:
If a client in a postpartum unit reports sudden sharp chest pain and dyspnea, and is found to be tachycardic with an elevated respiratory rate, the initial nursing action should be to assess for a potential pulmonary embolism. Since these symptoms could indicate a life-threatening condition, the most immediate and appropriate action would be to call for medical assistance (e.g., call a code, alert the rapid response team, or notify the physician immediately depending on the hospital's protocol). It is critical that the medical team assesses and manages the patient as soon as possible for conditions like pulmonary embolism, which may require emergency interventions such as anticoagulants or other treatments based on the underlying cause. While elevating the legs can assist with venous return, and administering pain medication might provide comfort, both are secondary to the urgent need to address the potential pulmonary embolism.