Final answer:
The first action the nurse should take when noticing a soaked perineal pad and blood under the client's buttocks is to assess the client's vital signs. This is crucial to identify and manage a potential postpartum hemorrhage, a potentially life-threatening condition.
Step-by-step explanation:
If the nurse notes that the perineal pad is soaked with blood and there is blood underneath the client's buttocks, the first action the nurse should take is a) Assess the client's vital signs. This action is critical as it helps determine the client's hemodynamic status and the presence of potential postpartum hemorrhage, which can be a life-threatening emergency. Prompt assessment of vital signs allows for timely intervention. After assessing and stabilizing the patient's vital signs, the nurse would typically document the findings, change the perineal pad, observe for further bleeding, and notify the healthcare provider to further manage the situation.