Final answer:
The nurse should first take the patient's vital signs.
Step-by-step explanation:
The nurse should take the action of taking the patient’s vital signs first. The presence of new bright-red drainage on the dressing may indicate bleeding or hemorrhage, which could be a potentially serious complication after a laparotomy for a small bowel obstruction. Taking the patient’s vital signs will help assess their overall condition and provide important data for the nurse to make further decisions.