Final answer:
The nurse should assess the patient's bleeding source, which could indicate retained placental fragments or a full bladder. Promptly assist the patient to void and monitor vital signs closely. Report findings to an obstetrician or midwife and evaluate the perineal laceration for infection or hematoma.
Step-by-step explanation:
A postpartum patient with a third-degree perineal laceration experiencing a temperature of 37.8 ℃ (100 ℉) and a firm fundus deviated to the right with a gush of blood upon ambulation requires immediate nursing intervention. The priority action the nurse should take is to assess the source of bleeding. Although postpartum uterine contractions limit blood loss from the detachment of the placenta and lochia rubra is expected in the initial postpartum days, a deviation of the fundus and a gush of blood could signify retained placental fragments or bladder distension due to a full bladder, which can displace the uterus and impede uterine contractions leading to increased bleeding.
The nurse should prompt the patient to void to see if the bladder is contributing to the fundal displacement and excessive lochia. All findings should be quickly reported to the obstetrician or midwife for further assessment and management, which may include examination of the patient's uterus or performing an ultrasound, to ensure no fragments are left inside that could cause an infection or hemorrhage. Additionally, the nurse should monitor vital signs closely, maintain the intravenous line for potential rapid administration of fluids or medications, and evaluate the perineal laceration site for signs of infection or hematoma formation as sources of fever.