An otherwise healthy 25-year-old pregnant woman in the hospital in active labor. She requests an epidural nerve block, which is an injection of an anesthetic into the epidural space around the spinal cord. Epidural nerve blocks for labor pain are injected near thoracic nerve 10 (T10, a spinal nerve). The injection will lead to the blockade of signals from the afferent neurons of the uterus, thereby reducing the sensation of pain associated with labor contractions. These afferents enter the spinal cord between T10 and L3 (lumbar nerve 3). The injection can also lead to sympathetic blockade for sympathetic efferent neurons exiting at the regions of the spinal cord below T10. The sensory afferent blockade works for the patient and labor pain diminishes, however, after administration of the epidural medication, the patient begins to experience the following symptoms: . Decreased blood pressure (MAP) Lightheadedness and dizziness Tachycardia= increased heart rate, beyond that, brought on by the stress of labor The new mom stayed in the hospital for 24 hours after giving birth. A friend came to see her and the baby at the hospital, so she sits on the side of the bed with her feet dangling just above the floor while visiting and showing off her beautiful baby. A few minutes after she changes from sitting with feet on the bed to sitting with feet hanging down, she looks down and realizes that her ankles, which were completely normal before she moved to the sitting position with legs down, now are extremely swollen. She is healthy and the effects of the epidural and alpha adrenergic agonist have worn off (are not affecting her anymore). 5. What combination of factors has caused her ankle edema to develop?