If the systolic blood pressure falls below 90 mmHg within days of the injury, blood supply to the spinal cord may be reduced, resulting in further damage. Thus it is important to maintain the blood pressure which may be done using intravenous fluids and vasopressors. Vasopressors used include phenylephrine, dopamine, or norepinephrine. Mean arterial blood pressure is measured and kept at 85 to 90 mmHg for seven days after injury. The treatment for shock from blood loss is different from that for neurogenic shock, and could harm people with the latter type, so it is necessary to determine why someone is in shock. However it is also possible for both causes to exist at the same time. Another important aspect of care is prevention of insufficient oxygen in the bloodstream, which could deprive the spinal cord of oxygen. People with cervical or high thoracic injuries may experience a dangerously slowed heart rate; treatment to speed it may include atropine.