Therapeutic efficacy of adrenergic agents on systemic and spinal hemodynamics in an acute cervical spinal cord injury rodent model

Background: Cervical spinal cord injury usually results in cardiorespiratory dysfunctions due to interruptions of the bulbospinal pathways innervating the cervical phrenic motoneurons and thoracic sympathetic preganglionic neurons. Purpose: The present study aimed to evaluate the therapeutic effects of adrenergic agents on systemic and spinal hemodynamics during acute cervical spinal cord injury. Study design: In vivo animal study. Methods: The cardiorespiratory function and spinal cord blood flow and oxygenation level were monitored in response to cervical spinal cord contusion and intravenous infusion of three types of adrenergic agents (phenylephrine, dobutamine, and norepinephrine). Results: Cervical spinal cord contusion resulted in immediate reduction of respiratory airflow, arterial blood pressure, and spinal cord blood flow. The arterial blood pressure and spinal cord blood flow remained lower than the preinjury value in contused animals infused with saline at 60 min postinjury. Infusion of phenylephrine (500, 1000, and 2000 mu g/kg) and norepinephrine (125, 250, and 500 mu g/kg) significantly increased the arterial blood pressure, while only norepinephrine augmented the spinal cord blood flow. Conversely, dobutamine (1000 and 2000 mu g/kg) reduced both arterial blood pressure and spinal cord blood flow. Notably, administration of adrenergic agents tended to increase spinal cord hemorrhage in contused animals. Conclusions: Infusion of norepinephrine can effectively maintain the blood pressure and improve spinal cord blood flow during acute spinal cord injury.