Hemodynamic responses to metaboreflex activation: insights from spinal cord-injured humans

This investigation was conducted to study the hemodynamic consequences of spinal cord injury (SCI) during post-exercise muscle metaboreflex activation in SCI subjects. The hemodynamic response to metaboreflex recruitment was assessed in ten SCI patients and nine healthy controls (CTL) by means of impedance cardiography. The main results were (1) the metaboreflex-induced blood pressure rise was blunted in SCI subjects compared with normals, (2) the CTL group achieved the blood pressure response via cardiac output increase, while the SCI subjects could not use this mechanism, (3) the CTL group was able to enhance stroke volume and ventricular filling rate in response to the metaboreflex, whereas the SCI group could not. It was concluded that in healthy individuals, the hemodynamic response to the metaboreflex is an integrated phenomenon that depends mainly on a flow-mediated mechanism, whereas in SCI individuals the reduced venous return impairs this mechanism.