Abstract 1383: Noninvasive Transcutaneous Bionic Baroreflex System Prevents Severe Orthostatic Hypotension in Spinal Cord Injury
Background: Central baroreflex failure in spinal cord injuries results in serious orthostatic hypotension. Although various interventions such as salt loading and adrenergic agonists have been attempted to treat orthostatic hypotension, such interventions can neither restore nor reproduce the functioning of the native vasomotor center. We proposed a novel therapeutic strategy, i.e., an artificial feedback control system (bionic baroreflex system: BBS) capable of automatically regulating sympathetic vasomotor tone (Circulation 1999, 2002, 2004). Since somatic inputs are known to affect sympathetic drive in patients, we examined if the transcutaneous noninvasive electrical stimulation can be used to feedback control arterial pressure (AP) in spinal cord injury.
Methods and Results: We identified skin regions (bilateral inguinal areas), windows of somato-splachnic reflex, capable of increasing AP in response to electrical stimulation. By a binary white noise approach with stimulation frequency 0 – 40 Hz (0.3 msec, 40 mA), we estimated the dynamic properties of the stimulation-AP responses (Fig. A⇓) and then determined the transfer function required for the BBS. We examined the performance of BBS by imposing orthostatic stress (passive upright position). The orthostatic stress decreased AP to 45 mmHg (Fig. B⇓). But the activation of BBS immediately restored AP to a prespecified level (65 mmHg) in <20 sec. The patient who had had serious orthostatic hypotension was totally free from any hypotensive symptoms.
Conclusion: Transcutaneous bionic baroreflex system is noninvasive and capable of stabilizing AP in spinal cord injury with central baroreflex failure.