Seizures and blood pressure
Yes, seizures can affect autonomic function including blood pressure. Such symptoms can even result in death. Note though that not all seizures are the same: there are many different types with many different causes, and they can affect different parts of the brain. There can also be different effects before, during, and post-seizure.

The effects described seem to be more related to overall discharge rates rather than synchronous firing in the periphery per se. The autonomic nervous system does not directly control heart rate, for example, but rather modulates the rate. The heart beat or vasculature would not entrain to any sort of seizure activity, for example, because the neurotransmitters involved in autonomic regulation of heart rate and blood pressure are comparatively slow-acting relative to the rate of seizure activity (essentially those functions are taking a moving average of neural input, rather than responding specifically to each impulse).

The relationship between autonomic function and seizures need not be unidirectional, either; circulatory changes can also be triggers for seizures.

References



Devinsky, O. (2004). Effects of seizures on autonomic and cardiovascular function. Epilepsy currents, 4(2), 43-46.

Nei, M. (2009). Cardiac effects of seizures. Epilepsy currents, 9(4), 91-95.

Penfield, W., von Sántha, K., &amp; Cipriani, A. (1939). Cerebral blood flow during induced epileptiform seizures in animals and man. Journal of Neurophysiology, 2(4), 257-267.