Electrolytes are essential for proper hydration. All too often I'll see individuals state they're drinking copious amounts of water --1-1.5gal per day. Yet, if they have any recent copy(ies) of their CBC/Chem panel, their Albumin will be encroaching >5g/dL, their Na nearly bottomed out and their osmotic concentrations are indicative of insufficient hydration/dehydration.
If they're chugging copious amounts of water and pissing several times throughout the day This can create an individual to piss their Na (sodium) in the dirt, which shits on hydration. If they're sweating during the course of the day, this too will push their Na further down. Especially if they're not getting in sufficient electrolytes.
In the context of increased HR, insufficient hydration/dehydration increases cardiac output via increase HR to maintain adequate systemic blood perfusion.
The OP may be sufficiently hydrated in which case would be unrelated to his RHR. If he's on the school of routine phlebotomizing pushing his Fe in the dirt, this can increase his RHR, too.