I was wondering if there may be an advantage to doing a faster rather than slower infusion within the window of safety for infusion rate. I did find this, "It does not seem to matter how fast or slow the fluids are run in, everyone seems to develop their own preferences," from Dr. Bell who has expertise in IV saline from ME/CFS, so I think it answers my question.
https://www.prohealth.com/library/dr-david-bell-on-intravenous-fluid-as-a-treatment-for-me-cfs-23713
I did do the IV saline yesterday, 1L over 2.5 hours starting around noon. Unfortunately, it didn't seem to make a difference for me, if anything, I felt more fatigued that afternoon and into the evening. It did increase my systolic and diastolic BP by about 15 mm/hg each (usually I am low 80s/ low 50s. My ADH is low and I drink about 4-6 L of water a day, so I was hoping to get a response. I do not, however, have POTS.