Elevated BP due to dehydration?

Today I am 38w. At 36+4, my BP was unusually elevated suggesting I may have pre-eclampsia. I had a clean catch urinalysis done (twice), blood work and an ultrasound and everything has came back perfect. I have also not had any symptoms besides an elevated BP that would suggest pre-eclampsia. The hospital gave me a saline/sodium drip and my BP immediately went down. The OB on call said I was dehydrated but I consistently drink 2-3 liters of water a day. After this situation, my midwife suggested drinking 1 liter of Gatorade on top and of my water intake to replenish my electrolytes. Today, my BP seemed to rise again and my midwife asked me to switch my water intake to 1 liter and drink 2-3 liters of Recharge (a healthier version of Gatorade). 
Has anyone ever experienced a change in BP due to dehydration or depleted electrolytes? I'm praying my second round of blood work and third urine catch will be the same good result as the past and we can continue with our birth plan with our midwife. Hoping someone else may have had this experience??