Absolutely, fluid/electrolyte replacement is essential for scouring calves. I'll often also add a human dose of Metamucil to the electrolytes when I'm treating a scouring calf - it 'gels', and helps slow gut transit time a bit, allowing for better chance to absorb fluid/electrolytes, rather than having 'em just run straight through. There used to be a commercial product that contained psyllium fiber, but haven't seen it in years(but I haven't looked, either).
Revive was the brand of electrolyte replacement I preferred, back when I was in practice; not sure if it's still on the market or not. ReSorb and others have been around for decades, and may be just as good.
There are 'homemade' recipes - and I've used 'em in a pinch - something like this: 1 can of beef consomme(protein source), 1 packet of fruit pectin(dextrose source) 1tsp baking soda, 1tsp salt substitutes(KCl - potassium source), water to bring volume to 1/2 gallon.
In the past, we used to recommend stopping feeding milk replacer to scouring calves - but they NEED that protein to drive their immune system, and particularly at this time of year, they need the energy from sugars/fats in the milk replacer just to maintain body temperature. So... the recommendation to withhold MR is not valid anymore; we just recommend working in additional feedings of electrolyte solution between MR feedlings to maintain hydration/electrolyte balance.
Your veterinarian can recommend antimicrobial therapy, based on what has worked best for previous cases. Don't waste your time with penicillin or LA-200; they're unlikely to be effective against most enteric pathogens - and totally ineffective against viruses or protozoa(Crypto, coccidia).