The Essential is Rapid Recovery's tradename for our basic IV therapy/IV drip package, which is one full liter of Ringer's Lactate.
That probably doesn't tell you much, so we'll explain.
You've probably heard of "normal saline". You might have been watching a show like ER or Grey's Anatomy and heard a doctor say "one liter of NS, stat". That means the patient is going to get a liter of normal saline, by IV, now. Normal Saline is exactly what it says it is: salt water. There's not much to it. It's 0.9% salt, in sterile water.
We don't use it, unless we're infusing someone with specific allergies to something in Ringer's Lactate (very very rare), or we're using a unique medicine for a particular patient which calls for infusion into normal saline. One the shows with better medical experts, or shows where the hospital isn't some cheap dive, you'll hear "a liter of Ringer's".
We use Ringer's Lactate. Ringer's is called a "balanced fluid", because the specific gravity of it (basically the density of the materials dissolved in the water) is much closer to your blood than salt water is, and the osmolarity (passing across barriers) of it is closer to your blood than normal saline. It's "isotonic", which means it has the same concentration of solutes as your blood.
When your body is dehydrated, there's a 100% chance you aren't just lacking fluids, or salt (which is an electrolyte), you're missing lots of electrolytes.
Ringer's isn't just salt in water. It's water with Potassium chloride, calcium chloride, sodium chloride, and sodium lactate. The best way to think of it is "more ingredients that your body needs, instead of just salt". With normal saline you'll get the water, and the salt, but nothing in NS is going to help you replace the potassium you're missing (lack of which leads to muscle spasms, restless leg syndrome, etc..), or the calcium your body has burned through either working out or drinking. In almost every single IV situation, Ringer's is better than Normal Saline.
It's a little more expensive for us than normal saline, but we wouldn't really feel right making a dollar more a treatment and knowing that we were giving you something we wouldn't want for ourselves.
So, there you go. Now you know way more about The Essential, Normal Saline, and Ringer's Lactate than you ever needed or wanted to know.