Coconuts! An exotic and delicious treat. When thinking of them, you may think of Pina Coladas or tropical islands, but would you ever think of it as a replacement for saline solution?
During World War II, when there was a shortage of saline solution, coconut water was inserted intravenously, and it has been used successfully on a man in an emergency situation in the Solomon Islands when nothing else was available.
In 1954, three doctors (Eisman, Lozano and Hager), all combined the findings from their research. Between them, they had administered coconut water intravenously to 157 patients in Thailand, the USA and Honduras. Out of 157 patients, only 11 had reactions to the coconut water. However, is this really an acceptable alternative to saline solution? 
In very dire cases, possibly. One case in the involved a man who had recently suffered a stroke in the Solomon Islands. He had difficulty in swallowing, choked on both liquids and solids and repeatedly vomited them up. He was rehydrated with regular IV fluids, and fed via a tube directly into his stomach. After 36 days in hospital, he could no longer tolerate the feeding tube. Unfortunately, the hospital had run out of IV fluids, and because of its remoteness, would not get supplies for two days. He was given coconut water intravenously and left the hospital on day 39 in much better health. 
Why is coconut water actually even considered an alternative? Coconut water is not identical to the plasma of blood as some people believe it to be. Human blood is about 55 per cent salty water, and about 45 per cent cells. The salty water, called plasma, is a clear slightly yellowish liquid, with high levels of sodium, low levels of potassium, and trace amounts of other minerals. Genuine intravenous fluids are manufactured to have high sodium and low potassium.
Coconut water it is closer to the liquid inside the red blood cells, with low sodium and high potassium, which is the exact opposite. 
Coconut water is loaded with calcium and magnesium, which means it’s not suitable for patients with kidney failure, severe burns, etc. Another problem is that it is much more acidic than human plasma. The bottom line is that coconut water is not identical to human plasma. Therefore, only in extreme situations would it be an acceptable substitution.
But while coconut water isn’t a safe alternative for an IV, some doctors are recommending it to patients as an oral rehydration therapy. People with conditions like colitis from Crohn’s disease and gastroenteritis can lose a lot of water in diarrhea; coconut water can help replenish their bodies. 
 Kruszelnicki, Karl S. “Coconut Water as Blood Plasma Alternative?” ABC News, Australian Broadcasting Corporation, 9 Dec. 2014, http://www.abc.net.au/science/articles/2014/12/09/4143229.htm.
 Barclay, Eliza. “Coconut Water To The Rescue? Parsing The Medical Claims.” NPR, NPR, 15 Aug. 2011, http://www.npr.org/sections/health-shots/2011/08/15/139638930/saved-by-the-coconut-water-parsing-coconut-waters-medical-claims.
 Image credit to Pexels https://www.pexels.com/photo/beach-coconut-delicious-food-322483/