Saline is simply a solution of sodium chloride (say that 3 times fast...)
Essentially, salt in water.
You likely have some in your house! Eye drops, contact lens solution, nasal irrigation bottles, and even simple first aid wound preparations. In your veterinary hospital, you may have 0.9% NaCl (sodium chloride) on your shelf as an isotonic crystalloid fluid. Salt and water...
Like everything in life (sarcasm) if some is good...more is better! So if a little saline is good, is more saline better? Specifically, what are the benefits of hypertonic saline?
First, let's define what hypertonic saline is? While the commonly used veterinary crystalloid sterile saline is a 0.9% concentration, hypertonic saline is a solution that is greater than 0.9%. Common medical preparations include ~7% and 23.4% hypertonic saline.
Let's review 3 reasons why you should carry hypertonic saline on your veterinary clinic shelf:
1) Paraphimosis: Because of its hypertonicity, hypertonic saline can be used to reduce paraphimosis or prolapses of the vagina or rectum. As a hypertonic solution, it can draw fluid out of swollen areas and towards the hypertonic solution. By applying it topically, it reduces the size of the prolapse and assists in returning the tissue to normal.
2) Intracranial hypertension: While mannitol is a common treatment for intracranial hypertension, hypertonic saline can also be administered, especially in patients that are also hypovolemic. As hypertonic saline is hyperosmotic but does not cross the blood-brain barrier, it will draw water from the brain reducing intracranial pressure as well as decrease blood viscosity to enhance cerebral blood flow and oxygenation. It is also theorized to have immunomodulatory effects beneficial in reducing secondary injuries that occur due to the inflammatory response following traumatic brain injury (TBI).
3) Small volume resuscitation: As compared to an isotonic crystalloid, the use of hypertonic saline for resuscitation allows the clinician to use small dosing for rapid volume expansion. As compared to large volume isotonic crystalloids, hypertonic saline is less likely to contribute to volume overload or interstitial edema. Another theoretical benefit includes immunomodulatory effects to decrease reperfusion injury during resuscitation.
Does hypertonic saline have side effects or potential concerns? Certainly. They can range from fluid overload to hypernatremia, or even hyperosmolality. More importantly, hypertonic saline can be life saving and for this reason should be a fluid you stock on your shelves.
So, consider carrying hypertonic saline in addition to your 0.9% saline on your veterinary clinic shelf - it's inexpensive and may be life-saving!
Dr. Garret Pachtinger, DACVECC