A 0.9% solution of saline is isotonic and is therefore called physiological or “normal.” The fluid contains a marked surplus of chloride ions and no buffer and, hence, infusion of 2 liters or more of the fluid causes hyperchloremic metabolic acidosis.
In adults, normal saline should be reserved for patients with hypochloremic metabolic alkalosis, as in disease states associated with vomiting. The fluid has a more accepted role for perioperative fluid therapy in children where the risk of subacute hyponatremia is a more serious concern than in adults.
When infused in healthy volunteers normal saline might cause abdominal pain, which is not the case for lactated Ringer’s. The fluid also has more undesired effects, including acidosis, when used during surgery.
Normal saline is excreted more slowly than both lactated and acetated Ringer’s solution , increasing the volume effect (“efficiency”) of the fluid to be about 10% greater compared with the Ringer’s solutions.
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