Saline solutions hypertonic sodium chloride

Hypertonic sahne is actively excluded from an intact BBB and also acts to draw water into the intravascular space by the creation of a sodium gradient. Various concentrations have been evaluated, with continuous sodium chloride infusions ranging from 3% to 9%, and bolus infusions up to 23.4% administered over 20 minutes in a 30 mL solution. When a continuous infusion is used, the serum sodium is typically titrated to the 155-160 range. Sodium levels above this range raise the concern for seizures and other toxic side effects. Hypertonic saline may hold an advantage over mannitol, as it has been found in animal models to decrease edema in both... 

Fluids can be classified further according to their tonicity. Isotonic solutions (i.e., normal saline or 0.9% sodium chloride [NaCl]) have a tonicity equal to that of the ICF (approximately 310 mEq/L or 310 mmol/L) and do not shift the distribution of water between the ECF and the ICF. Because hypertonic solutions (i.e., hypertonic saline or 3% NaCl) have greater tonicity than the ICF (greater than 376 mEq/L or 376 mmol/L), they draw water from the ICF into the ECF. In contrast, hypotonic solutions (i.e., 0.45% NaCl) have less tonicity than the ICF (less than 250 mEq/L or 250 mmol/L) leading to an osmotic pressure gradient that pulls water from the ECF into the ICF. The tonicity, electrolyte content, and glucose content of selected fluids are shown in Table 24—3. 

Commonly administered LVPs include such products as Lactated Ringers Injection USP, Sodium Chloride Injection USP (0.9%), which replenish fluids and electrolytes, and Dextrose Injection USP (5%), which provides fluid plus nutrition (calories), or various combinations of dextrose and saline. In addition, numerous other nutrient and ionic solutions are available for clinical use, the most popular of which are solutions of essential amino acids or lipid emulsions. These solutions are modified to be hypertonic, isotonic, or hypotonic to aid in maintaining both fluid, nutritional, and electrolyte balance in a particular patient according to need. Indwelling needles or catheters are required in LVP administration. Care must be taken to avoid local or systemic infections or thrombophlebitis owing to faulty injection or administration technique. 

Despite their apparent efficacy, the usefulness of sodium chloride solutions in the treatment of edematous corneas with a traumatized epithelium appears to be limited. The intact corneal epithelium exhibits limited permeability to inorganic ions. In the absence of an intact epithelium the cornea imbibes salt solutions, which reduces the osmotic effect. In the management of corneal edema associated with traumatized epithelium, hypertonic saline solutions may be of limited value due to their increased ability to penetrate the epithelial barrier. 

Unfortunately, beneficial outcome data attributable to administration of these hypertonic solutions also have been lacking. Most of these studies were conducted in prehospital and emergency department settings using 250 mL 7.5% sodium chloride with or without 6% dextran-70. A meta-analysis of randomized, controlled trials found no statistical difference between the survival rates of patients receiving the hypertonic saline solutions and those receiving standard isotonic crystalloid solutions.Part of the explanation for this finding may... 

A 0.90% (0.15 M) sodium chloride solution is known as a physiological saline solution because it is isotonic with blood plasma that is, it has the same concentration of NaCl as blood plasma. Because each mole of NaCl yields about 2 mol of ions when in solution, the solute particle concentration in physiological saline solution is nearly 0.30 M. Five-percent-glucose solution (0.28 M) is also approximately isotonic with blood plasma. Blood cells neither swell nor shrink in an isotonic solution. The cells described in the preceding paragraph swell in water because water is hypotonic to cell plasma. The cells shrink in 5%-urea solution because the urea solution is hypertonic to the cell plasma. To prevent possible injury to blood cells by osmosis, fluids for intravenous use are usually made up at approximately isotonic concentration. 

Some of the best examples of osmosis are those associated with living organisms. For instance, if red blood cells are placed in pure water, the cells expand and eventually burst as a result of water that enters through osmosis. The osmotic pressure associated with the fluid inside the cell is equivalent to that of 0.92% (mass/volume) NaCl(aq). Thus, if cells are placed in a sodium chloride (saline) solution of this concentration, there is no net flow of water through the cell membrane, and the cell remains stable. Such a solution is said to be isotonic. If cells are placed in a solution with a concentration greater than 0.92% NaCl, water flows out of the cells, and the cells shrink. Such a solution is said to be hypertonic. If the NaCl concentration is less than 0.92%, the solution is hypotonic, and water flow s into the cells. Fluids that are intravenously injected into patients to combat dehydration or to supply nutrients must be adjusted so that they are isotonic with blood. The osmotic pressure of the fluids must be the same as that of 0.92% (mass/volume) NaCl. 

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