Upon completion of the chapter the reader will be able to

1. Estimate the volumes of various body fluid compartments.

2. Calculate the daily maintenance fluid requirement for patients given their weight, and gender.

3. Differentiate among currently available fluids for volume resuscitation.

4. Identify the electrolytes primarily found in the extracellular and intracellular fluid compartments.

5. Describe the unique relationship between serum sodium concentration and total body water (TBW).

6. Review the etiology, clinical presentation, and management for disorders of sodium, potassium, calcium, phosphorus, and magnesium.


O Total body water (TBW) is approximately 50% of lean body weight in normal females and 60% of lean body weight in males. TBW is comprised of the intra-cellular fluid (two-thirds of TBW) and the extracellular fluid (one-third of TBW). The extracellular fluid is made up of two major fluid subcompartments: the interstitial fluid and the intravascular fluid.

Therapeutic fluids include crystalloid and colloid solutions. The most commonly used crystalloids include normal saline, hypertonic saline, and lactated Ringer's solution. Examples of colloids include albumin, the dextrans, hetastarch, and fresh-frozen plasma.

The calculated serum osmolality helps determine deviations in TBW content.

^ Concentrated electrolytes (potassium chloride [KCl], potassium phosphate, and sodium chloride [NaCl] greater than 0.9%) should not be stored in patient care areas as a patient safety measure.

® Hyponatremia is a very common finding in hospitalized patients and is defined as a serum sodium concentration below 136 mEq/L (136 mmol/L).

IV potassium infusions running at rates of greater than 10 mEq/h require cardiac monitoring.

Calcium gluconate is the preferred peripherally infused calcium supplement because it is less irritating to the veins. Calcium chloride (CaCl) must be infused via a central line.

Severe hypophosphatemia can result in impaired diaphragmatic contractility and acute respiratory failure.

Serum magnesium concentrations do not correlate well with total body magnesium stores. For this reason, magnesium supplementation is often given empirically to critically ill patients.

Blood Pressure Health

Blood Pressure Health

Your heart pumps blood throughout your body using a network of tubing called arteries and capillaries which return the blood back to your heart via your veins. Blood pressure is the force of the blood pushing against the walls of your arteries as your heart beats.Learn more...

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