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TEST TAKING TIPS

Test Taking Tips

  • Manifestations of trace element deficiencies (eg, chromium, zinc, copper, etc) tend to be a recurring theme on the test.

  • Know the basics of TPN. Learn the indications, content, and adverse effects.

  • Do not confuse the ECG findings associated with various electrolyte abnormalities.

FLUIDS

Name the 2 major body fluid compartments:

  • Intracellular and extracellular

Extracellular fluid is divided into these 2 subcompartments:

  • Interstitial fluid and intravascular fluid

Mnemonic for the composition of body fluid:

  • 60, 40, 20; 60% total body weight fluid, 40% total body weight intracellular, 20% total body weight extracellular

Approximate percentage of body weight that is fluid:

  • 60%

Approximate percentage of body fluid that is extracellular:

  • 33%

Approximate percentage of body weight that is intracellular:

  • 66%

Percentage of extracellular fluid within the vascular compartment in the venous system:

  • 85%

Percentage of extracellular fluid within the vascular compartment in the arterial system:

  • 15%

The approximate percentage of body weight that blood accounts for in an adult:

  • 7% (so to estimate how many liters of blood in a 70-kg man; 0.07 × 70 kg = 5 liters)

Requirement of water per 24-hour period:

  • ~30 to 35 mL/kg

FIGURE 7-1.

Chemical composition of body fluid compartments. (Reproduced form Brunicardi FC, Anderson DK, Billiar TR, et al. Schwartz's Principles of Surgery. 9th ed. http://www.accessmedicine.com. Copyright © The McGraw-Hill Companies, Inc. All rights reserved.)

Requirement of sodium per 24-hour period:

  • ~1 to 2 mEq/kg

Requirement of chloride per 24-hour period:

  • ~1.5 mEq/kg

Requirement of potassium per 24-hour period:

  • ~1 mEq/kg

Name the sources and the amount of normal daily water loss:

  • Respiratory losses: 500 to 700 cc

  • Sweat: 200 to 400 cc

  • Urine: 1200 to 1500 cc

  • Feces: 100 to 200 cc

Name the sources and the amount of insensible fluid loss:

  • Skin: ~300 cc/24 h

  • Breathing: 500 to 700 cc/24 h

  • Feces: 100 to 200 cc/24 h

General rate of fluid loss during an open abdominal procedure in the absence of measurable blood loss:

  • 0.5 to 1.0 L/h

Name the sources and the amount of normal daily electrolyte loss:

  • Chloride: 150 mEq, sodium: 100 mEq, potassium: 100 mEq

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