Fluids and Electrolytes

  • Michalakis Savva


In this chapter, the basic physiology of fluid and electrolytes is reviewed before attempting to examine how pathological conditions affect homeostasis. Rules have been established based on the phenomenon of osmosis to help you better comprehend physiological parameters that govern the movement of fluids between body compartments. Some useful tips for the correct diagnosis of fluid and electrolyte imbalances are also discussed. The first part of the chapter is about understanding the interplay between electrolyte deficit and fluid shifts and making the right decision for appropriate clinical interventions. Through various practice examples, you will learn how to calculate the volume fraction of a replacement fluid that is distributed to different body fluid compartments and how cells manage to counteract a hypotonic or hypertonic environment. The second part of the chapter discusses osmotic diuretics and calculations related to electrolytes. You are given the opportunity to learn how to calculate electrolyte doses expressed in the units of Eq and convert those into actual salt mass.


Homeostasis Fluid compartment Intracellular Interstitial Extracellular Maintenance fluid Replacement fluid Crystalloid Colloid Plasma expander Osmolarity Osmotic diuretics Equivalent weight 

Supplementary material

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Lesson 10.1

Fluids and electrolytes—Part I: Electrolyte deficits and fluid shifts. Description: (a) Major body fluid compartments and their composition. (b) Intracellular and extracellular concentrations of important crystalloids. (c) Functional difference between crystalloids and colloids related to in vivo water sorption. (d) Electrolyte disturbances will lead to fluid shifts. (e) Colloid solutions increase plasma volume. (f) Isotonic and hypertonic saline solutions increase plasma extracellular fluid volume. (g) Isotonic glucose and hypotonic saline solutions increase intracellular fluid volume. (h) Calculating plasma volume increase upon administration of a colloid solution. (i) Actions that cells may take to maintain homeostasis when they are exposed to non-physiological osmolarity environment. (j) Maintenance and replacement solutions (MP4 2085732 kb)

Lesson 10.2

Fluids and electrolytes—Part II: Osmotic diuretic. Description: (a) Properties of osmotic diuretics. (b) Similarities and differences of osmotic diuretics with plasma expanders (MP4 383862 kb)

Lesson 10.3

Fluids and electrolytes—Part III: g-EW and electrolyte concentration. Description: (a) The concept of gram Equivalent Weight (g-EW). (b) Calculating the EW and Eq of substances. (c) Converting grams of ions and ionic compounds into Eq and vice versa. (d) Calculating the Eq of ions in solutions that are made by multiple common ions (MP4 1062141 kb)

Copyright information

© Springer Nature Switzerland AG 2019

Authors and Affiliations

  • Michalakis Savva
    • 1
  1. 1.School of PharmacySouth UniversitySavannahUSA

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