Ch 40, Fluids, Electrolytes, and Acid Base Balance

This is an excellent video set for this class

Taylor's Fundamentals of Nursing 

Chapter 40, Fluid, Electrolyte, and Acid-Base Balance

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ANATOMY AND PHYSIOLOGY

Body Fluids:

• Water is the most important nutrient of life.
• Water in the body functions primarily to:
• provide medium for transporting nutrients and waste( cell to cell)
• providing medium for transporting hormones, enzymes, platelets, etc...
• facilitate cellular metabolism
• act as solvent
• maintain normal body temp
• facilitate digestion and elimination
• act as tissue lubricant

Body Water and Fluid Compartments:

• water is 50-60% of body weight in healthy person
• fluid is located in two compartments, ICF and ECF
• ICF is fluid within cells, 70% total body water
• ECF fluid outside cells, 30% total body water
• ECF includes two major areas: Intravascular and Interstitial
• Intravascular fluid is the liquid component of blood (plasma, fluid found within vascular system)

Fluid Sources:

• the body obtains water from ingested liquids, food, and as a by-product of metabolism
• the thirst control center in in the hypothalamus
• thirst center is stimulated by intracellular dehydration and decreased blood volume
• fluid intake averages around 2600ml.day
• 1300ml from water
• 1000ml from food
• 300ml from metabolic oxidation

Fluid Losses:

• fluid is lost through sensible and insensible losses
• sensible can be measured
• insensible cannot be measured or seen (vapor, sweat)
• fluid output averages 2500-2900ml per day
• 1500 as urine
• 600ml from skin
• 300 from lungs 
• 200 in feces

Homeostasis Mechanisms:

• adrenal glands secrete aldosterone that helps conserve sodium, helps save chloride and water, causes potassium to be excreted
• ADH

ELECTROLYTES:

• electrolytes are particles that can be broken down into ions 
• an ion is an atom or molecule that carries a charge
• a positively charged ion is a cation
• a negatively charged ion is an anion
• solvents are liquids that hold a substance in a solution
• solutes are substances that are dissolved into solution
• major electrolytes in the ECF:
•  sodium
• chloride
•  calcium
•  bicarb
• major electrolytes in ICF:
• potassium
• phosphorus
• magnesium

Sodium:

• chief electrolyte of ECF
• primary influence outside of cell
• normal serum concentration: 135-145 mEq/L
• Functions of Sodium:
• controls and regulates extracelluar fluid volume
• affects serum osmo
• muscle contraction and nerve impulse transmission
• regulation of acid base balance as sodium bicarb
• loss or gain of sodium usually accompanied by loss or gain of water
• Regulation of Sodium:
• transported out by sodium potassium pump
• affected by salt as well as water intake
• regulated by renin angiotensin aldosterone system
• elimination and reabsorption regulated by kidneys

Potassium:

• major cation of ICF
• primary influence inside the cell
• normal serum concentration 3.5-5 mEq/L
• Function  of Potassium:
• helps control intracellular osmo
• chief regulator of cellular enzyme activity
• electric impulses- nerves, heart, skeletal, intestinal, lung tissue
• regulation of acid base balance
• Regulation of Potassium:
• regulated by aldosterone
• eliminated by kidneys
• additional regulation via shift between ICF and ECF

Calcium:

• most abundant electrolyte in the body
• normal serum level: 8.6-10.2
• normal ionized level: 4.5-5.1mg/dL

Magnesium:

• second most abundant ICF cation after potassium
• normal serum concentration: 1.3-2.3mEq/L

Chloride:

• major extracellular anion
• normal serum level: 97-107mEq/L

Fluid and Electrolyte Regulation:

The mechanisms for regulating the shift of fluids and transporting materials to and from intracellular compartments are:

• Osmosis
• Diffusion
• Active Transport
•  Filtration

Acid-Base Balance:

• an acid is a substance containing a H+ that can be released
• a base is a substance that can accept or trap H+ (bicarb)
• the unit of measurement to describe acid base balance is pH which is an expression of hydrogen concentration
• acidosis is a condition where the pH falls below 7.35
• alkalosis is greater than 7.45
• the narrow range of normal pH is achieved through three homeostatic regulators:
• chemical buffer systems
• respiratory mechanisms
• rena mechanisms

Chemical Buffer Systems:

• carbonic acid-sodium bicarbonate buffer system
• phosphate buffer system
• protein buffer system

Respiratory Regulation od Hydrogen Ions:

• d/t their large surface, that lungs can make rapid changes in hydrogen by diffusing CO2
• when the amount of CO2 in the blood increases, chemorecptors in the medulla are stimulated to increase rate and depth of respiration
• when CO2 decreases, respirations are slowed
• the respiratory system can respond quickly in a healthy person but takes long in its with chronic disease

Renal Regulation of Hydrogen Ions:

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