1. Water, Electrolytes and Acid-Base Balance
Chapter 25
Corrie Ruckdeschel RN, BSN

2. Body Composition of water
Males = 60%
Females = 50%
Infants = 75%
Adipose tissue (fat tissue) contains less water than muscle...
Obese person has less water than a thin person

3. Fluid Compartments
Intracellular - 63%
Extracellular - 37%

4. Extracellular Fluid Interstitial - between cells, tissue fluid
Plasma - liquid intercellular matrix, blood component
Lymph - fluid w/in lymphatic vessels
Transcellular
CSF- Cerbral Spinal Fluid
Aqueous/Vitreous Humor - Fluid in the eye
Synovial fluid - Fluid found in joints
Serous fluids - secreted from serous membranes , Pericardium, Pleural membranes,
Glandular secretions

5. Composition of body fluids
Intracellular and Extracellular vary in their concentration of various electrolytes.
Electrolytes can move from one compartment to another ...well regulated!
Extracellular
Na+ sodium
Cl- Chloride
Hco3- bicarbonate
Plasma contains more protein than others
Intracellular
K+ potassium
po4- phosphatase
Mg++ Magnesium

7. Water Balance Intake = Output
Average adult takes into their body ml /24 hours...
drinking 60%
water from food 30%
water from metabolism 10%
Thirst regulates Intake - thirst center is in the hypothalamus (brain)
Decreased thirst mechanism in the elderly...prone to dehydration

8. Water Balance Output Output Water is eliminated by:
Kidneys (urine) 60%
Skin (sweat)
Lungs
Digestive tract (feces)

9. Output and Kidneys Kidneys are the primary regulator of output
React to a hormone, ADH (anti-diuretic hormone), when there is...
Less H20 body content ---- post. pituitary gland releases hormone (ADH) ---- stimulates collecting duct in kidney to reabsorb H20----
Decrease in urine output
Increase in amt of fluid circulating (blood volume)
Excess H20 body content ----decrease in amt of ADH secreted by the posterior pituitary gland ----decrease in H20 reabsorption
Increase in water elimination, increase in urine output.

10. Intake = Output
Water input should equal output!!

11. Water Imbalance Dehydration = deficiency in body water
OUTPUT > Intake
sweating, vomiting, diarrhea, uses of diuretic medication, poor po intake
Assess: Skin turgor (poor, good)
HOW? pinch the skin on the dorsal aspect of the hand, evaluate how quickly the skin returns to a flat position. If it is slow to return, stays in a tenting position = depletion of fluid in the interstitial spaces
untreated...low blood volume, low blood pressure...hypovolemic shock...death!

12. Water Imbalance
Edema - retaining fluid, especially in the interstitial space
Pedal edema - water accumulation in ankles/feet
Pulmonary edema - water accumulation in the lungs causing hypoxemia (low o2 in blood), cyanosis (blue discoloration to skin), shortness of breath
Cerebral edema - water accumulation in the brain. Life- threatening as the increase in pressure in the cranial cavity (intracranial pressure) - pressure on the brain tissue...neurological dysfunction...death if untreated!
Assess: edema (pitting, non-pitting)
Goals - to remove excess fluid, relieve symptoms and treat underlying cause.

13. Assessing Edema
Edema is observable swelling from fluid accumulation in body tissues.
Edema most commonly occurs in the feet and legs, where it is referred to as peripheral edema. The swelling is the result of the accumulation of excess fluid under the skin in the spaces within the tissues.
Assess area... push your finger down on the affected area...release. If an indentation retains, it is considered pitting edema.
Daily Weights - reliable measurement of H20 balance

14. Why does fluid shift?
Fluids shift because of changes in the “pushing/pulling” force in capillaries:
capillary filtration force
plasma oncotic pressure
effect of lymphatic drainage
effect of plasma proteins trapped
Fluid Spacing - clinical term refers to the distribution of body water
First spacing - normal distribution
Second spacing - accumulation of H20 in interstitial spaces - can be easily corrected with treatment
Third spacing - accumulation of fluid in spaces not easily reabsorbed - Abdominal cavity (ascites), cranium (cerebral edema)

15. Electrolyte Balance
Electrolyte Balance exists when the amounts of the various electrolytes gained by the body equal the amounts lost by the body.
Electrolyte imbalances are common, serious clinical challenges.
See Table 25-1 pg. 447

16. Sodium (Na+)
Sodium id the chief extracellular cation, accounts for 90% of the positively charged ions.
Necessary for nerve impulse conduction
Sodium is regulated by the hormone, aldosterone which acts on the kidneys to reabsorb sodium - back into the blood stream.
“when sodium moves, water moves”
Aldosterone retains/reabsorbs both sodium and water

17. Sodium imbalances
Hyponatremia - decrease in concentration of plasma Na+
Causes: excess water in blood (blood is diluted)
Hypernatremia - excess Na+ in the blood

19. Potassium Imbalances