Chapter 26 - Fluid Loss Flashcards
What % of body weight is water?
45-75%
What % of body weight is water for the following groups: infants, men, women?
Infants 73%
Men 60%
Females 50%
Why do women have higher body weight water % than men>
Higher Fat Content
Less Skeletal Muscle Mass
What is the total water capacity of both fluid compartmnets?
40L
What is ICF? How much water does it account for?
Intracellular Fluid Compartment
Accounts for 2/3 or 25L of the body’s water
What is ECF?
Extracellular Fluid Compartment
About 1/3 or 15L
What are the 3 parts of ECF?
Plasma, 3L
Interstitial Fluid, 12L
Other
What are the “other” ECFs?
Lymph CSF Humors of Eye Synovial Fluid Serous Fluid Gastrointestinal Fluid
How many fluid compartments do we have?
2
What type of solvent is water?
Universal
What are the 2 solutes?
Electrolytes and Non-Electrolytes
What are electrolytes? Give examples
Have electric charge when dissolved in water
Dissociate in water
Inorganic Salts
Acids and Bases
Some Proteins
What are non-electrolytes? Give examples
Do not carry charge
glucose
lipids
creatine
urea
What are the major cation and anion for ECFs?
Anions - Cl-, HCO3-
Cations: Na+
What are the major cation and anion for ICFs?
Cations: K+
Anion: HPO4^2-
What is fluid movement driven by?
Osmotic and hydrostatic pressures
What is osmotic pressure?
Water’s willingness to move
What is hydrostatic pressure?
The “pushing” pressure
How does water move in osmosis?
Water moves to areas of low solute concentration
Is the 2-way flow of water possible within the body?
Yes, if solute concentration changes, water will move to even it out
What is the most significant source of water loss?
urine, accounts for 60% of loss
What are sources of water intake?
Beverage
Food
Metabolic Water
What are sources of water output?
Urine
Insensible water loss in skin and lungs
Perspiration
Feces
How does water input compare to output?
Equal, roughly 2500mL or 2L daily
Who regulates the intake of water?
Hypothalamic osmoreceptors, driven by thirst
What stimulates water intake?
Increase in plasma osmolarity by 2-3%
Increase in angiotensin II
Dry Mouth
Decrease in blood volume
How do we regulate water output?
Insensible water loss from lungs and skin due to evaporation
Feces
What is our minimum sensible loss in urine?
500mL to secrete waste
What effect does ADH have on water retention?
Causes aquaporins to be inserted into cell membrane of collecting ducts.
ADH saves water
How does water absorption in the collecting duct compare to ADH release?
They are proportional
What happens if you release LESS ADH?
Dilute urine and decreased body fluids
What happens if you release MORE ADH?
Concentrated Urine and increased body fluids
When is ADH release?
When ECF osmolarity is HIGH (concentrated blood)
What are other influencing factors that stimulate ADH release?
Fever Sweating Vomiting Diarrhea Blood Loss Traumatic Burns
What is dehydration?
Negative fluid balance
ECF water loss
What are some causes of dehydration?
Diuretic Abuse Diarrhea Sweating Water Deprivation Hemorrhage Severe Burn Prolonged Vomiting
What are symptoms of dehydration? What can dehydration lead to?
Thirsty, dry flushed skin
May lead to weight loss, fever, confusion, shock and loss of electrolytes
What is hypotonic hydration?
Too much water!
Over-hydrated cells
Also called water intoxification
What are causes of hypotonic hydration?
Renal insufficiency or drinking too much water too fast
What are symptoms of hypotonic hydration?
Nausea, vomiting, muscle cramps, headaches, cerebral edema, convulsions, coma, death
How do you treat hypotonic hydration?
hypertonic saline
What organ is primarily responsible for balancing electrolytes?
Kidneys
Why are salts (electrolytes) important?
control fluid movement
Neuromuscular excitability
secretory activity
membrane permeability
What are 3 important things to know about sodium?
- Most abundant cation in the ECF
- Sodium exerts MOST of the osmotic pressure and does the most to control water volume and water distribution in the body
- total sodium content may change, but ECF Na+ remains stable due to osmosis
3 Mechanisms of Dehydration
1) Excessive loss of H20 from ECF
2) ECF osmotic pressure rises
3) Cells lose H20 to ECF by osmosis, cells shrink
3 Mechanisms of Hypertonic
1) Excessive H20 enters ECF
2) ECF osmotic pressure falls
3) H20 moves into cells by osmosis, cells swell
Overhydration is also called…
Hypotonic hydration
Water intoxication
What hormone promotes sodium reabsorption?
Aldosterone
What % of reabsorption occurs in the proximal convoluted tubule?
65%
What % of reabsorption occurs in the Loops of Henle?
25%
What does it mean to have “high aldosterone” levels?
Sodium is reabsorbed from filtrate in the DCT and collecting ducts
What is the biggest trigger for aldosterone release?
Angiotensin II
What triggers the release of angiotensin II?
When the granular cells of the JGA secrete renin
When do granular cells secrete renin?
In response to low blood pressure and low filtrate osmolality
How fast does aldosterone work?
Very SLOWLY; takes hours to days
When is atrial natriuretic peptide (ANP) released?
Released by atrial cells in response to stretch of the tissue.
What causes atrial stretch?
High blood pressure
What are the effects of ANP?
Reduces production of ADH, Renin, Aldosterone and Angiotensin II
Increases excretion of Na+ and water
Promotes vasodilation directly
What other hormones affect sodium balance?
Estrogen
Progesterone
Glucocorticoids
What effect does estrogen have on sodium balance?
Increase NaCl reabsorption (Increases H20)
What effect does progesterone have on sodium balance?
Decrease sodium reabsorption
Promotes loss of sodium and water
What effect does glucocorticoids have on sodium balance?
Increase sodium reabsorption and edema
What is Ca 2+ important for?
Neuromuscular excitability
Blood Clotting
Cell Membrane Permeability
Secretory Activities
What happens during HYPOcalcemia?
Low Calcium levels
Increase excitability and muscle tetany
What happens during HYPER calcemia?
High Calcium Levels
Inhibits neurons and muscle cells, can cause heart arrhythmias
What is calcium balance controlled by?
PTH
Calcitonin
What is the only hormone to respond to high BP/atrial stretch?
ANP
How do acids enter the bloodstream?
Most enter as breakdown of foods, but some enter as foods
What is the normal pH of body fluid?
7.35 to 7.45
What is alkalosis?
> 7.45
Body contains excess bases, is alkaline
What is acidosis?
<7.35
Body is acidic
What does pH affect?
ALL functional proteins and biochemical reactions in the body
What are 3 types of H+ ion concentration?
- Chemical Buffer System
- Brain Stem Respiratory Centers
- Renal Mechanisms
What is the chemical buffer system?
System of 1 or more compounds that act to resist pH changes when strong acid or base is added.
Most important, first line of defense
What are the 3 Chemical Buffer Systems?
Bicarbonate (HCO3)
Phosphate Buffer System
Protein Buffer System
What is the Bicarbonate HCO3 buffer system?
Buffering the ICF and the ECF
Acts rapidly by releasing or binding H+
How quickly do the respiratory and renal systems respond?
Slowly but have more capacity
What is the job of the respiratory buffer system?
Elimination of CO2 when in acidosis by increasing respiration and depth
Eliminate CO2, increase pH
How does alkalosis effect the respiratory buffer system?
Depresses the respiratory center, helping to retain CO2 and lower of blood pH
What do renal mechanisms depend on?
Depend on secretion of H+ in the PCT and controlling duct
What is metabolic acidosis and alkalosis?
Any pH imbalance NOT caused by abnormal HCO3- levels
What is metabolic acidosis? What causes it?
pH is too acidic
- Too much alcohol (metabolized into acetic acid)
- Excessive loss of HCO3 (Bicarbonate) as in persistent diarrhea
- Build up lactic acid, shock, ketosis, starvation, kidney failure
What is metabolic alkalosis? What causes it?
- MUCH less common
- Rising blood pH and HCO3- levels
- Cause is excessive vomitting and loss of the acid contents or excessive amounts of antacids
What happens when your pH is below 7?
CNS depression
Coma
Death
What happens when pH is above 7.8?
Excitation of nervous system, muscle tetany, nervousness, convulsions, respiratory arrest death
