Exam 1 – Lecture 1: Dr. Langston Flashcards
What is homeostasis?
The maintenance of a stable internal environment of the body in higher animals under fluctuating environmental conditions
What is physiology?
The science of how the body maintains homeostasis
What is pathophysiology?
The science of how the body responds to disease in an effort to maintain homeostasis. The basis for the scientific approach to medicine
What are all chemical reactions in the body like?
They are in an aqueous matrix and many use water in the reaction
What does circulation of fluids provide the cells?
Access to nutrients and removes waste
Why do some of the most common and important problems in clinical medicine arise?
Because of abnormalities in the control systems that maintain constancy of body fluids
What are the goals of homeostasis with fluids in the body?
Maintain hydration
Maintain an isotonic environment for most tissues
Maintain the microcirculation for effective exchange of fluids through tissues
Maintain a constant blood and extracellular fluid pH
How much water makes up the body?
40-70% (average 60%)
What must the amount of fluid you take in equal?
The amount of fluid you let out
How can water be taken in? (sources of water)
Metabolism of carbohydrates Oral intake (majority)
How many fluids should a cat get per day?
40 ml/kg
How many fluids should a dog get per day?
60 ml/kg
How can you figure the amount of maintenance fluids that should be given?
1.5 x 70 x (body weight in kg)^0.75
What does fluid diuresis supply?
IV fluids in excess of maintenance requirements to “volume load” patient and promote urine production
How can body water be lost?
Sweat (horses, man, slight cow)
Saliva for cooling (cats, rats, kangaroos)
Feces
Insensible water loss (skin, respiratory tracts)
Urine
What is the main cause of body water loss? How much?
Urine at 1 to 2 mls/kg per hours if not dehydrated
How do dogs blow off heat? Why?
Panting
They cannot sweat
What is a major cooling mechanism for horses?
Sweating
If an animal is 5% dehydrated, what are its symptoms?
Just barely detectable
Lethargic
“Tacky” mucus membranes
“Skin tent” perhaps slow
If an animal is 8% dehydrated, what are its symptoms?
Depressed
“Skin tent” 1 to 3 seconds
Eyes withdrawn into sockets
Capillary refill 2-3 seconds
If an animal is 10% dehydrated, what are its symptoms?
Unresponsive and in shock "Skin tent" 3 to 5 seconds Capillary refill is more than 3 seconds Eyes sunken into sockets Progressing toward death
What do you assume 1 kg is equal to?
1 liter
What do you pinch to check “skin tent” in dogs? Cows and horses?
Throax
Eyelids
What is the deficit?
Dehydration losses
How do you figure the deficit?
Take the kg multiplied by the percentage of dehydration
How do you calculate the amount of fluids needed?
Deficit + maintenance + ongoing losses
How much of body weight is blood?
8%
How much of the blood is plasma? Cells?
60%
40%
How much of the total body water distribution is plasma?
5%
How much of the total body water distribution is interstitial fluid?
15%
How much of the total body water distribution is intracellular fluid?
40%
How much of the total body water distribution is extracellular fluid?
20-30%
What makes up extracellular fluid?
Plasma and interstitial fluid
How much of the total body water distribution is transcellular fluid?
Variable %
What fluids make up transcellular fluid?
Cerebrospinal fluid Digestive tract Intraocular fluid Peritoneal fluid Pleural fluid Synovial fluid
Where does interstitial fluid circulate?
Around the cells
What does the capillary membrane act as?
Endothelium barrier
What do all body fluids contain?
Other substances that exert osmotic pressure
What are the chief substances that exert osmotic pressure?
Ions and proteins (sodium and potassium)
What is a solution?
A homogeneous mixture of two or more substances, usually in a liquid
What is solvent?
The substance whose physical state is preserved in a solution
What is solute?
The substance whose physical state is changed in a solution
What is a crystalloid?
A solution that diffuses readily through semipermeable membranes, and generally is capable of being crystallized. Includes solutions with the major electrolytes or dextrose as solutes
What is colloid?
A mixture with properties between those of a solution and fine suspension. Includes blood products and hetastarch
What forms the major colloid in the body?
Proteins
What is a mole?
The molecular weight of a substance expressed in grams
What is a molar?
Number of mole per liter of fluid
What is osmotic pressure?
The pressure needed to prevent the diffusion of water across a semipermeable membrane to the solution that has the greater number of particles
What is plasma oncotic pressure?
The pressure exerted by plasma proteins on the capillary wall
A component of osmotic pressure
What is an osmole?
A unit of osmotic pressure equivalent to the amount of solute that dissociates in solution to form one mole of particles
What is osmolarity?
The concentration of dissolved particles per unit of volume
osmole/L or milliosmole/mL
What is osmolality?
The concentration of dissolved particles per unit of weight
What is the osmolarity of plasma?
280-310 mOsm/L
What is tonicity?
Discussed in terms of osmolarity across a membrane
Refers to the effects of a fluid on a cell it surrounds
What is the osmolarity of isotonic fluids like compared to the inside of a cell? Hypotonic fluids? Hypertonic fluids?
The same
Less than
Greater than
When we give fluids, what kind is it 90% of the time?
Isotonic
When something is isotonic, what happens?
No change
When something is hypotonic, what happens?
Cell swells
When something is hypertonic, what happens?
Cell shrinks
What does a hypertonic saline help with in emergencies?
Increasing blood pressure
What is very important in water regulation?
Kidney and adrenal glands
What do osmoreceptors in the brain respond to?
Changes in extracellular tonicity to alter thirst and water intake
What are idiogenic osmoles?
Osmotically active substances generated in neurons
What can the neuron do to idiogenic osmoles?
Increase or decrease the number of idiogenic osmoles to balance its osmolarity against that of plasma and the extracellular fluids
What does Starling’s hypothesis state?
The fluid movement due to filtration across the wall of a capillary is dependent on the balance between the hydrostatic pressure gradient and the oncotic pressure gradient across the capillary
What are the 4 Starling’s forces?
Hydrostatic pressure in the capillary (Pc)
Hydrostatic pressure in the interstitium (Pi)
Oncotic pressure in the capillary (pc)
Oncotic pressure in the interstitium (pi)
What is edema?
Tissue swelling from fluid accumulation
What does edema cause?
Cellular damage and swelling
What causes edema?
Disruption of Starling’s forces
What can cause a disruption of Starling’s forces?
Increased capillary hydrostatic pressure
Decreased capillary oncotic pressure
Increase capillary permeability
Blockage of lymphatics
What does increased capillary hyrdrostatic pressure cause?
A pressure build up on the venous side of the heart
What are some safety factors that help prevent edema?
Interstitial tissue has a negative pressure
Lymphatic system increases outflow
Washdown of interstitial fluid protein
What are transcellular spaces?
Potential spaces where the accumulation of fluids can occur
What is the fluid accumulation in transcellular spaces called?
Effusion (sometimes called 3rd spacing)
What is 1st space shifting?
Normal distribution of fluid in both the ECF and ICF compartments
What is 2nd space shifting?
Excess accumulation of interstitial fluid
What is 3rd space shifting?
Fluid accumulation in potential spaces
What did the revised Starling’s hypothesis include?
Role of endothelial glycocalyx
Which is more acidic, venous blood or arterial blood?
Venous
Which is more available, venous blood or arterial blood?
Venous
What is the only place in the body that has extensive pH?
Urine
What can happen with the different pH levels of urine?
Different diseases are affected by a certain pH
What can be changed to manipulate urine pH?
Diet
What happens if urine has a pH of 7.2? 7.0?
Animal is very sick
Death
What is an acid?
An ion molecule that can release hydrogen ions into solution (donates hydrogen ion)
What is a strong acid?
Rapidly dissociates and releases large amounts of H+ into solution
What is a weak acid?
Slowly dissociates and releases small amounts of H+ into solution
What is the only strong acid in the body?
HCl
What is a base?
An ion or molecule that can accept an H+ into solution
What does a strong base do?
Reacts rapidly and strongly with H+ and quickly removes them from solution
What does a weak base do?
Binds with H+ more weakly than it does OH-
What is the most common weak base?
Bicarbonate (HCO3-)
What do proteins in the body function as? Why?
A base
Because some of the amino acids that make up proteins have net negative charges that readily accept H+
What are some of the most important bases in the body?
Hemoglobin in RBCs and proteins in other cells
What are some acid-base balancing systems?
Respiratory (expiration of CO2)
Renal (excretion and retention of H+ and HCO3-)
Buffering systems
What is a buffer?
A substance that stabilizes the hydrogen-ion concentration of a solution by neutralizing, within limits, both acids and bases
What are the intracellular primary buffering systems?
Intracellular proteins
Phosphate buffer system
What are the extracellular primary buffering systems?
Hemoglobin
Bicarbonate buffering system
What is the bicarbonate buffering system important in?
Maintaining the pH of the extracellular fluid
Buffers are one of the main ways that __________.
The body maintains pH
Know the equation for the bicarbonate buffer system
CO2 + H20 –> H2CO3 —> H+ + HCO3-
What are the 4 primary acid-base disturbances?
Metabolic acidosis
Metabolic alkalosis
Respiratory acidosis
Respiratory alkalosis
What is the most common acid-base disturbance?
Metabolic acidosis
How much aspirin can be given to a cat?
10 mg/kg every 2-3 days
How much aspirin can be given to a dog?
10 mg/kg every 12 hours
Why does diarrhea cause?
Loss of the hydrogen ion
What does excess CO2 do to the respiration rate?
Increases it
What impacts respiration?
CO2
Why does metabolic acidosis happen?
Because there is not enough bicarbonate or addition of acid
What can cause metabolic alkalosis?
Loss of acid (vomiting)
What does metabolic alkalosis tell the body to do?
Retain CO2
How can you combat metabolic alkalosis?
Dilute acid IV or isotinic saline and NaCl
What can cause respiratory acidosis and alkalosis?
No ventilating or breathing properly
What can panting cause?
Respiratory alkalosis
Can the bicarbonate system correct respiratory acidosis or alkalosis?
No
How can respiratory acidosis or alkalosis be corrected?
If it’s an anesthetic problem, it can be corrected primarily through cellular buffers.
If it’s from a disease, it is up to the kidney
What is the primary reason for metabolic acidosis? How can it be compensated?
Low HCO3
Decrease the pCO2 by hyperventilation
What is the primary reason for metabolic alkalosis? How can it be compensated?
High HCO3
Increase the pCO2 by hypoventilation
What is the primary reason for respiratory acidosis? How can it be compensated?
High pCO2
Kidneys retain HCO3
What is the primary reason for respiratory alkalosis? How can it be compensated?
Low pCO2
Kidneys excrete HCO3
Know equations for metabolic and respiratory acidosis and alkalosis
Know equations for metabolic and respiratory acidosis and alkalosis
What does hydrostatic pressure in the capillary do?
Tends to force fluid outward through capillary membrane
Fluid moves from capillary into interstitium
What does hydrostatic pressure in the interstitium do?
Tends to force fluid inward through capillary membrane
Fluid moves from the interstitium into capillary
What does oncotic pressure in the capillary do?
Tends to cause osmosis of fluid inward through capillary membrane
Fluid moves via osmosis from the interstitium into capillary
What does oncotic pressure in the interstitium do?
Tends to cause osmosis of fluid outward through capillary membrane
Fluid moves via osmosis from the capillary into interstitium
