Flash Notes Miscellaneous - Acid Base Basics Flashcards
what is an acid? acidosis? acidemia?
acid: substance that gives up/donates a proton, acidosis: process that causes an excess of acid, & acidemia: pH of extracellular fluid is lower than normal, <7.4
what is a base? alkalosis? alkalemia?
base: substance that accepts/binds a proton, alkalosis: process that causes an excess of base, & alkalemia: pH of extracellular fluid is higher than normal
what is a buffer? why are they important? what role do they usually play?
compound that can accept or donate a proton - important to minimize pH changes in solutions/tissues, usually a weak acid with their corresponding salts
what happens when a strong acid is added to a buffer solution?
protons are donated to/accepted by the weak acid forming a salt & limiting the change in pH
what do acids do to litmus paper? what do bases do to a litmus paper?
acids turn it pink/red & base stays or turns blue
what are the 2 categories of buffers? which one is used most often in acid/base evaluation?
bicarbonate (HCO3-) major extracellular buffer & everything else (non bicarb) - bicarb
T/F: all buffers shift in the same direction as pH because pH & [H+] are inversely related
TRUE
how are hydrogen ions measured?
by pH
how are pH & H+ related?
inversely related, so if one increases the other decreases
what is pH?
approximate measure of the concentration of the hydrogen ion, pH = the negative log (base 10) of [H+]
a higher H+ means what to pH?
lower pH
what are the 3 mechanisms used to maintain pH homeostasis at 7.4?
- physiochemical buffering (develops immediately), 2. respiratory compensation (elimination or retention of CO2), & 3. metabolic compensation
what is the physiochemical buffering mechanism?
balance of cations/anions always maintained that occurs both intra & extra cellularly that occurs immediately & involves HCO3, proteins (hemoglobin & albumin), & phosphates
what is the respiratory compensation mechanism?
elimination or retention of CO2 seen within minutes & complete in minutes to hours where CO2 functions as an acid (carbonic acid formed when combined with water & called a volatile acid because removed via the lungs)
what is the metabolic compensation mechanism?
elimination or retention of H+/HCO3 by the kidney that begins within hours & is complete in 2-5 days
what is an anion gap?
calculation/estimate of the difference between cations/anions in serum/plasma used to evaluate a/b balance & to categorize/identify a metabolic acidosis
what are the measured cations & anions used to calculate an anion ap?
cations: sodium & potassium, anions: HCO3 & chloride
when there are changes in what ions, the anion gap will increase or decrease?
changes in the unmeasured ions!!!!
how is the anion gap calculated?
(Na + K) - (Cl + HCO3) = anion gap (anions - cations)
what are some common causes of a high anion gap?
alkalemia, dehydration, hyperalbuminemia
what are some common causes of a decreased anion gap?
acidemia, hemodilution, hyperglobulinemia, & hypercalcemia
what is the traditional approach to acid/base status?
using the henderson-hasselbalch equation: pH = 6.1 + log [HCO3]/(0.03 X pCO2)
what is the non-traditional approach to acid/base status?
strong ion theory
what 3 physical laws is the non-traditional approach to acid/base based on?
electroneutrality always maintained, equilibrium equations of incompletely dissociated solutes are satisfied, & conservation of mass
what are the 3 independent variables in the non-traditional approach to acid/base?
pCO2, atot (total concentrations of weak acids, balance between strong cations/anions), & strong ion difference
what is the strong ion difference? what are the cations? which is the most important cation? what are the anions?
balance between strong cations/anions, cations: Na, K, Mg, Ca, most important is Na (high concentration affects SID), anions: Cl & unmeasured anions (lactate, ketones, sulfates)
in the non-traditional approach to acid-base status, an increase in strong ion difference indicates? what about a decrease?
increase = alkalosis & decrease = acidosis
what is the one dependent variable used in the non-traditional approach to acid/base?
bicarbonate - altered by internal changes only
what is the basic concept of the strong ion therapy?
a/b status is determined by the concentration of CO2, proteins, & anion/cation balance
what is partial pressure? what do we measure?
pressure exerted by one compound contained in a mixture, pCO2 (partial pressure of carbon dioxide), pO2 (partial pressure of oxygen), & CO2/O2 are the main blood gases
what is the respiratory component in acid/base balance in both approaches to acid/base?
carbon dioxide - end product of metabolism
what is the metabolic compenent of acid/base balance which is also the major chemical buffer in the body?
bicarbonate - regulated by the kidneys & indirectly by the lungs
HCO3 is regulated by what?
directly the kidneys & indirectly the lungs
what is base excess?
net amount of base present
what is the base deficit?
net amount of acid present
what is negative base excess?
amount of additional acid or base needed to bring pH back to 7.4
what is the important equestion to know for bicarbonate?
HCO3 + H = H2CO3 = H2O + increased CO2
dogs & cats tend towards what while herbivores tend toward what? why?
dogs/cats: acidemia as HCO3 increases to balance gastric acid secretion & herbivores: alkalemia that is diet related
