acid / base - patho 406 Flashcards
pH
the potential or power of hydrogen
the negative logarithm of the hydrogen ion -> when H+ goes up, pH goes down
acid substances can “” an H+ ion & alkaline substances can “” an H+ ion and “” an OH-
give ; accept ; give up
why is hydrogen important to the body
-helps maintain cell membranes
-helps w/ enzyme activity
-component of H2O
-helps energy production
hydrogen is a component of
sugars
proteins
starch
fats
what does a neutral acid-base balance mean
-pH=7
-equal H+ & OH-
pH goal range
7.35 - 7.45
pH is not the same through the body
what happens if the body’s pH is not within goal range
-enzymes malfunction
-electrolyte imbalances (esp K+)
-O2 transport & delivery can be affected
if the body is more acidic, hemoglobin will
give up oxygen more readily at the tissue
if the body is more alkalotic, hemoglobin will
hold on to the oxygen and not give it to the tissue
a bigger problem then if the pt is more acidic
what pH is incompatible to life
below 6.8 d/t profound effect on cellular metabolism, enzyme activity and oxygen delivery to the tissue
if the pH is above 7.8
life threatening -> disrupts essential bodily functions, particularly in the cardiovascular and nervous system
what are the two types of acids in the body
volatile & non volatile
volatile acids
-can be converted to gas
-excreted/eliminated by the lungs
-one volatile acid in body (carbonic acid H2CO3 -> H2O + CO2)
allows lungs to expel carbon dioxide
non volatile acids
-lactic acid (met by kid/liv, can be reconverted & used as energy production if needed)
-phosphoric acid (bones & kidney support)
-sulfuric acid (produced w/ protein met)
-acetoacetic acid (produced in liver)
-beta hydroxybutric (inc w/ exercise, calorie restrictions, fasting & dx of ketoacidosis)
will all be eliminated by kidney (expect lactic acid) & cannot be converted to a gas
lactic acid is a byproduct of what
anaerobic metabolism
at baseline, does the body produce more acids or bases
acids b/c we eat/drink more acidic foods, the metabolism of lipids & protein generate acids and cellular metabolism waste product is CO2 which makes volatile acid
how does the body maintain acid - base homeostasis
-buffers: works all the time & is immediate
-respiratory system: rapid but short lived
-renal system: long term balance
buffers
-chemicals in the body that combine w/ acid or bases to change the pH
-accept or release a H+
-almost instantaneous but short lived
3 main systems: bicarbonate - carbonic acid buffer, phosphate buffer & protein buffers (hemoglobin)
Bicarbonate - Carbonic Acid
-main buffer seen outside the cell in the ECF
-carbonic anhydrase breaks down carbonic acid, if in the lungs this allows for CO2 to be expelled & if it is in the kidneys then will break down into H+ + HCO3- and the kidneys can excrete the hydrogen ions
if a patient is in the ICU and is acidic & not compensating, what can we give
sodium bicarb to raise their pH
Bicarbonate - Carbonic Acid equation (need to know)
HCO3- (bicarb) + H+ <-> H2CO3 (carbonic acid)<-> CO2 + H2O
if we retain CO2, equation will work in the direction of increases bicarb (think COPD or resp depression
kidneys can generate bicard & rid H+, lungs can expel CO2
phosphate buffer
main intracellular buffer
H+ +HPO4-2 = H2PO4- (example of buffer picking up a H+ ion intracellularly to balance pH)
Protein Buffers
-nearly all proteins can function as buffers
-carboxyl group (COOH) is a weak acid that gives up H+ (ex: amino acids & acetic acid)
-amino group (NH2-) accept H+
-hemoglobin picks up CO2 at the cellular level which results in less CO2 to make carbonic acid
cellular compensation
pH decreases -> H+ move into the cell creating more positively charged ions in the cell -> K+ moves out of the cell to maintain a neutral charge since it is also a + ion -> electrical neutrality is restored inside the cell
process will reverse as pH neutralizes & H+ will move out of the cell and K+ will move back into the cell
main concern w/ cellular compensation
K+ will be moved out of the cell and if it cannot be excreted through the kidneys, dysrhythmias can occur or if too much get excreted which can also cause a dysrhythmias
respiratory mechanisms to maintain pH homeostasis
when carbonic acid reaches the lungs it will break back into water and CO2 which will be expelled so body can adjust pH by changes rate & depth of breathing (inc will blow off more CO2 if pt is acidic, dec if patient is alk)
does not work for non volatile acids
kidney regulation maintain pH homeostasis
long term adjusters, adjusts the amount of HCO3
-can eliminate large amounts of acid expect carbonic acid & can also excrete base (when pH is too basic)
-can conserve & produce new bicarb ions (when pH is too acidic)
-most effective regulator of pH
-if kidney fails, pH balance fails
if a patient is in renal failure, what do they usually have to take daily
sodium bicarb to regulate their pH
kidney regulation: acidosis
kidneys respond by increasing reabsorption of bicarb (& making new) and increasing secretions of hydrogen ions (acid component) into the urine. this helps raise pH back to normal
kidney regulation: alkalosis
kidney respond by decreasing bicarb reabsorption and reduce hydrogen ion into urine. This helps lower the pH back to normal
rates of correction
Buffers: instantaneously
Respiratory: several minutes to hours
Renal: several hours to days
compensation
if underlying problem is metabolic, hyperventilation or hypoventilation can help aka respiratory compensation
If underlying problem is respiratory, renal mechanisms can bring about metabolic compensation
normal CO2
35-45
normal pO2
80-100
normal HCO3
24-29
normal O2 stat
95-100%
