Acid-Base - Wall Flashcards
What are the two main categories of acids?
carbonic acid and non-carbonic acids
what is the key organ for acid removal? how much does it eliminate per day?
the lungs
15,000 mmol/d
What is the main form of elimination of non-carbonic acids?
the kidneys
how much non-carbonic acids are eliminated each day?
50-100 meq/d
what are the extremes of ph compatible with human life?
6.8-7.8
what is the normal plasma bicarbonate concentration?
24 meq/l
in terms of pH levels, define the following:
acidemia
alkalemia
acidemia - reduced pH
alkalemia - increased pH
What is the chemical equation for the bicarbonate buffer system?
CO2 + H20 <> H2CO3 <> H+ + HCO3-
what is the normal HCO3?
24
what equation did he list as the determinants of pH, showing why only 4 cardinal acid-base disorders?
(pH) x H = 24 x CO2 / HC03
How can you estimate the H concentration from the pH?
[H] = 80 - decimal digits of pH
What is the normal:
pH
pCO2
HCO3
pH - 7.4
pCO2 - 36-44 mm Hg
HCO3 - 22-26 meq/L
In metabolic acidosis, do you have increased or decreased bicarbonate?
decreased bicarbonate
In metabolic alkalosis, increased or decreased bicarbonate?
increased bicarbonate
In respiratory acidosis, do you have increased or decreased C02?
Increased c02
in respiratory alkalosis, do you have increased or decreased c02?
decreased
What is the major extracellular buffer?
hco3
do buffers have an immediate or delayed effect?
immediate
what si the isohydric principle?
all buffers change in the same directoin
Where are the following buffer systems seen in the body:
bicarbonate
phosphate
ammonia
protein
bicarbonate - ecfv
phosphate - urine
ammonia - urine
protein - non-specific
What are secondary, compensatory mechanisms for acid-base disorders?
Lungs - start helping instantly
Kidneys - slower but more powerful than lungs
How do you lungs compensate for metabolic disorders?
altering c02 levels
how do the kidnesy correct respiratory disorders?
alterations in bicarbonate levels (1-2 days)
Explain the four stages of buffer mechanisms in order of soonest to last
Buffer systems (primarily bicarb.) ECF, immediate
Increased rate & depth of breath to decrease co2 - Lungs - minutes to hours
Buffers of phosphate, protein and bicarb - Intracell Fluid - 2-4 horus
Hydrogen Ion excretion, bicarb reabsorption and bicarb generation - kidneys - hours to days
What do the pH, HCO3 and pCO2 do in metabolic acidosis?
pH decreases HCO3 decreases (primary) pCO2 decreases (compensatory)
What do the pH, HCO3 and pCO2 do in metabolic alkalosis?
pH increases HC03 Increases (primary) pCO2 increases (compensatory)
What do the pH, HCO3 and pCO2 do in respi. acidosis?
pH decreases hc03 increases (compensatory) pc02 increases (primary)
What do the pH, HCO3 and pCO2 do in resp alkalosis?
ph INCREASES hco3 decreases (compensatory) pco2 decreases (primary
What are the golden rules of simple acid-base disorders?
- pC02 and HC03 always change in the same direction
- The secondary physiologic compensatory mechanisms must be present
- The ompensatory mechanims never fully correct pH
What is metabolic acidosis?
process that reduces plasma bicarbonate concentration
What is the etiology of metabolic acidosis?
decreased renal acid excretion, direct bicarbonate losses or increased acid generation (ie aspirin or methanol) (i.e. lactic acid and ketoacid)
What are the ways you can get decreased acid excretion?
renal failure/reduced gfr (leadings to decreased ammonium excretion)
type I distal renal tubular acidosis
type 4 renal tubular acidosis (hypoaldosteronism)
What induces respiratory acidosis?
hypercapnia (decreased alveolar ventilation)
what are the actions of the buffering mechanisms in respiratory acidosis?
raise plasma bicarbonate (compensatory) it’s a rapid but limited response
kidneys then minimize change in extracellular pH by increasing acid excretion generating new bicarbonate ions (delayed response)
what are some acute causes of respiratory acidosis?
general anasthesia sedative overdose cardiac arrest pneumothorax pneumonia basically anything that results in decreased oxygen intake that'll cause a build up of lactic acid
what are chronic causes of respiratory acidosis?
obstructive pulmonary disease primary alveolar hypoventilation brain tumor respiratory nerve damage scleroderm prolonged pneumonia
what is the common reason for respiratory alkalosis?
too much breathing
reduced co2 due to increased alveolar ventilation
what does the buffering process do in respiratory alkalosis?
lowers plasma bicarb concentration (rapid but limited response)
kidney response is to reduce net acid excretion (delayed 1-2 days)
what are causes of respiratory alkalosis?
anxiety, hysteria fever cns disease congestive heart failure hypoxia
do acute or chronic respiratory acid base disorders cause a great change in the pH?
acute (kidney hasn’t had the time to compensate)
How does plasma Cl- change in relation to plasma HCO3
Equally but inversely
Does the plasma anion gap change with respiratory disorders?
no
how is plasma sodium affected by respiratory disorders?
it is not directly altered
what occurs in metabolic alkalosis?
raising of the plasma bicarb concent
what is the etiology of metabolic alkalosis?
loss of hydrogen ion from the GI tract (vomiting) or into the urine (diuretic therapy) or through xs acid excretion
what are the major causes of metabolic alkalosis?
GI loss (vomiting) or urinary loss (thiazide type diuretics)
because bicarbonate is raised in metabolic alkalosis, what is necessarily decreased that isn’t part of the overall important chemical equation?
chlorine
when you have been vomiting and excreting pure hcl, what is the urine concentration going to be of chlorine?
it will be extremely low because they will want to keep everything that they can.
What causes an increased plasma anion gap?
when the A- is reabsorbed by the kidneys and reatined in the plasma, as an unmeasured anion
what causes a normal anion gap?
when the A- is filtered and excreted by the kidneys
What makes up the majority of the unmeasured cations?
albumin, normally around 10 meq/L
what can cause an increase anion gap?
renal failure - phosphate, sulfate urate hippurate
where does final excretion of daily acid load occur priamrily?
in the collecting duct
what is the law of electroneutrality?
if sodium concentration stays constant but chloride conc changes, an acid base disorder is present
t or f: sodium concentration is directly altered by an acid-base disorder
fasle, sodium conc is not directly altered by acid base disorder
t or f: chlorine is altered in all acid base disorders (except decreased plasma anion gap metabolic acidosis)
false: chlorine concentration is altered in all acid-base disordes except with DECREASED plasma anion gap metabolic acidosis
