Pathophysiology Exam #1 Flashcards
How much acid does adults produce in a day? How much acid does a child produce in a day? How does being in a catabolic state affect acid production?
• Adults: produce 1 mEq/kg/day of acids
• Children: 2 – 3 mEq/kg/day
o Children produce more acid than adults, so at greater risk for A-B imbalances & which is why their RR is faster (to blow off more CO2)
• Catabolism: significantly increased
o Pt in a catabolic state (breaking down proteins & amino acids for energy) increases their acid load à so
need to feed them bc until correct catabolism it’ll be hard to correct their A-B imbalance.
What are two types of acid that is produced by the body?
- volatile
- non volatile
What are the characteristics of volatile acid produced by the body?
• VOLATILE: LARGEST % OF ACIDS
o Volatile acids can chx from one state to another very quickly
o VOLATILE ACIDS COME FROM CO2, A BYPRODUCT OF FAT & CHO (CARB) METABOLISM
o CO2 + H2O -> H2CO3 (carbonic acid)
o CO2, a gas, REGULATED BY LUNGS, hence the name volatile acids
What are the characteristics of non-volatile acid produced by the body?
• NON-VOLATILE: SMALLER % OF ACIDS
o From protein metabolism
O SO NON-VOLATILE ACIDS ARE NON-CARBONIC; CONTAIN NO CO2; NOT REGULATED BY LUNGS
o REGULATED BY KIDNEYS
o E.G., sulfuric acid; phosphoric acid; many others
What are acids? What is the difference between a strong acid and a weak acid?
ACIDS
• Molecule or ion that DONATES H+ ions (protons) in chemical reactions
• Strong acids: freely dissociate into H+ & anions; e.g., HCl
o Strong acids freely give up their H+ ions
HCl -> H+ + Cl-
Hydrochloric acid when broken down disassociates into H+ & the associated anion Cl-
• Weak acids: minimally dissociate into H+ & anion; e.g., H2CO3 (carbonic acid)
o Weak acids don’t want to give up their H+ ions
H2CO3 ->H+ + HCO3-
Carbonic acid when broken down disassociated into H+ & its associated anion bicarb
What are bases? What is the difference between a strong base and a weak base?
BASES
• Molecule or ion that ACCEPTS H+ (protons) in chemical reactions; removes the H+ from the solution
• Examples:
o HCO3- + H+ -> H2CO3
(Bicarb binds to H+ & removes H+ from the solution & become carbonic acid)
o HPO4– + H+ -> H2PO4-
(Base phosphate will accept H+ & become acid phosphate)
- Strong bases (OH- aka hydroxide) react strongly with H+ -> strong bases readily accept H+ ions
- Weak bases (HCO3-) react weakly with H+
What are examples of a strong acid and a weak acid?
Strong Acid: HCl
o Strong acids freely give up their H+ ions
HCl -> H+ + Cl- (Hydrochloric acid when broken down disassociates into H+ & the associated anion Cl-)
Weak Acid; H2CO3(carbonic acid)
o Weak acids don’t want to give up their H+ ions
H2CO3 ->H+ + HCO3-(Carbonic acid when broken down disassociated into H+ & its associated anion bicarb)
What is the role of proteins in acid base balance?
ROLE OF PROTEINS
• Some amino acids cant accept H+ & donate H+ in certain conditions
• Zwitter ion -> a substance that can accept H+ & liberate H+
• E.G., albumin in the plasma & hgb in RBCs
o Albumin & hgb are proteins that can accept or donate/liberate H+ ions depending on the condition
• Hypoalbuminemic or anemic = met acidosis
o Hypoalbuminemic or anemic -> problem is there isn’t enough protein (albumin) to remove/accept H+
ions from the body’s environment. This leads to met acidosis.
Define pH value?
• H+ ion concentration is expressed
as pH value
• pH: Puissance hydrogen (power of hydrogen or H+ concentration)
• pH: negative logarithm of H+ ion concentration
In regards to the pH scale, describe what is happening as we move towards the left(towards 10^0) and what is happening as we move towards the right(10^-14)
o As we move to the left on the scale (towards 10^0)
increasing H+ ion concentration & decreasing
hydroxide (OH-) concentration à more ACIDIC
o As move to the right of the scale (towards 10^-14)
decreasing H+ ions concentration & increasing OHion
concentration -> more BASIC
Define pH neutral, acidosis and alkalosis:
• pH 7 = neutral; acid = base or H+ ion concentration = OH - ion concentration; we have the same # of H+ as OH-
Ex: HOH (H2O) -> HOH is one H+ ion & one OH-
• pH 7 = base solution
What the normal pH value of arterial blood?
• normal pH arterial blood = 7.4 (7.35 – 7.45)
o 7.45 = alkalemia or alkalosis
What is the normal pH value of venous blood?
• normal pH venous blood = 7.35
o Venous blood more acidic than arterial bc venous is
carrying more CO2 than arterial, which brings down
the pH
What are the pH limits to life?
• limits for life: 7 – 7.7 (???)->however have seen pH
values outside this range & pts have survived
What are the pH values of HCl acid, stomach acid, urine and NaOH?
o HCl acid: pH of 0 -> although need a highly
concentrated solution of HCl
o Stomach: pH of 1. Truly stomach pH is 1 – 3 depending on amt of HCl gastric parietal cells secrete. pH
of stomach is so low to inhibit bacterial growth & kills microorganisms
o Urine: pH 4 – 8, depending on physiologic conditions of body. Able to produce more acidic urine based
on that range than basic urine
o NaOH: pH 14 -> although need a highly concentrated solution of NaOH to achieve pH of 14
What is significant about the Henderson-Hasselbalch Equation and what is the formula?
HENDERSON-HASSELBALCH EQUATION
pH = 6.1 + log HCO3-/ CO2 (0.03)
So basically is = to kidney/lungs
• 0.03 is amt of CO2 dissolved in plasma
• Henderson-Hasselbalch equation allows us to calculate pH if have bicarb & CO2 level.
To maintain pH 7.4, ___ times more base than acid must be maintained
• to maintain pH 7.4, 20 times more base than acid must be maintained
• pH doesn’t change as long as ratio of base:acid is 20:1
o so if bicarb (base) goes up by a certain ratio & CO2 (acid) goes up by same ratio (keeping a 20:1 ration
b/t bicarb & CO2) ->pH doesn’t chx.
o Bicarb decrease & CO2 decreases in same ratios ->pH stays same
o Bicarb increases & CO2 stays same -> pH increases à alkaline
o CO2 decreases & bicarb stays same ->pH increases à alkaline
Define what compensation means in relation to acid base balance:
• Compensation: maintenance of normal pH by increasing or decreasing base to balance increase or decrease
in acid or increasing or decreasing acid to balance increase or decrease in base
o maintenance of pH can can be accomplished by:
-> increasing or decreasing amt of CO2 blowing off
-> increasing or decreasing amt of H+ excreting from body
->increasing or decreasing amt of bicarb reabsorbing from kidneys.
o If have primary resp disorders, kidneys will compensate for that
o If kidneys are cause of primary A-B disorder, respiratory system will compensate for that
Work the Henderson-Hasselbalch equation if the HCO3- is 24 and the CO2 is 40
• Example: o HCO3- = 24 mEq/L o pCO2 = 40 mmHg o Solve: 24/40 (0.03) 24/1.2 20 6.1 + common log 20 6.1 + 1.3 = 7.4
What are three ways the body maintains normal pH and what are the characteristics of each of them?
• Buffer systems: extracellular & intracellular
o Respond with fraction of second
o Buffer system is most rapidly responding system
• Respiratory system is the next to respond
o Acute regulation: 1 – 12 min
o Chronic regulation: 1 – 2 days
• Kidneys are the last to respond
o Respond in hrs to days, but once they do respond, kidneys are the strongest / most powerful system that
manage A-B balance
o Most powerful of all regulatory systems
o Can continue for extended periods to regulate A-B balance
What is the definition of a buffer system?
• Buffer system: 2 or more chemicals, so that when a strong acid is added to a solution, the strong acid is
buffered to a weak acid. If a strong base is added to that solution, it’s buffered to a weak base.
What are the characteristics of Bicarbonate as related to being a buffer agent?
• Bicarb – carbonic acid buffer system
o Not most powerful, but most important of buffer systems
o CO2 regulated by lungs & HCO3- by kidneys
o CO2↑ + H2O -> (CA) -> H2CO3 -> H+ + HCO3- or
CO2 + H2O
What determines which way the formula goes?(as related to Bicarbonate and AB balance?
- CO2 increases formula moves to the RIGHT.
* Bicarb increases formula moves to the LEFT.
What is the result when a strong acid(HCl) is combined with a weak base(HCO3-)? What is the outcome?
o Strong acid (HCl) + weak base (HCO3-) -> weak acid (H2CO3) + salt
§ In this example, added a strong acid (HCl) to a solution. It combines with a weak base (HCO3-) &
the result is a weak acid (carbonic acid) & salt as the byproduct
§ Started with a strong acid & buffered it down to a weak acid. That weak acid will have less of an effect on the solutions pH than the strong acid would.
What is the result when a strong base(NaOH) is combined with a weak acid(H2CO3)? What is the outcome?
o Strong base (NaOH) + weak acid (H2CO3) ->weak base (NaHCO3) + water
§ In this example, added strong base (sodium hydroxide) to a solution. It combines with a weak acid (carbonic acid) & yields a weak base (sodium bicarb) with the byproduct being water.
§ So we’ve taken a strong base added it to a solution & its buffered to a weak base. That weak base has less of an effect on the pH than the strong base would have.
In regards to the buffer system, what is the outcome and differences when a weak acid or base is added to a solution as opposed to a strong acid or base?
o OUTCOME: pH minimally changed by weak acid or weak base compared with the stronger acid or base
§ Buffer system has its limits. Strong acid added to a buffer system & is buffered to weak acid. But, if
keep adding strong acid, at some point the buffer system cannot buffer it to a weak acid any more.
§ So buffer systems have limits à keep adding strong acids & bases to it, there will be a point where it
cannot buffer that any more
What are the characteristics of protein buffers as related to acid base balance?
• Protein buffers
o Powerful & plentiful buffers
o Albumin & other extracellular proteins
o Hgb in RBCs
o Amino acids in these proteins can accept or donate H+ ions depending on what body needs at that time
o Body in a state of acidosis: those proteins are going to buffer the body fluids by accepting those H+ ions
& remove them from the extracellular fluid & increase pH back to normal.
o Body in state of alkalosis: proteins will release H+ into body fluids & bring pH down toward normal
• Effects of hypoalbuminemia & anemia on A-B balance à talked about earlier
What is the movement of H+ and K+ across the cell membrane in response to acidosis and alkalosis?
• Acidosis: H+ into cell & K+ out of cell = HYPERKALEMIA!!!
o Hyperkalemia most likely to occur R/T METABOLIC ACIDOSIS
o Body in state of acidosis, so have accumulation of H+ in extracellular fluid -> want to shift those H+
into cells. To maintain electrical neutrality a cation has to move out of the cell. H+ move into cell & K+
move out of cell à which can lead to significant
• Alkalosis: H+ ion out of cell & K+ into cell
o Metabolic alkalosis may cause mild hypokalemia
o Alkalosis = deficit of H+ in extracellular fluid à H+ moves out of cell into extracellular fluid & K+
move from extracellular fluid into cell
• Not very important in primary respiratory acidosis or alkalosis -> these are only associated with metabolic
acidosis & alkalosis
What are the treatments for hyperkalemia?
HYPERKALEMIA.
o Treatment of hyperkalemia:
§ First treat the met acidosis (need to fix the problem that started it)
§ Insulin -> moves K+ into cell & admin dextrose with it
§ Ca+ -> reestablishes TP. So TP has moved up, so RMP has further to go to elicit a response
§ Bicarb -> moves K+ back into the cell
§ Kayexalate
§ Dialysis
How does the respiratory system respond as a buffering system in acid base balance?
RESPIRATORY REGULATION OR A-B BALANCE
• Controls CO2 portion of Henderson-Hasselbach equation
• Increase in CO2 (caused by hypoventilation) = pH to acidic side
• Decrease in CO2 (caused by hyperventilation) = pH to alkaline side
• CO2 diffuses into CSF & decreases CSF pH
• Central medullary chemoreceptors monitor pH of CSF& increase rate & depth of ventilation
• Increase in CO2 -> pH of blood decreases -> pH of CSF decreases; medullary chemoreceptors send msg
to medullary inspiratory center to increase rate & depth of ventilations (to blow off more CO2) & bring pH
back up towards normal
• Opposite happens with decreased CO2
o Decrease in CO2 -> pH of blood increases -> pH of CSF increases (more alkaline); medullary chemoreceptors sense that & decrease rate & depth of ventilations to retain CO2 & bring pH back down toward normal
How is the renal system involved in Acid:Base Balance?
• Kidneys are last to respond but are the most powerful
• Can excrete urine with pH 4.5 – 8
• Acid urine if more H+ than HCO3
- excreted, which is typical especially in diets high in meat
o Eating meat increases acid load & urine pH is more acidic
• Alkaline urine if more HCO3- excreted than H+
What is the mechanism used by the renal system for acid:base balance?
• Filtered bicarbonate reabsorbed
o 99% of bicarb that is filtered from glomerulus into renal tubules is reabsorbed back into the body -> this
preserves bicarb load of the body; this isn’t adding NEW bicarb to the body
• Synthesis & reabsorption of NEW bicarbonate while buffering & excreting H+
o Buffering & excretion of H+ with inorganic phosphates
o Synthesis of ammonia (NH3) & excreting extra H+ as ammonium chloride (NH4Cl)
Describe the process of bicarb reabsorption in relation to the renal system involvement with acid:base balance.
• RULE: for every H+ secreted into the tubular lumen & excreted into the urine, a bicarbonate ion & Na+ ion are reabsorbed into the PTC/body fluids
• Bicarb reabsorption occurs in proximal tubules in kidneys
• Proximal tubule process ->->->->->
• In pic: tubular lumen, tubular cell & PTC
• Start with filtered bicarb (filtered through the glomerulus into tubular lumen)
• First have H+ that are being actively pumped out of tubular cell into tubular lumen & Na+ pumped out of tubular lumen & into tubular cell -> this is
secondary active counter transport.
• Have Na+ pumped in & H+ pumped out
• Bicarb combines with H+ that was just pumped out into tubular lumen to form carbonic acid.
• In presence of CA, carbonic acid breaks down into water & CO2.
• CO2 diffuses into tubular cell & combines with H2O (in presence of CA) to form H2CO3- inside tubular cell
• That carbonic acid breaks down into H+ & bicarb.
• That bicarb is then reabsorbed into PTC & into body fluids.
• So, we’re reabsorbing bicarb ->we’re maintaining the bicarb load of the body. 99% of bicarb that’s filtered
is reabsorbed back into PTC.
• The rule holds true: for each H+ secreted, a Na+ & bicarb are reabsorbed.
How is primary active secretion of H+ ions accomplished by the renal system in response to acid:base balance?
• CO2 & water yield carbonic acid & then disassociates
into bicarb & H+
• Then H+ are actively pumped out into the tubular
lumen This isn’t countertransport of H+; this is primary active transport of H+ out of the tubular cell.
• Cl- follows the H+. H+ + Cl- = HCl. HCl acid in the renal tubules. iIf that HCl acid goes thru renal tubules, into kidneys, into ureters, into bladder & out the urethra -> burn on urination if excreting HCl acid.
• Luckily those H+ that are actively pumped out into tubular lumen are immediately buffered by bicarb
How are H+ ions buffered by inordinate phosphates?
• Phosphate buffer system is composed of HPO4– (base phosphate) & H2PO4- (acid phosphate)
• The phosphate buffers handle the excess H+ when HCO3- isn’t available to combine with H+
• After HPO4– combines with H+ to form H2PO4
-, it can be excreted as NaH2PO4 (sodium acid phosphate), carrying with it excess H+ à this gets rid of the extra H+; this is one of the ways the kidneys deal with A-B imbalances
• In pic have: tubular lumen, tubular cell & PTC
• Have Na2HPO4: di-sodium base phosphate.
When Na2HPO4 is broken down, it yields base
phosphate & 2 Na+.
• Base phosphate (HPO4–) combines with H+ to
form acid phosphate (H2PO4-). H2PO4- + Na+ =
sodium acid phosphate (NaH2PO4), which is
eventually excreted into the urine -> this
removes H+ ions from body fluids & excretes
H+ in urine
• At the same time in the tubular cell, have water
& CO2 combining to form carbonic acid (H2CO3). H2CO3 breaks down into H+ & bicarb. Bicarb is then reabsorbed back into PTC.
In regards to the buffering of H+ with inordinate phosphates, do you see an associated bicarb in the tubular lumen?
No! This is BRAND NEW BICARB being added to
body fluids & absorbed into PTC
• The rule holds true: for each H+ secreted & excreted into urine, reabsorb one bicarb & one Na+
What are the characteristics of the AMMONIA (NH3) – AMMONIUM CHLORIDE (NH4Cl) BUFFERING OF H+?
• Very powerful buffer system in renal tubules that depends on glutaminase enzyme
• Generates much NEW bicarbonate
• Activity of the enzyme glutaminase, which begins the process, is pH dependent
• When pH becomes more acidic: glutaminase is more active -> MORE H+ secreted & excreted; more NEW
bicarbonate synthesized & reabsorbed
o Increases pH by excreting H+ & creating NEW
bicarb
• When pH becomes more alkaline: glutaminase is
LESS active -> less H+ secreted & excreted; less
NEW bicarbonate synthesized & reabsorbed
o Decreases pH back to normal by excreting less
H+ & creating less NEW bicarb
• In this example the pH of body fluid is more acidic
-> making glutaminase enzyme more active.
• Glutaminase is an enzyme that breaks down
glutamine to NH3 (ammonia). NH3 then moves into
tubular lumen & combines with H+ to form NH4
(ammonium)
• NH4 combines with Cl- yielding NH4Cl à NH4Cl is
then excreted in the urine
• So we’re getting rid of H+ ions
• Also have water + CO2 = carbonic acid, which
breaks down in H+ & bicarb à that a BRAND NEW BICARB being added to body fluids & PTC
• The rule holds true: H+ secreted into tubular lumen (& eventually into urine) & reabsorbed one bicarb & one
Na+
What is the significance of high anion gap versus normal anion gap in regards to metabolic acidosis?
• Any time your interpretation of ABG results in metabolic acidosis, have to determine if it’s a normal or high
anion gap metabolic acidosis à do this to ID what’s causing the acidosis
• Anion gap: Difference in major measured cations (Na+ & K+) & major measured anions (bicarb & Cl-)
What is the formula used to determine anion gap?
• AG = (Na+ + K+) – (HCO3- + Cl-)
What is a “normal” anion gap?
• Normal AG = 12 – 18 mEq/L
o This is assessing the major measured cations & anions (not saying 12 – 18 mEq/L more cations than the anions bc we need chemical neutrality [so cations have to = anions])
What is the significance of a high anion gap?
• If AG is increased (> 18 mEq/L), some unmeasured anion is contributing to the gap. That anion must be identified –> have to ID the anion to ID the cause of metabolic acidosis.
o As unmeasured anion increases, the Cl- decreases to maintain electrical neutrality
o Additionally, the HCO3- decreases as it is used to buffer the acidosis
o So, if bicarb is decreasing to buffer the acidosis & Cl- decreases the maintain chemical neutrality, then
measured anions gets smaller & cations stays same -> a smaller # of anions is subtracted from cations
o So gap b/t measured cations & measured anions increases
What is the significance of a normal anion gap?
• Normal AG metabolic acidosis is HYPERCHLOREMIC
o normal AG met acidosis is usually caused by decrease in bicarb or an increase in Cl-.
o Ex: give NS bolus. This causes hyperchloremic met acidosis bc increase Clo
Ex: pt with diarrhea loses lots of bicarb. As bicarb level decreases, the Cl- increases to maintain electrical neutrality.
What are some examples of high AG metabolic acidosis & associated unmeasured anion causing the acidosis?
o Shock – lactate
* Shock -> decreased perfusion -> anaerobic metabolism -> lactate production. Lactate is the unmeasured anion that’s leading to high AG met acidosis.
* As lactate increases, Cl- decreases to maintain electrical neutrality -> causing hyperchloremia.
o Cardiac arrest – lactate
* cardiac arrest same thing happens -> decreased perfusion -> anaerobic met -> lactate production
o Renal failure – a number of anions that are usually renally excreted but cant be bc of kidney fx -> so get
anion buildup & cause high AG met acidosis
o Lactic acidosis – lactate
o DKA – ketone bodies
* Ketone bodies are anions that cause a high AG met acidosis
* 3 ketone bodies made during DKA: acetoacetic acid, beta-hydroxybutyric acid & acetone
* ketone bodies vs ketoacids à ketoacids involved with krebs cycle. Ketone bodies are developed
when more acetyl coenzyme A is produced than what can be cycled through Krebs cycle à which is
what DKA leads to: production of ketone bodies
o Malnutrition/starvation – ketone bodies & others
o Salicylate overdose
o Ethylene glycol (antifreeze) – metabolites of ethylene glycol that cause the high AG met acidosis
In mixed compensation, how do you determine the primary problem and the greatest degree of compensation?
• PaCO2
o Subtract pt PaCO2 value from normal PaCO2 (40 mmHg)
o Divide the difference by 40 to determine % chx from normal 40 mmHg – PaCO2/40 mmHg
o Note direction of change from normal & how it relates to pt pH value
• HCO3-
o Subtract pt HCO3- from normal HCO3- (24 mEq/L)
o Divide the difference by 24 to determine % chx from normal 24 mEq/L – HCO3-/24 mEq/L
o Note direction of change from normal & how it relates to pt pH value
• The larger % chax is the primary problem
• The smaller % chx is the % (degree) of compensation OR in mixed disorders, the % (degree) of contribution
to problem
What two components make up mean systemic arterial pressure?
- Cardiac Output
- Total Peripheral Resistance
Mean systemic arterial pressure= Cardiac Output x Total Peripheral Resistance
What two components make up mean cardiac output?
- Stroke Volume
2. Heart Rate
What two components make up total peripheral resistance?
- Arteriolar Radius(major influence on PVR)
2. Blood Viscosity(minor influence on PVR)
When blood circulation reaches the ____ the blood pressure is a single digit number.
arterioles
The major influence on heart rate is the ANS. The parasympathetic mainly affects HR at the ___ node by what NMT with what receptors? The sympathetic affects HR at these nodes and by what NMT with what receptors?
Parasympathetic –> SA Node –> Ach(neurotransmitter)/M-2(receptor)
Sympathetic –> SA Node, AV Node, Ventricular Contractile Fibers –> NE(neurotransmitter)/B-1(receptor)
Stroke Volume is influenced by the ___ and ___.
- Sympathetic NS
- LEVD/LVEDP(venous return)
What is the cascade determining LVEDV/LVEDP?(4)
- atrial vol/pressure
- venous return
- venous pressure
- venous tone(sympathetic nervous system activity to the veins) NE/EPI(NMT) a-1/B-2(receptors)
