ferg 2
Terms
undefined, object
copy deck
-
for which of teh following do you care about anion gap and osmolar gap?
1. metabolic acidosis
2. metabolic alkalosis
3. respiratory acidosis
4. respiratory alkalosis - metabolic acidosis
- formula to calculate anion gap
- anion gap = [Na] - ([Cl-] + [HCO3-])
- what is the normal value for anion gap?
- 12 +/- 2 mEq/L
- elevated anion gap metabolic acidosis could be due to...
-
collection of excess acids:
-lactic acid
-ketoacids
-toxic acids (e.g. methanol)
-kidney failure (organic acids)
"MUDPILES"
Methanol
Uremia (organic acids)
Diabetic ketoacids
Paraldehyde
Isoniazid
Lactic acd
Ethylene glycol (antifreeze)
Salicylates - normal anion gap metabolic acidosis could be due to...
-
1. diarrhea (loss of HC03-)
2. loss of HCO3- from kidneys - how is is normal anion gap metabolic acidosis differ from hi anion gap metab. acidosis in terms of how HCO3- is lost?
-
in hi anion gap M.A., the HCO3- is lost b/c it combines with xcess acid
in non-anion gap M.A. there is 'simple' loss of HCO3- via the gut (diarrhea) or via the kidneys (e.g. RTA) - how do you calculate osmolar gap?
-
osmolar gap = measured - calculated
calculated = 2[Na] + [urea] + [glucose] + [EtOH] - what does an osmolar gap indicate?
- that there are significant uncharged osmoles present in the serum (usually toxic alcohols like methanol) that aren't accounted for in the formula
- H+ LOSS = HCO3- GAIN!!!
- just to push the point!
- 2 major buffer systems in the body
-
1. BBS
2. intracellular proteins - 2 minor buffer systems in teh body
-
1. inorganic intracellular phostphate
2. bone (chronically) - how is the body losing bicarb?
- via CO2 when we breathe
- where does most of the HCO3- reabsorption occur? what percentage occurs here?
- in the PCT. 85%
- where does non-PCT reabsorption of HCO3- occur?
-
in the TAL (15%)
paracellular pathways (20%) - in order to get NEW HCO3-, what has to happen? MOA?
-
H+ must get secreted AND trapped in the urine.
ways this can happen is if H+ attaches to a titratable acid (such as HPO4- or HSO4-) or ammonia (NH3) - where are the 2 places in the nephron where NH4 can be secreted into the lumen?
- the PCT and the DT
- list the 2 fates of glutamine once it is metabolized in kidney
- in kidney, glutamine is broken down into 2NH4+ and 2HCO3-. If the NH4s are put into the urine, you have a net loss of acid from the body. The 2HCO3- are taken up into the blood, and this is considered the 'generation of new bicarb.' However, if the NH4+ go to the liver instead to get converted into urea, this process releases 2H+ into the blood, which combine with the 2HCO3- that were originally generatede from the breakdown of glutamine. Thus, the charges balance out, and youi have no new generation of HCO3-
- what are the 4 modulators of DISTAL TUBULEAR acid/base?
-
1. Na+
-aldosterone
-lumen electric potential
2. K+
3. ATP availability
4.pH - in RTA, would you have a normal A/G metabolic acidosis, or a wide A/G metabolic acidosis
- a normal A/G metabolic acidosis. Why? b/c HCO3- is "simply" being eliminated from the body (i.e. not being reabsorbed) - its not that its combining with any excess acids.
- does RTA cause chronic metabolic acidosis?
-
yes - its a problem with reclaimin/regererating bicarbonate
it is a non-A/G metabolic acidosis - what would the effects of a carbonic anhydrase inhibitor be?
-
decrease the formation of H+
lead to an alkaline urine; retain H+ (therefore could be a cause of RTA
prevent Na+ from being reabsorbed via Na/H pump (b/c it retains H+). Thus acts as a weak diuretic (e.g. acetazolamide) - describe the SCr vs. GFR curve
- as GFR initially declines, this is accompanied by only a small elevation in serum creatinine. Thus, an elevation of Scr from 100 to 200 represents a greater decline in renal function than an increase in SCr from 300 to 400. SCr is also therefore a late indicator of declining renal f'n.
- how can you distinguish b/w a pre-renal vs. intrinsic cause of RTA in terms of: Una
-
pre-renal Una < 10
instrinsic Una >20
(inability to reabsorb Na in intrinsic) - how can you distinguish b/w a pre-renal vs. intrinsic cause of RTA in terms of: FeNa
-
pre-renal FeNa <1%
intrinsic FeNa >2% - how can you distinguish b/w a pre-renal vs. intrinsic cause of RTA in terms of: Uosm
-
pre-renal: Uosm > 500
intrinsic: Uosm < 300 - how can you distinguish b/w a pre-renal vs. intrinsic cause of RTA in terms of: SpGr
-
pre-renal: >1.018
intrinsic: <1.012 - how can you distinguish b/w a pre-renal vs. intrinsic cause of RTA in terms of: sediment (casts)
-
prerenal: hyaline casts
intrinsic: granular cast, dysm. RBC, cellular cast, crystal/oxalate/Uric - where is ADH made (specifically)
- paraventricular and supraoptic nucleus in hypothalamus
-
which of the following does ADH act on?
PCT, LOH, DCT, CCD, MCD - DCT, CCD, MCD
- if you have a decreased effective circulating volume, are you necessarily hypovolemic?
- no - you could have normal/hi intravascular volume; the problem lies in the fact that it is poorly distributed, or that there is low CO
- low effective circ. volume is going to cause 3 things to happen. what are they?
-
1. activation of thirst sensation
2. ADH secretion
3. SNS activation - RAS - NaCl reabsorption - hyponatremia, or low serum [Na] has two requirements:
-
1. source of free water
2. ADH is acting - hypernatremia, or hi serum [Na] has two requirements:
-
1. no source of free water (otherwise it would be absorbed in other places besides the DCT/CD
2. ADH not acting (centra/nephrogenic DI) - how is polyuria usually defined in terms of volume excreted?
- 3 L/day in an adult
- how is urine volume calcuclated?
- urine volume = (# osmoles)/Uosm
- 2 things that could cuase an increase in urine volume
-
1. osmotic diuresis (hi osmoles)
2. water diuresis (urine osmolality is too low b/c the kidney can't concentrate urine) - not all osmoles can lead to osmotic diuresis. Only effective osmoles can. 4 examples are
-
"GUMS"
1. glucose (Diab. mellitus)
2. urea (hi protein, GI bleed - only place in body where urea is an effective osmole!)
3. mannitol (iatrogenic)
4. salts (Na, BHB, NaCl) - 2 ways of determining whether polyuria is due to (i) water diuresis or (ii) osmolar diuresis
-
a) could measure Uosm.
-if Uosm > 250 mosmol/l, then its osmolar diuresis
-if Uosm <250 mosmol/l, then its water diuresis
2. assuming that you know Uosm, measure the 24 hour urine output. using these two values, calculate the # of osmoles excreted. Knowing that an avg # of excreted osmoles is <900 in a 75 kg male, you can figure out whether the polyuria is due to greater excretion of osmoles - once you know that polyuria is due to osmotic diuresis, what calculation do you perform next? why?
- calculate the osmolar gap. b/c you want to determine what osmoles are responsible for the polyuria. Are they "measured" (Na, urea, glu) or "non-measured" (ketoacids, mannitol)
- name one occasion in which water diuresis is deemed appropriate
- psychogenic DI - body NEEDS to get rid of excess water consumed
- if the osmolar gap is greater than what value can you conclude that osmolar diuresis is due to unmeasured osmoles
- if Uosm gap is >100
-
definition of hyperkalemia?
definition of hypokalemia? -
plasma [K]> 5 mEq/L
plasma [K] < 3.5 mEq/L - describe the external and internal means of K balance
-
external: GI absorp - (urine + stool) excretion
internal: 98% ICF, 2% ECF (any compartment shift will change the K balance) - would a K shift from ICF to ECF be described as catabolic or anabolic?
- catabolic
- what 2 things could increase the K+ movement INTO ICF?
-
insulin
B-agonists - ROM-K is characteristic of what part of the renal tubule?
- LOH
- aldosterone secretion is triggered either by _____ or ______
-
AII
hi serum [K] - 3 actions of aldosteron on teh principle cell
-
1. activates existing ENaC
2. produces new ENaC
3. upregulates Na/K pump on basolateral membrane, thus driving the gradient - a negative/positive lumen will favor K secretion
- negative lumen
- how does flow influence the secretion of K in the CCD?
- the greater the flow, the greater the secretion of K
- 3 ways you could get hypokalemia
-
1. renal K wasting
2. reduced dietary intake
3. compartmental shift into ICF - what is the major concern with hypokalemia?
- cardiac arrhythmia
-
which of the following drugs could cause K wasting?
NSAIDS
purgatives
diuretics
anti-emetics
laxatives -
purgatives
diuretics
laxatives - when treating hypokalemia, would you first increase body content of K? or first increase the serum concentration of K?
- first increase serum concentration of K. This is because body content of K is only loosely related to the plasma [k]
- what does pseudo-hiK refer to?
- a dx of hyperkalemia that is false b/c the measured hi K is due to a technical error (e.g. tight tourniqet, or hemolysis) i.e. its the doctor's fault THE PATIENT DOESNT ACTAULLY HAVE HYPERKALEMIA
- what types of things could elevate your K intake?
-
salt substitutes (KCl)
transfusion of old blood
IV K+
drugs containing K
blackstrap molasses
geographia = clay eaters!! - what might cause a redistribution of K from the ICF to the ECF (causing hyperkalemia)
-
lack of insulin
b-antagonists
cell damage
medications
fasting (catabolic state)
physical exertion
hyperchloremic acidemia - would hypercloremic acidemia cause hyper or hypokalemia?
- hyperkalemia
- would reduced flow throught eh CCD result in hyper or hypokalemia?
- hyperkalemia (recall that luminary flow is a determinant of K secretion)
- would digitalis result in hyperkalemia or hypokalemia (think about its MOA)
- hyperkalemia (Na/K ATPase will keep Na inside the cell, and K outside)
- if you have an INAPPROPRIATELY low TTKG, what could this be due to? Name 2 things
-
1. defective aldosterone responses (hyporeninemia, drugs...)
2. increased Cl- reabsorption - what salts can you administer to antagonsize the cardiac effectws of HiK
- Calcium salts
- what is the preferred method for shifting K into the ICF from teh ECF? waht other methods are there to shift K into ICF
-
insulin + glucose infusion
B-agonists - what are 3 ways you could remove K from teh body?
-
1. increase renal excretion (loop diuretic, mineralocorticoid, CA inhibitor)
2. increasing GI excretion (K adsobing resin, kayexalate
3. dialysis (HD more effcient that PD)