Acid Base Flashcards
Primary buffer
Bicarb = extracellular
Secondary buffer
Intracellular
Hours
3rd step
*Lungs = minutes to hours
*Renal base-then-acid excretion
Hours to days
If too high a load, overwhelms kidney
Formula
H + HCO3- H2CO3 CO2 + H20
Mechanisms of acidosis
- increased acid production/load
- decreased acid excretion
- loss of bicarb ions
Increased acid load
ORGANIC
- lactic acid->lactic acidosis
- Ketoacids (b-Hydr/ acetoacetate) = DM, ETOH, Starvation
INORGANIC
*HCL
*Ammonium cloride
RAPIDLY DEVELOPING ACIDOSIS
Decreased acid excretion
- Acid = mostly from metabolism of sulfur-containing amino a
- H secreted to lumen (NH3to NH4) (HPO to
- Ammonium excretion UPs dramatically in respons to acid
- renal failure
- incre?
Renal failure
Decrease
- up NH4
- down HCO3
- increase unmeasured anions
Type 1 distal renal tubular acidosis
- gfr preserved, urine pH=>5.3
- less H+ secreted in tubular to combine with NH4 -> less excretion = Impaired H-ATPase pump
- less carbonic anhydrase
- up luminal permeability to H+
- DISTAL tubule = more severe
- 1ary = congenital,
- 2ndary = Meds, Sjorgen’s syndrome, RA, SLE
3rd mech acidosis
Loss of bicarb
- Big tubule = Colon (diarrhea = rich in Bicarb + sodium. Na loss, Less HCO3, more Cl, unmeasured ions to not change)
- small tubule = urethra (tube disfuction- proximal renal tubule acidosis type 2 renal tubular acidosis, Down Proximal Bicarb reabsorption, will have loss unless distal tubule makes up for it)
Clin manifestations
Metabolic acidosis
*UP ventilation
*DOWN myocardial contractility (less pH 7.2)
*Ventr arrythmia
*down vascular resistance
*GI = N/V , ab pain, DIarrhea (especially DM)
MSK
*muscle weakness, osteomalacia, hypercalcuria
CNS
*lethargy, coma
INFANTS
*impaired bone growth, listlessness
Serum Anion Gap
UA-UC = Na - Cl + bicarb
Anion gap = UA - UC =
Anion gap
=Na - (Cl + HCO3)
*correct AG = (4.4-ablumin) - 2.5
AG normal = 10-12
12+ abnormal AG acidosis
High anion gap metabolic acidosis
Citrate
*Uremia
Toulene
Ethanol
*DM/ETOH/Starve ketoacidosis Iron Methanol Paraldehyde *Lactate Ethelyne Glycol Salicylate
*THESE ARE NOT INGESTED
AG acidosis
CKD
*Dietary =>sulfate ions (not reabsorbed is secreted)
STAGE 2-3 = normal AGmetabolic acidosis (defective secretion/reabsorption)
Stage 4-5 CKD = high AG M acidosi
*retention of H ions + sulfate ion, less nephron mass/GFR
AG acidosis
DM ketoacidosis
*Insulin deficiency = UP free fatty acid = acetone production
*Glucagon excess = altered hepatic metab
Free fatty acid to ketoacids
DKA
Renal consequences
*insulin deficiency
*more K coming out of cells
OSMOTIC DIURESIS
*Loss of hypotonic fluid
*Loss of ketoa acid ions
AG acidosis
Lactic acidosis
- byproduct of pyruvate acidosis
- if lactate up = pyruvate inbalance, or down lactate utilization
- DX = lactate level, venous pH down *upCO2 cuz DOWN pulmonary blood flow (hypoperfusion)
- Tx : underlying disorder
DX Acid base
1= acidemic/alkalemic? 2= primary disorder, respiratory/metabolic? 3=respiratory (acute/chronic?) 4=Metabolic (Anion gap?) 5= Mixed? Gap/nongap? 6= compensated? If not, why?
Delta gap
Change in AG/Change in HCO3= 1 = change in bicarb CONSISTENT with change in AG
NO NON-ION GAP PROCESS
Alkalosis
High extracelluar PH
Primary elvation of bicarb
Respiratory compensation
Proton loss =
Increase in bicarb concentration
- GI = n/v, adenoma, ..
- renal = DIURETICS, …
Loop diuretic
Up Na delivery to Principal cell, Tubular lumen more negative, H-+ pumped
Contraction alkalosis
Lose fluid
*higher concentration bicarb = alkalosis
Alkalosis
Add Bicarb
*Nabicarb
*milk-alkali syndrome
*hypercalcemia
*renal Bicarb reabsorption
*massive blood transfusion (citrate load)
CHECK HISTORY
Bicarb reabsorption in nephron
Most PCT
Can malfunction in other places
*Na reabsorption = Bicarb reabsorption
Alkalosis
Intracellular H movmenet
Hypokalemia = K moves out cell, H in
Refeeding syndrome = up increase, H + K movement into cells
Maintanence of Met Alkalosis
*kidney can’t excrete HCO3
- hypovolemia/chloremia/kalemia
- mineralocorticoid excess
Volume depletion
Alkalosis
Nephron main job = reabsorb Na (bicarb comes with)
- ang 2 increases Na-H exchanger
- low pH in PCT ups bicarb reabsoprtion
Free bicarb can’t bind with H to be excreted in cell to lumen, so goes into blood
Volume depletion
Alkalosi
*2ndary hyperaldosteronism???
Alkalosis
Cl- depletion
- decrease Cl to macula densa = 2ndary hyperaldosteronism
- UP Hatpase to mained electroneurtrality
- DOWN Clbicarb exchange in intercalated cells, bicarb reabsoprted into blod
Giving chloride to volume depleted tx without tx volume
Cl
Hypokalemia
Alkalosis
- Up KHatpase = increase H secretion
- UP KH transcellur exchagne = up H secretion
- Up renal NH4 generation, Up Bicarb generation
Alkalosis
*Down ventilation
*ventr arrythmia
*ortho HypoTN
*GI = N/V
*MSK = cramping, tetany
CNS = confusion, seizures
Alkalosis
Cl responsive
- w/ Extracellular fluid volume contraction (conserve Cl)
- urine CL <20
- Tx = NaCl (mabye K repletion)
Alkalosis
Cl Resistant
- w/ extracellular fluid volume expansion , HTN
- depletion NaCL NOT RESPONSIBLE
- urine cl high/normal >40
- NaCl doesn’thelp
- treat Dz
Metabolic Acidosis - Normal AG
Causes
H yperalimentation A cetazolamide R enal Tubular Acidosis D iarrhea U tereral diversion (neobladder) P ancreatic fistula (bicarb loss)/ Post-hypocapnea S pironolactone
RTA type 2
- PROXIMAL - less severe
- HCO3 wasting
- urine pH = variable
- 1ary = congenitall
- 2ary = CA inhibitor, autoimmune dz, meds
RTA type 4
- Urine pH <5.3
- HYPER K
- Aldosterone deficiency (congenital/meds), Tubular resistance to aldosterone (meds, tubulointerstitial dz)
Metabolic Acidosis = High AG
Causes (ingestion + non-ingestion)
C itrate U remia T oluene E toh R enal failure/Rhabodomyelosis
D iabetic ketoacidosis I ron / Infxn / isoniazide M ethanol P araldehyde L actate E thylene glycol S alicylate
Metabolic Acidosis - High AG
Non-ingestion causes
- Uremia
- Ketoacidosis
- Lactic Acidosis (sceptic)
Metabolic Alkalosis often w/
- Hypo Cl
- Hypo K
- hypovolemia
- high aldosterone (?)
Kidney H/HCO3 exchange
- excrete H to bring in HCO3 = PCT
* UP in high pCO2, hypovolemia, hypokalemia
Metabolic Acidosis = High AG
Mech
- Acid in blood (H + anion) dissociates
* H to bicarb, then ion accumulates in serum
Metabolic acidosis = Normal AG
- lost Bicarb replaced by Cl-
- AG normal, Cl serum high
- diarrhea ,RTA II = loss of Na Bicarb (?)