Approach to Acid/Base (Selby)

Question 1

What kind of disturbances exist in Metabolic Acidosis

Answer 1

HAGMA
NAGMA (hypercholermic acidosis)

Question 2

What kind of disturbances exist in Metabolic Alkalosis

Answer 2

Salie-Responsiveness (hypovolemia… contraction alkalosis or chloride deficiency alkalosis)

Saline-on-Responsive (euvolemia)

Question 3

What kind of disturbances exist Respiratory Acidosis

Answer 3

Acute

Chronic

Question 4

What kind of disturbances exist Respiratory Alkalosis

Answer 4

Acute

Chronic

Question 5

Metabolic Acidosis formula

Answer 5

Winter’s formula

PCO2 = 1.5[HCO3] + 8 +/- 2

Question 6

Metabolic Alkalosis formula

Answer 6

PCO2 will increase by 0.7 for each 1.0 increase in HCO3 above 24

ΔPCO2 = ([HCO3] - 24) * 0.7

Question 7

Respiratory Acidosis Acute Formula

Answer 7

HCO3 will increase by 1 for every 10 increase in PCO2 above 40

ΔHCO3 = (CO2-40) * 0.1

Question 8

Respiratory Acidosis Chronic Formula

Answer 8

HCO3 will increase by 3.5 for every 10 increase in PCO2 above 40

ΔHCO3 = (CO2-40) * 0.35

Question 9

Respiratory Alkalosis Acute formula

Answer 9

HCO3 will decrease by 2 for every 10 decrease in PCO2 above 40

ΔHCO3 = (CO2-40) * -0.2

Question 10

Respiratory Alkalosis Chronic formula

Answer 10

HCO3 will decrease by 5 for every 10 decrease in PCO2 above 40

ΔHCO3 = (CO2-40) * -0.5

Question 11

Normal Anion Gap

Answer 11

12 +/- 2

Question 12

Paraproteinemias present as

Answer 12

low anion gap values

Question 13

lithium/bromide/iodide toxications present as

Answer 13

low or even negative anion gap values

Question 14

Anion Gap formula

Answer 14

Na - (HCO3 + Cl-)

Question 15

RTA or diarrhea present as

Answer 15

NAGMA

Question 16

For every 1 g/dL drop in Albumin AG changes by

Answer 16

drops 2.5

Question 17

If AG is calculated as 12 but serum albumin is 2 lower than normal what is the real AG

Answer 17

17

Question 18

Serum osmolality calculation

Answer 18

2(Na) + (Glucose/18) + (BUN/2.8)

Question 19

Osmolar Gap

Answer 19

Calculated osm - measured osm

Question 20

normal osmolar gap

Answer 20

<10

Question 21

if AG is 20

Answer 21

suspect alcohol ingestion

Question 22

Delta - Delta Gap calculation

Answer 22

calculated AG(x) - normal AG(12)
Delta HCO3 == normal HCO3 (24) - calculated delta gap

so

x-12 = y 
24-y= delta gap

Question 23

if measured HCO3 was close to 16 in delta detla

Answer 23

no additional acid base present

Question 24

if measured HCO3 was >16 in delta delta

Answer 24

then additional metabolic alkalosis is present in addtion to HAGMA

Question 25

if measured HCO3 <16 in delta detla

Answer 25

non-gap metabolic acidosis is present in addition to HAGMA

Question 26

what is acidosis

Answer 26

pH <7.35

Question 27

what is alkalosis

Answer 27

pH >7.44

Question 28

normal HCO3

Answer 28

24

Question 29

normal PCO2

Answer 29

40

Question 30

normal anion gap

Answer 30

12

Question 31

normal osmolar gap

Answer 31

10

Question 32

HAGMA differential

Answer 32

``` GOLD MARK Glycols (ethylene and propylene) Oxoproline (acetaminophen toxicity) L-lactic acidosis D-lactic acidosis (colonic matbolization of glucose and seen in short bowel syndrome) ``` Methanol Aspirin Renal failure Ketoacidosis (alcoholic, diabetic, starvation)

Question 33

pyroglutamic acidosis

Answer 33

more in women who are malnourished or critically ill seen through urinary organic acid screen treated with halting of acetaminophen/IVF/N-acetylcysteine

Question 34

DDx for increased osmolar gap

Answer 34

ME DIE Methanol Ethanol ``` Diethylene glycol (mannitol) Isopropyl alcohol (not associated with met acidosis) Ethylene glycol ``` ketoacidosis and lactic acidosis smaller increase in osmolar gap

Question 35

NAGMA DDx

Answer 35

DURHAAM he said the three we need to know are Diarrhea Ureteral diversion (ileal conduit) Renal tubular Acidosis Hyperalimentation Acetazolamide Addison's disease Miscellaneous (glue sniffing sits here... pancreatic fistula, medications)

Question 36

Proximal RTA (type 2)

Answer 36

decreased in capacity of PT to reabsorb HCO3 loss of HCO3 in urine because the TAL and DT cannot compensate creating acidosis eventually the serum HCO3 will decrease and PT/TAL/DT are no longer overhwlemed and a new steady state develops

Question 37

Proximal RTA (type 2) etiology in kids

Answer 37

most common cause in kids is cystinosis

Question 38

Proximal RTA (type 2) etiology in adults

Answer 38

most common cause in adults is falconi syndrome and secondary is multiple myeloma

Question 39

clinical manifestation of proximal RTA (type 2)

Answer 39

NAGMA with or without proximal tubular dysfunction hypokalemia which is milder than distal RTA (type 1)

Question 40

diagnosis of proximal RTA (type 2)

Answer 40

urine pH can be high or low depending on serum HCO3 urine ph <5.5 when in new steady state UAG can be positive or negative

Question 41

Urine Anion Gap

Answer 41

used to determine if renal or non-renal in NAGMA NH4Cl excretion which indicated appropriate urinary acidification... but most labs don't measure this UAG = (UrineNa + Urine K+) - Urine Cl

Question 42

if UAG is negative

Answer 42

indicated appropriate distal nephron urinary acidification

Question 43

if UAG is positive

Answer 43

indicates inappropriate distal nephron urinary acidification

Question 44

Distal RTA (Type 1)

Answer 44

Pts are unable to acidify their urine decreased H+ ion secretion gradient defect can be caused by amphotericin or fungal infections lack of H+ secretion prevents acidification and excretion of ammonium leading to prevention of HCO3 reabsorption in distal tubule

Question 45

Distal RTA (Type 1) etiology and manifestation

Answer 45

can be primary/acquired commonly seen with Sjogren's Syndrome Glue sniffing another common cause due to toluene associated with nephrolithiasis or nephrocalcinosis

Question 46

Distal RTA (Type 1) diagnosis

Answer 46

NAGMA unable to acidify urine pH <5.5 Hypokalemia from urinary K wasting UAG is positive

Question 47

Hyperkalemic RTA (Type 4)

Answer 47

Dysfunction from impaired excretion of H+ and K causing NAGMA/Hyperkalemia Deficiecy of circulating Aldosterone (DM and NSAIDs/Beta blockers/ACEi/Heparin) Aldosterone resistance in CD (interstitial renal disease such as sickle cell/obstructive uropathy/lupus or drugs including amiloride/triameterene/spironolactone/trimethoprim) impaired Na reabsorpion and resulting hyperkalemia

Question 48

Hyperkalemic RTA (Type 4) clinical manifestation and diagnosis

Answer 48

usually asymptomatic/NAGMA/hyperkalemia patients are normally 50-70 with history of diabetes or CKD diagnosis urine pH>5.5 UAG positive

Question 49

Metabolic Alkalosis DDx

Answer 49

``` 5 important ones Hypokalemia Vomiting/nasogastric tube suctioning diuretics volume depletion Mineralocorticoid excess ``` ``` secondarily Bartter and gielman posthypercapnic alkalosis hypercalcemia/milk-alkali syndrome diarrhea (rarely) ```

Question 50

Respiratory Alkalosis DDx

Answer 50

anything that increases respiratory rate or Tidal Volume | there's a big table

Question 51

Respiratory Acidosis DDx

Answer 51

anything that lowers respiratory rate/tidal volume, increses dead space, or worsens an obstruction inadequate ventilator setting can increase CO2 production (there's a big list in the slideshow)

Question 52

Acid-Base Stepwise Approach

Answer 52

Determine if Acidosis or Alkalosis determine if primary disturbance is metabolic or respiratory calculate anion gap if met acidosis is present calculate appropriate compensation for primary acid-base disorder