What kind of disturbances exist in Metabolic Acidosis
HAGMA NAGMA (hypercholermic acidosis)
What kind of disturbances exist in Metabolic Alkalosis
Salie-Responsiveness (hypovolemia… contraction alkalosis or chloride deficiency alkalosis)
Saline-on-Responsive (euvolemia)
What kind of disturbances exist Respiratory Acidosis
Acute
Chronic
What kind of disturbances exist Respiratory Alkalosis
Acute
Chronic
Metabolic Acidosis formula
Winter’s formula
PCO2 = 1.5[HCO3] + 8 +/- 2
Metabolic Alkalosis formula
PCO2 will increase by 0.7 for each 1.0 increase in HCO3 above 24
ΔPCO2 = ([HCO3] - 24) * 0.7
Respiratory Acidosis Acute Formula
HCO3 will increase by 1 for every 10 increase in PCO2 above 40
ΔHCO3 = (CO2-40) * 0.1
Respiratory Acidosis Chronic Formula
HCO3 will increase by 3.5 for every 10 increase in PCO2 above 40
ΔHCO3 = (CO2-40) * 0.35
Respiratory Alkalosis Acute formula
HCO3 will decrease by 2 for every 10 decrease in PCO2 above 40
ΔHCO3 = (CO2-40) * -0.2
Respiratory Alkalosis Chronic formula
HCO3 will decrease by 5 for every 10 decrease in PCO2 above 40
ΔHCO3 = (CO2-40) * -0.5
Normal Anion Gap
12 +/- 2
Paraproteinemias present as
low anion gap values
lithium/bromide/iodide toxications present as
low or even negative anion gap values
Anion Gap formula
Na - (HCO3 + Cl-)
RTA or diarrhea present as
NAGMA
For every 1 g/dL drop in Albumin AG changes by
drops 2.5
If AG is calculated as 12 but serum albumin is 2 lower than normal what is the real AG
17
Serum osmolality calculation
2(Na) + (Glucose/18) + (BUN/2.8)
Osmolar Gap
Calculated osm - measured osm
normal osmolar gap
<10
if AG is 20
suspect alcohol ingestion
Delta - Delta Gap calculation
calculated AG(x) - normal AG(12) Delta HCO3 == normal HCO3 (24) - calculated delta gap
so
x-12 = y 24-y= delta gap
if measured HCO3 was close to 16 in delta detla
no additional acid base present
if measured HCO3 was >16 in delta delta
then additional metabolic alkalosis is present in addtion to HAGMA
if measured HCO3 <16 in delta detla
non-gap metabolic acidosis is present in addition to HAGMA
what is acidosis
pH <7.35
what is alkalosis
pH >7.44
normal HCO3
24
normal PCO2
40
normal anion gap
12
normal osmolar gap
10
HAGMA differential
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)
pyroglutamic acidosis
more in women who are malnourished or critically ill
seen through urinary organic acid screen
treated with halting of acetaminophen/IVF/N-acetylcysteine
DDx for increased osmolar gap
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
NAGMA DDx
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)
Proximal RTA (type 2)
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
Proximal RTA (type 2) etiology in kids
most common cause in kids is cystinosis
Proximal RTA (type 2) etiology in adults
most common cause in adults is falconi syndrome and secondary is multiple myeloma
clinical manifestation of proximal RTA (type 2)
NAGMA with or without proximal tubular dysfunction
hypokalemia which is milder than distal RTA (type 1)
diagnosis of proximal RTA (type 2)
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
Urine Anion Gap
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
if UAG is negative
indicated appropriate distal nephron urinary acidification
if UAG is positive
indicates inappropriate distal nephron urinary acidification
Distal RTA (Type 1)
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
Distal RTA (Type 1) etiology and manifestation
can be primary/acquired
commonly seen with Sjogren’s Syndrome
Glue sniffing another common cause due to toluene
associated with nephrolithiasis or nephrocalcinosis
Distal RTA (Type 1) diagnosis
NAGMA
unable to acidify urine pH <5.5
Hypokalemia from urinary K wasting
UAG is positive
Hyperkalemic RTA (Type 4)
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
Hyperkalemic RTA (Type 4) clinical manifestation and diagnosis
usually asymptomatic/NAGMA/hyperkalemia
patients are normally 50-70 with history of diabetes or CKD
diagnosis
urine pH>5.5
UAG positive
Metabolic Alkalosis DDx
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)
Respiratory Alkalosis DDx
anything that increases respiratory rate or Tidal Volume
there’s a big table
Respiratory Acidosis DDx
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)
Acid-Base Stepwise Approach
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