Acid-Base Disorders Flashcards
What is the normal range for arterial pH?
Intracellular pH is maintained in what range?
- 35-7.45
- 0-7.3
Many extracellular and intracellular buffer systems maintain the body’s pH. What is the most important buffer system?
Bicarbonate buffer system
As HCO3 increases, pH does what?
As PCO2 increases, pH does what?
pH increases
pH decreases
Where is carbonic anhydrase found?
present in the lung alveoli and renal tubular epithelial cells
Lungs regulate pH by controlling the concentration of what?
Increase RR causes CO2 to (increase or decrease)?
Decrease RR causes CO2 to (increases or decrease)?
PCO2
increase in RR=increases in CO2 blown off
decrease in RR=decreases in CO2 blown off
The kidneys regulate pH by excreting what?
either an acidic or alkaline urine
A low serum HCO3 indicates what disturbance?
A high serum HCO3 indicates what disturbance?
Metabolic Acidosis
Metabolic alkalosis
A high PCO2 indicates what disturbance?
A low PCO2 indicates what disturbance?
Respiratory disturbances can be qualified how?
Respiratory Acidosis
Respiratory Alkalosis
Either acute or chronic
What are the two flavors or metabolic acidosis?
high anion gap metabolic acidosis
normal anion gap metabolic acidosis
What are the two flavors of metabolic alkalosis?
Saline-responsive (hypovolemia or contraction alkalosis)
Saline-Non-Responsive (euvolemia or hypervolemia)
If the kidney caused acidosis/alkalosis, what organ compensates?
If the lung caused acidosis/alkalosis, what organ compensates?
The lung!
The kidney!
Metabolic acidosis with a decrease in HCO3 will be compensated with what disturbance?
Compensated with respiratory alkalosis
(decreased PCO2, increased RR)
Metabolic alkalosis (increased HCO3) will be compensated with what disturbance?
Compensated by respiratory acidosis
(increased PCO2 and decreased RR)
Respiratory acidosis (increased PCO2) will be compensated by what disturbance?
Compensated by metabolic alkalosis
(increased HCO3)
Respiratory alkalosis (decreased PCO2) will be compensated by which disturbance?
compensated by metabolic acidosis
(decreased HCO3)
For every 10mmHg increase in pCO2, HCO3 should increase by ___ in acute and ___ in chronic respiratory acidosis
acute: 1
chronic: 3.5
For every 10mmHg decrease in PCO2, HCO3 should decrease by ___ in acute and ___ in chronic respiratory alkalosis
acute: 2
chronic: 5
how many acid-base disturbances can be present at once?
three
What are the four steps of determining an acid-base disturbance?
- determine if it is acidosis or alkalosis
- determine if the primary disturbance is metabolic or respiratory
- if metabolic acidosis, calculate anion gap
- calculate appropriate compensation for primary acid base disorder
If metabolic acidosis is present, what three things should be considered?
- if hypoalbunemia present, calculate corrected anion gap
- if HAGMA present, calculate osmolar gap
- if HAGMA present, consider delta-delta gap calculation
If the primary acid-base disorder is compensated appropriately, is there a simple or mixed AB disorder?
Simple acid-base disorder
If the primary acid-base disorder is not compensated, is there a simple or mixed AB disorder?
Mixed acid-base disorder
What is the normal range for pH?
7.35-7.44
What is the normal HCO3?
24
What is the normal PCO2?
40
What is the normal anion gap?
12
What is the normal osmolality gap?
10
What is the formula for anion gap?
What is anion gap used to determine?
Na-(HCO+Cl)
Normal AG is 12+/-2
HAGMA vs. NAGMA
If HAGMA is present, calculate the osmolality using the following formula:
Find the olsmolar gap how?
2(Na) + (Glucose/18) + (BUN/2.8)
normal: 275-290
gap= measured serum osmolality-calculated serum osmolality
normal: <10
If anion gap is >20, what is this highly suspicious for?
Alcohol ingestion
(likely seen with HAGMA)
What is delta-delta gap used for?
Used in patients with HAGMA to determine if there is a coexisiting NAGMA or metabolic alkalosis present
What are the GOLDMARK causes of HAGMA?
Glycols
Oxyproline
L-Lactic acidosis
D-Lactic acidosis
Methanol
Aspirin
Renal failure
Ketoacidosis
Which cause of acidosis is commonly seen in women who are malnourished or critically ill?
Diagnosed how?
Treated how?
Pyroglutamic (5-oxoproline) acidosis
Diagnosed via urinary organic acid screen
Stop Tylenol; Give IVF and NAC
What are the causes of increased osmolar gap?
Methanol
Ethanol
Dietheylene Glycol
Isopropyl Alcohol
Ethylene glycol
Propylene glycol
Ketoacidosis/lactic acidosis
Methanol metabolizes to formic acid which can cause which aberration?
Ethylene glycol metabolizes to oxalic acid which can cause which aberration?
blindness
Renal failure
What are the DURHAAM causes of NAGMA?
Diarrhea
ureteral diversion or fistula
renal tubular acidosis
hyperalimentation
acetazolamide
addison’s disease
Misc.
When net acid excretion by the kidneys is impaired resulting in a NAGMA without any s/s of AKI, what is the likely diagnosis?
Renal Tubular Acidosis
What is RTA 1?
results from decreased net H ion secretion in distal tubules and CD
What is RTA 2?
results from decreased HCO3 reabsorption in the proximal tubules
What is RTA 4?
results from decreased aldosterone secretion or aldosterone resistance
IF RTA is suspected and hypokalemia is present with proximal tubular dysfunction (AA, glucose, bicarb in urine) what is the diagnosis?
Type 2 RTA
urine anion gap will be negative
If RTA is suspected and hypokalemia is present without proximal tubular dysfunction, what is the diagnosis?
Type 1 RTA
urine anion gap will be positive
If RTA is suspected and hyperkalemia is present, what is the diagnosis?
Type 4 RTA
urine anion gap will be +
most common type, often seen with DM2 or CKD
What is the urine anion gap used for?
How is it calculated?
used to differentiate renal from non-renal causes of NAGMA
NH4Cl excretion indicates urinary acidifcation and is UAG is a surrogate marker of NH4 excretion via NH4Cl
UAG=(urineNa + UrineK) - UrineCl
if negative-appropriate urinary acidification
if positive-inappropriate urinary acidification
Along the nephron, as H ions are secreted, what is reabsorbed at a 1:1 ratio?
HCO3
What is the etiology for RTA 2?
common cause in children is cystinosis
common cause in adults is Fanconi Syndrome caused by Multiple Myeloma
What are the clinical manifestations of RTA type 2?
NAGMA with or without proximal tubular dysfunction
Hypokalemia (mild compared to type 1)
how is RTA type 2 diagnosed?
Urine pH can be high or low, but will be <5.5 in steady state
UAG will be negative
unlike proximal RTA, distal RTA (type 1) patients are ____ to acidify their urine?
Type 1 RTA patients are unable to acidify their urine
What is the etiology for type 1 RTA?
Sjögren’s Syndrome
Glue Sniffing
What are two clinical manifesations associated with RTA type 1?
Nephrolithiasis
Neprhocalcinosis
What are the four diagnostic characteristics of RTA type 1?
NAGMA
Unable to acidify urine to <5.5
Hypokalemia
UAG is positive
What are two main causes of RTA type 4?
Both lead to what?
deficiency of circulating adolsterone (DM, drugs)
Aldosterone resistance in CD (instl disease, drugs)
Lead to impaired Na reabsorption leading to Hyperkalemia
What are the clinical manifestations of RTA type 4?
NAGMA
Hyperkalemia
often older pts with hx of DM or CKD
Diagnosis of RTA type 4 includes what?
variable urine pH, usually >5.5
UAG is positive
Acidosis is associated with (hypo or hyperkalemia?)
Alkalosis is associated with (hypo or hyperkalemia?)
hyperkalemia
hypokalemia
Factors that stimulate Na reabsorption secondarily increase H secretion thus stimulating ___ reabsorption leading to a potential ____
HCO3; metabolic alkalosis
What are five main causes of metabolic alkalosis?
Hypokalemia
Vomiting/NG tube
Diuretics
Volume depletion (contraction alkalosis)
Mineralcorticoid excess
What are the clinical manifesttions of Bartter syndrome?
What does this lead to?
What type of diuretic does this mimic?
hypokalemia
metabolic alkalosis
low-norm BP
hypercalciuria, nephrocalcinosis
leads to NaCl loss, volume depletion and 2’ hyperaldosteronism
mimics loop diuretics
What are the clinical manifestations of Gitelman Syndrome?
What diuretic does this mimic?
hypokalemia
metabolic alkalosis
low to norm BP
hypocalciruia
hypomagnesemia (TRPM6 channel downregulation)
mimics thiazide diuretic
What is the clinical manifestation of Liddle Syndrome?
Autosomal dominant
resistant to hypertension
hypokalemia
metabolic alkalosis
How is the diagnosis of Liddle syndrome made?
how is it treated?
Genetic testing
low aldosterone and renin levels
treat with amiloride or triamterene and low Na diet
Anything that increases respiratory rate or TV causes what aberration?
Respiratory alkalosis
(esp. Pregnancy)
anything that lowers respiratory rate/TV, increases dead space, or worsens airway obstruction causes what aberration?
Respiratory acidosis
Inadequate ventilator settings and increased CO2 production can cause what aberration?
Respiratory Acidosis
