Acid/Base disorders

Question 1

What are ABG’s used for

Answer 1

monitoring oxygenation, ventilation, acid base balance

quantifying level of carboxyhemoglobin and methhemoglobin

Question 2

How do you draw an ABG

Answer 2

from artery (MC radial)
mix with anticoag (heparin)
put on ice
take to the lab ASAP, results w/in 5-15 min

Question 3

What are the ABG’s

Answer 3

pH 7.35-7.45 
pO2: 80-100
O2 sat: >95
pCO2: 35-45 
HCO3: 22-26

Question 4

pO2 is used to determine

Answer 4

how well a patient is oxygenated (better than an O2 sat), NOT for determining acid-base conditions

Question 5

What is our body’s normal physiology

Answer 5

body maintains homeostasis with strict control of hydrogen ions
buffer systems keep pH in normal range
acidosis/alkalosis are disorders
acidemia and alkalemia are pH of blood

Question 6

What are respiratory and metabolic problems

Answer 6

Resp acidosis: pCO2 >45
Resp alkalosis: pCO2 <35
Met acidosis: HCO3 <22
Met alkalosis: HCO3 >26

Question 7

Acid base disorders indicate

Answer 7

underlying disease process- so Tx underlying disease!
You can have up to 3 AB d/o- we have to figure out the primary one and treat it
(but you can only have ONE respiratory AB d/o)

Question 8

What is the compensatory process

Answer 8

body will compensate for an AB d/o with the opposite
Respiratory compensation for metabolic d/o= fast
metabolic compensation for resp d/o= days-weeks

Question 9

What causes metabolic acidosis

Answer 9

high anion gap: MUDPILES (methanol, uremia, DKA, propylene glycol, iron, lactate, ethanol, salicylate/starvation)
non-high anion gap: diarrhea (you lose more bicarb), RTA, Acetazolamide, spironalactone, Hyperchloremia

Question 10

How do you treat metabolic acidosis

Answer 10

Sodium bicarb (band aid)
allow for respiratory compensation (hyperventilation, low CO2)
treat underlying cause

Question 11

What is renal tubular acidosis

Answer 11

defects in H+ secretion and urinary acidification

Metabolic acidosis + NORMAL anion gap

Question 12

What are the 2 types of renal tubular acidosis

Answer 12

Type 1: failure to excrete H+

Type 2: failure to reabsorb filtered HCO3

Question 13

Explain Type 1 RTA (distal)

Answer 13

AI disease and hypercalciuria (or genetic) cause H+ to not be excreted
Tx: correct metabolic acidosis (sodium bicarb), give potassium citrate if persistent hypokalemia

Question 14

Explain Type 2 RTA (proximal)

Answer 14

Defect in proximal bicarb reabsorption, or other defects in proximal tubule that inhibit reabsorption of phosphate, glucose, uric acid, and amino acids
-Fanconi syndrome: generalized proximal tubular dysfunction caused by multiple myeloma or acetazolamide

Question 15

How do you treat Type 2 RTA

Answer 15

correct academia
Vitamin D and phosphate
+/- thiazide

Question 16

With metabolic Alkalosis, what do you need to check

Answer 16

Urine chloride

Question 17

If Metabolic alkalosis + Urine chloride <25 (responsive to alkalosis) it is caused by

Answer 17

Vomiting (you lose more acid)
Diuretics (contraction alkalosis)
CF
**Tx with FLUIDS!

Question 18

If Metabolic alkalosis + urine chloride >25 (not responsive to alkslosis) it is caused by

Answer 18

Cushing’s, high aldosterone, low potassium, citrate toxicity
chronic diuretics
renin secreting tumor
*Tx underlying cause, +/- potassium

Question 19

What happens in respiratory acidosis

Answer 19

you cant ventilate well (hypoventilation) so you build up CO2 (>45)

Question 20

What are causes of respiratory acidosis

Answer 20

Acute airway obstruction (FB, laryngospasm)
Lung Dz: PNA, PE, COPD, PE
CNS depression: narcotics, trauma, OSA
NM d/o: Guillan barre, MG, brain stem/S.C. injury

Question 21

How do you treat respiratory acidosis

Answer 21

Tx underlying cause
BiPAP (resp support) if acute
chronic is more stable an dmay not need Tx

Question 22

What are Sx of respiratory alkalosis

Answer 22

(hyperventilation, pCO2 <35)

Light headed, palpitations, tachypnea, paresthesias

Question 23

What can cause respiratory alkalosis

Answer 23

Hyperventilaiton (anxiety) 
sepsis compensation 
pain
salicylate OD (mudpiles!) 
pregnancy
high altitude
hypoxemia 
hepatic encephalopathy

Question 24

How do you treat respiratory alkalosis

Answer 24

treat underlying cause

Question 25

What is compensation

Answer 25

if pH is close to normal, pt is compensating | if highly abnormal pH, patient is not compensating

Question 26

What is an anion gap

Answer 26

anions that cant be measured on BMP- albumin, phosphate, sulfate, etc Na- (Cl+HCO3)= 8-12 mmOl normally

Question 27

What does anion gap >20 mean

Answer 27

primary metabolic acidosis (regardless of what other ABG's say!) body doesn't generate large anion gaps as compensation, so there must be an underlying metabolic acidosis

Question 28

Explain mixed acid base disorders

Answer 28

you can have up to 3 at a time, but only 1 respiratory d/o at a time

Question 29

Take home points

Answer 29

``` normal pH does NOT mean no acid base disorder low bicarb (metabolic acidosis) is usually pathologic- investigate it ```

Question 30

What does MUDPILES stand for

Answer 30

``` Methanol Uremia DKA Propylene glycol Iron Lactate Ethanol Salicylate OD/starvation ``` They all cause high anion gap metabolic acidosis!