ABG

Question 1

venous blood gas

Answer 1

Differences in pH and PCO2 are relatively small
In general the pH is 0.03-0.04 units lower than arterial
In general the PCO2 is 7 or 8mmHg higher than artery
-less accurate and less preferred than arterial

Question 2

Hend. Hasselbach

Answer 2

pH= 6.1 + log (HCO3/0.03*PCO2)

Question 3

questions

Answer 3

Acidic or Basic? 7.35-7.45 Who’s to blame? look at CO2

Is that all?

Question 4

Normal CO2

Answer 4

35-45

Question 5

to evaluate acid-base disturbance, need

Answer 5

simultaneous measurements of electrolytes, albumin, arterial blood gas

Question 6

ABG directly measures

Answer 6

pH and Pco2

Question 7

if the pH is acidic

Answer 7

And the CO2 is elevated (acidic)—blame the lungs (respiratory)
But if the CO2 is decreased (basic)—blame the body (metabolic)

Question 8

The body can have a basic single acid base disturbance…or…

Answer 8

the more frequent double acid base disturbance, or the complex triple acid base disturbance

Question 9

for ever multiple of 10 the co2 is elevated or decreased (from normal: 40) the pH should change by..

Answer 9

0.08 times (from 7.40) that multiple
Example: pH of 7.24 with a CO2 of 60
*single A-B disturbance

Question 10

it is physically impossible to have a…

Answer 10

respiratory acidosis w/ resp. alkalosis but CAN have an anion gap metab. acidosis w/ metab. alkalosis

Question 11

measurement of cations/anions in plasma

Answer 11

[Na] + Unmeasured cations = HCO3 + Cl + Unmeasured anions

Question 12

anion gap =

Answer 12

Na – (HCO3 + Cl)

Normal Anion gap is from 12 +/- 4

Question 13

major unmeasured cations

Answer 13

Ca (2 mEq/L), Mg (2 mEq/L), gamma-globulins, and K (4 mEq/L)

Question 14

major unmeasured anions

Answer 14

albumin (2 mEq/L per g/dL), PO4 (2 mEq/L), sulfate (1 mEq/L), lactate (1–2 mEq/L), and other organic anions (3–4 mEq/L).

Question 15

anion gap: misleading data from..

Answer 15

hypoalbuminemia (for every 1g change in albumin, the AG should have a 2meq change (inc. if albumin low, dec. if high)
hyper or hyponatremia
certain antibiotics

Question 16

causes of increased anion gap: metabolic anion

Answer 16

Diabetic, alcoholic, starvation ketoacidosis
lactic acidosis (Type A (tissue ischemia), Type B (altered cell metabolism), D-Lactic acidosis)
CKD
5-oxoproline acidosis from acetaminophen toxicity

Question 17

causes of inc. anion gap: drug or chemical anion

Answer 17

Salicylate intoxication
Sodium carbenicillin therapy
Methanol (formic acid)
Ethylene glycol (oxalic acid)
Cyanide
Isoniazid
Propofol
Propylene glycol
Valproic acid
Paraldehyde

Question 18

causes of anion gap: metabolic acidosis (MUDPILES)

Answer 18

Methanol
Uremia
DKA (and etOH, starvation ketoacidosis)
Paracetamol (acetaminophen) (Paraldehyde)
Iron, Isoniazide, Inborn errors of metabolism
Lactic acidosis
Ethanol, Ethylene Glycol
Salicylate/ASA

Question 19

lactic acidosis

Answer 19

from pyruvate in anaerobic glycolysis, normal 1mEq
-Metab of lactate mostly: liver gluconeogenesis (30% by kidneys)
Type A (hypoxic): dec. perfusion (shock, CO poisoning)
Type B (metab/toxins): DM, KD, leukemia, lymphoma, salicylates, metformin, INH, propofol, etc.

Question 20

DKA

Answer 20

acetoacetate/B-hydroxybutyrate cause INC. metab. gap, also have comb. lactic acidosis from tissue HYPOperfusion and inc. anaerobic metab.

Question 21

DKA may dev. this during recovery phase

Answer 21

hyperchloremic non-anion gap metab. acidosis from saline resuscitation
*important to monitor anion gap–>when to turn off insulin drip (guides tx)

Question 22

alcoholic ketoacidosis

Answer 22

lots of variation:

• primarily: Beta hydroxybutyrate and acetoacetate excess
• Lactic acidosis since alcohol increases production of lactate especially when accompanied by thiamine deficiency (if v. high >6 consider pancreatitis, sepsis, post-seizure (concomitant)
• metab. alkalosis from vomiting and vol. contraction
• resp. alkalosis from w/drawal and pain

Question 23

decreased anion gap

Answer 23

Hypoalbuminemia (decreased unmeasured anion)
Plasma cell dyscrasias
Monoclonal protein (cationic paraprotein) (accompanied by chloride and bicarbonate)
Bromide intoxication

Question 24

normal anion gap acidosis

Answer 24

loss of HCO3
renal loss of HCO2
renal tubular dysfunction
hypoaldosteronism
Chloride retention
admin. of HCl equiv or NH4Cl
argining and lysine in parenteral nutrition

Question 25

normal anion gap acidosis: loss of HCO3

Answer 25

Diarrhea
Ureteral diversion
Proximal colostomy
Ileostomy (pancreatic fluid loss

Question 26

normal anion gap acidosis: renal loss of HCO3

Answer 26

Proximal Renal tubular acidosis

Carbonic anhydrase inhibitors

Question 27

normal anion gap acidosis: renal tubular dysfunction

Answer 27

ATN
Chronic tubulointerstitial disease
Distal RTA type 1
Distal RTA type 4

Question 28

normal anion gap acidosis: hypoaldosteronism

Answer 28

Addison’s disease

K+ sparing diuretic

Question 29

strong ion difference, what if >30?

Answer 29

[SID] = [Na+] + [K+] + [Ca2+] + [MG2+] - [CL-] - [Other Strong Anions]
*Na and Cl are biggest contributors (calculate: Na-Cl)
if >30: metabolic alkalosis

Question 30

contraction alkalosis

Answer 30

decreasing volume increases SID (inc. Na+ relative to Cl-)

Question 31

causes of respiratory alkalosis

Answer 31

see slide- think of what makes you breathe rapidly

Question 32

causes of respiratory acidosis

Answer 32

see slide- consider airway obstruction, laryngospasm, mucus plug, anesthesia, resp. depression (meds), high carb diet, sedatives

Question 33

typical patterns seen in disease states

Answer 33

Combined Metabolic Acidosis and Respiratory Acidosis (Cardiogenic Shock- not breathing as much and hyper perfusion)
Combined Metabolic Acidosis and Respiratory Alkalosis (Sepsis, Salicylate poisoning)
Respiratory Acidosis with metabolic alkalosis (Chronic COPD-body compensating for resp. acidosis w/ the metab. alk)