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Flashcards in ABG Deck (33):
1

venous blood gas

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

2

Hend. Hasselbach

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

3

questions

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

4

Normal CO2

35-45

5

to evaluate acid-base disturbance, need

simultaneous measurements of electrolytes, albumin, arterial blood gas

6

ABG directly measures

pH and Pco2

7

if the pH is acidic

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

8

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

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

9

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

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

10

it is physically impossible to have a...

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

11

measurement of cations/anions in plasma

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

12

anion gap =

Na – (HCO3 + Cl)
Normal Anion gap is from 12 +/- 4

13

major unmeasured cations

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

14

major unmeasured anions

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).

15

anion gap: misleading data from..

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

16

causes of increased anion gap: metabolic anion

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

17

causes of inc. anion gap: drug or chemical anion

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

18

causes of anion gap: metabolic acidosis (MUDPILES)

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

19

lactic acidosis

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.

20

DKA

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

21

DKA may dev. this during recovery phase

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

22

alcoholic ketoacidosis

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

23

decreased anion gap

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

24

normal anion gap acidosis

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

25

normal anion gap acidosis: loss of HCO3

Diarrhea
Ureteral diversion
Proximal colostomy
Ileostomy (pancreatic fluid loss

26

normal anion gap acidosis: renal loss of HCO3

Proximal Renal tubular acidosis
Carbonic anhydrase inhibitors

27

normal anion gap acidosis: renal tubular dysfunction

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

28

normal anion gap acidosis: hypoaldosteronism

Addison's disease
K+ sparing diuretic

29

strong ion difference, what if >30?

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

30

contraction alkalosis

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

31

causes of respiratory alkalosis

see slide- think of what makes you breathe rapidly

32

causes of respiratory acidosis

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

33

typical patterns seen in disease states

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)