Unit 3 Day 3 (Thur 4/23) Flashcards Preview

Cardiovascular > Unit 3 Day 3 (Thur 4/23) > Flashcards

Flashcards in Unit 3 Day 3 (Thur 4/23) Deck (18):
1

Define Henderson-Hasselbalch Equation for Bicarbonate/CO2

pH is defined as –log [H+] which gives:

-log [H+] = -log Ka- log [HA]/[A-]

or

pH = pKa + log[A-][HA]

2

Normal arterial blood gas values for pH, PaCO2, and [HCO3]

-pH: 7.4(little higher in Denver)
-PaCO2: 40mm Hg
-HCO3: 24 mEq/L

3

Four Major Acid-Base Disorders

-respiratory acidosis
-respiratory alkylosis
-metabolic acidosis
-metabolic alkalosis

4

Respiratory Acidosis Causes

-common cause:
--acute: CNS depressants (opiates, benzos, alcohol), respirator muscle fatigue (inc. work of breathing)
--chronic: central hypoventilation (obesity hypoventilation syndrome), neuromuscular disease (ALS), chronic lung diseases (emphysema, bronchiectasis), hypothyroidism

5

Respiratory Alkalosis Causes

-acute causes: pain, anxiety/panic attack, fever, mechanical ventilation
-chronic causes: living at altitude, brain injury, chronic salicylate toxicity, pregnancy

6

Metabolic Acidosis Causes

-anion gap: methanol, uremia, DKA, propylene glycol, INH, lactate, ethylene glycol, salicylates (mud piles)
-non-anion gap: GI losses (diarrhea), renal losses (RTA), too much IV saline (inc. Cl- with loss of bicarb)

7

Metabolic Alkalosis Causes

-vomiting or NG tube suction (loss of gastric acid)
-ingestion of NaHCO3
-ingestion of other alkali
-hypovolemia, so called contration alkalosis
-diuretics

8

Respiratory Acidosis Compensation

•acute change in PaCO2 of 10 Torr pH changes about 0.08 •PaCO2 of 1 Torr change in [HCO3–]of 0.4 meq/L in the same direction

9

Respiratory Alkalosis Compensation

•acute change in PaCO2 of 10 Torr pH changes about 0.08
•PaCO2of1Torrchangein [HCO3–]of 0.4 meq/L in the same direction

10

Metabolic Acidosis Compensation

Expected pCO2 = 1.5[HCO3-] + 8± 2

11

Respiratory Acidosis Acid-Base Disturbancs

-pH dec.
-pCO2 inc.
-HCO3- no change/small inc.

12

Metabolic Alkalosis Compensation

Increase [HCO3-] of 1mEq/L increases PaCO2 by 0.7 Torr

13

Respiratory Alkalosis Acid-Base Disturbances

-pH inc.
-pCO2 dec.
-HCO3- no change/small dec.

14

Metabolic Acidosis Acid-Base Disturbances

-pH dec.
-pCO2 dec.
-HCO3- dec.

15

Metabolic Alkalosis Acid-Base Disturbances

-pH inc.
-pCO2 inc.
-HCO3 inc.

16

Anion Gap

anion gap = [Na] - ([Cl] +[HCO3-])
-normally 12-14
-the difference in the measured cations and the measured anions in serum, plasma, or urine.

17

Winter's Formula

expected pCO2 = 1.5 [HCO3-] + 8 +/- 2
-compare to given PCO2
-compensation rule
-if within range, it is compensated/probably chronic

18

A-a Gradient

PAO2 = (630-47) x FiO2 - (PCO2/0.8) - PaO2
-useful in determining the source of hypoxemia
-isolates the location of the problem as either intrapulmonary or extrapulmonary
-normal is between 5 - 20
-an inc. A–a gradient suggests a defect in diffusion, V/Q mismatch, or right-to-left shunt.