Acid/Base

Question 1

Acidosis

Answer 1

Metabolic: decrease HCO3 or =45 mmHg

Question 2

Alkalosis

Answer 2

Metabolic: increase HCO3 > or = 28 mEq/L
Respiratory: decrease pCO2

Question 3

Lungs

Answer 3

• regulate ACUTE changes (occurs w/in seconds)

- regulates PCO2 through respiration rate and depth changes

Question 4

Renal

Answer 4

• regulates CHRONIC changes (takes hours- days to compensate)
• regulates HCO3 and H through excretion/reabsorption/buffer

Question 5

Primary METABOLIC disorder–> Respiratory compensation

Answer 5

meta acidosis –> compensate w/respiratory alkalosis

meta alkalosis–> compensate w/respiratory acidosis

Question 6

Primary RESPIRATORY disorder–> Metabolic compensation

Answer 6

resp acidosis–> compensate w/metabolic alkalosis

resp alkalosis–> compensate w/metabolic acidosis

Question 7

Acidosis Clinical Manifestation

Answer 7

• hyperventilation
• CNS depression
• Hypotension
• Hyperkalemia
• Arrhythmias
• decrease contractility

Question 8

Alkalosis Clinical Manifestation

Answer 8

• nerve excitation
• Arrhythmias
• respiratory depression
• hypoventilation
• hypokalemia

Question 9

Step 1.

Answer 9

evaluate the pH

• pH acidemia
• pH > 7.40–> alkalemia

Question 10

Step 2.

Answer 10

Is the primary disorder respiratory or metabolic?

–> it is problem with the HCO3 or the PCO2?

Question 11

Step 3.

Answer 11

Calculate the anion gap.

AG= Na- Cl- HCO3

Question 12

Step 4.

Answer 12

Check for compensation

• winter’s formula for METABOLIC acidosis
• -> pCO2= 1.5 (HCO3)+8 (+-2)
• expected increase in pCO2 w/METABOLIC alkalosis
• -> pCO2= 0.75 (pt’s HCP3- norm HCO3) (-+2)

Question 13

Step 5.

Answer 13

If AGMA, check corrected HCO3

• -> corrected HCO3= pt’s HCO3 + (pt’s AG- norm AG)
• **norm AG= 12

Question 14

Corrected HCO3

Answer 14

• relationship between the serum HCO3 & AG
• Indicates if degree of compensation is appropriate or if another metabolic acid/base disorder is present
• for rise in AG by 1–> corresponding decrease of HCO by 1 mEq/L
• if calculated HCO3 is not in the reference range (22-28 mEq/L)–> coexisting metabolic disturbance
• —> if > norm, metabolic alkalosis
• —> if

Question 15

Causes of NAGMA

Answer 15

H: Hyperalimentation (high Cl soln) TPN & NS
A: Acetazolamide (inhibit Na reabsorption)
R: Renal tubular acidosis (proximal, distal, & hyperaldosteronism type 4)
D: Diarrhea
U: Uretero-pelvic shunt (fistula)- excessive loss of HCO3 from surgery or cancer
P: Post-hypocapnia (decreased CO2)
S: Spironolactone

Question 16

Causes of AGMA

Answer 16

M: Methanol/Metformin
U: Uremia (high BUN)--> CKD or AKI
D: Diabetic acidosis (DKA), ketoacidosis
P: Poisoning/ propylene glycol/ paraldehyde 
I: Intoxication/ infection/ isoniazid (INH)
L: Lactic acidosis (shock)
E: Ethylene glycol (antifreeze)
S: Salicylates/Sepsis

Question 17

Winter’s Formula

Answer 17

expected pCO2= 1.5 (HCO3) +8 (+-2)

- pCO2 predicted: coexisting respiratory acidosis

Question 18

Osmolar Gap

Answer 18

• if you can’t easily identify a cause for an AGMA, calculated the osmolar gap.
• osmolar gap= measured Osm- calculated Osm
• calculated Osm= 2(Na) + BUN/2.8 + glucose/18 + EtOH/4.6
• -> norm gap Osm gap > 10

Question 19

Typical Treatment for Metabolic acidosis

Answer 19

• if pH is 7.20-7.35: focus on cause

- if pH

Question 20

Treatment Options for Metabolic acidosis- Sodium Bicarbonate

Answer 20

***Goal: target pH 7.2
tab: 3.9 mEq/ 325 mg, chronic replacement in renal failure or renal tubular acidosis
IV: 50 mEq or mmol ampule; isotonic soln in D5W or SW 150 mEq NaHCO3/ 1 L, reserve for acute situations no evidence-based benefit

Question 21

Treatment Options for Metabolic acidosis- Sodium citrate/ citric acid

Answer 21

Alkali: 1 mEq/ mL soln

- chronic replacement in renal failure or renal tubular acidosis

Question 22

Treatment Options for Metabolic acidosis- Tromethamine (THAM)

Answer 22

Alkali: sodium-free buffer

• reserve for acute situations
• no benefit over sodium bicarbonate

Question 23

Treatment Options for Metabolic acidosis- Hemodialysis

Answer 23

A:
E:
I:
O:
U: 
- reserved for acute situations

Question 24

Metabolic Alkalosis Causes

Answer 24

C: contraction
L: Licorice
E: Endocrine (Conn's, Cushing's, Bartter's syn)
V: vomiting
E: excess alkali (Sodium bicarb)
R: refeeding alkalosis (malnurished pt's)
P: post-hypercapnia
D: diuretics

Question 25

Compensation for metabolic alkalosis

Answer 25

exp increase in pCO2= 0.75 (pt's HCO3- norm HCO3 {12}) | - if pCO2 predicted: respiratory acidosis

Question 26

Treatment for metabolic alkalosis: volume-dependent or saline-responsive

Answer 26

1. vomiting 2. nasogastric suction 3. diuretics Urine Chloride:

Question 27

Treatment for metabolic alkalosis: volume-independent or saline-resistant

Answer 27

1. mineralcorticoid excess --> Cushing's syn --> Conn's syn 2. hypokalemia Urine Chloride: > 20 mEq/L Treat: - treat underlying disorder - potassium replacement

Question 28

Respiratory Acidosis causes

Answer 28

C: CNS depression (stroke, opiate OD, seizures, sedation, head trauma) A: Airway obstruction (COPD) N: Neuromuscular disorders (ALS, Guillain Barre, Myasthenia gravis) S: Severe pneumonia, pulmonary embolism, pulmonary edema

Question 29

Compensation for Respiratory Acidosis

Answer 29

- for each 10 mmHg increase in pCO2, pH will decrease by: - -> 0.08 units in ACUTE respiratory acidosis - -> 0.03 units in CHRONIC respiratory acidosis

Question 30

Treatment for Respiratory Acidosis

Answer 30

- Focus on cause - Oxygen therapy * ***NEVER use added base for respiratory acidosis

Question 31

Respiratory Alkalosis cause

Answer 31

C: CNS stimulation (pain, anxiety, fever, tumors, stroke, head trauma) H: hypoxia A: anxiety M: mechanical ventilation P: progesterone (pregnancy & cirrhosis) S: salicylates/sepsis

Question 32

Compensation for Respiratory Alkalosis

Answer 32

- for each 10 mmHg decrease in pCO2, pH will increase by - -> 0.08 units in ACUTE respiratory alkalosis - -> 0.03 units in CHRONIC respiratory alkalosis

Question 33

Treatment for Respiratory Alkalosis

Answer 33

- focus on cause - hypoventilation - breathe into a bag for anxiety - sedation

Question 34

General Treatment Principles

Answer 34

- ALWAYS correct underlying etiology - ->DKA: stop ketoacid production, correct volume depletion, and normalize blood glucose - ->Uremia: renal replacement therapy (dialysis) - -> excessive vomiting: antiemetics - -> COPD exacerbation: oxygen, bronchodilators, corticosteroids, possibly antibiotics - -> narcotic OD: opiod antagonist - Alkali or acid replacement - -> reserved for critically-ill pt's - -> only provides a "temporary fix"