Block 4: Acid-Base Disorders

Question 1

What is the underlying cause of acid-base disorders?

Answer 1

Don’t just treat pH, you treat homeostatic imbalances

Question 2

What is purpose of respiration?

Answer 2

Provide O2 for ATP

Question 3

What is the equation for cellular respiration?

Answer 3

Glucose + 6 O2 → 6 CO2 + 6 H2O + 38 ATP (energy)

Question 4

What is the equation for bicarb buffer system?

Answer 4

Question 5

What are the variables that affect H+?

Answer 5

CO2: lungs
Bicarb: Kidneys

Question 6

What what are ABGs? Normal values?

Answer 6

pH
PaCO2
PaO2
HCO3

Question 7

What is the difference between alkalemia and academia?

Answer 7

Alkalosis → Alkalemia >7.45
Acidosis → Acidemia <7.35

Question 8

What is a primary disorder?

Answer 8

Process that causes a pH shift in the direction that the pH actually shifted

Question 9

What is compensatory response?

Answer 9

A change in either bicarb or CO2 that is in the opposite direction expected for the change in pH

Question 10

Describe the time it takes for respiratory vs metabolic compensation?

Answer 10

Respiratory: Minutes and max comp within 24 hrs
Metabolic: 3-5 days

Question 11

How are CO2 and HCO3 affected by acidosis?

Answer 11

↑ CO2
↓ HCO3-

Question 12

How are CO2 and HCO3 affected by alkalosis?

Answer 12

↑ HCO3-
↓ CO2

Question 13

In which direction would a simple respiratory acidosis move CO2?

Answer 13

UP

Question 14

If the disorder is respiratory acidosis in which direction would metabolic compensation (after 3-5 days) move the bicarb?

Answer 14

UP

Question 15

In which direction would a simple respiratory alkalosis move CO2?

Answer 15

Down

Question 16

In which direction would a simple metabolic acidosis move bicarb.?

Answer 16

Down

Question 17

If the disorder is metabolic acidosis in which direction would respiratory compensation move the CO2?

Answer 17

Down

Question 18

In which direction would metabolic compensation for a simple respiratory alkalosis move bicarb?

Answer 18

Down

Question 19

In which direction would respiratory compensation for a simple metabolic alkalosis move CO2?

Answer 19

Up

Question 20

Describe the compensation and primary disturbances of acid base disorders?

Answer 20

Question 21

How do you calculate an anion gap?

Answer 21

[Na+] – ([Cl-] + [HCO3-])

sum all negative charges = sum all positive charges

[Na+] + All unmeasured cations = [Cl-] + [HCO3-] + all unmeasured anions

Question 22

What is the normal anion gap?

Answer 22

11-12 mol/L

Question 23

What are the steps of acid-base disorder diagnosis?

Answer 23

1. Identify abnormalities in pH, PaCO2, and bicarbonate (ABG + electrolytes).
2. Which abnormalities are primary and which compensatory
3. Estimate the compensatory response.

Question 24

Describe the respiratory a-b disorder w or w/o composition? Labs?

Answer 24

Question 25

What is the general rule of a-b compensation?1

Answer 25

Compensation can not fully bring the back to normal state

Question 26

What are the rules of identifying primary abnormalities and which compensatory?

Answer 26

1. The process consistent with the pH shift is primary 2. Calculate anion gap: Gap > 20mmol/L - primary metabolic acidosis, regardless of pH or bicarb 3. Calculate excess anion gap (total – normal) add that to measured bicarb. If sum > normal bicarb there is underlying metabolic alkalosis. Sum < normal bicarb there is an underlying non-anion gap metabolic acidosis.

Question 27

What are the causes of metabolic acidosis and an ↑ in anion gap?

Answer 27

1. Lactic acidosis 2. Kidney disease 3. Methanol ingestion 4. Ethylene glycol ingestion 5. Salicylate overdose 6. Starvation

Question 28

What are the causes of metabolic acidosis and a normal anion gap?

Answer 28

1. GI bicarbonate loss 2. Drugs: cholestyramine, magnesium 3. Renal tubular acidosis

Question 29

What are the causes of metabolic alkalosis?

Answer 29

1. Volume depletion - vomiting, nasogastric suctioning 2. Diuretic use 3. Hypokalemia 4. Increased aldosterone 5. Increased mineralocorticoids

Question 30

What would an electrolyte fishbone panel look like?

Answer 30

Question 31

What are the causes of anion gap of metabolic acidosis?

Answer 31

Question 32

What is the gold mark?

Answer 32

G – Glycols (ethylene and propylene) O – Oxoproline L – L-lactate D – D-lactate M – Methanol A – Aspirin (salicylates) R – Renal failure K - Ketoacidosis

Question 33

What is acute acidosis caused by? Tx?

Answer 33

medications/ADRs, tissue hypoxia (lactic acidosis), DKA More severe/symptomatic Corect underlying Pathophysiology and consider dialysis or IV bicarb

Question 34

What are the causes of chronic acidosis? Treatment?

Answer 34

RTA or GI bicarb wasting Mild/asymptomatic but bone/growth disorders Tx: oral alkali replacement (Na vs K, Bicarb vs citrate)

Question 35

What are the complications of using just HCO3?

Answer 35

Administering exogenous HCO3 for chronic respiratory acidosis with relatively normal kidney function results in urinary excretion of the administered HCO3 without any further increase in serum HCO3 concentration

Question 36

What do the guidelines say about using HCO3 for acidosis?

Answer 36

Bicarbonate administration is **NOT ** recommended except for treatment of life-threatening hyperkalemia or for severe acidosis (pH<6.9) with evidence of compromised cardiac contractility

Question 37

How is HCO3 only recommended for cardiac arrest?

Answer 37

Related to hyperkalemia (to cause K shift) or overdose of tricyclic antidepressants

Question 38

What is the common cause of metabolic alkalosis?

Answer 38

Either Vomiting or Loop Diuretics + AKI 1. loss of H+ and Cl- 2. Injured kidneys cannot excrete enough HCO3- and Na+ to compensate 3. Vague S/Sx: patient history very important

Question 39

How do you treat metabolic alkalosis?

Answer 39

1. NaCl fluids (increased renal perfusion and replaces lost Cl-) 2. Acetazolamide (inhibits renal HCO3 absorption) - **first line** 3. HCl or HD (severe only)

Question 40

What are some of the cause of respiratory acidosis?

Answer 40

1. CNS depression – opiates, CNS event 2. Neuromuscular disorders – myopathies, neuropathies 3. Acute airway obstruction 4. Severe pneumonia 5. Pulmonary edema 6. Impaired lung motion – hemothorax, pneumothorax 7. Thoracic cage injury – flail chest 8. Ventilator dysfunction

Question 41

What are the common causes of respiratory alkalosis?

Answer 41

1. Progesterone 2. Theophylline 3. Nicotine 4. Hypoxia 5. Lung disease with or without hypoxia 6. CNS disease 7. Sepsis 8. Hepatic encephalopathy 9. Mechanical ventilation

Question 42

How do you use a mechanical ventilation for respiratory acid base disorders?

Answer 42

Give analgesics and sedatives, then you can control rate and depths of breaths to correct **But first you treat the underlying cause**