Acid-Base

Question 1

urinary buffers

Answer 1

Phosphate (HPO4 = H → H2PO4)
Urate
Creatinine
Ammonia (NH3 + H → NH4)
Major adaptive response is an increase in ammonium excretion in the urine

Question 2

Causes of Respiratory AcidosispH < 7.35 with a PaCO2 > than 45 mm Hg

Answer 2

Central nervous system depression: medications (narcotics, sedatives, or anesthesia), head injury
Impaired respiratory muscle function: spinal cord injury,neuromuscular diseases
neuromuscular blocking drugs
Pulmonary disorders: Atelectasis, Pneumonia, Pneumothorax, Pulmonary edema, Bronchial obstruction, Massive pulmonary embolus, Respiratory failure
Hypoventilation due to:
Pain, Chest wall injury/deformity, Abdominal distension, Obesity, Trauma

Question 3

tabolic Acidosisbicarbonate level of < 22 mEq/L with a pH < 7.35

Answer 3

Renal failure
Diabetic ketoacidosis
Diarrhea**
Anaerobic metabolism
from tissue hypoxia
Starvation
Salicylate intoxication

Question 4

Increased anion gap metabolic acidosis : MUDPILES

Answer 4

M – methanol intoxication
U - uremia
D – diabetic or alcoholic ketoacidosis
P – paraldehyde
I – Isoniazide or iron overdose
L – lactic acid
E – ethylene glycol intoxication
S – salicylate overdose

Question 5

Non-anion gap metabolic acidosis: USED CAR

Answer 5

U - Ureteral- sigmoid diversions (accumulate urine in intestine, reabsorb Cl; H20 in intestine, secrete bicarb in intestine)
S – small bowel fistula, saline administration
E – Endocrinopathies (Addison’s, Hyperparathyroidsim)
D – Diarrhea
C – carbonic anhydrase inhibitors
A - (hyper)alimentation (TPA)
R - Renal tubular acidosis

Question 6

Metabolic Alkalosisbicarbonate level > 26 mEq/L with a pH > 7.45

Answer 6

Excess base occurs from ingestion of:
antacids, excess use of bicarbonate, use of lactate in dialysis
Loss of acids can occur secondary to:
protracted vomiting, gastric suction, Hypochloremia, Excess administration of diuretics, High levels of aldosterone

Question 7

Symptoms of Alkalosis

Answer 7

Paresthesias of the fingers and toes
Tetany
Seizures
Pt may become belligerent
CNS depression

Question 8

Treatment of Metabolic Alkalosis

Answer 8

1. Chloride-responsive:
   Replace volume with NaCl if depleted
   Correct hypokalemia if present
   NH4Cl and HCl should be reserved for extreme cases
2. Chloride-resistant:
   Treat underlying problem, such as stopping exogenous glucocorticoids

Question 9

High serum anion gap

Answer 9

Most often due to an increase in unmeasured anions, and this is almost always caused by one of the organic metabolic acidoses (eg, lactic acidosis, ketoacidosis)

Question 10

Delta Gap

Answer 10

Ratio of the increase in anion gap compared to the decrease in the HCO3 concentration
AG measured - 12 = delta AG (∆AG)
24 – measured HCO3 = delta bicarb(∆BC)
If ∆AG is > ∆BC then 
metabolic alkalosis present
If ∆AG is < ∆BC then NON-AG
metabolic acidosis
If they are equal (=/- 2) then NO ADDITIONAL DISTURBANCE

Question 11

Winter’s formula

Answer 11

Used in metabolic acidosis to predict the PaCO2 you should have if there is appropriate respiratory compensation for the metabolic acidosis

Predicted PaCO2 =1.5 * (HCO3-) + 8 (+/- 2)
Rough estimate is HCO3 + 15
Or PCO2 should be similar to the decimal digits of the pH. (pH 7.25, the PCO2 should be about 25)

Question 12

Winter’s formula interpretation

Answer 12

Higher than predicted = concomitant respiratory acidosis

Lower than predicted = concomitant respiratory alkalosis

Question 13

Summer’s formula

Answer 13

Used to calculate respiratory compensation (CO2) for metabolic alkalosis
CO2 higher than actual = concomitant respiratory alkalosis
CO2 lower than actual = concomitant respiratory acidosis

PCO2=0.7 ( HCO3+21) +/-2