Acid-Base Flashcards
The kidney is able to stabilize acid base by ?
altering either acid elimination (H+ excretion) or base elimination (HC03 excretion).
The lung eliminates massive amounts of acid as (1), but if there is pulmonary disease, then the kidney excretes (2)
- C02
2. H+ thereby raising the blood pH.
In times of base excess, there is more (1) filtered, so the kidney eliminates more (1), thereby (2)
- bicarbonate (HC03)
2. lowering the blood pH.
Cells use the ability of carbonic anhydrase to catalyze the formation of C02 from (1) to achieve charge neutrality and add either (2) to the blood or the urine as needed.
- hydrogen and bicarbonate
2. H+ or HC03
Buffers such as (3) allow neutralization of pH without massive excretion of charged ions
- phosphate and ammonia
The simplest way to solve acid base problems is by first determining if there is an acidosis or alkalosis by evaluating the pH. If the pH is below the normal range (1), then there is (2), whereas if it is above the normal range, there is (3)
- 7.35-7.45
- acidosis
- alkalosis.
Next, evaluate whether the respiratory or metabolic component can explain the observed pH change. If an acidosis, then (1)
- elevated pC02 or a reduced HC03
Next, evaluate whether the respiratory or metabolic component can explain the observed pH change. If an alkalosis then (1)
- reduced pC02 or an elevated HC03
For example: If the pH is 7.2 and the pC02 is above the normal range (35-45 mm Hg), then the patient has (1). We may also expect to find (2) in such a patient, but that is the (3)
- respiratory acidosis
- an elevated HC03
- compensatory metabolic alkalosis.
In some patients with a metabolic acidosis, there are (1) present (2) which can be calculated by determining the (3)
- excess anions
- lactic from lactic acidosis or ketone bodies from diabetic ketoacidosis
- anion gap
Anion gap is calculated by (1). The normal range for the anion gap is usually between (2)
- taking the sodium and then subtracting the Cl and HC03
2. 8-16.
An anion gap should really only be present if there is a component of a (1) and not just as a compensation
- metabolic acidosis
Because the lung eliminates C02 as acid, (1) causes a respiratory alkalosis and (2) causes a respiratory acidosis.
- hyperventilation
2. hypoventilation
Hypoventilation can be caused by?
airway obstruction, neurological diseases (stroke, sleep apnea,Guillain-Barre), chest wall deformities, or pulmonary diseases such as asthma or COPD.
It can cause a respiratory acidosis
Winter’s formula:
Checks if there is compensation for METABOLIC ACIDOSIS
PaCO2 = 1.5 {HCO3-} + 8
anion gap formula
AG = [Na+] – ([HCO3-] + [Cl-])
anion gap Determines cause of 1)
metabolic acidosis
Normal Anion Gap
HARD-ASS
Hyperalimentation Addison disease Renal tubular acidosis Diarrhea Acetazolamide Spironolactone Saline infusion
normal anion gap value
8-12 mEq/L
Increased Anion Gap
Indicates accumulation of unmeasured anion.
Diarrhea
Normal Anion Gap Metabolic acidosis
Acetazolamide
Normal Anion Gap Metabolic acidosis
Increased Anion Gap metabolic acidosis causes:
MUDPILES
Methanol Uremia Diabetic Ketoacidosis Propylene glycol Iron tablets or Isoniazid Lactic acidosis Ethylene glycol Salicylates
contraction alkalosis occurs secondary to ECF volume contraction; pH? and K?
pH is INCREASED
K is decreased;
Diabetic Ketoacidosis
Increased Anion Gap metabolic acidosis
Salicylates
Increased Anion Gap metabolic acidosis
Lactic acidosis
Increased Anion Gap metabolic acidosis
Vomiting
Metabolic alkalosis
Bicarb is CONTRAINDICATED
Diabetic Ketoacidosis
asthma, COPD, chronic fibrosis, and interstitial disease
Respiratory Acidosis
Water Deficit =
DBW – CBW
Desirable body water (DBW) =
(DBW) = (Current sodium/140) * CBW
Current body water (CBW) =
Use 0.5 for females
0.6 * Body weight
Insulin shifts K+ into cells –> leads to 1)
hypokalemia.
Filtration fraction =
GFR/RPF where GFR is measured by creatinine clearance and RPF by PAH clearance
RPF measured by 1)
PAH clearance
