Lecture 19: Introduction to Acid Base Disturbances Flashcards
Know how to read the davenport diagram in the slides
Ok
What is the difference between acute and chronic respiratory acidosis/alkalosis?
In chronic, kidney has learned to compensate for respiratory disturbance and is able to drive the pH to normal
If you have a metabolic problem _____ will compensate and ______ will correct
If you have a respiratory problem _____ will compensate
- lungs, kidneys
- kidneys
What does anion gap mean?
How is this calculated?
-how many cations are there than anions in the blood/urine? High means you lost anions you shouldn’t have lost (like HCO3-)
Plasma: Na - Cl + HCO3 = should be 11-12
Urine: Na+ + K+ - Cl- = should 20 - 90
What does osmolal gap mean?
How is this calculated?
- how many more solutes are there in the blood/urine compared to normal.\
- Serum Osm/Urine Osm - 2(Na) + K + glucose/18 + BUN/2.8
How do you calculate Delta Gap?
How do you calculate Delta HCO3-?
Anion Gap - 12
Normal HCO3- - Delta Gap
If [HCO3-] = delta[HCO3-]
If [HCO3-] > delta[HCO3-]
If [HCO3-] < delta[HCO3-]
Acid base disorder
Metabolic alkalosis + HAGMA
NAGMA + HAGMA
If AG/HCO3- ratio is 1:1 = <1 = >1-2 = >2 =
HAGMA
Losing HCO3-
Lactic acidosis
Metabolic alkalosis
Respiratory acidosis
Primary defect
Compensatory response
Alveolar hypoventilation (keeping too much CO2) Kidneys absorb more HCO3- back in
Causes of Respiratory Acidosis
Acute (CANS): CNS depression Airway obstruction Neuromuscular dz Severe lung issues
Chronic:
COPD
In acute respiratory acidosis, for every 10 increase in CO2, kidneys should reabsorb how much HCO3-?
In chronic respiratory acidosis, for every 10 increase in CO2, kidneys should reabsorb how much HCO3-?
Increase by 1
Increase by 3.5
Respiratory Alkalosis
Primary defect
Compensatory response
Alveolar hyperventilation (exhaling too much CO2) Kidneys will excrete HCO3-
In acute respiratory alkalosis, for every decrease 10 in CO2, kidneys should excrete how much HCO3-?
In chronic respiratory alkalosis, for every decrease 10 in CO2, kidneys should excrete how much HCO3-?
Decrease by 2
Decrease by 5
What are the causes of respiratory alkalosis?
CHAMPS
CNS disease Hypoxia Anxiety Mechanical Ventilators Progesterone Salicylates/Sepsis
Symptoms of acute and chronic respiratory alkalosis
Acute: Tachypnea, hyperpnea
Chronic: asymptomatic
Metabolic acidosis
Primary defect
Compensatory response
Renal correction
- Kidneys excrete too much HCO3-
- Hyperventilation to expel CO2
- kidneys will excrete more H+ in urine and reabsorb more HCO3-
Why is a high serum anion gap indicative of metabolic acidosis (HAGMA)?
If you have more cations than anions in the blood than normal (high anion gap), you have lost anions you shouldn’t have lost (HCO3-)
What is NAGMA?
Non anion gap metabolic acidosis. Anion gap stays the same, but that’s because you kept more Cl- which covered up the fact that you lost HCO3-
What are the causes of HAGMA?
GOLDMARK
Glycols Okoproline Lactate D-lactate Methanol Aspirin Renal failure Ketoacidosis
What are the causes of NAGMA?
HARDUPS
Hyperalimentation Acetazolamide Renal tubular acidosis Diarrhea Uterosigmoid fistula Posthypocapnia Spironolacton
What are the symptoms of metabolic acidosis?
Long deep breaths, normal rate
Vomiting nausea and malaise when pH drops below 7.10
How do you calculate how much PaCO2 is in the blood during metabolic acidosis/Winter’s formula?
PaCO2 = 40 - (1.2 x (24 -HCO3-))
Winter Formula: (PaCO2 = 1.5 (HCO3-)) + 8 (+/-2)
How do you calculate how much PaCO2 is in the blood during metabolic alkalosis?
PaCO2 = 40+ (0.7 x (HCO3-) - 34)
If a patient with NAGMA exhibits HCO3- loss, normal AG and hyperchloremia, what is the most likely cause?
Type 2 RTA (diarrhea)
If a patient with NAGMA is unable to excrete H+ in the urine, what is the most likely cause?
Type 1 RTA
If a patient with NAGMA exhibits hypoaldosteronism and hyperkalemia, what is the most likely cause?
Type 4 RTA
Metabolic alkalosis
Primary defect
Compensatory response
Renal correction
Kidneys absorb too much HCO3-
Hypoventilation (try to keep CO2 in)
Kidneys excrete HCO3- and decrease H+ in urine
What are the causes of Metabolic alkalosis?
CLEVER PD
Contraction (volume) Licorice Endo problems Vomiting Excess Alkali Refeeding Alkalosis Post hypercapnia Diuretics
What are the symptoms of severe metabolic alkalosis?
Hypocalcemia (Ca2+ binds to proteins)
Chloride responsive metabolic alkalosis is caused by….
Treated by?
Losing Cl- so you can’t regulate acid properly
Normal saline
Chloride resistant metabolic alkalosis
Something else is causing the acid loss, not Cl- imbalance
If your predicted compensation does not match what happens, this means
Patient has mixed acid-base disorder
