Acid Base Balance Flashcards
What are examples of volatile acids & what type of metabolism do volatile acids use?
Volatile acids include carbonic acid and uses aerobic metabolism
What are examples of nonvolatile acids & what type of metabolism do nonvolatile acids use?
Nonvolatile acids include lactic acid & hydrogen phosphate and use anaerobic metabolism
How are body acids generated?
Through aerobic metabolism with volatile acids and anaerobic metabolism with nonvolatile acids
What does it mean to be an acid?
An acid is a compound that contains hydrogen and reacts with water to form hydrogen ions
Strong acids…
readily & irreversibly give up hydrogen ions
Define acidemia
ph <7.35 and is the net effect of all the primary processes and compensatory mechanisms on pH
Why is pH important for normal physiology?
-affects ionization
Responsible for the movement of certain
molecules in & out of cells
-Can affect enzyme activity
-Can alter the degree of ionization of proteins & drugs
-pH & PCO2 demonstrate fairly predictable changes in pathological conditions
-Changes in ventilation, perfusion, and electrolyte composition can rapidly alter [H+] & the acid based balance
What are the physiological effects of acidemia?
-Pushes carbonic acid equation to the right
-Net effect is inhibitory
-Coronary system dilates & respiratory system constricts
-decreased SVR, contractility–> hypotension
-vasculature less responsive to endogenous
catecholamines
- threshold for vfib is decreased
-tissue hypoxia despite rightward shift of hgb affinity for O2
-Progressive hyperkalemia (increase of 0.6 mEq/L for 0.1 drop in pH)—> results in lethal dysrhythmias
-Increased CBF & intracranial HTN- “CO2 narcosis”
-CNS depression (affect is greater than what the epi & norepi can do to help fix it)
Using general terms, how does kidney function alter acid base balance?
- Control reabsorption of bicarb
- Form new bicarb
- & excrete H+ in the form of titratable & ammonium acids
What does the kidney do during acidosis?
Increase reabsorption of bicarb, increased excretion of H+ through titratable & ammonium acids
What does the kidney do during alkalosis?
excretes large amounts of bicarb
Metabolic alkalosis is commonly associated with increased mineralcorticoid activity even in the absence of sodium & chloride depletion
Define respiratory acidosis, compensatory measures, and determination of acute vs. chronic
pH <7.35, CO2 >45; compensatory mechanism bicarb <22; for acute vs. chronic would need pt history or if fully compensated and pH not 7.4 then most likely chronic
Define respiratory alkalosis, compensatory measures, and determination of acute vs. chronic
pH >7.45, CO2 <35; compensation: bicarb >26; would need pt history or if fully compensated and pH not 7.4 then most likely chronic
What are the possible mixed disorders?
- pH 7.4, PCO2 and Bicarb are opposite of each other
- pH <7.35, PCO2 high & bicarb low
- pH >7.45, PCO2 low and bicarb high
What is metabolic acidosis?
pH <7.35, bicarb <22, compensation: CO2 >45
What can anion gap tell us about the source of metabolic acidosis?
If it is high anion gap acidosis then MUDPILES is the answer
If it is normal anion gap acidosis then FUSEDCARS is the answer- lead to reduced bicarb & increased chloride
How is anion gap calculated?
[Na+]-[HCO3-]-[Cl-]
anion gap of 12 is normal
What is the normal range of base excess?
-2 to +2
How do you calculate base excess?
BE= calculated bicarb- 24 (normal bicarb)
What does a BE of >+2 indicate?
excess base
What does a BE of >-2 indicate?
reduced base
What is the “base” in base excess?
the sum of weak acids including hemoglobin, plasma proteins, phosphate, and bicarb
What does base excess signifiy?
Helps to quantify the metabolic acidosis
What is metabolic alkalosis?
pH >7.45, bicarb >26, compensation: CO2 <35
What happens to the base excess in metabolic alkalosis?
the base excess increases in metabolic alkalosis
Describe the strength & efficiency (timing) of the acid based buffer systems in the body.
- Buffers- immediate- weakest
- Respiratory- hours to 24 hours- middle
- Renal-3-5 days- strongest
List the anesthetic considerations of acidemia:
- Potentiates CNS depressant effects of most sedatives & anesthetic agents
- increased sedation & depression of airway reflexes (predispose to aspiration)
- direct circulatory depressant effects of anesthetics may be exaggerated
- Anesthetic agents that rapidly decrease sympathetic tone can indirectly produce unopposed circulatory depression
- Avoid succ d/t hyperkalemia
List the anesthetic considerations of alkalemia:
- combination of alkalemia & hypokalemia can precipitate dysrhythmias
- general ischemia can occur with decreased CBF (particularly in the presence of hypotension)
- Respiratory alkalosis prolongs the duration of opioid induced respiratory depression
