Acid-Base Disorders + ABG Interpretation Flashcards
What is the most important ECF buffer system? What does it do?
- Bicarbonate - Carbonic Acid Buffer System
- maintains desired pH of ECF or blood
A buffer system of any kind involves the pairing of:
an acid + weak base
OR
a weak acid + base
What kind of mechanism is involved with the Bicarb/Carbonic System? What does this mechanism do?
physiological mechanisms
- in body to adjust the levels of both “sides” of the acid/base pair
- between the opposite chemicals, H+ ions may be absorbed or donated to the solution as needed
- occurs in response to changes in pH
What is often measured as a substitute for carbonic acid concertation in the Bicarb/Carbonate System?
Since carbonic acid has a tendency to dissolve into gaseous form in the bloodstream, CO2 (PaO2) is often measured as a substitute
Equation and component of each side
CO2 + H2O —–> H2CO3 —–> H+ + HCO3-
Left side: respiratory component - physiological adjustment by lungs
Right side: metabolic/kidney component - physiologic adjustment by kidneys
Are buffer systems a permanent fix for pH imbalances?
No - only temporary fix
Respiratory system vs. kidney adjustment time
Respiratory can adjust CO2 blood level within MINUTES/HOURS
Kidneys are slower to adjust H+ and HCO3- blood levels: HOURS/DAYS
Acid/Base Imbalances are characterized by 2 things:
- primary cause
- pH problem
Primary Cause
- the initiating even that causes the acid/base imbalance
categorized as respiratory or metabolic
- Respiratory: affect gas exchange –> changes in CO2 blood level –> imbalance
- Metabolic: lot more variety; can cause changes in HCO3- (bicarb) or H+ levels
pH problem
classified as:
- acidosis (decrease in pH: left side of chart)
- alkalosis (increase in pH: right side of chart)
Compensation
- a mechanism that attempts to balance the state created by the primary cause
- observed when components of opposite sides of the buffer CHANGE to minimize or balance out the initial pH imbalance
- goal: to push pH back towards 7.4
- temporary
- permits survival while body attempts to fix problem or medical intervention occurs
In all acid/base disorders, the ______ is impaired
clearance of CO2 out of the blood
- due to either reduced ventilation or reduced gas exchange at alveoli
Respiratory Acidosis starting situation
pH is less than 7.35
PaCO2 is greater than 45
Respiratory Acidosis issue
decreased CO2 expiration by lungs leaves too much CO2 in the blood
- too acidic
- CO2 accumulation makes pH decrease
Respiratory Acidosis - compensatory action
the kidneys will either:
- retain HCO3-
OR
- excretes H+ ions
Respiratory Acidosis - causes
hypoventilation
- breath slow –> less air pushed out
- narcotic/sedative overdose
- COPD
- muscular disorders resulting in respiratory paralysis
- pulmonary edema
Respiratory Acidosis - treatment
restore effective ventilation - give O2
Respiratory Alkalosis starting situation
- pH is greater than 7.45 (right side)
- PaCO2 is less than 35 (right side)
Respiratory Alkalosis issue
increased CO2 output makes blood level CO2 decrease
too alkaline
Respiratory Alkalosis - compensatory action
kidneys will excrete more HCO3- or retain H+
Respiratory Alkalosis - cause
hyperventilation (exhale quickly)
- increase in heart rate or tidal volume (panic attack)
brain injury or tumor
some lung diseases
Respiratory Alkalosis - signs/symptoms
neurological
- dizziness
- confusion
- seizures
- numbness and tingling in extremities
Respiratory Alkalosis - treatment
fix underlying cause: breathe into paper bag is hyperventilating
Metabolic Acidosis starting situation
- pH is less than 7.35
- HCO3- is less than 22
Metabolic Acidosis issue
loss of HCO3-
or
retention of H+
Metabolic Acidosis - compensatory action
lungs will hyperventilate (blow off more CO2) to excrete excess CO2 out of blood
Metabolic Acidosis - causes
bicarbonate loss (diarrhea)
increased acid production
- lactic acidosis
- diabetic ketoacidosis
- ingestion of acidic poisons
- acute or chronic renal failure
Metabolic Acidosis - signs/symptoms
- GI disturbance
- CNS changes (disorientation)
- bradycardia
- dysrhythmias
- hyperventilation
Metabolic Acidosis - treatment
- IV NAHCO3
- replace fluids and other electrolytes
Metabolic Alkalosis starting situation
- pH is greater than 7.45
- HCO3- is greater than 26
Metabolic Alkalosis issue
retention of HCO3-
OR
loss of H+
- dysfunctional metabolic process
Metabolic Alkalosis - compensatory action
lungs will hyperventilate (blow off less CO2)
Metabolic Alkalosis - causes
- vomiting: loss of hydrochloric acid
- excess ingestion or administration of bicarbonate or alkaline substances
Metabolic Alkalosis - signs/symptoms
- hypokalemia or fluid volume deficit
- mental status changes: confusion, hypoventilation, hyperactive reflexes
Metabolic Alkalosis - treatment
replacement of necessary electrolytes and fluids
What are arterial blood gases and what does the information tell us?
- the numbers and lab values we use when patients gets their blood drawn from their artery
- tells us which of the 4 acid/base imbalance disorders they have
4 steps in ABG interpretation
- Assess PaO2
- Asses pH
- Determine Initiating system
- Determine Compensatory action - if one
What is the partial pressure of O2?
the concentration of our dissolved and free floating molecules in our plasma
- unattached to hemoglobin
- only type able to diffuse across the capillary bed + provide cells/tissues with O2
Partial Compensation
if OPPOSITE system (not initiating system) is outside normal range in the OPPOSITE direction
Successful/Complete Compensation
if OPPOSITE system (not initiating system) is outside normal range in the OPPOSITE direction
AND
pH is in the normal range
No Compensation
If OPPOSITE system (not initiating system) is INSIDE normal range
