Arterial Blood Gas Flashcards
Normal pH range
7.35-7.45
Arterial blood gas is an essential part of diagnosing and managing
Oxygenation status
Ventilation failure
Acid base balance
Normal PaO2 range
80-100 mmHg
Normal PaCO2 range
35-45 mmHg
Normal HCO3 range
22-26 mmol/L
Bicarbonate is a _________ value.
Calculated
The base excess indicates the amount of excess or insufficient level of
Bicarbonate
Normal range of BE
A negative BE indicates a base
-2 to 2 mEq/L
Deficit in the blood
Normal SaO2
> 95%
A normal [H+] of ______ corresponds to a pH of 7.40
40 nEq/L
Changes in pH are inversely related to changes in [H+]. A decrease in pH is associated with
An increase in [H+]
How much CO2 does the body produce daily?
15,000 mmol
How much nonvolatile acids does the body produce daily?
50-100 mEq nonvolatile acids
What organs attempt to maintain balance of acids in the body?
Lungs and kidneys
These two buffers work in pairs
carbonic acid and base bicarbonate
H2CO3 and NaHCO3
The respiratory buffer response maintains that blood pH will change according to the level of ____ which triggers the lungs to
H2CO3
Increase or decrease the rate and depth of ventilation
Activation of the lungs to compensate for an imbalance starts to occur within
1-3 min
The renal buffer response is that kidneys excrete or retain bicarbonate. If blood pH decreases, the kidneys will compensate by
Entraining HCO3
How long can it take the renal system to correct an imbalance?
Hours to days
If decreased pH
Increased CO2
Decreased ventilation
Respiratory acidosis
What can cause respiratory acidosis
CNS depression Pleural disease COPD/ARDS Musculoskeletal disorders Compensation for metabolic alkalosis All of these can decrease ventilation
What is the difference between acute and chronic respiratory acidosis?
Acute - little kidney involvement
Chronic - renal compensation via synthesis and retention of HCO3
With acute resp acidosis, pH decrease by ___ for 10 mmHg increase in CO2
0.08
Retention of CO2 results in decreased
Chloride
Can lead to hypochloremia because the body wants to balance charges
With chronic resp acidosis, pH decreases by __ for 10 mmHg increase in CO2
0.03
If increased pH
Decreased CO2
Increased ventilation
Respiratory alkalosis
What can cause respiratory alkalosis?
Inter cerebral hemorrhage Salicylate and progesterone drug usage Anxiety, which decreases lung compliance Cirrhosis of the liver Sepsis
What is the difference between acute and chronic respiratory alkalosis?
Acute - HCO3 decreases by 2 mEq/L for every 10 mmHg in PCO2
Chronic - HCO3 decreases by 4
Respiratory alkalosis causes decreased bicarb _____ and decreased ______ excretion to normalize pH
Reabsorption, ammonium
If decreased pH
Decreased HCO3
Metabolic acidosis
What is Winter’s formula and what does it tell you?
PCO2 = 1.5(HCO3) + 8 +/- 2
The degree of compensation for metabolic acidosis
How long does it take for complete activation of respiratory compensation?
12-24 hours
For met acidosis, there is a decrease of ____ for every decrease of 1 mEq/L HCO3
1.2 mmHg
Causes of metabolic gap acidosis
Methanol Uremia DKA Paraldehyde INH Lactic acidosis Ethylene glycol Salicylate
Causes of nongap metabolic acidosis
Hyperalimentation Acetazolamide RTA (calculate urine anion gap) Diarrhea Pancreatic fistula
If increased pH
Increased HCO3
Metabolic alkalosis
In metabolic alkalosis, PCO2 increases by ___ for every increase of 1 mEq/L in HCO3
0.7
Metabolic alkalosis is caused by
Vomiting Diuretics Chronic diarrhea Hypokalemia Renal failure
Mixed acid base disorders describes ___ acid base disorders at one time
Two or more
What is the delta gap? What value equals metabolic alkalosis?
Delta HCO3 = HCO3 + change in anion gap
> 24
What kind of respiratory problem is it if pH and PaCO2 move in opposite directions?
Primary
What kind of problem is it if pH and HCO3 are moving in the same direction?
Primary
What level of Pao2 indicates hypoxemia?
< 80 mmHg
Change in PaO2 is associated with a change in pH, the disorder is ______. If the compensatory process brings the pH to within the clinically acceptable range (7.30 - 7.50), the disorder is
Acute, chronic
The estimate of how much strong base or acid needed to correct the metabolic component of an acid base disorder is
Base excess
The formula for the amount needed to correct an acid base disorder is
0.3 x body weight x BE
Formula for anion gap
AG = (Na + K) - (Cl + HCO3)
T or F. The system does not have the ability to overcompensate.
False
If pH remains outside of the normal range after compensation, then it is
Partially compensated
In a compensated state, when the pH decreases, PaCO2 should also decrease because
The lungs are acting as a buffer response
Always strongly suggest a metabolic acidosis
High anion gap
Ketones present, diabetic ketoacidosis
Hyperglycemia
Hypokalemia and or hypochloremia
Suggests metabolic alkalosis
Common with normal anion gap acidosis
Hyperchloremia
Elevated creatinine and urea
Suggests uremic acidosis or hypovolemia (prerenal renal failure)
Elevated creatinine
Consider ketoacidosis
Consider ketoacidosis or hyperosmolar nonketotic syndrome
Elevated glucose
Urine dipstick test for glucose and ketones
Glucose - hyperglycemia
Ketones - ketoacidosis
