Acid Base Balance and Oxygen Management Flashcards
FiO2
Fraction of inspired oxygen
PaO2
Partial arterial pressure of oxygen
PAO2
Partial pressure of alveolar oxygen
PvO2
Partial pressure of venous oxygen
Sao2
Arterial saturation of oxygen
Body’s preferred source of energy
Glucose
Aerobic Cellular metabolism
Glycolysis (2ATP) -> Pyruvic acid-> Acetyl coA -> Krebs cycle (2ATP) -> electron transport chain (34ATP)= 38 total ATP
What are the primary biproducts of Aerobic metabolism?
H2O and CO2
Anaerobic Cellular metabolism
Glycolysis (2ATP) -> Pyruvic acid -> Lactic acid
What is the primary biproduct of Anaerobic metabolism?
Lactic acid
What is shock?
Inadequate tissue oxygenation
Lactate levels
Normal = 0.5-1.5
>2.0 in ill patients signals lactic acidosis
Left shift of Oxyhemoglobin dissociation curve
Less hydrogen, holds on to oxygen instead.
Alkalosis
Causes of Left shift of Oxyhemoglobin dissociation curve
Low temp
Low 2-3DPG
Carbon Monoxide
Right shift of Oxyhemoglobin dissociation curve
Hydrogen rich environment.
Releases O2 quickly.
Acidosis
Causes of Right shift of Oxyhemoglobin dissociation curve
Raised acidosis
Raised temp
Raised 2-3 DPG
Reduced oxygenation
Carbonic acid - bicarbonate buffer system formula
Co2 + H20 = H2co3 (carbonic acid) = H+ / HCO3-
Fastest buffering system
Carbonic acid - bicarbonate buffering system work second to second in blood, lungs and kidneys but is easy to overwhelm.
Intermediate buffering system
Lungs adjust H2CO3 by blowing off or holding onto CO2.
Works Minute to Minute
Slow buffering system
Kidneys can reabsorb, create, or excrete HCO3- or H+.
Takes hours to days.
PaCO2 change of __ mmHg causes a Ph change of __ in opposite direction.
10 mmHg
0.08
Primary intracellular cation
Potassium
Primary extracellular cation
Sodium
For every change in Ph of __ , there is a change in Potassium of __ MEq/L in the opposite direction.
- 1
0. 6
For every change in PaCO2 of __ mmHg, there is a change in Potassium of __ MEq/L in the opposite direction.
10
0.5
What causes a false high Potassium level?
Acidosis
What causes a false low Potassium level?
Alkalosis
Treatment of Hyperkalemia >5.5
Correct acid-base balance first
Calcium chloride (raises action potential)
NaHCO3 (Raises Ph, Moves K+ intracellular)
D50/Insulin
B2 agonist (albuterol)
Lasix
Kayexalate
Treatment Hypokalemia <3.5
Correct acid-base balance
Do not exceed 0.5-1.0 MEq/kg/hr
Normal is 10-20 MEq/hr
What is a normal Arterial Ph?
7.35-7.45
What is a normal PaCO2?
35-45
What is a normal Arterial HCO3-?
22-26
What is a normal PaO2?
80-100
What is a normal SaO2?
> 95%
What is a normal BE (base excess)?
-2 to 2
ABG interpretation
Ph 7.19
PCo2 66
HCO3- 24
Uncompensated respiratory acidosis
ABG interpretation
Ph 7.27
PCo2 37
HCO3- 14
Uncompensated metabolic acidosis
ABG interpretation
Ph 7.58
PCo2 14
HCO3- 22
Uncompensated respiratory alkalosis
ABG interpretation
Ph 7.48
PCo2 41
HCO3- 30
Uncompensated metabolic alkalosis
ABG interpretation
Ph 7.09
PCo2 60
HCO3- 14
Mixed disturbance (Both are causing issues)
ABG interpretation
Ph 7.31
PCo2 68
HCO3- 34
Partially compensated respiratory acidosis
ABG interpretation
Ph 7.17
PCo2 31
HCO3- 04
Partially compensated metabolic acidosis
ABG interpretation
Ph 7.51
PCo2 29
HCO3- 37
Mixed disturbance
PaO2 should equal __ times Fio2
5
Formula for bicarb replacement
Kg/4 x Base deficit = MEq of bicarb needed
For every change in HCO3- of __ MEq, the Ph changes __ in the same direction.
10
0.15
Define Respiratory Acidosis
Failure to remove CO2 from plasma / lungs.
Ph <7.40, CO2> 45
Fast causes of Respiratory Acidosis
Failure to get CO2 to the lungs (decreased Cardiac Output).
Failure to get CO2 out of the lungs (decreased Minute Volume).
Slow causes of Respiratory Acidosis
Bronchospasm
COPD
V/Q mismatch (P.E., ARDS, Pneumonia)
Pulmonary Edema
Treatment of Respiratory Acidosis
Remove CO2 by increasing alveolar minute volume
Define Respiratory Alkalosis
Alveolar hyperventilation causing removal of too much CO2.
Ph >7.40
CO2 <35
Causes of hyperventilation
Tissue hypoxia secondary to poor supply
Tissue hypoxia secondary to excessive demand
Mechanical hyperventilation (most common)
Anxiety
Treatment of Respiratory Alkalosis
Control anxiety
Decrease alveolar minute volume (decrease rate, then volume)
Define Metabolic Acidosis
Ph <7.40
HCO3- <22
Anion Gap >20
Normal Anion Gap
8-16 (w/o K+ factored)
10-20 (with K+ factored)
Causes of Metabolic Acidosis
#1 Lactic Acidosis #2 DKA #3 Renal failure #4 Toxins
Primary toxin causing metabolic acidosis
Alcohols / Methanol / Ethylene Glycol
MUDPILES
Causes of Metabolic Acidosis Methanol (toxin) Uremia (renal failure) DKA Paraldehyde (toxin) Iron (toxin) Lactate Ethylene glycol (toxin) Salicylate (toxin)
Treatment of Metabolic Acidosis
Treat the cause!
Lactic? Good oxygenation, improve cardiac output
DKA? Control sugar, correct acidosis
Renal failure? Identify treatable conditions
Toxins? stop intake, look for antidote, supportive care
Metabolic Alkalosis
Too much HCO3 or too little H+ (hydrogen = acid)
Ph >7.40
HCO3- >26
Worst of the Worst!
Causes of Metabolic Alkalosis
Think Electrolyte disorder! (#1 cause)
GI loss of H+ (OG/NG suctioning, N/V)
GI loss of electrolytes (diarrhea)
Renal loss of potassium and hydrogen
Treatment of Metabolic Alkalosis
Identify and correct electrolyte abnormalities
Focus on Potassium, Magnesium, and Calcium