Exam 2- Acid-Base Disorders (6/22/23) Flashcards
In order to ensure optimal function of enzymatic function, acid-base balance is tightly regulated at what pH?
- 7.35 to 7.45
What causes acidemia?
- Excess production of H+ (in relation to hydroxyl ions)
What causes alkalemia?
- Excess production of OH- (in relation to hydrogen ions)
What is known as the measured hydrogen concentration?
- pH
The Power of Hydrogen
The stability of pH is managed by what three factors?
- CO2 (enters/leaves the body via lungs)
- HCO3 (enters/leaves the body via kidneys
Via proximal tubule) - H+ (reabsorbed Via distal tubule and collecting duct)
What is the equation to calculate pH?
pH = 6.1 + log [serum bicarb/(0.03 x PaCO2)]
How can you tell if an acid-base disorder is a primary disorder with secondary compensation?
- Both PaCO2 and HCO3 change in the same direction
How can you tell if an acid-base disorder is a mixed acid/base problem?
- PaCO2 and HCO3 are in different directions.
What is the Acid/Base Disorder
pH: 7.34
PCO2: 48
HCO3: 24
Uncompensated Respiratory Acidosis
What is the Acid/Base Disorder
pH: 7.58
PCO2: 38
HCO3: 29
Uncompensated Metabolic Alkalosis
What is the Acid/Base Disorder
pH: 7.28
PCO2: 42
HCO3: 18
Uncompensated Metabolic Acidosis
What is the Acid/Base Disorder
pH: 7.48
PCO2: 32
HCO3: 22
Uncompensated Respiratory Alkalosis
If your patient has normal lungs, what should their PaO2 be when they are on 60% FiO2?
- PaO2: 240 to 300 mmHg
Normal range of PaO2: 80-100 mmHg
FiO2 of room air is 21%
FIO2 of 60% is about 3x of room air.
PaO2 will be between 240-300 mmHg
Cardiovascular Consequences of Acidosis
- Impaired contractility at pH 7.2
- Decreased contractility
- Decreased arterial blood pressure
- Sensitive to re-entry dysrhythmias
- Decrease threshold for V-fib
- Decreased responsiveness to catecholamines at pH 7.1
Nervous System Consequence of Acidosis
- Obtundation
- Coma
Pulmonary Consequences of Acidosis
- Hyperventilation (d/t compensation, blowing off CO2)
- Dyspnea
- Respiratory Muscle Fatigue
Metabolism Consequence of Acidosis
- Hyperkalemia (contributes to reentry dysrhythmias)
- Insulin Resistance
- Inhibition of anaerobic glycolysis
Define Respiratory Acidosis
- An acute decrease in alveolar ventilation resulting in increase PaCO2
- pH < 7.35
- Caused by respiratory failure
What are the causes of Respiratory Acidosis?
- Drug-induced ventilatory depression
- Permissive hypercapnia
- Upper airway obstruction
- Status asthmaticus
- Restriction of ventilation (rib fx, flail chest)
- Disorder of neuromuscular function
- MH
- PNA/ Pulmonary Edema, Pleural Effusion
What are the three categories that can cause Respiratory Acidosis?
- Central ventilation control (neuro/brain)
- Peripheral ventilation control (neuromuscular disease)
- VQ mismatch (Pneumonia)
With acute hypercarbia, how long does it take for the bicarb to compensate for the acid-base disorder?
If PaCO2 increases by 10 mmHg, this will increase _______ mEq/L of HCO3- for the system to be compensated.
- Very slowly (2-3 days)
- Increase in 1 mEq/L of HCO3 for every 10 mmHg of PaCO2
How much will HCO3- increase with compensated chronic hypercarbia?
- ↑ PaCO2 of 10 mmHg = ↑ HCO3- by 3 mEq/L
This is prevalent in COPD patients
Upon arrival at the ICU, the patient has a PaCO2 of 80 mmHg.
What is the expected HCO3 if this patient has compensated acute hypercapnia?
- 28 mEq/L
Normal PaCO2 level: 40 mmHg
Normal HCO3 level: 24 mEq/L
PaCO2 of the patient is 80 mmHg
PaCO2 increased by 40 mmHg
For acute hypercapnia, ↑PaCO2 of 10 mmHg=↑HCO3- of 1 mEq
Upon arrival at the ICU, the patient has a PaCO2 of 80 mmHg.
What is the expected HCO3 if this patient has compensated chronic hypercapnia?
- 36 mEq/L
Normal PaCO2 level: 40 mmHg
Normal HCO3 level: 24 mEq/L
PaCO2 of the patient is 80 mmHg
PaCO2 increased by 40 mmHg
Chronic Hypercapnia: ↑PaCO2 10 mmHg=↑HCO3- 3 mEq
HCO3- increase by 12 mEq/L
Expected HCO3- = 24 + 12 = 36 mEq/L