Nursing 360

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Regulatory Systems for acid base regulation

BUFFER SYSTEMS: most rapid system
INTRACELLULAR & EXTRACELLULAR
CARBONIC/BICARBONATE PHOSPHATE
HEMOGLOBIN
CELLS

RESPIRATORY: C02/Carbonic Acid (H2C03) regulation system. Next most rapid

RENAL: bicarbonate regulatory system (HC03): slowest

ACID-BASE IMBALANCES: CAUSES & TREATMENT

1. Acidosis

a. Respiratory: carbonic acid excess

1. Causes: respiratory failure

2. ABG: pH: 7.2; pCO2 50, HCO3 24, pO2 60

3. Clinical Signs: CNS depression, headache, tachycardia, cardiac arrhythmias

4. Treatment: improve ventilation

b. Metabolic: bicarb deficit (relative to acid, bicarb is used up buffering the acid

1. Causes: diabetic ketoacidosis, shock, tissue anoxia, renal failure, severe infection, loss of Gl fluids (diarrhea, intestinal suctioning)

2. ABG: pH:7.22; pCO235, HC03-15,p02 90

3. Clinical Signs: same CNS depression; severe leads to ventricular arrhythmias and myocardial contractility. Death from brainstem dysfunction when pH <6.9

4. Treatment: give bicarb & treat primary disorder

2. Alkalosis

a. Respiratory: carbonic acid deficit

1. Causes: usually hyperventilation

2. ABG: pH: 7.52; pCO2 20, HCO3-26, pO2 90

3. Clinical Signs: paresthesias, diaphoresis, light headedness - fainting

4. Treatment: treat disorder: control ventilation

b. Metabolic bicarb excess (decrease of acid)

1. Causes: Gastric suctioning, emesis, excessive intake of bicarbonate or its precursors, extracellular fluid volume depletion

2. ABG: pH: 7.62; pCO2 45. HCO3 -30, pO2 90

3. Clinical Signs: neuromuscular irritability: tingling »tetany» seizures; signs of the precursor problem.

4. Treatment: treat disorder

Normal blood gas

Method to identify pH and possible causes

1. Identify if pH normal, acid or basic

2. Check PC02 to see if respiratory cause for the acid or basic problem (results should match the pH reading)

3. Check HC03 to see if metabolic cause for the acid Or basic problem.

Compensation

When the cause for the pH alteration is found, identify if the other mechanism is compensating:
ie: pH: 7.25
PC02: 50
HC03: 30

Acid pH

Respiratory cause: PC02 elevated (remember changes to carbonic acid in body)

Bicarb elevated: metabolic compensation with elevating bicarb.

COMPENSATING:

What if: pH 7.4 and same bicarb and C02?
Then pH is compensated,

Practice Examples

Identify type of pH problem and if uncompensated or compensating

1.
pH: 7.25
pC02 : 50
HC03 : 24
Answer:

2.
pH: 7.54
pC02 : 50
HC03: 30
Answer:

3.
pH: 7.5
pC02 : 42
HC03 : 32
Answer:

4.
pH: 7.56
pC02: 53
HC03: 29
Answer:

5.
pH: 7.1
pC02 : 40
HC03 : 18
Answer:

6.
pH: 7.0
PC02: 53
HC03: 31
Answer:

7.
pH: 7.45
pC02: 40
HC03: 24
Answer:

8.
pH: 7.55
pC02: 30
HC03: 18
Answer:

9.
pH: 7.23
pC02: 30
HC03: 16
Answer:

10.
pH 7.5
pC02: 36
HC03: 28
Answer:

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