Mark K Notes

In order to solve acid-base disorders, it is important to know the normal values for pH, CO₂, and HCO₃ (bicarbonate):

The first value to look at is the pH:

• If pH < 7.35 → the acid-base imbalance is Acidotic
• If pH > 7.45 → the acid-base imbalance is Alkalotic

To determine if the imbalance is metabolic or respiratory, determine whether HCO₃ goes in the same or opposite direction with pH:

Rule of the Bs: If pH and Bicarb move Both in the same direction → Metabolic; otherwise → Respiratory.

Example #1

• pH: 7.3 → Acidotic
• HCO₃: 20 → Same direction (both low)
• This is Metabolic Acidosis

Example #2

• pH: 7.58 → Alkalotic
• HCO₃: 32 → Same direction (both high)
• This is Metabolic Alkalosis

Example #3

• pH: 7.22 → Acidosis
• HCO₃: 35 → Opposite direction
• This is Respiratory Acidosis

"As the pH goes, so goes my patient — except for Potassium."

• If pH is low → everything is low, except potassium (hyperkalemia)
• If pH is high → everything is high, except potassium (hypokalemia)

pH > 7.45 (Alkalosis)

Everything is UP:

• Tachycardia, tachypnea, HTN, seizures, irritability
• Spastic, diarrhea, borborygmi (increased bowel sounds)
• Hyperreflexia (3+, 4+)
• K⁺ is opposite → hypokalemia

Nursing intervention: Pt needs suctioning because of seizure risk

pH < 7.35 (Acidosis)

Everything is DOWN:

• Bradycardia, constipation, absent bowel sounds
• Flaccid, obtunded, lethargy, coma
• Hyporeflexia (0, 1+), bradypnea, low BP
• K⁺ is high → hyperkalemia

Nursing intervention: Pt needs to be ventilated with an Ambu bag — respiratory arrest risk

"MAC Kussmaul" — the only acid-base imbalance to cause Metabolic ACidosis with Kussmaul respirations.

First ask yourself: "Is it LUNG?"

• If YES → Respiratory
  • UNDERventilating → Acidosis (pH under 7.35)
  • OVERventilating → Alkalosis (pH over 7.45)
• If NOT lung → Metabolic
  • Prolonged gastric vomiting/suction (sucking out acid) → Alkalosis
  • Everything else → Metabolic Acidosis (default)

What type of acid-base derangement is present?

• In labor? → Respiratory Alkalosis (overventilating → pH increases)
• Drowning? → Respiratory Acidosis (underventilating → pH decreases)
• Pt on PCA pump? → Respiratory Acidosis (ventilation is down)

Tip: Set your default to Metabolic Acidosis. Always pay attention to the modifying phrase rather than the original noun.

A ventilator is a machine designed to move breathable air into and out of the lungs, aiding patients who are physically unable to breathe or breathing insufficiently. It is equipped with high and low pressure alarms.

High Pressure Alarms (increased resistance to air flow)

Look for obstructions. Appropriate order to address:

1. Kinks in tubing → Solution: Unkink the tube
2. Condensed water in dependent tube → Solution: Empty it
3. Mucus plugs → Solution: Ask pt to turn, cough, deep breathe; or suction the tubing PRN

Low Pressure Alarms (decreased resistance)

• Main tubing disconnection
• O₂ sensor tube disconnection
• In both cases: reconnect unless tube is on floor → Bag pt and call Respiratory Therapist

Ventilator Settings

Weaning Question

The physician wants to wean pt off vent in the morning. At 6 AM, ABGs show respiratory acidosis. What would you do?

• Notify physician that pt is NOT ready to be weaned — pt is underventilated
• If pt were in respiratory alkalosis (overventilated), they WOULD be ready to wean