🩸 Lecture 1
Acid-Base Balance
pH, CO2, HCO3, Rule of Bs, ventilators, high/low alarms.
Overview
Normal Values — Memorize These!
| Value | Normal Range | If LOW | If HIGH |
|---|---|---|---|
| pH | 7.35–7.45 | Acidosis | Alkalosis |
| CO2 | 35–45 | Alkalosis (blowing off) | Acidosis (retaining) |
| HCO3 | 22–26 | Acidosis | Alkalosis |
🅱️ Rule of the Bs
pH and Bicarb go SAME direction = METABOLIC
pH and Bicarb go OPPOSITE = RESPIRATORY
pH and Bicarb go OPPOSITE = RESPIRATORY
✅
Example 1: pH 7.3↓ + HCO3 20↓ → BOTH down = Metabolic Acidosis
✅
Example 2: pH 7.58↑ + HCO3 32↑ → BOTH up = Metabolic Alkalosis
✅
Example 3: pH 7.22↓ + HCO3 35↑ → OPPOSITE = Respiratory Acidosis
⚠️
Potassium EXCEPTION: Everything follows pH — EXCEPT K+. K+ always goes opposite!
📌 Default Rule
Set default to METABOLIC ACIDOSIS
• Lung problem? → Respiratory
• Overventilating? → Alkalosis | Underventilating? → Acidosis
• Prolonged vomiting/GI suction? → Metabolic ALKALOSIS
• Everything else? → Metabolic ACIDOSIS (your default!)
• Overventilating? → Alkalosis | Underventilating? → Acidosis
• Prolonged vomiting/GI suction? → Metabolic ALKALOSIS
• Everything else? → Metabolic ACIDOSIS (your default!)
| Alkalosis (pH >7.45) | Acidosis (pH <7.35) |
|---|---|
| Tachy, HTN, seizures, spastic, diarrhea | Brady, low BP, lethargy, flaccid, constipation |
| HYPO-kalemia | HYPER-kalemia |
| Nursing: suction (seizure risk) | Nursing: Ambu bag (resp arrest) |
Ventilators
⚠️
HIGH pressure alarm = Obstruction. Order: (1) Unkink (2) Empty water (3) Cough/deep breathe (4) Suction
⚠️
LOW pressure alarm = Disconnection. Reconnect. If on floor → bag pt, call RT.
| Setting | Result |
|---|---|
| Too HIGH → Overventilating | Resp ALKALOSIS |
| Too LOW → Underventilating | Resp ACIDOSIS |
📌
Weaning: ABG shows Resp ACIDOSIS → NOT ready to wean. Alkalosis → ready.
Practice Tips
🎯 Exam Tips
In Labor → Resp ALKALOSIS (overventilating)
Drowning → Resp ACIDOSIS (underventilating)
PCA pump → Resp ACIDOSIS (meds slow breathing)
Drowning → Resp ACIDOSIS (underventilating)
PCA pump → Resp ACIDOSIS (meds slow breathing)
⚠️
MAC Kussmaul = ONLY Metabolic ACidosis causes Kussmaul respirations. NEVER pick it for respiratory acidosis!
📖 Notes for Dummies
🧠 Think of it this way…
Your blood needs to stay in perfect balance — not too acidic, not too basic. When something goes wrong (lungs or kidneys), the balance shifts. Your job: figure out WHERE the problem is and WHAT it's doing to the body.
🍋
Acid = sour like lemon juice. Low pH = too much acid = ACIDOSIS.
Normal pH 7.35–7.45. Below 7.35 = too acidic. Above 7.45 = too basic (alkalotic).
Normal pH 7.35–7.45. Below 7.35 = too acidic. Above 7.45 = too basic (alkalotic).
🫁
LUNG problem? → RESPIRATORY. Lungs control CO2.
Breathing too FAST = blows off CO2 = less acid = ALKALOSIS
Breathing too SLOW = traps CO2 = more acid = ACIDOSIS
Breathing too FAST = blows off CO2 = less acid = ALKALOSIS
Breathing too SLOW = traps CO2 = more acid = ACIDOSIS
🫘
NOT a lung problem? → METABOLIC. Kidneys control bicarbonate (HCO3).
Diabetes, kidney failure, diarrhea = Metabolic ACIDOSIS (your default!)
Vomiting A LOT = losing stomach acid = Metabolic ALKALOSIS
Diabetes, kidney failure, diarrhea = Metabolic ACIDOSIS (your default!)
Vomiting A LOT = losing stomach acid = Metabolic ALKALOSIS
🪄 Super Simple Trick — Rule of the Bs
pH and HCO3 (Bicarb) both go LOW? → Same direction = METABOLIC
pH goes one way, HCO3 goes opposite? → RESPIRATORY
pH goes one way, HCO3 goes opposite? → RESPIRATORY
Example: pH 7.2 (LOW) + HCO3 18 (LOW) → both low = same direction = Metabolic Acidosis ✅
🍌
Potassium is the rebel! Low pH (acidosis) → HIGH potassium | High pH (alkalosis) → LOW potassium
📝 Common Scenarios in Plain English:
🤰 Woman in labor breathing fast → Resp ALKALOSIS (overbreathing)
🏊 Drowning victim → Resp ACIDOSIS (can't breathe, CO2 trapped)
💊 Patient on PCA pump → Resp ACIDOSIS (meds slow breathing)
🤮 Patient vomiting for days → Metabolic ALKALOSIS (losing stomach acid)
🍬 Diabetic in DKA → Metabolic ACIDOSIS (default!)
🏊 Drowning victim → Resp ACIDOSIS (can't breathe, CO2 trapped)
💊 Patient on PCA pump → Resp ACIDOSIS (meds slow breathing)
🤮 Patient vomiting for days → Metabolic ALKALOSIS (losing stomach acid)
🍬 Diabetic in DKA → Metabolic ACIDOSIS (default!)