التوازن الحمضي القاعدي

Three-step ABG interpretation with worked examples.

السوائل والأملاح وغازات الدم

Normal values

Value	Normal	Notes
pH	7.35 – 7.45	< 7.35 acidosis · > 7.45 alkalosis
PaCO₂	35 – 45 mmHg (4.7 – 6.0 kPa)	The respiratory (acid) component
HCO₃⁻	22 – 26 mEq/L	The metabolic (base) component
PaO₂	80 – 100 mmHg (10.6 – 13.3 kPa)	Oxygenation, not acid–base
SaO₂	95 – 100%

Three steps

1. pH — low = acidosis, high = alkalosis.
2. Which system? ROME — Respiratory Opposite (pH and PaCO₂ move in opposite directions), Metabolic Equal (pH and HCO₃⁻ move in the same direction).
3. Compensation — other value normal = uncompensated; both abnormal with pH still abnormal = partially compensated; pH back in the normal range = fully compensated.

Worked examples

ABG	Interpretation
pH 7.30 · PaCO₂ 40 · HCO₃ 20	Uncompensated metabolic acidosis
pH 7.58 · PaCO₂ 42 · HCO₃ 32	Uncompensated metabolic alkalosis
pH 7.25 · PaCO₂ 60 · HCO₃ 24	Uncompensated respiratory acidosis
pH 7.33 · PaCO₂ 50 · HCO₃ 30	Partially compensated respiratory acidosis
pH 7.53 · PaCO₂ 27 · HCO₃ 22	Uncompensated respiratory alkalosis (e.g., panic attack)
pH 7.38 · PaCO₂ 55 · HCO₃ 32	Fully compensated respiratory acidosis (e.g., COPD)

Common causes

Imbalance	Causes
Respiratory acidosis	Hypoventilation: COPD, opioid or sedative overdose, drowning, cardiac arrest, chest trauma, long-term ventilation problems
Respiratory alkalosis	Hyperventilation: anxiety or panic, pain, fever, high altitude, early salicylate toxicity
Metabolic acidosis	DKA, diarrhea, ileostomy losses, renal failure, lactic acidosis (shock, arrest), salicylate overdose
Metabolic alkalosis	Vomiting, NG suction, diuretics, hypokalemia, excess antacids or bicarbonate, Cushing syndrome

Loss from the top of the GI tract (vomiting, gastric suction) loses acid → alkalosis. Loss from the bottom (diarrhea, ileostomy) loses bicarbonate → acidosis.

اختبر نفسك الآن

23 سؤالاً بنمط الاختبار في السوائل والأملاح وغازات الدم، مع شرح لكل خيار. حساب مجاني بدون بطاقة.

تدرّب مجاناً

التالي:مكافحة العدوى والعزل

Value

Normal

Notes

7.35 – 7.45

< 7.35 acidosis · > 7.45 alkalosis

PaCO₂

35 – 45 mmHg (4.7 – 6.0 kPa)

The respiratory (acid) component

HCO₃⁻

22 – 26 mEq/L

The metabolic (base) component

PaO₂

80 – 100 mmHg (10.6 – 13.3 kPa)

Oxygenation, not acid–base

SaO₂

95 – 100%

Three steps

1. pH — low = acidosis, high = alkalosis.

2. Which system? ROME — Respiratory Opposite (pH and PaCO₂ move in opposite directions), Metabolic Equal (pH and HCO₃⁻ move in the same direction).

3. Compensation — other value normal = uncompensated; both abnormal with pH still abnormal = partially compensated; pH back in the normal range = fully compensated.

Worked examples

ABG	Interpretation
pH 7.30 · PaCO₂ 40 · HCO₃ 20	Uncompensated metabolic acidosis
pH 7.58 · PaCO₂ 42 · HCO₃ 32	Uncompensated metabolic alkalosis
pH 7.25 · PaCO₂ 60 · HCO₃ 24	Uncompensated respiratory acidosis
pH 7.33 · PaCO₂ 50 · HCO₃ 30	Partially compensated respiratory acidosis
pH 7.53 · PaCO₂ 27 · HCO₃ 22	Uncompensated respiratory alkalosis (e.g., panic attack)
pH 7.38 · PaCO₂ 55 · HCO₃ 32	Fully compensated respiratory acidosis (e.g., COPD)

Common causes

Imbalance	Causes
Respiratory acidosis	Hypoventilation: COPD, opioid or sedative overdose, drowning, cardiac arrest, chest trauma, long-term ventilation problems
Respiratory alkalosis	Hyperventilation: anxiety or panic, pain, fever, high altitude, early salicylate toxicity
Metabolic acidosis	DKA, diarrhea, ileostomy losses, renal failure, lactic acidosis (shock, arrest), salicylate overdose
Metabolic alkalosis	Vomiting, NG suction, diuretics, hypokalemia, excess antacids or bicarbonate, Cushing syndrome

Loss from the top of the GI tract (vomiting, gastric suction) loses acid → alkalosis. Loss from the bottom (diarrhea, ileostomy) loses bicarbonate → acidosis.