Interprets arterial blood gas (ABG) results to determine acid-base status, compensation, and oxygenation status for clinical assessment.
Primary Disorder
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pH Status
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Compensation
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Anion Gap
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Expected Compensation
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Normal ABG values are: pH 7.35-7.45, PaCO₂ 35-45 mmHg, HCO₃⁻ 22-26 mEq/L, PaO₂ 80-95 mmHg, and O₂ saturation 95-99%. Base excess should be within ±2 mEq/L.
Follow these steps: 1) Check pH (acidotic <7.35, alkalotic >7.45), 2) Determine primary disorder (respiratory vs metabolic), 3) Assess compensation, 4) Check oxygenation status, and 5) Calculate anion gap if electrolytes available.
Respiratory acidosis occurs when CO₂ retention causes pH to drop (high PaCO₂, low pH). Metabolic acidosis results from loss of bicarbonate or gain of acid (low HCO₃⁻, low pH). The body compensates through breathing or kidney function respectively.
The body compensates for pH changes through opposite system responses. In metabolic acidosis, lungs hyperventilate to lower CO₂. In respiratory acidosis, kidneys retain HCO₃⁻. Full compensation normalizes pH, partial compensation improves but doesn't normalize it.
Anion gap (Na⁺ - [Cl⁻ + HCO₃⁻]) helps classify metabolic acidosis. Normal gap is 8-12 mEq/L. High anion gap acidosis suggests unmeasured anions (ketones, lactate, toxins), while normal gap acidosis indicates bicarbonate loss or chloride retention.
ABGs are essential for assessing oxygenation and precise acid-base status in critically ill patients. Venous blood gases can assess acid-base status but cannot evaluate oxygenation. ABGs are preferred in respiratory failure, shock, or severe metabolic disorders.
Air bubbles in sample, delays in analysis, improper storage temperature, and patient factors like fever or hypothermia can affect results. Samples should be analyzed within 15 minutes or kept on ice. Ensure proper arterial puncture technique and patient positioning.