16 worked blood gases covering metabolic and respiratory acidosis, alkalosis, compensation and opposing effects.
Start with a single disturbance, then compare the mixed cases. The mixed-disorder guide explains how pH and compensation distinguish these patterns.
Synthetic teaching cases. All values and interpretations below are generated by the calculator’s current equations. They are not patient records or independent validation cases.
Arterial sample; chemistry from the same sampling time. Respiratory time course: Unknown. Total magnesium is an approximation.
Inputs
Measurement
Value
Unit
pH
7.400
—
PaCO₂
40
mmHg
Sodium
140
mmol/L
Potassium
4
mmol/L
Chloride
104
mmol/L
Lactate
1
mmol/L
Albumin
40
g/L
Phosphate
1
mmol/L
Ionized calcium
1.2
mmol/L
Magnesium
0.8
mmol/L
Lithium
0
mmol/L
Sulfate
0
mmol/L
Calculated values
Measurement
Value
Unit
HCO₃⁻
24.22
mmol/L
SBE
−0.17
mEq/L
SIDa
43.00
mEq/L
SIDe
37.21
mEq/L
SIG
+5.79
mEq/L
Anion gap, no K
11.78
mEq/L
Albumin-corrected AG
11.78
mEq/L
pH 7.400: ph within reference range.
SBE −0.2 mEq/L: within the selected −2.0 to +2.0 mEq/L range. Opposing metabolic effects may still be present.
Default 0–2 mEq/L is a conventional screening range. Use your laboratory’s method-matched interval when available; assays and the total-magnesium approximation can shift SIG. A raised result alone does not establish metabolic acidosis.
AG delta anchor: 8.5 mEq/L. SBE screening cutoff: ±2.0 mEq/L.
Metabolic
Metabolic acidosis — raised lactate
Lactate 12 mmol/L. Respiratory compensation is within the expected range.
pH 7.282PaCO₂ 26 mmHgSBE −13.1 mEq/L
Metabolic acidosis
Incomplete pH correction. Respiratory compensation is within the expected range; pH remains below 7.35.
Arterial sample; chemistry from the same sampling time. Respiratory time course: Acute. Total magnesium is an approximation.
Inputs
Measurement
Value
Unit
pH
7.282
—
PaCO₂
26
mmHg
Sodium
140
mmol/L
Potassium
4
mmol/L
Chloride
105.84
mmol/L
Lactate
12
mmol/L
Albumin
40
g/L
Phosphate
1
mmol/L
Ionized calcium
1.2
mmol/L
Magnesium
0.8
mmol/L
Lithium
0
mmol/L
Sulfate
0
mmol/L
Calculated values
Measurement
Value
Unit
HCO₃⁻
12.00
mmol/L
SBE
−13.14
mEq/L
SIDa
30.16
mEq/L
SIDe
24.37
mEq/L
SIG
+5.79
mEq/L
Anion gap, no K
22.16
mEq/L
Albumin-corrected AG
22.16
mEq/L
Expected PaCO₂: 24.0–28.0 mmHg. Actual: 26.0 mmHg. PaCO₂ is compatible with expected respiratory compensation. Expected PaCO₂ = 1.5 × HCO₃⁻ + 8 ±2 mmHg. Calculated bicarbonate is used here for the empirical compensation check, not as the Stewart cause of acidosis.
pH 7.282: acidaemia.
SBE −13.1 mEq/L: net metabolic acidifying component; selected range −2.0 to +2.0 mEq/L.
PaCO₂ 26.0 mmHg: reduced CO₂. The direction is compensatory.
Default 0–2 mEq/L is a conventional screening range. Use your laboratory’s method-matched interval when available; assays and the total-magnesium approximation can shift SIG. A raised result alone does not establish metabolic acidosis.
AG delta anchor: 8.5 mEq/L. SBE screening cutoff: ±2.0 mEq/L. The ratio can fit a high-gap metabolic acidosis; it does not prove a single process.
Metabolic
Metabolic acidosis — chloride-associated
Chloride is high relative to sodium. Lactate is normal; respiratory compensation is appropriate.
pH 7.317PaCO₂ 32 mmHgSBE −8.9 mEq/L
Metabolic acidosis
Incomplete pH correction. Respiratory compensation is within the expected range; pH remains below 7.35.
Arterial sample; chemistry from the same sampling time. Respiratory time course: Acute. Total magnesium is an approximation.
Inputs
Measurement
Value
Unit
pH
7.317
—
PaCO₂
32
mmHg
Sodium
140
mmol/L
Potassium
4
mmol/L
Chloride
112.65
mmol/L
Lactate
1
mmol/L
Albumin
40
g/L
Phosphate
1
mmol/L
Ionized calcium
1.2
mmol/L
Magnesium
0.8
mmol/L
Lithium
0
mmol/L
Sulfate
0
mmol/L
Calculated values
Measurement
Value
Unit
HCO₃⁻
16.01
mmol/L
SBE
−8.94
mEq/L
SIDa
34.35
mEq/L
SIDe
28.56
mEq/L
SIG
+5.79
mEq/L
Anion gap, no K
11.34
mEq/L
Albumin-corrected AG
11.34
mEq/L
Expected PaCO₂: 30.0–34.0 mmHg. Actual: 32.0 mmHg. PaCO₂ is compatible with expected respiratory compensation. Expected PaCO₂ = 1.5 × HCO₃⁻ + 8 ±2 mmHg. Calculated bicarbonate is used here for the empirical compensation check, not as the Stewart cause of acidosis.
pH 7.317: acidaemia.
SBE −8.9 mEq/L: net metabolic acidifying component; selected range −2.0 to +2.0 mEq/L.
PaCO₂ 32.0 mmHg: reduced CO₂. The direction is compensatory.
Default 0–2 mEq/L is a conventional screening range. Use your laboratory’s method-matched interval when available; assays and the total-magnesium approximation can shift SIG. A raised result alone does not establish metabolic acidosis.
AG delta anchor: 8.5 mEq/L. SBE screening cutoff: ±2.0 mEq/L.
Metabolic
Metabolic acidosis — raised SIG
Raised residual anionic charge with normal lactate.
pH 7.282PaCO₂ 26 mmHgSBE −13.1 mEq/L
Metabolic acidosis
Incomplete pH correction. Respiratory compensation is within the expected range; pH remains below 7.35.
Arterial sample; chemistry from the same sampling time. Respiratory time course: Acute. Total magnesium is an approximation.
Inputs
Measurement
Value
Unit
pH
7.282
—
PaCO₂
26
mmHg
Sodium
140
mmol/L
Potassium
4
mmol/L
Chloride
104
mmol/L
Lactate
1
mmol/L
Albumin
40
g/L
Phosphate
1
mmol/L
Ionized calcium
1.2
mmol/L
Magnesium
0.8
mmol/L
Lithium
0
mmol/L
Sulfate
0
mmol/L
Calculated values
Measurement
Value
Unit
HCO₃⁻
12.00
mmol/L
SBE
−13.14
mEq/L
SIDa
43.00
mEq/L
SIDe
24.37
mEq/L
SIG
+18.63
mEq/L
Anion gap, no K
24.00
mEq/L
Albumin-corrected AG
24.00
mEq/L
Expected PaCO₂: 24.0–28.0 mmHg. Actual: 26.0 mmHg. PaCO₂ is compatible with expected respiratory compensation. Expected PaCO₂ = 1.5 × HCO₃⁻ + 8 ±2 mmHg. Calculated bicarbonate is used here for the empirical compensation check, not as the Stewart cause of acidosis.
pH 7.282: acidaemia.
SBE −13.1 mEq/L: net metabolic acidifying component; selected range −2.0 to +2.0 mEq/L.
PaCO₂ 26.0 mmHg: reduced CO₂. The direction is compensatory.
Default 0–2 mEq/L is a conventional screening range. Use your laboratory’s method-matched interval when available; assays and the total-magnesium approximation can shift SIG. A raised result alone does not establish metabolic acidosis.
AG delta anchor: 8.5 mEq/L. SBE screening cutoff: ±2.0 mEq/L. The ratio can fit a high-gap metabolic acidosis; it does not prove a single process.
Metabolic
Metabolic alkalosis — low chloride
Low chloride relative to sodium, with appropriate respiratory compensation.
pH 7.493PaCO₂ 48 mmHgSBE +12.1 mEq/L
Metabolic alkalosis
Incomplete pH correction. Respiratory compensation is within the expected range; pH remains above 7.45.
Arterial sample; chemistry from the same sampling time. Respiratory time course: Acute. Total magnesium is an approximation.
Inputs
Measurement
Value
Unit
pH
7.493
—
PaCO₂
48
mmHg
Sodium
140
mmol/L
Potassium
3.2
mmol/L
Chloride
91.1
mmol/L
Lactate
1
mmol/L
Albumin
40
g/L
Phosphate
1
mmol/L
Ionized calcium
1.2
mmol/L
Magnesium
0.8
mmol/L
Lithium
0
mmol/L
Sulfate
0
mmol/L
Calculated values
Measurement
Value
Unit
HCO₃⁻
36.01
mmol/L
SBE
+12.06
mEq/L
SIDa
55.10
mEq/L
SIDe
49.48
mEq/L
SIG
+5.62
mEq/L
Anion gap, no K
12.89
mEq/L
Albumin-corrected AG
12.89
mEq/L
Expected PaCO₂: 47.2–49.0 mmHg. Actual: 48.0 mmHg. PaCO₂ is compatible with expected respiratory compensation. Expected PaCO₂ = 40 + (0.6–0.75) × (HCO₃⁻ − 24) mmHg. A further ±2 mmHg screening margin is applied. A PaCO₂ above 55 mmHg usually requires an additional respiratory process; linear rules are less reliable at extremes.
pH 7.493: alkalaemia.
SBE +12.1 mEq/L: net metabolic alkalinising component; selected range −2.0 to +2.0 mEq/L.
PaCO₂ 48.0 mmHg: raised CO₂. The direction is compensatory.
Acidifying and alkalinising metabolic contributions coexist. This alone does not establish separate primary disorders.
Default 0–2 mEq/L is a conventional screening range. Use your laboratory’s method-matched interval when available; assays and the total-magnesium approximation can shift SIG. A raised result alone does not establish metabolic acidosis.
AG delta anchor: 8.5 mEq/L. SBE screening cutoff: ±2.0 mEq/L.
Respiratory
Acute respiratory acidosis
Raised PaCO₂ with the expected acute metabolic response.
pH 7.271PaCO₂ 60 mmHgSBE +0.6 mEq/L
Acute respiratory acidosis
Incomplete pH correction. Metabolic compensation is within the expected range; pH remains below 7.35.
Arterial sample; chemistry from the same sampling time. Respiratory time course: Acute. Total magnesium is an approximation.
Inputs
Measurement
Value
Unit
pH
7.271
—
PaCO₂
60
mmHg
Sodium
140
mmol/L
Potassium
4
mmol/L
Chloride
101.9
mmol/L
Lactate
1
mmol/L
Albumin
40
g/L
Phosphate
1
mmol/L
Ionized calcium
1.2
mmol/L
Magnesium
0.8
mmol/L
Lithium
0
mmol/L
Sulfate
0
mmol/L
Calculated values
Measurement
Value
Unit
HCO₃⁻
27.00
mmol/L
SBE
+0.63
mEq/L
SIDa
45.10
mEq/L
SIDe
39.31
mEq/L
SIG
+5.79
mEq/L
Anion gap, no K
11.10
mEq/L
Albumin-corrected AG
11.10
mEq/L
Acute: 26.0–28.0 mmol/L. Actual: 27.0 mmol/L. Within the expected acute response. Expected HCO₃⁻ change per 10 mmHg PaCO₂ rise: acute +1 to +2; chronic +3 to +4 mmol/L, starting at PaCO₂ 40 and HCO₃⁻ 24. A further ±2 mmol/L screening margin is used before flagging an additional process. This margin is not a validated prediction interval.
pH 7.271: acidaemia.
SBE +0.6 mEq/L: within the selected −2.0 to +2.0 mEq/L range. Opposing metabolic effects may still be present.
PaCO₂ 60.0 mmHg: raised CO₂.
Default 0–2 mEq/L is a conventional screening range. Use your laboratory’s method-matched interval when available; assays and the total-magnesium approximation can shift SIG. A raised result alone does not establish metabolic acidosis.
AG delta anchor: 8.5 mEq/L. SBE screening cutoff: ±2.0 mEq/L.
Arterial sample; chemistry from the same sampling time. Respiratory time course: Chronic. Total magnesium is an approximation.
Inputs
Measurement
Value
Unit
pH
7.345
—
PaCO₂
60
mmHg
Sodium
140
mmol/L
Potassium
4
mmol/L
Chloride
96.5
mmol/L
Lactate
1
mmol/L
Albumin
40
g/L
Phosphate
1
mmol/L
Ionized calcium
1.2
mmol/L
Magnesium
0.8
mmol/L
Lithium
0
mmol/L
Sulfate
0
mmol/L
Calculated values
Measurement
Value
Unit
HCO₃⁻
32.01
mmol/L
SBE
+6.31
mEq/L
SIDa
50.50
mEq/L
SIDe
44.71
mEq/L
SIG
+5.79
mEq/L
Anion gap, no K
11.49
mEq/L
Albumin-corrected AG
11.49
mEq/L
Chronic: 30.0–32.0 mmol/L. Actual: 32.0 mmol/L. Within the expected chronic response. Expected HCO₃⁻ change per 10 mmHg PaCO₂ rise: acute +1 to +2; chronic +3 to +4 mmol/L, starting at PaCO₂ 40 and HCO₃⁻ 24. A further ±2 mmol/L screening margin is used before flagging an additional process. This margin is not a validated prediction interval.
pH 7.345: acidaemia.
SBE +6.3 mEq/L: net metabolic alkalinising component; selected range −2.0 to +2.0 mEq/L. This may be the compensatory response to the respiratory disorder.
PaCO₂ 60.0 mmHg: raised CO₂.
Acidifying and alkalinising metabolic contributions coexist. This alone does not establish separate primary disorders.
Default 0–2 mEq/L is a conventional screening range. Use your laboratory’s method-matched interval when available; assays and the total-magnesium approximation can shift SIG. A raised result alone does not establish metabolic acidosis.
AG delta anchor: 8.5 mEq/L. SBE screening cutoff: ±2.0 mEq/L.
Respiratory
Chronic respiratory acidosis — normal pH
PaCO₂ remains raised. Compensation fits the chronic time course and pH is within range.
pH 7.366PaCO₂ 50 mmHgSBE +2.9 mEq/L
Chronic respiratory acidosis
Complete pH correction. Metabolic compensation is within the expected range; pH is 7.35–7.45.
Arterial sample; chemistry from the same sampling time. Respiratory time course: Chronic. Total magnesium is an approximation.
Inputs
Measurement
Value
Unit
pH
7.366
—
PaCO₂
50
mmHg
Sodium
140
mmol/L
Potassium
4
mmol/L
Chloride
100.4
mmol/L
Lactate
1
mmol/L
Albumin
40
g/L
Phosphate
1
mmol/L
Ionized calcium
1.2
mmol/L
Magnesium
0.8
mmol/L
Lithium
0
mmol/L
Sulfate
0
mmol/L
Calculated values
Measurement
Value
Unit
HCO₃⁻
28.00
mmol/L
SBE
+2.87
mEq/L
SIDa
46.60
mEq/L
SIDe
40.80
mEq/L
SIG
+5.80
mEq/L
Anion gap, no K
11.60
mEq/L
Albumin-corrected AG
11.60
mEq/L
Chronic: 27.0–28.0 mmol/L. Actual: 28.0 mmol/L. Within the expected chronic response. Expected HCO₃⁻ change per 10 mmHg PaCO₂ rise: acute +1 to +2; chronic +3 to +4 mmol/L, starting at PaCO₂ 40 and HCO₃⁻ 24. A further ±2 mmol/L screening margin is used before flagging an additional process. This margin is not a validated prediction interval.
pH 7.366: ph within reference range.
SBE +2.9 mEq/L: net metabolic alkalinising component; selected range −2.0 to +2.0 mEq/L. This may be the compensatory response to the respiratory disorder.
PaCO₂ 50.0 mmHg: raised CO₂.
Default 0–2 mEq/L is a conventional screening range. Use your laboratory’s method-matched interval when available; assays and the total-magnesium approximation can shift SIG. A raised result alone does not establish metabolic acidosis.
AG delta anchor: 8.5 mEq/L. SBE screening cutoff: ±2.0 mEq/L.
Respiratory
Acute respiratory alkalosis
Reduced PaCO₂ with the expected acute metabolic response.
pH 7.483PaCO₂ 30 mmHgSBE −1.1 mEq/L
Acute respiratory alkalosis
Incomplete pH correction. Metabolic compensation is within the expected range; pH remains above 7.45.
Arterial sample; chemistry from the same sampling time. Respiratory time course: Acute. Total magnesium is an approximation.
Inputs
Measurement
Value
Unit
pH
7.483
—
PaCO₂
30
mmHg
Sodium
140
mmol/L
Potassium
4
mmol/L
Chloride
105.8
mmol/L
Lactate
1
mmol/L
Albumin
40
g/L
Phosphate
1
mmol/L
Ionized calcium
1.2
mmol/L
Magnesium
0.8
mmol/L
Lithium
0
mmol/L
Sulfate
0
mmol/L
Calculated values
Measurement
Value
Unit
HCO₃⁻
21.99
mmol/L
SBE
−1.09
mEq/L
SIDa
41.20
mEq/L
SIDe
35.41
mEq/L
SIG
+5.79
mEq/L
Anion gap, no K
12.21
mEq/L
Albumin-corrected AG
12.21
mEq/L
Acute: 22.0–23.0 mmol/L. Actual: 22.0 mmol/L. Within the expected acute response. Expected HCO₃⁻ change per 10 mmHg PaCO₂ fall: acute −1 to −2; chronic −4 to −5 mmol/L, starting at PaCO₂ 40 and HCO₃⁻ 24. A further ±2 mmol/L screening margin is used before flagging an additional process. This margin is not a validated prediction interval.
pH 7.483: alkalaemia.
SBE −1.1 mEq/L: within the selected −2.0 to +2.0 mEq/L range. Opposing metabolic effects may still be present.
PaCO₂ 30.0 mmHg: reduced CO₂.
Default 0–2 mEq/L is a conventional screening range. Use your laboratory’s method-matched interval when available; assays and the total-magnesium approximation can shift SIG. A raised result alone does not establish metabolic acidosis.
AG delta anchor: 8.5 mEq/L. SBE screening cutoff: ±2.0 mEq/L.
Respiratory
Chronic respiratory alkalosis
PaCO₂ remains low. Compensation fits the chronic time course and pH is within range.
pH 7.431PaCO₂ 30 mmHgSBE −4.1 mEq/L
Chronic respiratory alkalosis
Complete pH correction. Metabolic compensation is within the expected range; pH is 7.35–7.45.
Arterial sample; chemistry from the same sampling time. Respiratory time course: Chronic. Total magnesium is an approximation.
Inputs
Measurement
Value
Unit
pH
7.431
—
PaCO₂
30
mmHg
Sodium
140
mmol/L
Potassium
4
mmol/L
Chloride
108.55
mmol/L
Lactate
1
mmol/L
Albumin
40
g/L
Phosphate
1
mmol/L
Ionized calcium
1.2
mmol/L
Magnesium
0.8
mmol/L
Lithium
0
mmol/L
Sulfate
0
mmol/L
Calculated values
Measurement
Value
Unit
HCO₃⁻
19.51
mmol/L
SBE
−4.11
mEq/L
SIDa
38.45
mEq/L
SIDe
32.66
mEq/L
SIG
+5.79
mEq/L
Anion gap, no K
11.94
mEq/L
Albumin-corrected AG
11.94
mEq/L
Chronic: 19.0–20.0 mmol/L. Actual: 19.5 mmol/L. Within the expected chronic response. Expected HCO₃⁻ change per 10 mmHg PaCO₂ fall: acute −1 to −2; chronic −4 to −5 mmol/L, starting at PaCO₂ 40 and HCO₃⁻ 24. A further ±2 mmol/L screening margin is used before flagging an additional process. This margin is not a validated prediction interval.
pH 7.431: ph within reference range.
SBE −4.1 mEq/L: net metabolic acidifying component; selected range −2.0 to +2.0 mEq/L. This may be the compensatory response to the respiratory disorder.
PaCO₂ 30.0 mmHg: reduced CO₂.
Default 0–2 mEq/L is a conventional screening range. Use your laboratory’s method-matched interval when available; assays and the total-magnesium approximation can shift SIG. A raised result alone does not establish metabolic acidosis.
AG delta anchor: 8.5 mEq/L. SBE screening cutoff: ±2.0 mEq/L.
Mixed
Metabolic acidosis + respiratory acidosis
PaCO₂ is higher than expected for the metabolic acidosis.
pH 7.095PaCO₂ 40 mmHgSBE −15.7 mEq/L
Metabolic acidosis + respiratory acidosis
Mixed disorder. PaCO₂ is above expected compensation: additional respiratory acidosis. Compensation alone does not explain the result.
Arterial sample; chemistry from the same sampling time. Respiratory time course: Acute. Total magnesium is an approximation.
Inputs
Measurement
Value
Unit
pH
7.095
—
PaCO₂
40
mmHg
Sodium
140
mmol/L
Potassium
4
mmol/L
Chloride
106.82
mmol/L
Lactate
12
mmol/L
Albumin
40
g/L
Phosphate
1
mmol/L
Ionized calcium
1.2
mmol/L
Magnesium
0.8
mmol/L
Lithium
0
mmol/L
Sulfate
0
mmol/L
Calculated values
Measurement
Value
Unit
HCO₃⁻
12.00
mmol/L
SBE
−15.72
mEq/L
SIDa
29.18
mEq/L
SIDe
23.39
mEq/L
SIG
+5.79
mEq/L
Anion gap, no K
21.18
mEq/L
Albumin-corrected AG
21.18
mEq/L
Expected PaCO₂: 24.0–28.0 mmHg. Actual: 40.0 mmHg. PaCO₂ is above expected compensation: additional respiratory acidosis. Expected PaCO₂ = 1.5 × HCO₃⁻ + 8 ±2 mmHg. Calculated bicarbonate is used here for the empirical compensation check, not as the Stewart cause of acidosis.
pH 7.095: acidaemia.
SBE −15.7 mEq/L: net metabolic acidifying component; selected range −2.0 to +2.0 mEq/L.
Default 0–2 mEq/L is a conventional screening range. Use your laboratory’s method-matched interval when available; assays and the total-magnesium approximation can shift SIG. A raised result alone does not establish metabolic acidosis.
AG delta anchor: 8.5 mEq/L. SBE screening cutoff: ±2.0 mEq/L. The ratio can fit a high-gap metabolic acidosis; it does not prove a single process.
Mixed
Metabolic acidosis + respiratory alkalosis
Raised lactate and negative SBE. PaCO₂ is below Winter’s range despite a normal pH.
pH 7.442PaCO₂ 18 mmHgSBE −10.9 mEq/L
Metabolic acidosis + respiratory alkalosis
Mixed disorder. PaCO₂ is below expected compensation: additional respiratory alkalosis. Compensation alone does not explain the result.
Arterial sample; chemistry from the same sampling time. Respiratory time course: Acute. Total magnesium is an approximation.
Inputs
Measurement
Value
Unit
pH
7.442
—
PaCO₂
18
mmHg
Sodium
140
mmol/L
Potassium
4
mmol/L
Chloride
105
mmol/L
Lactate
12
mmol/L
Albumin
40
g/L
Phosphate
1
mmol/L
Ionized calcium
1.2
mmol/L
Magnesium
0.8
mmol/L
Lithium
0
mmol/L
Sulfate
0
mmol/L
Calculated values
Measurement
Value
Unit
HCO₃⁻
12.01
mmol/L
SBE
−10.93
mEq/L
SIDa
31.00
mEq/L
SIDe
25.21
mEq/L
SIG
+5.79
mEq/L
Anion gap, no K
22.99
mEq/L
Albumin-corrected AG
22.99
mEq/L
Expected PaCO₂: 24.0–28.0 mmHg. Actual: 18.0 mmHg. PaCO₂ is below expected compensation: additional respiratory alkalosis. Expected PaCO₂ = 1.5 × HCO₃⁻ + 8 ±2 mmHg. Calculated bicarbonate is used here for the empirical compensation check, not as the Stewart cause of acidosis.
pH 7.442: ph within reference range.
SBE −10.9 mEq/L: net metabolic acidifying component; selected range −2.0 to +2.0 mEq/L.
PaCO₂ 18.0 mmHg: reduced CO₂.
Default 0–2 mEq/L is a conventional screening range. Use your laboratory’s method-matched interval when available; assays and the total-magnesium approximation can shift SIG. A raised result alone does not establish metabolic acidosis.
AG delta anchor: 8.5 mEq/L. SBE screening cutoff: ±2.0 mEq/L. The ratio can fit a high-gap metabolic acidosis; it does not prove a single process.
Mixed
Metabolic alkalosis + respiratory acidosis
CO₂ retention exceeds compensation for the metabolic alkalosis.
pH 7.396PaCO₂ 60 mmHgSBE +10.7 mEq/L
Metabolic alkalosis + respiratory acidosis
Mixed disorder. PaCO₂ is above 55 mmHg, beyond the compensation ceiling used by this rule. This suggests additional respiratory acidosis; linear estimates are less reliable at extremes. Compensation alone does not explain the result.
Arterial sample; chemistry from the same sampling time. Respiratory time course: Chronic. Total magnesium is an approximation.
Inputs
Measurement
Value
Unit
pH
7.396
—
PaCO₂
60
mmHg
Sodium
140
mmol/L
Potassium
4
mmol/L
Chloride
92.24
mmol/L
Lactate
1
mmol/L
Albumin
40
g/L
Phosphate
1
mmol/L
Ionized calcium
1.2
mmol/L
Magnesium
0.8
mmol/L
Lithium
0
mmol/L
Sulfate
0
mmol/L
Calculated values
Measurement
Value
Unit
HCO₃⁻
36.00
mmol/L
SBE
+10.72
mEq/L
SIDa
54.76
mEq/L
SIDe
48.96
mEq/L
SIG
+5.80
mEq/L
Anion gap, no K
11.76
mEq/L
Albumin-corrected AG
11.76
mEq/L
Expected PaCO₂: 47.2–49.0 mmHg. Actual: 60.0 mmHg. PaCO₂ is above 55 mmHg, beyond the compensation ceiling used by this rule. This suggests additional respiratory acidosis; linear estimates are less reliable at extremes. Expected PaCO₂ = 40 + (0.6–0.75) × (HCO₃⁻ − 24) mmHg. A further ±2 mmHg screening margin is applied. A PaCO₂ above 55 mmHg usually requires an additional respiratory process; linear rules are less reliable at extremes.
pH 7.396: ph within reference range.
SBE +10.7 mEq/L: net metabolic alkalinising component; selected range −2.0 to +2.0 mEq/L.
PaCO₂ 60.0 mmHg: raised CO₂.
Acidifying and alkalinising metabolic contributions coexist. This alone does not establish separate primary disorders.
Default 0–2 mEq/L is a conventional screening range. Use your laboratory’s method-matched interval when available; assays and the total-magnesium approximation can shift SIG. A raised result alone does not establish metabolic acidosis.
AG delta anchor: 8.5 mEq/L. SBE screening cutoff: ±2.0 mEq/L.
Mixed
Metabolic alkalosis + respiratory alkalosis
Positive SBE with PaCO₂ below the expected compensatory range.
pH 7.588PaCO₂ 30 mmHgSBE +5.9 mEq/L
Metabolic alkalosis + respiratory alkalosis
Mixed disorder. PaCO₂ is below expected compensation: additional respiratory alkalosis. Compensation alone does not explain the result.
Arterial sample; chemistry from the same sampling time. Respiratory time course: Acute. Total magnesium is an approximation.
Inputs
Measurement
Value
Unit
pH
7.588
—
PaCO₂
30
mmHg
Sodium
140
mmol/L
Potassium
4
mmol/L
Chloride
99.23
mmol/L
Lactate
1
mmol/L
Albumin
40
g/L
Phosphate
1
mmol/L
Ionized calcium
1.2
mmol/L
Magnesium
0.8
mmol/L
Lithium
0
mmol/L
Sulfate
0
mmol/L
Calculated values
Measurement
Value
Unit
HCO₃⁻
28.01
mmol/L
SBE
+5.94
mEq/L
SIDa
47.77
mEq/L
SIDe
41.98
mEq/L
SIG
+5.79
mEq/L
Anion gap, no K
12.76
mEq/L
Albumin-corrected AG
12.76
mEq/L
Expected PaCO₂: 42.4–43.0 mmHg. Actual: 30.0 mmHg. PaCO₂ is below expected compensation: additional respiratory alkalosis. Expected PaCO₂ = 40 + (0.6–0.75) × (HCO₃⁻ − 24) mmHg. A further ±2 mmHg screening margin is applied. A PaCO₂ above 55 mmHg usually requires an additional respiratory process; linear rules are less reliable at extremes.
pH 7.588: alkalaemia.
SBE +5.9 mEq/L: net metabolic alkalinising component; selected range −2.0 to +2.0 mEq/L.
PaCO₂ 30.0 mmHg: reduced CO₂.
Acidifying and alkalinising metabolic contributions coexist. This alone does not establish separate primary disorders.
Default 0–2 mEq/L is a conventional screening range. Use your laboratory’s method-matched interval when available; assays and the total-magnesium approximation can shift SIG. A raised result alone does not establish metabolic acidosis.
AG delta anchor: 8.5 mEq/L. SBE screening cutoff: ±2.0 mEq/L.
Mixed
Raised lactate and low albumin — normal SBE
Low albumin partly offsets the acidifying effects of chloride and lactate. Net SBE is near zero.
pH 7.400PaCO₂ 40 mmHgSBE −0.2 mEq/L
Opposing metabolic effects; net SBE within the selected range
Not required. pH, PaCO₂ and SBE are within the screening ranges.
Arterial sample; chemistry from the same sampling time. Respiratory time course: Acute. Total magnesium is an approximation.
Inputs
Measurement
Value
Unit
pH
7.400
—
PaCO₂
40
mmHg
Sodium
140
mmol/L
Potassium
4
mmol/L
Chloride
110
mmol/L
Lactate
5
mmol/L
Albumin
20
g/L
Phosphate
1
mmol/L
Ionized calcium
1.2
mmol/L
Magnesium
0.8
mmol/L
Lithium
0
mmol/L
Sulfate
0
mmol/L
Calculated values
Measurement
Value
Unit
HCO₃⁻
24.22
mmol/L
SBE
−0.17
mEq/L
SIDa
33.00
mEq/L
SIDe
31.62
mEq/L
SIG
+1.38
mEq/L
Anion gap, no K
5.78
mEq/L
Albumin-corrected AG
10.78
mEq/L
pH 7.400: ph within reference range.
SBE −0.2 mEq/L: within the selected −2.0 to +2.0 mEq/L range. Opposing metabolic effects may still be present.
Acidifying and alkalinising metabolic contributions coexist. This alone does not establish separate primary disorders.
Default 0–2 mEq/L is a conventional screening range. Use your laboratory’s method-matched interval when available; assays and the total-magnesium approximation can shift SIG. A raised result alone does not establish metabolic acidosis.
AG delta anchor: 8.5 mEq/L. SBE screening cutoff: ±2.0 mEq/L.
Arterial sample; chemistry from the same sampling time. Respiratory time course: Acute. Total magnesium is an approximation.
Inputs
Measurement
Value
Unit
pH
7.442
—
PaCO₂
18
mmHg
Sodium
140
mmol/L
Potassium
4
mmol/L
Chloride
90
mmol/L
Lactate
12
mmol/L
Albumin
40
g/L
Phosphate
1
mmol/L
Ionized calcium
1.2
mmol/L
Magnesium
0.8
mmol/L
Lithium
0
mmol/L
Sulfate
0
mmol/L
Calculated values
Measurement
Value
Unit
HCO₃⁻
12.01
mmol/L
SBE
−10.93
mEq/L
SIDa
46.00
mEq/L
SIDe
25.21
mEq/L
SIG
+20.79
mEq/L
Anion gap, no K
37.99
mEq/L
Albumin-corrected AG
37.99
mEq/L
Expected PaCO₂: 24.0–28.0 mmHg. Actual: 18.0 mmHg. PaCO₂ is below expected compensation: additional respiratory alkalosis. Expected PaCO₂ = 1.5 × HCO₃⁻ + 8 ±2 mmHg. Calculated bicarbonate is used here for the empirical compensation check, not as the Stewart cause of acidosis.
pH 7.442: ph within reference range.
SBE −10.9 mEq/L: net metabolic acidifying component; selected range −2.0 to +2.0 mEq/L.
PaCO₂ 18.0 mmHg: reduced CO₂.
Acidifying and alkalinising metabolic contributions coexist. This alone does not establish separate primary disorders.
Default 0–2 mEq/L is a conventional screening range. Use your laboratory’s method-matched interval when available; assays and the total-magnesium approximation can shift SIG. A raised result alone does not establish metabolic acidosis.
AG delta anchor: 12.0 mEq/L. SBE screening cutoff: ±2.0 mEq/L. An additional metabolic alkalosis or a pre-existing high bicarbonate is suggested.