Math
Spreadsheet arithmetic with fictional blood-pressure and laboratory values
Practice approximate MAP, an anion-gap subtraction and a historical albumin-adjusted calcium calculation, with explicit units and limitations.
Educational arithmetic only; these values do not diagnose a patient
The familiar MAP approximation (SBP+2*DBP)/3 is not a direct measurement and can be less accurate with altered heart rate or waveform. Anion gap here excludes potassium and uses sodium-(chloride+bicarbonate), all in mEq/L. Interpretation depends on the laboratory method, reference interval, albumin and clinical context; a fixed number alone does not diagnose acidosis or adequate perfusion.
The historical adjusted-total-calcium expression totalCa+0.8*(4-albumin) uses calcium in mg/dL and albumin in g/dL. It does not measure ionized calcium or establish that it is normal. Research shows albumin-adjustment formulas can misclassify calcium status. This is a formula-literacy exercise with fictional data, not an ICU decision aid or a substitute for clinician interpretation and appropriate measurement.
| Clinical Panel | Cells & Inputs | Bedside Formula | Arithmetic result; no clinical classification |
|---|---|---|---|
| Blood Pressure (SBP / DBP) | B2 = 120, B3 = 75 mmHg | B3 + (B2 - B3) / 3 | Approximate MAP = 90 mmHg |
| Electrolytes (Na, Cl, HCO3) | B4 = 140, B5 = 102, B6 = 18 | B4 - (B5 + B6) | Anion gap = 20 mEq/L |
| Calcium & Albumin | B7 = 8.2 mg/dL, B8 = 2.5 g/dL | B7 + 0.8 * (4 - B8) | Historical adjusted total Ca = 9.4 mg/dL |
| Hypotensive Case (84 / 48) | SBP = 84, DBP = 48 mmHg | 48 + 36 / 3 | Approximate MAP = 60 mmHg |
Mean Arterial Pressure MAP = ROUND((B2 + 2 * B3) / 3, 1)
Uses fictional positive pressures in mmHg with systolic pressure at least as high as diastolic pressure. No perfusion diagnosis or treatment threshold is attached to the result.
=IF(OR(COUNT(B2:B3)<>2,MIN(B2:B3)<=0,B2<B3),"Invalid inputs",ROUND((B2 + 2 * B3) / 3, 1))Historical albumin-adjusted total calcium arithmetic
Enter total calcium in mg/dL and albumin in g/dL. This historical calculation can be misleading and is not a substitute for ionized calcium assessment when clinically indicated. The separate example check subtracts electrolytes in matching mEq/L units.
=IF(OR(COUNT(B7:B8)<>2,MIN(B7:B8)<=0),"Invalid inputs",ROUND(B7 + 0.8 * (4 - B8), 2))Try the example
Use the original values or change them to test your understanding.