LessonsReduction of Risk Potential
Laboratory values worth knowing cold
Recall the reference ranges that decide nursing actions, and say which results are reported immediately rather than recorded.
The ranges that change what you do
- Sodium 135 to 145 mEq/L; potassium 3.5 to 5.0; calcium 9.0 to 10.5 mg/dL; magnesium 1.3 to 2.1.
- Glucose 70 to 110 mg/dL fasting; hemoglobin A1c under 5.7 percent normal, and a target usually under 7 in diabetes.
- Hemoglobin roughly 12 to 16 g/dL in women and 14 to 18 in men; platelets 150,000 to 400,000/mm3.
- White cells 5,000 to 10,000/mm3. Creatinine 0.6 to 1.2 mg/dL; BUN 7 to 20.
- INR 2 to 3 on warfarin for most indications; aPTT 1.5 to 2.5 times control on heparin.
Learn them as the numbers that trigger an action rather than as a table. A potassium of 3.2 means the nurse checks the digoxin dose and the diuretic; a platelet count of 40,000 means bleeding precautions start today.
Results that are reported now
A critical value is one where the number itself predicts harm within hours. These are telephoned, read back, and acted on rather than filed.
- Potassium below 2.5 or above 6.5.
- Glucose below 50 or above 400.
- Platelets below 50,000, and certainly below 20,000.
- Hemoglobin below 7 g/dL.
- INR above 5, and any INR with bleeding.
- A positive blood culture, at any hour.
Before a procedure
A few results are checked before specific things happen, and the exam asks about them because each can stop the procedure.
- Platelets and INR before any biopsy, lumbar puncture or invasive line.
- Creatinine before contrast, and metformin withheld around it.
- Potassium before digoxin and before surgery.
- A trough level before the next aminoglycoside or vancomycin dose, with the creatinine beside it.
Worth remembering
- Learn a range as the action it triggers, not as a row in a table.
- A critical value predicts harm within hours; it is telephoned and read back.
- Platelets and INR precede any invasive procedure.
- Creatinine before contrast, and metformin held around it.