Critical Values: What Are They and Why Do They Exist?
Also known as "panic" values, these are laboratory results that require prompt response by alert lab professionals as they reflect possible life-threateneing conditions, or may progress to irreversible ailments to vital organs. If you get one of these, don't even wait for the lab director to authorize it. Just look up the requesting physician (available on the test requisition form), pick up the phone, and call them ASAP.
It is important to note that cut-off values may differ from one lab to another, and even select tests as well. Here are the essential ones:
Test |
Critical Value(s) |
Rationale |
Glucose |
< 40 mg/dl |
Hypoglycemic cerebral coma |
> 500 mg/dl |
Diabetic dehydration and hyperosmolar coma; Diabetic cerebral coma |
|
Bilirubin (Total) |
> 15 mg/dl (1st week of life) |
Hepatic impairment Excessive hemolysis |
> 20 mg/dl (1st month of life) |
||
Calcium |
< 5 mg/dl |
Rickets and seizures |
> 13 mg/dl |
Renal stones and failure Failure to thrive Muscle weakness |
|
Potassium |
< 2.5 mg/dl |
Heart failure Muscle weakness |
> 6.5 mg/dl |
Heart failure Respiratory failure Paralysis Muscle weakness |
|
Sodium |
< 120 mmol/L |
Cerebral edema and death |
> 160 mmol/L |
Seizures and comatose |
|
Magnesium |
> 2.2 mmol/L |
Paralysis Comatose Hypotension Cardiac arrhythmias Cardiorespiratory arrest |
< 1.3 mmol/L |
Paralysis Seizures Cardiac arrhythmia |
|
Bicarbonate |
< 10 mmol/L |
Coma and death |
Troponin |
> 0.1 ng/ml |
Myocardial infarction (heart attack) |
pH |
< 7.2 |
Coma and death |
> 7.6 |
Seizures Paralysis Cardiac arrhythmia Coma |