Clinical Laboratory Review for Toxicology

Objectives List the common lab tests used in the evaluation of poisoned patients Normal values Describe common calculations based on these tests Interpret the findings of common tests

Electrolytes Basic Metabolic Panel Sodium (135-148) Potassium (3.2-5.0) Bicarbonate (22-28) Chloride (95-105) Calcium (8.5-10.5 mg/dl) Other electrolytes Magnesium (1.2-2.0) Phosphorous (2.3-4.3) Units are millieqivilant/L except Ca

Renal function Creatinine (0.8-1.2 mg/dl) Blood Urea Nitrogen (8-18 mg/dl)

Shorthand for Basic Metabolic Panel

Liver function Alananine aminotransferase- ALT SGPT (12-40 IU/L) Aspartate aminotransferase AST SGOT (12-40 IU/L) AST and ALT increase with hepatocyte death Acetaminophen (and most acute toxic causes) produce 10-100 fold elevation while viral/ethanol cause 5-10 fold elevation

Liver function Alkaline phosphatase (39-117) Bilirubin (0.5 to 2.0) Elevation= billiary obstruction Bilirubin (0.5 to 2.0) Measures ability of liver to clear toxins INR (1-1.2) Measures ability of liver to produce coagulation proteins Elevation of transaminsase with change in INR= significant liver injury

Blood gas Shorthand: pH/CO2/O2 pH 7.35 to 7.42 <7.3= acidosis >7.45= alkalosis Partial pressure of CO2 (38-42 torr) <36=respiratory alkalosis >42= respiratory acidosis Low serum bicarbonate= metabolic acidosis High serum bicarbonate= metabolic alkalosis

Anion Gap = Sodium-bicarbonate+ chloride Normal= 10 to 14 meq/L Increase anion gap in the setting of metabolic acidosis consider MUDPILES etc

2xNa+(Glucose/18)+ (BUN/2.8)+ (EtOH/4.6) Osmolar gap Serum osmolality is measured by the lab You estimate serum osmolality from other values 2xNa+(Glucose/18)+ (BUN/2.8)+ (EtOH/4.6) Calculate the difference (“Osmolar Gap”) Measured-estimated (normal<10) If the osmolar gap> 10 suspect toxic alcohol