Intrepretation of laboratory tests

Intrepretation of Laboratory Tests Joseph S Bertino Jr., Pharm.D Bertino Consulting Bertino Consulting www.bertinoconsultng.com Goals and Objectives • Review common laboratory tests – Chemistry – Hematology – Urinalysis – Cerebral Spinal Fluid – Microbiology and Serology • Discuss how pharmacists can use information to assist in drug therapy Bertino Consulting www.bertinoconsultng.com Specimen Types • • • • • • • • Serum: the fluid from blood after blood cells and clot are removed Plasma: fluid from blood centrifuged with anticoagulants Erythrocytes: red blood cells Leukocytes: white blood cells Urine: Random or “clean catch” (for microbiology) Feces Cerebral Spinal Fluid Joint Fluid Bertino Consulting www.bertinoconsultng.com Normal values are specific to a laboratory, I give general normal ranges in this lecture Bertino Consulting www.bertinoconsultng.com Chemistry Bertino Consulting www.bertinoconsultng.com Sodium (Na ) + • Measures amount of serum sodium – Major cation in the blood – Balance depends on intake and renal excretion • • • • Normal: 136 – 146 mmol/L Critical values: < 120 or > 160 mmol/L ↑ Sodium (hypernatremia): ↑ Na+ intake, ↓ Na+ loss, Excessive free water loss ↓ Sodium (hyponatremia): ↓ Na+ intake, ↑ Na+ loss, ↑ free water intake Bertino Consulting www.bertinoconsultng.com Correction of Hypernatremia • Acute hypernatremia – Decrease serum sodium by mmol/L each hour – If patient has normal blood pressure use 0.45% NaCl IV infusion – If patient has low blood pressure use 0.9% NaCl until BP is normal, then 0.45% NaCl IV infusion • Chronic hypernatremia – Decrease serum sodium slowly (0.5 mmol/L each hour) to avoid cerebral edema Bertino Consulting www.bertinoconsultng.com Correction of Hyponatremia • Increase serum sodium by 0.5 mmol/L each hour and 10 mmol/L in 24 hours or 18 mmol/L • • Restrict fluid in 48 hours 3% NaCl should only be used for moderate to severe hyponatremia (very symptomatic) Bertino Consulting www.bertinoconsultng.com Use of 3% NaCl for Hyponatremia • Choose desired correction rate of serum sodium (Example: correct at • Multiply patient’s weight X desired correction rate and infuse as ml/h of • For example in a 60 kg patient: 60 kg X 1.0 mmol/L/h = 60 ml/h infusion of • Correct at no more than 1.0 mmol/hr 1.0 mmol/L/h) 3% NaCl intravenously 3% NaCl Bertino Consulting www.bertinoconsultng.com Potassium (K ) + • Measures serum potassium level – Majority of potassium is in cells (intracellular), not in serum (extracellular) • • Normal potassium value: 3.4 – 5.2 mmol/L • ↓ potassium (hypokalemia): insufficient K+ intake, burns, hyperaldosteronism, Cushing syndrome, renal tubular acidosis, alkalosis, renal artery stenosis Critical potassium value: < 2.5 or > 6.5 mmol/L Bertino Consulting www.bertinoconsultng.com Cerebral Spinal Fluid (CSF) Bertino Consulting www.bertinoconsultng.com Cerebral Spinal Fluid (CSF) Analysis • • Collected via lumbar puncture (LP) Useful for the diagnosis of: – metastatic brain/spinal cord cancer – cerebral hemorrhage – meningitis, encephalitis – degenerative brain disease – autoimmune diseases with brain involvement – neurosyphilis – demyelinating diseases Bertino Consulting www.bertinoconsultng.com CSF analysis Normal Values • • • • • • • • • • Opening pressure: [...]... mass, corticosteroids – Catabolic product of creatine phosphate (from skeletal muscle) – Creatinine is excreted entirely by kidneys → direct measure of renal function – Minimally affected by liver function – Elevation of creatinine occurs slower than BUN Bertino Consulting www.bertinoconsultng.com Calcium • The total serum calcium is a measure of the total of: – Free (ionized) calcium – Protein bound... Bertino Consulting www.bertinoconsultng.com Diagnosing Diabetes • The criteria for the diagnosis of diabetes: – Fasting Plasma Glucose ≥7 mmol/L – 2 hour Post-Prandial (eating) Glucose ≥11.1 mmol/L – Random Plasma Glucose >11.1 mmol/L in the presence of symptoms (increase urine, thirst, hunger) – Any one of these tests should be repeated to confirm diagnosis Bertino Consulting www.bertinoconsultng.com Blood... potassium IV dose 10 mmol/hr, can also give oral K+ at the same time For higher amounts of K+ IV, need to use a central venous line Check Mg+2, if serum Mg+2 low, replace Mg also Bertino Consulting www.bertinoconsultng.com Correction of Hyperkalemia • • • • Stop all potassium and diuretics that prevent renal excretion of potassium • • • Inhaled beta 2 agonists (salbutamol 20 mg inhalation) Insulin + glucose... (dehydration or drugs), renal disease • ↓ BUN: liver failure, overhydration due to SIADH, pregnancy, nephrotic syndrome – Urea nitrogen is end product of protein metabolism (produced in liver) – BUN is an indirect measure of renal function – BUN is a poor measure of liver function – BUN is usually interpreted along with serum creatinine (less accurate than creatinine for measuring renal disease) Critical:... body must maintain equal numbers of cations (+) and anions(-)  The AG measures the excess anions in the blood, a measure of excess acid  AG = Na – Cl – HCO3 (normal AG =12 ± 2)  AG corrected = AG + 2.5 [4 – albumin]  If serum albumin is