Normal Value of Sodium

135 - 145 mEq/L

PANIC value of Sodium

<120 mEq/L or >155 mEq/L

Normal value of Potassium

3.5 - 5.3 mEq/L

PANIC value for Potassium

<2.5 mEq/L or >7.0 mEq/L

Normal value for Magnesium

1.3 - 2.1 mEq/L

PANIC value for Magnesium

<1.0 mEq/L or >5.0 mEq/L

Normal value for Phosphate

2.5 - 4.5 mEq/dl

PANIC value for Phosphate

< 1.0 mg/dl and no high limit

Normal values for Chloride

98 - 113 mEq/L

PANIC value for Chloride

< 70 mEq/L or > 120 mEq/L

Normal value for Calcium

8.6 - 10.0 mg/dl

PANIC value for Calcium

< 6.0 mg/dl or > 13.0 mg/dl

Normal value for Ionized Calcium

(not listed on our objectives, but it was in the lecture)

4.65 - 5.28 mg/dl

PANIC value for Ionized Calcium

(not listed on our objectives, but it was in the lecture)

< 2.0 mg/dl or > 7.0 mg/dl

Normal value for Carbon Dioxide

23 - 30 mmol/L

PANIC values for Carbon Dioxide

< 6.0 mmol/L or > 35 mmol/L

Labs included in Basic Metabolic Panel (Chem 7)

Sodium

Potassium

Chloride

CO₂

BUN

Creatinine

Glucose

Total Calcium

Anion gap

GFR (AA & non-AA)

Labs in Comprehensive Metabolic Panel (Chem 12, CMP)

Everything from Chem 7 PLUS...

Total protein

Albumin

Total bilirubin

AST

ALT

Alkaline phosphate

Calcium

Phosphate (sometimes, could also be in renal function panel)

Labs in Electrolyte Panel

Sodium

Potassium

Chloride

CO₂

Labs ordered separately

Ionized calcium 

Typically ordered separately

Phosphates

Ordered separately or as part of Renal Function Panel

Magnesium

Always ordered separately - NOT in RFP

Factors that can interfere with Sodium lab results

↑ triglycerides will cause artificially low sodium levels

High protein will cause artificially low sodium levels

Varies with circulatory volume

Hemolysis will artificially elevate results

If specimen left for > 4 hours, potassium will leak out of cells and falsely elevate results

Forearm exercise will falsely elevate results

Factors that interfere with Phosphate values

Catastrophic, stressful event may cause high level

Levels are highest in the AM and lowest in the evening

Factors that interfere with Magnesium

Calcium gluconate & other drugs can interfere with testing methods and cause falsely decreased results

Hemolysis will release magnesium into blood & invalidate results (3/4 of body magnesium is located intracellularly)

Prolonged salicylate therapy, lithium, & magnesium products (antacids, laxatives) will falsely increase magnesium leads

Factors that increase Calcium

A decrease in serum albumin results in decrease in serum calcium

Ionized calcium not affected by protein content of blood

Serum Osmolarity Testing Protocol

Patient drinks test load of water (20 ml/kg of body weight within 30 minutes of test)

Each urine sample is checked for volume, osmolality, and specific gravity

Serum sample collected at the end of procedure (use serum or green top heparinized sample)

Test done in recumbent position as response to water-loading is reduced in upright position

Normal values for water-loading ADH suppression test

> 90% of water within 4 hours

Urine osmolality falls to < 100 mOsm/kg

Specific gravity falls to 1.003

Normal urinary: serum ratio (U/S)

0.2 - 4.7

> 93 with overnight dehydration

Normal urine osmolar gap

80 - 100 mOsm/kg/H₂O

Factors that may affect serum osmolarity

Don't ingest alcohol for more than 24 h before the test

Altitude may alter results

There is diurnal variation

Symptoms of Cystic Fibrosis (indicate need to do sweat chloride test)

Failure to thrive in child

Repeated respiratory infections

Meconium ileus

Steatorrhea

Chronic diarrhea

Asthma

Hypoproteinemia

Rectal prolapse

Salty skin

Nasal polyps

Factoids about Sweat Chloride Test

Uses pilocarpine iontophoresis & then analyzes the sweat contents of sodium, chloride, and potassium

Forearm is preferred site, but can use thigh, back, or leg in small baby

MUST obtain at least 100 microliters of sweat

Dehydration & edema may interfere; can't do test before 4-6 weeks old

Sweat Chloride Test procedure

Gauze pads or filter paper with measured amount of pilocarpine is applied to skin

Electrodes are attached which deliver 4-5 miliamps at intervals for 5 minutes

Electrodes are removed and skin is washed

Red area remains and preweighed filter paper or sweat collection cup is applied

Paper is left on for 1 hour and then placed in preweighed flask

ABNORMAL values for Sweat Chloride Test

> 60 mEq/L in children

>80 mEq/L in adolescents and adults

40 - 60 mEq/L should be retested!

Other conditions with elevated sweat chloride levels

Addison's disease

Congenital Adrenal Hyperplasia

Vasopressin resistant diabetes insipidus

Glucose-6 phosphatase deficiency

Glycogen storage disease