Urea and electrolytes

Resources

Common Patterns of Water and Electrolyte Change in Injury, Surgery and Disease

(Moore, NEJM 1958)Fluid, Electrolyte, and Acid-Base emergencies (Morris,

in Current Diagnosis and Treatment series, 2008)Approach to Fluid and Electrolyte Disorders and Acid-Base Problems

(Palmer, 2008) Oxford Handbook of Clinical Medicine 8e, p678

Normal, abnormal, and Dangerous results

“Normal” range Danger limits Units

Na+ 135 – 145 120 – 155 mmol/L

K+ 3.5 – 5 2.5 – 6.5 mmol/L

Total Ca++ 2.12 – 2.65 mmol/L

Corrected Ca++ 2.0 – 3.5 mmol/L

Glucose 3.5 – 5.5 2.0 – 20 mmol/L

Total Ca++ is measured, but unbound Ca++ is the important factor.Albumin below 40g/L: add 0.1 mmol/L to Ca++ for each 4 g/L albumin drop.

Oxford handbook of clinical medicine, p679

Relative limits

Na+

K+

Corrected Ca++

Glucose

0 50 100 150 200 250 300 350 400 450 500

Steps

1. Sodium relative to osmolarity2. Chloride relative to sodium3. Anion Gap ([Na] – [Cl] – [HCO3]) and pH4. Potassium

Approach to Fluid and Electrolyte Disorders and Acid-Base Problems (Palmer, 2008)

5. Urea, creatinine, urea to creatinine ratio, gfr

Anion GapCations (t = +) Anions (n = negative)

Na+ Cl-

K+ HCO3-

H+ Albumin

Ca++ Lactate

Mg++ Urate

Proteins Phosphate

Sulphate

Ketone bodies

Proteins

Patterns?Tubular damage Addison’s diseaseGlomerular damage Cushing syndromeLactic acidosis Diabetes MellitusKetoacidosis Diabetes InsipidusDehydration Bone disordersGIT upset SIADHDiuretics Other drugs

Oxford handbook of medicine 8e

Kidney patterns

Low GFR Tubular dysfunction

Thiazide and Loop Diuretics

Urea ↑ - ↑

Creatinine ↑ -

Na+ ↓

K+ ↑ ↓ ↑

H+ ↑ ↓

HCO3- ↓ ↑ ↑

Anion Gap ↑

Ca+ ↓

Urate ↑ ↓

Phosphate ↑