Urea and electrolytes

Resources Common Patterns of Water and Electrolyte Change in Injury, Surgery and Disease Common Patterns of Water and Electrolyte Change in Injury, Surgery and Disease (Moore, NEJM 1958) Fluid, Electrolyte, and Acid-Base emergencies Fluid, Electrolyte, and Acid-Base emergencies (Morris, in Current Diagnosis and Treatment series, 2008) Approach to Fluid and Electrolyte Disorders and Acid- Base ProblemsApproach to Fluid and Electrolyte Disorders and Acid- Base Problems (Palmer, 2008) Oxford Handbook of Clinical Medicine 8e, p678

Normal, abnormal, and Dangerous results “Normal” rangeDanger limitsUnits Na+135 – – 155mmol/L K+3.5 – 52.5 – 6.5mmol/L Total Ca – 2.65mmol/L Corrected Ca++2.0 – 3.5mmol/L Glucose3.5 – – 20mmol/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

Steps 1.Sodium relative to osmolarity 2.Chloride relative to sodium 3.Anion Gap ([Na] – [Cl] – [HCO3]) and pH 4. Potassium Approach to Fluid and Electrolyte Disorders and Acid-Base ProblemsApproach to Fluid and Electrolyte Disorders and Acid-Base Problems (Palmer, 2008) 5.Urea, creatinine, urea to creatinine ratio, gfr

Anion Gap Cations (t = +)Anions (n = negative) Na+Cl- K+HCO3- H+Albumin Ca++Lactate Mg++Urate ProteinsPhosphate Sulphate Ketone bodies Proteins

Patterns? Tubular damageAddison’s disease Glomerular damageCushing syndrome Lactic acidosisDiabetes Mellitus KetoacidosisDiabetes Insipidus DehydrationBone disorders GIT upsetSIADH DiureticsOther drugs Oxford handbook of medicine 8e

Kidney patterns Low GFRTubular dysfunction Thiazide and Loop Diuretics Urea↑-↑ Creatinine↑- Na+↓ K+↑↓↑ H+↑↓ HCO3-↓↑↑ Anion Gap↑ Ca+↓ Urate↑↓ Phosphate↑