12.11.30 cPBL

Order of draw

    • Cultures

    • Clotting

    • Chemistry (no additives)

    • EDTA

      • Can give falsely low Ca, Mg

      • Also falsely low Alk-Phos, because it's an Mg-dept.reaction

    • Fluoride-oxylate

Sodium limits

    • Phone for help

      • Less than 125 mM

      • More than 150 mM

    • Life-threatening

      • Less than 115 mM

      • More than 160 mM

    • NB hypernatraemia can be just as dangerous as hyponatraemia

      • 40-50% mortality / 7X mortality increase

      • Although not corrected for co-morbidities

Excreting products of metabolism

    • Require minimum 600 ml of urine to enable excretion, in a healthy adult

      • Can be up to 1200 ml if sick

    • Calculate how much sodium your patient has had!

      • Antibiotics + fluids contribute LOADS of sodium

      • May require up to 4 litres of urine per day to excrete

    • HONK => Need extra water for excretion

    • Make sure you give enough water, or 5% dextrose

      • Even if they're diabetic, give dextrose (not significant in terms of blood glucose)

Causes of polyuria

    • Glucose

    • Hypercalcaemia

    • Hypokalaemia

    • Diabetes insipidus

Hyponatraemia

    • UTI can => Tubule dysfunction => Hyponatraemia

    • Drugs

      • SSRIs

      • Carbemazepine

    • Schizophrenia => Polydipsia ?

    • Some anaesthetics => ADH production

    • Glycine buffer

      • Used for irrigation in prostate, bladder, uterus surgery

        • As it doesn't conduct as well as saline?

      • Can get into blood => Hyponatraemia

    • Pseudohyponatraemia

      • Volume displacement causes raised blood volume and so apparently low sodium

      • But the [Na] in the aqueous phase is actually normal

Hepatorenal syndrome

Notes

    • Renal failure => Hypocalcaemia

      • Failure of vitamin D hydroxylation

      • => High PTH

      • => Renal bone disease

    • Plasma sample

      • Lithium heparin

      • Orange / Green tube

      • Doesn't clot => No risk of potassium release from platelets

    • Be very wary of using half- or twice- normal saline