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