Electrolytes Disturbances

Sodium Major cation of the ECF

The total body Na – 5000 mmol.

Plasma Na conc. 137 – 147 mmol/l

ICF conc. – 5 mmol/l

Distribution 44% in ECF

47% in bone

9% in ECF.

Sodium

Daily intake – 3 – 5g.(50 –90 mEq ) Normal urinary loss 10 – 90

mEq/day < 1 mEq/ day in conditions of

reduced intake or extra renal loss

Other sources of Na loss

Sweat 10 – 60 mEq/ day

300 mEq in individuals unacclaimatised to hot climates

Intestine 0 – 20 mEq/day

Hyponatraemia

Common causes

1) GI loss e.g. obstruction 2)Inappropriate ADH secretion

GI loss obstruction

H+ ion Paralytic ileus

K+ ion loss Fistulae Diarrhoea

Inappropriate ADH secretion

Oat cell Ca

CNS tumours

Trauma

Hyponatraemia – C. F. Neurological – irritability, lethargy,

c convulsions,

coma

Associated water loss-dehydration

. Investigations

Hct,

plasma proteins,

creatinine,

urea

Investigations Plasma Na low or normal

Urinary Na

< 10mmol/l in extra renal loss,

>20mmol/l in renal loss.

Treatment oral

Isotonic saline

Hypertonic saline

Hypernatraemia

Causes Over infusion of saline

Water loss

Water loss increased sweating

Diabetes insipidus

Hyperadrenalism

Hypernatraemia – C.F.

Facial puffiness, edema, weight gain, CCF, increased osmalality

ICF dehydration

brain - confusion irritability, convulsions coma

Treatment P/O period stop saline,

if due to lack of water, infuse 5% Dextrose

Potassium

ICF cation

Total body K(TBK) = 2500 mmol,

98% ICF – 160 mmol/l,

2% ECF

Plasma K is an important determinant of TBK ,

reduction of 1mmol/l = 200 – 300mmol of TBK

Potassium

Commonest site – skeletal muscle

ECF K- important for neuromuscular function

Acidosis - K out of the cell – hyperkalaemia

Alkalosis - hypokalaemia

Potassium

Daily intake – 50 – 100 mmol

Sources – fruits, milk, honey

K excreted through kidney Renal response to K depletion

slower

Alkalosis - increased renal loss

Acidosis - decreased renal loss

Trauma - increased K excretion

Hypokalaemia

Causes: Loss through the GI excretions –

diarrhoea, fistulas, villous adenomas, ureterosigmoidostomy

Deficient administration – IVfluids

Hyperaldosteronism

Insulin administration

Hypokalaemia . C . F.

Neuromuscular > muscular weakness

Arrhythmias

Ileus

Polyuria

ECG > flattening of T waves, prominent U waves, sagging of ST segment

Treatment oral K,

I/V should not exceed 20 mmols/hour

Hyperkalaemia

Inadequate excretion –

renal

C.F GI symptoms CVS – peaked T, wide T, cardiac

arrest

GI symptoms nausea, vomiting, int. colic, diarrhoea

CVS peaked T,

wide T,

cardiac arrest

Treatment I/V Ca,

combination of HCO3, glucose and insulin,

dialysis

Magnesium

Intracellular divalent cation

Normal serum Mg. – 0.8 to 1.2 mmol/l

Total – 1000 mmols.

Slowly exchangeable

Distribution Bone – 67%,

ICF – 31%,

ECF – 1%

Magnesium

Absorbed

jejunum

ileum

Excretion – kidney. Kidney has remarkable ability to conserve

Function –most of the enzyme systems

Deficiency – along with K & Ca deficiency

Normal daily intake – 10 mmol

Sources – nuts, peas seed gram

Hypomagnesemia

Causes: Malabsorption,

intestinal fistula,

pancreatic insufficiency,

massive bowel resection,

Causes:

biliary diversion,

prolonged N/G suction, hypoparathyroidism, TPN

Severe hypomagnesemia - blocks release of PTH – hypocalcaemia

Increased aldosterone - K loss -hypokalaemia

Hypomagnesemia C. F.

Paraesthesia,

irritability,

mental confusion

Hypocalcaemic features

Hypokalaemic features – arrhythmia etc

Hypermagnesmia in severe renal failure.

Treatment hypokalaemia & hypocalcaemia to

be corrected.

TPN – supplement Mg.

Trace elements

Copper,

Manganese,

Zinc,

Selenium

Trace elements Exact role not defined

Deficiency > rash in TPN patients

Supplementation required in TPN

Replacement of ongoing lossesComposition of GI secretions

401005145500Biliary Fistula

120755140700Pancreatic Fistula

159015601500Gastric Juice (Fasting)

301025101500Saliva

HCO3

(mg mol/l)

Cl(mg mol/l)

K(mg mol/l)

Na (mg mol/l)

Vol (ml)

Locality

Replacement of ongoing lossesComposition of GI secretions

459025120500-15000

DiarrhoealStool

HCO3

(mg mol/l)

Cl(mg mol/l)

K(mg mol/l)

Na (mg mol/l)

Vol (ml)

Locality

30452080300Prox.Colostomy

30458115500Ileostomy