Fluids and Electrolytes Part 1

Fluid and electrolytes

Fluid regulation
ADH (antidiuretic hormone) - released when water levels are low to increase tubular reabsorption

Electrolyte regulation
Aldosterone - released when serum sodium is low to increase tubular reabsorption.

Water balance
Assess drinking ability in all patients
Fluid balance charts
Insensible loss, 400 mls skin, 400 mls lungs, metabolic water 400mls day
Varies with stress, ambient conditions, fever
Daily weight

Too much water
Increased intake or reduced output
Iatrogenic fluid overload
Big risk in children
Water intoxication, polydipsia

Disease states causing fluid retention
Renal impairment
Heart failure
Hypoalbuminaemia
Hepatic cirrhosis

Clinical features
Polyuria, light colour if normal renal function
Oedema
Pulmonary oedema, orthopnoea
Raised jugular venous pressure
May contribute to congestive cardiac failure
Pleural and pericardial effusion
Ascites
Reduced electrolyte concentrations
Overhydration of cells

Treatments
Underlying cause
Diuretics
Dialysis / haemofiltration
Reduce sodium intake

Not enough water
Causes
Lack of water intake
Vomiting and diarrhoea
Burns
Excessive sweating - hot environment, increased work load
Fever
Diabetes insipidus
Osmotic diuresis
DKA, HONK
Iatrogenic, diuretic use, alcohol

Features of dehydration
Dry mouth/Thirst
Oliguria then anuria, ureamia
Reduced CVP
Tachycardia
Vasoconstriction and pallor
Peripheral venoconstriction
Postural hypotension then hypotnesion
Nausea
Inelastic skin
Sunken eyes
Muscle cramps
Increased blood viscosity - sluggish circulation
Impairment in function of many organs --- confusion --- coma
Haemoconcentration - increased plasma sodium
Elevated haematocrit
Sunken fontanel

Treatments in diarrhoea and vomiting
Replace water and electrolytes
Oral rehydration solutions
Oral or nasogastric fluids
Sodium and glucose is actively taken up by the duodenum
Potassium and sodium are lost from gastrointestinal secretions
Hypoglycaemia is a problem in diarrhoea and vomiting

Other treatments
Haemorrhage
Burns
Dehydration
Intravenous infusions
Crystalloids
Colloids
Blood
Subcutanious infusions, 60 mls / hour
Per rectum administration of fluids may be used by people with low skill levels


Blood volumes 6 months - 500 mls 2 years -1000 mls 5 years - 1.5 litres
10 years - 2 litres 12 years - 2.25 litres


Electrolyte balance

Normal ranges
Potassium, 3.5 - 5 mmol/L Sodium, 135 - 145 mmol/L

Hyponatraemia
Causes
Vomiting Diarrhoea
Excessive sweating Impaired tubular reabsorption
Excessive diuretic therapy Addisons disease
Water excess

Effects
Reduced blood volume
Hypotension
Heat exhaustion, (loss of water and sodium)
Stokers cramp

Treatment
Remove/treat cause Oral sodium
IV. normal saline

Hypernatraemia
Causes
Water deficit - increased loss or reduced intake
Osmotic diuresis
High levels of mineralcorticoids
Cushing`s syndrome

Effects
Thirst Increase in blood volume
Nausea Vomiting
Confusion

Treatment
Treat underlying cause Correct over 48 hours

Hypokalaemia
Causes
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Vomiting Diarrhoea
Diuretic therapy Alkalosis
Increased aldosterone levels

Effects
Usually asymptomatic Weakness
Atrial and ventricular ectopic beats Cardiac dysrhythmias