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

If you would like to get hold of my books, one on Physiology and another on Pathophysiology, check out my web site campbellteaching.co.uk Funds from selling books helps to finance distribution of resources to students in poorer countries.

Vomiting Diarrhoea

Diuretic therapy Alkalosis

Increased aldosterone levels

Effects

Usually asymptomatic Weakness

Atrial and ventricular ectopic beats Cardiac dysrhythmias