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

 

Too much water

Water intoxication

Iatrogenic fluid overload

Fluid overload

May contribute to congestive cardiac failure

Overhydration of cells

Reduced electrolyte concentrations

 

Disease states causing fluid retention

Heart failure

Hypoalbuminaemia

Renal impairment

Hepatic cirrhosis

 

Clinical features

Oedema

Pulmonary oedema

Pleural and pericardial effusion

Ascites

Raised jugular venous pressure

 

Treatments

Underlying cause

Reduce sodium intake

Diuretics

 

Not enough water

Causes

Vomiting and diarrhoea

Burns

Excessive sweating - hot environment, increased work load

Fever

Diabetes insipidus

Osmotic diuresis

Lack of water intake

Diuretic use

 

Features of dehydration

Dry mouth/Thirst

Nausea

Inelastic skin

Muscle cramps

Sunken eyes

Postural hypotension

Peripheral venoconstriction

Increased blood viscosity - sluggish circulation

Impairment in function of many organs ---- confusion ---- coma

Impaired renal function - increased plasma urea

Haemoconcentration - increased plasma sodium

Elevated haematocrit

 

Treatments

Replace that which is lost

Haemorrhage

Burns

Dehydration

 

Treatments in diarrhoea and vomiting

Replace water and electrolytes

Oral rehydration solutions

Water is lost in diarrhoea and vomiting

Potassium and sodium are lost from gastrointestinal secretions

Sodium and glucose is actively taken up by the duodenum

Hypoglycaemia is a problem in diarrhoea and vomiting

 

In emergencies use intravenous infusions

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

Vomiting                                                                     Diarrhoea

Diuretic therapy                                                         Alkalosis

Increased aldosterone levels

 

Effects

Usually asymptomatic                                               Weakness

Atrial and ventricular ectopic beats             Cardiac dysrhythmias

 

Treatment

Treat cause                                                                Diet

Intravenous only when symptomatic or very low serum levels < 2.5 mmol/litre

Replace at less that 20 mmol/hour

 

Never give intravenous bolus potassium

Do not ever give intravenous potassium

 

Hyperkalaemia

Causes

Renal failure                                                   From tissue necrosis after surgery or trauma

Acidosis

 

Effects

Muscle weakness

Changes in potassium may cause cardiac arrest - > 7.0 mmol/L is a medical emergency

Progressive ECG changes - peaked T wave

 

Treatment

10 mls 10% calcium gluconate

Insulin 10 units and 50 mls 50%dextrose

Calcium resonium 15g orally up to 3 times per day with laxatives

Dialysis

 

 

 

 

 

 

 

Oral rehydration solution (WHO)

Sodium                    90            mmol/litre

Potassium                20            mmol/litre

Chloride                   80            mmol/litre

Glucose                   111          mmol/litre

Citrate                      20            mmol/litre

 

 

1 packet of salts dissolved in 1 litre

 

 

1 pinch of salt

1 teaspoon of sugar

1 cup of water

Lemon juice

 

 

Sodium chloride                       3.5g

Sodium bicarbonate                                2.5 g

Potassium chloride                  1.5 g

Glucose                                   20 g

Water                                      1 litre

 

 

 

Diarrhoea

 

Common and serious in children