Fluids and electrolytes Terry Irwin MD FRCS Consultant

Fluids and electrolytes Terry Irwin MD FRCS Consultant Colorectal Surgeon

What we will cover § Assessing fluid needs § How to prescribe fluids and electrolytes § Common electrolyte problems

Who has agreed this protocol Surgery Anaesthesia Nephrology Medicine

1/5 intravascular 1/3 Litres extracellular 602/3 tointracellular 70% water = 42 4/5 interstitial

Fluid compartments ICF (mmol/l) ECF (mmol/l) Sodium (Na) 10 145 Potassium (K) 140 4 Calcium (Ca) 3 3 Magnesium (Mg) 50 2 Chloride (Cl) 4 110 Bicarbonate (HCO 3) 10 25 Phosphate (PO 4) 75 2 Protein (g/d. L) 16 5

Fluid compartments ICF (mmol/l) ECF (mmol/l) Sodium (Na) 10 145 Potassium (K) 140 4 Calcium (Ca) 3 3 Magnesium (Mg) 50 2 Chloride (Cl) 4 110 Bicarbonate (HCO 3) 10 25 Phosphate (PO 4) 75 2 Protein (g/d. L) 16 5

Distribution of infused fluids Plasma Interstitial fluid Intracellular fluid

Distribution of infused fluids Plasma Interstitial fluid Colloids Intracellular fluid

Distribution of infused fluids Plasma Interstitial fluid Colloids 0. 9% Na. Cl Intracellular fluid

Distribution of infused fluids Plasma Interstitial fluid Intracellular fluid Colloids 0. 9% Na. Cl 5% Dextrose

Why do we give fluids § Replace lost volume § Maintenance of daily requirements § Replace haemoglobin § Replace blood component § Diluent for drugs § Physical effect

Why do we give fluids § Replace lost volume § Maintenance of daily requirements § Replace haemoglobin § Replace blood component § Diluent for drugs § Physical effect

Daily prescriptions § Water § Sodium § Potassium

How do you decide how much fluid to prescribe?

Fluid volume prescription § Shock § Replacement of any existing deficit § Daily maintenance fluids § Allowance for predicted excess losses

Shock § Fluid bolus (usually 200 ml) § Rapid infusion, not increased rate § Repeat as necessary § Monitor immediate response

Maintenance prescription § Adults 30 mls/kg/day § For children strictly by weight: – 100 mls/kg/day for 1 st 10 kgs – 50 mls/kg/day for the 2 nd 10 kgs – 20 mls/kg/day for the rest

Maximum 2. 5 litres

Maximu m 2 litres

Sodium and Potassium

Sodium § 2 mmols/kg/day § Up to a maximum of 150 mmol/day

Potassium § 1 mmol/kg/day § Usually about 60 mmol per day § Infusion rate important • maximum 10 mmol/hr • maximum 40 mmol in any one bag of fluid

Maintenance fluid calculation 3 0 ml /kg per day

Can your patient drink?

“Usual” daily fluid script ♀ § 1 L N Saline (150 mmols Na) § 1 L 5% dextrose § 60 mmol KCl

Volume Solution Additives Rate Prescribed by 1 1 litre N Saline 20 mmol KCl 84 ml/hr Dr Joe Bloggs 2 1 litre 5% Dextrose 40 mmol KCl 84 ml/hr Dr Joe Bloggs 3 4 5 Administered

. . but what about § Oral intake § Enteral feeding § Paracetamol § IV antibiotics 3 0 ml /kg per day

If she is receiving § 600 mls oral fluids per day § 100 ml paracetamol IV 6 hourly

Volume Solution Additives Rate Prescribed by 1 500 ml N Saline 20 mmol KCl 42 ml/hr Dr Joe Bloggs 2 500 ml 5% Dextrose 40 mmol KCl 42 ml/hr Dr Joe Bloggs 3 4 5 Administered

Volume Solution Additives Rate Prescribed by 1 500 ml N Saline 20 mmol KCl 42 ml/hr Dr Joe Bloggs 2 500 ml 5% Dextrose 40 mmol KCl 42 ml/hr Dr Joe Bloggs 3 4 5 Plus: 400 ml Paracetamol 600 ml oral fluid Total: 2000 ml Administered

Replacing the deficit

§ Symptoms and signs § Fluid balance chart § Urinary output § Biochemistry results § Postural fall in blood pressure § Urine - osmolality (>300), ↓[Na] < 10

Estimating the deficit Severity Symptoms and signs Mild (1 to 2 litres) Mild thirst, dry mouth, normal otherwise Moderate (2 to 4 litres) Thirsty, mild tachycardia, low urinary output, mildly disturbed electrolytes, orthostatic hypotension, slow capillary refill Severe (4 to 6 litres) Dry mucous membranes, pulse >100, low BP, severe oliguria, raised urea and creatinine, veins guttered, peripheries cool Very severe (>6 litres) Sunken eyes, leathery tongue, hypotension, tachycardia >120, anuria, grossly disturbed electrolytes

Replacing the deficit § Estimate the deficit § Choose the most appropriate fluid § Replace over 24 to 36 hours § Monitor response

Excess losses Ongoing losses

Excess losses § Gastric – Vomiting – NG aspiration § Bowel – Diarrhoea – Stoma output § Fistulae

Excess losses § Calculate estimated volume § Replace with same volume of appropriate fluid § Always within the next 24 hour period

What fluid should be used?

Replace with N Saline with potassium as required

Replace with Hartmann’s solution (if potassium OK)

Daily prescriptions § Shock § Deficit § Maintenance § Excessive losses

Daily prescriptions § Shock § Deficit § Maintenance § Excessive losses N Saline /colloid / blood products

Daily prescriptions § Shock § Deficit § Maintenance § Excessive losses N Saline /colloid / blood products N Saline or Hartmann’s

Daily prescriptions § Shock § Deficit N Saline /colloid / blood products N Saline or Hartmann’s § Maintenance N Saline and 5% dextrose § Excessive losses

Daily prescriptions § Shock § Deficit N Saline /colloid / blood products N Saline or Hartmann’s § Maintenance N Saline and 5% dextrose § Excessive losses N Saline or Hartmann’s

Common problems

RIFLE criteria Categor GFR criteria y Urine output Risk Increased creatinine x 1. 5 or GFR decrease > 25% Injury Increased creatinine x 2 or GFR decrease > 50% UO < 0. 5 ml/kg/h x 12 hr Failure Increase creatinine x 3 or GFR decrease > 75% Loss Persistent ARF = complete loss of kidney function > 4 weeks End stage End Stage Kidney Disease (> 3 months) UO < 0. 5 ml/kg/h x 6 hr UO < 0. 3 ml/kg/h x 24 hr or Anuria x 12 hrs

Hyponatraemia

Hyponatraemia Too much water, not too few buildings!

§ Usually caused by XS prescription of water § GAIN guidelines available www. gain-ni. org

Hypokalaemia § Often under-prescription of potassium § May be due to excessive losses

Hyperkalaemia

Summary § Calculate don’t guess § 30 ml fluid/kg/day (maximium 2 to 2. 5 L) § 2 mmol Na+/kg/day (up to 150 mmol/day) § 1 mmol K+/kg/day § Estimate and replace existing deficit § Replace predicted losses § Monitor response