Perioperative fluid management

Question 1

Define insensible losses of fluid

Answer 1

Water loss due to:
Transepidermal diffusion and evaporation
Evaporative water loss from respiratory tract

‘insensible’ as we are not aware of it.

Loss of pure water with no associated solute loss (which occurs in sweating)

Insensible losses cannot be eliminated

Question 2

What is the minimal insensible fluid loss in the average adult?

Answer 2

400ml/d from skin

400ml/d from respiratory tract

Question 3

What can cause insensible fluid loss to vary?

Answer 3

Changes in minute ventilation - e.g. disease and controlled ventilation
Changes with humidity

Question 4

Define sensible losses of fluid

Answer 4

Water loss due to:
Urine
Sweat
Defection
Wounds etc.

‘sensible’ as it can be seen/felt/measured

Loss of water +/- solutes

Can be eliminated

Question 5

What is the primary cation in ICF?

Answer 5

Potassium

Question 6

What is the primary cation in ECF?

Answer 6

Sodium

Question 7

How much sodium is required daily?

Answer 7

1-1.5mmol/kg/day

Question 8

How much potassium is required daily?

Answer 8

0.7-1mmol/kg/day

Question 9

Which patients are more likely to need preoperative fluid resuscitation?

Answer 9

Acute presentations with vomiting or diarrhoea
Acute presentations where patient has been immobile or debilitated prior, causing reduced fluid intake
Elderly patients with impaired renal function
Drugs that impair renal function
Patients with low body weight and total body fluid
Children - may not show obvious physical signs of dehydration

Question 10

What fluids are used for correcting the majority of fluid imbalances?

Answer 10

Isotonic crystalloids:

• Isotonic 0.9% saline*
• Dextrose (4%) saline (0.18%)
• Hartmann’s solution

Question 11

When may non-isotonic fluid optimisation be necessary?

Answer 11

Significant disorders of sodium balance. Likely to require optimisation in high-dependence unit (HDU)

Question 12

How is volume of fluid depletion assessed?

Answer 12

Body weight on admission vs recent when healthy
Haematocrit on admission vs recent when healthy
Serum urea is raised disproportionately more than serum creatinine

Question 13

What are signs of intravascular volume depletion? When are these seen?

Answer 13

Hypotension
Tachycardia
Seen with loss of 10-15% of body water

Question 14

Name 3 symptoms and signs of extracellular fluid depletion

Answer 14

Increased thirst
Drowsiness
Reduced urine output
Headache
Dizziness
Lax skin tone
Reduced sweating
Dry mucosa

Question 15

How is fluid need initially assessed?

Answer 15

ABCDE assessment

Question 16

Name 3 indications for potential fluid resuscitation

Answer 16

SBP <100mmHg
HR >90bpm
Capillary refill >2s
Peripheries cold to touch
RR >20
NEWS 5+
Passive leg raise test

Question 17

What is the initial treatment for fluid resuscitation?

Answer 17

Identify cause of deficit and respond
Give a fluid bolus of 500ml crystalloid over 15min
*Keep Na within 130-154mmol/L

Question 18

What can be given following initial treatment for fluid resuscitation if required?

Answer 18

Further fluid bolus of 250-500ml of crystalloid up to 2000ml before seeking expert help

Question 19

Outline how fluid resuscitation is monitored

Answer 19

Skin turgor and mucosal hydration change slowly - unreliable
1-hourly urine output - target 0.5ml/kg/h
Serum urea provided adequate renal function and no acute GI bleed

Question 20

What are the indications for fluid routine maintenance?

Answer 20

Patient cannot meet fluid and/or electrolyte needs
No complex fluid or electrolyte replacement
No abnormal distribution issues

Question 21

Outline the normal daily fluid and electrolyte requirements for routine fluid maintenance

Answer 21

Water: 25-30 ml/kg/d
Na/K/Cl: 1 mmol/kg/d
Glucose: 50-100 g/d

Question 22

What are the indications for fluid replacement and redistribution?

Answer 22

Patient cannot meet their fluid and/or electrolyte needs
Patient has complex fluid or electrolyte replacement, or
Patient has abnormal distribution issues

Question 23

List 3 causes of abnormal fluid or electrolyte loss

Answer 23

Vomiting and NG tube loss
Biliary drainage loss
High/low volume ileal stoma loss
Diarrhoea/excess colostomy loss
Ongoing blood loss
Sweating/fever/dehydration
Pancreatic/jejunal distula/stoma loss
Urinary loss

Question 24

List 3 types of redistribution or complex fluid issues

Answer 24

Gross oedema
Severe sepsis
Hyper/hyponatraemia
Renal, liver and/or cardiac impairment
Post-op fluid retention and redistribution
Malnourished and refeeding issues