IV fluid prescribing in adults

Question 1

2 major groups of fluids

Answer 1

crystalloids
- solutions of small molecules in water (e.g., sodium chloride, Hartmann’s, dextrose)

colloids
- solutions of larger organic molecules (e.g., albumin, Gelofusine)

NB: colloids are used less often than crystalloid solutions as they carry a risk of anaphylaxis and research has shown that cystalloids are superior in initial fluid resuscitation

Question 2

points in the history to consider for the initial assessment of the patient’s fluid and electrolyte needs

Answer 2

fluid intake:
- assess if the patient’s fluid intake has been adequate

symptoms suggestive of dehydration:
- thirst
- dizziness/syncope

fluid loss:
- vomiting (or NG tube loss)
- diarrhoea (inc stoma output)
- polyuria
- fever
- hyperventilation
- increased drain output (e.g., biliary drain, pancreatic drain)

co-morbidities:
- heart failure
- renal failure

Question 3

examination findings suggestive of hypervolaemia

Answer 3

B:
- increased RR (>20 bpm)
- decreased oxygen sats
- bilateral crackles on auscultation

C:
- hypertension
- elevated JVP

E:
- increased urine output
- abdominal distension (ascites) and peripheral oedema
- a fluid chart showing a positive fluid balance
- weight gain

Question 4

examination findings suggestive of hypovolaemia

Answer 4

C:
- increased HR (>90 bpm)
- hypotension (systolic BP < 100 mmHg)
- prolonged CRT
- non-visible JVP

D:
- decreased GCS may be noted if significantly volume depleted

E:
- increased output from wounds and drains
- decreased urine output (<30mls/hr)
- a fluid chart showing a negative fluid balance
- weight loss
- other sources of fluid loss (e.g., rectal bleeding, diarrhoea, vomiting)

Question 5

initial fluid bolus (resuscitation fluids)

Answer 5

500ml bolus of a crystalloid solution (e.g., NaCl 0.9%/Hartmann’s solution) over less than 15 minutes

re-assess the patient
- if ongoing hypovolaemia, give a further 250-500ml bolus of a crystalloid solution then re-assess
- you can repeat up until you’ve given a total of 2000ml of fluid
- if patient has complex medical comorbidities (e..g, HF, renal failure) and/or are elderly, then give 250ml rather than 500ml

Question 6

how to calculate maintenance fluids

Answer 6

daily maintenance fluid requirements:
- 25-30ml/kg/day of water
- 1mmol/kg/day of potassium, sodium and chloride
- 50-100g/day of glucose to limit starvation ketosis

Question 7

factors to consider prior to prescribing maintenance fluids

Answer 7

obese patients
- adjust prescription to ideal body weight
- use the lower range for volume per kg (e.g., 25ml/kg rather than 30ml/kg) as patients rarely need more than 3 of fluid per day

elderly patients
patients with renal impairment
patients with cardiac failure
malnourished patients at risk of refeeding syndrome

Question 8

examples of sources of ongoing fluid or electrolyte loss

Answer 8

• vomiting/NG tube loss
• diarrhoea
• stoma output loss (colostomy, ileostomy)
• biliary drainage loss
• blood loss (e.g., melaena/haematemesis)
• sweating/fever/dehydration (reduced or absent oral intake)
• urinary loss (e.g., diabetes insipidus/post-AKI polyuria)