tutorial for medical students

1. Fluids and electrolytes in surgery
• Case scenario
• A young male patient, day one post op
laparotomy for perforated peptic ulcer, planed
to stay next 24 hr nil by mouth, he weighted
70 kg, he has NG tube, abdominal drain and
urine cath. Calculate fluid and electrolyte
requirement ?

2. Learning Objectives
• Understand the importance of fluids and
electrolytes in the management of surgical
patient
• Review the normal body composition and
physiology of fluid and electrolytes
• Common pathological changes of fluids and
electrolytes in surgical patients
• Common available IV fluids and electrolytes

3. • Fluid management is a topic that a junior
doctor utilises on a regular basis.
• Because;
• working on a patient who is nil-by-mouth or
• a dehydrated patient or
• a care of the elderly firm
• Significant impact on post-operative
morbidity and the length of hospital stay.

4. • Fluids are prescribed for three reasons
• Resuscitation of deficit
• Maintenance
• Replacement ongoing loss
• correct fluid prescription varies depending on
the individual patient

5. key considerations to remember with
every patient are:
• Aim of giving fluid
(resuscitation, maintenance, or replacemen)?
• What is the weight and size of the patient?
• Are there any co-morbidities e.g HF, CKD
• What is their underlying reason for admission?
• What were their most recent electrolytes?

6. Fluid Compartments
• For adult male
• 2/3rd of total body weight is water (60%)
• 2/3 (40%) of water is intracellular fluid
• 1/3 (20%)nis extracellular fluid
• Female water
• (50%) of total BW
• (33%) IC
• (17%)EC

7. Different fluid for different purposes
• Fluid for maintenance
• Fluid for resuscitation
• Fluid in septic patient

8. Fluid Input-Output

9. Assessment of Fluid Status
patient’s clinical status
• Fluid depleted patients,
• (MM/skin turgor) , thirst?
• Decreasing urine output ( target >0.5 ml/kg/hr)
• Orthostatic hypotension
• In worsening stages:
– Increased capillary refill time
– Tachycardia
– Low blood pressure
• Fluid overloaded, one should be looking for:
• Raised JVP
• Peripheral or sacral oedema
• Pulmonary oedema
• Weight

10. Daily Requirements
• Current NICE guidelines suggest the following:
• Water: 25 mL/kg/day
• Na+: 1.0 mmol/kg/day
• K+: 1.0 mmol/kg/day
• Glucose: 50g/day

11. Intravenous Fluids

13. Fluid Prescribing
• Maintenance Fluids
• these do not have to be replaced exactly but should be targeted, to permit ease of
prescribing
• As an example,
• 70kg healthy male
• fluids over 24 hours 1750mL of water (70kg x 25mL/kg/day) let us say 2000 ml
• 70mmol of Na+ (70kg x 1.0mmol/kg/day)
• 70mmol of K+ (70kg x 1.0mmol/kg/day)
• 50g (50g/day) of glucose
• maintenance regimen is as follows:
• First bag: 500mL of 0.9% saline with 20mmol/L K+ to be run over 8 hours
– This provides all of their Na+, ~1/3rd of their K+, and a quarter of their water
• Second bag: 1L of 5% dextrose with 20mmol/L K+ to run over 8 hours
– This provides a further 1/3rd of their K+, and half of their water, as well as 50gm glucose
• Third bag: 500mL of 5% dextrose with 20mmol/L K+ to run over 8 hours
– This provides the remaining 1/3rd of their K+, and a quarter of their water, as well as 25
gm glucose

14. Correcting a Fluid Deficit
• Given in addition to maintenance through same
IV line or better through a second line
• Calculated subjectively based on Hx and EX, age,
size and comorbidity
• E.g. 70 kg male with Hx of NV over the last 24 hr
• Target urine urine out put >0.5ml/kg/hr
• Fluid challenge 250-500 ml over 15-30 min

15. Replacing Ongoing Losses
• Subjective assessment of excess loss in the 4
secretions also take inconsideration;
• 3rd space loss e.g bowel wall, retroperitoneum in
pancreatitis
• Common scenarios
• Dehydration (high urea:creatinine ratio and high
PCV)
• vomiting (low K+, low Cl–, and alkalosis)
• diarrhoea (low K+ and acidosis)

16. Ongoing Monitoring
• Clinical response
• Fluid chart
• Oral fluid intake amend fluid prescription
• Daily weight
• Blood test U&Es

17. Examples of commonly available fluids
• Crystalloids
• 5% dextrose solution is a hypotonic (and isosmotic)
• What will happen if we infuse
1 liter
• How much will stay in
circulation?
• What will happen to D-isomer?
• Role of infusing 5% dextrose?
• Is there any substantial
calorific or nutritional value?

18. Normal Saline
0.9% sodium chloride solution
isotonic solution , iso osmolar
Advantage
Disadvantage

19. Hartmann’s Solution
• balanced isotonic solution/iso osmolar
contains Na+, Cl–, K+, HCO3
– (as lactate),
Ca2+, and water.
• Advantages
• disadvantages

20. Mixed solutions
• Variable according to
concentrations of G or Na
• Advantages

21. Colloids
• rarely used
• they are solutions containing
complex molecules like
polysaccharides or proteins
with large molecular weights,
aiming to maintain a high
plasma oncotic pressure to
keep fluid within the
intravascular compartment
• Advantages
• disadvantages

22. Quiz
• If a patient receives 1.5L
of 5% dextrose, how
much will remain in the
intravascular
compartment?
A. 100ml
B. 500ml
C. 1L
D. 200ml
• What are the NICE
guidelines for daily
requirements of Na+
and K+ in
mmol/kg/day?
A. Na+: 2, K+: 1
B. Na+: 1, K+: 2
C. Na+: 1, K+: 0.5
D. Na+: 1, K+: 1

23. • Which of these is least
likely to indicate severe
dehydration in a
patient?
A. Increased capillary
refill time
B. Compaining of thirst
C. Tachycardia
D. Orthostatic drop in
blood pressure
• Which of these is not a
cause of concern with
the use of colloids?
A. Increased risk of
coagulopathy
B. Increases risk of intra
cranial bleeding
C. Hypersensitivity
reactions
D. High coast