1. 4th year Anaesthesia MB ChB
IV Fluids
4th year Anaesthesia
MB ChB

2. The Human Body 60% total body weight (TBW) is water
40% of TBW is intracellular water
20% of TBW is extracellular water (ECF = interstitial and plasma)
5% of TBW is intravascular water i.e. ¼ of the ECF is found in the intravascular compartment as plasma

3. Osmols and tonicity 1 osmole = 1 mole nondissociable substance
Osmolarity = osmoles per liter
Osmolality = osmoles per kg
Tonicity refers to effect on cell volume
Normal plasma osmolarity is mOsm/l

4. Oncotic pressure
Plasma proteins remain intravascular and keep fluid within vessels
Opposed by hydrostatic and interstitial oncotic pressure

5. Goals of perioperative fluids
Maintain fluid volume and electrolytes
Enable adequate renal excretion
Provide energy substrates

6. Surgical stress response Fight or flight
Circulatory changes trauma: haemorrhage, endothelial damage, tissue hypoxia, acidosis and loss of ATP
Endocrine response: activation of SNS with release of adrenaline, cortisol, aldosterone and ADH
Retention sodium and water
Hyperglycaemia
Preferential perfusion brain, heart and muscles

7. Types of Fluids Crystalloids - hypotonic - ± isotonic - hypertonic
5% dextrose
GMS
10% dextrose
Maintelyte
0.45% saline
- ± isotonic
Ringer’s Lactate ()
Plasmalyte L / B (Balsol) ()
0.9% saline ()
- hypertonic
5% saline

8. Colloids - synthetic Starches: Voluven, Venofundin - blood products
Gelatins: Haemacel, Gelofusin
Dextrans
- blood products
Packed red blood cells (RBC’s)
Platelets
Fresh frozen plasma (FFP)
Albumin (SHS: stabilised human serum)

9. Components Water Electrolytes - Na+, K+, Mg2+, Ca2+, Cl-, anions
Glucose
Proteins (synthetic and derived)
Blood components

10. Commonly used IV fluidsNa K Cl
Ca / Mg
Glucose (g/l)
lactate
bicarb
Tonicity (mOsm/l)
5% dextrose 50
Hypo
253
N saline
154
Iso
308
Ringer’s Lactate
131
5.4
111
Ca = 2 29
273
Plas L
107
Mg 3

11. Indications for fluids
Rehydration
Resuscitation
Replace losses
Maintenance fluid balance
Maintain / correct electrolytes
Maintain / correct glucose

12. IV Fluids in theatre Rehydration Maintenance: 1 – 2 ml/kg/hour
Hourly maintenance requirements x hours starved
Don’t need to replace that much fluid though ... WHY?
Increased requirements if high losses
High temperature; nasogastric losses etc
Maintenance: 1 – 2 ml/kg/hour
Replacement of Ongoing Losses
Clear fluids (crystalloid or colloid)
Blood and blood products

13. How much? History Clinical Investigations
Surgical losses – bleeding, exposure and “third space”

14. Too much! Pulmonary oedema Bowel oedema Tissue oedema
Dilutional anaemia and coagulopathy

15. Crystalloids vs Colloids
Expands intravascular space, but
Need 3x volume (3:1)
Physiologically similar to ECF (electrolytes)
Cheap
Long shelf life
Easily transported + stored
No anaphylaxis
Colloid:
No loss of oncotic pressure
Volume for volume replacement (1:1)
Expensive
Anaphylaxis
Coagulation defects
Renal damage

16. Blood & Blood Products

17. Blood bank and its products
Relies on donated blood
Whole blood – in CPD-A
Citrate, phosphate, dextrose and adenine
Packed cells – in SAGM
Sodium, adenine, glucose and mannitol
Platelets, FFP’s, cryoprecipitate
Storage and shelf life differs

18. Safety issues
Correct labelling of blood for X-match and transfusion request
Checking blood
Warming blood
Appropriate giving sets with FILTERS
Patient monitoring
STAT and uncrossed blood

19. Indications for blood transfusion: “transfusion triggers”
GUIDELINES! consider physiology and pathophysiology of each patient as well as intended type of surgery
8 g/dl
<6 – transfuse
<10 g/dl ‘ischaemic cardiac & elderly’
Tolerate lower in chronic anaemia, chronic renal failure
4 ml/kg PRBC’s to increase Hb by 1 g/dl

20. Complications of transfusion
Acute
Hypothermia
Electrolyte changes (esp K)
Acidosis
Incompatibility reactions
Subacute
Infections & Immunosuppression
TRALI (tranfusion related acute lung injury)
Alkalosis

21. Recognition of reaction
Restless, anxious
Nausea & Vomitting
Pain in back, flank or praecordium
Flushing, sweating, tingling, itching
Abnormal bleeding
Pyrexia, rigors
Tachy/bradycardia, hypo/hypertension, clammy peripheries, anaemia
Tachypnoea, bronchospasm
Haemoglobinuria, oliguria
Jaundice
Coma, death

22. Management of transfusion reaction
Stop transfusion
Resuscitate – fluids, oxygen, adrenaline, antihistamines, steroids
FBC, CEU, coag screen and urine
Inform bloodbank ASAP
Return all units of blood with blood and urine samples and reaction report form

23. Massive transfusion >10 units
All the risks of single transfusions multiplied
Hypothermia – need to warm units
Decreased platelets, clotting factors
Acidosis and alkalosis
Hyperkalaemia and later hypokalaemia
Citrate toxicity

24. Blood substitutes Oxygen carrying fluids
Perfluorocarbons – Not currently used
Haemoglobin-based Oxygen carriers e.g. Hemopure® (bovine haemoglobin)

25. Hemopure® Polymerised bovine haemoglobin molecules
Acellular with low viscosity
‘oxygen bridge’
t1/2 life = 12 to 36 hours i.e. need daily infusions
Expensive
Despite being sourced from bovine blood it is apparently acceptable to most Jehovah’s Witnesses