This document discusses fluid and electrolyte balance in surgery. It covers: 1. Total body water distribution, with most being intracellular. Fluid sources and losses are discussed. 2. Electrolytes like sodium, potassium, and calcium are important to maintain balance of. Crystalloid and colloid fluids are compared for volume expansion abilities. 3. Perioperative fluid therapy aims to maintain normovolemia, electrolyte balance, and blood sugar. Fluid types, deficits, and losses are factors to consider for therapy. Guidelines emphasize prompt treatment of hypovolemia and monitoring for adequacy of resuscitation.

1. FLUIDS &
ELECTROLYTE
S IN SURGERY
*** ***
DR. MUGENYA

2. Fluid And Electrolytes
Therapy
 Though fluid and electrolyte therapy can
be a lifesaver, it can also be very harmful.
 Fluid and electrolyte balance is an
extremely complicated thing.
 It requires the understanding of its
composition and distribution in the body.

3. Fluids & Electrolytes
Total body water:
 60% of total body weight in males.
 55% of total body weight in females.
 75% of total body weight in infants.

4. Total Body Water
Total
Body
Water
Intracellula
r 2/3
Extracelul
ar 1/3
Intravascular
1/3
Interstitial
2/3

5. Total Body Water
% Body Weight % Total Body
Water
Body Water 60 100
ICF 40 67
ECF 20 33
--Intravascular 4 8
--Interstitial 16 25

6. Water Sources & Losses
 Sources
o Exogenous 2 – 3 litres per day
o Endogenous ( metabolic water )350 ml/day
 Losses
o Sensible:- urine & faeces(1000 ml/day and
100- 200 ml/day)
o Insensible:- sweat & respiration (500 – 1000
ml/day)
NB: Water input should be = Water output

7. Electrolytes Metabolism
 Na :- Main extracellular cation =>135 -145 mEq/l
oDaily requirements is about 5 gm.
oEquivalent to 5oo ml of isotonic saline 0.9 %
 K :- Main intracellular cation => 3.5 -5.5 mmol/l
oA normal daily intake 1mmol/kg
 Ca:-Normal total serum level is 8.5 -10.5 mg/dl
oNormal ionized serum level is 3.5 -4.5mg/dl
oHypoalbuminemia causes total
hypocalcaemia without affecting the
physiologically active ionized Ca.

8. Perioperative Fluid Therapy
 Aim may include:
 To maintain normovolemia.
 To maintain electrolyte balance
 To maintain normoglycemia

9. Types of Fluids
 Fluids are generally classified as:
1. Crystalloids.
2. Colloids.
 They are jointly referred to as plasma
expanders or volume expanders.
 Fluids can also be classified as:
1. Hypertonic
2. Isotonic
3. Hypotonic

10. Crystalloids
 Aqueous solutions of low molecular weight
ions(salts)
 With or without glucose.
 Sodium is the major osmotically active
particle.
 Crystalloid replacement should be 3 to 6 times
the volume of lost blood.

11. Some Crystalloids
Normal saline(NS).
Lactated Ringer’s solution(LR).
5% dextrose in water (D5W).
Ringer’s acetate.
D5LR.
D5 NS.
D5 ½ NS.
Hypertonic saline(HS)3%.

12. Normal Saline
 Na 154 mEq/L.; Cl 154 mEq/L.; PH 5.7
 Uses: Hyponatreamia.
Brain oedema.
 0.9% NaCl (isotonic) 308 mOsm/L.
 Large quantity may lead to hyperchloremic
metabolic acidosis.
 The predominant effect of volume resuscitation
with crystalloid fluids is to expand the interstitial
fluid volume rather than the plasma volume

13. Lactated Ringer’s (LR)
 Osmolarity 273 mOsm/L
 Na —130 mEq/L
 Cl —109 mEq/L
 K — 4 mEq/L
 Ca — 3 mEq/L
 Lactate —28 mEq/L
 The most physiological solution.
 Lactate is converted into HCO3 in the liver
Ringer’s Acetate
 Acetate —28 mEq/L
 Metabolism 2.5-4 times faster than lactate (in
muscles).

14. Glucose 5% (5% Dextrose)
 It functions as free water.
 50 gm/L isotonic (253 mOsm/L).
 Uses:
 To maintain normoglycemia.
 To correct Hypernatraemia.
 To keep an IV line open for medication.
 Not used for volume expansion => predominant effect is
to expand the intracellular volume (cellular oedema).
 During surgery only given for patients at risk of
hypoglycemia(infants, insulin therapy).
 Avoided in critically ill (increases CO2 production and
aggravates ischemic brain injury).

15. Hypertonic Saline HS 3%
 Osmolarity of1026 mOsm/L.
 Na — 513 mEq/L.
 Cl — 513 mEq/L.
 It expands plasma volume by the
increasing IV oncotic pressure(fluids move
from IC space).
 More effective than crystalloids.
 Uses: -Severe hyponatreamia.
-Early treatment of hypovolaemic
shock.
 Side effects:

16. Colloids
 Solutions containing high-molecular
weight substances such as proteins or
large glucose polymers.
 Plasma is expanded by:
 Volume of colloid.
 Increasing plasma oncotic pressure
which moves fluids from interstitial
space to intravenous spaces.

17. Colloids –vs— Crystalloids
 Colloids stays longer in IV space (3-6 hrs.)
compared to crystalloids (20-30 min.).
 Colloids 3 times potent than crystalloids.
 Severe IV fluid deficits can be more
rapidly corrected using colloids.
 Colloid resuscitation is more expensive.
 Rapid administration of large amounts of
crystalloids (>4-5L) is more frequently
associated with significant tissue edema.

18. Types of Colloids
Sources:
 Blood derived
*Human albumin.
 Synthetic
* Starches.
* Gelatins.
*Dextrans.

19. Human Albumin
 Formulations:
 5% (isotonic) in NS.
 25% (hypertonic) in NS.
 Uses:
 Abnormal protein loss: e.g peritonitis.
 Severe burns.
 Expensive.
 No risk of viral infection.
 Rare allergic reactions.
 No effect on coagulation.

20. Starches
 Examples:
 Hetastarch 6%(Hydroxyethyl Starch ; HES)
 Pentastarch 10% in NS.
More effective than 5% albumin, gelatins
and dextrans.
Non-antigenic => No effect on cross-
matching.
Lower cost than albumin.
Cleared by the kidneys.
 Disadvantages:
 Coagulation abnormalities if >1.5L. is given.
 Rare anaphylactic reactions.
 Elevated serum amylase.

21. Gelatins
 Degraded gelatin polypeptides:
 Examples:
 Haemagel
Relatively cheap.
No effect on coagulation or on cross-
matching.
High incidence of allergic reactions.

22. Dextrans
 Long-chain glucose polysaccharides.
 Dextran 40 and 70 in NS or 5% dextrose.
 Anti-thrombotic effects.
 Dextran 70 is preferred (12hrs.).
 Dextran 40 improves blood flow in
microcirculation.
 Uses:
*Plasma expander.
*To prevent thromboembolism
(postoperative.).

23. …Dextrans
 Disadvantages:
1. Bleeding tendency.
2. Interfere with blood grouping and
cross-matching.
3. Rare anaphylactic reactions.
4. Dextran 40 can precipitate in renal
tubules leading to renal failure.

24. Peri-operative Fluid Therapy
May be required to address the following:
 Compensatory IV volume expansion.
 Normal maintenance requirements.
 Pre-existing deficits.
 Surgical fluid losses:
*Blood.
*Other fluids.

25. Peri-operative Situations
 Factors that need to be considered in the
peri-operative period:
 Patient (age, physiological reserve, pre-op
status)
 Clinical context (magnitude of surgery, blood
loss, etc.)
 Existing deficit
 Stress response - causes salt and water
retention.
 Anticipated losses( Fever, Respiratory rate

26. Compensatory Volume
Expansion
 5-7 ml/kg of crystalloid before anaesthesia.
 This is to compensate for vasodilatation and
cardiac depression by anaesthetic drugs.
 For spinal anaesthesia pre-loading is
mandatory (1 litre in adults)

27. Normal Maintenance
Requirements
The 4 / 2 / 1 rule:
 For the first 10 kg: 4 ml/kg/h.
 For the next 10-20 kg: 2 ml/kg/h.
 For each kg above 20 kg: add 1 ml/kg/h.
Example:
Maintenance fluid needs for a 25 kg child:
40+20+5= 65ml/hour.

28. Postoperative
Requirements to consider:
 Water: as maintenance.
 Potassium: 1 mmol/kg/day.
 Sodium: 1-1.5 mmol/kg/day
 For 70 kg adult:
 2640 ml water
 70-100 mmol Na
 70 mmol K (remember rule of 40)
(Urine output at least40ml/h; Not more than 40 mmol added
to1L drip; Not faster than 40 mmol/hr.)
 Choice of fluids for 70 kg adult:
 2L dextrose 5% => 100gm glucose
 500 ml NS => 75 mmol sodium

29. Preexisting Deficits
 The deficit can be estimated by multiplying
the normal maintenance rate by the length
of the fast.
 70 kg person fasting 8 hr:
 40+20+50 ml/h x 8h =880 ml.
 Consider abnormal losses.

30. Patients Who Are Eating
 Patients who are eating require
“supplemental” fluids (due to inadequate
oral intake):
May require only small amounts of IV
fluid.
 Intravenous potassium replacement is not
usually required (even if hypokalaemic):
Can usually use oral supplementation.

31. …Patients Who Are Eating
 Calculate the amount of water actually
required:
If needs one litre in addition to oral
intake, then give only one litre in a day
(as NS or dextrose solution).
If no other intravenous drug access is
required and intravenous access is
difficult:
o Consider a subcutaneous line (maximum
rate 80 ml/h).

32. Surgical Fluid Losses
Blood loss:
 Continuous monitoring and accurate
estimation of blood loss is very important:
 For each 1 ml loss replace with 3 mls
crystalloids or 1 ml colloids.
Other losses:
 Evaporation from large exposed wounds.
 Third space losses.

33. Guidelines For Fluid Therapy
 Use a short large-bore I.V. cannula.
 The consequences of hypovolemia carry
high mortality and must be treated
promptly.
 Do not give inotropes to hypovolaemic
patient.
 For old, cardiac, hepatic or renal patients,
replace gradually.
Only half calculated deficit is given
initially.

34. …Guidelines For Fluid
Therapy
 Crystalloids, when given in sufficient
amounts are just as effective as colloids:
ie. 3-6 times the volume.
 Severe deficits correct by colloids.
 Rapid large amounts of crystalloids(>5L)
is frequently associated with tissue
edema.
 Monitor clinical markers of perfusion:
Capillary refill time
Urine output

35. …Guidelines For Fluid
Therapy
 Observations (Pulse-BP-CVP)
 CVP if central venous access present (5-12cmH2O)
 Patient thirst
 Response to fluid challenge
 Investigations:
 Electrolytes (Na & K)
 Heamoglobin
 Urine out put more than 0.5ml/kg/h.
 ABG—Arterial blood gas
 CXR

36. Water Depletion
Causes:
 Lack of intake
 Diabetes insipidus
 Increased out put (fever; osmotic diuresis)
C/P:
 Intense thirst & weakness, decreased skin
turgor, oliguria with increased specific gravity.
 Initially increase in serum Na: 3mmol=1L water
deficit
Mx:

37. Water Excess
Causes
 Over infusion of IV 5% glucose in post operative
patients.
 Colorectal washout with plain water before colonic
surgery.
 Excessive uptake of water during TURP.
Findings:
 Moderate:- Asymptomatic; increased urine volume;
increase in body weight; decrease in Na &
haematocrit.
 Marked:- Na <120 meq/L; cerebral oedema, nausea &
vomiting of clear fluid
Mx:
 Mild water excess require fluid restriction
 Severe:- induction of diuresis by Mannitol+careful infusion of 5%

38. Electrolyte Imbalance
HYPONATREAMIA
CAUSES:
 Abnormal GIT losses(suction, vomiting, diarrhea)as in
obstruction of small bowel
 Loss of ECF externally (burns, marked sweating)
 Loss of ECF internally into a third space.
 Excessive urine Na wastage( diuretics, salt wasting
nephritis, adrenal failure)
 Blood loss.
 Decrease intake.
 Addison’s disease.

39. …Electrolyte Imbalance
…HYPONATREAMIA
C/P:
 Eyes sunken & face drawn & skin dry & wrinkled
& tongue dry
 Peripheral veins contracted hypovolaemia
(tachycardia & orthostatic hypotension & shock)
 Low CVP
 Decreased urine output.
Mx :
 NaCl 0.9% infusion.
 Blood loss replaced by blood

40. Hypernatraemia
CAUSES:
 Administration of excessive amount of 0.9%
NaCl post-operatively (Na retention tend to
occur).
 Hyperaldosteronism (Conn’s disease, liver
cirrhosis).
 Cushing syndrome.
C/P: Puffiness of the face is the only early sign:
 Reliable signs are oedema, weight gain,
hypertension.
 Serum Na is usually normal.

41. Hypokalaemia
CAUSES:-
 Excessive vomiting: eg. pyloric stenosis; intestinal
obstruction; paralytic ileus;
 Prolonged GIT aspiration with fluid replacement by IV
NaCl
 External alimentary fistulae
 Diarrhoea & Diuretics as furosemide
 Alkalosis (shift of K intra cellular) & Hyperaldosteronism
C/P:-Mostly asymptomatic; early signs are malaise &
weakness:
:-Paralytic ileus & distention; muscular paresis.
:-ECG prolonged QT; Tachycardia; ST segment

42. Hyperkalaemia
CAUSES
 Life-threatening K excess usually with renal
failure
 Acidosis lead to shift of K out side the cells
C/P:- Arrhythmia, bradycardia, hypotension,
cardiac arrest.
:-ECG wide QRS & peaked T wave.
Mx:- IV Ca gluconate & IV NaHCO3 & glucose,
insulin & if previous fail ion exchange resins
& the end dialysis

43. Calcium Imbalance
HYPOCALCAEMIA
 Latent: As in hypoparathyriodism following thyroid
surgery
 C/P:- Circum-oral tingling, numbness & +ve chvosteks
sign.
 Symptomatic hypocalcaemia: As in permanent
hypoparathyriodism, acute pancreatitis & acute alkalosis
 C/P:- Hyperactive deep tendon reflexes, muscle &
abdominal cramps, carpo-pedal
spasm.
:-ECG prolonged QT interval.
 Mx:- IV Ca gluconate or CaCl2
:- Chronic hypocalcaemia: vit D, oral Ca &
AL(OH)3 bind phosphate in the intestine

44. Metabolic Acidosis
CAUSES
 Over production of organic acid DKA; Lactic
acidosis of sepsis and shock.
 Renal failure(acute-chronic)
 Excessive loss of HCO3(diarrhea; pancreatic or
small intestinal fistula; ureterosigmoidostomy.
C/P:- Increased rate & depth of breathing
Mx:- Mild to moderate treat the cause.
:- Severe: IV HCO3 and treat the cause.

45. Metabolic Alkalosis
PH more than 7.45
CAUSES
 GIT losses of H due to vomiting, suction (pyloric
stenosis)
 Hypokalemia lead to H movement into the
cells(extracellular alkalosis & paradoxical intracellular
acidosis)
 HCO3 retention(NaHCO3 administration, milk alkali
syndrome)
C/P:- Chyne-Stoke respiration & apnea; Tetany.
Mx:- Replacement of Cl:
:-In mild cases saline NaCl is sufficient; associated