1. Fluid and Electrolytes
Prepared by:
Majed Alturkistani
MBBS, FRCPS

2. Objectives Revision of fluid compartments.
Osmotic / Oncotic pressure / osmolality.
Maintenance Fluid Calculation
Deficit Calculation and replacement.
Prescribing fluids.
Es abnormalities

3. Total Body Fluid (compartments)

4. Fluid Compartments

6. Osmotic / Oncotic Pressure

7. Osmolarity Concentration of particles in solution.
The greater the concentration (Osmolarity) of a solution, the greater the pulling force (Osmotic pressure).
Normal serum (blood) osmolarity = mOSM/kg.
A solution that has HIGH osmolarity is one that is > serum osmolarity = HYPERTONIC solution.
A solution that has LOW osmolarity is one that is < serum osmolarity = HYPOTONIC solution.
A solution that has equal osmolarity as serum = ISOTONIC solution.

8. Calculation
Calculated osmolarity = 2 (Na+) + 2 (K+) + Glucose + Urea (all in mmol/L).
OR Calculated osmolarity = 2 (Na+) + Glucose + Urea (all in mmol/L).

9. Fluid balance Total requirement = Maintenance + deficit + ongoing loss
In surgical setting this formula must take into account
pre-operative fasting.
increase losses during surgery.
fluid shift during surgery.
fluid given with blood products.

10. Maintenance Average adult requires approx. 2500 ml water/day. loses: -
200 ml/day GI losses.
800ml/day insensible losses.
1500 ml/day urine. (?renal Failure)
Increase requirements with fever, sweating, GI losses (diarrhea, vomiting, Ng suction), adrenal insuff. hyperventilation.
Decrease requirements with Anuria/Oliguria, CHF.

11. Calculation Fluid Rule to calculate maintenance requirements: -
4 ml/kg/h first 10 kg.
2 ml/kg/h second 10 kg.
1ml/kg/h for remaining weight > 20 kg.

12. Daily Maintenance of Es
Na = 3 mEq/kg.
K = 1 mEq/kg.
Ca = mEq/kg.
Mg = mEq/kg.
Cl Equal to Na.

13. 50 Kg maintenance requirement (Fluid+Es)
Fluid = = 90 ml/h 2160ml/day
Na = 150m Eq/day (therefore 66 mEq/L)
K = 50 mEq/day (therefore 22 mEq/L)

14. Deficit
Patient should be adequately resuscitated prior to anesthesia and surgical procedure.

15. Estimation of deficit

16. IV Fluid
Replacement fluid includes crystalloid,colloid solution and blood.
Synthetic fluid improve perfusion but not Oxygen carrying capacity of blood.
Replacement Ratio 3:1 for Crystalloid and 1:1 For Colloid.

17. Crystalloid
Balanced salt/electrolyte solution; forms a true solution and is capable of passing through semipermeable membranes. May be isotonic, hypertonic, or hypotonic.
E.g. normal Saline (0.9% NaCl), Lactated Ringer’s, Hypertonic saline (3, 5, & 7.5%), Ringer’s solution.
However, hypertonic solutions are considered plasma expanders as they act to increase the circulatory volume via movement of intracellular and interstitial water into the intravascular space.

18. Colloid
High-molecular-weight solutions, draw fluid into intravascular compartment via oncotic pressure (pressure exerted by plasma proteins not capable of passing through membranes on capillary walls). Plasma expanders, as they are composed of macromolecules, and are retained in the intravascular space.
® Albumin, Hetastarch, Pentastarch (Pentaspan ).
Plasma, Dextran.

19. IV Fluid composition

20. IV fluid composition

21. Hypo-volemia (duo to Volume contraction)
Extra-renal Na loss
Vascular e.g. Hemorrhage.
GI e.g. (Vomiting, NG suction, Drainage, Fistula, Diarrhea).
skin e.g. (sweating).
Renal Na loss (Diuretics, Hypoaldoteronism).
Renal free water loss (D.I.)
Hypo-volemia with normal or expanded ECF
Reduce C.O.
Redistribution