Electrolytes play a vital role in maintaining homeostasis within the body. They help to regulate heart and neurological function, fluid balance, oxygen delivery, acid–base balance and much more. Electrolyte imbalances can develop by the following mechanisms: excessive ingestion; diminished elimination of an electrolyte; diminished ingestion or excessive elimination of an electrolyte. The most serious electrolyte disturbances involve abnormalities in the levels of sodium, potassium or calcium.

1. Dr. Muhammad Saifullah
HOUSE SURGEON (SU-III)

2. Total Body Water
Intracellular Fluid
Extracellular Fluid

3. constitutes 50-70 % of total body weight
fat contains little water, the lean individual
has a greater proportion of water to total
body weight than the obese person
total body water as a percentage of total
body weight decreases steadily and
significantly with increasing age

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

5. largest proportion in the skeletal muscle
potassium and magnesium are the
principal cations
phosphates and proteins the principal
anions

6. interstitial fluid: two types
functional component (90%) - rapidly equilibrating
nonfunctioning components (10%) - slowly
equilibrating
connective tissue water and transcellular water
called a “third space” or distributional change
sodium is the principal cation
chloride and bicarb the principal anions

7. Water Exchange
Salt Gain & Losses

8. daily water gains
normal individual consumes 2500 mL
water per day
approximately 2000-2200 mL taken by
mouth…half in Solid food!!!
rest is extracted from food as the product
of oxidation, about 300-500 mL

9. daily water losses
60-150 mL in stools, 1500 mL in urine, and 600 mL as
insensible loss
total losses ~ 2.2 liters
Insensible loss: skin (75%) and lungs (25%)
increased by hypermetabolism, hyperventilation, and fever
250 mL/day per degree of fever
unhumidified tracheostomy with hyperventilation =
insensible loss up to 1.5 L/day

10. Minimum of 400 mL urine per 24 hrs
required to excrete the products of
protein catabolism

11. daily salt intake varies 3-5 gm as NaCl
kidneys excretes excess salt: can vary from < 1 to > 200
mEq/day
Volume and composition of various types of
gastrointestinal secretions
Gastrointestinal losses usually are isotonic or slightly
hypotonic
should replace by isotonic salt solution

12. Volume Changes
Concentration Changes
Composition Changes
Potassium Abnormalities
Calcium Abnormalities
Magnesium Abnormalities

13. If isotonic salt solution is added to or lost from
the body fluids, only the volume of the ECF is
changed, ICF is relatively unaffected
If water is added to or lost from the ECF, the conc.
of osmotically active particles changes
Water will pass into the intracellular space until
osmolarity is again equal in the two compartments

14. BUN level rises with an ECF deficit of sufficient
magnitude to reduce GFR
creatinine level may not incr. proportionally in young
people with healthy kidneys
hematocrit increases with an ECF deficit and decreases
with ECF excess
sodium is not reliably related to the volume status of
ECF
a severe volume deficit may exist with a normal,
low, or high serum level

15. ECF volume deficit is most common fluid loss in
surgical patients
most common causes of ECF volume deficit are: GI
losses from vomiting, nasogastric suction,diarrhea,
and fistular drainage
other common causes: soft-tissue injuries and
infections, peritonitis, obstruction,
and burns

16. signs and symptoms of volume deficit:
CNS: sleepy, apathy – stupor, coma
GI: dec food consumption – N/V
CVS: orthostatic, tachy, collapsed veins
- hypotension
Tissue: dec skin turgor, small tongue –
sunken eyes, atonia

17. Iatrogenic or Secondary to renal insufficiency,
cirrhosis, or CHF
signs & symptoms of volume excess:
CNS: none
GI: edema of bowel
CVS: elevated CVP, venous distension –
pulmonary edema
Tissue: pitting edema – anasarca

18. Na+ primarily responsible for ECF osmolarity
Hyponatremia and hypernatremia s&s often occur if
changes are severe or occur rapidly
The concentration of most ions within the ECF can be
altered without significant osmolality change, thus
producing only a compositional change
Example: rise of potassium from 4 to 8 mEq/L would
significantly effect the myocardium, but not the effective
osmotic pressure of the ECF

19. acute symptomatic hyponatremia (< 130)
hypertension can occur & is probably induced by the rise in
intracranial pressure
signs & symptoms:
CNS: twitching, hyperactive reflexes – inc ICP,
convulsions, areflexia
CVS: HTN/brady due to inc ICP
Tissue: salivation, watery diarrhea
Renal: oliguria - anuria

20. Hyponatremia occurs when water is given to replace
losses of sodium-containing fluids or when water
administration consistently exceeds water losses
Hyperglycemia: glucose exerts an osmotic force in the
ECF and causes the transfer of cellular water into the
ECF, resulting in a dilutional hyponatremia

21. The only state in which dry, sticky mucous membranes are
characteristic
sign does not occur with pure ECF deficit alone
signs & symptoms:
CNS: restless, weak - delirium
CVS: tachycardia - hypotension
Tissue: dry/sticky muc membranes – swollen tongue
Renal: oliguria
Metabolic: fever – heat stroke

22. Potassium Abnormalities
Calcium Abnormalities
Magnesium Abnormalities

23. normal daily dietary intake of K+ is approx. 50 to
100 mEq
majority of K+ is excreted in the urine
98% of the potassium in the body is located in ICF
@ 150 mEq/L and it is the major cation of
intracellular water
intracellular K+ is released into the extracellular
space in response to severe injury or surgical stress,
acidosis, and the catabolic state

24. signs & symptoms:
CVS: peaked T waves, widened QRS
complex, and depressed ST segments 
Disappearance of T waves, heart block,
and diastolic cardiac arrest
GI: nausea, vomiting, diarrhea
(hyperfunctional bowel)

25. K+ has an important role in the regulation of acid-base
balance
alkalosis causes increased renal K+/H+ excretion
signs & symptoms:
CVS: flatten T waves, depressed ST segments
GI: paralytic ileus
Muscular: weakness - flaccid paralysis, diminished to
absent tendon reflexes

26. majority of the 1000 to 1200g of calcium in the
average-sized adult is found in the bone
Normal daily intake of calcium is 1 to 3 gm
Most is excreted via the GI tract
half is non-ionized and bound to proteins
ionized portion is responsible for neuromuscular
stability

27. signs & symptoms (serum level < 8):
numbness and tingling of the circumoral region and the
tips of the fingers and toes
hyperactive tendon reflexes, positive Chvostek's sign,
muscle and abdominal cramps, tetany with carpopedal
spasm, convulsions (with severe deficit), and
prolongation of the Q-T interval on the ECG

28. causes:
acute pancreatitis, massive soft-tissue
infections (necrotizing fasciitis), acute
and chronic renal failure, pancreatic
and small-bowel fistulas, and
hypoparathyroidism

29. signs & symptoms:
CNS: easy fatigue, weakness, stupor, and
coma
GI: anorexia, nausea, vomiting, and
weight loss, thirst, polydipsia, and
polyuria

30. two major causes:
hyperparathyroidism and cancer
bone mets
PTH-like peptide in malignancies

31. total body content of magnesium 2000 mEq
about half of which is incorporated in bone
distribution of Mg similar to K+, the major
portion being intracellular
normal daily dietary intake of magnesium is
approximately 240 mg
most is excreted in the feces and the remainder in
the urine

32. causes:
starvation, malabsorption syndromes, GI
losses, prolonged IV or TPN with
magnesium-free solutions
signs & symptoms:
similar to those of calcium deficiency

33. Symptomatic hypermagnesemia, although rare, is
most commonly seen with severe renal insufficiency
signs & symptoms:
CNS: lethargy and weakness with progressive loss of
DTR’s – somnolence, coma, death
CVS: increased P-R interval, widened QRS complex, and
elevated T waves (resemble hyperkalemia) – cardiac
arrest

35. Preoperative Fluid Therapy
Intraoperative Fluid Therapy
Postoperative Fluid Therapy

36. Correction of Volume Changes: Volume deficits result
from external loss of fluids or from an internal
redistribution of ECF into a nonfunctional compartment
 nonfunctional because it is no longer able to participate in the
normal function of the ECF and may just as well have been lost
externally
Correction of Concentration Changes: If severe
symptomatic hypo or hypernatremia complicates the
volume loss, prompt correction of the concentration
abnormality to the extent that symptoms are relieved is
necessary

37. replace losses & supply a maintenance:
open abdomen losses: 8 cc/kg/hr
NGT & urine output
Blood loss x 3
Replace with isotonic salt solution (LR or NS)
unwise to administer potassium during the first 24 h,
until adequate urine output has been established even a
small quantity of potassium may be detrimental
because of fluid shifts

38. Postoperative fluids:
1-Dextrose saline will produce hyponatraemia in a
postoperative patient.
2-Alternate bags of saline and dextrose saline with
supplementary potassium give the best balance.
Fluids distribute into :
1-Colloid(blood, albumin or gelatine solution ) stays in the
vascular compartment.
2-Saline stays in the extracellular compartment.
3-Dextrose eventually goes to all compartment