Management of Fluids and Electrolytes in Surgical Patient

1. Fluids and Electrolytes
Management in Surgical Patient
MANIRABONA Emmanuel, MD, PG-Y2, General Surgery
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2. SCOPE
 Introduction
 Fluid compartments and composition
 Disorders of fluid balance and management
 Disorders of electrolytes and management
 Disorders of acid base balance and management
MANIRABONA Emmanuel, MD, PGY-2, General Surgery Resident 2

3. Introduction
 Fluids and electrolyte management is paramount to the surgical patient.
 Many changes in fluid volume and electrolyte composition can occur:
• Preoperatively
• Intraoperatively
• Postoperatively
• In response to trauma and sepsis
MANIRABONA Emmanuel, MD, PGY-2, General Surgery Resident 3

4. Body fluids
TOTAL BODY WATER (TBW)
• 50-60% of total body weight
• Reflection of body fat
• Skeletal muscles and solid
organs >>> more water than
bone and fat
• Young lean male: 60%
• Lean female: 50%
• Infant: 80%
MANIRABONA Emmanuel, MD, PGY-2, General Surgery Resident
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5. Fluid Compartments
Total body water
3 Functional fluid compartments:
 PLASMA ECF
 INTERSTITIAL FLUID
 INTRACELLULAR FLUID (ICF)
MANIRABONA Emmanuel, MD, PGY-2, General Surgery Resident
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6. Composition of fluid compartments
 ECF : Na+ is the principal cation,
and chloride and bicarbonate are
principal anions
 ICF: principal cations is K+ and
Mg2+, and anions are
Phosphate and sulfate and
proteins
MANIRABONA Emmanuel, MD, PGY-2, General Surgery Resident 6

7.  Concentration gradient is
maintained by Na- K ATPase in
cell membranes
 Water is freely movable between
compartments
 Na+ in ECF remains associated
with water
MANIRABONA Emmanuel, MD, PGY-2, General Surgery Resident 7

8. Serum Osmolality
 Principal determinants of osmolality are : Na+, glucose and urea (BUN)
 Calculated serum osmolality = 2Na + glucose/18 + BUN/2.8
 Normal ECF and ICF osmolality : 290 -310 mOsm/kg
 Any change in osmotic pressure: redistribution of water
 Isotonic change in volume : no net movement of water as long as the ionic
concentration is the same
MANIRABONA Emmanuel, MD, PGY-2, General Surgery Resident 8

9. Normal exchange of fluids
MANIRABONA Emmanuel, MD, PGY-2, General Surgery Resident 9

10. Disorders of body fluids
3 general categories
o Disturbance in volume
o Disturbance in concentration
o Disturbance in composition
MANIRABONA Emmanuel, MD, PGY-2, General Surgery Resident 10

11. Extracellular volume fluid deficit
 Most common disorder in surgical patients: Acute or chronic
 Acute : CVS and CNS signs
 Chronic
 Tissue signs
• Decrease in skin turgor
• Sunken eyes
• +CVS and CNS sings
MANIRABONA Emmanuel, MD, PGY-2, General Surgery Resident 11

12. Volume Disturbance
Labs
 Increase in BUN
 Hemoconcentration : Hb+++
 Increase in urine osmolality
 Urine Na < 20 mEq/L
MANIRABONA Emmanuel, MD, PGY-2, General Surgery Resident 12

13. Causes of volume deficit in surgery
 Loss of GI fluids
• NG tube suctioning
• Vomiting and Diarrhea
• Enterocutaneous fistula
 Sequestration
• Soft tissue injuries and Burns
• Intraabdominal process (peritonitis, obstruction, prolonged surgery)
MANIRABONA Emmanuel, MD, PGY-2, General Surgery Resident 13

14. ECF excess
 Iatrogenic
 2nd to renal dysfunction
 CHF
 Cirrhosis
 Elderly and cardiac patients: very susceptible to fluid excess
MANIRABONA Emmanuel, MD, PGY-2, General Surgery Resident 14

15. FLUID THERAPY
 Fluid therapy in surgical patients is adjusted to each patients needs and
volume status
 Assessing intravascular volume status is pivotal and sometimes difficult.
 It is based on each patient’s:
Volume status (hypervolemic, normovolemic and hypovolemic)
MANIRABONA Emmanuel, MD, PGY-2, General Surgery Resident 15

16. IVF Crystalloids
 Lactated Ringer’s and NS
0.9% are isotonic to
plasma
 Ideal for correcting ECF
volume deficits
 Replacement use 3: 1 rule
MANIRABONA Emmanuel, MD, PGY-2, General Surgery Resident 16

17. IVF Colloids
 High molecular weight
 Confined to the intravascular
space
 Albumin, dextran, hetastarch and
gelatins
 Replacement uses the 1:1 rule
MANIRABONA Emmanuel, MD, PGY-2, General Surgery Resident 17

18. Fluid management
The principle is to replace:
1. Fluid deficit
2. Maintenance fluids
3. Ongoing losses
MANIRABONA Emmanuel, MD, PGY-2, General Surgery Resident 18

19. Preoperative fluid therapy
 Maintenance IV fluids
 For patients who are NPO before surgery
 5% dextrose in 0.45% NS (K can be added in
normal renal function )
 4-2-1 rule
MANIRABONA Emmanuel, MD, PGY-2, General Surgery Resident 19

20. Fluids requirement during surgery
 Calculated per hour during OR:
Fluid deficit (NPO for 6+ hours): 4/2/1
Ongoing fluid requirements: 4/2/1
Replacement of blood loss Crystalloid 3:1, Colloid 1:1
“Third-space” loss uses 4/6/8 rule:
• 4ml/kg/h for minor surgery (hernias, wrist ORIF, breast)
• 6mL/kg for moderate surgery (gyn&obs, ortho, thoracics)
• 8mL/kg for major procedures (GIT surgery, trauma)
MANIRABONA Emmanuel, MD, PGY-2, General Surgery Resident
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21. Postoperative Fluid Therapy
 Based on the patients volume status and ongoing fluid losses
 Correct deficits, replace ongoing losses and give maintenance fluids
 Initial post op period: give an isotonic fluid solution
 After 24-48 hrs: 5% Dextrose 0.45% NS ( with added K)
 Daily assessment of volume status and electrolytes
MANIRABONA Emmanuel, MD, PGY-2, General Surgery Resident 21

22. ELECTROLYTE ABNORMALITIES
HYPONATREMIA: Serum Na < 135 mEq/L
 Dilutional
• High ECF volume
• Excessive oral fluid intake or IVF therapy
• Syndrome of inappropriate ADH
• Drugs: antipsychotics, tricyclic antidepressantants, ACEI
MANIRABONA Emmanuel, MD, PGY-2, General Surgery Resident 22

23.  Depletional:
• Decreased intake: low sodium diet
• GI losses from vomiting
• Prolonged nasogastric tube suctioning
• Diarrhea
• Diuretic use or primary renal disease
MANIRABONA Emmanuel, MD, PGY-2, General Surgery Resident 23

24. Manifestation of Hyponatremia
MANIRABONA Emmanuel, MD, PGY-2, General Surgery Resident 24

25. Hyponatremia Management
 Most cases can be treated with water restriction
 Severe cases need Na administration
 Symptomatic at levels < 120 mEq/L
 Neurologic symptoms: give 3% NS ( correct Na at a rate < 1mEq/l, until
130mEq/l)
 Rapid correct can lead to Central Pontine myelinolysis
MANIRABONA Emmanuel, MD, PGY-2, General Surgery Resident 25

26. Hypernatremia
 Na > 145mEq/L
 Loss of free water or gain of Na
 Hypervolemic hypernatremia
• Iatrogenic ( Na containing fluids)
• NaHCO3
• Mineralocorticoid excess (hyperaldosteronism, Cushing syndrome)
MANIRABONA Emmanuel, MD, PGY-2, General Surgery Resident 26

27. Hypernatremia
 Normovolemic hypernatremia
• Diabetic insipidus
• Diuretic use and Renal disease
• GI losses, skin losses
 Hypovolemic hypernatremia
• GI losses- diarrhea
• Fever and hyperventilation
MANIRABONA Emmanuel, MD, PGY-2, General Surgery Resident 27

28. Manifestation of Hypernatremia
MANIRABONA Emmanuel, MD, PGY-2, General Surgery Resident 28

29. Management of Hypernatremia
 First, assess the volume status
 Treat hypovolemia with isotonic fluids
 Once volume is restored replace water deficit with a hypotonic solution :
dextrose 5%, ¼ NS 5% Dextrose
 Slowly correct Na levels at a rate < 1mEq/h and 12 mEq/d (< 0.7 mEq/h
in chronic hypernatremia)
 This is to prevent cerebral edema
MANIRABONA Emmanuel, MD, PGY-2, General Surgery Resident 29

30. POTASSIUM
 K+ is critical to cardiac and neuromuscular function
 Factors that influence K+ distribution in ICF and ECF
• Surgical stress
• Injury
• Acidosis
• Tissue metabolism
 Normal serum K+: 3.5- 5.0 mEq/L
MANIRABONA Emmanuel, MD, PGY-2, General Surgery Resident 30

31. HYPERKALEMIA
 Serum level > 5.5 mmol/L
 Excessive potassium intake
 Increased release from cells
 Impaired excretion
MANIRABONA Emmanuel, MD, PGY-2, General Surgery Resident 31

32. Cont.…
 GI: nausea, vomiting, intestinal
colic, diarrhea
 Neuromuscular: weakness,
ascending paralysis, respiratory
failure
MANIRABONA Emmanuel, MD, PGY-2, General Surgery Resident 32

33. Management of Hyperkalemia
MANIRABONA Emmanuel, MD, PGY-2, General Surgery Resident 33

34. HYPOKALEMIA : Etiologies , S&S
MANIRABONA Emmanuel, MD, PGY-2, General Surgery Resident 34

35. Management of Hypokalemia
• Check Magnesium level first
• Asymptomatic patient with K > 3.0
mEq/L, oral K replacement may be
sufficient.
• Rate of IV infusion should not exceed
40 mEq/hr
• May cause a burning sensation if
given in peripheral IV.
• Low flow rate of 10 mEq/hr or add
small amount of lidocaine to the
solution can decrease discomfort
MANIRABONA Emmanuel, MD, PGY-2, General Surgery Resident
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36. HYPERCALCEMIA
 Normal total serum calcium : 8.5-
10.5 mg /dl
 Ionized calcium > 4.2- 4.8 mg/dl
 Causes
• Primary hyperparathyroidism ( 90%
of patients)
• Malignancy: bone metastasis, tumor
secreting PTH
 Anorexia, nausea and vomiting,
abdominal pain
 Weakness, confusion, coma, bone
pain
 Hypertension, arrhythmias,
polyuria, polydipsia
MANIRABONA Emmanuel, MD, PGY-2, General Surgery Resident 36

37. Management of Hypercalcemia
 Definitive management is the correction of the primary cause
 Correct volume deficits with IVF like NS followed by a loop diuretic
 In case of renal failure: hemodialysis
 Biphosphonates : reduce osteoclast mediated release of calcium. (bone
metastasis)
 Exogenous calcitonin; can be used in short term treatment but not
helpful in the long term
MANIRABONA Emmanuel, MD, PGY-2, General Surgery Resident 37

38. HYPOCALCEMIA
 Total calcium < 8.5 mEq/L or Ionized calcium < 4.2 mg/dl
Etiologies
o Pancreatitis, Necrotizing fasciitis, Tumor lysis syndrome
o Renal failure, Hypoparathyroidism
o Post parathyroid or thyroid surgery
• Occurs in 1-2% after total thyroidectomy
o Malignant related osteoblastic activity
MANIRABONA Emmanuel, MD, PGY-2, General Surgery Resident 38

39. Manifestation of Hypocalcemia
 Symptoms start with ionic fraction < 2.5 mg/dl
 Paresthesia of face and extremities ,Muscle cramps
 Carpopedal spasm, tetany, seizures, Hyperreflexia
 Chvostek’s sign: spasm from tapping over the facial nerve
 Trousseau sign: Carpal spam after inflating the BP cuff
 Decreased cardiac contractility, heart failure
MANIRABONA Emmanuel, MD, PGY-2, General Surgery Resident 39

40. Management of Hypocalcemia
 Repletion can be given oral or IV
 Oral calcium carbonate suspension 1250 mg/5ml q6 hours
 IV Calcium gluconate 2g IV over 1hr
 Recheck levels after 3 days
 Correct associated Magnesium, potassium and phosphate abnormalities
MANIRABONA Emmanuel, MD, PGY-2, General Surgery Resident 40

41. HYPERMAGNESEMIA
 Normal plasma Mg: 1.5-2.0 mEq/L
 Causes Of hypermagnesemia
• Severe renal insufficiency
• Magnesium containing antacids and laxatives
 S&S
• Nausea and vomiting
• Weakness, lethargy, hyporeflexia
• Hypotension, cardiac arrest
MANIRABONA Emmanuel, MD, PGY-2, General Surgery Resident 41

42. Management of Hypermagnesemia
 Eliminate exogenous sources
 Correct volume deficits
 Correct acidosis
 Acute symptoms: calcium chloride 5-10 ml immediately to antagonize
CVS effects
 Hemodialysis: if levels and symptoms persist
MANIRABONA Emmanuel, MD, PGY-2, General Surgery Resident 42

43. HYPOMAGNESEMIA
 Common in hospitalized patients and critically ill
 Alteration of intake
Starvation, alcoholism, prolonged IVF therapy
 Increased renal excretion
Alcohol abuse, diuretic use, amphotericin B, primary aldosteronism
,diarrhea, malabsorption, acute pancreatitis
MANIRABONA Emmanuel, MD, PGY-2, General Surgery Resident 43

44. Manifestation of Hypomagnesemia
 S&S
• Hyperactive reflexes
• Muscles tremors, tetany
• Positive Chvostek's and trousseau signs
• Delirium and seizures
 Hypomagnesemia can lead to hypocalcemia, persistent hypokalemia
 When they coexist, prompt correction of Mg2+ , to restore the other
electrolytes
MANIRABONA Emmanuel, MD, PGY-2, General Surgery Resident
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45. Management of Hypomagnesemia
 Mg level 1.0 -1.8 mEq/L
• Magnesium sulfate 0.5 mEq/L in NS 250 ml infused over 24 hr for 3
days
 Mg < 1.0 mEq/L
• Magnesium sulfate 1 mEq/l in NS 250 ml iv over 24 hr for 1 day, then
0.5 mEq/l in NS 250 ml over 24 hr for 2 days
o Asymptomatic and mild
• Oral: milk of magnesia 15 ml ( 49mEq/l ) q 24hours and hold if
diarrhea
MANIRABONA Emmanuel, MD, PGY-2, General Surgery Resident
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46. REFERENCES
1. Fluid and Electrolyte Management of
the surgical patient, in Schwartzs
Principles of Surgery, 10th Ed, chap 3,
p65-81
2. Shock, Electrolytes and Fluids, in
Sabiston Texbook of Surgery, 19th Ed,
chap 5
3. Managing physiologic changes in
the surgical patient, in Essential
Surgery 5TH Ed, p 19-32
4. G P Joshi, Intraoperative fluid
management. Available on
UPTODATE.
5.N. Siparsky, Overview of
Postoperative fluid therapy in
adults. Available on UPTODATE.
6.Fluid, Electrolyte and Acid Base
Balance in Elaine N. Marieb,
Human Anatomy and Physiology,
7th Ed, chap 26
MANIRABONA Emmanuel, MD, PGY-2, General Surgery Resident 46