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Fluids and Electrolytes

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Standard II - Formulate a patient-specific plan for anesthesia care ... Trousseau's sign. Dysrhythmias. Prolonged QT interval. Treatment of Hypocalcemia ... – PowerPoint PPT presentation

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Title: Fluids and Electrolytes


1
Fluids and Electrolytes
2
Water is the most abundant compound in the body
and is the major solvent in which metabolism
occurs.
3
During an anesthetic, the anesthetist has primary
responsibility for the airway and the fluid
status of the patient.
4
AANA Standards for Care
  • Standard I - Thorough preoperative evaluation
  • Standard II - Formulate a patient-specific plan
    for anesthesia care
  • Standard III - Implement and adjust the plan
    based on the patients physiologic response.

5
Agenda
  • Body fluid compartments
  • Electrolyte imbalances
  • Types of fluids
  • Fluid loss during surgery
  • Developing a fluid plan
  • Complications of fluid therapy

6
Body Fluid Compartments and Composition
7
Total Body Water
  • 80 water in newborn
  • Maximal at birth
  • Adults - 60-70 water
  • Obese - Lower percentage
  • Lean - Higher percentage

8
Rule of Approximate Thirds
  • 2/3 of body weight is water (lean person)
  • Body water
  • 2/3 intracellular
  • 1/3 extracellular
  • Extracellular water
  • 2/3-3/4 extravascular
  • 1/3-1/4 intravascular

9
70 kg Patient
  • Total body water - 42 L
  • Intracellular - 28 L
  • Extracellular - 14 L
  • Intravascular - 3 L
  • Interstitial - 11 L

10
Fluid Dynamics
  • Forces affecting movement of fluids
  • Capillary hydrostatic pressure
  • Interstitial fluid pressure
  • Plasma colloid osmotic pressure (oncotic)
  • Interstitial fluid colloid pressure

11
Capillary Hydrostatic Pressure
  • Tends to move fluid out of the capillaries
  • Arterial end - 25 mm/Hg
  • Venous end - 10 mm/Hg
  • Increasing hydrostatic pressure moves fluids to
    interstitial spaces.

12
Edema occurs when fluid moves into interstitial
spaces faster than it can be drained by the
lymphatic system.
13
Why is edema harmful?
  • Edema increases the distance between the cells
    and the capillaries which reduces the
    effectiveness of meeting metabolic needs.

14
Factors Increasing Hydrostatic Pressure
  • Hypervolemia
  • Decreased renal function
  • Cardiac failure

15
Plasma Osmotic Pressure
  • Draws fluid from interstitial space back to the
    capillaries
  • Colloid osmotic pressure is generated by protein
    molecules
  • Donnan equilibrium enhances the osmotic effect

16
Donnan Equilibrium
  • Causes COP to be about 50 greater than that
    caused by proteins alone
  • Proteins carry a negative charge
  • Attract a large number of cations
  • Water follows sodium

17
Colloid Osmotic Pressure
  • Combination of oncotic and osmotic pressures
  • Oncotic pressure - from proteins
  • Osmotic pressure - from electrolytes
  • Normal osmolality 285 mOsm/kg (about twice the
    Na value)

18
Interstitial Fluid Colloid Osmotic Pressure
  • From small protein concentration in the
    interstitial fluid
  • Most capillary pores are smaller than proteins,
    but some leak
  • Interstitial osmotic pressure 8 mm/Hg

19
Review forces causing capillary fluid movement
  • McIntosh Table 11-1 p.192

20
Normal Equilibrium
  • Slightly more fluid leaves the capillaries than
    returns
  • Excess fluid is returned via the lymphatic system

21
Fluid Volume Problems
  • Hypovolemia
  • Hypervolemia

22
Hypovolemia
  • Volume defecit in ECF or circulating blood volume
  • May be absolute or relative
  • Actual fluid loss
  • Shift to different compartment

23
Causes of Fluid Loss
  • Gastrointestinal loss
  • Fever
  • Blood loss
  • Burns
  • Peritonitis
  • Fluid shifts
  • Diuretics
  • Inhalation of dry gases

24
Signs of Hypovolemia
  • Tachycardia
  • Orthostatic hypotension
  • Flat neck veins when supine
  • Decreased CVP
  • Decreased urine output
  • Dry membranes
  • CV collapse

25
Compensatory Mechanisms
  • Vaso constriction
  • Tachycardia
  • Note The patient under general anesthesia is
    unable to compensate. Therefore, fluid
    management is even more critical.

26
Hypervolemia
  • Fluid admisistration exceeds actual need
  • May be caused by
  • Large IV fluid volume
  • CHF
  • Renal failure
  • Long term steroid use
  • Cushings Syndrome

27
Signs of Hypervolemia
  • Destended neck veins
  • Peripheral edema
  • Dyspnea
  • Pulmonary edema
  • Hypertension
  • Increased CVP
  • Polyuria with decreasing specific gravity
  • Cyanosis
  • Hemodilution

28
Fluid Composition Problems
  • Hypernatremia / hyponatremia
  • Hyperkalemia / hypokalemia
  • Hyperchloremia / hypochloremia
  • Hypercalcemia / hypocalcemia
  • Magnesium
  • Phosphate
  • Glucose

29
Hypernatremia
  • Causes
  • Excess renal excretion of free water
  • Sweating / fever
  • Diarrhea
  • Respiratory evaporation

30
Signs of Hypernatremia
  • Mental changes
  • Thirst
  • Peripheral edema
  • Myoclonus
  • Cardiovascular collapse

31
Treatment of Hypernatremia
  • Restore volume with hypotonic solution
  • Loop diuretics

32
Causes of Hyponatremia
  • Renal failure
  • CHF
  • Replacement with sodium-free solution
  • Inappropreiate ADH
  • Decreased serum osmolality
  • TURP Syndrome

33
Signs of Hyponatremia
  • Hypertension / hypotension
  • Mental confusion
  • Seizure / coma

34
Treatment of Hyponatremia
  • Reduce excess fluid volume
  • Administer hypertonic solution

35
Use Caution When Correcting Hyponatremia
  • Rapid correction may cause
  • Central pontine myelinolysis
  • Osmotic demyelination syndrome
  • Correct 1-2 meq/hr to 120 meq/s
  • Then 0.5 meq/hr to normal

36
Hyperkalemia
  • Causes
  • Inadequate excretion
  • Excessive intake
  • Extracellular redistribution
  • Cellular destruction
  • Succinylcholine

37
Signs of Hyperkalemia
  • ECG peaked T waves
  • Prolonged PR interval
  • Absent P wave
  • Wide QRS with severe hyperkalemia
  • V-Tach / V-Fib

38
Treatment of Hyperkalemia
  • Alkalization
  • Hyperventilation
  • Bicarbonate
  • Calcium chloride
  • Glucose / insulin
  • Potassium banding resin
  • Diuretics
  • Dialysis

39
Hypokalemia
  • Causes
  • Usually iatrogenic
  • Diuretics
  • G.I. fluid loss
  • Sweating
  • Exacerbated by respiratory alkalosis

40
Signs of Hypokalemia
  • Lab values
  • ECG changes

41
Treatment
  • Consider delaying surgery
  • Lower limit 2.5-3.0??
  • Consider total body depletion
  • Consider magnesium deficit
  • Give dilute solution slowly in peripheral I.V.

42
Chloride Disorders
  • Most commonly related to
  • acid-base disorders

43
Hyperchloremia
  • Causes
  • Renal tubular acidosis
  • Excessive chloride admisistration
  • Signs
  • Hypercholremic acidosis
  • Treatment
  • Consider correcting the acidosis with bicarbonate

44
Hypochloremia
  • Causes
  • Alkalosis secondary to excessive chloride loss
  • Diuretics
  • NG suction
  • May follow massive blood transfusion

45
Hypochloremia
  • Signs
  • Metabolic alkalosis
  • Hypoventilation
  • Treatment
  • Saline with potassium or ammonium chloride
  • Diamox

46
Calcium Disorders
  • 99 of the bodys calcium is contained the bone
    and not available in circulation
  • Major function - To maintain cell membrane
    integrity and excitability
  • Required for coagulation cascade

47
Hypercalcemia
  • Causes
  • Bone degenerating diseases (Kirby 42-8)
  • Excessive intake
  • Decreased excretion
  • Parathyroid disease
  • Renal failure

48
Treatment
  • Correct underlying problem
  • Diuresis with large volume saline
  • Calcium binding drugs
  • Careful positioning

49
Hypocalcemia
  • Causes- (Kirby Table 42-9)
  • Redistribution
  • Alkalosis
  • Hypomagnesemia
  • Inadequate intake
  • Rapid infusion of banked blood

50
Signs
  • Irritability of electrically active cells
  • Tetany
  • Chvosteks sign
  • Trousseaus sign
  • Dysrhythmias
  • Prolonged QT interval

51
Treatment of Hypocalcemia
  • Calcium chloride 15 mg/hr via central line
  • Calcium gluconate 45 mg/kg via peripheral or
    central line

52
Magnesium
  • Intracellular cation
  • Given to treat dysrhythmias secondary to
    hypomagnesemia or hypokalemia
  • Given to treat pre-eclampsia or eclampsia

53
Magnesium
  • High magnesium levels
  • Hypotension
  • Muscle weakness
  • Potentiate non-depolarizing relaxants

54
Phosphate Disorders
  • Phosphates required for normal ATP function
  • Disorders associated with chronic malnutrition

55
Glucose
  • Will be covered in Diabetes unit
  • Mild hyperglycemia is better than hypoglycemia in
    the operating room
  • Can be dangerous when outside the range of 100-300

56
Types of Fluids(see Morgan Table 29-2)
  • Many solutions available
  • Maintenance solutions - hypotonic solutions to
    replace water loss
  • Replacement solutions - replace both water and
    electrolyte deficits

57
What is free water?
  • Water from drinking fountain
  • Rain
  • Water in excess of electrolyte content
  • Water you dont have to pay for

58
Ringers Lactate
  • Most commonly used solution in the O.R.
  • Slightly hypotonic - 100 ml free water / liter
  • Most physiologic solution when large volumes are
    needed
  • Lactate metabolizes in liver to bicarbonate

59
Normal Saline
  • Large volumes cause dilutional hyperchloremic
    acidosis
  • Preferred solution for
  • Hypochloremic metabolic acidosis
  • Diluting packed cells

60
5 Dextrose in Water
  • Dextrose is metabolized leaving a large volume of
    free water
  • Used for patients on sodium restriction
  • Some dextrose needed when insulin is given

61
Intraoperative Fluid Requirements
62
Intraoperative Fluids
  • Must Replace
  • Maintenance
  • Deficit
  • Actual blood loss
  • Third space loss

63
Maintenance Fluids
  • Water and electrolytes needed for normal
    metabolism
  • Need 1 ml/hr for each kilocalorie expended

64
Fluid Deficits
  • Ongoing normal losses
  • Intestinal / renal
  • Perspiration
  • Respiratory tract

65
Fluid Deficits
  • Increased loss
  • Vomiting, diarrhea, ostomy
  • Bowel prep
  • Fever
  • Hyperventilation
  • Loss of skin integrity

66
Intraoperative Fluid Loss
  • Actual blood loss
  • Hidden internal bleeding
  • Evaporation from exposed surfaces
  • Third space loss

67
Estimating Blood Loss
  • Volume in suction minus irrigation
  • Volume on drapes
  • Volume on surgical sponges
  • Observe for blood on the flood

68
Blood Loss
  • Small sponges
  • Large laporotomy sponges

69
Actual Blood Loss
  • Multiply surgeons guess by 2
  • Divide anesthetists guess by 2
  • Average those numbers

70
Your patient is a lean 70 kg and has a hematocrit
of 38. How much blood can be lost to drop the
hematocrit to 26?
71
Calculating Allowable Blood Loss
72
Allowable Blood Loss
  • 1. Starting HCT minus lowest HCT
  • 2. Divide by the average of the above
  • 3. Multiply times the estimated blood volume

73
Example
  • 70 kg patient (lean)
  • EBV 70kg X 70 ml/kg 4900 cc
  • Starting HCT 38 minus lowest HCT 26
  • 38 minus 26 12
  • 12 divided by average of 26 and 38
  • 12 divided by 32 .375
  • 0.375 X 4900 1837 cc

74
Remember, as the patient becomes more obese, the
ml/kg is reduced
75
What is the immediate effect of acute blood loss
on the HCT?
76
Throughout a long case with moderate blood loss
your patient is becoming progressively
hypovolemic. What will you see on the blood gas?
77
What is third space loss?
78
Third Space Loss
  • Shifting fluid to interstitial spaces
  • Any traumatized tissue becomes edematos
  • Third space loss is isotonic - replace with
    Ringers

79
How much third space loss?
  • Minimal 3-4 ml/kg/hr
  • Moderate 5-6 ml/kg/hr
  • Severe 7-8 ml/kg/hr

80
Developing a Care Plan
  • You must have a written plan for anticipated
    fluid therapy
  • Calculate maintenance fluids
  • Calculate deficit
  • Estimate third space loss
  • Replace actual blood loss

81
Maintenance Fluids
  • Many formulas available
  • Hourly formulas
  • 24 hour formulas

82
Hourly Maintenance Formula
  • 4 ml/kg/hr for 1st 10 kg
  • 2 ml/kg/hr for 2nd 10 kg
  • 1 ml/kg/hr for all weight over 20 kg

83
Example
  • 72 kg patient
  • 4 ml/kg/hr for 1st 10 40 ml
  • 2 ml/kg/hr for 2nd 10 20 ml
  • 1 ml/kg/hr for 52 kg 52 ml
  • Total 112 ml/hr

84
24 Hour Formula
  • 100 ml for 1st 10 kg
  • 50 ml for 2nd 10 kg
  • 20 ml for remaining kg
  • Divide by 24 to get hourly rate

85
Example
  • 72 kg patient
  • 100 ml for 1st 10 kg 1000 ml
  • 50 ml for 2nd 10 kg 500 ml
  • 20 ml for 52 kg 1040 ml
  • Total 1040 ml
  • Divide by 24 106 ml/hr

86
Fluid Deficit
  • Calculate hourly maintenance
  • Multiply by hours NPO
  • Consider other factors
  • Overnight I.V.
  • Bowel prep
  • Replace 1/2, 1/4, 1/4

87
Does Anesthesia Affect Fluid Needs?
88
Effects of General Anesthesia
  • Vasodilation may unmask compensated hypovolemia
  • Decreased release of atrial natriuretic hormone
  • Increased release of ADH

89
Effects of Regional Anesthesia
  • Block of sympathetic nerves
  • Vasodilation
  • Hypotension

90
Complication of Fluid Therapy
  • Peripheral edema
  • Pulmonary edema
  • Increased intracranial pressure
  • Coagulopathy
  • Allergies to colloids

91
Thats all folks!
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