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Fluid and electrolytes
1. Fluid and Electrolytes in Surgical
patients
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Presenter: Dr Khagendra Shrestha
Resident, General Surgery
PAHS, Pokhara
2. Objectives
• To review the normal fluid composition of the body.
• To understand the physicochemical and biologic properties of the
various crystalloid and colloid solutions available.
• To discuss the perioperative fluid management.
• To review about the management of common electrolytes imbalance.
2
7. Types of Fluids
A. Crystalloids
1. Saline solutions
2. Balanced solutions
3. Dextrose solutions
B. Colloids
1. Human Plasma Derivatives – Albumin solutions
2. Semisynthetic Colloids – Gelatins, HES, Dextran.
C. Blood and Blood products
1.Whole blood, PCV, FFP, PRP, PC,
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8. Crystalloids
• Electrolyte solutions with small molecules that can diffuse freely
throughout the extracellular space.
• 70% of a crystalloid infusion remains in the intravascular
compartment at the end of a 20-minute continuous infusion,
decreasing to 50% after 30 minutes.
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10. Saline Solutions
0.9% Sodium Chloride
• One of the most commonly administered crystalloids.
• Though called normal saline, it is neither chemically nor physiologically
normal.
• Infusion of one liter of 0.9% NaCL adds 275 mL to the plasma volume
and 825 mL to the interstitial volume.
• Infusion of saline leads to a hyperchloremic metabolic acidosis, reduced
renal perfusion and promote interstitial edema.
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11. Hypertonic Saline
• Available as solutions of 1.8%, 3%, and 7.5% NaCl.
• Uses:
• Plasma volume expansion.
• Correction of hypoosmolar hyponatremia.
• Treatment of increased intracranial pressure.
• reduce cerebral edema and intracranial pressure.
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12. Ringer’s Fluids
• Advantage
• lack of a significant effect on acid-base balance
• Disadvantage
• the ionized calcium in Ringer’s solutions can bind to the citrated
anticoagulant in stored RBCs and promote clot formation.
• contraindicated as diluent fluids for the transfusion of erythrocyte
concentrates (PRBC).
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13. Other Balanced Salt Solutions
• Normosol and Plasma-Lyte
Contain magnesium instead of calcium.
Contain both acetate and gluconate buffers to achieve a pH of 7.4.
Less tendency to promote interstitial edema when compared with
isotonic saline.
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14. Dextrose Solutions
• D5, D10, DNS
• Less than 10% of the infused volume of D5 remains in the vascular
compartment.
• Therefore the predominant effect of D5 infusions is cellular swelling.
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15. Dextrose Solutions
• Uses:
• Replacement of pure water deficits
• Maintenance fluid for patients on sodium restriction
• Source of metabolic substrate
• If glucose utilization is impaired (as is common in critically ill
patients), large- volume infusions of D5 can result in cellular
dehydration.
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16. Colloids
• Contain large, poorly diffusible, solute molecules that create an
osmotic pressure to keep water in the vascular space.
• About three times more effective than crystalloid fluids for increasing
plasma volume.
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17. Albumin Solutions
• Albumin:
• Principal determinant of plasma colloid oncotic pressure
• Principal transport protein in the blood
• Significant antioxidant activity
• Heat treated preparations of human serum albumin
• 5% sol (50g/l) and 25% sol (250g/l) in 0.9% NaCl
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18. Albumin Solutions
5% Albumin Solution
• Given in aliquots of 250 mL
• Plasma volume increment
averages 100% of infused
volume
• Volume effect begins to dissipate
at 6 hrs and can be lost after 12
hrs
25% Albumin Solution
• Given in aliquots of 50/100 mL
• Plasma volume increases by 3 to
4 times the infusate volume
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22. Perioperative Fluid Therapy
• Vary depending on
• Patient factors, including weight and comorbidity
• Surgical factors, such as the magnitude and site of surgery
• The aims of perioperative fluid administration should be to:
• avoid dehydration,
• maintain an effective circulating volume, and
• prevent inadequate tissue perfusion
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23. Perioperative Fluid Therapy
• Includes:
1. replacement of normal losses (maintenance requirements),
2. replacement of preexisting fluid deficits, and
3. replacement of surgical wound losses including blood loss.
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25. Preexisting Deficits
• Preoperative bleeding, vomiting, nasogastric suction, diuresis, and
diarrhea are often contributory.
• Fluid shifting out of intravascular space because of burns,
inflammation(as in pancreatitis) ,intestinal obstruction, infection and
sepsis.
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26. Surgical Fluid Losses
1. Blood Loss
• Monitor and estimate blood loss
2. Other Fluid Losses
• Obligatory losses of fluids other than blood
• Mainly due to
• evaporation and
• internal redistribution of body fluids (third space loss)
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27. Intraoperative Fluid Replacement
• Include supplying basic fluid requirements and
• Replacing residual preoperative deficits as well as intraoperative
losses (blood loss, fluid redistribution, and evaporation)
• For minor procedures involving minimal or no blood loss, minimal or
no fluid
• For all other procedures, a balanced crystalloid such as lactated
Ringer’s solution or Plasmalyte
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28. Replacing Redistributive & Evaporative Losses
• Primarily related to wound size and the extent of surgical dissections
and manipulations.
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29. Post operative fluids
• Aim: To maintain reasonable vitals
BP >100/70 mmhg, PR <120/min, Urine output: 30-50ml/hour, with
normal temperature, warm skin, normal respiration and sensation.
• Ringer lactate is most physiological fluid.
• Intra op blood loss replaced with equal volume of
crystalloid. Ideal is to replace volume of blood lost
with three times volume of crystalloids.
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30. When and how long to give iv fluids
• Depends on type and duration of surgery.
• Patients subjected to short operative procedures , who
don’t need handling of intestinal viscera will only need
maintenance iv fluids to correct deficit due to NPO.
• Patients with major surgeries (exploratory laparotomy,)
where intestinal viscera need rest, require post op iv fluids
for few days.
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31. NICE Guideline:
• In Dec.2013 NICE introduced a guideline for the provision of
intravenous (IV) fluid therapy in adults in hospital.
• The guidance is applicable to adults in hospital, but excludes some
groups.
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37. Electrolytes
- Maintain body fluid volume and osmolarity
- Distribute body water between fluid compartment
- Promote neuromuscular conductivity
- Regulate acid-base balance
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38. Regulation of Total Body Electrolyte Mass and
Plasma Concentrations
Electrolyte Regulated by
Sodium Total body sodium regulated by
aldosterone, ANP, [Na+] altered by
ADH
Potassium Total body potassium regulated by
aldosterone, intrinsic renal
mechanisms;
[K+] regulated by epinephrine,
insulin
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39. SODIUM
• Principal extracellular cation and solute
• Essential for generation of action
potentials in neurologic and cardiac
tissues.
• Normal value:135-145 mEq/L
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40. Hyponatremia
• Hyponatremia is defined as plasma [Na+] <135 mEq/L
• Classified as
• Mild (130 to 134 mEq/L),
• Moderate (120 to 130 mEq/L), or
• Severe (<120 mEq/L)
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41. Clinical features of Hyponatremia
• Acute onset (< 48 hrs):
• symptoms typically occur when [Na+] as low as 120 to 125 mEq/L
with headache, confusion, agitation, vomiting, and lethargy
• [Na+] < 110 mEq/L - seizures and coma
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42. Clinical features of Hyponatremia
• Acute onset (<48hr)
when [Na+] as low as 120 to 125 mEq/L
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44. • Chronic:
•clinical features may be absent even at [Na+] < 120
mEq/L.
•Other features include loss of appetite, nausea,
vomiting, cramps, weakness.
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45. Management of Hyponatremia
•Infusion Rate For Hypertonic Saline:
The initial infusion rate of hypertonic saline (3%
NaCl) can be estimated by :
- Weight in kg * desired rate of rise in plasma/hr.
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46. Osmotic Demyelinating Syndrome
• Measures recommended for avoiding osmotic demyelination:
• For chronic hyponatremia
• the plasma [Na] should not rise faster than 0.5 mEq/L per hour (or 10–12
mEq/L in 24 hours), and
• the rapid correction phase should stop when the plasma [Na] reaches 120
mEq/L.
• For acute hyponatremia,
• the plasma [Na] can be increased by 4–6 mEq/L in the first 1– 2 hrs.
• However, the final plasma [Na] should not exceed 120 mEq/L.
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47. Na+ Replacement
• Na Deficit = (Na Desired - Na observed) x 0.6 x body weight (kg)
• Replace half in first 8 hours and the rest in the following 16 hours
• Rise in serum Na should not exceed 10-12 mEq/L in first 24 hrs to
prevent Central Pontine Myelinolysis
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48. Hypernatremia
• Hypernatremia is defined as a plasma [Na+] >145 mEq/L
• Less common than hyponatremia
• May affect up to 10% of critically ill patients.
• If severe ([Na] > 160 mEq/L), a 75% mortality may occur depending
on the severity of the underlying disease process.
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49. Management of Hypernatremia
• The first step in treating hypernatremia is to estimate the TBW deficit:
• Hypernatremia must be corrected slowly because of the risk of neurologic
sequelae such as seizures or cerebral edema.
• The water deficit should be replaced over 24 to 48 hours.
• The plasma [Na+] should not be reduced by more than 1 to 2 mEq/L/hr for
the first few hours and, if the hypernatremia has been present for more than
2 days, no more than 10 mEq/L/day.
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50. POTASSIUM
• Important role in cell membrane
physiology
• Generating action potentials in the
central nervous system and heart
• Intracellular - 150 mEq/L,
Extracellular - 3.5 to 5 mEq/L
• Normal value: 3.5-5 mEq/L
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51. Hypokalemia
• Hypokalemia is defined as a plasma [K+] <3.5 mEq/L
• Can be the result of K+ movement into cells (transcellular shift), or a
decrease in total body K+ ( K+ depletion)
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52. Mechanism Cause
Intracellular K+ shift ß2 agonists Lithium overdose
Insulin therapy Hypothermia
Alkalosis
Inadequate intake Anorexia nervosa
Alcoholism
Malnutrition
GI loss Vomiting
Diarrhoea
Fistulas
Excess Renal loss Mineralocorticoid excess
Glucocorticoid excess
Diuretics
Osmotic substance
Renal tubular acidosis
Bartter and Gitelman syndrome
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53. Clinical Features of Hypokalemia
• Asymptomatic in most
cases.
• Moderate-to-severe
hypokalemia (2 to 2.5
mEq/L) leads to
muscle weakness,
ECG abnormalities (
50% cases)
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54. Management of Hypokalemia
• Mild Hypokalemia ( K+ > 2 mEq/L )
• IV KCL infusion ≤ 10 mEq/hr
• Severe Hypokalemia ( K+ ≤ 2 mEq/L, paralysis or ECG changes )
• IV KCL infusion ≤ 40 mEq/hr
• Continuous ECG monitoring
• If life threatening, 5-6 mEq bolus
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55. Safe rules for giving potassium:
1. Urine output at least 40ml/hour.
2. Not more than 40 mmol added to 1 Lt.
3. No faster than 40 mmol/hr.
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56. Hyperkalemia
• Hyperkalemia is defined as a plasma [K+] >5.5 mEq/L
• Can be a life threatening condition.
• Can be the result of
• potassium release from cells (transcellular shift), or
• impaired renal excretion of potassium
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60. CALCIUM:
• Most abundant electrolyte in the body overall.
• 99%- Bone, 1%- Blood.
• Essential cofactor in the coagulation cascade.
• Participates in the regulation of neuronal, hormonal, muscular and
renal cellular function.
• Normal range: 8.5 – 10.5 mg/dl
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61. MAGNESIUM:
• Second most prevalent cation in the cell.
• Critical cofactor in any reaction powered by ATP.
• Also acts as a calcium channel antagonist.
• Normal range: 1.5 – 2.0 mEq/L
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62. Summary
• Fluids should be considered as drugs with specific indications,
cautions, dose ranges, and side effects.
• The secret to selecting the appropriate resuscitation fluid is to ask the
question—what is the cause and severity of the hypovolemia in this
patient?
• A single variable (i.e. the extracellular volume), can be used to
understand, identify, and correct the osmotic impact of hypernatremia
and hyponatremia.
• Hypokalemia is remarkably well tolerated compared to hyperkalemia.
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63. References
• Sabiston textbook of surgery.
• Schwartz’s principles of surgery.
• Bailey &Love’s short practice of surgery.
• RCS course manual 4th edition.
• NICE clinical guideline (CG174) published on 2013.
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Av. insensible loss – 8 to 12 ml/kg(60-75% resp and 20-40% skin)
Indicated for replacement of free water and electrolytes and used for volume expansion
Large-volume crystalloid infusion also may be associated with a hypercoagulable state caused by dilution of circulating anticoagulant factors.
A 2-L infusion of 0.9% NaCl leads to an increase in ECF volume, dilutional decrease in hematocrit and albumin, increase in Cl− and K+ concentrations, and decrease in plasma HCO3−.
The increase in interstitial edema can have a negative influence on clinical outcomes.
NaCl concentration greater than 7.5% may cause endothelial damage
Hypertonic saline may be superior to mannitol.
clot formation in erythrocyte concentrates (packed RBCs) does not occur if the volume of Ringer's lactate does not exceed 50% of the volume of packed RBCs
aminocaproic acid (Amicar), amphotericin, ampicillin, and thiopental
One gram of dextrose provides 3.4 kilocalories (kcal) when fully metabolized, so a 5% dextrose solution (50 grams dextrose per liter) provides 170 kcal per liter. Daily infusion of 3 liters of a 5% dextrose (D5) solution will then provide about 500 kcal per day, which is enough nonprotein calories to limit the breakdown of endogenous proteins to meet daily caloric requirements
dextrose is taken up into cells in the presence of insulin, leaving free water. These solutions are therefore hypotonic with respect to the cell membrane and in excess can dilute plasma electrolytes and osmolality.
less suitable for intravascular plasma volume expansion
25% albumin should not be used as volume replacement therapy for patients with acute blood loss or dehydration. Albumin as less inflammatory properties than crystalloids. And associated with minimal coagulopathy compared to other colloids. Books have explained about 25%albumin solution however in practice we commonly use 20%solutions for 3 consecutive days. 50ml of 25%albumin is physiologically equivalent to approx 2000-2500ml of cyrstalloids.
the intravascular half-life of a crystalloid solution is 20 to 30 min, most colloid solutions have intravascular half-lives between 3 and 6 h
Different fluid requirements are encountered in the preoperative, intraoperative, and postoperative phases
prevent inadequate tissue perfusion during a period when the patient is unable to achieve these goals through normal oral fluid intake.
The goals of fluid therapy:
To ensure adequate circulating volume to support cellular O2 delivery and avoid the deleterious effects of hypoperfusion
To avoid the iatrogenic side effects of fluid administration
For a 70kg NPO man , fluid rate in ml/ per hour is 40+ wt in kgs= 40+70=110ml/hr
In the absence of oral intake, fluid and electrolyte deficits can rapidly develop as
a result of continued urine formation, gastrointestinal secretions, sweating, and
insensible losses from the skin and lungs. The current standard is to use 5% dextrose in half – NS with 40 mEq/L of potassium.
Ideally, deficits should be replaced preoperatively in surgical patients, and the
fluids administered should be similar in composition to the fluids lost
Evaporative losses are most significant with large wounds, especially burns
massive fluid shifts and severe intravascular depletion in patients with peritonitis, burns, and similar situations characterized by inflamed or infected tissue.
Three times volume of fluid will maintain intravascular blood volume and cardiac output but O2 carrying capacity of blood will be compromised . So blood should be arranged as soon as possible.
Maintenance fluids on first post op day are less in salt low total vol due to excess salt retention by body due to ADH and aldosterone from pain and GA
For example, if the patient weighs 70 kg and the desired rate of rise in plasma [Na] is 0.5 mEq/L per hour, the initial infusion rate of hypertonic saline is 70×0.5 = 35 mL/hr
Reversible underlying causes should be treated
The standard method of intravenous K+ replacement is to add 20 mEq of K+ to 100 mL of isotonic saline and infuse this mixture over 1 hour
Serum K+ may be slow to rise initially.
If the hypokalemia is resistant or refractory to K+ replacement, magnesium depletion should be considered. Magnesium depletion promotes urinary K+ loss and in patients who are magnesium deficient, hypokalemia is often refractory to K+ replacement until the magnesium is repleted
HEMODIALYSIS: The most effective method of potassium removal is hemodialysis, which can produce a 1 mEq/L drop in serum K+ after one hour, and a 2 mEq/L drop after 3 hours
