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Fluids And Electrolytes
1. Celso M. Fidel, MD,FPCS,FPSGS Diplomate Philippine Board of Surgery FLUIDS AND ELECTROLYTES
2. INTRODUCTION HOMEOSTASIS is determined by: Individual’s Intake and output Carefully and precisely regulated by the body during Health One of the most critical aspects of patient’s care is management of the body composition of fluids and electrolytes
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4. INTRODUCTION Thorough understanding of the mechanisms of fluids and electrolytes and certain metabolic responses is essential to the care of surgical patients SURGEONS encounter these PROBLEMS: Additional stress of SURGERY Use of tubes that drain fluids Patient’s inability to tolerate oral intake of fluids and nutrients
5. BODY WATER Water constitutes between 50% to 70%TB Wt. Average Normal Values Young Adult Male 60% of body wt. Young Adult Female 50% of body wt. Total Body Water (% TBW) decreases steadily and significantly with age: 52% in males 47% in females
6. BODY WATER Highest proportion of TB water : Infants 75% to 80% of body weight One Year Old averages 65% of BWt. Lean individuals has greater proportion of water to TBW than the obese
7. FUNCTIONAL COMPARTMENT OF BODY FLUIDS INTRACELLULAR fluid w/in the body’s diverse cell population represent---- 40% largest proportion ---- skeletal muscle principal CATION----- K (potassium) principal ANION ------ phosphates & proteins
8. FUNCTIONAL COMPARTMENT OF BODY FLUIDS EXTRACELLULAR Represents----- 20% of the BW Two major subdivisions plasma volume----- 5% of BW Interstitial( extravascular ) 15% of BW
9. FUNCTIONAL COMPARTMENT OF BODY FLUIDS EXTRACELLULAR Non-functioning components----1%-2% B wt. Connective tissue water Cerebrospinal fluid Joint fluids The principal CATION----- Na+( Sodium) The principal ANION------- Cl (Chloride and bicarbonates
10. FUNCTIONAL COMPARTMENT OF BODY FLUIDS Gibbs-Donnan Equilibrium----- The product of concentration of any pair of diffusable cation and anion on one side of a semi-permeable membrane will equal the product of the same pair of ions on the other side
11. FUNCTIONAL COMPARTMENT OF BODY FLUIDS TWO THIRDS RULE Determination of the exact size of any one of the 3 compartments is virtually impossible Total Body Compartment is approximately 2/3 of BODY Weight
12. FUNCTIONAL COMPARTMENT OF BODY FLUIDS TWO THIRDS RULE Of this 2/3; 2/3 is INTRACELLULAR & 1/3 is EXTRACELLULAR Of the extracellular portion 2/3 is INTERSTITIAL & 1/3 intravascular
13. REPLACEMENT OF WATER By Ingestion By Metabolism-----combustion of foodstuff: Each 100 calories of FAT CARBOHYDRATES PROTEINS VITAL NEEDS W/C DEMANDS continuous water EXPENDITURE Removal of Body Heat ----800cc ( SKIN AND LUNGS) 600-1000 >>>> RANGE DAILY RELEASES 14 CC OF WATER
14. VITAL NEEDS W/C DEMANDS continuous water EXPENDITURE Excretion of UREA, METABOLIC PRODUCTS & MINERAL SALTS 1200 mOsm of solute have to be excreted daily A good kidney can CONCENTRATE urine up to 1400 mOsm solute
15. VITAL NEEDS W/C DEMANDS continuous water EXPENDITURE Average Adult excretes 900 cc H20/day Normal H20 loss in Urine----800-1500cc/ day Normal Na+ loss-----10-100 mEq/ liter of urine
16. Normal Daily Losses 1. GIT 100-200 ml loss in stools 2. GUT 1000- 1500 ml loss in urine 3. Insensible 600-800 ml in adults (divided equally between lungs and skin) a better term would be imperceptible loss
17. Abnormal Losses of Water 1. Fever - 10% increase insensible loss per degree above 37 C. 2. Tachypnea –doubling RR 50% increase resp. L 3. Evaporation- Sweating, ventilator, open wounds 4. GI –Fistula, Diarrhea, Tube drainage 5. Third space – Interstitium of lungs, bowel, soft tissues 6. Intraoperative losses
18. Tonicity Body Fluids ---- composed of water and substances dissolved in it Total number of particles in solution are constant throughout the body, although the nature of the individual solute varies in different parts of the body Tonicity( property derived from the number of particles in solution) Normal----300 mOsm/L
19. Tonicity In PLASMA 280 is due to ELECTROLYTES 1/2 --- 140 mOsm is coming from Na+ 1/2 --- 140 mOsm from Chlorides & Bicarbonates Crystalloids: Sugar Urea 10-20 mOsm Creatinine Protein ------ 2 mOsm
20. Electrolytes, What are They ? Group of compounds-----DISSOCIATES in solution to form “IONS’ after the greek for “ GOING” These ions each carry an electrical charge; example; NaCl -----dissolved in water provides Na+ ---- carries a positive charge Cl- -----carries a negative charge
21. Electrolytes, What are They ? Those IONS carrying a (+) charge migrated to FARADAY’s (-) electrode or “CATHODE” were called ”Cations” after the Greek for “DOWN” Those IONS carrying a (-) charge migrated to FARADAY’s (+) electrode or “ANODE” were called ”anions” after the Greek for “UP”
22. Electrolytes, What are They ? Cations in the body; Na+, K+, Ca++, Mg++ Anions in the body include ; Cl-, HCO3-, HPO4=, SO4=; ions of inorganic acids such as: Lactate Pyruvate Aceto-Acetate Proteinates
23. Electrolytes, What are They ? Each of the water compartments of the body contains electrolytes. However the composition and concentration of these electrolytes in the water of each compartment differ from that of the others.
24. Electrolytes, What are They ? Physiologic and Chemical Activity of electrolytes are proportional to: Number of particles present per unit volume ( MOLES or MILLIMOLES) No. of electrical charges per unit volume ( Equivalents or Milliequivalents per liter)
25. Electrolytes, What are They ? mEq/L=mgs./L X val. divided by the atomic Wt. = mgs/ 1000cc X Valence Atomic Weight OSMOLARITY >>>expression of concentration of ions and proteins in solution in body water. Water moves freely in the body to prevent the development of any compartmentalized osmolar concentration difference.
26. Electrolytes, What are They ? Electrolyte Concentration in Serum Na+ -------- 135-145 mEq/ liter K+ -------- 3.5-5.5 mEq/liter Cl- ----- 85-115 mEq/liter HCO3- ---- 22-29 mEq/liter Mg++ ---- 1.5-2.5 mEq/liter Ca++ ---- 4-5.5 mEq/liter
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28. ELECTROLYTE COMPOSITION OF BODY FLUIDS Na+ K+ H+ Cl- HCO3 Proteins PO4 SO4- Plasma 142 4.5 100 25 16 2 1 Gastric Low Acid 45 30 70 120 25 High Acid 100 45 0.015 115 30 Intestinal Juice 120 20 30 Bile 140 5 40 Pancreatic Juice 130 15 80 Intracellular 10 150 5 10 60 100 20
29. NORMAL DAILY FLUID& ELECTROLYTE LOSSES AND REQUIREMENTS LOSSES/ 24 hours Substances Urine Skin Lungs Feces Total WATER 1200-1500 200-400 500-700 100-200 2300-2600 SODIUM 100 mEq 40 mEq/liter 80-100 mEq POTASSIUM 100 mEq 80-100mEq CHLORIDES 150 mEq 40 mEq/ liter 100-150 mEq REQUIREMENTS WATER 35 ml/ kg. body weight PEDIATRICS 100 ml/kg first 10 kg. body weight 50 ml/kg next 10 kg. “ “ 20 ml/kg for each additional body weight SODIUM 1 mEq/kg body weight POTASSIUM “ “ “ “ CHLORIDE 1.5 mEq/ kg. body weight HCO3 0.5 “ “ “ “
30. THE IONS SODIUM Principal Cation of extracellular fluid Normal requirement is met by the average diet Average intake----- 100 mgs daily Sweat conc. -----27mEq/ L is to 100mEq /L Total secretion---Alimentary Tract 1000-1200 mEq ADH of Pituitary promotes Na+ excretion from the kidney to some extent & to markedly favor water resorption from the distal tubules.
31. THE IONS POTASSIUM (cation) Major exchangeable portion lies within the cell Daily turnover of K+ requirement represents 1.5 to 5% of the total K+ content of the body. Normal 70 kg. man----- 3,200 mEq Average woman--------- 2,300mEq Normal requirement met by average diet Gastric Juice Content----15-40mEq/liter Healthy cell maintains high K+ & low Na+ conc. Patient under stress of disease or in the postop. period>> Normal Kidney excretes 80-90 mEq/day
32. THE IONS POTASSIUM (cation) At 7 mEq/L in Serum----- elevation of T waves on Electro Cardio Gram At 8-10 mEq/L ------Arrhythmia & Heart Block CHLORIDE (ANION) Na+ to Cl- ratio is 3:2 in serum & extracellular compartment It follows changes in Na+ concentration EXCEPT in GASTRIC OBSTRUCTION; Chloride is low Na+ is normal Alkalosis is severe
33. DIAGNOSIS OF IMBALANCES It is the center of any scheme of FLUID and ELECTROLYTE Balance Nature of imbalances and approximate magnitude are based on: History Clinical Signs and Symptoms Certain Laboratory Studies Past Clinical Experience
34. DIAGNOSIS OF IMBALANCES CLUES FROM THE HISTORY In Gastric Outlet Obstruction present in Duodenal Ulcer will produce Pyloric Stenosis alkalosis (loss of Chloride & K+; Hypokalemia; loss of H20 & Na+) Vomiting secondary to a cause other than gastric Outlet Obstruction: Loss of H2O If there is a shift in ACID Loss of Na+ BASE balance, it is towards Loss of K+ METABOLIC ACIDOSIS vomiting
35. DIAGNOSIS OF IMBALANCES CLUES FROM THE HISTORY Diarrhea secondary to: Cholera Loss of Ulcerative Colitis H20, K+, ACIDOSIS Ileostomy dysfunction Na+ Burns produces acute loss of PLASMA & Extra- cellular fluid (Water, Proteins, and Na+) Sweating if excessive causes appreciable loss of both Na+ & H20------ Shrinkage of Extracellular Fluid Volume -------VASCULAR COLLAPSE
36. DIAGNOSIS OF IMBALANCES P.E. should give attention to: BODY WEIGHT Weight gain >>>H20 retention Weight loss 300-500 gms./day expected in postoperative Patients.>>>> In excess of 300- 500 gms/ day indicates H20 loss. Tissue Turgor >>Decrease in T T in volume of the Interstitial Fluid compartment of ECF ( Na+ dependent) Skin Turgor>> useful indicator of diminished interstitial fluid volume
37. DIAGNOSIS OF IMBALANCES P.E. should give attention to: Tissue turgor Tongue>> most reliable indicator forT.T Normally it has a single “Median Furrow” Additional furrows parallel to the median furrow appears with decrease interstitial volume and a need for Na+ Moisture of the axilla and groin . Dry but other- wise normal axilla----H20 deficit, at least 150cc Jugular Veins ------Normally it fills to the anterior border of the sternocleidomastoid muscle when the patient is supine.
38. DIAGNOSIS OF IMBALANCES P.E. should give attention to: Blood Pressure and Pulse Tachypnea>> earliest sign of decrease BVolume Postural Hypotension Need for Blood & Na Hypotension when Supine containing fluid Edema and Rales Pitting Edema>>> Na+ increase >> 400 mEq Rales>> Acute increase in Volume by at least 1500cc
39. DIAGNOSIS OF IMBALANCES LABORATORY TESTS & Other PARAMETERS Hematocrit Urine Specific Gravity Na+ levels in serum and urine CVP monitoring Pulmonary Wedge Pressure
40. DIAGNOSIS OF IMBALANCES LABORATORY TESTS & Other PARAMETERS Hematocrit Urine Specific Gravity Na+ levels in serum and urine CVP monitoring Pulmonary Wedge Pressure Determining the Amount of the Deficit A Vol(H2O) deficit---- Estimate from patient’s Body Wt.& appearance or from the serum Sodium level. The hematocrit gives also useful information.
41. DIAGNOSIS OF IMBALANCES CLINICAL ESTIMATES MILD Dehydration----- Patient losses 3% of the Body Weight ----- THIRSTY MODERATE Dehydration ------ Patient losses 6% of the Body Wt. Clinical signs of dehydration are Evident: Marked Thirst and Dry Mouth No groin and axillary Sweat Loss of Skin Turgor .
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43. DIAGNOSIS OF IMBALANCES CLINICAL ESTIMATES SEVERE Dehydration------Patient losses 10% of Body Weight: Clinical signs of Dehydration are marked. Hypotension may be present Patient may be confused & delirious. BODY WATER CALCULATIONS Body H20 = Normal Serum Na+ X normal B H20 Measured Na+ value
44. DIAGNOSIS OF IMBALANCES Electrolyte deficits. They are calculated after the lab results for Na+. K, Cl, and NaHC03 are in. NaCl & HCO3 deficit are calculated using foll: DEFICIT= NORMAL VOLUME –OBSERVED BODY VOLUME x ELECTROLYTE DISTRIBUTION IN BODY COMP% x BODY WT(KG) WHERE: NA DISTRIBUTION = 60 % CL “ 20 % HCO3 “ 5O%
45. DIAGNOSIS OF IMBALANCES Electrolyte deficits. The K+ deficit is figured differently w/normal Blood pH: For every 1.0 mEq/L decrease in concentration at or above 3.0 mEq----consider the total body deficit as 100-200 mEq. For every1.0 mEq/L decrease in the K+ conc. below 3.0 mEq/L -----consider the total body deficit as another 300-400 mEq.
46. DIAGNOSIS OF IMBALANCES ABNORMAL PATTERNS in Fluids & Electrolytes Disorders of composition & concentration Disorders of Volume Disorders of Acid-Base Balance CLINICAL STATES HYPONATREMIA HYPERCLOREMIA HYPERNATREMIA ACID BASE BALANCE ISOTONIC DEHYDRATION HYPOKALEMIA HYPERKALEMIA
47. DIAGNOSIS OF IMBALANCES HYPONATREMIA Pathophysiology Hypovolemic or Isovolemic Mechanism: Loss of Na+ containing fluid and replacement with salt free fluid( isovolemic) Salt free fluid and administration in excess in the absence of salt loss ( dilutional Hyponatremia)
48. DIAGNOSIS OF IMBALANCES HYPONATREMIA Causes Loss of fluid with high Na+ content: Fistula Ngt Drainage Vomiting Diarrhea Excessive URINE Na+ wastage Diuretics Chronic Nephritis Adrenal Cortical Insufficiency as in Addison’s disease Over infusion of salt free fluid ( dilutional Hyponatremia)
49. DIAGNOSIS OF IMBALANCES HYPONATREMIA Causes cont’d Loss of Extracellular Fluid: Externally: Burns Marked Sweating Internally as in Third Space loss: Peritonitis Ascites Ileus Pancreatitis
50. DIAGNOSIS OF IMBALANCES HYPONATREMIA Clinical Presentation Accumulation of intracellular fluid could cause CNS symptoms: Serum Na+ below 130 mEq/Liter ( Mild) “ “ “ 113 “ “ (Severe) CNS depression, Confusion, Somnolence Signs of Increase Intracranial pressure OLIGURIC Renal Failure in Severe Hyponatremia
51. DIAGNOSIS OF IMBALANCES HYPONATREMIA Management Repeated Na+ determination; other Electrolytes H20 deprivation, Use diuretics Administer Na+ containing Fluids Sodium must be Titrated slowly back to Normal
52. DIAGNOSIS OF IMBALANCES HYPONATREMIA “ Sample CASE” A muscular 50 year old man with polycystic kidney disease presents w/ hypotension, confusion, oliguria, and no axillary sweat. Past medical record reveals that he has polyuria has been eating a low salt diet because of mild hypertension. BUN has been stable at 40mgs/dL;Blood CO2 is 15mmol/L (Metabolic Acidosis) and Na+ level of 120mEq/L.Body Weight is 90kgs; Urine output- 170ml/day GIVEN: Na+ deficit =140mEq – 120mEq = 20mEq/L Total Body H20 = 90kgs X 60 = 54 L Fluid Loss = 10% (Clinical Findings) First Step: COMPUTE for Hypotonic Na+ deficit Hypotonic Na+ deficit = Na+ deficit X TBW = 20mEq X 54 L =1080(Hypotonic Na+ def.)
53. DIAGNOSIS OF IMBALANCES HYPONATREMIA “ Sample CASE” 2 nd Step : COMPUTE for the isotonic Na+ deficit Find out the Isotonic Fluid loss or How much fluid is necessary to revert to ISOTONIC STATE . Formula ISOTONIC FLUID LOSS =Weight X % of FLUID LOSS 90 Kgs. X 10% (9 Liters) Then compute for isotonic Na+ deficit Formula: Isotonic Na+ Loss X NORMAL Na+ level 9 Liters X 140mEq = 1260mEq Total Na+ REQUIREMENT: Hypotonic Na+ Deficit + Isotonic Na+ deficit + Daily requirement 1080mEq + 1260mEq + 75mEq = 2415mEq Initially only ½ is given so divide it by 2 =1207.5 mEq
54. DIAGNOSIS OF IMBALANCES HYPONATREMIA “ Sample CASE” 3 rd Step: COMPUTE for the 24 hours H20 requirement The daily H20 requirement in an OLIGURIC patient is reduced: FORMULA 0.2 ml/kg body wt. + preceeding 24 hour Urine Output +10% for every rise of 1 degree in body temp. =(0.2ml X 90 X 24) + 170 =602 ml/day 24 HOUR H20 requirement = Isotonic Fluid loss(9 L) + 600 = 4.8 Liters 2 4 th Step: Compute for Bicarbonate. The ideal replacement solution should contain a NaCl ratio of 1.4:1 particularly if the patient is ACIDOTIC.
55. DIAGNOSIS OF IMBALANCES HYP0NATREMIA “ Sample CASE” 4 th Step: Compute for Bicarbonate. The ideal replacement solution should contain a NaCl ratio of 1.4:1 particularly if the patient is ACIDOTIC. Sub- Step: Compute for Chloride Requirement 1.4 = 1245 X= 1245 =890 mEq as NaCl 1 X(mEq) 1.4 The Bicarbonate requirement is thus: 1245- 890 =355 mEq of HCO3 PATIENT’S FLUID & ELECTROLYTE REQUIREMENT 4.8 liters of 5% Dextrose in 0.9 % NaCl Add 8 vials of Na2CO3 (44 mEq/50 cc) Plus 200 cc of 5% NaCl injection
56. DIAGNOSIS OF IMBALANCES HYPERNATREMIA Pathophysiology ECF Hyperosmolarity= shift of H20 from cell---- -- ECF- More Fluid --- DEHYDRATION Increased Intracellular Osmolality -- CNS effects: Fever Hallucination Delirium
57. DIAGNOSIS OF IMBALANCES HYPERNATREMIA Causes Prolonged Fever Large surface Burns -- 3-5 Liters loss/day Tachypnea – Do Tube Tracheostomy Renal Damage Loss of Solute Urine High Output Failure Desert Exposure Drinking Salt H2O
58. DIAGNOSIS OF IMBALANCES HYPERNATREMIA Management Gradual Reduction of Serum Na+ Rehydrate patient with salt Free H20 Formula: 70 kg patient with Na+ of 160mEq Total Body Water 60% X 70kgs = 42 Liters= Current Body Water 140 =0.87 or 0.9 16 0.9 X 42 =37.8 Liters current Body Water 42L- 37.8= 4.2 Liters ( water Needed)
59. DIAGNOSIS OF IMBALANCES HYPERNATREMIA “ Sample CASE” A moderately lean woman with esophageal stricture has a serum Na+ level of 160mEq /L (normal is 140mEq). Her present weight is 70kgs. HER REQUIREMENTS WOULD BE CALCULATED AS FOLLOWS: Current Body Water 140mEq =7/8 =87.5 % of normal 160mEq WATER Loss>>> 100%- 87.5% =12.5% of water PATIENT’S NORMAL total BODY WATER 70 X 60% = 42 Liters H20 DEFICIT 42 L X 12.5% = 5.3 Liters
60. DIAGNOSIS OF IMBALANCES HYPERNATREMIA “ Sample CASE ” A moderately lean woman with esophageal stricture has a serum Na+ level of 160mEq /L (normal is 140mEq). Her present weight is 70kgs. HER Fluid REQUIREMENT 2.7 + 2.4 = 5.1 L of fluid needed in the next 24 hours containing 70mEq of Na+ FORMULA USED: ½ H20 Deficit + normal daily fluid requirement ½ H2O Deficit + ( 35cc X70 kgs.) 2.4 Liters
61. DIAGNOSIS OF IMBALANCES HYPERNATREMIA Example If the same patient has diarrhea as well as esophageal stricture and has persisted with weakness, confusion; hypotension CALCULATIONS WOULD BE AS FOLLOWS Present Body Water 140 =7/8 = 87% of NORMAL 160 Water Loss 100-87.5 =12.5% Patient’s Normal Body Water =70kgs X 60% = 42 Liters H20 Deficit: 42 L X 12.5% =5.3 Liters CLINICAL Findings shows 10% dehydration CALCULATIONS should be changed
62. DIAGNOSIS OF IMBALANCES HYPERNATREMIA Example If the same patient has diarrhea as well as esophageal stricture and has persisted with weakness, confusion; hypotension CLINICAL Findings shows 10% dehydration CALCULATIONS should be changed FLUID LOSS 10% of 70kgs = 7 liters ISOTONIC Fluid loss = 7 – 5.3 =1.7 Liters Na+ loss in Isotonic Fluid = 1.7 L X 140mEq = 238mEq 24 Hour Fluid Requirement= ½ H20 deficit + Normal Body Fluid = ½ of 7( 7/2) +2.4 = 5.9 L 24 Hour Na+ Requirement = ½ Na+ deficit + 70 =189mEq This can be given as: 4 liters of 5% Dextrose in Water plus 1200 cc of NORMAL Saline Solution
63. DIAGNOSIS OF IMBALANCES ISOTONIC DEHYDRATION The Serum Na+ Concentration is Normal “ EXAMPLE” A short obese alcoholic patient presents with Vomiting due to gastritis 102 F fever due to pneumonitis Complaining of thirst Has dry mouth No groin or Axillary Sweat Alert and Normotensive Weight of 100kgs. Serum Na+ is 140mEq/L Serum K+ 3mEq/L
64. DIAGNOSIS OF IMBALANCES ISOTONIC DEHYDRATION FLUID and ELECTROLYTE Requirement Fluid Loss = 6% (based on Clinical Findings) Isotonic Fluid loss 100kgs X 6% = 6 Liters Na+ loss (in isotonic fluid) 140mEq X 6=840mEq 24 hours Na+ Requirement 840 + 100mEq = 520mEq 2 24 hour Fluid Requirement 6 + 4.9 L =7.9 L 2
65. DIAGNOSIS OF IMBALANCES ISOTONIC DEHYDRATION FLUID and ELECTROLYTE Requirement EXPLANATIONS: The daily requirement is 4.9 instead of 3.5 because of the patient’s fever. Each 1 degree rise in temperature increase by at least 10% Fluid and Na+ replacement can be given as: 3 Liters of 5% dextrose in Normal Saline 2 Liters of 5% dextrose in water 200cc of Normal saline KCl should be added as indicated at ½ of the DEFICIT plus the the daily requirement (100mEq) provided urine flow is adequate. KCl should be divided among the solutions
66. DIAGNOSIS OF IMBALANCES HYPOKALEMIA CAUSES. Chronic Pyloric Obstruction Ulcerative Colitis Prolonged Vomiting Fistula Diarrhea Diuretic Therapy Nephritis Adrenal Hyperactivity( Stress; Cushing’s Syndrome) PATHOPHYSIOLOGY Loss of GASTRIC JUICE -- minimal loss of K+ -- Loss of Cl.--- insufficient Cl. For renal Tubular reabsorption of Na+ Loss of Na+ ions>>>Adrenal and Renal mechanisms will conserve Na+>>>and add in exchange K+ and H+ are excreted>>>>>>HYPOKALEMIA
67. DIAGNOSIS OF IMBALANCES HYPOKALEMIA CLINICAL FEATURES Less than 3.5mEq/L in serum Associated with: Diuretics Metabolic Alkalosis Aldosterone Secretion GIT losses
68. DIAGNOSIS OF IMBALANCES HYPOKALEMIA CLINICAL FEATURES Prolonged Ileus, Hyporeflexia, Paralysis Increased sensitivity to digitalis Favors ALKALOSIS (because of Acid loss) and alkalosis DECREASE K+ ECG shows Prolonged QT; Depressed ST; T Wave inversion Early Signs of K+ Depletion: Malaise and Weakness Paralytic Ileus and Distention Muscular Paresis
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80. PRINCIPLES OF ACID BASE BALANCE Normal H+ ion concentration in Extracellular fluid is maintained at pH 7.36-7.42 Daily Metabolic products are H+ and CO2 To keep the pH constant, Acids are neutralized by two mechanisms: Buffer System of Body Fluids Regulatory functions of the LUNGS & KIDNEY Most important Buffer System is the Bicarbonate Carbonic Acid System H2CO3 HCO3 + H+
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82. PRINCIPLES OF ACID BASE BALANCE At pH 7.4 ratio of Carbonate to Carbonic Acid is 20:1 In METABOLIC ACID BASE Shifts, effects on buffer system is on LEVEL of BICARBONATE INCREASED: Increased Bicarbonate = ALKALOSIS Decreased “ = ACIDOSIS
83. PRINCIPLES OF ACID BASE BALANCE In METABOLIC ACID BASE shifts = LUNGS compensates: Metabolic Acidosis>> Increased Ventilation >> more CO2 released less H2CO3 Metabolic Alkalosis>> Decreased Ventilation > more CO2 retained >> Increased H2CO3 IN RESPIRATORY ACID BASE shifts the effect on the buffer system is a GAIN or LOSS of CARBONIC ACID Compensatory Mechanism is via the KIDNEYS by retaining or Excreting BICARBONATES
84. PRINCIPLES OF ACID BASE BALANCE Respiratory Acidosis = Increased H2CO3 Compensated by RENAL RETENTION OF BICARBONATE Respiratory Alkalosis = Decreased H2CO3 is Compensated by RENAL EXCRETION of BICARBONATE Serum HCO3 20 pH = Kidney Serum H2CO3 1 Lungs
85. PRINCIPLES OF ACID BASE BALANCE To Follow Acid Base Changes KNOW: Signs and Symptoms Pathophysiology Plasma pH Arterial pCO2 Total Extractable CO2 measured as venous CO2 content corrected to pCO2 of 40mm Hg
86. PRINCIPLES OF ACID BASE BALANCE METABOLIC ACIDOSIS Clinical Aspects Excess H+ in plasma>>Fall in pH >>Diminished>> Plasma Bicarbonates seen in: Loss of fluid rich in Na2CO3 Adrenal Insufficiency>> Renal loss of Na2C03 Low flow state >>>Lactic Acid Diabetes Mellitus
87. PRINCIPLES OF ACID BASE BALANCE METABOLIC ACIDOSIS Pathophysiology Increased rate & depth of breathing> Decrease plasma pC02>>>Decrease H2CO3 with return of pH to normal Laboratory Findings pH below 7.38 HCO3 less than 24mEq/minute Arterial pCO2 40mmHg Acidic Urine w/ low Na+ content
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89. PRINCIPLES OF ACID BASE BALANCE METABOLIC ACIDOSIS Management Treat Cause Adjustment to respirator (if patient is attached to one). Increased RATE decrease arterial pCO2. METABOLIC ALKALOSIS Clinical Aspects HCl loss due to vomiting, gastric drainage Loss of K+ and Cl- in urine
90. PRINCIPLES OF ACID BASE BALANCE METABOLIC ALKALOSIS Clinical Aspects cont’d Diuretics Adrenal Steroids Administration of Na2CO3 or Sodium Citrate (in blood transfusion) Pathophysiology Due to uncompensated loss of Acids or retention of Bases
91. PRINCIPLES OF ACID BASE BALANCE METABOLIC ALKALOSIS Pathophysiology In Metabolic Alkalosis Increase urinary K+ loss>>H+ and Na+ ion enter the cell>> Decrease of Extracellular H+ ion concentration>> further >>increase in Alkalosis.
92. PRINCIPLES OF ACID BASE BALANCE METABOLIC ALKALOSIS Pathophysiology LUNG Compensation: Hypoventilation>>> CO2 accumulation>> Increased Carbonic Acid.
93. PRINCIPLES OF ACID BASE BALANCE METABOLIC ALKALOSIS Pathophysiology RENAL Compensation: Increased Excretion of Bicarbonat e in ALKALINE Urine
94. PRINCIPLES OF ACID BASE BALANCE METABOLIC ALKALOSIS Condition is usually seen in: Multiple Transfusion Hyperventilation Volume Reduction Increased Aldosterone Secretion Administration of Large volume of Ringer’s Lactate
95. PRINCIPLES OF ACID BASE BALANCE METABOLIC ALKALOSIS Laboratory Findings: 1. Blood pH Higher than 7.44 2. HCO3= Higher than 28mEq/L 3. Arterial PCO2= 40 in the presence of Respiratory Compensation
96. PRINCIPLES OF ACID BASE BALANCE METABOLIC ALKALOSIS Management Replace lost Na+, Cl, and K+ ions Lower pH by using of 0.1 N HCl In moderately severe Alkalosis where there is Increased Renal K+ excretion, permit the tubule to retain H+ (treat) w/ IV KCl Severe METABOLIC ALKALOSIS is the only good indication for the administration of NH4CL
97. PRINCIPLES OF ACID BASE BALANCE METABOLIC ALKALOSIS Severe METABOLIC ALKALOSIS is the only good indication for the administration of NH4CL
98. PRINCIPLES OF ACID BASE BALANCE RESPIRATORY ACIDOSIS Clinical Aspects It is caused by Pulmonary Insufficiency 1. Failure to excrete CO2 via the Lungs with normal efficiency as in: a. Pneumonia b. Emphysema c. Fibrosis
99. PRINCIPLES OF ACID BASE BALANCE RESPIRATORY ACIDOSIS Clinical Aspects It is caused by Pulmonary Insufficiency 2. Hypoventilation caused by a. Pulmonary Edema b. Injury c. Post op. Atelectasis d. Drugs e. Poor Ventilation( Respirator)
100. PRINCIPLES OF ACID BASE BALANCE RESPIRATORY ACIDOSIS Clinical Aspects Manifested by: 1. Somnolence 2. Confusion 3. Coma due to CO2 Narcosis
101. PRINCIPLES OF ACID BASE BALANCE RESPIRATORY ACIDOSIS Pathophysiology Compensatory Mechanism: 1. Increase Tubular reabsorption of Na+ and bicarbonate by Kidneys 2. Increase excretion of H+ ions
102. PRINCIPLES OF ACID BASE BALANCE RESPIRATORY ACIDOSIS Laboratory Findings 1. Blood pH below 7.38 2. Arterial pCO2 over 50mm Hg 3. Acute Respiratory Acidosis= Plasma H2CO3 not increased 4. In Chronic state it’s elevated to 20mEq/L
103. PRINCIPLES OF ACID BASE BALANCE RESPIRATORY ACIDOSIS Management Control ventilation to increase inspired 02>>> Return of Arterial Blood Gas to Normal Careful and slow correction of pH and pCO2 so as not to produce rapid changes with associated Cardiac instability
104. PRINCIPLES OF ACID BASE BALANCE RESPIRATORY ALKALOSIS Clinical Features Due to Hyperventilation seen in: 1. Pulmonary Infection 2. Hysteria 3. CNS Injury 4. Occasionally during Anesthesia 5. Fever 6. Pain 7. Apprehension 8. Salicylate Poisoning
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106. PRINCIPLES OF ACID BASE BALANCE RESPIRATORY ALKALOSIS Laboratory Findings : 1. Blood pH more than 7.46 2. Arterial pCO2 is lower than 36mm Hg. 3. With renal compensation Bicarbonate level will fall 4. Urinary Na+ concentration is high
107. PRINCIPLES OF ACID BASE BALANCE RESPIRATORY ALKALOSIS Management Directed at its initiating Causes Note: Mild respiratory alkalosis is common postoperative problem Associated muscle irritability or frank tetany especially if serum calcium++ level is low Corrected by administration of calcium salts Calcium Chloride, Calcium Gluconate
108. PRINCIPLES OF ACID BASE BALANCE FORMULA FOR Acid Base Imbalance Serum HCO3 = 20 Serum H2CO3 1 in the numerator 20/1 to 10/1 >Met. ACIDOSIS in the numerator 20/1 to 30/1 >Met. ALKALOSIS in the denominator 20/1 to 20/2>>Resp Acidosis in the denominator 20/1 to 20/.5 > R. Alkalosis
109. PRINCIPLES OF MANAGING FLUID, ELECTROLYTE AND ACID BASE IMBALANCE PRIORITIES 1. Correct SHOCK and restore Blood Volume>>Normal 2. Restore Colloid Osmotic Pressure 3. Correct Acid Base Imbalance 4. Restore Blood Osmolality 5. Correct K+ deficit 6. Correct Total Body Electrolytes disturbance (static debt) and establish daily maintenance
110. PRINCIPLES OF MANAGING FLUID, ELECTROLYTE AND ACID BASE IMBALANCE DEFICIT CORRECTION Fluid and Electrolyte Therapy to Correct existing Deficit. Examples : Blood volume deficit in Acute or Chronic Blood loss. Extracellular or Intracellular deficit in dehydration Deficit correction is added to maintenance and replacement therapy in order to restore H20, salt balance Deficit correction is also Top priority in Fluid and Electrolyte therapy
111.
112. PRINCIPLES OF MANAGING FLUID, ELECTROLYTE AND ACID BASE IMBALANCE REPLACEMENT THERAPY Necessary to Replace Abnormal (continuing) losses from or within the body. Example via drainage tubes.
113. PRINCIPLES OF MANAGING FLUID, ELECTROLYTE AND ACID BASE IMBALANCE REPLACEMENT THERAPY Gastrointestinal Losses If these are purely gastric( succus gastricus); A solution providing 0.45% NaCl mEq plus 40 mEq of KCl per liter is used for replacement.
114. PRINCIPLES OF MANAGING FLUID, ELECTROLYTE AND ACID BASE IMBALANCE REPLACEMENT THERAPY Gastrointestinal Losses If the fluid lost contains intestinal (succus entericus) Lactated Ringer’s solution plus 10 mEq KCl per liter is used .
115. PRINCIPLES OF MANAGING FLUID, ELECTROLYTE AND ACID BASE IMBALANCE REPLACEMENT THERAPY Third Space Loss 1. The amount of loss varies with the magnitude of injury. 2. Lactated Ringer’s solution plus Albumin is used.
116. PRINCIPLES OF MANAGING FLUID, ELECTROLYTE AND ACID BASE IMBALANCE REPLACEMENT THERAPY Continuing losses require volume for volume replacement and added to maintenance requirements. Replacement Therapy has second priority in Fluids & Electrolyte Therapy
117. PRINCIPLES OF MANAGING FLUID, ELECTROLYTE AND ACID BASE IMBALANCE MAINTENANCE THERAPY Clinical Example: Average size 60kgs woman has an Elective Cholecystectomy. No drainage tubes. Patient’s Normal Daily Requirements H2O : 35ml/kgs X 60 >>> 2100 cc Na+ : 1mEq/kgs X 60 >>> 60mEq K+ : 1mEq/kgs X 60 >>> 60mEq Cl- : 1.5mEq/mEq X 60 >>> 90mEq HCO3-: 0.5mEq/mEq X 60 >>> 30mEq
118. PRINCIPLES OF MANAGING FLUID, ELECTROLYTE AND ACID BASE IMBALANCE MAINTENANCE THERAPY Methods to calculate H20 maintenance requirement 1. Utilization of body water as a guide for H20 Ex. 70 kg. x 0.5 x 24 hrs + 500ml/24 hrs = 1340ml/24hrs 2. It can be based on patient’s weight (Pediatric Patients) 100 ml/kg for the first 10 kg of body weight 50 ml/kg for the next 10 kg of body weight 20 ml/kg for each additional kg of body weight
119. PRINCIPLES OF MANAGING FLUID, ELECTROLYTE AND ACID BASE IMBALANCE MAINTENANCE THERAPY Methods to calculate H20 maintenance requirement 3. A given amount of water /kg body wt. can be used. (35 ml/kg/24 hours) 4. A given amount of fluid regardless of wt. (125ml/hr)
120. PRINCIPLES OF MANAGING FLUID, ELECTROLYTE AND ACID BASE IMBALANCE MAINTENANCE THERAPY IV Fluids would be as follows: 1. 1000 ml of 5% Dextrose in H2O + 40mEq Kcl 2. 650 ml of 5% Dextrose in H20 + 20mEq KCl 3. 450 ml of 5% Dextrose in Lactated Ringer’s solution
121. PRINCIPLES OF MANAGING FLUID, ELECTROLYTE AND ACID BASE IMBALANCE MAINTENANCE THERAPY This would provide: 2100 ml of Water 58.5mEq of Na+( 4.5 X 1.3mEq/dl LR 61.8mEq of K+ (60mEq from KCl+1.8mEq 109mEq of Cl( 60mEq from KCl + 49mEq 12.6mEq of HCO3( 4.5 X 2.8mEq/dl LR
122. PRINCIPLES OF MANAGING FLUID, ELECTROLYTE AND ACID BASE IMBALANCE REPLACEMENT THERAPY The same patient develops ileus. NGT was placed. Over 24 hours 1600 ml NGT bile stained fluid was collected. Normal serum electrolytes. For replacement she would require: 1600 ml D5LR solution +10mEq of KCl
123. PRINCIPLES OF MANAGING FLUID, ELECTROLYTE AND ACID BASE IMBALANCE REPLACEMENT THERAPY Her maintenance requirement would be the same 1000 ml of 5% Dextrose in H2O + 30mEq Kcl 1000 ml of 5% Dextrose in H20 + 30mEq KCl 2 liters of 5% Dextrose in Lactated Ringer’s solution + 10mEq KCl to each liter. Run at 170ml/hr( 400 maintenance 600 Replacement)
124. OTHER COMMONLY USED FLUIDS SOLUTIONS NA+ CONTENT Cl CONTENT USES 3% NaCl INJ. 51 51 For symptomatic Na deficit 5% NACl INJ 85 85 SAME AS ABOVE 14.9% KCl INJ 20 cc ampule 40 40 Additive for K+ Correction & maintenance 7.5% NA2CO3 44.6 44.6 HCO3 Additive for GI Losses; Correct Metabolic Acidosis
125. COMMONLY USED PARENTERAL SOLUTIONS SOLNS. Na+ K+ Cl- HCO3- Ca++ Principal Uses 0.9 NaCl 154 154 Correction of Hyponatremia ECF Replacement 0.45NaCl 77 77 Na+ Maintenance; Gastric Fluid Replacement Lactated Ringer’s Solution 130 4 109 28 9 Best ECF Replacement; Correction of Isoosmolar Deficit 5% Dextrose In Water Correction of insensible water loss; Maintenance and Correction of Hyperosmolar Dehydration
