Acid-Base, Fluids and Electrolytes

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Acid-Base, Fluids and Electrolytes

  1. 1.  Fluid and Electrolytes  At the end of this lecture, we will be able to:  Discuss the importance of homeostasis.  Enumerate and discuss the importance of laboratory assessment of fluid and electrolyte balance.  Interpret laboratory results of fluids and electrolytes.  correlate clinically
  2. 2.  Acid-Base Balance  Discuss the control of pH in the blood with emphasis on the role of lungs/kidneys  Enumerate and discuss the four major possible abnormalities of acid-base balance  Metabolic vs Respiratory  Acidosis vs Alkalosis  Compensated vs Uncompensated  Correlate clinically
  3. 3.  A delicate balance of fluids, electrolytes, acids and bases is required to maintain good health.  This balance is called Homeostasis.
  4. 4.  Intracellular fluid (ICF) found within the cells of the body  constitutes 2/3 of total body fluid in adults  major cation is potassium   Extracellular fluid (ECF) found outside the cells  accounts of 1/3 of total body fluid  major cation is sodium 
  5. 5.  Osmosis   Solutes   movement of water across cell membranes from less concentrated to more concentrated substances dissolved in a liquid Osmolality  the concentration within a fluid
  6. 6.  Diffusion   Filtration   movement of molecules in liquids from an area of higher concentration to lower concentration fluid and solutes move together across a membrane from area of higher pressure to one of lower pressure Active Transport  substance moves across cell membranes from less concentrated solution to more concentrated requires a carrier and energy.
  7. 7.    Urine Insensible fluid loss Feces
  8. 8.     Sodium Potassium Chloride Phosphate    Magnesium Calcium Bicarbonate Electrolytes are important for: Maintaining fluid balance Contributing to acid-base regulation Facilitating enzyme reactions Transmitting neuromuscular reactions
  9. 9.   Sodium (Na) NV 135-145 mEq/L Potassium (K) NV 3.5 – 5.5 mEq/L Ion-selective electrodes most common method  Atomic absorption spectroscopy reference method   Osmolality NV 275-300mOsm/kg H2O  Freezing point depression, most common method (serum or urine)
  10. 10.   Hypernatremia Conditions causing dehydration and absolute Na excess Hyponatremia Conditions causing loss of Na and increase in body water (dilutional)
  11. 11.   Hyperkalemia  Conditions causing absolute increase in body K and extracellular shift of K Hypokalemia  Conditions causing loss of K, decreased K intake, and intracellular shift of K
  12. 12.  Hyperosmolality (osmolal gap)  Normal: dehydration, high Na, azotemia, DI  Moderately elevated: Ketoacidosis, Renal and lactic acidosis  Markedly elevated: alcohol ingestion and poisoning of selected substances
  13. 13.  Water Distribution  60% of BW  60% ICF and 33% ECF  8% in plasma  freely permeable  Na, K, glucose, urea and protein  balance between intake and body loss
  14. 14.  Sodium Distribution major EC cation 135 to 145 mmol/L relatively impermeable leakage is actively pump out by Na-K ATPase balance intake and loss excessive intake contributes to hypertension massive internal turnover
  15. 15.  Potassium Distribution major IC cation constant tendency to diffuse down its concentration gradient opposed by Na-K ATPase EC concentration is accessible for measurement
  16. 16. Changes in H2O content independent of the amount of solute will alter osmolality  Water Loss  movement from ICF to ECF  stimulation of ADH secretion  stimulates thirst center  ECF volume is directly dependent upon the total sodium content  Sodium Balance: regulated by its renal excretion (GFR, aldosterone); atrial natriuretic hormone and natriuretic factor (cardiac glycosides) which acts against Na-K ATPase 
  17. 17.  Abnormalities:  Combined Water and Sodium Depletion  Pure Water Depletion  Pure Sodium Depletion (Hyponatremia)  Combined Water and Sodium Excess  Pure Water Excess  Pure Sodium Excess (Hypernatremia)
  18. 18.  Hypotonic fluid loss  thirst, dryness of mouth, difficulty of swallowing, weakness, confusion  weight loss, dry mucous membrane, decreased saliva secretion, loss of skin turgor, decreased urine volume  Causes:  Increased Loss: renal, GIT, lungs, skin  Decreased Intake
  19. 19. Isotonic or hypotonic fluid loss  hypertonic loss (excessive sweating)  corresponding decrease in ECF  response: aldosterone, inc. reabsorption, low GFR  increased Hct and plasma protein  reduced ECF volume  peripheral circulatory failure  plasma Na concentration  isotonic loss = decreased  hypotonic loss = increased  Causes: Excessive Loss or Inadequate Intake 
  20. 20. Failure of normal excretion Excessive intake (iatrogenic)
  21. 21. Impairment of water excretion hyponatremia load is shared by ICF and ECF cerebral over-hydration causes: increased intake and decreased excretion
  22. 22. Peripheral edema, dyspnea, pulmonary edema, venous congestion, HPN, effusions, weight gain Causes: Increased Intake, Decreased Excretion mostly has paradoxical hyponatremia due to defect in free water excretion
  23. 23.    Plasma Na is dependent upon relative amounts of Na and water in the plasma Indications for serum Na determination:  dehydration or excessive fluid loss - as a guide to appropriate replacement  on parenteral fluid replacement who are unable to indicate or respond to thirst  with unexplained confusion, abnormal behavior or signs of CNS irritability Correlated with clinical observations
  24. 24.    Balance is controlled by kidneys and GIT related to Hydrogen Ions Kidney: complete reabsorption and active secretion  amount of Na for reabsorption  relative availability of K and H  ability to secrete H  aldosterone concentration  rate of flow of tubular fluid
  25. 25.   GIT: secreted in gastric juice, reabsorb in the SI, secreted in LI in exchange of Na movement between ECF and ICF  influence of insulin  integrity of cell membranes  Na-K ATPase  H ion concentration
  26. 26.       Output exceeds intake inadequate intake is rarely the sole cause increased loss drug therapy redistribution in the ECF and ICF asymptomatic, neuromuscular disturbance, cardiac, renal (impaired concentration), metabolic alkalosis
  27. 27.      Excessive intake if excretion is decreased iatrogenic and parenteral decreased excretion redistribution of ECF and ICF spurious (hemolysis, delayed separation, contamination)
  28. 28.   Hypokalemia  low ST wave  T depression/inversion  prolonged PR interval  prominent U wave Hyperkalemia  peaking of T waves  loss of P waves  abnormal QRS complexes  ventricular fibrillation
  29. 29.  Acid-Base balance is: the regulation of HYDROGEN ions. 
  30. 30.      The acidity or alkalinity of a solution is measured as pH. The more acidic a solution, the lower the pH. The more alkaline a solution , the higher the pH. Water has a pH of 7 and is neutral. The pH of arterial blood is normally between 7.35 and 7.45
  31. 31.  The more Hydrogen ions, the more acidic the solution and the LOWER the pH  The lower Hydrogen concentration, the more alkaline the solution and the HIGHER the pH
  32. 32.  Know what is normal.
  33. 33.  Regulate pH by binding or releasing Hydrogen  Most important buffer system:  Bicarbonate-Carbonic Acid Buffer System  (Blood Buffer systems act instantaneously and thus constitute the body’s first line of defense against acidbase imbalance)
  34. 34.  Lungs  help regulate acid-base balance by eliminating or retaining carbon dioxide  pH may be regulated by altering the rate and depth of respirations  changes in pH are rapid,  occurring within minutes  normal CO2 level  35 to 45 mm Hg
  35. 35.  Kidneys  the long-term regulator of acid-base balance  slower to respond  may take hours or days to correct pH  kidneys maintain balance by excreting or conserving bicarbonate and hydrogen ions  normal bicarbonate level  22 to 26 mEq/L.
  36. 36.     Age  especially infants and the elderly Gender and Body Size  amount of fat Environmental Temperature Lifestyle  stress
  37. 37.     Respiratory Acidosis Respiratory Alkalosis Metabolic Acidosis Metabolic Alkalosis
  38. 38.  Mechanism  Hypoventilation or Excess CO2 Production  Etiology  COPD  Neuromuscular Disease  Respiratory Center Depression  Late ARDS  Inadequate mechanical ventilation  Sepsis or Burns  Excess carbohydrate intake
  39. 39.   Symptoms  Dyspnea, Disorientation or coma  Dysrhythmias  pH < 7.35, PaCO2 > 45mm Hg  Hyperkalemia or Hypoxemia Treatment  Treat underlying cause  Support ventilation  Correct electrolyte imbalance  IV Sodium Bicarb
  40. 40.  Risk Factors and etiology  Hyperventilation due to  extreme anxiety, stress, or pain  elevated body temperature  overventilation with ventilator  hypoxia  salicylate overdose  hypoxemia (emphysema or pneumonia)  CNS trauma or tumor
  41. 41.  Symptoms  Tachypnea or Hyperpnea  Complaints of SOB, chest pain  Light-headedness, syncope, coma, seizures  Numbness and tingling of extremities  Difficult concentrating, tremors, blurred vision  Weakness, paresthesias, tetany  Lab findings  pH above 7.45  CO2 less than 35
  42. 42.  Treatment  Monitor VS and ABGs  Treat underlying disease  Assist client to breathe more slowly  Help client breathe in a paper bag  or apply rebreather mask  Sedation
  43. 43.  Risk Factors/Etiology  Conditions that increase acids in the blood  Renal Failure  DKA  Starvation  Lactic acidosis  Prolonged  Toxins diarrhea (antifreeze or aspirin)  Carbonic anhydrase inhibitors - Diamox
  44. 44.   Symptoms  Kussmaul’s respiration  Lethargy, confusion, headache, weakness  Nausea and Vomiting  Lab:  pH below 7.35  Bicarb less than 22 Treatment  treat underlying cause  monitor ABG, I&O, VS, LOC, NaHCO3
  45. 45.  Risk Factors/Etiology  Acid loss due to  vomiting  gastric suction  Loss of potassium due to  steroids  diuresis  Antacids (overuse of)
  46. 46.   Symptoms  Hypoventilation (compensatory)  Dysrhythmias, dizziness  Paresthesia, numbness, tingling of extremities  Hypertonic muscles, tetany  Lab: pH above 7.45, Bicarb above 26  CO2 normal or increased w/comp  Hypokalmia, Hypocalcemia Treatment  I&O, VS, LOC  give potassium  treat underlying cause
  47. 47.  1. Look at the pH  is the primary problem acidosis (low) or alkalosis (high)  2. Check the CO2 (respiratory indicator)  is it less than 35 (alkalosis) or more than 45 (acidosis)  3. Check the HCO3 (metabolic indicator)  is it less than 22 (acidosis) or more than 26 (alkalosis)  4. Which is primary disorder (Respiratory or Metabolic)?  If the pH is low (acidosis), then look to see if CO2 or HCO3 is acidosis (which ever is acidosis will be primary).  If the pH is high (alkalosis), then look to see if CO2 or HCO3 is alkalosis (which ever is alkalosis is the primary).  The one that matches the pH (acidosis or alkalosis), is the primary disorder.
  48. 48.  The Respiratory system and Renal systems compensate for each other  attempt  ABG’s show that compensation is present when  the   to return the pH to normal pH returns to normal or near normal If the nonprimary system is in the normal range (CO2 35 to 45) (HCO3 22-26), then that system is not compensating for the primary. For example:  In respiratory acidosis (pH<7.35, CO2>45), if the HCO3 is >26, then the kidneys are compensating by retaining bicarbonate.  If HCO3 is normal, then not compensating.
  49. 49. THE END

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