BIOCHEM_LB1_ACID-BASE BALANCE.pdf

form. Therefore, the addition of acid or base will barely affect the pH of a buffered solution as long as the COURSE OUTLINE acidic or...

form. Therefore, the addition of acid or base will barely affect the pH of a buffered solution as long as the COURSE OUTLINE acidic or basic forms of the buffer are not depleted. I. BUFFERS II. BLOOD GAS ANALYSIS A. Henderson-Hasselbach Equation II. BLOOD GAS ANALYSIS Important diagnostic tool to determine: A. Components of Acid Base Status Acid-base balance B. Acid Base Markers Oxygenation status C. Acid Base Regulation Abnormalities in respiration and III. RESPIRATORY AND METABOLIC DISORDERS IV. ABG ANALYSIS A. COMPONENTS OF ACID-BASE STATUS A. Interpretation of Arterial Blood pH - measures the blood's acidity Gas Analysis Normal range: 7.35 - 7.45 B. Steps to ABG Interpretation C. ABG Analysis Normal ph value: 7.4 V. ACID-BASE COMPENSATION Overall H+ from both respiratory and A. Uncompensated metabolic factors B. Partially Compensated C. Fully Compensated pCO2 - partial pressure of carbon dioxide in the VI. RESPIRATORY ACIDOSIS blood VII. RESPIRATORY ALKALOSIS Normal range 35-45 mmHg VIII. METABOLIC ACIDOSIS A. ANION GAP Snapshot of adequacy of alveolar IX. METABOLIC ALKALOSIS ventilation HCO3 - the amount of bicarbonate in the blood ACID-BASE BALANCE Normal range 22- 26 mEq/L I. ACID - BASE DEFINITION B. ACID-BASE MARKERS BUFFERS Bicarbonate - carbonic acid buffer equation Certain solutions can resist drastic changes in pH when small quantities of acids and bases are added to them. Such solutions are called BUFFERS. Mixture of a weak acid and a salt containing its conjugate base or a weak base and a salt containing its conjugate acid. C. ACID-BASE REGULATION A. HENDERSON-HASSELBALCH EQUATION FOR SOLUTIONS Regulated by the lungs and the kidneys The Henderson–Hasselbalch equation predicts that in order to change the pH of a buffered solution by one point, either the acidic or basic form of the buffer must be brought to a concentration of 1/10 that of the other BIOCHEMISTRY LAB 1: ACID-BASE BALANCE DR. ESPIRITU, A. DATE: 09/04/2024 PHYSIOLOGIC MECHANISMS OF ACID-BASE REGULATION A. INTERPRETATION OF ARTERIAL RESPIRATORY: BLOOD GAS ANALYSIS Normal Values Exhalation of Carbon dioxide: Changes in pH: 7.35-7.45 the rate and depth of breathing can alter pCO2: 35 - 45 mmHg the pH of body fluids within a couple of НСО2: 22 - 26 mEg/L minutes. Evaluate each component as Acidic or Alkalotic With increased ventilation, more CO2 pH: exhaled. When CO2 levels decrease, the below 7.35 - acidic reaction is driven to the left, hydrogen above 7.45 - alkalotic concentration falls, and blood pH pCO2: increases. below 35 mmHg - alkalotic If ventilation is slower than normal, less above 45 mmHg - acidic carbon dioxide is exhaled. When CO2 HCO3: levels increase, the reaction is driven to below 22 mEq/L - acidic the right, the hydrogen concentration above 26 mEq/L - alkalotic increases, the blood pH decreases. METABOLIC: B. FOUR STEPS IN BASIC ABG INTERPRETATION Only way to eliminate non volatile acids is 1. Evaluate pH and determine the overall to excrete hydrogen ions in urine. PCT status of the body and collecting ducts of the kidneys secrete 2. Evaluate the respiratory status hydrogen ions into the tubular fluid for 3. Evaluate the metabolic status excretion. 4. Determine which regulatory system is In the PCT, Sodium hydrogen antiporters responsible for the imbalance by checking secrete Hydrogen ions as they reabsorb to see which component sodium ions. HCO3(bicarbonate), produced by dissociation of H2CO3(carbonic acid) inside intercalated cells crosses the basolateral membrane and then diffuses to peritubular capillaries (bicarbonate produced then contributes to alkalinity). Excretion and reabsorption in the kidneys is regulated depending on the body's acid base state. III. RESPIRATORY AND METABOLIC DISORDERS Table 2: ABG Analysis pic RESPIRATORY DISORDERS Increased Carbon dioxide (CO2): Respiratory acidosis Decreased Carbon dioxide (CO2): Respiratory Alkalosis METABOLIC DISORDERS Increased Bicarbonate (HCO3): Metabolic alkalosis Decreased Bicarbonate (HCO3): Metabolic acidosis Table 3: Practice on ABG analysis PREPARED BY: BATCH 2028 1D 2 BIOCHEMISTRY LAB 1: ACID-BASE BALANCE DR. ESPIRITU, A. DATE: 09/04/2024 V. ACID-BASE COMPENSATION Level of Oxygenation - Determine level of oxygenation (arterial When an acid-base imbalance exists, OVER TIME, samples only) the body attempts to compensate. Uncompensated Standard measurement level of oxygenation: Partially Compensated Normal: 80-100 mmHg Fully Compensated Mild hypoxemia: 60-80 mmHg Moderate hypoxemia: 40-60 mmHg A. UNCOMPENSATED Severe hypoxemia: less than 40 mmHg The alternate system has not yet started to adjust (acute condition), and the pH remains abnormal SpO2 or saturation measure of oxygen - Can be determined very rapidly using Example: pulse oximeters but it doesn't translate to pH : 7.30 - A the values above. pCO2 : 60 - A Normal: 95% and above HCO3 : 25 - N Desaturation: 95% and below Answer: Uncompensated Respiratory Acidosis VI. RESPIRATORY ACIDOSIS B. PARTIAL COMPENSATION It may be caused (commonly) by sedation or coma, The alternate system is starting to correct the respiratory muscle weak- ness/fatigue, airways acid-base balance by trying to bring the pH back obstruction or (rarely) lung restriction. within normal limits, but has not yet succeeded. Excessive CO2 retention Example Causes: pH : 7.34 - A Airway obstruction pCO2 : 59 - A Depression of respiratory drive HCO3 : 28 - B Sedatives, analgesics Head trauma Answer: Partially Compensated Respiratory Respiratory muscle weakness resulting Acidosis from muscle disease or chest wall abnormalities C. FULLY COMPENSATED Decreased lung surface area participating The alternate system has corrected the acid-base in gas exchange disorder over time (chronic condition). Compensation: H+ excretion and HCO3- Example reabsorption by the kidney pH : 7.36 - N ( but slightly A) pCO2 : 58 - A VII. RESPIRATORY ALKALOSIS HCO3 : 31 - B Or hyperventilation may be caused by anxiety, brain Answer: Fully Compensated Compensated lesions, salicylates, acute asthma, pulmonary embolism or liver failure. Acidosis Table 4: Practice Activity on Compensation Status Excessive CO2 loss due to hyperventilation Causes: CNS injury: brainstem lesions, salicylate overdose, Reye's Syndrome, hepatic encephalopathy Aggressive mechanical ventilation Anxiety, fear or pain Hypoxia Fever Congestive heart failure PREPARED BY: BATCH 2028 1D 3 BIOCHEMISTRY LAB 1: ACID-BASE BALANCE DR. ESPIRITU, A. DATE: 09/04/2024 Compensation: The kidney compensates by High anion gap – increase in organic acids. reducing the amount of new HCO3- generated and (mnemonic: MUDPILES) by excreting HCO3-. Methanol Uremia VIII. METABOLIC ACIDOSIS Diabetic Ketoacidosis May be caused by retention of excess acids of Paraldehyde metabolic origin (diabetic, renal, lactic) or loss of Isoniazid, Iron alkali as in renal tubular lesions, or pancreatic Lactic Acidosis fistula. Ethylene Glycol, Ethanol Salicylates Excessive HCO3 loss, or acid gain Normal Anion Gap – defects in bicarbonate loss. Causes: (mnemonic: HARDUP) Diabetic ketoacidosis Sepsis/shock Hyperalimentation - formation of different Diarrhea (fluid losses below gastric alimentary canals on the GI tracts leading sphincter) to ion loss. Renal Failure Acetazolamide - carbonic acid anhydride Poison ingestion inhibitor Starvation Renal tubular acidosis Dehydration Diarrhea The plasma anion gap is used mainly in Utero-pelvic shunt diagnosing different causes of metabolic Post-hypocapnia acidosis. In metabolic acidosis, plasma HCO3 is reduced. Anion gap computation: Compensation: Increased breathing rate to lower Subtract the concentration of bicarbonate pCO2- hyperventilation. Maximal compensation is and chloride ions from the concentration of completed within 12-24 hours. sodium [Na+ – (HCO3 + Cl)]. IX. METABOLIC ALKALOSIS May be caused by loss of acid through vomiting, volume contraction associated with diuretic therapy or by ingestion of alkali (e.g. a high fruit diet). HCO3 retention, or loss of extracellular acid Causes ○ Gl losses above gastric sphincter ○ Vomiting ○ Nasogastric suction ○ Antacids Figure 4: Metabolic acidosis associated with normal and/or ○ Diuretic therapy causing increased plasma ion gap. electrolyte loss Compensation: Breathing rate decreases to increase pCO2- hypoventilation. Maximal A. ANION GAP compensation is completed within 12-24 hours. Anion gap is the difference between cations and Reference(s): anions in the system. 1. Dr. A. Espiritu (2024). Lecture and Powerpoint 2 types of anion gap: Presentation. High anion gap (HAGMA) 2. Bishop, M. L., Fody, E. P., Siclen, C. V. & Mistler, J. M. (2022), Clinical Chemistry Principles, Techniques, and Normal anion gap (NAGMA) Correlations 9th Edition 3. Lippincott_s Illustrated Reviews Biochemistry, 6th Edition 4. Respiratory-Diseases-and-Management-by-Mcluckie PREPARED BY: BATCH 2028 1D 4