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Acid-Base Balance and Imbalance

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  1. Acid-Base Balanceand Imbalance James Barnett, RN, MSN Clinical Educator – Neuroscience PCC Vanderbilt University Medical Center May 2007

  2. Definitions • pH • Measurement of how alkaline or acid a substance is • Chemistry • Neutral ph = 7 • pH < 7 is acid • pH > 7 is alkaline • Normal human blood pH is slightly alkaline at 7.35 – 7.45

  3. Definitions • An Acid is… • A molecule that can donate a H+ ion • Examples: • H2O  H+ + OH- • H2CO3  H+ + HCO3- • An acid can be weak, moderate, or strong depending on its pH • Weaker acids are closer to 7 • Stronger acids are closer to 1

  4. Definitions • A Base or alkali is… • A molecule that can accept a H+ ion • Examples: • H+ + OH- H2O • H+ + HCO3-  H2CO3 • A base can be weak, moderate, or strong depending on its pH • Weaker bases are closer to pH 7 • Stronger bases are closer to pH 14

  5. An Important Equilibrium Equation H2O + CO2 H2CO3  H+ + HCO3- Water plus carbon dioxide equals carbonic acid which is broken down by carbonic anhydrase into a hydrogen ion and bicarbonate.

  6. Types of Acids • Volatile acids • Easily move from liquid to gas state • Within the body • Lung can remove • H2CO3 + renal enzyme  H2O + CO2 (both of which are exhaled) • Carbon dioxide is therefore considered an acid KEY CONCEPT: As CO2 rises, there is more acid  respiratory acidosis KEY CONCEPT: As CO2 drops, there is less acid  respiratory alkalosis

  7. Types of Acids • Nonvolatile acids • Cannot be changed to gas state • Within the body • Must be removed by the kidneys (metabolic) • Examples • Keto acids • Lactic acids

  8. Acid-Base Imbalance

  9. Acid Imbalance • Too much CO2 leads to decreased pH and an acid condition • Too little CO2 leads to increased pH and an alkaline condition • PaCO2 • Amount of CO2 dissolved in the blood • Good indicator of respiratory and ventilatory function

  10. Base Imbalance • Major base in body is bicarbonate (HCO3-) • Regulated by the kidneys (metabolic) • Too little HCO3- causes decrease in pH and acid conditions • Too much HCO3- causes increase in pH and alkaline conditions

  11. More definitions • Acidemia – condition where blood is more acid than normal (pH < 7.35) • Alkalemia – condition where blood is more alkaline than normal (pH > 7.45) • Acidosis – the process causing acidemia • Alkalosis – the process causing alkalemia

  12. Respiratory Imbalances • Respiratory mechanisms involve either • Retention of excess carbon dioxide • Retention of insufficient carbon dioxide • Over- or Under-ventilation or respiration abnormalities are the main causes of this imbalance

  13. Metabolic Imbalances • Metabolic mechanisms involve • Renal function alteration • Production of acidic metabolic products • Loss of acid from the body

  14. pH PaCO2 HCO3- PaO2 7.35 – 7.45 35 – 45 mmHg 22 – 26 mEq/L 80 – 100 mmHg The Normal’s

  15. The Abnormal’s • Respiratory Acidosis • Respiratory Alkalosis • Metabolic Acidosis • Metabolic Alkalosis

  16. pH < 7.35 PaCO2 > 45 Alveolar Hypoventilation CNS depression or disease Ventilatory/respiratory dysfunction Acute infections Signs and Symptoms Dyspnea Restlessness Confusion/lethargy Dysrhythmias Headache Treatment Increase ventilation Treat the cause Respiratory Acidosis

  17. pH > 7.45 PaCO2 < 35 Alveolar Hyperventilation Anxiety Pain Fever Thyrotoxicosis CNS lesions Improper vent management, hypoxia Pulmonary embolus Signs and Symptoms Light headedness Confusion Muscle spasm / parasthesias Dysrhythmias / palpitations Sweating Dry mouth Blurred vision Treatment Slow down breathing Paper bag breathing if anxiety or fear is cause Treat the cause! Respiratory Alkalosis

  18. pH < 7.35 HCO3- < 22 mEq/L Causes Increased acids from Anaerobic metabolism Abn metabolic process (DKA, lactic acidosis) Starvation ASA or other acid ingestion Excess HCO3- loss Diarrhea Renal Failure Intestinal Fistulae Signs and Symptoms Headache Confusion/lethargy Stupor/coma Weakness Kussmaul respiration N/V Dysrhythmias Flushing Treatment Treat the cause!!! Give Bicarbonate Dialysis for renal failure Metabolic Acidosis

  19. pH > 7.45 HCO3- > 28 Cause Increased base Excessive use of bicarb Lactate from dialysis Excessive antacid ingestion Acid loss Vomiting/Gastric suctioning Hypo- chloremia -kalemia Diuretics Large volume blood transfusion Signs and Symptoms Muscle spasms/tetany/seizure Dizziness Disorientation/lethargy/coma Weakness N/V Depressed respiratory drive Treatments Treat the cause!!!! Increase respirations Metabolic Alkalosis

  20. Finished • You have finished this in-service on Acid-Base Balance and Imbalance. • Continue with the next lesson titled: • Compensated and Uncompensated Blood Gas Analysis