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ACID BASE BALANCE Spring 2010 WHAT YOU WILL LEARN Definition of Acid-Base Balance Deference between regulation of buffers, respirations and renal system What acidosis is and the Difference between Metabolic and Respiratory What alkalosis is and the Difference between Metabolic and Respiratory Complications and diseases associated with both processes KEY TERMS WHAT IS ACID BASE BALANCE Acid-Base Balance refers to homeostasis of hydrogen ion concentration in body fluids Expressed as pH Acids Bases Health problems that may lead to an imbalance PH AND HYDROGEN ION CONCENTRATION Lower the pH Higher the ? Heath Issues that can cause decrease in pH Higher the pH Lower the ? Heath issues that can cause increase in pH Normal pH of blood 7.35 to 7.45 (arterial) Normal pH of blood 7.32 to 7.42 (venous) Critical Values of pH ACID-BASE REGULATION Buffer Systems Respiratory System Renal System BUFFER SYSTEM What is a Buffer? Fastest acting and primary regulator of Acidbase balance 3 types of chemical buffers Buffers can not work with out proper function of what systems BICARBONATE BUFFER Bicarbonate is found in Extra-cellular and intracellular fluid Controls small fluctuation in pH Responds immediately Mainly buffers what 2 fluids Assisted by what organs PHOSPHATE BUFFER Found in intra-cellular fluid as bicarbonates. Control small fluctuation in pH Responds Quickly Effective in Renal tubules, due to high levels of phosphates PROTEIN BUFFER Most abundant buffer in the body Found in ICF as hemoglobin and ECF as albumin and globulins Works rapid Works along same lines of bicarbonate system RESPIRATORY REGULATION Helps maintain pH Second line of defense Responds with in minutes Temporary Relies on Kidneys for long term regulation RESPIRATORY CO2 levels in blood regulated by Lungs Receptors in brain Medulla sense Ph changes Rate and Depth of Breathing changed to compensate Low pH = faster or deeper breaths to eliminate more CO2 from lungs; CO2 blood levels in blood drop and pH increases RESPIRATORY High pH levels Respirations slow and shallow Reduces CO2 elimination Lower pH RESPIRATORY PaCO2 (partial pressure of Arterial CO2 in arterial blood) Used to assess effectiveness of ventilation PaCO2 levels reflect CO2 in the blood. Normal levels 35-45 mm Hg RENAL SYSTEM FOR REGULATION Slowest of all regulating systems Can permanently adjust Blood pH Considered most powerful Kidneys can reabsorb acids and bases and excrete them in urine Kidneys produce bicarbonate to replenish Kidneys regulate bicarbonate Normal levels of bicarbonate 22-26 mEq/L in ABG Three mechanism of acid eliminations RENAL 1. 2. 3. Secretion of small amounts of free hydrogen in renal tubule Combination of hydrogen with ammonia to form ammonium Excretion of weak acids RENAL To much Acid or not enough Base ph drops – kidneys reabsorb sodium bicarb Hydrogen phosphate and ammonia excreted by kidneys Urine more Acidic (Normal Acidic level is 6pH) Bicarb levels rise to normal levels and ph Increases RENAL More base and less acid pH rises Kidneys excrete bicarb retain hydrogen Urine becomes alkaline, Bicarb levels drop and pH decreases IMBALANCES Occur with compensatory mechanism fail Acidosis is excess of hydrogen ions and arterial pH of less that 7.35 Alkalosis is excess of base mainly bicarb in ECF caused by increase of pH greater than 7.45 ROME Respiratory Opposite Metabolic Equal RESPIRATORY OPPOSITE Respiratory Acidosis level pH < that 7.35 PaCO2 is > 45 mm Hg Respiratory Alkalosis pH > than 7.45 PaCO2 is < 35 mm Hg METABOLIC EQUAL Metabolic Acidosis Levels pH is < 7.35 HCO3 < 24 mEq/L Metabolic Alkalosis pH is >7.35 HCO3 > 28 mEq/L RESPIRATORY ACIDOSIS Occurs whenever there is hypoventilation Common Causes include COPD Over sedation Chest Wall abnormality (obesity) Severe Pneumonia Atelectasis Respiratory Muscle Weakness (Gilliain-Barre syndrome) Mechanical hypoventilation CLINICAL MANIFESTATIONS Neurologic Cardiovascular Gastrointestinal Neuromuscular Respiratory DIAGNOSTIC FINDINGS pH < 7.35 PaCo2 > 45mm Hg HCO3 is normal if uncompensated HCO3 is elevated if compensated Hyperkalemia THERAPEUTIC MANAGEMENT NURSING DIAGNOSIS Treatment of underlying cause Improved Ventilation Nursing Diagnosis Ineffective breathing Patterns Impaired Gas Exchange Medications Bronchodilators Antibiotics Agents used to decrease viscosity of secretions Anticoagulants and thrombolytic to prevent emboli RESPIRATORY ALKALOSIS Caused by Hyperventilation as result of pulmonary disorders Mechanical over ventilation Hypoxia Pulmonary Emboli Anxiety Fear Pain Exercise Fever CLINICAL MANIFESTATIONS Cardiovascular Respiratory Neurologic Gastrointestinal Neuromuscular Respiratory CLINICAL FINDINGS pH > 7.45 PaCO2 < 35mm Hg HCO3 normal if uncompensated HCO3 decreased if compensated Urine pH > 6 Hypokalemia Hypocalcemia THERAPEUTIC MANAGEMENT NURSING DIAGNOSIS Therapeutic Management Treatment of underlying cause Re-breathe CO2 Re-breather Mask or paper bag O2 if patient is Hypoxic Nursing Diagnosis Medication Sedatives to control Hyperventilation Antianxiety Me METABOLIC ACIDOSIS Base bicarbonate loss from body fluids or occurs when other acid other than Carbonic Acid accumulates Either way Bicarbonate is deficient Very rarely occurs spontaneously Usually occurs accompanied by other problems CLINICAL MANIFESTATIONS Neurologic Cardiovascular Gastrointestinal Neuromuscular Respiratory CLINICAL FINDINGS pH < than 7.35 Remember in Metabolic you look at HCO3 HCO3 < 22 mEq/L PaCO2 is normal if uncompensated PaCO2 is decreased in compensated Hyperkalemia EKG Changes THERAPEUTIC MANAGEMENT NURSING DIAGNOSIS Correct Underlying Problem Hydration Nutrients Electrolytes Administration of Sodium Bicarb or Sodium lactate Administration of N/S Reg. Insulin and potassium for DKA Nursing Diagnosis METABOLIC ALKALOSIS Loss of acid or gain on bicarbonate – Which in turn causes Increase pH and Increase in HCO3 Conditions that cause Alkalosis Gastric suction, Prolonged vomiting Ingestion of bicarbonate bases (baking soda antacids) Diuretic Therapy Potassium Deficit CLINICAL MANIFESTATIONS Respiratory Cardiovascular Gastrointestinal Neuromuscular Respiratory CLINICAL FINDINGS pH > 7.45 Remember HCO3 is the focus HCO3 > 26 mEq/L PaCO2 is normal uncompensated PaCO2 is elevated if compensated Urine pH is >6 if compensated Hypokalemia Hypocalcemia Hyponatremia and Hypochloremia THERAPEUTIC MANAGEMENT NURSING DIAGNOSIS Correct Underlying Problem Provide sufficient chloride to enhance renal absorption of sodium and excretion of HCO3 and restore normal fluid balance Nursing Diagnosis ABG INTERPRETATION Step One Assess the pH to determine if the blood is within normal range, alkalotic or acidotic. If it is above 7.45, the blood is alkalotic. If it is below 7.35, the blood is acidotic. ABG’S Step Two If the blood is alkalotic or acidotic, we now need to determine if it is caused primarily by a respiratory or metabolic problem. To do this, assess the PaCO2 level. Remember that with a respiratory problem, as the pH decreases below 7.35, the PaCO2 should rise. If the pH rises above 7.45, the PaCO2 should fall. Compare the pH and the PaCO2 values. If pH and PaCO2 are indeed moving in opposite directions, then the problem is primarily respiratory in nature. ABG’S Step Three Finally, assess the HCO3 value. Recall that with a metabolic problem, normally as the pH increases, the HCO3 should also increase. Likewise, as the pH decreases, so should the HCO3. Compare the two values. If they are moving in the same direction, then the problem is primarily metabolic in nature. ABG’S pH PaCO2 HCO3 Respiratory Acidosis Normal Respiratory Alkalosis Normal Metabolic Acidosis Normal Metabolic Alkalosis Normal TEST OURSELVES Jane Doe is a 45-year-old female admitted to the nursing unit with a severe asthma attack. She has been experiencing increasing shortness of breath since admission three hours ago. Her arterial blood gas result is as follows: Clinical Laboratory PATIENT: DOE, JANE DATE: 6/4/03 18:43 pH 7.22 PaCO2 55 HCO3- 25 Follow the steps: 1. Assess the pH. It is low (normal 7.35-7.45); therefore, we have acidosis. 2. Assess the PaCO2. It is high (normal 35-45) and in the opposite direction of the pH. 3. Assess the HCO3. It has remained within the normal range (22-26). ANSWER Acidosis is present (decreased pH) with the PaCO3 being increased, reflecting a primary respiratory problem. For this patient, we need to improve the ventilation status by providing oxygen therapy, mechanical ventilation, pulmonary toilet or by administering bronchodilators. ANOTHER CHANCE John Doe is a 55-year-old male admitted to your nursing unit with a recurring bowel obstruction. He has been experiencing intractable vomiting for the last several hours despite the use of antiemetic. Here is his arterial blood gas result: Clinical Laboratory PATIENT: DOE, JOHN DATE: 3/6/03 08:30 pH 7.50 PaCO2 42 HCO3 - 33 Follow the three steps again: 1. Assess the pH. It is high (normal 7.35-7.45), therefore, indicating alkalosis. 2. Assess the PaCO2. It is within the normal range (normal 35-45). 3. Assess the HCO3. It is high (normal 22-26) and moving in the same direction as the pH. ANSWER Alkalosis is present (increased pH) with the HCO3 increased, reflecting a primary metabolic problem. Treatment of this patient might include the administration of I.V. fluids and measures to reduce the excess base. COMPENSATION The bodies attempt to return to normal state using the opposite system pH is out of balance because of a respiratory disorder, it will be the renal system that makes the corrections to balance the body pH renal system is to blame for the pH disorder, the respiratory system will have to compensate Complete compensation returns the pH balance to normal. There are times when the imbalance is too large for compensation to return the pH to normal. This is called incomplete compensation. NURSING SCHOOL SURVIVAL RULES When in doubt, wash your hands. The correct answer is either "hand washing" or "patent airway." If it moves, ambulate it. If it doesn't move, turn and reposition it Q2H. Remember the 11th Commandment: Thou shalt not cross thy sterile field. The instructor is ALWAYS right. See Rule #5.
