Acid-Base Balance

Acid-Base Balance Why is acid-balance carefully regulated? Acid-base balance is carefully regulatedto maintain a normal pH via multiple mechanisms. What is the normal pH in our blood? 7.35-7.45 What is the acid-base balance determined by? Different molecules, like the hydrogen ion (H+), bicarbonate (HCO3), and carbon dioxide (CO2), concentration in body fluids. Acid-base balance involves what three systems? 1. Chemical buffer system (HCO3-H2CO3) 2. Kidneys (HCO3) 3. Lungs (CO2) Think: - The more CO2 we have then ______. (the more acidic the blood is) - The more bicarbonate (HCO3) we have then ______. (the more basic the blood is) •Negative logarithm of the H+ concentration(?) If the H+ are ^ high in number, the pH is _________. [low (acidic)] If the H+ are low in number, the pH is __________. [high (alkaline)] How can acid be eliminated? - By breathing faster by lungs as CO2 gas - By the renal tubules with the regulation of bicarbonate (HCO3– ) (retaining HCO3) By regulating secretion of H+ into the urine. (secrete more H+ in urine) - What is a buffer? It is a chemical that can bind excessive H+ or OH– without a significant change in pH What are the most important plasma-buffering systems? The carbonic acid (H2CO3) – bicarbonate (HCO3) pair. Acid-Base Balance What is the normal ratio of a carbonic acid to a bicarbonate to maintain the pH? And can they increase or decrease? 20 molecules of bicarbonate (base) to 1 molecules of carbonic acid (acid). Bicarbonate and carbonic acid can increase or decrease, but the ratio must be maintained to maintain the pH. Think: Anything lower than <7.35 is_______. (Acidosis) Anything higher than >7.45 is _______. (Alkalosis) When the pH is altered, what two systems can compensate and how? 1. Respiratory system by ^ inc. ventilation to release CO2, or dec. ventilation to retain CO2. 2. Renal system by producing acidic or alkaline urine (regulating the amount of HCO3- and H+ retained or excreted. SLOOOWWW How do you test for acidic or basic blood? First, find pulse (artery) then, draw blood. Obtained by arterial blood gas (ABG) sampling. What is the primary acid and base? Primary acid is CO2.Primary base is HCO3 Define acidosis: Systemic increase in H+ concentration or decrease in bicarbonate (base) Define alkalosis: Systemic decrease in H+ concentration or increase in bicarbonate PaCO2 represents ________. (partial pressure of carbon dioxide in arterial blood) What is the normal PaCO2? 35 to 45 mm Hg (Mercury) What happens when there is an acute rise in PCO2? It will serve as a powerful stimulant to respiration. Acid-Base Balance If the pH of ECF is low, what will the kidney do? - Eliminate H+ in urine - Reabsorb of HCO3 Produce new HCO3 - Arterial Blood Gas Interpretation MEMORIZE What are the normal values of the blood gases below: • pH 7.35-7.45 •PaCO2 35-45 mm Hg •HCO3 21-28 mEq/L •PaO2 80-100 mm Hg •O2 Sat. 95% or greater If the normal PaO2 is 35-45, then what is the range when it’s in acidosis or alkalosis? >45 acidosis; <35 alkalosis If the normal bicarbonate is 21-28, then what is the range when it’s in acidosis or alkalosis? <21 acidosis; >28 alkalosis The PaO2 usually indicates a ________ component. (respiratory) The HCO3 usually indicates a ________ component. (metabolic) Name and describe the 6 categories of acid-base imbalances: 1. •Respiratory acidosis—elevation of pCO2 as a result of ventilation depression 2. •Respiratory alkalosis—depression of pCO2 as a result of hyperventilation 3. •Metabolic acidosis—decrease of HCO3– or an increase in noncarbonic acids 4. •Metabolic alkalosis—elevation of HCO3– usually caused by an excessive loss of metabolic acids 5. •Mixed acidosis 6. •Mixed alkalosis Acid-Base Balance Think: When we are talking about respiratory, we are looking at CO2 levels. When we are talking about metabolic, we are looking at HCO3 levels. Acid-Base pH PCO2 (mm Hg) HCO3 (mEq/L) 7.35-7.45 35-45 21-28 Conditions Normal Respiratory acidosis ↓ ↑ Normal Respiratory alkalosis ↑ ↓ Normal Metabolic acidosis ↓ Normal ↓ Metabolic alkalosis ↑ Normal ↑ Summary What happens to the blood with metabolic acidosis? Decreased bicarbonate low pH (acidosis) What is causes metabolic acidosis? - Increased metabolic acids - Inability of kidneys to excrete acid - Excess loss of bicarbonate via kidneys/GI What are the two clinical causes of metabolic acidosis? 1. Overproduction of Acids 2. Diabetic ketoacidosis Give 5 clinical examples of the overproduction of acids. Acid-Base Balance 1. Diabetic ketoacidosis (DKA): when diabetic is using too much fat (lipids) for energy, they end up with an accumulation of keto bodies (acidic) 2. Starvation ketoacidosis: don’t eat enough carbs 3. Anaerobic metabolism 4. Overdose of ferrous sulfate 5. Renal failure, uremia Give 4 clinical examples of severe body loss of bicarbonate. 1. SEVERE Diarrhea (losing bicarbonate in stool) 2. Pancreatic secretions lost via pancreatic fistulas 3. Excessive acetazolamide (Diamox) or ammonium chloride 4. Renal failure Summary Acid-Base Balance What is one sign/symptom of metabolic acidosis? Kussmaul Respirations (compensating for acidosis by getting rid of CO2) What are the main two physical causes of metabolic acidosis? 1. DKA 2. Severe diarrhea What happens to the blood with metabolic alkalosis? Increased bicarbonate with elevated pH higher than >7.45 What causes metabolic alkalosis? - Increased bicarbonate administration - Excess loss of acid via kidneys/GI - Increased bicarbonate levels by contraction of ECF via hypokalemia & hypochloremia What are the 3 main clinical causes of metabolic alkalosis? 1. Excess base loading: •Antacids•Ringer’s lactate 2. Loss of acid:•Gastric suctioning• Vomiting •Thiazide/loop diuretics 3. Contraction of ECF: Decrease in ECF due to vomiting/NGT suction leads to loss of Cl- and reabsorption of Na+ and Bicarbonate What are the sign/symptom of metabolic alkalosis? - Compensatory Hyperventilation (Lower respiratory rate) Acid-Base Balance - Tremors Muscle cramps Tingling fingers/toes What are the main two physical causes of metabolic alkalosis? 1. Severe vomiting 2. Excessive GI suctioning Summary Metabolic acidosis Metabolic alkalosis Acid-Base Balance Increased H+ = low pH (<7.35) Decreased H+ = high pH (>7.45) Decreased bicarbonate Increased bicarbonate, loss of acid. Severe Diarrhea Severe vomiting Compensation: Heavier breathing Compensation: Lighter breathing causes decreased PCO2 causes increased PCO2 What happens to the blood with respiratory acidosis? Increased CO2 with decreases pH What causes respiratory acidosis? - Hyperventilation - Acute disorders of ventilation - Chronic disorders of ventilation Increased CO2 production What are the main clinical causes of respiratory acidosis? 1. Acute Disorders of Ventilation a. Impaired function of respiratory center in medulla and pons- breathing center (common in overdoses, tumors) b. Lung disease c. Chest injury d. Weakness of respiratory muscles e. Airway obstruction 2. Chronic Disorders of Ventilation a. COPD b. Pulmonary fibrosis What are the signs/symptoms of respiratory acidosis? - Hyperventilation (Hypoxia) - CO2 by lungs What are the main physical causes of respiratory acidosis? Acid-Base Balance - Respiratory Depression (Anesthesia, Overdose, ^ICP) - Airway Obstruction Summary What happens to the blood with respiratory alkalosis? Decrease PCO2 with increased pH How does hyperventilation cause both respiratory alkalosis and acidosis? What causes respiratory alkalosis? - Hyperventilation(dec. CO2) - Central stimulation of respiratory center - Stimulation of peripheral pathways to respiratory center What are the main clinical causes of respiratory alkalosis? - Central Stimulation o Anxiety o Pain o Febrile states o Sepsis o Encephalitis o Salicylate toxicity (stimulate the respiratory center) – Too much aspirin which increases ^ Acid-Base Balance respiratory center, then RR rate increases, then CO2 decreases = alkalosis (RESPIRATORY ALKALOSIS) - Hypoxemia What are the sign/symptom of respiratory alkalosis? - Numbness or tingling in the face, hands, or feet. - Lightheadedness What are the main physical causes of respiratory alkalosis? 1. Hyperventilation Summary Respiratory acidosis Respiratory alkalosis Increased PCO2 Decreased PCO2 Increased carbonic acid Decreased carbonic acid Increased H+ = low pH (<7.35) Decreased H+ = high pH (>7.45) Compensation: Increased bicarbonate Compensation: Decreased bicarbonate When does mixed acidosis or alkalosis occur? Results when 2 or more primary acid-base disorders are present NAMING THE ABNORMAL ABG 1. Last name first •Acidosis or Alkalosis (look at pH) 2. First name next •Respiratory or Metabolic(look at the values of CO2 and HCO3)