Slide 1

Zoya Minasyan, RN, MSN-Edu

Slide 2

Purpose Maintain a balance between acids and bases to achieve homeostasis: State of equilibrium Health problems lead to imbalance Diabetes mellitus Vomiting and diarrhea Respiratory conditions Chemotherapy- N/V

Slide 3

pH Measure of H + ion concentration Blood is slightly alkaline at pH 7.35 to 7.45. 7.45 is alkalosis.

Slide 4

Range of pH Fig. 17-16. The normal range of plasma pH is 7.35 to 7.45. A normal pH is maintained by a ratio of 1 part carbonic acid to 20 parts bicarbonate.

Slide 5

Regulators of Acid/Base Metabolic processes produce acids that must be neutralized and excreted. Regulatory mechanisms Buffers Respiratory system Renal system

Slide 6

Regulators of Acid/Base Buffers: Act chemically to neutralize acids or change strong acids to weak acids Primary regulators React immediately Cannot maintain pH without adequate respiratory and renal function The buffers in the body include carbonic acidbicarbonate monohydrogen- dihydrogen phosphate intracellular and plasma protein hemoglobin

Slide 7

Regulators of Acid/Base Respiratory system: Eliminates CO 2 Respiratory center in medulla controls breathing. Responds within minutes/hours to changes in acid/base. Increased respirations lead to increased CO 2 elimination decreased CO 2 in blood.

Slide 8

Regulators of Acid/Base When released into circulation, CO 2 enters RBCs and combines with H 2 O to form H 2 CO 3. This carbonic acid dissociates into hydrogen ions and bicarbonate. The free hydrogen is buffered by hemoglobin molecules, and the bicarbonate diffuses into the plasma. In the pulmonary capillaries, this process is reversed, and CO 2 is formed and excreted by the lungs. As a compensatory mechanism, the respiratory system acts on the CO 2 + H 2 O side of the reaction by altering the rate and depth of breathing to blow off (through hyperventilation) or retain (through hypoventilation) CO 2. If a respiratory problem is the cause of an acid-base imbalance (e.g., respiratory failure), the respiratory system loses its ability to correct a pH alteration.

Slide 9

Regulators of Acid/Base Renal system: Eliminates H + and reabsorbs HCO 3 Reabsorption and secretion of electrolytes (e.g., Na +, Cl ) Responds within hours to days

Slide 10

Regulators of Acid/Base The three mechanisms of acid elimination are secretion of small amounts of free hydrogen into the renal tubule, combination of H + with ammonia (NH 3 ) to form ammonium (NH 4 + ), and excretion of weak acids. The body depends on the kidneys to excrete a portion of the acid produced by cellular metabolism. Thus the kidneys normally excrete acidic urine (average pH equals 6). As a compensatory mechanism, the pH of the urine can decrease to 4 and increase to 8.

Slide 11

Alterations in Acid-Base Balance Imbalances occur when compensatory mechanisms fail. Classification of imbalances Respiratory: Affect carbonic acid concentration Metabolic: Affect bicarbonate

Slide 12

Respiratory Acidosis Carbonic acid excess caused by Hypoventilation Respiratory failure Compensation Kidneys conserve HCO 3 and secrete H + into urine.

Slide 13

Respiratory Acidosis Hypoventilation results in a buildup of CO 2 carbonic acid accumulates in the blood Carbonic acid dissociates, liberating H +, and a decrease in pH occurs. If CO 2 is not eliminated from the blood, acidosis results from the accumulation of carbonic acid. In acute respiratory acidosis, the renal compensatory mechanisms begin to operate within 24 hours.

Slide 14

Respiratory Alkalosis Carbonic acid deficit caused by Hyperventilation Hypoxemia from acute pulmonary disorders

Slide 15

Metabolic Acidosis Base bicarbonate deficit caused by Ketoacidosis Lactic acid accumulation (shock) Severe diarrhea Kidney disease Metabolic acidosis (base bicarbonate deficit) occurs when an acid other than carbonic acid accumulates in the body, or when bicarbonate is lost from body fluids. Compensatory mechanisms Compensatory mechanisms Increased CO 2 excretion by lungs Increased CO 2 excretion by lungs Kussmaul respirations (deep and rapid) Kussmaul respirations (deep and rapid) Kidneys excrete acid Kidneys excrete acid

Slide 16

Metabolic Alkalosis Base bicarbonate excess caused by Prolonged vomiting or gastric suction Gain of HCO 3 Compensatory mechanisms Decreased respiratory rate to increase plasma CO 2 Renal excretion of HCO 3

Slide 17

Blood Gas Values Arterial blood gas (ABG) values provide information about Acid-base status Underlying cause of imbalance Bodys ability to regulate pH Overall oxygen status

Slide 18

Interpretation of ABGs Diagnosis in six steps: Evaluate pH. Analyze PaCO 2. Analyze HCO 3 Determine if CO 2 or HCO 3 matches the alteration. Decide if the body is attempting to compensate.

Slide 19

Normal Blood Gas Values Table 17-15. Normal Arterial Blood Gas Values *.

Slide 20

Sample ABG Interpretation Table 17-16. Arterial Blood Gas (ABG) Analysis.

Slide 21

Acid-Base MnemonicROME R espiratory O pposite Alkalosis pH PaCO 2 Acidosis pH PaCO 2 M etabolic E qual Acidosis pH HCO3 Alkalosis pH HCO3

Slide 22

Interpretation of ABGs pH 7.18 PaCO 2 38 mm Hg PaO 2 70 mm Hg HCO 3 15 mEq/L What is this? Metabolic acidosis

Slide 23

Interpretation of ABGs pH 7.58 PaCO 2 35 mm Hg PaO 2 75 mm Hg HCO 3 50 mEq/L What is this? Metabolic alkalosis

Slide 24

A patient with an acid-base imbalance has an altered potassium level. The nurse recognizes that the potassium level is altered because: 1. Potassium is returned to extracellular fluid when metabolic acidosis is corrected. 2. Hyperkalemia causes an alkalosis that results in potassium being shifted into the cells. 3. Acidosis causes hydrogen ions in the blood to be exchanged for potassium from the cells. 4. In alkalosis, potassium is shifted into extracellular fluid to bind excessive bicarbonate. Question 24

Slide 25

Answer Answer: 3 Rationale: Changes in pH (hydrogen ion concentration) will affect potassium balance. In acidosis, hydrogen ions accumulate in the intracellular fluid (ICF), and potassium shifts out of the cell to the extracellular fluid to maintain a balance of cations across the cell membrane. In alkalosis, ICF levels of hydrogen diminish, and potassium shifts into the cell. If a deficit of H + occurs in the extracellular fluid, potassium will shift into the cell. Acidosis is associated with hyperkalemia Alkalosis is associated with hypokalemia.

Slide 26

Case Study 1: Jeri Jeris been on a 3-day party binge. Friends are unable to awaken her. Assessment reveals level of consciousness difficult to arouse. Respiratory rate 8 Shallow breathing pattern Diminished breath sounds 1. What ABGs do you expect? 2. What is your treatment? 26

Slide 27

Case Study 1: Jeri What ABGs do you expect? Respiratory acidosis reflected by pH 45 mm Hg. The HCO 3 will be normal (20-30 mEq/L) if her respiratory depression has lasted less than 24 hours; if longer than 24 hours, the HCO 3 may be elevated as the result of compensation. The PaO 2 may be

Case Study 2: Mayna 1. What ABGs do you expect? Respiratory alkalosis indicated by pH >7.45 and PCO 2

Slide 30

Case Study 3: Allen 17 years old History of Feeling bad Fatigue Constant thirst Frequent urination Blood sugar is 484 mg/dL. Respirations are 28 and deep. Breath has a fruity odor. Lungs are clear. 1. What ABGs do you expect? 2. What is your treatment?

Slide 31

Case Study 3: Allen What ABGs do you expect? A diabetic ketoacidosis is a metabolic acidosis indicated by a pH