Chapter 42 Acid-Base Balance 2021 PDF

Chapter 42 Acid-Base Balance Dr. Athena Watkins Copyright © 2021, Elsevier Inc. All Rights Reserved. Potter & Perry (2021), pages 987-990  Intended Student Learning Describe the proc...

Chapter 42 Acid-Base Balance Dr. Athena Watkins Copyright © 2021, Elsevier Inc. All Rights Reserved. Potter & Perry (2021), pages 987-990  Intended Student Learning Describe the processes that regulate acid-base balance. Interpret acid-base imbalances based on arterial blood gas results. – Respiratory acidosis – Respiratory alkalosis – Metabolic acidosis – Metabolic alkalosis Identify risk factors for acid-base imbalances. Apply the nursing process when caring for patients with acid-base imbalances. Assess your patients with specific acid-base imbalances. Copyright © 2021, Elsevier Inc. All Rights Reserved. Potter & Perry (2021), pages 979  Acid-Base Balance The body maintains a balance between acids & bases for optimal cell function. Acid-base homeostasis is the dynamic interplay of 3 processes: – Acid production (carbonic, metabolic) – Acid buffering – Acid excretion Normal acid-base balance is maintained with acid The human body is production = acid excretion. naturally slightly Acids release hydrogen (H+) ions alkaline , (blood pH 7.4). Bases (alkaline substances) take up H+ The stomach is acidic, The solution is > acidic when there’s an abundance which allows it to digest of H+ present. food. Copyright © 2021, Elsevier Inc. All Rights Reserved. Potter & Perry (2021), pages 987  All body fluids contain buffers & they work within Acid Buffering seconds. Buffers normally keep the blood Buffers are pairs from becoming of chemicals that too acidic when work together to acids that are maintain normal produced by cells pH of body fluids. circulate to the A buffer takes lungs and them up excess kidneys for Major Buffer System in ECF H+ when there excretion. are too many. The HCO3- buffer system consists of a lot of HCO3- & a small amount of A buffer can carbonic acid (20:1 ratio). release H+ when there are Other buffers too few. Hgb, protein buffers, phosphate buffers, cellular & bone buffers  Acid Excretion Excretion of Excretion of Metabolic Carbonic Acid Acids You excrete carbonic acid in the form of CO2 & H2O when you exhale. The kidneys excrete metabolic acids. ↑PaCO2 rises  the chemoreceptors trigger faster & They secrete H+ into the renal tubular fluid, putting HCO3- deeper respirations to excrete the excess. back into the blood at the same time. ↓PaCO2 falls  the chemoreceptors trigger slower & ↑H+ in the blood  renal cells move more H+ ions into the shallower respirations so that more of the CO2 renal tubules for excretion, retaining more HCO3- in the produced by cells remain in the blood & makes up process. the deficit. ↓H+ ions in the blood  renal cells secrete fewer H+ Copyright © 2021, Elsevier Inc. All Rights Reserved. Potter & Perry (2021), page 989  Lab Normal Range in Adult ABG pH 7.35-7.45 PaCO 35-45 mmHg 2 (4.7-6 kPa) HCO3 21-28 mEq/L (21- - 28 mmol/L) PaO2 80-100 mmHg (10.7-13.3 kPa) SaO2 95% - 100% Base -2 to +2 mEq/L Exces (mmol/L) s Copyright © 2021, Elsevier Inc. All Rights Reserved. Potter & Perry (2021), pages 990, TABLE 42.6 Arterial Blood Gas Measures  Respiratory Acidosis Arises from alveolar hypoventilation  lungs not able to excrete CO2  ↑ Carbonic Acid Impaired Neuromuscular Function Chest wall injury Dysfunction of Brainstem Respiratory Control Respiratory depressant drug overdose Chest wall surgery Head injury Impaired Gas Exchange Respiratory failure Acute asthma episode Respiratory muscle fatigue Respiratory muscle weakness Airway obstruction Atelectasis COPD Type A emphysema COPD Type B chronic bronchitis Pneumonia bacterial Copyright © 2021, Elsevier Inc. All Rights Reserved. Potter & Perry (2021), pages 990, TABLE 42.7 Acid-Base Imbalances  Respiratory Acidosis Physical Exam Lab ↓LOC (confusion, lethargy, coma) pH < 7.35 Headache PaCO2 > 45 mmHg (6 kPa) Lightheadedness HCO3- normal if uncompensated or > 28 mEq/L (28 mmol/L) if Dysrhythmias compensated Treatment: treat underlying cause, bronchodilators, O2, non-invasive positive pressure ventilation, naloxone for opioid reversal Copyright © 2021, Elsevier Inc. All Rights Reserved. Potter & Perry (2021), pages 990, TABLE 42.7 Acid-Base Imbalances  Respiratory Alkalosis Arises from alveolar hyperventilation  Stimulation of brainstem respiratory control ↓Carbonic Acid Aspirin overdose Hypoxemia from any cause Gram-negative sepsis Initial part of asthma episode Head injury Pneumonia (PNA) Meningitis Acute pain Anxiety, psychological distress, sobbing Inappropriate mechanical ventilator settings Copyright © 2021, Elsevier Inc. All Rights Reserved. Potter & Perry (2021), pages 990, TABLE 42.7 Acid-Base Imbalances  Respiratory Alkalosis Physical Exam ABG Light-headedness pH > 7.45 Numbness & tingling of fingers, PaCO2 < 35 mmHg (4.7 toes, & circumoral region kPa) ↑RR, ↑ depth HCO3- normal if short Excitement & confusion  lived or uncompensated followed by ↓LOC OR < 21 mEq/L (21 mmol/L) if compensated Dysrhythmias Copyright © 2021, Elsevier Inc. All Rights Reserved. Potter & Perry (2021), pages 990, TABLE 42.7 Acid-Base Imbalances  Metabolic Acidosis Excessive metabolic acids H+ ↑ metabolic acids (High Anion Gap) Loss of bicarbonate (Normal Anion Ketoacidosis (alcoholism, diabetes, starvation) Gap) Hypermetabolic state (burns, severe hyperthyroidism, severe infection) Diarrhea Oliguric renal disease (acute kidney injury, end-stage Pancreatic fistula or intestinal decompression renal disease) Renal tubular acidosis Circulatory shock (lactic acidosis) Anion Gap Normal range 4-12 Ingestion of acid or acid precursors (boric acid, ethylene, mEq/L glycol, methanol) Metabolic acidosis >12mEq/L  Metabolic Acidosis Physical Exam Lab ↓LOC (lethargy, confusion, coma) pH < 7.35 ↑RR & ↑respiratory depth (compensatory PaCO2 normal if uncompensated OR < hyperventilation) 7.35 (4.7 kPa) if compensated Abdominal pain HCO3- < 21 mEq/L (21 mmol/L) Treatment: bicarbonate infusions, ACE inhibitors are used Dysrhythmias to lower K+ levels, Insulin IV for DKA, starvation, restoration of tissue O2 in lactic acidosis, drugs to counteract methanol poisoning or salicylate poisoning Copyright © 2021, Elsevier Inc. All Rights Reserved. Potter & Perry (2021), pages 990, TABLE 42.7 Acid-Base Imbalances  Metabolic Alkalosis ↑↑↑ of HCO3- ↓↓↓ metabolic acids H+ Loss of Metabolic Acid Bicarbonate ↑ aldosterone Excessive administration of sodium Hypokalemia bicarbonate Excessive vomiting Massive blood transfusion (liver converts citrate to HCO3- Mild or moderate ECV Gastric suction deficit (contraction alkalosis) Copyright © 2021, Elsevier Inc. All Rights Reserved. Potter & Perry (2021), pages 990, TABLE 42.7 Acid-Base Imbalances  Metabolic Alkalosis ABG Physical Exam pH > 7.45 Possible excitement & confusion  followed by PaCO2 normal if uncompensated OR > 45 ↓LOC mmHg (6.0 kPa) if compensated Light-headedness HCO3- >Treat Treatment: 28 mEq/L (28 mmol/L) the underlying cause. Numbness & tingling of fingers, toes, & circumoral IV Saline IV K+ replacement region IV Mg2+ replacement IV Chloride infusion Dysrhythmias (may be caused by concurrent IV HCl acid infusion hypokalemia) DC high doses of diuretics. Muscle cramps