1 / 74

Acid-Base Balance Interactive Tutorial

Acid-Base Balance Interactive Tutorial. Emily Phillips MSN 621 Spring 2009 E-mail: emmalemmaRN@hotmail.com All images imported from Microsoft Clipart & Yahoo Image gallery. How to navigate this tutorial:. To advance to the next slide click on the box

ray
Download Presentation

Acid-Base Balance Interactive Tutorial

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Acid-Base Balance Interactive Tutorial Emily Phillips MSN 621 Spring 2009 E-mail: emmalemmaRN@hotmail.com All images imported from Microsoft Clipart & Yahoo Image gallery

  2. How to navigate this tutorial: • To advance to the next slide click on the box • To return to the previous slide click on the box • To return to the Main Menu: click the box • Hover over underlined text for a definition/explanation • To return to the last slide viewed click on the button • Click the for additional information

  3. Objectives: • Define acid base balance/imbalance • Explain the pathophysiology of organs involved in acid base balance/imbalance • Identify normal/abnormal and compensated/uncompensated lab values • Explain symptoms related to acid base imbalances and compensated vs. uncompensated • Appropriate interventions and expected outcomes

  4. Main Menu: Acid-Base Pretest The Buffer Systems Acid-Base Review test Metabolic Distubances Respiratory Disturbances Acid-Base Compensation Diagnostic Lab Values ABG Interpretation & Case Studies

  5. Acid-Base Pretest: • What is the normal range for arterial blood pH? 7.38 – 7.46 7.40 – 7.52 7.35 – 7.45

  6. Acid-Base Pretest: • What 2 extracellular substances work together to regulate pH? Sodium bicarbonate & carbonic acid Carbonic acid & bicarbonate Acetic acid & carbonic acid

  7. Acid-Base Pretest: • Characterize an acid & a base based on the choices below. Acids release hydrogen (H+) ions & bases accept H+ ions. Acids accept H+ ions & bases release H+ ions Both acids & bases can release & accept H+ ions

  8. Acid-Base Pretest: • Buffering is a normal body mechanism that occurs rapidly in response to acid-base disturbances in order to prevent changes in what? HCO3- H2CO3 H+

  9. Acid-Base Pretest: • What are the two systems in the body that work to regulate pH in acid-base balance & which one works fastest? The Respiratory & Renal systems Renal The Respiratory & Renal systems Respiratory The Renal & GI systems Renal

  10. Acid-Base Balance: • Homeostasis of bodily fluids at a normal arterial blood pH • pH is regulated by extracellular carbonic acid (H2CO3) and bicarbonate (HCO3-) • Acids are molecules that release hydrogen ions (H+) • A base is a molecule that accepts or combines with H+ ions

  11. Acids and Bases can be strong or weak: • A strong acid or base is one that dissociates completely in a solution - HCl, NaOH, and H2SO4 • A weak acid or base is one that dissociates partially in a solution -H2CO3, C3H6O3, and CH2O

  12. The Body and pH: Protein Buffer system • Homeostasis of pH is controlled through extracellular & intracellular buffering systems • Respiratory: eliminate CO2 • Renal: conserve HCO3- and eliminate H+ions • Electrolytes: composition of extracellular (ECF) & intracellular fluids (ICF) - ECF is maintained at 7.40 HCO3- Buffer system K+ - H+ Exchange

  13. Quick Review: Click the Boxes An Acid is: A Base is: A donator of H+ ions An acceptor of H+ w/ pH <7.0 ions w/ pH >7.0 Regulated by EC Controlled by EC H2CO3 & HCO3- & IC buffer systems Eliminates CO2 Conserves HCO3- Eliminates H+ ions pH is: pH is: Respiratory System: Renal System:

  14. Respiratory Control Mechanisms: • Works within minutes to control pH; maximal in 12-24 hours • Only about 50-75% effective in returning pH to normal • Excess CO2 & H+ in the blood act directly on respiratory centers in the brain • CO2 readily crosses blood-brain barrier reacting w/ H2O to form H2CO3 • H2CO3 splits into H+ & HCO3- & the H+ stimulates an increase or decrease in respirations

  15. Renal Control Mechanisms: • Don’t work as fast as the respiratory system; function for days to restore pH to, or close to, normal • Regulate pH through excreting acidic or alkaline urine; excreting excess H+ & regenerating or reabsorbing HCO3- • Excreting acidic urine decreases acid in the EC fluid & excreting alkaline urine removes base H+ elimination & HCO3- conservation

  16. Mechanisms of Acid-Base Balance: • The ratio of HCO3- base to the volatile H2CO3 determines pH • Concentrations of volatile H2CO3 are regulated by changing the rate & depth of respiration • Plasma concentration of HCO3- is regulated by the kidneys via 2 processes: reabsorption of filtered HCO3- & generation of new HCO3-, or elimination of H+ buffered by tubular systems to maintain a luminal pH of at least 4.5 Phosphate Buffer system Ammonia Buffer system

  17. Acid-Base Balance Review test: • The kidneys regulate pH by excreting HCO3- and retaining or regenerating H+ TRUE FALSE

  18. Acid-Base Review test: • H2CO3 splits into HCO3- & H+ & it is the H+ that stimulates either an increase or decrease in the rate & depth of respirations. TRUE FALSE

  19. Acid-Base Review test: • Plasma concentration of HCO3- is controlled by the kidneys through reabsorption/regeneration of HCO3-, or elimination of buffered H+ via the tubular systems. TRUE FALSE

  20. Acid-Base Review test: • The ratio of H+ to HCO3- determines pH. TRUE FALSE

  21. Acid-Base Review test: • Secreted H+ couples with filtered HCO3- & CO2 & H2O result. TRUE FALSE

  22. Metabolic Disturbances: • Alkalosis: elevated HCO3- (>26 mEq/L) • Causes include: Cl- depletion (vomiting, prolonged nasogastric suctioning), Cushing’s syndrome, K+ deficiency, massive blood transfusions, ingestion of antacids, etc. • Acidosis: decreased HCO3- (<22 mEq/L) • Causes include: DKA, shock, sepsis, renal failure, diarrhea, salicylates (aspirin), etc. • Compensation is respiratory-related

  23. Metabolic Alkalosis: • Caused by an increase in pH (>7.45) related to an excess in plasma HCO3- • Caused by a loss of H+ ions, net gain in HCO3- , or loss of Cl- ions in excess of HCO3- • Most HCO3- comes from CO2 produced during metabolic processes, reabsorption of filtered HCO3-, or generation of new HCO3- by the kidneys • Proximal tubule reabsorbs 99.9% of filtered HCO3-; excess is excreted in urine

  24. Metabolic Alkalosis Manifestations: • Signs & symptoms (s/sx) of volume depletion or hypokalemia • Compensatory hypoventilation, hypoxemia & respiratory acidosis • Neurological s/sx may include mental confusion, hyperactive reflexes, tetany and carpopedal spasm • Severe alkalosis (>7.55) causes respiratory failure, dysrhthmias, seizures & coma

  25. Treatment of Metabolic Alkalosis: • Correct the cause of the imbalance • May include KCl supplementation for K+/Cl- deficits • Fluid replacement with 0.9 normal saline or 0.45 normal saline for s/sx of volume depletion • Intubation & mechanical ventilation may be required in the presence of respiratory failure

  26. Metabolic Acidosis: • Primary deficit in base HCO3- (<22 mEq/L) and pH (<7.35) • Caused by 1 of 4 mechanisms • Increase in nonvolatile metabolic acids, decreased acid secretion by kidneys, excessive loss of HCO3-, or an increase in Cl- • Metabolic acids increase w/ an accumulation of lactic acid, overproduction of ketoacids, or drug/chemical anion ingestion

  27. Metabolic Acidosis Manifestations: • Hyperventialtion (to reduce CO2 levels), & dyspnea • Complaints of weakness, fatigue, general malaise, or a dull headache • Pt’s may also have anorexia, N/V, & abdominal pain • If the acidosis progresses, stupor, coma & LOC may decline • Skin is often warm & flush related to sympathetic stimulation

  28. Treatment of Metabolic Acidosis: • Treat the condition that first caused the imbalance • NaHCO3 infusion for HCO3- <22mEq/L • Restoration of fluids and treatment of electrolyte imbalances • Administration of supplemental O2 or mechanical ventilation should the respiratory system begin to fail

  29. Quick Metabolic Review: • Metabolic disturbances indicate an excess/deficit in HCO3- (<22mEq/L or >26mEq/L • Reabsorption of filtered HCO3- & generation of new HCO3- occurs in the kidneys • Respiratory system is the compensatory mechanism • ALWAYS treat the primary disturbance

  30. Respiratory Disturbances: • Alkalosis: low PaCO2 (<35 mmHg) • Caused by HYPERventilation of any etiology (hypoxemia, anxiety, PE, pulmonary edema, pregnancy, excessive ventilation w/ mechanical ventilator, etc.) • Acidosis: elevated PaCO2 (>45 mmHg) • Caused by HYPOventilation of any etiology (sleep apnea, oversedation, head trauma, drug overdose, pneumothorax, etc.) • Compensation is metabolic-related

  31. Respiratory Alkalosis: • Characterized by an initial decrease in plasma PaCO2 (<35 mmHg) or hypocapnia • Produces elevation of pH (>7.45) w/ a subsequent decrease in HCO3- (<22 mEq/L) • Caused by hyperventilation or RR in excess of what is necessary to maintain normal PaCO2 levels

  32. Respiratory Alkalosis Manifestations: • S/sx are associated w/ hyperexcitiability of the nervous system & decreases in cerebral blood flow • Increases protein binding of EC Ca+, reducing ionized Ca+ levels causing neuromuscular excitability • Lightheadedness, dizziness, tingling, numbness of fingers & toes, dyspnea, air hunger, palpitations & panic may result

  33. Treatment of Respiratory Alkalosis: • Always treat the underlying/initial cause • Supplemental O2 or mechanical ventilation may be required • Pt’s may require reassurance, rebreathing into a paper bag (for hyperventilation) during symptomatic attacks, & attention/treatment of psychological stresses.

  34. Respiratory Acidosis: • Occurs w/ impairment in alveolar ventilation causing increased PaCO2 (>45 mmHg), or hypercapnia, along w/ decreased pH (<7.35) • Associated w/ rapid rise in arterial PaCO2 w/ minimal increase in HCO3- & large decreases in pH • Causes include decreased respiratory drive, lung disease, or disorders of CW/respiratory muscles

  35. Respiratory Acidosis Manifestations: • Elevated CO2 levels cause cerebral vasodilation resulting in HA, blurred vision, irritability, muscle twitching & psychological disturbances • If acidosis is prolonged & severe, increased CSF pressure & papilledema may result • Impaired LOC, lethargy/coma, paralysis of extremities, warm/flushed skin, weakness & tachycardia may also result

  36. Treatment of Respiratory Acidosis: • Treatment is directed toward improving ventilation; mechanical ventilation may be necessary • Treat the underlying cause • Drug OD, lung disease, chest trauma/injury, weakness of respiratory muscles, airway obstruction, etc. • Eliminate excess CO2

  37. Quick Respiratory Review: • Caused by either low or elevated PaCO2 levels (<35 or >45mmHg) • Watch for HYPOventilation or HYPERventilation; mechanical ventilation may be required • Kidneys will compensate by conserving HCO3- & H+ • REMEMBER to treat the primary disturbance/underlying cause of the imbalance

  38. Compensatory Mechanisms: • Adjust the pH toward a more normal level w/ out correcting the underlying cause • Respiratory compensation by increasing/decreasing ventilation is rapid, but the stimulus is lost as pH returns toward normal • Kidney compensation by conservation of HCO3- & H+ is more efficient, but takes longer to recruit

  39. Metabolic Compensation: • Results in pulmonary compensation beginning rapidly but taking time to become maximal • Compensation for Metabolic Alkalosis: • HYPOventilation (limited by degree of rise in PaCO2) • Compensation for Metabolic Acidosis: • HYPERventilation to decrease PaCO2 Begins in 1-2hrs, maximal in 12-24 hrs

  40. Respiratory Compensation: • Results in renal compensation which takes days to become maximal • Compensation for Respiratory Alkalosis: • Kidneys excrete HCO3- • Compensation for Respiratory Acidosis: • Kidneys excrete more acid • Kidneys increase HCO3- reabsorption

  41. DIAGNOSTIC LAB VALUES & INTERPRETATION

More Related