Acid Base Balance Review & Questions II

1. Acid Base BalanceReview & Questions II Ana Corona, MSN, FNP-C Nursing Instructor September 2007

2. Basic Questions • There are three critical questions to keep in mind when attempting to interpret arterial blood gases (ABGs). First Question: Does the patient exhibit acidosis or alkalosis? Second Question: What is the primary problem? Metabolic? or Respiratory? Third Question: Is the patient exhibiting a compensatory state? In order to understand ABG analysis and remember what is abnormal, you need to review what is normal.

3. Remember Definitions • Acidosis (acidemia) occurs when pH drops below 7.35 • Alkalosis (alkalemia) occurs when the pH rises above 7.45 • A primary respiratory problem is determined if the PaC02 is less than 35mmHg (alkalosis) or greater than 45 mmHg (acidosis). • A primary metabolic problem is when the HC03 is less than 22mEq/L (acidosis) or greater than 26mEq/L (alkalosis).

4. Compensation • Our bodies have compensatory mechanisms that assist us to return to a state of homeostasis (equilibrium). • The body attempts to compensate for whatever the primary problem is in an effort to return the acid-base balance to normal.

5. An illustration of COMPENSATION is given below: • A newly diagnosed Type 1 diabetic client has a ‘primary’ problem of metabolic acidosis (pH 7.29; HCO3 16 mEq/L) due to an increase in ketone bodies (ketoacidosis). • The nurse notes that the ABGs show a below normal PaCO2 value (27mmHg) and the client is breathing faster in an attempt to ‘blow off’ the carbon dioxide (CO2:’acid’) to create a respiratory alkalosis, the opposite of metabolic acidosis! • Hint! In order to recognize ‘compensation’ look for a change in the buffering system that was not involved in the ‘primary’ problem.

6. Review the three essential steps of ABG analysis • Number One: Determine if the client is demonstrating an acidotic (remember: pH less than 7.35) or alkalotic (pH greater than 7.45). • Number Two: What is the 'primary problem? If the client is acidotic with aPaC02greater than 45 mmHg it is RESPIRATORY If the client is acidotic with a HC03 less than 22 mEq/L it is METABOLIC! If the client is alkalotic with a PaC02 less than 35 mmHg it is RESPIRATORY! If the client is alkalotic with a HC03 greater than 26 mEq/L it is METABOLIC!

7. ABG analysis • Number Three:Is the client compensating? • Are both components (HCO3 and PaCO2) shifting in the same direction? • Up or down the continuum? • Above or below the normal ranges? • If this is noted, you know that the client’s buffering systems are functioning and are trying to bring the acid-base balance back to normal.

8. ACID BASE PARAMETERS

9. Normal Blood Gas Values

10. 1 case study Jean Thomas is a 25-year-old secretary admitted to the emergency room with diaphoresis, hyperventilation, palpitations, and trembling. Jean tells the nurse that she has been "very upset and nervous" over a poor employment evaluation. A tentative diagnosis of acute anxiety episode is made. Which of the following acid-base imbalances would likely occur as a result of Jean's hyperventilation? A.  Respiratoryacidosis B.  Respiratory alkalosis C.  Metabolic acidosis D.  Metabolic alkalosis

11. Answer to 1 • The intended response is B, since hyperventilation will cause an increased loss of CO2

12. 2 Case Study A client recovering from surgery is difficult to arouse following surgery. The nurse in the PACU has been administering Morphine Sulfate IV to the client for pain. The client’s respiratory rate is 7 per minute with shallow breathing. The patient does not respond to any stimuli! The nurse assesses the ABCs and obtains ABGs STAT! The STAT results come back from the laboratory and show: pH = 7.15 Pa C02 = 68 mmHg HC03 = 22 mEq/L • Compensated Respiratory Acidosis • Uncompensated Metabolic Acidosis • Compensated Metabolic Alkalosis • Uncompensated Respiratory Acidosis

13. 2 case study • The answer is #1 uncompensated respiratory acidosis

14. 3 Case Study • An infant, three weeks old, is admitted to the Emergency Room. The mother reports that the infant has been irritable, difficult to breastfeed and has had diarrhea for the past 4 days. The infant’s respiratory rate is elevated and the fontanels are sunken. The Emergency Room physician orders ABGs after assessing the ABCs. The results from the ABGs come back from the laboratory and show: pH = 7.37 Pa C02 = 29 mmHg HC03 = 17 mEq/L • Compensated Respiratory Alkalosis • Uncompensated Metabolic Acidosis • Compensated Metabolic Acidosis • Uncompensated Respiratory Acidosis

15. 3 • Answer is #3 • Compensated Metabolic Acidosis

16. 4 case study • A client, 5 days post-abdominal surgery, has a nasogastric tube. The nurse notes that the nasogastric tube (NGT) is draining a large amount (900 cc in 2hours) of coffee ground secretions. The client is not oriented to person, place, or time. The nurse contacts the attending physician and STAT ABGs are ordered. The results from the ABGs come back from the laboratory and show: pH = 7.52 Pa C02 = 35 mmHg HC03 = 29 mEq/L • Compensated Respiratory Alkalosis • Uncompensated Metabolic Acidosis • Compensated Metabolic Acidosis • Uncompensated Metabolic Alkalosis

17. 4 • Answer is #4 • Uncompensated Metabolic Alkalosis

18. 5 case study • A client is admitted to the hospital and is being prepared for a craniotomy (brain surgery). The client is very anxious and scared of the impending surgery. He begins to hyperventilate and becomes very dizzy. The client looses consciousness and the STAT ABGs reveal: • The results from the ABGs come back from the laboratory and show: • pH = 7.57 • Pa C02 = 26 mmHg • HC03 = 24 mEq/L • Compensated Metabolic Acidosis • Uncompensated Metabolic Acidosis • Uncompensated Respiratory Alkalosis • Uncompensated Respiratory Acidosis

19. 5 • The answer is #3 • Uncompensated Respiratory Alkalosis

20. 6 case study • A two-year-old is admitted to the hospital with a diagnosis of asthma and respiratory distress syndrome. The father of the infant reports to the nurse that he has observed slight tremors and behavioral changes in his child over the past three days. The attending physician orders routine ABGs following an assessment of the ABCs. The ABG results are: • pH = 7.36 • Pa C02 = 69 mmHg • HC03 = 36 mEq/L • Compensated Respiratory Alkalosis • Uncompensated Metabolic Acidosis • Compensated Respiratory Acidosis • Uncompensated Respiratory Alkalosis

21. 6 • Answer is #3 • Compensated Respiratory Acidosis

22. 7 case study • A young woman, drinking beer at a party, falls and hits her head on the ground. A friend dials "911" because the young woman is unconscious, depressed ventilation (shallow and slow respirations), rapid heart rate, and is profusely bleeding from both ears. • Which primary acid-base imbalance is this young woman at risk for if medical attention is not provided? • metabolic acidosis • metabolic alkalosis • respiratory acidosis • respiratory alkalosis

23. 7 • Correct answer is #3 • Respiratory Acidosis

24. 8 case study • An 11-year old boy is admitted to the hospital with vomiting, nausea and overall weakness. The nurse notes the laboratory results: potassium: 2.9 mEq. • Which primary acid-base imbalance is this boy at risk for if medical attention is not provided? • metabolic acidosis • metabolic alkalosis • respiratory acidosis • respiratory alkalosis

25. 8 • Correct Answer is #2 • Metabolic Alkalosis

26. 9 case study • An elderly gentleman is seen in the emergency department at a community hospital. He admits to taking many tablets of aspirin (salicylates) over the last 24-hour period because of a severe headache. He complains of an inability to urinate. His vital signs are: Temp = 98.5; apical pulse = 92; respiration = 30 and deep. • Which primary acid-base imbalance is the gentleman at risk for if medical attention is not provided? • metabolic acidosis • metabolic alkalosis • respiratory acidosis • respiratory alkalosis

27. 9 • Correct Answer is #1 • Metabolic Acidosis

28. 10 case study • A young man is found at the scene of an automobile accident in a state of emotional distress. He tells the paramedics that he feels dizzy, tingling in his fingertips, and does not remember what happened to his car. Respiratory rate is rapid at 34/minute. • Which primary acid-base disturbance is the young man at risk for if medical attention is not provided? • metabolic acidosis • metabolic alkalosis • respiratory acidosis • respiratory alkalosis

29. 10 • Correct Answer is #4 • Respiratory Alkalosis

30. 11 Review question The client with severe vomiting is at risk for developing: • RESPIRATORY ALKALOSIS WITHOUT DEHYDRATION • METABOLIC ACIDOSIS WITH DEHYDRATION • RESPIRATORY ACIDOSIS WITHOUT DEHYDRATION • METABOLIC ALKALOSIS WITH DEHYDRATION

31. 11 answer • Answer B is correct. With vomiting comes dehydration. When the client is dehydrated, she will have metabolic acidosis. Answers A and C are incorrect because they are respiratory dehydration. Answer D is incorrect because the client will not be in alkalosis with persistent vomiting.

32. 12 Review question AN OBSTETRIC CLIENT IS ADMITTED WITH DEHYDRATION. WHICH IV FLUID WOULD BE MOST APPROPRIATE FOR THE CLIENT? • 0.45 NORMAL SALINE • DEXTROSE 1% IN WATER • LACTATED RINGER'S • DEXTROSE 5% IN .45 NORMAL SALINE

33. 12 answer • Answer A is correct. The best IV fluid for correction of dehydration is normal saline because it is most like normal serum. Dextrose pulls fluid from the cell, lactated Ringer’s contains more electrolytes than the client’s serum, and dextrose with normal saline will also alter the intracellular fluid. Therefore, answers B, C, and D are incorrect.

34. 13 Review Question A patient has taken an overdose of aspirin. Which of the following should a nurse most closely monitor for during acute management of this patient? A: Onset of pulmonary edema B: Metabolic alkalosis C: Respiratory alkalosis D: Parkinson’s disease type symptoms

35. 13 answer • Answer A is correct: Aspirin overdose can lead to metabolic acidosis and cause pulmonary edema development.

36. 14 Review question A patient’s chart indicates a history of hyperkalemia.  Which of the following would you not expect to see with this patient if this condition were acute? A:  Decreased HR B:  Paresthesias C:  Muscle weakness of the extremities D:  Migraines

37. 14 answer • Answer D is correct: choices A - C were symptoms of acute hyperkalemia

38. 15 review question A patient’s chart indicates a history of ketoacidosis.  Which of the following would you not expect to see with this patient if this condition were acute? A:  Vomiting B:  Extreme Thirst C:  Weight gain D:  Acetone breath smell

39. 15 answer • Answer C is correct: • Weight loss would be expected

40. 16 review question Which of the following conditions correlate with the following information:High pHHigh HCO3 High BENeutral PaCO2 • Respiratory alkalosis • Respiratory acidosis • Metabolic acidosis • Metabolic alkalosis

41. 16 answer • The correct answer is D • Metabolic Alkalosis

42. 17 review question Which of the following conditions correlate with the following information:High  pHNeutral HCO3 Neutral BELow PaCO2 • Respiratory alkalosis • Respiratory acidosis • Metabolic acidosis • Metabolic alkalosis

43. 17 answer • The correct answer is A • Respiratory Alkalosis

44. 18 review question Which of the following conditions correlate with the following information:Low  pHLow HCO3 Low BENeutral PaCO2 • Respiratory alkalosis • Respiratory acidosis • Metabolic acidosis • Metabolic alkalosis

45. 18 answer • The correct answer is C • Metabolic Acidosis

46. 19 question Normal values for PaCO2 are considered: • 20-40 mm Hg • 25-30 mm Hg • 30-40 mm Hg • 35-45 mm Hg

47. 19 answer • The correct answer is D • 35 – 45 mmHg

48. 20 question Normal values for HCO3 are considered: • 15-30 mEq/L • 20-35 mEq/L • 22-26 mEq/L • 24-29 mEq/L

49. 20 answer • The correct answer is C • 22-26 mEq/L