Most Important Buffer system Bicarbonate-carbonic acid buffer system Controlled by lungs & kidneys Aeorobic metabolism = to forms of acid respiratory acid (carbonic acid) metabolic acids In order to maintain proper pH balance, the body attempts to maintain a ratio of 20:1 (bicarb to carbonic acid)
BE of -8 represents a deficit of base=metabolic acidosis BE of +10 representsan excess of base=metabolic alkalosis
Metabolic Acidosis Deficit HCO3 Common in cases of kidney disease and diabetes Respiratory Acidosis Excess HCO3 Caused by hypoventilation Metabolic Alkalosis Excess HCO3 Caused by diarrhea, steroid or diuretic therapy. Respiratory Alkalosis Deficit HCO3 Caused by hyperventilation Acid-Base Imbalances
Compensation When there is an imbalance in one parameter of the buffer system (bicarbonate-kidneys) – carbonic acid (lungs) the other tries to compensate for it by causing the opposite imbalance Goal: Restore the 20:1 ratio & return the pH back to the acceptable range 7.35-7.45
ABG Interpretation: Final Step Determine if compensation is present and to what extent When compensation is present, you will see two imbalances The question-Which is the primary problem & which imbalance is due to compensation
Compensation The Clue: pH If the pH is leaning toward acidosis or alkalosis then the parameter with the matching imbalance is the primary problem & the other is due to compensation
Compensation: Example Pt has chronic pulmonary problems & is in a chronic respiratory acidosis. His kidneys will compensate by retaining bicarbonate Creating a metabolic alkalosis to balance his chronic respiratory acidosis
Compensation pH 7.30 acidosis PCO2 70 respiratory acidosis HCO3 30 mild metabolic alkalosis Interpretation Respiratory acidosis with partial compensation by the kidneys. The kidneys have only begun to compensate, because the pH is not back to acceptable limits yet
Supplementary Resources Handout: “Interpreting Arterial Blood Gases” Nursing Article ”Perfecting your acid-base balancing act: How to detect and correct acid-base disorders”
Client diagnosis: bacterial pneumoniaABGs: pH 7.24, PCO2 65 mmHg & HCO3- 24 mEq/L Antibiotics and O2 started. What is a priority nursing intervention?
Mrs. Mendoza Which assessment data indicate that this client has impaired gas exchange? 75-years-old H/O emphysema Adm with Pneumonia Decreased urine output Lethargy Decreased chest excursion hypotension
Mrs. Mendoza Which of the following ABG values indicates that this client is a CO2 retainer? PaCO2 = 40 mm Hg PaCO2 = 60 mm Hg Bicarbonate = 42 PaO2 = 60 mm Hg
Mrs. Mendoza Which of the following ABGs most likely indicate that she is having a negative response to the administration of oxygen. (next slide) Baseline ABG’s pH 7.36 PaCO2 60 mm Hg Pa02 52 mmHg Bicarbonate 42 mEq/L
Mrs Mendoza Based on your answer from the last slide, is the client’s respiratory acidosis compensated or uncompensated? Explain your answer. Which immediate interventions are needed for this client.
Mrs Mendoza Later in the shift, you note that his oxygen is set at 5 L/minute. The client says that he asked the nursing assistant to turn up his oxygen because he was havng trouble breathing. What actions, if any, should you take at this time
Mr. Henderson: H/O Cellulites What is the patients acid base imbalance? T 101 F 90/60 SOB Diarrhea 2 days pH 7.30 pCO2 28 Pa02 88 HCO3 17
Mr Williams HCO3 level of 17 mEq/L is a result of:
The nurse, admitting a patient with diabetes, believes the patient is attempting to correct an acidotic condition. Which of the following did this nurse most likely observe while assessing this patient?
Slow methodical respirations Deep rapid respirations Change in level of consciousness Intact extraocular movements
The nurse is caring for a patient with metabolic acidosis. The nurse realizes that which of the following laboratory values might be altered for this patient?
The nurse is providing discharge instructions to a patient with respiratory alkalosis. Which of the following statements indicates the patient understands the instructions?
“I will not take my Lasix without a potassium supplement.” “I will not use Mylanta 5-6 times a day like I used to.” “I will take a stress management class or seek counseling.” “I will call my MD the next time I have diarrhea for a few days.”