acid-base balance

compensation

can be partial or full partial: Body tries to compensate for pH change Parameter that does not match the pH is moving in the opposite direction With partial compensation the pH will NOT be within normal limits full: If the body has compensated fully the pH WILL be within normal limits

15. The nurse analyzes the results of a patients arterial blood gases (ABGs). Which finding would require immediate action? a. The bicarbonate level (HCO3) is 31 mEq/L. b. The arterial oxygen saturation (SaO2) is 92%. c. The partial pressure of CO2 in arterial blood (PaCO2) is 31 mm Hg. d. The partial pressure of oxygen in arterial blood (PaO2) is 59 mm Hg.

d. The partial pressure of oxygen in arterial blood (PaO2) is 59 mm Hg. All the values are abnormal, but the low PaO2 indicates that the patient is at the point on the oxyhemoglobin dissociation curve where a small change in the PaO2 will cause a large drop in the O2 saturation and a decrease in tissue oxygenation. The nurse should intervene immediately to improve the patients oxygenation.

pH - 7.45 PaCO2 - 45 HCO3- - 25

normal

pH - 7.30 PaCO2 - 25 mm Hg HCO3- - 16 mEq/L

pH < 7.35 = acidosis PaCO2 < 35 mm Hg indicates respiratory alkalosis HCO3- < 22mEq/L indicates metabolic acidosis CO2 doesn't match, indicates compensation, now partial compensation metabolic acidosis, partially compensated

full compensation

pH is normal If the body has compensated fully the pH WILL be within normal limits

partial compensation

pH, CO2, and HCO3 are all off Body tries to compensate for pH change Parameter that does not match the pH is moving in the opposite direction With partial compensation the pH will NOT be within normal limits pH - 7.30 PaCO2 - 25 mm Hg HCO3- - 16 mEq/L pH < 7.35 = acidosis PaCO2 < 35 mm Hg indicates respiratory alkalosis HCO3- < 22mEq/L indicates metabolic acidosis CO2 doesn't match pH, indicates compensation, now partial compensation

HCO3 is normal in __________ acidosis/alkalosis

respiratory (unless partially compensating, then opposite)

PaCO2 greater than 45

respiratory acidosis (if pH low)

pH - 7.49 PaCO2 - 30 HCO3- - 24

respiratory alkalosis

PaCO2 less than 35

respiratory alkalosis (if pH high)

acid base regulation - renal system

takes hours to 2 - 3 days (slowest) Excretes H+ into the renal tubule Combines H+ with ammonia IF KIDNEYS NOT WORKING, YOU HAVE TO WATCH OUT FOR ALK/ACIDOSIS Excretion of weak acids Acidosis: reabsorb HCO3 and eliminate H+ pH of blood increases and pH of urine decreases ALK K+ - DECREASED DKA - K+ HIGH, BLOOD IS ACIDIC, FIX IT BY GIVING INSULIN, MOVING K+ INTO CELLS W/ INSULIN, MOVING H+ IONS OUT OF CELLS INTO BLOOD, RAISING PH

acid base regulation - Respiratory system

takes minutes to hours to work BLOWING OFF ACID Excrete CO2 and water - When CO2 is expelled, it leads to less H+ - KIDNEYS HAVE TO DEAL WITH NON-H ATTACHED ACIDS - Acidosis: increased resp rate and depth to correct - Alkalosis: hypoventilation to correct (THEYRE ORIGINALLY BREATHING TOO MUCH)

Normal PaCO2

35-45 mmHg

metabolic acidosis compensation

CO2 excretion by lungs HYPERVENTILATION

metabolic alkalosis compensation

CO2 retention by the lungs hypoventilation

Respiratory alkalosis

- Increased CO2 excretion Causes: -HYPERVENTILATION - Anxiety Hypoxia - Exercise - heavy - Fever - Stimulated resp. center (from brain injury or tumor) - Overvenitilation with mechanical vents - pain Compensation: HCO3 excretion by kidneys clinical manifestations: Dizzy Lightheaded Confusion Tachycardia Nausea, vomiting, GI pain Tetany, tingling, numbness Hyperreflexia Hyperventilation - Blown off too much acid

acid-base imbalances

-Respiratory acidosis -Respiratory alkalosis -Metabolic acidosis -Metabolic alkalosis

ABG interpretation

1. Start with pH Acidosis/Alk 2. Look at CO2 Opposite of pH w/ resp, bicarb can be normal until we start to compensate 3. Next, HCO3 Metabolic is kidneys, use bicarb to see what youre in 4. Does the CO2 or HCO3 match the alteration of the pH? ROME = respiratory opposite, metabolic equal

Normal HCO3

22-26 mEq/L

normal blood pH (for adults)

7.35-7.45

acid base regulation - buffer systems

Buffer Systems - work in seconds - CAN RUN OUT OF BUFFERS, THEN LUNGS AND KIDNEYS HAVE TO TAKE OVER -Change strong acids into weaker acids, bind, or neutralize effects Buffer systems in body: - H2CO3/HCO3- - HPO42-/H2PO4- - Amino acids - Hemoglobin H2CO3/HCO3 buffer system is main/quickest system to deal with changes in pH

respiratory alkalosis compensation

HCO3 excretion by kidneys

respiratory acidosis compensation

HCO3 retention by kidneys

respiratory alkalosis primary cause

HYPERventilation

respiratory acidosis primary cause

HYPOventilation

CO2 is _________ in respiratory alkalosis

INCREASED EXCRETION

Metabolic Acidosis

Loss of base or gain of acid; LOW BICARB Caused by - Ketoacidosis - Starvation - Lactic acidosis - Renal failure - Shock - causes renal failure - aspirin overdose - High fat diet - due to ketones - Severe diarrhea Compensation: CO2 excretion by lungs Renal system reabsorbs HCO3 & Na, secrets Cl in acidosis

pH: 7.29 CO2: 38 mm Hg WNL HCO3: 18 mEq/L Bicarb low

Metabolic Acidosis

pH: 7.50 CO2: 40 mm Hg HCO3: 34 mEq/L

Metabolic Alkalosis

pH - 7.30 PaCO2 - 35 HCO3- - 20

Metabolic acidosis

pH - 7.48 PaCO2 - 44 HCO3- - 30

Metabolic alk

pH - 7.48 PaCO2 - 38 HCO3- - 30

Metabolic alkalosis

pH - 7.50 PaCO2 - 30 HCO3- - 18

Partially comp metab alk

pH - 7.25 PaCO2 - 32 HCO3- - 18

Partially comp metabolic acid

pH - 7.30 PaCO2 - 49 HCO3- - 30

Partially comp resp acidosis

pH - 7.30 PaCO2 - 50 HCO3- - 34

Partially comp resp acidosis

metabolic acidosis causes

Primary Cause: Addition of large amounts of fixed acids to body fluids; Caused by - Ketoacidosis - Starvation - Lactic acidosis - Renal failure - Shock - causes renal failure - aspirin overdose - High fat diet - due to ketones - Severe diarrhea Contributing Causes: Lactic acidosis (circulatory failure), Ketoacidosis (diabetes, starvation), Phosphates and sulfates (Renal dz), Acid ingestion (salicylates), Secondary to respiratory alkalosis, Adrenal insufficiency

respiratory acidosis causes

Primary Cause: Hypoventilation (causes hypercapnia); - COPD - MECHANICAL - PARALYSIS OF DIAPHRAGM - ASTHma - Atalaxtisis - after surgery, this is why we make people use IS IS make ph level go up - Sedatives - narcotics - Pneumonia - Muscle weakness - Chest wall abnormality - Brain trauma - Bronchitis - Emphasema - Pulmonary edema - Pulmonary emolism Contributing Causes: COPD, Pulmonary dz, Drugs, Obesity, Mechanical asphyxia, Sleep Apnea

respiratory alkalosis causes

Primary cause: Hyperventilation (causes hypocapnia); - Anxiety Hypoxia - Exercise - heavy - Fever - Stimulated resp. center (from brain injury or tumor) - Overvenitilation with mechanical vents - pain Contributing Causes: Overventilation on a ventilator, Response to acidosis, Bacteremia, Thyrotoxicosis, Fever, Hepatic failure, Response to hypoxia, Hysteria

CO2 is _________ in respiratory acidosis

RETAINED

pH: 7.31 CO2: 54mm Hg High CO2 HCO3: 25 mEq/L Normal bicarb

Respiratory Acidosis

pH: 7.52 CO2: 27 mm Hg HCO3 24 mEq/L

Respiratory Alkalosis

<7.35 pH

acidosis

1. To evaluate the effectiveness of ordered interventions for a patient with ventilatory failure, which diagnostic test will be most useful to the nurse? a. Chest x-ray b. Oxygen saturation c. Arterial blood gas analysis d. Central venous pressure monitoring

c. Arterial blood gas analysis Arterial blood gas (ABG) analysis is most useful in this setting because ventilatory failure causes problems with CO2 retention, and ABGs provide information about the PaCO2 and pH. The other tests may also be done to help in assessing oxygenation or determining the cause of the patients ventilatory failure.

17. A patient in metabolic alkalosis is admitted to the emergency department, and pulse oximetry (SpO2) indicates that the O2 saturation is 94%. Which action should the nurse take next? a. Administer bicarbonate. b. Complete a head-to-toe assessment. c. Place the patient on high-flow oxygen. d. Obtain repeat arterial blood gases (ABGs).

c. Place the patient on high-flow oxygen. Although the O2 saturation is adequate, the left shift in the oxyhemoglobin dissociation curve will decrease the amount of oxygen delivered to tissues, so high oxygen concentrations should be given. Bicarbonate would worsen the patients condition. A head-to-toe assessment and repeat ABGs may be implemented. However, the priority intervention is to give high-flow oxygen.

HCO3 less than 22

metabolic acidosis

patient who had a transverse colectomy for diverticulosis 18 hours ago has nasogastric suction and is complaining of anxiety and incisional pain. The patients respiratory rate is 32 breaths/minute and the arterial blood gases (ABGs) indicate respiratory alkalosis. Which action should the nurse take first? a. Discontinue the nasogastric suction. b. Give the patient the PRN IV morphine sulfate 4 mg. c. Notify the health care provider about the ABG results. d. Teach the patient how to take slow, deep breaths when anxious.

b. Give the patient the PRN IV morphine sulfate 4 mg. The patients respiratory alkalosis is caused by the increased respiratory rate associated with pain and anxiety. The nurses first action should be to medicate the patient for pain. Although the nasogastric suction may contribute to the alkalosis, it is not appropriate to discontinue the tube when the patient needs gastric suction. The health care provider may be notified about the ABGs but is likely to instruct the nurse to medicate for pain. The patient will not be able to take slow, deep breaths when experiencing pain.

38. The nurse in the emergency department receives arterial blood gas results for four recently admitted patients with obstructive pulmonary disease. Which patient will require the most rapid action by the nurse? a. 22-year-old with ABG results: pH 7.28, PaCO2 60 mm Hg, and PaO2 58 mm Hg b. 34-year-old with ABG results: pH 7.48, PaCO2 30 mm Hg, and PaO2 65 mm Hg c. 45-year-old with ABG results: pH 7.34, PaCO2 33 mm Hg, and PaO2 80 mm Hg d. 65-year-old with ABG results: pH 7.31, PaCO2 58 mm Hg, and PaO2 64 mm Hg

a. 22-year-old with ABG results: pH 7.28, PaCO2 60 mm Hg, and PaO2 58 mm Hg The pH, PaCO2, and PaO2 indicate that the patient has severe uncompensated respiratory acidosis and hypoxemia. Rapid action will be required to prevent increasing hypoxemia and correct the acidosis. The other patients also should be assessed as quickly as possible but do not require interventions as quickly as the 22- year-old.

paco2 is normal in __________ acidosis/alkalosis

metabolic (unless partially compensating, then opposite)

HCO3 greater than 26

metabolic alkalosis

metabolic alkalosis causes

Severe vomiting GI suctioning - put residuals back in patient Diuretics - urinating more K+ deficit Excess NaCHO3 intake Hyperaldosteronism Massive infusions of whole blood due to citrate conc - binds to calcium Excessive antiacid intake -Calcium binds to acid - PPIs can cause alk

pH

a measure of H+ ion concentration

15. A patient who is lethargic and exhibits deep, rapid respirations has the following arterial blood gas (ABG) results: pH 7.32, PaO2 88 mm Hg, PaCO2 37 mm Hg, and HCO3 16 mEq/L. How should the nurse interpret these results? a. Metabolic acidosis b. Metabolic alkalosis c. Respiratory acidosis d. Respiratory alkalosis

a. Metabolic acidosis The pH and HCO3 indicate that the patient has a metabolic acidosis. The ABGs are inconsistent with the other responses.

>7.45 pH

alkalosis

3. A diabetic patients arterial blood gas (ABG) results are pH 7.28; PaCO2 34 mm Hg; PaO2 85 mm Hg; HCO3 18 mEq/L. The nurse would expect which finding? a. Intercostal retractions b. Kussmaul respirations c. Low oxygen saturation (SpO2) d. Decreased venous O2 pressure

b. Kussmaul respirations Kussmaul (deep and rapid) respirations are a compensatory mechanism for metabolic acidosis. The low pH and low bicarbonate result indicate metabolic acidosis. Intercostal retractions, a low oxygen saturation rate, and a decrease in venous O2 pressure would not be caused by acidosis.

21. Four hours after mechanical ventilation is initiated for a patient with chronic obstructive pulmonary disease (COPD), the patients arterial blood gas (ABG) results include a pH of 7.51, PaO2 of 82 mm Hg, PaCO2 of 26 mm Hg, and HCO3 of 23 mEq/L (23 mmol/L). The nurse will anticipate the need to a. increase the FIO2. b. increase the tidal volume. c. increase the respiratory rate. d. decrease the respiratory rate.

d. decrease the respiratory rate. The patients PaCO2 and pH indicate respiratory alkalosis caused by too high a respiratory rate. The PaO2 is appropriate for a patient with COPD and increasing the respiratory rate and tidal volume would further lower the PaCO2.

19. The laboratory has just called with the arterial blood gas (ABG) results on four patients. Which result is most important for the nurse to report immediately to the health care provider? a. pH 7.34, PaO2 82 mm Hg, PaCO2 40 mm Hg, and O2 sat 97% b. pH 7.35, PaO2 85 mm Hg, PaCO2 45 mm Hg, and O2 sat 95% c. pH 7.46, PaO2 90 mm Hg, PaCO2 32 mm Hg, and O2 sat 98% d. pH 7.31, PaO2 91 mm Hg, PaCO2 50 mm Hg, and O2 sat 96%

d. pH 7.31, PaO2 91 mm Hg, PaCO2 50 mm Hg, and O2 sat 96% These ABGs indicate uncompensated respiratory acidosis and should be reported to the health care provider. The other values are normal or close to normal.