3125 Week 2 Acid-Base Balance PDF

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Acid base...

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Acid-Base Balance Why is acid-balance carefully regulated? Acid-base balance is carefully regulatedto maintain a normal pH via multiple mechanisms. What is the normal pH in our blood? 7.35-7.45 What is the acid-base balance determined by? Different molecules, like the hydrogen ion (H+), bicarbonate (HCO3), and carbon dioxide (CO2), concentration in body fluids. Acid-base balance involves what three systems? 1. Chemical buffer system (HCO3-H2CO3) 2. Kidneys (HCO3) 3. Lungs (CO2) Think: -

The more CO2 we have then ______. (the more acidic the blood is)

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The more bicarbonate (HCO3) we have then ______. (the more basic the blood is)

•Negative logarithm of the H+ concentration(?) If the H+ are ^ high in number, the pH is _________. [low (acidic)] If the H+ are low in number, the pH is __________. [high (alkaline)] How can acid be eliminated? -

By breathing faster by lungs as CO2 gas

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By the renal tubules with the regulation of bicarbonate (HCO3– ) (retaining HCO3) By regulating secretion of H+ into the urine. (secrete more H+ in urine)

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What is a buffer? It is a chemical that can bind excessive H+ or OH– without a significant change in pH What are the most important plasma-buffering systems? The carbonic acid (H2CO3) – bicarbonate (HCO3) pair.

Acid-Base Balance What is the normal ratio of a carbonic acid to a bicarbonate to maintain the pH? And can they increase or decrease? 20 molecules of bicarbonate (base) to 1 molecules of carbonic acid (acid). Bicarbonate and carbonic acid can increase or decrease, but the ratio must be maintained to maintain the pH. Think: Anything lower than 7.45 is _______. (Alkalosis) When the pH is altered, what two systems can compensate and how? 1. Respiratory system by ^ inc. ventilation to release CO2, or dec. ventilation to retain CO2. 2. Renal system by producing acidic or alkaline urine (regulating the amount of HCO3- and H+ retained or excreted. SLOOOWWW How do you test for acidic or basic blood? First, find pulse (artery) then, draw blood. Obtained by arterial blood gas (ABG) sampling. What is the primary acid and base? Primary acid is CO2.Primary base is HCO3 Define acidosis: Systemic increase in H+ concentration or decrease in bicarbonate (base) Define alkalosis: Systemic decrease in H+ concentration or increase in bicarbonate PaCO2 represents ________. (partial pressure of carbon dioxide in arterial blood) What is the normal PaCO2? 35 to 45 mm Hg (Mercury) What happens when there is an acute rise in PCO2? It will serve as a powerful stimulant to respiration.

Acid-Base Balance If the pH of ECF is low, what will the kidney do? - Eliminate H+ in urine -

Reabsorb of HCO3 Produce new HCO3

Arterial Blood Gas Interpretation MEMORIZE What are the normal values of the blood gases below: • pH

7.35-7.45

•PaCO2

35-45 mm Hg

•HCO3

21-28 mEq/L

•PaO2

80-100 mm Hg

•O2 Sat.

95% or greater

If the normal PaO2 is 35-45, then what is the range when it’s in acidosis or alkalosis? >45 acidosis;

7.45 What causes metabolic alkalosis? -

Increased bicarbonate administration

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Excess loss of acid via kidneys/GI

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Increased bicarbonate levels by contraction of ECF via hypokalemia & hypochloremia

What are the 3 main clinical causes of metabolic alkalosis? 1. Excess base loading: •Antacids•Ringer’s lactate 2. Loss of acid:•Gastric suctioning• Vomiting •Thiazide/loop diuretics 3. Contraction of ECF: Decrease in ECF due to vomiting/NGT suction leads to loss of Cl- and reabsorption of Na+ and Bicarbonate What are the sign/symptom of metabolic alkalosis? -

Compensatory Hyperventilation (Lower respiratory rate)

Acid-Base Balance -

Tremors Muscle cramps

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Tingling fingers/toes

What are the main two physical causes of metabolic alkalosis? 1. Severe vomiting 2. Excessive GI suctioning

Summary

Metabolic acidosis

Metabolic alkalosis

Acid-Base Balance Increased H+ = low pH (7.45)

Decreased bicarbonate

Increased bicarbonate, loss of acid.

Severe Diarrhea

Severe vomiting

Compensation: Heavier breathing

Compensation: Lighter breathing

causes decreased PCO2

causes increased PCO2

What happens to the blood with respiratory acidosis? Increased CO2 with decreases pH What causes respiratory acidosis? -

Hyperventilation

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Acute disorders of ventilation

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Chronic disorders of ventilation Increased CO2 production

What are the main clinical causes of respiratory acidosis? 1. Acute Disorders of Ventilation a. Impaired function of respiratory center in medulla and pons- breathing center (common in overdoses, tumors) b. Lung disease c. Chest injury d. Weakness of respiratory muscles e. Airway obstruction 2. Chronic Disorders of Ventilation a. COPD b. Pulmonary fibrosis What are the signs/symptoms of respiratory acidosis? - Hyperventilation (Hypoxia) - CO2 by lungs What are the main physical causes of respiratory acidosis?

Acid-Base Balance -

Respiratory Depression (Anesthesia, Overdose, ^ICP)

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Airway Obstruction

Summary

What happens to the blood with respiratory alkalosis? Decrease PCO2 with increased pH How does hyperventilation cause both respiratory alkalosis and acidosis? What causes respiratory alkalosis? -

Hyperventilation(dec. CO2)

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Central stimulation of respiratory center

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Stimulation of peripheral pathways to respiratory center

What are the main clinical causes of respiratory alkalosis? - Central Stimulation o Anxiety o Pain o Febrile states o Sepsis o Encephalitis o Salicylate toxicity (stimulate the respiratory center) – Too much aspirin which increases ^

Acid-Base Balance respiratory center, then RR rate increases, then CO2 decreases = alkalosis (RESPIRATORY ALKALOSIS) -

Hypoxemia

What are the sign/symptom of respiratory alkalosis? -

Numbness or tingling in the face, hands, or feet.

- Lightheadedness What are the main physical causes of respiratory alkalosis? 1. Hyperventilation Summary

Respiratory acidosis

Respiratory alkalosis

Increased PCO2

Decreased PCO2

Increased carbonic acid

Decreased carbonic acid

Increased H+ = low pH (7.45)

Compensation: Increased bicarbonate

Compensation: Decreased bicarbonate

When does mixed acidosis or alkalosis occur? Results when 2 or more primary acid-base disorders are present NAMING THE ABNORMAL ABG 1. Last name first •Acidosis or Alkalosis (look at pH) 2. First name next •Respiratory or Metabolic(look at the values of CO2 and HCO3)...