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Acid base balance

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2

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pH

The acidity or alkalinity of a solution is

measured as pH.

The more acidic a solution, the lower the pH.

The more alkaline a solution , the higher the

pH.

Water has a pH of 7 and is neutral. The pH of arterial blood is normally

between 7.35 and 7.45

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Respiratory Regulation

Lungs

help regulated acid-base balance byeliminating or retaining carbon dioxide

pH may be regulated by altering the rate anddepth of respirations

changes in pH are rapid, occurring within minutes

normal CO2 level

35 to 45 mm Hg

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Renal Regulation

Kidneys

the long-term regulator of acid-base balance

slower to respond

may take hours or days to correct pH

kidneys maintain balance by excreting or

conserving bicarbonate and hydrogen ions

normal bicarbonate level

22 to 26 mEq/L.

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Acid-Base Imbalances

Respiratory Acidosis

Respiratory Alkalosis

Metabolic Acidosis

Metabolic Alkalosis

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Respiratory Acidosis

Mechanism

Hypoventilation or Excess CO2 Production

Etiology

COPD

Neuromuscular Disease

Respiratory Center Depression

Late ARDS

Inadequate mechanical ventilation

Sepsis or Burns

Excess carbohydrate intake

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Respiratory Acidosis (cont)

Symptoms

Dyspnea, Disorientation or coma Dysrhythmias

pH < 7.35, PaCO2 > 45mm Hg

Hyperkalemiaor Hypoxemia

Treatment

Treat underlying cause Support ventilation

Correct electrolyte imbalance

IV Sodium Bicarb

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Respiratory Alkalosis

Risk Factors and etiology

Hyperventilation due to extreme anxiety, stress, or pain

elevated body temperature

overventilation with ventilator

hypoxia

salicylate overdose

hypoxemia (emphysema or pneumonia)

CNS trauma or tumor

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Respiratory Alkalosis (cont)

Symptoms

Tachypnea or Hyperpnea

Complaints of SOB, chest pain

Light-headedness, syncope, coma, seizures Numbness and tingling of extremities

Difficult concentrating, tremors, blurred vision

Weakness, paresthesias, tetany Lab findings

pH above 7.45

CO2 less than 35

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Respiratory Alkalosis (cont)

Treatment

Monitor VS and ABGs

Treat underlying disease

Assist client to breathe more slowly

Help client breathe in a paper bag

or apply rebreather mask

Sedation

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Metabolic Acidosis

Risk Factors/Etiology

Conditions that increase acids in the blood

Renal Failure

DKA

Starvation

Lactic acidosis

Prolonged diarrhea Toxins (antifreeze or aspirin)

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Metabolic Acidosis (cont)

Symptoms Kussmauls respiration

Lethargy, confusion, headache, weakness

Nausea and Vomiting

Lab: pH below 7.35

Bicarb less than 22

Treatment treat underlying cause

monitor ABG, I&O, VS, LOC Sodium Bicarb?

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Metabolic Alkalosis

Risk Factors/Etiology Acid loss due to

vomiting

gastric suction

Loss of potassium due to

steroids

diuresis

Antacids (overuse of)

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Metabolic Alkalosis (cont) Symptoms

Hypoventilation (compensatory)

Dysrhythmias, dizziness

Paresthesia, numbness, tingling of extremities

Hypertonic muscles, tetany

Lab: pH above 7.45, Bicarb above 26 CO2 normal or increased w/comp

Hypokalmia, Hypocalcemia

Treatment I&O, VS, LOC

give potassium

treat underlying cause

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Interpreting ABGs

1. Look at the pH

is the primary problem acidosis (low) or alkalosis (high)

2. Check the CO2 (respiratory indicator) is it less than 35 (alkalosis) or more than 45 (acidosis)

3. Check the HCO3 (metabolic indicator) is it less than 22 (acidosis) or more than 26 (alkalosis)

4. Which is primary disorder (Resp. or Metabolic)? If the pH is low (acidosis), then look to see if CO2 or HCO3 is acidosis (which

ever is acidosis will be primary).

If the pH is high (alkalosis), then look to see if CO2 or HCO3 is alkalosis

(which ever is alkalosis is the primary).

The one that matches the pH (acidosis or alkalosis), is the primary disorder.

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Compensation The Respiratory system and Renal systems

compensate for each other

attempt to return the pH to normal

ABGs show that compensation is present when

the pH returns to normal or near normal

If the nonprimary system is in the normal range(CO2 35 to 45) (HCO3 22-26), then that system isnot compensating for the primary.

For example: In respiratory acidosis (pH45), if the HCO3 is >26, then

the kidneys are compensating by retaining bicarbonate.

If HCO3 is normal, then not compensating.

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Thank you