ACID BASE BALANCESpring 2010

WHAT YOU WILL LEARN

Definition of Acid-Base Balance Deference between regulation of buffers,

respirations and renal system What acidosis is and the Difference between

Metabolic and Respiratory What alkalosis is and the Difference between

Metabolic and Respiratory Complications and diseases associated with

both processes

KEY TERMS

WHAT IS ACID BASE BALANCE

Acid-Base Balance refers to homeostasis of hydrogen ion concentration in body fluids

Expressed as pH

Acids

Bases

Health problems that may lead to an imbalance

PH AND HYDROGEN ION CONCENTRATION Lower the pH Higher the ?

Heath Issues that can cause decrease in pH

Higher the pH Lower the ?

Heath issues that can cause increase in pH

Normal pH of blood 7.35 to 7.45 (arterial)

Normal pH of blood 7.32 to 7.42 (venous)

Critical Values of pH

ACID-BASE REGULATION

Buffer Systems

Respiratory System

Renal System

BUFFER SYSTEM

What is a Buffer?

Fastest acting and primary regulator of Acid-base balance

3 types of chemical buffers

Buffers can not work with out proper function of what systems

BICARBONATE BUFFER

Bicarbonate is found in Extra-cellular and intra-cellular fluid

Controls small fluctuation in pH

Responds immediately

Mainly buffers what 2 fluids

Assisted by what organs

PHOSPHATE BUFFER

Found in intra-cellular fluid as bicarbonates.

Control small fluctuation in pH

Responds Quickly

Effective in Renal tubules, due to high levels of phosphates

PROTEIN BUFFER

Most abundant buffer in the body

Found in ICF as hemoglobin and ECF as albumin and globulins

Works rapid

Works along same lines of bicarbonate system

RESPIRATORY REGULATION

Helps maintain pH Second line of defense Responds with in minutes Temporary Relies on Kidneys for long term regulation

RESPIRATORY

CO2 levels in blood regulated by Lungs Receptors in brain Medulla sense Ph changes Rate and Depth of Breathing changed to

compensate Low pH = faster or deeper breaths to

eliminate more CO2 from lungs; CO2 blood levels in blood drop and pH increases

RESPIRATORY

High pH levels

Respirations slow and shallow

Reduces CO2 elimination

Lower pH

RESPIRATORY

PaCO2 (partial pressure of Arterial CO2 in arterial blood)

Used to assess effectiveness of ventilation

PaCO2 levels reflect CO2 in the blood.

Normal levels 35-45 mm Hg

RENAL SYSTEM FOR REGULATION

Slowest of all regulating systems Can permanently adjust Blood pH Considered most powerful Kidneys can reabsorb acids and bases and

excrete them in urine Kidneys produce bicarbonate to replenish Kidneys regulate bicarbonate Normal levels of bicarbonate 22-26 mEq/L in

ABG Three mechanism of acid eliminations

RENAL

1. Secretion of small amounts of free hydrogen in renal tubule

2. Combination of hydrogen with ammonia to form ammonium

3. Excretion of weak acids

RENAL

To much Acid or not enough Base

ph drops – kidneys reabsorb sodium bicarb

Hydrogen phosphate and ammonia excreted by kidneys

Urine more Acidic (Normal Acidic level is 6pH)

Bicarb levels rise to normal levels and ph Increases

RENAL

More base and less acid pH rises Kidneys excrete bicarb retain

hydrogen Urine becomes alkaline, Bicarb levels drop

and pH decreases

IMBALANCES

Occur with compensatory mechanism fail Acidosis is excess of hydrogen ions and

arterial pH of less that 7.35 Alkalosis is excess of base mainly bicarb in

ECF caused by increase of pH greater than 7.45

ROMERespiratory Opposite Metabolic Equal

RESPIRATORY OPPOSITE

Respiratory Acidosis level pH < that 7.35 PaCO2 is > 45 mm Hg

Respiratory Alkalosis pH > than 7.45 PaCO2 is < 35 mm Hg

METABOLIC EQUAL

Metabolic Acidosis Levels pH is < 7.35 HCO3 < 24 mEq/L

Metabolic Alkalosis pH is >7.35 HCO3 > 28 mEq/L

RESPIRATORY ACIDOSIS

Occurs whenever there is hypoventilation Common Causes include

COPD Over sedation Chest Wall abnormality (obesity) Severe Pneumonia Atelectasis Respiratory Muscle Weakness (Gilliain-Barre

syndrome) Mechanical hypoventilation

CLINICAL MANIFESTATIONS

Neurologic

Cardiovascular

Gastrointestinal

Neuromuscular

Respiratory

DIAGNOSTIC FINDINGS

pH < 7.35

PaCo2 > 45mm Hg

HCO3 is normal if uncompensated

HCO3 is elevated if compensated

Hyperkalemia

THERAPEUTIC MANAGEMENTNURSING DIAGNOSIS Treatment of underlying cause Improved Ventilation

Nursing Diagnosis Ineffective breathing Patterns Impaired Gas Exchange

Medications Bronchodilators Antibiotics Agents used to decrease viscosity of secretions Anticoagulants and thrombolytic to prevent

emboli

RESPIRATORY ALKALOSIS

Caused by Hyperventilation as result of pulmonary disorders

Mechanical over ventilation Hypoxia Pulmonary Emboli Anxiety Fear Pain Exercise Fever

CLINICAL MANIFESTATIONS Cardiovascular

Respiratory

Neurologic

Gastrointestinal

Neuromuscular

Respiratory

CLINICAL FINDINGS pH > 7.45

PaCO2 < 35mm Hg

HCO3 normal if uncompensated

HCO3 decreased if compensated

Urine pH > 6

Hypokalemia

Hypocalcemia

THERAPEUTIC MANAGEMENTNURSING DIAGNOSIS

Therapeutic Management Treatment of underlying cause Re-breathe CO2 Re-breather Mask or paper

bag O2 if patient is Hypoxic

Nursing Diagnosis

Medication Sedatives to control Hyperventilation Antianxiety Me

METABOLIC ACIDOSIS

Base bicarbonate loss from body fluids or occurs when other acid other than Carbonic Acid accumulates Either way Bicarbonate is deficient

Very rarely occurs spontaneously

Usually occurs accompanied by other problems

CLINICAL MANIFESTATIONS

Neurologic

Cardiovascular

Gastrointestinal

Neuromuscular

Respiratory

CLINICAL FINDINGS pH < than 7.35

Remember in Metabolic you look at HCO3

HCO3 < 22 mEq/L

PaCO2 is normal if uncompensated

PaCO2 is decreased in compensated

Hyperkalemia

EKG Changes

THERAPEUTIC MANAGEMENTNURSING DIAGNOSIS

Correct Underlying Problem Hydration Nutrients Electrolytes Administration of Sodium Bicarb or Sodium

lactate Administration of N/S Reg. Insulin and

potassium for DKA

Nursing Diagnosis

METABOLIC ALKALOSIS

Loss of acid or gain on bicarbonate – Which in turn causes Increase pH and Increase in HCO3

Conditions that cause Alkalosis Gastric suction, Prolonged vomiting Ingestion of bicarbonate bases (baking soda

antacids) Diuretic Therapy Potassium Deficit

CLINICAL MANIFESTATIONS

Respiratory

Cardiovascular

Gastrointestinal

Neuromuscular

Respiratory

CLINICAL FINDINGS

pH > 7.45 Remember HCO3 is the focus HCO3 > 26 mEq/L PaCO2 is normal uncompensated PaCO2 is elevated if compensated Urine pH is >6 if compensated Hypokalemia Hypocalcemia Hyponatremia and Hypochloremia

THERAPEUTIC MANAGEMENTNURSING DIAGNOSIS

Correct Underlying Problem Provide sufficient chloride to enhance renal

absorption of sodium and excretion of HCO3 and restore normal fluid balance

Nursing Diagnosis

ABG INTERPRETATION

Step One

Assess the pH to determine if the blood is within normal range, alkalotic or acidotic. If it is above 7.45, the blood is alkalotic. If it is below 7.35, the blood is acidotic.

ABG’S

Step Two If the blood is alkalotic or acidotic, we now

need to determine if it is caused primarily by a respiratory or metabolic problem. To do this, assess the PaCO2 level. Remember that with a respiratory problem, as the pH decreases below 7.35, the PaCO2 should rise. If the pH rises above 7.45, the PaCO2 should fall. Compare the pH and the PaCO2 values. If pH and PaCO2 are indeed moving in opposite directions, then the problem is primarily respiratory in nature.

ABG’S

Step Three

Finally, assess the HCO3 value. Recall that with a metabolic problem, normally as the pH increases, the HCO3 should also increase. Likewise, as the pH decreases, so should the HCO3. Compare the two values. If they are moving in the same direction, then the problem is primarily metabolic in nature.

ABG’S

pH PaCO2 HCO3

Respiratory Acidosis

Normal

Respiratory Alkalosis

Normal

Metabolic Acidosis

Normal

Metabolic Alkalosis

Normal

TEST OURSELVES

Jane Doe is a 45-year-old female admitted to the nursing unit with a severe asthma attack. She has been experiencing increasing shortness of breath since admission three hours ago. Her arterial blood gas result is as follows:

Clinical LaboratoryPATIENT: DOE, JANEDATE: 6/4/03 18:43pH 7.22PaCO2 55HCO3- 25

Follow the steps: 1. Assess the pH. It is low (normal 7.35-7.45);

therefore, we have acidosis. 2. Assess the PaCO2. It is high (normal 35-

45) and in the opposite direction of the pH. 3. Assess the HCO3. It has remained within

the normal range (22-26).

ANSWER

Acidosis is present (decreased pH) with the PaCO3 being increased, reflecting a primary respiratory problem. For this patient, we need to improve the ventilation status by providing oxygen therapy, mechanical ventilation, pulmonary toilet or by administering bronchodilators.

ANOTHER CHANCE

John Doe is a 55-year-old male admitted to your nursing unit with a recurring bowel obstruction. He has been experiencing intractable vomiting for the last several hours despite the use of antiemetic. Here is his arterial blood gas result:

Clinical LaboratoryPATIENT: DOE, JOHNDATE: 3/6/03 08:30pH 7.50PaCO2 42HCO3 - 33

Follow the three steps again: 1. Assess the pH. It is high (normal 7.35-

7.45), therefore, indicating alkalosis. 2. Assess the PaCO2. It is within the normal

range (normal 35-45). 3. Assess the HCO3. It is high (normal 22-26)

and moving in the same direction as the pH.

ANSWER

Alkalosis is present (increased pH) with the HCO3 increased, reflecting a primary metabolic problem. Treatment of this patient might include the administration of I.V. fluids and measures to reduce the excess base.

COMPENSATION

The bodies attempt to return to normal state using the opposite system

pH is out of balance because of a respiratory disorder, it will be the renal system that makes the corrections to balance the body pH

renal system is to blame for the pH disorder, the respiratory system will have to compensate

Complete compensation returns the pH balance to normal.

There are times when the imbalance is too large for compensation to return the pH to normal. This is called incomplete compensation.

NURSING SCHOOL SURVIVAL RULES

When in doubt, wash your hands.

The correct answer is either "hand washing" or "patent airway."

If it moves, ambulate it. If it doesn't move, turn and reposition it Q2H.

Remember the 11th Commandment: Thou shalt not cross thy sterile field.

The instructor is ALWAYS right.

See Rule #5.