Acid-Base (Class 22)

Acid

A substance that shows pH values lower than 7 when it is in an aqueous solution. Releases H+ in a solution.

Base

A substance that shows pH value higher than 7 when it is in an aqueous solution. Binds to H+ in solutions

pH

The degree of acidity and alkalinity in the blood and other body fluids is reported as pH.

Acidosis

A condition that makes the blood too acidic.

Alkalosis

A condition that tends to make the blood too alkaline.

Arterial Blood pH

7\.35-7.45

Effects of an Abnormal pH

* Enzymes cannot carry out functions
* Oxygen does not bind to hemoglobin
* Death

Two Types of Acids

* Carbonic Acid
* Metabolic Acid (Any acid that is not carbonic)

Acid-Base Homeostasis Processes

* Acid production
* Acid buffering
* Acid excretion

Buffers

* Pairs of chemicals that work together to maintain normal pH of body fluids.
* Decrease in pH will cause the buffer to bind to H+.
* Increase in pH will cause the buffer to release H+.

True

True or False: Bicarbonate is the main buffer in the body.

Lungs (Excretion)

* Excrete Co2 and water (carbonic acid)
* Occurs through alterations in respiratory rate and depth.

Kidneys (Excretion)

* Excrete metabolic acids
* Filter and process them into urine (why urine is acidic)

Arterial Blood Gases (ABGs)

* Used to monitor the patient’s acid-base balance through an arterial blood sample.
* Drawn by a qualified RN or respiratory therapist.

PaCO2 Value

35-45 mmHg

HCO3 Value

(Arterial) 21-28 mEq/L

PaO2 Value

80-mmHg

SaO2 Value

95-100%

PaCO2

* Level of CO2 in the blood
* Acidic

PaO2

* Determines how much oxygen is moving into the blood from the alveoli level into the capillaries.

SaO2

* Percent of oxygen that binds to hemoglobin

Conditions that Affect Metabolic Acidosis

* Increased Metabolic Acids:
* Ketoacidosis (diabetes, starvation, alcoholism, etc.)
* Hypermetabolic state (burns)
* Oliguric renal disease
* Circulatory shock
* Ingestion of acid or acid precursors
* Decreased Bicarbonate:
* Diarrhea
* Pancreatic fistula
* Renal tubular acidosis

Conditions that Affect Metabolic Alkalosis

* Increase of Bicarbonate:
* Excessive sodium bicarbonate administration
* Massive blood transfusion
* Mild or moderate ECV deficit
* Decrease in Metabolic Acid:
* Excessive vomiting or gastric suctioning
* Hypokalemia
* Excessive aldosterone

True

True or False: The GI tract is lined with K and the bowels are lined with bicarb.

Conditions that Affect Respiratory Acidosis

* Impaired gas exchange:
* Type B COPD
* Bacterial Pneumonia
* Airway obstruction
* Excessive atelectasis
* Severe acute asthma episode
* Impaired neuro function:
* Respiratory muscle weakness/fatigue
* Chest wall injury or painful surgery
* Brainstem dysfunction:
* Drug overdose
* Some types of head injuries

Conditions that Affect Respiratory Alkalosis

* Hypoxemia
* Acute pain
* Anxiety, psychological distress, sobbing
* Inappropriate mechanical ventilator settings
* Stimulation of respiratory control in the brainstem (Ex. Sepsis, meningitis, head injury, aspirin overdose, etc.)

Respiratory Acidosis

* Retention of CO2
* Lab Values:
* pH:

Respiratory Alkalosis

* Blowing off CO2
* Lab Values:
* pH: >7.45
* PaCO2:

Metabolic Acidosis

* Lab Values:
* pH:

Metabolic Alkalosis

* Lab Values:
* pH: >7.45
* PaCO2: Normal
* HCO3: >28 mEq/L
* Symptoms:
* Lightheadedness
* Dysrhythmias
* Numbness
* Muscle cramps
* Possible excitement/confusion followed by decreased LOC

Nursing Interventions

* Supplemental oxygen if needed
* Maintain a functional IV line
* Fluid/Electrolyte replacement and prescribed drugs
* Monitor patient closely for status change
* Fall prevention protocols
* Support compensatory hyperventilation by keeping oral mucous membranes moist and positioning them to facilitate chest expansion

True

True or False: When administering Sodium Bicarbonate to correct metabolic acidosis, watch for the signs of rebound alkalosis.