Mastering Arterial Blood gases ABGs - FUND

Buffers, Respiratory regulation, and Renal regulation

The body maintains the blood’s pH in a narrow window through the use of:

Buffers

a substance that has the chemical ability to absorb changes in pH when an acid or base is added to the solution

Respiratory regulation

The lungs utilize carbonic acid (created when CO2 and water mix). Changes in ventilation result in not enough carbon dioxide, or too much

Renal regulation

The kidneys filter hydrogen (H+) and bicarbonate (HCO3–) and either excrete them in the urine or reabsorb them back into the bloodstream

Acid-Base Imbalances

_______ occur when one or both of these systems fail

• Acidosis

• Alkalosis

Alkalosis

higher than expected (level of acid is too low)

Acidosis

pH lower than expected (level of acid is too high)

acid–base imbalance

When an _______ occurs, the body will attempt to regain homeostasis by using the opposing system (lungs or kidneys) to restore balance.

When to consider ordering:

 Respiratory distress

 Changes in the level of consciousness

 Trauma

 Diabetes mellitus (DKA, hyperglycemia)

 Sepsis

 Dehydration

 Intoxication with poisons or other toxins

Respiratory Acidosis

The lungs cannot remove enough carbon dioxide, often due to respiratory depression → The kidneys increase the amount of bicarbonate in the body while excreting hydrogen through the urine.

Primary Causes of Respiratory Acidosis

- any condition preventing adequate ventilation or causing hypoventilation

• Central nervous system depression

• spinal cord injury

• pulmonary diseases

• functional disorders

Central nervous system depression

brain trauma, opioids (morphine, fentanyl, heroin), sedatives, or anesthesia

Spinal cord injury

with impaired respiratory function

Pulmonary diseases

atelectasis, pneumonia, pulmonary embolism, or obstructive pulmonary disorders (COPD)

Functional disorders

limiting respirations—for example, chest wall injury or abdominal distention

Respiratory Acidosis Manifestations

 anxiety and confusion

 lethargy, fatigue, sleepiness

 shortness of breath

Treament for respiratory acidosis

 supplemental oxygen administration

 medications: bronchodilators and corticosteroids to promote air movement and decrease swelling/inflammation

Respiratory alkalosis

Carbon dioxide levels drop due to too much being exhaled, usually due to hyperventilation → The kidneys excrete bicarbonate through the urine while decreasing the amount of new bicarbonate being produced.

Primary Causes of Respiratory Alkalosis

- any condition causing hyperventilation

1. pain

2. Psychological Distress: Ex. anxiety, severe stress, panic

3. Central nervous system injury: Ex. head injury, stroke, or meningitis

4. infection, sepsis, or fever

5. drug use (LSD, methamphetamines, cocaine)

6. medications (aspirin, asthma medications)

Respiratory Alkalosis Manifestations

 hyperventilation

 lightheadedness, dizziness, confusion, altered mental status

 chest discomfort

 tingling of the mouth, fingers or toes

Respiratory Alkalosis Treatments

 breathing into a paper bag or applying oxygen using a partial rebreathing mask can help increase the CO2 levels by rebreathing previously expired air.

 Medications to manage pain or anxiety

Metabolic acidosis

kidneys cannot rid the body of excess acid → The lungs try to exhale the acid (carbon dioxide) by increasing the respiratory rate and depth.

Primary Causes of metabolic acidosis

1. Increased Production of Acid:

 Ketoacidosis (increased ketones from using fat for energy)

 Diabetes, starvation, alcohol toxicity

 Lactic acidosis (body produces too much lactic acid through anerobic respiration due to reduced tissue perfusion)

 cancer, sepsis, cardiac arrest, salicylate intoxication, severe dehydration

2. Decreased Excretion of Acid: renal failure or kidney disease

3. Renal/Gastric Loss of Bicarb: Severe diarrhea or laxative abuse

Manifestations of metabolic acidosis

 Kussmaul Respirations: long and deep breaths (buffer compensation)

 confusion, headache, lethargy

 tachycardia

 loss of appetite, nausea and vomiting

treatment for metabolic acidosis

- correcting the underlying cause, with the goal of ridding the body of the excess acid.

 Sodium bicarbonate (a base) is often given to neutralize the acid in the blood

 IV fluids to dilute the acid

Metabolic alkalosis

The kidneys are holding on to too much bicarbonate or body is losing too much acid → The lungs try to retain acid by slowing the respiratory rate while the kidneys decrease bicarbonate through excretion into the urine.

Primary cause Metabolic alkalosis

1. Gastrointestinal Loss of H+: prolonged vomiting, gastric suctioning, excessive use of antacids (contains sodium bicarb)

2. Renal Loss of H+: excessive use of diuretics, renal impairment,

3. Hypokalemia (forces H+ into the cells)

Metabolic Alkalosis Manifestations

 Muscle twitching or spasms

 Lethargy, Lightheadedness, Headache

 Nausea and vomiting

 Tremors, tingling, or numbness of extremities

• With severe metabolic alkalosis, confusion, seizures, agitation, coma and arrhythmias can occur

treatments for metabolic alkalosis

 Correcting the underlying cause

 Retain potassium and excrete bicarb (potassium sparing diuretics)

 Can replace acid in severe cases