Acid Base Balance

ADH2 WK7

Acid-Base Balance

maintenance of arterial blood of a pH between 7.35 - 7.45

Balance of acids (H2​CO3​) and bases (HCO3−​) is crucial for normal function

Acidosis pH Level/ deadly low pH level

Arterial blood pH below 7.35 / High hydrogen ion concentration.

pH < 6.9

Alkalosis pH Level/ Deadly high pH level

Arterial Blood Ph of 7.45/ Low hydrogen ion concentration

pH > 7.8

Buffers

Substances that release or bind hydrogen ions, stabilizing pH

Kussmaul respiration

A pattern of breathing associated with acidosis in which breaths are deep and rapid.

• Medical Emergency

• Rapid deep labored breathing

• The body's response to metabolic acidosis

Normal PaO2 Range

80-100 

PaCO2 Normal Range

35-45

Out of Range CO2 is an indicator for this

Indicator for a lung issue

HCO3 Normal Range

23-30 mEq/L

Out of range bicarbonate is an indicator of this 

Indicator of kidney issue

SaO2 Normal Range

95%-100%

Lactic Acid Normal Range

0.5-2.2 mmol/L

Arterial Lactate Normal Range

3-7 mg/dL

Venous Lactate Normal Range

5-20 mg/dL

How pH Scale works

Inversely related to hydrogen ion concentration

Acidosis Physiological Effects

Reduced function of enzymes, hormones, and electrolytes.

Alkalosis Physiological Effects

Overstimulation of the nervous, neuromuscular, and cardiac systems.

Bicarbonate (HCO3−​)

The main base in body fluids, binds free hydrogen ions.

Carbonic Acid (H2​CO3​)

The main acid, releases hydrogen ions.

Ratio of Carbonic acid (H2CO3) to bicarbonate (HCO3) to maintain pH

Body maintains a 1:20 ratio

The Carbonic Anhydrase Equation

• Enzyme carbonic anhydrase links

  CO2​ levels and free hydrogen ions (H+).

• An increase in

  CO2​ leads to an increase in H+, and vice versa.

Formation of Carbonic Acid

• CO2​+H2​O→H2​CO3​ (carbonic acid).

• Carbonic acid quickly separates into

  H+ and bicarbonate ions (HCO3−​).

Right Shift

Excess CO2​→ More H+→pH decreases.

Left Shift

Excess H+→ More CO2​ production.

Chemical Buffers:

First line of defense; act immediately to stabilize pH.

• Examples: Bicarbonate, phosphate, proteins.

Respiratory Regulation

Second line of defense, adjusts CO2​ levels through breathing.

Renal Regulation

Third line of defense, adjusts bicarbonate and hydrogen ion excretion/reabsorption

Hyperventilation effect on pH

Increases CO2​ elimination, raises pH (alkalosis).

Hypoventilation effect on pH

Increases CO2​ retention, lowers pH (acidosis)

CO2​−H+ Relationship

As CO2​ levels increase, H+ increases (and vice versa).

Kidney Control of pH

Bicarbonate Reabsorption: Kidneys reabsorb or excrete bicarbonate to regulate pH.

Ammonium Formation: Excretes hydrogen ions in the form of ammonium.

Slow Response: Takes 24-48 hours to compensate for pH changes, but powerful.

Compensation

The body's process of adapting to correct changes in blood pH to maintain acid-base balance.

Respiratory or Kidney 

Respiratory Compensation

Begins compensation within seconds to minutes.

Limited capacity and can be overwhelmed.

Kidney Compensation

More powerful compensatory response.

Takes hours to days to activate fully.

Acidosis Causes 

DKA (metabolic), Lactic Acidosis (Respiratory)

Acidosis Symptoms

CNS Depression, Cardiovascular issues, Muscular weakness

Causes of Metabolic acidosis

Overproduction of Hydrogen Ions: Fatty acid breakdown, Anaerobic metabolism, Excessive intake of acids

Under elimination of Hydrogen Ions: Impaired CO2 elimination, Kidney Failure

Underproduction of Bicarbonate Ions

Over-elimination of Bicarbonate Ions

METABOLIC ACIDOSIS Symptoms

Headache,

↓ BP,

Hyperkalemia,

Muscle Twitching,

Warm/Flushed Skin (Vasodilation),

Nausea, Vomiting,

↓ Muscle Tone/Reflexes,

Confusion,

Drowsiness,

Kussmaul Respirations (Compensatory Hyperventilation)

Respiratory Acidosis

• Definition: Results from impaired respiratory function and reduced O2​−CO2​ exchange, leading to CO2​ retention.

Main Cause: CO2​ retention → Increased hydrogen ion production → Acidosis

Respiratory Acidosis Key Causes

1. Respiratory Depression: Brainstem dysfunction, trauma, increased intracranial pressure.

2. Inadequate Chest Expansion: Skeletal trauma, deformities, muscle weakness, obesity, external constriction.

3. Airway Obstruction: Prevents ventilation and gas exchange.

4. Reduced Alveolar-Capillary Diffusion: Pneumonia, ARDS, pulmonary embolism, chest trauma, drowning.

5. Improper Mechanical Ventilation: Low tidal volume or low ventilation rate.

Respiratory Acidosis Symptoms

Hypoventilation → Hypoxia,

Rapid/Shallow Respirations,

↓ BP,

Skin/Mucosa Pale to Cyanotic,

Headache,

Hyperkalemia,

Dysrhythmias (↑ K+),

Drowsiness,

Dizziness,

Disorientation,

Muscle Weakness,

Hyperreflexia.

Alkalosis Causes

Excessive Vomiting (losing to many acids), Bicarbonate Administration (gaining to many bases)

Alkalosis Symptoms

CNS Overexcitement, Muscle Cramps, Arrhythmias

Metabolic Alkalosis

Increase of base components

Causes: Medical treatment, Disease process

Metabolic Alkalosis Symptoms

Restlessness followed by Lethargy,

Dysrhythmias (Tachycardia),

Compensatory Hypoventilation,

Confusion (↓ LOC, Dizzy, Irritable),

Nausea, Vomiting, Diarrhea,

Tremors,

Muscle Cramps,

Tingling of Fingers & Toes,

Hypokalemia.

Respiratory Alkalosis

Excessive loss of carbon dioxide

Causes: Hyperventilation, Mechanical ventilation, Salicylate toxicity, High altitudes, Early-stage acute pulmonary problems

RESPIRATORY ALKALOSIS Symptoms

Seizures,

Deep/Rapid Breathing,

Hyperventilation,

Tachycardia,

↓ or Normal BP,

Hypokalemia,

Numbness & Tingling of Extremities,

Lethargy & Confusion,

Light Headedness,

Nausea, Vomiting.

Acid-Base Balance Problem Assessment

• Patients History

• Resp Rate

• Skin color

• Mental Status

Acid-Base Balance Interventions

Correct underlying cause

Hydration

Oxygen

Electrolyte monitoring

Administer meds: Bronchodilators, Antiemetics, Antidiarrheals

ROME Acid Base Interpretation (RO)

Respiratory

Opposite

High pH + Low PCO2 = Respiratory Alkalosis 

Low pH + High PCO2 = Respiratory Acidosis 

ROME Acid Base interpretation (ME)

Metabolic

Equals

High pH + High Bicarb (HCO3) Metabolic Alkalosis

Low pH + Low Bicarb (HCO3) Metabolic Acidosis