Acid-Base Balance and Imbalance James Barnett, RN, MSN Clinical Educator – Neuroscience PCC Vanderbilt University Medical Center May 2007

Definitions pH pH Measurement of how alkaline or acid a substance is Measurement of how alkaline or acid a substance is Chemistry Chemistry Neutral ph = 7 Neutral ph = 7 pH < 7 is acid pH < 7 is acid pH > 7 is alkaline pH > 7 is alkaline Normal human blood pH is slightly alkaline at 7.35 – 7.45 Normal human blood pH is slightly alkaline at 7.35 – 7.45

Definitions An Acid is… An Acid is… A molecule that can donate a H + ion A molecule that can donate a H + ion Examples: Examples: H 2 O  H + + OH - H 2 O  H + + OH - H 2 CO 3  H + + HCO 3 - H 2 CO 3  H + + HCO 3 - An acid can be weak, moderate, or strong depending on its pH An acid can be weak, moderate, or strong depending on its pH Weaker acids are closer to 7 Weaker acids are closer to 7 Stronger acids are closer to 1 Stronger acids are closer to 1

Definitions A Base or alkali is… A Base or alkali is… A molecule that can accept a H + ion A molecule that can accept a H + ion Examples: Examples: H + + OH -  H 2 O H + + OH -  H 2 O H + + HCO 3 -  H 2 CO 3 H + + HCO 3 -  H 2 CO 3 A base can be weak, moderate, or strong depending on its pH A base can be weak, moderate, or strong depending on its pH Weaker bases are closer to pH 7 Weaker bases are closer to pH 7 Stronger bases are closer to pH 14 Stronger bases are closer to pH 14

An Important Equilibrium Equation H 2 O + CO 2  H 2 CO 3  H + + HCO 3 - Water plus carbon dioxide equals carbonic acid which is broken down by carbonic anhydrase into a hydrogen ion and bicarbonate.

Types of Acids Volatile acids Volatile acids Easily move from liquid to gas state Easily move from liquid to gas state Within the body Within the body Lung can remove Lung can remove H 2 CO 3 + renal enzyme  H 2 O + CO 2 (both of which are exhaled) H 2 CO 3 + renal enzyme  H 2 O + CO 2 (both of which are exhaled) Carbon dioxide is therefore considered an acid Carbon dioxide is therefore considered an acid KEY CONCEPT: As CO2 rises, there is more acid  respiratory acidosis KEY CONCEPT: As CO2 drops, there is less acid  respiratory alkalosis

Types of Acids Nonvolatile acids Nonvolatile acids Cannot be changed to gas state Cannot be changed to gas state Within the body Within the body Must be removed by the kidneys (metabolic) Must be removed by the kidneys (metabolic) Examples Examples Keto acids Keto acids Lactic acids Lactic acids

Acid-Base Imbalance

Acid Imbalance Too much CO 2 leads to decreased pH and an acid condition Too much CO 2 leads to decreased pH and an acid condition Too little CO 2 leads to increased pH and an alkaline condition Too little CO 2 leads to increased pH and an alkaline condition PaCO 2 PaCO 2 Amount of CO 2 dissolved in the blood Amount of CO 2 dissolved in the blood Good indicator of respiratory and ventilatory function Good indicator of respiratory and ventilatory function

Base Imbalance Major base in body is bicarbonate (HCO 3 - ) Major base in body is bicarbonate (HCO 3 - ) Regulated by the kidneys (metabolic) Regulated by the kidneys (metabolic) Too little HCO 3 - causes decrease in pH and acid conditions Too little HCO 3 - causes decrease in pH and acid conditions Too much HCO 3 - causes increase in pH and alkaline conditions Too much HCO 3 - causes increase in pH and alkaline conditions

More definitions Acidemia – condition where blood is more acid than normal (pH < 7.35) Acidemia – condition where blood is more acid than normal (pH < 7.35) Alkalemia – condition where blood is more alkaline than normal (pH > 7.45) Alkalemia – condition where blood is more alkaline than normal (pH > 7.45) Acidosis – the process causing acidemia Acidosis – the process causing acidemia Alkalosis – the process causing alkalemia Alkalosis – the process causing alkalemia

Respiratory Imbalances Respiratory mechanisms involve either Respiratory mechanisms involve either Retention of excess carbon dioxide Retention of excess carbon dioxide Retention of insufficient carbon dioxide Retention of insufficient carbon dioxide Over- or Under-ventilation or respiration abnormalities are the main causes of this imbalance Over- or Under-ventilation or respiration abnormalities are the main causes of this imbalance

Metabolic Imbalances Metabolic mechanisms involve Metabolic mechanisms involve Renal function alteration Renal function alteration Production of acidic metabolic products Production of acidic metabolic products Loss of acid from the body Loss of acid from the body

The Normal’s pH pH PaCO 2 PaCO 2 HCO 3 - HCO 3 - PaO 2 PaO – – 45 mmHg 22 – 26 mEq/L 80 – 100 mmHg

The Abnormal’s Respiratory Acidosis Respiratory Acidosis Respiratory Alkalosis Respiratory Alkalosis Metabolic Acidosis Metabolic Acidosis Metabolic Alkalosis Metabolic Alkalosis

Respiratory Acidosis pH < 7.35 pH < 7.35 PaCO 2 > 45 PaCO 2 > 45 Alveolar Hypoventilation CNS depression or disease CNS depression or disease Ventilatory/respiratory dysfunction Ventilatory/respiratory dysfunction Acute infections Acute infections Signs and Symptoms Dyspnea Restlessness Confusion/lethargy Dysrhythmias Headache Treatment Increase ventilation Treat the cause

Respiratory Alkalosis pH > 7.45 pH > 7.45 PaCO 2 < 35 PaCO 2 < 35 Alveolar Hyperventilation Anxiety Anxiety Pain Pain Fever Fever Thyrotoxicosis Thyrotoxicosis CNS lesions CNS lesions Improper vent management, hypoxia Improper vent management, hypoxia Pulmonary embolus Pulmonary embolus Signs and Symptoms Light headedness Confusion Muscle spasm / parasthesias Dysrhythmias / palpitations Sweating Dry mouth Blurred vision Treatment Slow down breathing Paper bag breathing if anxiety or fear is cause Treat the cause!

Metabolic Acidosis pH < 7.35 pH < 7.35 HCO 3 - < 22 mEq/L HCO 3 - < 22 mEq/LCauses Increased acids from Increased acids from Anaerobic metabolism Anaerobic metabolism Abn metabolic process (DKA, lactic acidosis) Abn metabolic process (DKA, lactic acidosis) Starvation Starvation ASA or other acid ingestion ASA or other acid ingestion Excess HCO3- loss Excess HCO3- loss Diarrhea Diarrhea Renal Failure Renal Failure Intestinal Fistulae Intestinal Fistulae Signs and Symptoms Headache Confusion/lethargy Stupor/coma Weakness Kussmaul respiration N/V Dysrhythmias Flushing Treatment Treat the cause!!! Give Bicarbonate Dialysis for renal failure

Metabolic Alkalosis pH > 7.45 pH > 7.45 HCO 3 - > 28 HCO 3 - > 28Cause Increased base Increased base Excessive use of bicarb Excessive use of bicarb Lactate from dialysis Lactate from dialysis Excessive antacid ingestion Excessive antacid ingestion Acid loss Acid loss Vomiting/Gastric suctioning Vomiting/Gastric suctioning Hypo- chloremia -kalemia Hypo- chloremia -kalemia Diuretics Diuretics Large volume blood transfusion Large volume blood transfusion Signs and Symptoms Muscle spasms/tetany/seizure Dizziness Disorientation/lethargy/coma Weakness N/V Depressed respiratory drive Treatments Treat the cause!!!! Increase respirations

Finished You have finished this in-service on Acid-Base Balance and Imbalance. You have finished this in-service on Acid-Base Balance and Imbalance. Continue with the next lesson titled: Continue with the next lesson titled: Compensated and Uncompensated Blood Gas Analysis Compensated and Uncompensated Blood Gas Analysis