Anatomy & Physiology Tri-State Business Institute Micheal H. McCabe, EMT-P

Acid-Base Balance: pH of Body Fluids pH of Body Fluids Mechanisms that control pH of Body Fluids Mechanisms that control pH of Body Fluids pH Imbalances pH Imbalances

The pH scale: Definition of pH – a number that indicates the hydrogen ion (H+) concentration of a fluid. Definition of pH – a number that indicates the hydrogen ion (H+) concentration of a fluid. A pH of 7.0 indicates neutrality – neither acid nor base A pH of 7.0 indicates neutrality – neither acid nor base A pH higher than 7.0 indicates alkalinity A pH higher than 7.0 indicates alkalinity A pH less than 7.0 indicates acidity A pH less than 7.0 indicates acidity

pH of Body Fluids: Normal pH of arterial blood is around 7.45 Normal pH of arterial blood is around 7.45 Normal pH of venous blood is around 7.35 Normal pH of venous blood is around 7.35 Normal pH of urine ranges from 4.6 to 8.0 Normal pH of urine ranges from 4.6 to 8.0 Gastric Acid has a pH of around 1.6 – 2.0 Gastric Acid has a pH of around 1.6 – 2.0 Saliva has a pH of 7.7 Saliva has a pH of 7.7

Mechanisms that Control pH of Body Fluids: 1. The buffer system 2. The respiratory system 3. The urinary system

The Buffer System: Buffers – Substances that prevent a sharp change in the pH of a fluid when an acid or base is added to it. Buffers – Substances that prevent a sharp change in the pH of a fluid when an acid or base is added to it. Acids are buffered mainly by sodium bicarbonate (NaHCO 3 ) Acids are buffered mainly by sodium bicarbonate (NaHCO 3 )

Carbon Anhydrase: Carbon Anhydrase is an enzyme found in red blood cells that helps combine carbon dioxide with water into carbonic acid. Carbon Anhydrase is an enzyme found in red blood cells that helps combine carbon dioxide with water into carbonic acid. This allows blood to efficiently transport carbon dioxide in solution without specialized carrier proteins (as is required for transport of oxygen – hemoglobin) This allows blood to efficiently transport carbon dioxide in solution without specialized carrier proteins (as is required for transport of oxygen – hemoglobin) The presence of carbonic acid in venous blood accounts for the lower pH of venous blood when compared to arterial blood. The presence of carbonic acid in venous blood accounts for the lower pH of venous blood when compared to arterial blood.

Carbonic Acid Formation: CO 2 + H 2 O  H 2 CO 3

Changes in Blood Produced by Buffering of Acids in Tissue Capillaries: Amount of carbonic acid (H 2 CO 3 ) in blood increases slightly. Amount of carbonic acid (H 2 CO 3 ) in blood increases slightly. Amount of NaHCO 3 in blood decreases; ratio of amount of NaHCO 3 to H 2 CO 3 normally does not change; normal ratio is 20:1 Amount of NaHCO 3 in blood decreases; ratio of amount of NaHCO 3 to H 2 CO 3 normally does not change; normal ratio is 20:1 H+ Concentration of blood increases slightly H+ Concentration of blood increases slightly Blood pH decreases slightly below arterial levels Blood pH decreases slightly below arterial levels

Respiratory Mechanism of pH Control: Respirations remove some CO 2 from blood as blood flows through lung capillaries. Respirations remove some CO 2 from blood as blood flows through lung capillaries. The amount of H 2 CO 3 in blood is decreased and thereby its H+ concentration is decreased. The amount of H 2 CO 3 in blood is decreased and thereby its H+ concentration is decreased. This increases blood pH from its venous to arterial level. This increases blood pH from its venous to arterial level.

Urinary Mechanism of pH Control: The urinary mechanism is the body’s most effective regulator of blood pH. The urinary mechanism is the body’s most effective regulator of blood pH. The kidneys acidify urine by the distal tubules secreting H+ ions and ammonia (NH 3 ) into the urine in exchange for NaHCO 3 being reabsorbed by the blood. The kidneys acidify urine by the distal tubules secreting H+ ions and ammonia (NH 3 ) into the urine in exchange for NaHCO 3 being reabsorbed by the blood.

pH Imbalances: Acidosis & Alkalosis are the two kinds of pH imbalance. Acidosis & Alkalosis are the two kinds of pH imbalance. Disturbances in acid-base balance depend on relative quantities of NaHCO 3 and H 2 CO 3 in the blood. Disturbances in acid-base balance depend on relative quantities of NaHCO 3 and H 2 CO 3 in the blood. The Body can regulate both components (sodium bicarbonate and carbonic acid) through separate mechanisms. The Body can regulate both components (sodium bicarbonate and carbonic acid) through separate mechanisms.

pH Imbalances: Blood levels of sodium bicarbonate (NaCO 3 ) are regulated by the kidneys. Blood levels of sodium bicarbonate (NaCO 3 ) are regulated by the kidneys. Blood levels of carbonic acid (H 2 CO 3 ) are regulated by the lungs. Blood levels of carbonic acid (H 2 CO 3 ) are regulated by the lungs.

Metabolic Disturbances: Changes in metabolism can change the acid / base balance. Changes in metabolism can change the acid / base balance. Uncontrolled diabetes mellitus can result in metabolic acidosis (DKA -- diabetic ketoacidosis). Uncontrolled diabetes mellitus can result in metabolic acidosis (DKA -- diabetic ketoacidosis). Severe vomiting can result in metabolic alkalosis. Severe vomiting can result in metabolic alkalosis.

Causes of Metabolic Acidosis: Renal Disease Renal Disease Uncontrolled Diabetes Uncontrolled Diabetes Prolonged Diarrhea Prolonged Diarrhea Poisoning (Aspirin, Anti-Freeze, Wood Alcohol, Sterno, etc.) Poisoning (Aspirin, Anti-Freeze, Wood Alcohol, Sterno, etc.) Exhaustion Exhaustion Starvation Starvation

Diabetic Ketoacidosis: If insulin is unavailable, body cells are unable to metabolize carbohydrates and switch to fat metabolism. If insulin is unavailable, body cells are unable to metabolize carbohydrates and switch to fat metabolism. Fat metabolism produces ketone bodies as waste products. In solution, ketones are acidic. Fat metabolism produces ketone bodies as waste products. In solution, ketones are acidic. Accumulation of ketones in the blood causes metabolic acidosis. Accumulation of ketones in the blood causes metabolic acidosis.

Lactic Acidosis: Carbohydrate metabolism requires oxygen. Carbohydrate metabolism requires oxygen. Physical endurance is limited by the ability of the body to deliver oxygen to the cells. Physical endurance is limited by the ability of the body to deliver oxygen to the cells. When the workload (as in strenuous work or exercise) exceeds the ability of the body to deliver oxygen to the cells, the cells are forced to switch to less efficient anaerobic metabolism. When the workload (as in strenuous work or exercise) exceeds the ability of the body to deliver oxygen to the cells, the cells are forced to switch to less efficient anaerobic metabolism. This condition is known as oxygen debt. This condition is known as oxygen debt. Anaerobic metabolism produces metabolic waste in the form of lactic acid. Anaerobic metabolism produces metabolic waste in the form of lactic acid. Localized lactic acidosis in muscle tissue is perceived as muscle fatigue. Systemic lactic acidosis can result in death. Localized lactic acidosis in muscle tissue is perceived as muscle fatigue. Systemic lactic acidosis can result in death.

Lactic Acidosis and Glucophage: Glucophage is a commonly used oral medication for the treatment of non- insulin dependant diabetes. Glucophage is a commonly used oral medication for the treatment of non- insulin dependant diabetes. A rare but serious complication of Glucophage therapy is systemic lactic acidosis. A rare but serious complication of Glucophage therapy is systemic lactic acidosis. Incidence: 1 pt. in 33,000 Incidence: 1 pt. in 33,000 Mortality: 50% Mortality: 50%

Causes of Metabolic Alkalosis: Diuretic Therapy Diuretic Therapy Vomiting Vomiting Gastric Suction / Gastric Lavage Gastric Suction / Gastric Lavage Metabolic Disease (Cushing’s Syndrome) Metabolic Disease (Cushing’s Syndrome) Poisoning Poisoning

Vomiting: Vomiting (also called emesis) is the forcible emptying of gastric and sometimes esophageal contents. Vomiting (also called emesis) is the forcible emptying of gastric and sometimes esophageal contents. Vomiting occurs as the result of many stimuli including foul odors or tastes, irritation of the stomach or intestinal mucosa, and some emetic drugs such as ipecac. Vomiting occurs as the result of many stimuli including foul odors or tastes, irritation of the stomach or intestinal mucosa, and some emetic drugs such as ipecac. Severe vomiting can be life threatening. Severe vomiting can be life threatening. One life-threatening complication of vomiting is metabolic alkalosis. One life-threatening complication of vomiting is metabolic alkalosis. Bicarbonate excess occurs because of the massive loss of hydrochloric acid from the stomach. Bicarbonate excess occurs because of the massive loss of hydrochloric acid from the stomach. Therapy includes IV administration of chloride-containing solutions such as Normal Saline (0.9% Sodium Chloride) Therapy includes IV administration of chloride-containing solutions such as Normal Saline (0.9% Sodium Chloride)

Respiratory Disturbances: Respiratory failure can result in respiratory acidosis – carbon dioxide(CO 2 ) remains in the blood as carbonic acid (H 2 CO 3 ). Respiratory failure can result in respiratory acidosis – carbon dioxide(CO 2 ) remains in the blood as carbonic acid (H 2 CO 3 ). Hyperventilation can result in respiratory alkalosis – too much carbon dioxide is removed and the blood becomes alkali. Hyperventilation can result in respiratory alkalosis – too much carbon dioxide is removed and the blood becomes alkali.

Causes of Respiratory Acidosis: Respiratory Depression or arrest due to drugs, anesthesia, or head injury. Respiratory Depression or arrest due to drugs, anesthesia, or head injury. Pulmonary diseases such as emphysema or pneumonia. Pulmonary diseases such as emphysema or pneumonia. Hypoxia / Anoxia / Asphyxia / Apnea Hypoxia / Anoxia / Asphyxia / Apnea “Slow Breathing” “Slow Breathing” Any respiratory compromise Any respiratory compromise

Causes of Respiratory Alkalosis: Anxiety, Hyperventilation Syndrome Anxiety, Hyperventilation Syndrome Oxygen Toxicity (High flow oxygen for extended periods of time.) Oxygen Toxicity (High flow oxygen for extended periods of time.) Overzealous ventilation of patients on respirators Overzealous ventilation of patients on respirators Hepatic Coma Hepatic Coma

Urinary Disturbances: Since the urinary system regulates the quantity of sodium bicarbonate (NaCO 3 ) in the blood, urinary disturbances will change the pH balance. Since the urinary system regulates the quantity of sodium bicarbonate (NaCO 3 ) in the blood, urinary disturbances will change the pH balance. Renal failure can result in alkalosis since the body retains too much sodium bicarbonate (NaCO 3 ). Renal failure can result in alkalosis since the body retains too much sodium bicarbonate (NaCO 3 ).