Blood buffering system 4/17/2017 Blood buffering system

The pH of Body fluids The pH of blood is 7.35 – 7.45 Changes in pH below 6.8 and above 8.0 may result in death.

The pH of body fluids is maintained by three major buffer systems: 1- Carbonic acid–bicarbonate system. 2- Dihydrogen phosphate – hydrogen phosphate system. 3- The ability of proteins to act as either proton acceptors or proton donors at different pH values. The carbonic acid–bicarbonate system is the principal buffer in blood serum and other extracellular fluids. The hydrogen phosphate system is the major buffer within cells.

Proteins as a blood buffer Proteins contain – COO- groups, which, like acetate ions (CH3COO-), can act as proton acceptors. Proteins also contain – NH3+ groups, which, like ammonium ions (NH4+), can donate protons.

Respiratory and Renal regulation Both the respiratory & renal systems work to regulate pH in acid-base imbalance; the respiratory system works in a matter of minutes & is maximal within 12-24 hours while the renal (kidneys) system continues to function for days to restore pH within normal limits (WNL).

Respiratory Regulation of Acid-Base Balance Respiratory regulation of pH is achieved through carbonic acid/bicarbonate buffer system As carbon dioxide levels increase, pH decreases As carbon dioxide levels decrease, pH increases Carbon dioxide levels and pH affect respiratory centers Hypoventilation increases blood carbon dioxide levels Hyperventilation decreases blood carbon dioxide levels

Respiratory Regulation of Acid-Base Balance

Renal Regulation of Acid-Base Balance Secretion of H+ into filtrate and reabsorption of HCO3- into ECF cause extracellular pH to increase HCO3- in filtrate reabsorbed Rate of H+ secretion increases as body fluid pH decreases .

Acidosis and Alkalosis Acidosis: pH body fluids below 7.35 Respiratory: Caused by inadequate ventilation Metabolic: Results from all conditions other than respiratory that decrease pH Alkalosis: pH body fluids above 7.45 Respiratory: Caused by hyperventilation Metabolic: Results from all conditions other than respiratory that increase pH

Respiratory Acidosis: CO2 ↑ pH ↓ Symptoms: Failure to ventilate, suppression of breathing, disorientation, weakness, coma Causes: Lung disease blocking gas diffusion, depression of respiratory center by drugs, cardiopulmonary arrest, stroke, or nervous system disorders Treatment: Correction of disorder, infusion of bicarbonate

Respiratory Alkalosis: CO2 ↓ pH ↑ Symptoms: Increased rate and depth of breathing, numbness, light-headedness, tetany Causes: hyperventilation due to anxiety, hysteria, fever, exercise; reaction to drugs such as salicylate, quinine, and antihistamines Treatment: Elimination of anxiety producing state, rebreathing into a paper bag

Metabolic (Nonrespiratory) Acidosis: H+ ↑ pH ↓ Symptoms: Increased ventilation, fatigue, confusion Causes: Renal disease, hepatitis and cirrhosis; increased acid production in diabetes mellitus, hyperthyroidism, starvation; loss of alkali in diarrhea; acid retention in renal failure Treatment: Sodium bicarbonate given orally, dialysis for renal failure, insulin treatment for diabetic ketosis

Metabolic (Nonrespiratory) Alkalosis: H+ ↓ pH ↑ Symptoms: Depressed breathing, confusion Causes: Vomiting, diseases of the adrenal glands, ingestions of access alkali Treatment: Infusion of saline solution, treatment of underlying diseases

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