Acid-Base Balance PDF
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October University for Modern Sciences & Arts
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This document provides a comprehensive overview of acid-base balance in the body. It explains how the body regulates acid-base levels, and describes the different types of acidosis and alkalosis. The document also discusses the compensatory mechanisms of the body.
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Normal PH values Explain normal regulation of PH Differentiate respiratory acid-base imbalance Differentiate metabolic acid-base imbalance Known medical management of acid base imbalance Acids and bases are formed during normal metabolic processes Acids: Is...
Normal PH values Explain normal regulation of PH Differentiate respiratory acid-base imbalance Differentiate metabolic acid-base imbalance Known medical management of acid base imbalance Acids and bases are formed during normal metabolic processes Acids: Is a proton donor Hydrogen containing substance which dissociate in a solution to release H⁺ ion Base : Is a proton acceptor A substance accept H⁺ ion often with the release of hydroxyl OH⁻ ions Buffer: is a mixture of weak acid and its conjugate base Has the ability to resist changes in pH when acid or base added to an aqueous solution Weak acid: a substance that reversibly donates H⁺ Weak base: a substance that reversibly binds H⁺ pH : refers to the concentration of H⁺ in a solution 1pH unit change = 10 fold change in H⁺ ion Normal pH : 7.35 – 7.45 Acidosis: An increase H⁺ ion concentration decreases the pH < 7.35 Alkalosis: A decrease in H⁺ ion concentration increase in pH >7.45 The maintenance of acid-base status is very important for hemostasis A slit change in pH below 7.35 or above 7.45 will cause serious threats to many physiological functions (coma and death) Are formed continuously during metabolic reactions Can also entered from outsides May be lost in abnormal pathological conditions Daily production of H⁺ ion in form of volatile and non volatile acids, if are not removed, pH of body fluids will be seriously disturbed ❑ Volatile acids: Produced by oxidative metabolism of CHO, fat and protein e.g. carbonic acid Excreted through lungs as CO2 ❑ Non volatile acids (Fixed acids): E.g. phosphoric acid, sulfuric acid, lactic acid and organic acids Acids generated during catabolism of amino acids, phospholipids and nucleic acids Remain in body fluid until eliminated by kidneys Acid-base balance is concerned with maintaining a normal hydrogen ion concentration in the body fluid The body has three different mechanisms to regulate acid-base status: 1. chemical buffer system which binds free H⁺ ions 2. Respiratory mechanism which remove CO2 3. Renal mechanism which excretes H⁺ ions and conserve the bases HCO3⁻ It is the first line of defense against blood pH changes It acts very rapidly within seconds It is the least efficient mechanism It includes: A. The bicarbonate buffer system (NaHCO3/H2CO3) B. The phosphate buffer system (Na2HPO4/NaH2PO4) C. The protein buffer system ▪ It is very important in extracellular fluid (ECF), plasma HCO3 acts immediately and interstitial HCO3 acts within minutes ▪ It consist of HCO3 and H2CO3 B. The phosphate buffer system (Na2HPO4/NaH2PO4): ▪ Phosphate buffer formed inorganic phosphate ▪ It is very important in intracellular fluid (ICF) C. Protein buffer system: ▪ It is the most important buffer in the body ▪ It present in: ▪ Intracellular fluid ▪ Plasma proteins ▪ Hemoglobin (Hb) which is the most important metabolic buffer in the blood and ECF ▪ responsible for 60 % of buffering capacity of the blood It is the second line of defense mechanism against blood pH changes It acts within minutes to hours It is a moderate efficient mechanism It acts by controlling dissolved CO2 level in the blood How it works: Decrease arterial blood pH (e.g. metabolic acidosis) causes changes in the CSF pH that stimulate chemoreceptors within the brain stem that in turn stimulate the respiratory center. This increase in the alveolar ventilation (rate and depth of breathing) This in turn decreases PaCO2 which restores the arterial pH to normal levels It is the third line of defense mechanism against blood pH changes It acts within few hours to days It is the most powerful and efficient mechanism It acts by controlling the HCO3⁻ level in the blood to keep HCO3⁻/ CO2 constant at about 20:1 Prevent changes in blood pH by increase reabsorption of filtered HCO3⁻ and excreting H⁺ ion in urine An acid base disorder is a change in normal value of extracellular pH Occurs when renal or respiratory function is abnormal Or when an acid or base load overwhelm excretory capacity Normal values: pH 7.35 – 7.45 PCO2 35 – 45 mmHg HCO3 22 – 26 mEq/L Acidosis: process that increases H⁺ by increasing PCO2 or by reducing HCO3⁻ Decrease in blood pH below normal range Alkalosis: Process that reduces H⁺ by reducing PCO2 or by increasing HCO3⁻ Increase in blood pH above normal range Acidosis and alkalosis are not disease but rather are the result of a wide variety of disorders. Acidosis and alkalosis are categorized as metabolic or respiratory depending on their primary cause. ❑ Metabolic acidosis and metabolic alkalosis are caused by imbalance in the production of acids or bases and their excretion by the kidney. ❑ Respiratory acidosis and respiratory alkalosis are caused by changes in carbon dioxide due to lung or breathing disorder ❑ Major adverse effect of systemic acidosis (pH < 7.2): Acidosis mainly affect cardiovascular system Acidosis decrease myocardial contractility the clinical effect are minimal until pH < 7.2, cardiac response to catecholamine are decreased these effect are accentuated in patients with myocardial ischemia, left ventricular dysfunction, on B-blockers or under general anesthesia ❑ Major adverse effect of severe systemic alkalosis (pH > 7.6): reflect impairment on cerebral and coronary artery blood flow due to arterial vasoconstriction Decrease serum ionized calcium concentration (hypocalcemia) which responsible for neurologic abnormalities (seizures) Predispose patient to ventricular arrhythmias Hypokalemia Alkalosis depress ventilation so impair weaning patients from mechanical ventilation ❑ It is due to a decrease in HCO3⁻ ❑ Causes: Diabetic ketoacidosis ( accumulation of ketone bodies) Drugs e.g. aspirin intoxication, acetazolamide, alcohol Shock (lactic acidosis) Loss of bases (bicarbonate): diarrhea, Colostomy renal failure, hepatic failure Renal tubular acidosis Cyanide or carbon monoxide poisoning ❑ Sign and symptoms: no symptoms in mild acidosis nausea, vomiting and fatigue Hyperventilation (increase rate) and depth of breathing to correct acidosis by washing CO2 Drowsiness and confusion If not corrected hypotension, shock, coma and death ❑ Treatment: Treatment of metabolic acidosis includes Treatment of the cause e.g.: Insulin and fluids for treatment of diabetic ketoacidosis and fluids for improvement of tissue perfusion in lactic acidosis Remove toxic substance from the blood Bicarbonate given only when pH