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dr sajid khan

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dr sajid khan

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  1. METABOLIC AND RESPIRAYORY ACIDOSISAND ALKALOSIS

  2. INTRODUCTION Why pH 7.35-7.45is necessary ?

  3. FOR OPTIMAL FUNCTIONING OF CELLULAR ENZYMES & METABOLIC PROCESSES

  4. NORMAL ACID-BASE HOMEOSTASIS • Acid - Base balance is primarily concerned with two ions: • Hydrogen (H+) • Bicarbonate (HCO3- )

  5. Systemic arterial pH is maintained between 7.35 and 7.45 • extracellular and intracellular chemical buffering mechanism • Respiratory • renal regulatory mechanisms.

  6. Chemical Buffers: (First system within minutes) • Bicarbonate-buffer-system • Phosphate buffer-system • Protein-buffer-system

  7. BICARBONATE BUFFER H++HCO3ˉ == H2O+ CO2 ( pK 6.1 ) • NON-BICARBONATE BUFFERS 1. ALBUMIN ( PK 6.5) 2. Hb 3. phosphate[H2PO4ˉ == H+ + HPO4ˉˉ ( pK6.8)] 4. Bone

  8. Chemoreceptors in the medulla of brain sense pH changes and vary the rate and depth of breathing to compensate for pH changes. • The lungs combine CO2 with water to form carbonic acid. carbonic acid leads to a  in pH.

  9. The kidneys regulate plasma [HCO3–] through three main processes: (1) reabsorption of filtered HCO3–, (2) formation of acid, and (3) excretion of NH4+ in the urine

  10. Renal compensation begins 12-24 hr after, hyperventilation starts. • It takes 3-4 days to complete appropriate metabolic compensation.

  11. Metabolic acidosis • Metabolic acidosis may result from either increased production of metabolic acids, such as lactic acid, or disturbances in the ability to excrete acid via the kidneys, such as either renal tubular acidosis or the renal acidosis of renal failure, which is associated with an accumulation of urea and creatinine as well as metabolic acid residues of protein catabolism. • An increase in the production of other acids may also produce metabolic acidosis. For example, lactic acidosis may occur from: • severe (PaO2 <36mm Hg) hypoxemia causing a fall in the rate of oxygen diffusion from arterial blood to tissues • hypoperfusion (e.g., hypovolemic shock) causing an inadequate blood delivery of oxygen to tissues.

  12. Respiratory acidosis • Respiratory acidosis results from a build-up of carbon dioxide in the blood (hypercapnia) due to hypoventilation. • It is most often caused by pulmonary problems, although head injuries, drugs (especially anaesthetics andsedatives), and brain tumors can cause this acidemia. Pneumothorax, emphysema, chronic bronchitis, asthma, severe pneumonia, and aspiration are among the most frequent causes. It can also occur as a compensatory response to chronic metabolic alkalosis.

  13. Metabolic alkalosis • Metabolic alkalosis is a metabolic condition in which the pH of tissue is elevated beyond the normal range (7.35-7.45). This is the result of decreased hydrogen ionconcentration, leading to increased bicarbonate, or alternatively a direct result of increased bicarbonate concentrations.

  14. Respiratory alkalosis Respiratory alkalosis is a medical condition in which increased respiration elevates the blood pH beyond the normal range (7.35-7.45) with a concurrent reduction in arterial levels of carbon dioxide.

  15. Classification • There are two types of respiratory alkalosis:  • chronic and acute as a result of the 3-5 day delay in kidney compensation of the abnormality.

  16. Acute respiratory alkalosis occurs rapidly, have a high pH because the response of the kidneys is slow. • Chronic respiratory alkalosis is a more long-standing condition, here one finds the kidneys have time to decrease the bicarbonate level

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