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INTRODUCTION TO ACID- BASE DISORDERS

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objectives

Interpretation of ABG Acid Base status Respiratory disorders Metabolic disorders
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[H+] =40meq/lit ----- PH---7.4 pH ---- negative base 10 log of the hydrogen ion conc. Relation of [H+] to pH is nearly linear at the range of 7.2---7.5 0.01 unit of pH --- 1 meq /lit change of [H+]
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PLASMA ACID HOMEOSTASIS

Plasma [H] influenced by 1- endogenous production 2- rate of excretion 3- body buffers
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A buffer is a weak acid and its base : [HA] [H+] + [A-] [H+] = K [HA] / [A-]
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pH = pK + log [HCO3-] / [H2CO3] Henderson -Hasselbach equation

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Acid Production &Excretion

Bicarbonate -carbonic acid buffer is open & not fixed ---- by 1-pulmonary CO2 excretion 2-renal excretion and formation of bicarbonate Note: pulmonary ----- immediate renal ----- hours to days
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BLOOD GAS

pH = 7.35-7.45 PCO2= 35-45 mmHg [HCO3-] = 21-28 meq/lit PO2 = 75 -100 mmHg O2% = 95-99%
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FUNDAMENTAL ACID -BASE DISORDERS

Disorders lead to HIGH [H] --- LOW pH = ACIDOSIS Disorders lead to LOW [H] ---- HIGH pH = ALKALOSIS ACIDEMIA ALAKLEMIA
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RESPIRATORY PROBLEM ---- FIRST AFFECT PCO2 METABOLIC PROBLEM --- FIRST AFFECT BICARBONATE. SO PCO2 DETERMINE pH IN RESP. PROBLEM AND SO FOR THE BICARBONATE IN METABOLIC IF NO COMPENSATION
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COMPENSATION RETURN pH TOWARD BUT NOT TO NORMAL COMPENSATION NEVER EXCEED NORMAL

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ACID-BASE IMBALANCE
RESPIRATORY PROBLEMS: Respiratory Acidosis: 1- Low pH 2- Pco2 > 40mmHg 3- inadequate elimination of co2 by the lungs
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Resp. cont.

CNS lesions Sedatives Neuromuscular disorders Asthma and COPD
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TREATMENT OF UNDERLYING CAUSE ASSISTED VENTILATION Pco2 > 60 mmHg

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RESPIRATORY ALKALOSIS 1- INCREASED PH 2-DECREASED Pco2 DUE TO EXCESSIVE ELIMINATION OF CO2 FROM THE LUNGS
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ANXIETY HYPOXIA PREGNANCY EARLY G-ve SEPSIS

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TREAT PRIMARY CAUSE NO DIRECT TREATMENT

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METABOLIC ACIDOSIS: 1-DECREASED BLOOD pH , 2-DECREASED BICARBONATE LESS THAN 24mEq/L
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TREATED BY SODIUM BICARBONATE pH less than 7.2 TREAT THE PRIMARY CAUSE
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METABOLIC ALKALOSIS

Increase pH , increase plasma bicarbonate CAUSES VOMITING DIURETICS CS
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TREAT UNDERLYING CAUSE VOLUME EXPANTION BY NaCl SOL.

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THANK YOU

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