Download Blood Gas Analysis

INTRODUCTION TO ACID
- BASE DISORDERS
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objectives
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Interpretation of ABG
Acid Base status
Respiratory disorders
Metabolic disorders
• [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
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PCO2= 35-45 mmHg
[HCO3-] = 21-28 meq/lit
PO2 = 75 -100 mmHg
O2% = 95-99%
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.
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CNS lesions
Sedatives
Neuromuscular disorders
Asthma and COPD
• 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
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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