DR Medhat MRCP

o Treatment of chronic respiratory acidosis :
1. long term oxygen therapy (LTOT)
Indications (e.g in COPD) :
a) FEV1 30% of the time).
2. Nocturnal NIV (BIPAP):
Used in COPD with chronic hypoventillation causing chronic CO2
retention& respiratory acidosis
Initially over-night monitoring of pco2 &PO2 has to be done to assess
over-night gas exchange & decide nocturnal BiPAP.
As the disease progress , the need for BiPAP will increase for longer time
3. Treatment of the underlying etiology .
Metabolic alkalosis :
o May be caused by a loss of hydrogen ions or a gain of bicarbonate.
o It is due mainly to problems of the kidney or gastrointestinal tract
o Features :
1. High plasma HCO3 -
2. High plasma pH > 7.45
3. Compensatory in PCO2 by 0.6-0.7 per every 1 mmol/L increase in
Plasma HCO3 -
o Causes
1. Vomiting / aspiration (e.g. Peptic ulcer leading to pyloric stenosis, nasogastric
suction).
2. Diuretics (= contraction alkalosis i.e loss of water to ECF & HCO3 - retention in
blood.
3. Liquorice, carbenoxolone .
4. Hypokalemia.
5. Primary hyperaldosteronism.
6. Congenital adrenal hyperplasia.
7. Cushing's syndrome.
8. Bartter's syndrome
Mechanism of metabolic alkalosis
1. Activation of renin-angiotensin II-aldosterone (RAA) system is a key factor
2. Aldosterone causes reabsorption of Na+ in exchange for H+ in the distal
convoluted tubule
3. ECF depletion (vomiting, diuretics) Na+ and Cl - loss activation of RAA
system raised aldosterone levels
4. In Hypokalemia, K+ shift from cells ECF. Alkalosis is caused by shift of H+
into cells to maintain neutrality.
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