Upload
a-j-institute-of-medical-sciences-mangalore-and-international-medical-school-malaysia
View
199
Download
2
Tags:
Embed Size (px)
DESCRIPTION
Teachers and students
Citation preview
04/13/2023 Dr. Ashok Kumar J; IMS; MSU 1
RENAL REGULATION OF pH
Dr. Ashok Kumar JInternational Medical School
Management and science universityMalaysia
04/13/2023 Dr. Ashok Kumar J; IMS; MSU 2
RENAL MECHANISM
Kidney plays a major role in acid-base regulation
2. Reclamation the bicarbonate ions present in the ultra-filtrate
1. Excretion of H+
3. Excretion of titrable acid 4. Excretion of ammonia
04/13/2023 Dr. Ashok Kumar J; IMS; MSU 3
1. EXCRETION OF H+
- Occurs in proximal tubule
- CO2 combines with H2O to form H2CO3
- It dissociates to form HCO3- and H+
- H+ is secreted in exchange for Na+
- Net production of HCO3- and net excretion
of H+
- mechanism serves to increase
the alkali reserve
HCO3-HCO3
-
H2O + CO2 H2CO3-
H+ H+
Tubular cellTubular Lumen
Na+Na+
04/13/2023 Dr. Ashok Kumar J; IMS; MSU 4
HCO3-HCO3
-
H2O + CO2 H2CO3-
H+ H+HCO3
-+
H2CO3-
H2O CO2 + CO2
Tubular cell Tubular Lumen
2. RECLAIMATION THE BICARBONATE IONS PRESENT IN THE ULTRAFILTRATE
04/13/2023 Dr. Ashok Kumar J; IMS; MSU 5
HCO3-
H2O + CO2 H2CO3-
H+
NH4+
H+
Tubular cell
Tubular Lumen
NH3
Titrable acid
Na2HPO4-
NaH2PO4-
GLUTAMIN
GLUTAMATE
Glutaminase NH3
04/13/2023 Dr. Ashok Kumar J; IMS; MSU 6
•NH3 (ammonia) freely crosses the cell membrane enters the lumen of renal tubule
•Combines with protons present in the filtrate to form NH4 (ammonium ions)
•Ammonium ions are impermeable through the cell membrane – excreted in urine
•Daily excretion in urine 60 mEq/L of H+ excreted as Ammonia
04/13/2023 Dr. Ashok Kumar J; IMS; MSU 7
When there is an excess of acid production in the body, H+ are excreted in urine as titrable acid and ammonia
• Titratable acidity of urine : The number of milliliters of N/10 (0.1N) NaOH
required to titrate 1 liter of urine to pH 7.4.
• This is a measure of net acid excretion by the kidney
04/13/2023 Dr. Ashok Kumar J; IMS; MSU 8
Anion GapIn Extracellular fluidSum of anions = Sum of cations - Electrical neutrality
•Sodium (Na+) and Potassium (K+) together accounts for 95% of the cations
•Chloride and bicarbonate accounts for only 86% of the anions
• Measured cationsSodium 136 mEq/LPotassium 4 mEq/L
• Unmeasured CationCalcium 4.5 mEq/LMagnesium 1.5 mEq/L
• Measured anionsChloride 98mEq/LBicarbonate 25mEq/L
• Unmeasured anionProtein 15mEq/LPhosphate 2mEq/LOrganic acids 5mEq/LSulfate 1mEq/L
04/13/2023 Dr. Ashok Kumar J; IMS; MSU 9
• Unmeasured anions constitute the anion gap
• Calculated as difference between measured cations and measured anions
Anion Gap = (Na+ + K+) - (Cl- + HCO3-)
• Normal is about 12 mEq/L
e.g: = ( 140 + 4) – (103 + 25) = 16
04/13/2023 Dr. Ashok Kumar J; IMS; MSU 10
Disturbance in acid base balance
Acidosis : Clinical state where acids accumulate or bases are lost Alkaosis : Clinical state where accumulation of base or loss of acids
[Bicarbonate]pH = pKa + log10
[Carbonic acid]
04/13/2023 Dr. Ashok Kumar J; IMS; MSU 11
[Bicarbonate][Carbonic acid]
pH = pKa + log10
Regulated by KidneyMetabolic component
Decreased BicarbonateDecreases the ratioDecreases pHMETABOLIC ACIDOSIS
ACIDOSIS
Metabolic acidosis :- Primary alkali (bicarbonate) deficit
04/13/2023 Dr. Ashok Kumar J; IMS; MSU 12
[Bicarbonate][Carbonic acid]
pH = pKa + log10
Regulated by KidneyMetabolic component
Increased BicarbonateIncreases the ratioIncreases pHMETABOLIC ALKALOSIS
ALKALOSIS
Metabolic alkalosis :- Primary alkali (biocarbonate) excess
04/13/2023 Dr. Ashok Kumar J; IMS; MSU 13
Metabolic acidosis
Increased production of hydrogen ions
• Diabetic ketoacidosis ; Starvation ketoacidosis; Lactic acidosis ; Salicylate intoxication
Impaired excretion of hydrogen ions
• Renal failure ; Renal tubular acidosis type II
Loss of bicarbonate from the gastrointestinal tract or in urine
• Severe diarrhoea ; Renal tubular acidosis type I; Ureterosigmoidostomy
04/13/2023 Dr. Ashok Kumar J; IMS; MSU 14
Loss of bicarbonate a. From gastrointestinal tract as in • severe diarrhoea
b. From the kidney as in• Ureterosigmoidostomy• Renal tubular acidosis
is replaced by chlorideResults in hyperchloremic acidosis
04/13/2023 Dr. Ashok Kumar J; IMS; MSU 15
04/13/2023 Dr. Ashok Kumar J; IMS; MSU 16
BUFFER SYSTEM
Mainly bicarbonate buffer minimizes change in pH
HCO3 concentration is decreased and ratio of HCO3/H2 CO3 less than 20/1
RESPIRATORY MECHANISM
Increases rate and depth of respiration (Kussumauls breathing)
Elimination of carbonic acid as CO2 ,
Decrease in pCO2 and consequently decrease in H2CO3
04/13/2023 Dr. Ashok Kumar J; IMS; MSU 17
RENAL compensation seta in 2 to 4 days
Increases excretion of acid and preserves the base by increased rate of
Na- H exchange
Increases ammonia formation and increased reabsorption of HCO3
04/13/2023 Dr. Ashok Kumar J; IMS; MSU 18
• Uncompensated Metabolic acidosis• Partially compensated Metabolic acidosis• Compensated Metabolic acidosis
Fully compensated
Partially compensated
uncompensated
Normal decreased decreased pHDecreased decreased normal pCO2
Decreased decreased decreased HCO3
pO2
04/13/2023 Dr. Ashok Kumar J; IMS; MSU 19
Metabolic alkalosis• Raise in the plasma bicarbonate• Loss of H+ ions
CAUSES : • Loss of gastric juice along with H+ ions as in
- prolonged vomiting, - Nasogastric succion etc
•Therapeutic administration of large dose of alkali – chronic intake of excess antacids - Intravenous administration of bicarbonateetc
04/13/2023 Dr. Ashok Kumar J; IMS; MSU 20
RESPIRATORY MECHANISM:
Increase in pH depresses the respiratory center, causes retention of CO 2
pCO2which in turn increases the H 2CO 3 .
RENAL MECHANISM:
Kidney decreases H+ excretion
decreased reclamation of bicarbonate.
COMPENSATORY MECHANISM
04/13/2023 Dr. Ashok Kumar J; IMS; MSU 21
Fully compensated
Partially compensated
uncompensated
normal increased increased pHincreased increased normal pCO2
increased increased increased HCO3
pO2
04/13/2023 Dr. Ashok Kumar J; IMS; MSU 22
Thank you