HYDROGEN ION HOMEOSTASIS

Transcription

1 ACID BASE BALANCE 1

2 HYDROGEN ION HOMEOSTASIS Free H + ions are present in very minute quantity in the blood (is around 1 in 3 million of Na + concentration) H + ion concentration is meq/l Na + ion concentration is 145 meq/l Hence Free H + ions in blood is expressed as ph, unit of expression Normal ph is 7.4 (7.35 to 7.45) 2

3 HYDROGEN ION HOMEOSTASIS CONT.. ph is defined as the negative logarithm of Free H + ion concentration Both ph and H + ion concentration are inversely related to each other Lower the ph Greater the H + ion Ex: acidosis ph <7.4 Greater the ph Lower the H + ion Ex: Alkalosis ph > 7.4 Examples of ph incompatible with life are < than 6.7 ( Acidosis ) > than 7.7 ( Alkalosis ) 3

4 SEVERE ACIDOSIS Depresses myocardium Sensitizes the heart to arrhythmias Produces arteriolar dilatation and hypo tension Predisposes to pulmonary edema 4

5 SEVERE ALKALOSIS CAN PRODUCE Tetany and convulsion Alkalosis reduces ionized Calcium Acidosis increases ionized Calcium 5

6 SOURCE OF HYDROGEN IONS IN THE BODY CO 2 ( In an adult of 70kg 530 L/ day or mm/day) Diet ( around 70 mm of H + ions daily in an adult 1mM/ kg/day) From Sulphur and Protein containing amino acids Incomplete oxidation of fats and carbohydrates ( In the absence of diet, from the body metabolism ) 6

7 BASIC PROCESS IN MAINTAINING H + ION HOMEOSTASIS Transport of CO 2 in Blood 7

8 BASIC PROCESS IN MAINTAINING H + ION HOMEOSTASIS CONT.. BICARBONATE RECLAMATION 8

9 BASIC PROCESS IN MAINTAINING H + ION HOMEOSTASIS CONT.. Thus there is no change in the Free H+ ion concentration, maintaining Hydrogen ion Homeostasis An unique buffer system for Homeostasis is CO2 production in the body results in equal amount if H + ions and HCO3 ions which is part of H 2 CO3: Na HCO3 an important buffer in the body Ex: Lactic acid + NaHCO3= Na Lactate + H 2 CO3 9

10 BASIC PROCESS IN MAINTAINING H + ION HOMEOSTASIS CONT.. H 2 CO 3 is a weak acid where there is poor ionization of H + ions due to lesser dissociation Lactic acid is a strong acid due to greater ionic state Thus NaHcO 3 converts Lactic acid into carbonic acid & hence increase in free H + ions & change in ph is minimal thus acting as an important buffer 10

11 BICARBONATES REGENERATION In an healthy adult of 70 kg 70mM HCO 3 are Regenerated in kidneys 24Hrs 70mM of H + formed in the body 24 Hrs 40 mm of HCO 3 by phosphate buffer system 30 mm of HCO 3 by ammonia buffer system 11

12 PHOSPHATE BUFFER SYSTEM 12

13 PHOSPHATE BUFFER SYSTEM CONT.. In the renal tubules HCO3 are formed from CO 2 + H 2 O H 2 CO 3 HCO 3 + H and From Glutamine through phosphate + ammonia buffer system The mechanism for bicarbonates Reclamation and regeneration are energy requiring Active processes 13

14 AMMONIA BUFFER SYSTEM 14

15 DISORDERS CONCERNING H + ION HOMEOSTASIS In acidosis H + ion increase ph decrease 15

16 RESPIRATORY ACIDOSIS Resp. acidosis Respiration depressed ph decrease pco2+hco3 increased Causes: Birth asphyxia Phenobarbitone poisoning Treatment: Treat the cause Oxygenation & ventilation 16

17 RESPIRATORY ACIDOSIS CONT In severe acute respiratory acidosis, moderate amount of NaHCO3 may be given to mitigate the serious cardiovascular effects of severe acidosis Here CO2 is Primarily predominantly increased HCO3 secondarily less predominantly increased 17

18 MODERATE ACIDOSIS ph decreased,pco2 & HCO3 decreased Ex: Hypoxia due to lactic acidosis Renal failure due to increased free H+ ion Diabetic ketoacidosis due to: Acetone,B hydroxy butric acid,&acetoacetic acid Here HCO3 Primarily predominating & CO2 secondarily less predominating 18

19 TREATMENT Treat the cause Supportive therapy Specific management is Na HCO3 Na HCO3 is never given by bolus ( except in hyperkalaemia & life threatening acidosis) NaHCO3 2mEq/kg 8 th hourly by IV infusion Each time before giving NaHCO3 a fresh assessment is made 19

20 ALKALOSIS Respiratory alkalosis Rapid breathing due to high fever due to hysterical condition Metabolic alkalosis Severe vomiting ( loss of HCl and more generation of HCO3 Ex: Infantile hypertrophic pyloric stenosis 20

21 RESPIRATORY ALKALOSIS CO2 decreased, HCO3 decreased Here CO2 is primarily predominantly reduced HCO3 is secondarily, less predominantly decreased In both respiratory and metabolic alkalosis ph increased 21

22 METABOLIC ALKALOSIS HCO3 increased, CO2 increased Here HCO3 is primarily, predominantly elevated. CO2 is secondarily less predominantly elevated 22

23 PRINCIPLES IN THE MANAGEMENT OF ALKALOSIS Volume contraction should be corrected In volume deficit additional aldosterone is secreted, absorbing Na + and secreting H + & K + ions, thus perpetuating alkalosis Any existing hypokalemia should be corrected otherwise to preserve K + ion, H + ion is secreted out, thus perpetuating alkalosis Any hypochloremia must be corrected. NaCl is absorbed as such as otherwise Na+ is absorbed in exchange of H + ion or K + ion aggravating alkalosis 23

24 CORRECTION IN ALKALOSIS Fluid of choice NaCl ( Saline ) solution 24

25 MIXED DISORDERS Is a combination of 2 or more abnormal process Respiratory acidosis Metabolic acidosis Respiratory alkalosis Metabolic alkalosis 25

26 MIXED DISORDERS EXAMPLES Bronchopneumonia with high fever (rapid breathing) Metabolic acidosis + Respiratory alkalosis (hypoxia) (rapid breathing) Phenobarbitone poisoning Respiratory acidosis + metabolic acidosis (Respiratory center depression + hypoxia) ph, CO2 & HCO3 levels depend on severity of the components (Respiratory or metabolic) affected and Correction depend on it 26

27 Thank You 27