Acid, Base, Electrolytes
Regulation for BALANCE
Fluid Compartments
Fluid Compartments:20 – 40 – 60 Rule
Fluid Movement
Water and Electrolyte Balance Input = output Hormones
• Na+ / K+• Renin• Aldosterone• ANP• Reproductive Hormones• GCC
• Ca++ / Mg++• Calcitonin• PTH
• H2O• ADH
Anions follows passively• Cl-• HCO3-
Electrolyte Fluid Composition
Cations and Anions balance for Electroneutrality
Acid Base Terms Define
• pH• Acid
• Strong• Weak• Volatile : CO2 from CH20 and Fat Metabolism• Nonvolatile: H2SO4, H2PO4 from protein metabolism
• Base• Strong• Weak
• Salt• Buffer
Acid Sources
pH Define
• pH = log (1/[H+])• pH = -log [H3O+]
Water Dissociation• H2O + H2O
H3O+ + OH- Scale Blood values
• Venous• Arterial
Abnormal Values• Acidemia• Alkalemia
pH formula and scale
Acid Base Chart
pH of Solutions
Acid Base Regulation for Balance Systems
• Chemical Buffer Systems• Respiratory System• Renal
Time• Seconds to Minutes• Minutes to Hours• Hours to Days / Weeks
Strength Problems (reference 7.4 as normal average):
• + / - 0.1 changes result in respiratory rate changes• + / - 0.2 to 0.3 changes result in CV and Nervous changes• + / - 0.4 to 0.5 changes result in death
Chemical Buffer Systems Define 3 types
• Name of System• Buffer formula or name of chemical• Location• Effectiveness [pKa buffer = pH location]• Why important
pH changes with/without buffers
Buffer EffectivenessHA [H+] + [A-] pKa = -logKa
Titration of Buffer System
pK of Bicarbonate System
Formulas K = [H+] [HCO3-] / [H2CO3] pH = log (1 / [H+]) Henderson-Hasselbach Equation:
CO2 is directly related to H2CO3, as CO2 + H20 H2CO3; can substitute this equivalent [amount x solubility coefficient] in the above equation (0.03 X pCO2)
Bicarbonate Chemical Buffer H2CO3, HCO3- Plasma buffer pK = 6.1 Important:
• Can measure components• pCO2 = 40 mmHg• HCO3- = 24 mM
• Can adjust concentration / ratio of components • HCO3- @ kidneys• CO2 @ lungs
• Recalculate pH of buffer system in ECF using Henderson-Hasselbach• pH = 6.1 + log(24 / 0.03x40)
• pH = 6.1 + log (20/1)• pH = 7.4
Bicarbonate pK
Bicarbonate Buffer System
Phosphate Chemical Buffer H2PO4-, HPO4= ICF, Urine pK = 6.8 Important
• Intracellular buffer• ICF pH = ~ 6.5 – 6.8
• Renal Tubular Fluids• Urine pH ranges 6.0 – 7.0
Protein Chemical Buffer Proteins
• With Histadine: AA contain imidazole ring, pKa = 7.0• R-COOH R-COO- + H+• R-NH2 R-NH3+
ICF (hemoglobin), ECF pK = 7.4 Important
• Most numerous chemicals• Most powerful chemical buffer
Proteins in acid base
Acid-Base Properties of Alanine
Hemoglobin
Protein Chains
Hemoglobin Buffer for H+
CO2 transport and RBC buffer
Respiratory for A/B Balance
Occurs in minutes CO2 only Rate changes
Respiratory Controls for Acid /Base balance Volatile Acid: CO2 pH changes in CSF Respiratory Rate
• Pons• Medulla Oblongata
Chemoreceptors• pCO2• pO2
CO2 and pH
Increase CO2• Increase H+
• Decrease pH Decrease CO2
• Decrease H+• Increase pH
Renal Control for Long Term Acid / Base Balance
Renal processes in A/B balance
Renal Physiology Filtration
• Remove metabolic acids: Ketones, Uric acid
• Filter Base [HCO3-] @ Renal Filtration Membrane
Reabsorption• Base @ PCT• Reverse CO2 equation to
create HCO3- Secretion
• H+ @ PCT, late DCT and Cortical CD
• CO2 equation to create H+ for secretion
Renal Mechanisms for A/B
Renal Ion Exchanges Na+ / K+ antiporter Na+ / H+ antiporter Na+ / HCO3- cotrans H+ / K+ ATPase H+ ATPase Cl- / HCO3-
exchanger
Renal Reabsorption of HCO3-
Renal Movement of Ions andCO2, HCO3-, and H+ Acidic Urine
Renal Tubular Buffer:Phosphate Buffer System
Use of HPO4 buffer system
Ammonium Buffer System in Renal Tubules
Deamination of Glutamine creates HCO3- for more base creates NH3 for buffering H+
Increase of HCO3- Buffer
Renal Buffer Mechanisms
Normal Acid Base Values
Respiratory and Renal Balance
Acid-Base Problems Acidosis
• State of excess H+ Acidemia
• Blood pH < 7.35 Alkalosis
• State of excess HCO3- Alkalemia
• Blood pH >7.45
Classifying Respiratory Acid Base Problems (pCO2 changes) Respiratory Acidosis
• Respiratory Rate Decreases• Any Respiratory Disease
• Obstruction• Pneumonia• Gas exchange / transport problems
• Respiratory Membrane• RBC / Hemoglobin
Respiratory Alkalosis• Respiratory Rate Increases
Classifying Metabolic Acid Base Balance Problems (H+/ HCO3-) Systems
• Renal • Endocrine• GI• Cardiovascular / Fluid administration
Metabolic Acidosis• Retain Acid• Lose Base
Metabolic Alkalosis• Retain Base• Lose Acid
Other System diseases in Metabolic Acid/Base Problems
GI • Vomiting• Diarrhea• Medications : Antacids
Endocrine• DM• Hyperaldosteronism
Metabolism• Increase acid production
Ketones
ECF Cations, Anions, and Anion Gap
Anion Gap• Difference between
major plasma cations and major plasma anions
AG = ([Na+] + [K+]) – ([Cl-] + [HCO3-])
Normal AG = 12 +/- 4
Check in metabolic Acidosis to help identify non-measured acids
Compensation
Adjustments for Acid/Base Balance Imbalance
• Respiratory Acidosis• Incr pCO2
• Respiratory Alkalosis• Decr pCO2
• Metabolic Acidosis• Decr HCO3-• Incr H+
• Metabolic Alkalosis• Incr HCO3-• Decr H+
Compensation• Increase renal acid
excretion, Incr HCO3-
• Decrease renal acid excretion, decr HCO3-
• Hyperventilate to lower pCO2
• Hypoventilate to increase pCO2
Compensation Summary
Summary for A/B Balance