acid, base, electrolytes regulation for balance. fluid compartments
TRANSCRIPT
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-
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
pH Define
• pH = log (1/[H+])• pH = -log [H3O+]
Water Dissociation• H2O + H2O
H3O+ + OH- Scale Blood values
• Venous• Arterial
Abnormal Values• Acidemia• Alkalemia
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
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
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
Respiratory Controls for Acid /Base balance
Volatile Acid: CO2 pH changes in CSF Respiratory Rate
• Pons
• Medulla Oblongata
Chemoreceptors• pCO2
• pO2
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 Ion Exchanges
Na+ / K+ antiporter Na+ / H+ antiporter Na+ / HCO3- cotrans H+ / K+ ATPase H+ ATPase Cl- / HCO3-
exchanger
Ammonium Buffer System in Renal Tubules
Deamination of Glutamine creates HCO3- for more base creates NH3 for buffering H+
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
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
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