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