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): + / changes result in respiratory rate changes + / to 0.3 changes result in CV and Nervous changes + / 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 Effectiveness HA  [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 kidneys lungs Recalculate pH of buffer system in ECF using Henderson-Hasselbach pH = log(24 / 0.03x40) pH = 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 Renal Filtration Membrane Reabsorption PCT Reverse CO2 equation to create HCO3- Secretion 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 and CO2, 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