Acid-Base Analysis

Acid-Base Analysis

Acid-Base Analysis Sources of blood acids Volatile acids Non-volatile acids H2O + dissolved CO2 Inorganic acid Organic acid H+ + HCO3- H2CO3 Lactic acid Keto

acid Henderson-Hasselbalch pH = pK + log _[HCO3]_ s x PCO2 pK = 6.1 s = 0.0301 Renal mechanisms Excrete H+ into urine Active exchange of Na+ for H+ in tubules Carbonic anhydrase, in renal epithelial cells, assures high rate of carbonic acid formation <1% urine acid is free H+ Resorb filtered HCO3-, along with Na+ Excrete H2PO4, using phosphate buffer When phosphate buffer consumed, see H+ + NH3 = NH4+ Renal Compensation Metabolic acidosis: Phosphate and ammonia buffers used as plasma bicarb is deficient Respiratory acidosis: Increased H+ excretion, HCO3- retention Metabolic alkalosis: Increased urine HCO3- excretion

Respiratory alkalosis: Decreased resorption of HCO3- Other compensation Hypokalemia Most K+ is intracellular When K+ deficient, see redistribution to extracellular space (there Ki low) H+ moves intracellularly to balance K+ (keep) exchanged for H+ in distal tubules Excrete H+, resorb HCO3- Other compensation Hyponatremia Renals Na+ resorption requires H+ excretion HCO3 resorbed Chloride

Freely exchanged across membranes (In=Ex) When chloride deficient, other anions must substituteincrease HCO3- Nomenclature Uncompensated metab acidosis Compensated metab acidosis Uncompensated metab alkalosis Compensated metab alkalosis pH pCO2 [HCO3] BE

N N

N N Partial Pressure Gas % Total

Air at sea level Partial Pressure 760 Oxygen 20.9% 159 Nitrogen 79.0% 600 Alveolar gas at sea level

CO2 Oxygen 13.3% 101 Nitrogen 75.2% 572 CO2 5.3% 40

Water 6.2% 47 pCO2 0 pO2 Atmosphere 160 40 alv

100 45 systemic circulation 97 Capillary ~47 ~47 <54 extravascular fluid <39 ~5 >55 cells <1 Cells CO2 CO2 CO2 Endothelium ECF RBC

5% Dissolved CO2 = pCO2 30% CO2 + Hb = HbCO2 65% CO2 + H2O Utilizes = HCO3 + H+ carbonic anhydrase CarboxyHgb

CO2 CO2 Transport Excretion of CO2 Metabolic rate determines how much CO 2 enters blood Lung function determines how much CO 2 excreted minute ventilation alveolar perfusion blood CO2 content Hgb dissociation curve % Sat 20

40 100 75 50 pO2 25 60 80 100 Dissociation curve % Sat 100 90

80 Shifts 70 60 50 40 30 20 10 0 0 20 40 60

pO2 80 100 Alveolar oxygen equation Inspired oxygen = 760 x .21 = 160 torr Ideal alveolar oxygen = PAO2 = [PB - PH2O] x FiO2 - [PaCO2/RQ] = [760 - 47] x 0.21 - [40/0.8] = [713] x 0.21 -[50] = 100 torr or 100 mmHg If perfect equilibrium, then alveolar oxygen equals arterial oxygen. ~5% shunt in normal lungs

Normal Oxygen Levels FiO2 PaO2 0.30 >150 0.40 >200 0.50 >250 0.80

>400 1.0 >500 Predicting respiratory part of pH Determine difference between PaCO2 and 40 torr, then move decimal place left 2, ie: IF PCO2 76: 76 - 40 = 36 x 1/2 = 18 7.40 - 0.18 = 7.22 IF PCO2 = 18: 40 -18 = 22 7.40 + 0.22 = 7.62 Predicting metabolic component Determine predicted pH

Determine difference between predicted and actual pH 2/3 of that value is the base excess/deficit Deficit examples IF pH = 7.04, PCO2 = 76 Predicted pH = 7.22 7.22 - 7.40 = 0.18 18 x 2/3 = 12 deficit IF pH = 7.47, PCO2 = 18 Predicted pH =7.62 7.62 - 7.47 = 0.15 15 x 2/3 = 10 excess Hypoxemia - etiology Decreased PAO2 (alveolar oxygen) Hypoventilation Breathing FiO2 <0.21 Underventilated alveoli (low V/Q) Zero V/Q (true shunt)

Decreased mixed venous oxygen content Increased metabolic rate Decreased cardiac output Decreased arterial oxygen content Blood gases PaCO2 : pH relationship For every 20 torr increase in PaCO2, pH decreases by 0.10 For every 10 torr decrease in PaCO2, pH increases by 0.10 PaCO2 : plasma bicarbonate relationship PaCO2 increase of 10 torr results in bicarbonate increasing by 1 mmol/L Acute PaCO2 decrease of 10 torr will decrease bicarb by 2 mmol/L

Recently Viewed Presentations

  • Warm up: (in sketchbook) Draw and label the following-

    Warm up: (in sketchbook) Draw and label the following-

    Clay was originally fired in pits, ... The Funk Art Movement. An artistic movement that began in the Bay Area of California in the 1960's. Like Pop Art, Funk Artist's often depicted objects from our consumer culture. Unlike New York,...
  • The Rime of the Ancient Mariner Part IV

    The Rime of the Ancient Mariner Part IV

    The poem is called "The Rime of the Ancient Mariner, Part IV." The Author's name is Samuel Taylor. Samuel Taylor Coleridge was born in Ottery St Mary, Devonshire. He was the youngest son out of his family. When his father...
  • Non-deterministic Tree Automata Models for Statistical ...

    Non-deterministic Tree Automata Models for Statistical ...

    Non-deterministic Tree Automata Models for Statistical Machine Translation. ChiaraMoraglia. ... Generalize the work on tree automata and tree transductions to non-deterministic models and explore the equivalence properties that were proven to hold in the deterministic case. ... Non-deterministic ...
  • The Constitution 2 Learning Objectives 2.1 2 Describe

    The Constitution 2 Learning Objectives 2.1 2 Describe

    Practice FRQ Prompt. In The Federalist Papers #10, James Madison expressed concern over the possibility that both majority and minority factions would have too much power over government, and he presented ways of minimizing that danger. The United States Constitution...
  • Course Overview CS 4501 / 6501 Software Testing

    Course Overview CS 4501 / 6501 Software Testing

    Provides host-to-host communication services: TCP, … Transports packets from host across network boundaries: IP, ICMP, … Operates on the link that a host is physically connected to: MAC (Ethernet, DSL, …) Computer network. Hypertext and the WWW.
  • Proposing, Writing and Defending a Thesis

    Proposing, Writing and Defending a Thesis

    Proposing, Writing and Defending a Thesis/Research Paper "I was working on the proof of one of my poems all the morning, and took out a comma.
  • Mr. Bufano and Mrs. Schulz-Nick have been having a ...

    Mr. Bufano and Mrs. Schulz-Nick have been having a ...

    Mrs. Schulz-Nick went to Petsmart and surveyed 100 people on what their favorite breed was, below are the results: Directions for Bar Graph Make a bar graph with the information provided x-axis must be labeled with the dog breeds y-axis...
  • Reader-Response - Mr. Lin&#x27;s Classroom

    Reader-Response - Mr. Lin's Classroom

    Reader Response Cont. The continuum of RR theory The Continuum of RR Theory Louise Rosenblatt is a "central" figure PowerPoint Presentation Questions in RR Caveats PowerPoint Presentation PowerPoint Presentation PowerPoint Presentation Strict RR responses that focus only on the reader…...