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

  • Acid Strength: STRONG ACIDS

    Acid Strength: STRONG ACIDS

    Acid Strength: STRONG ACIDS REVIEW: Strong acids dissociate completely in water (strong electrolytes) HA(aq) + H2O(l) <-> H3O+(aq) + A-(aq) Acid Base Conjugate A. C.B. Equilibrium lies far to the RIGHT (almost all of the HA dissociates at equilibrium) A...
  • cs2220: Engineering Software Class 19: Java Security Fall

    cs2220: Engineering Software Class 19: Java Security Fall

    TheStringis really a reference to an entry in the string constant table! The strange String semantics should make more sense now. Arithmetic. Opcode. Mnemonic; Description; 96. iadd. Pops two integers from the stack and pushes their sum. iconst_2. iconst_3. iadd....
  • New Directions in Quantitative Finance

    New Directions in Quantitative Finance

    Canada Research Chair in Quantitative Finance, Western University Canada ... let Split integral to get Moving towards Bellman's equation Standard Taylor Series arguments Employ Ito's lemma to obtain Taylor series Eliminate all higher order terms and simplify Take expectations and...
  • Paradigms, Revolutions, Changes in World View

    Paradigms, Revolutions, Changes in World View

    Paradigms determine out data. Our observations are "theory laden". Psychology had recently been uncovering just how susceptible we are to illusions and cognitive bias. Btw, Popper spent a lot of time arguing for this as well. This is how he...
  • CSE190 Winter 2020 Lecture 3 Time and Interrupts

    CSE190 Winter 2020 Lecture 3 Time and Interrupts

    - [Stopwatch, UI, Buzzer] Processor's . timer. peripheral with interrupts (when communicating | usec) - [WiFi] WiFi chip's internal timer peripheral with interrupts. The term is used to avoid confusion with ordinary hardware clocks which are only signals that govern...
  • Chapter 1, Heizer/Render, 5th edition

    Chapter 1, Heizer/Render, 5th edition

    Method 2: Determine the effective interest rate for any time period t, and ... An equivalent annual worth value can be obtained by replacing each cash flow . amount with 'A' and setting the equation equal to the calculated P...
  • Men Should Weep - St Roch&#x27;s Secondary School

    Men Should Weep - St Roch's Secondary School

    Men Should Weep by Ena Lamont Stewart Contemporary Scottish Theatre Exam questions Men Should Weep should be used to answer questions on: Social, political and religious dimensions or Issues of gender Scottish History Glasgow took the brunt of the depression...
  • Communication 166 Research Methods

    Communication 166 Research Methods

    Communication 166 Research Methods Dr. Dev Sharma Alternative Knowledge Claim Positions Postpositive Constuctivism Advocacy/Particpatory Pragmatism Postpositivism -Knowledge is conjectural- Data, evidence, and rational considerations shape knowledge.