Post on 03-Jan-2016
Acid-Base Basics
Chemistry of Life
Acid-Base Balance: Basics Chemistry Facts
Acid gives up a hydrogen ion Proton donors [H+]
A base/alkali accepts a hydrogen ion Proton acceptor [H+] Major base in the body: BICARBONATE
(HCO3) Acids react w/carbonates & bicarbonate to
form CARBON DIOXIDE Carbon Dioxide
Major lung chemical [acid]
Acids react with bases to form H2O and a salt = Neutralization reaction because both the Acid and Base are neutralized i.e. Carbonic acid= HCO3 + H+ = Carbon dioxide +
Water2
Release/donate H ions when Dissolved in H2O.
Bases
Homeostatic Mechanisms
Ph Body fluid ph:
measure of the body’s fluid free H+ ion level
Buffer systems [chemical] Bicarbonate Phosphate Protein/Hemoglobin
Kidneys Lungs
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pH Concentration of hydrogen (H) in a
solution A chemically neutral solution has a
pH of 7.00 Normal body pH is 7.35–7.45
Below 7.25 or above 7.55 is considered life-threatening
Above 7.8 (alkalosis) or below 6.8 (acidosis) usually is fatal
7.4 indicates a ratio of 20 parts bicarbonate [base] to 1 part carbonic acid
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Buffer Systems Buffers-
Chemically change strong acids into weaker acids or to bind acids to neutralize their effect Primary regulator of acid-base
balance Function:
Minimize effect of acids on blood pH Three other buffer systems in the body include
Phosphate, Protein/Hemoglobin
Acid-Base Regulation: Buffer System Bicarbonate buffer systems
Body’s primary buffer system Buffers blood and interstitial
fluids Bicarbonate-carbonic BS
Buffer system maintains 20:1 ratio between bicarbonate & carbonic acid & normal pH
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Respiratory Buffer: Lungs
Under control of _________: control/regulate blood levels of CO2 & the H2CO3 content
CO2: powerful stimulator of resp. center Chemoreceptors (Brain):
Sense pH change & vary rate & depth of breathing to regulate CO2 levels Hypoventilate & hyperventilate respiratory acidosis and alkalosis
To assess effectiveness of ventilation: PaCO2 (Partial pressure of carbon dioxide in arterial blood) Normal PaCO2 : 35-45 mm Hg7
CO2 & Hyperventilation
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RR
CO2
Blowing off CO2
pH
CO2 & Hypoventilation
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RR
CO2
Body retains
pH
Renal Control: Kidney Kidneys: 3rd line of defense Movement of bicarbonate: 1st renal control
mechanism Change the excretion rate of acids and the
production and absorption of bicarbonate ion Formation of acids: 2nd renal control
[phosphate buffering system] Formation of ammonium: 3rd renal control Slow to compensate but are the most
effective compensating mechanism10
Helping Out: Bicarbonate System
Lungs assist by:
______________________________
Kidneys: __________________________
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Acid – Base Balance
CO2 + H20 H2CO3 H+ + HCO3-
LungsLungs
RespiratoryRespiratory
FastFast
Kidneys Kidneys
MetabolicMetabolic
SlowSlow
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What Happens?• When either the HCO3
- or H2CO3
increases or decreases resulting in 1:20 ratio no longer being maintained:
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Acid-Base Balance
pH: 7.35-7.45PaCO2: 35-45 mm HgHCO3: 22-26 mEq/L
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Acid-Base Balance
Base deficit/Excess:-2 to +2 mEq/L
SaO2 saturation: >95% to 100%
PaO2: 80-100 mm Hg
Factors Affecting Acid-Base/BodyFluids/E-Lytes
Age Gender & body size Illness Medical dx, meds & surgery
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Elevator Effect
Anion Gap
Cation-anion difference Relationship among body cations
(+) & anions (-) Helpful in dx & treating acidotic
conditions Increases in gap = too much acid
in blood (acidosis) due to i.e. DKA, Lactic acidosis
Looking at the “+” & “-” Side of Things
CATIONS
“+” charged ion Types
____, ____ ____ , ____
ANIONS
[-] charged ion Types
______ ______ ______
Anion: A Negative ION
Anion Gap
22
140 – (25+105)=
140 - (130) = 12 mEq/L
GAP= 10 (Normal)
Normal value: 8-16 mEq/L
Important in analyzing acid-base disorders
Anion Gap High Anion gap m. acidosis
Too much acid accumulated Seen with Lactic acidosi, DKA,
Hyperchloremia
Normal anion gap [aka as hyperchloremic m. acidosis] Direct loss of HCO3 ion
Diarrhea, fistula (GI) or renal causes
Abnormally low gap: HYPONATREMIA, multiple myeloma [Bone Cancer]