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Acid-Base Balance
KNH 413
Acid-Base Balance
AcidsDonate or give up H+ ions
Rise in pH as a result! Nonvolatile acids or fixed acids
CO2 indirect measure of production of acid b/c of rise of pH
Inorganic acids that occur through metabolism of CHO, protein, lipid
Average amount 50-100 mmol/day Proteins contribute the most Lungs cannot eliminate
Acid-Base Balance
BasesCan accept or receive H+ ions
Ex: bicarbonate Bicarbonate HCO3
Kidneys provide primary regulation of acid base balance
Dialysis patients deal with this on a weekly basis
Acid-Base Balance
pHAcidosis
Accumulation of acid or loss of base
Acidemia (*main concern)pH < 7.35 (stomach acid)
AlkalosisAccumulation of base or loss of acid
AlkalemiapH > 7.45 (pancreatic juice & bile)
Regulation of Acid-Base Balance
Chemical buffers-aid in maintaining balance# 1. bicarbonate increases rate and depth of
breathing b/c increases the amount of CO2 production
Respiratory regulation—to excrete more CO2
Kidney regulation—work to reabsorb more bicarbonate if in an acidodic condition
Regulation of Acid-Base Balance
Respiratory regulatory control:
Change in respiration rate
Depth of breathing
Release or retention of CO2
Regulation of Acid-Base Balance
Renal regulatory controlControl of HCO3 (bicarbonate) by the kidneys that is
excreted Increased or decreased bicarbonate absorption
based on needFormation of dibasic phosphate and sulfur in the
urine Accepts H+
Regulation of Acid-Base Balance
Electrolyte Balance 1. Blood 2. Urine 3. ?
Hydrogen and bicarbonate both electrolytesOther electrolytes affected to maintain
electroneutralityPotassium, chloride, sodium—constantly looking at
these blood values and altering them if necessary
Acid-Base Disorders4 major types
Respiratory acidosis: lower pH, higher plasma bicarbonate, increased CO2 production Trying to excrete more hydrogen to regulate this
Respiratory alkalosis: higher pH, lower plasma bicarbonate, decreased CO2 production
Metabolic acidosis: most common; lower pH, decreased plasma bicarbonate, decreased CO2 Hyperventilation situation; hydrogen being excreted at a
higher level
Metabolic alkalosis: increased pH, increased plasma bicarbonate, increased CO2 production Hypoventilation
Acid-Base Disorders
Respiratory acidosisExcess acid in blood secondary to carbon dioxide
retentionHypercapnia—too much CO2 in the bloodCommon causes d/t respiratory dysfunction – renal regulatory
systems compensate
Acid-Base Disorders
Respiratory acidosisLabs
Decreased pH, elevated pCO3
Slightly elevated bicarbonate Increase in serum Ca, K, Cl
Hypoxemia—inability of oxygen to flow throughout the blood
Restlessness, apprehension, lethargy, muscle twitching, tremors, convulsions, coma
Acid-Base Disorders
Respiratory acidosis
Treatment
Correct underlying condition Increase oxygenation—increasing or decreasing
ventilation Mechanical ventilation
Acid-Base Disorders
Respiratory alkalosis—hyperventilation Relative excess amount of base d/t reduction of CO2
HyperventilationCommon causes - see Table 9.6Shift of acid from ICF to ECF Bicarbonate moved into cells in exchange for
chloride – renal compensation
Acid-Base Disorders
Respiratory alkalosispH > 7.45 Plasma HCO3 low in chronic, PaCO3 low in acute
Cardiac, CNS, respiratory symptomsTreat underlying causeCorrection of hypoxia
Acid-Base Disorders
Metabolic Acidosis All types not caused by excessive CO2
Common causes **Diarrhea most common cause
d/t excessive loss of bicarbonate – bicarbonate-carbonic acid buffer system is stimulated
Fistula drainage may occur
© 2007 Thomson - Wadsworth
Acid-Base Disorders
Metabolic Acidosis Kussmaul breathing—deep labored breathing
Common in DKA
Cardiac and neurological—insult to heart/neurological as a result of being acidotic (not the norm)
Treat underlying cause Raise pH to safe level – not too quickly
Acid-Base Disorders
Metabolic Alkalosis—RARE Excess amount of base (too much acetate in
solution) Fluid imbalance – with volume decrease Without fluid imbalance – without volume
decrease Common causes Underlying event determines pathophysiology
Assessment of Acid-Base Disorders
© 2007 Thomson - Wadsworth