KAAP221 Lecture Notes - Lecture 25: Respiratory Acidosis, Respiratory Alkalosis, Metabolic Acidosis
11 May 2018
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Lecture 25
• Acid-base balance disorders
• Metabolic acid-base disorders
• Result from production or loss of excessive amounts of fixed or organic acids
• Carbonic acid-bicarb buffer system protects against these
• Respiratory acid-base disorders
• Result from imbalance of CO2 generation and elimination
• Carbonic acid-bicarb buffer system cannot protect against respiratory disorders
• Imbalances must be corrected by change in depth and rate of respiration - because they’re
caused by something to do with respiration
• Metabolic acidosis
• Develops when large numbers of H+ released by organic or fixed acids and pH decreases; due to
severe diarrhea, untreated diabetes mellitus, kidney disease, and starvation
• Responses to restore homeostasis involve: increased respiratory rate, lowering PCO2 levels;
converting more carbonic acid to H2O
• Renal response - secrete more H+ into the tubular fluid which then allows your body to get rid of
that excess H+, in PCT, DCT, and collecting system; tubule cells secrete more H+ ions into urine;
reabsorbing more bicarb to help replenish bicarb reserve within the body
• Metabolic alkalosis - pH is higher
• Develops when large numbers of H+ removed from body fluids, raising pH
• Due to excessive/prolonged vomiting, selected diuretics, ingestion of excessive sodium bicarbonate
(antacid)
• Kidney responses include:
• Rate of kidney H+ secretion declines
• Tubular cells do not reclaim HCO3- - it’s not secreted, getting rid of it
• Collecting system transports HCO3- into tubular fluid (urine) and release HCl into ECF
• Responses to restore homeostasis involve:
• Respiratory rate - decreased to raise PCO2 levels, to convert more CO2 to carbonic acid
• Renal response - conserving more H+ and excreting more HCO3-
• Respiratory acid-base disorders
• Imbalance between rate of CO2 generation in body tissues and rate of CO2 elimination at lungs -
cannot be corrected solely by carbonic acid-bicarb buffer system
• Respiratory acidosis (increasing PCO2 caused by hypoventilation)
• Rate of CO2 generation > rate of CO2 removal
• PCO2 above 45 mmHg
• Shifts H2CO3 - HCO3- buffer system to right, generates more HCO3- and releases more H+ ions
• HCO3- goes into bicarb reserve
• Excess H+ must be taken care of by other buffer systems or excreted by kidney
• Underlying problem cannot be corrected with increase in RR
• Responses involve:
• Increased RR
• Increased H+ secretion by kidneys and reabsorption of HCO3- ions (keep more HCO3- in
body to buffer)
• Other buffer systems accept H+ ions
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Document Summary
Lecture 25: acid-base balance disorders, metabolic acid-base disorders, respiratory acid-base disorders. Result from production or loss of excessive amounts of fixed or organic acids. Result from imbalance of co2 generation and elimination. Carbonic acid-bicarb buffer system cannot protect against respiratory disorders. Tubular cells do not reclaim hco3- - it"s not secreted, getting rid of it. Respiratory rate - decreased to raise pco2 levels, to convert more co2 to carbonic acid. Renal response - conserving more h+ and excreting more hco3- Rate of co2 generation > rate of co2 removal. Shifts h2co3 - hco3- buffer system to right, generates more hco3- and releases more h+ ions. Excess h+ must be taken care of by other buffer systems or excreted by kidney cannot be corrected solely by carbonic acid-bicarb buffer system: respiratory acidosis (increasing pco2 caused by hypoventilation) Underlying problem cannot be corrected with increase in rr.
