Acid Base Balance Flashcards
Describe what metabolic acid-base alterations can lead to.
- Altered CVS function
- Altered neuro function
- Altered resp function
- Altered response to drugs
Describe the effect of pH in the body.
-altered H ion conc affect structure of proteins, function of enzymes, receptors, transport proteins, channels, etc
-constant pH needed for cell function
-abnormal H conc = adverse effect on function of all organ systems
>conc of H ions in ECF must be equal (acid base regulation)
Describe buffers.
-maintain pH
-reversibly binds free H+ ions in solutions
-intracellular & extracellular buffer systems
-2 organs help maintain pH = lungs & kidneys
Describe acids VS base.
Acid = donates H
>H+
>made by metabolic processes
Base = accepts H
>HCO3-
>derived from nutrients
*protons are pos
Describe volatile VS nonvolatile acids.
Volatile:
-CO2 & H2O
-can breathe out
Nonvolatile:
-acids generated as byproducts of metabolism (kidneys)
Describe pH.
-measure of alkalinity & acidity
-proton conc [H+] in a solution & pH are inversely related
(High pH = low H+)
*pH equal to neg log of H+
*blood pH = 7.4
Describe the Henderson hasselbach equation.
-relationship between pH & mixture of an acid & its conjugate base
-evaluates pH by partial pressure of CO2 & bicarbonate HCO3
*increase HCO3 -> increase pH -> alkalosis
*increase PCO2 -> decrease pH -> acidosis
Describe strong VS weak acids & bases.
-strong acid = dissociates & releases H+ (ex. HCl)
-weak acid = releases H+ less easily (ex. H2CO3)
-strong base = reacts w H+ & removes H+ quickly (ex. OH)
-weak base = reacts slow w H+ (ex. HCO3)
*acids & bases in ECF are weak = H2CO3 & HCO3
Describe alkali.
-formed by combination of alkaline metals with a basic ion (OH)
-soluble base (soluble in water = contains alkaline metal)
Describe buffer solution.
-mixture of weak acid & conjugate base
-mixture of weak base & conjugate acid
-dissociation constant (pK) = pH at which half the buffer substance is dissociated & half is undissociated
Describe the pH differences in ECF & ICF.
-intracellular (ICF) pH is lower than plasma pH (ECF)
-cells under ischemia = more acidic pH
Describe the 3 systems that regulate H+ & HCO3- conc & pH in the body.
-buffer system (secs) = phosphate, proteins, bicarb
-lungs (mins) = CO2
-kidneys (hrs/days) = excrete/reabsorb H+ & HCO3-
Describe bicarbonate, phosphate, & protein buffer system.
- Bicarbonate (ECF)
-if the conc of H+/H2CO3 decreases = more H+ & HCO3 made & CO2 levels reduced
-decrease respiratory rate - Phosphate (ICF)
-NaHPO4, HPO4 - Proteins (ECF & ICF)
-accept protons like ex. Hemoglobin
Describe intracellular buffers.
-amino acids, proteins, phosphate
-membrane carriers:
>Na/H exchanger
>Cl/HCO3 exchanger
Describe respiration & acid base regulation.
-increased ventilation = increase CO2 elimination & decreased H+ conc (left shift, pH increases)
>hyperventilation = respiratory alkalosis
-changes in blood pH helps mitigate by increasing/decreasing rate of alveolar ventilation
>decrease in plasma pH = increase ventilation rate
*non volatile acids cant be excreted by lungs
Describe the kidneys.
-if H+ excretion > HCO3 excretion = acid loss from ECF
What are the 4 factors that control bicarbonate reabsorption?
- Luminal HCO3 conc
- Luminal flow rate
- Arterial pCO2
- Angiotensin II
Describe secretion & reabsorption.
- H+ secretion requires: (apical)
-Na/H anti porter
-H+ ATPase (proton pump) - HCO2 reabsorption requires: (basolateral)
-HCO3/Na cotransporter
-HCO3/Cl antiporter
*H+ excretion implies HCO3 reabsorption
Describe renal regulation of acids & bases.
- Acidosis = high H+ promote reabsorption of HCO3 & excess H+ excreted into urine
- Alkalosis = excess HCO3 not reabsorbed and excreted into urine
Describe intercalated cells functions.
- Acidosis (Type A) = IC cells secrete H+ & reabsorb HCO3
- Alkalosis (Type B) = IC cells reabsorb H+ & eliminate HCO3
What happens to the excess H+ in the tubular lumen?
-excretion of H+ via phosphate & ammonia
Describe the relationship between hypokalemia & acid base disturbances.
- Type B alkalosis (high pH)
-hypokalemia = decrease conc of K+ in ECF
>impaired neural transmission & muscle weakness - Type A acidosis (low pH)
-hyperkalemia = increase conc of K+ in ECF
>interfere w membrane potential -> cardiac toxicity
H+ elimination means K+ reabsorption & vice versa
Describe metabolic acidosis.
-gain in acid or loss of base
-decrease pH from acid accumulation that consume HCO3 or loss of HCO3
-compensatory = decrease PCO2 via hyperventilation
(Hyperkalemia)
Describe metabolic alkalosis.
-gain in base or loss of acid
-increased pH by loss of acid or increased HCO3
-compensatory = increased PCO2 via hypoventilation
(Hypokalemia)
Describe respiratory acidosis.
-decreased pH & increased PCO2
-compensatory = increase in HCO3 via kidneys
(Hypoventilation)
Describe respiratory alkalosis.
-increased pH & decreased PCO2
-compensatory = decrease in HCO3
(Hyperventilation)
Describe the 3 parameters needed for analyzing acid base status.
-pH of blood
-pCO2
-standard bicarb
Describe the anion gap (AG).
-eval acid base disorders
-characterize metabolic acidosis
>increased AG (normochloremic) metabolic acidosis
>normal AG (hyperchloremic) metabolic acidosis
-electroneutrality
>UA = unmeasured anions like organic acids
>UC = unmeasured cations like Ca & Mg
*either increase UA or Cl-
*AG increases if UA increase (>16) or UC decreases
Clinical cases diagram!
