Exam 4 - Electrolytes 3 Flashcards
Hypoventilation
increases blood CO2 levels (person will become acidotic)
Hyperventilation
decreases blood CO2 levels (person will become alkalotic)
Increase CO2 and decreased pH
stimulate pulmonary ventilation
Increase pH
inhibits pulmonary ventilation
Renal control of pH
- most powerful “buffer” system (but slow response)
- allows for reabsorption of HCO3- into ECF
- renal tubules secrete H+ into tubular fluid then excrete it in urine
H+ secretion
- rate of H+ secretion INCREASES as body fluid pH DECREASES (as H+ increases) or as ALDOSTERONE LEVELS INCREASE
- secretion of H+ inhibited when urine pH falls below 4.5
Tubular secretion of H+ continues only w/…?
only w/ a concentration gradient of H+ between tubule cells and tubular fluid
- if H+ concentration increases in tubular fluid (lowering pH to 4.5), secretion of H+ stops
Buffers in tubular fluid
- bicarbonate system
- phosphate system
- ammonia
Acidosis
H+ diffuses into cells and drives K+ out, elevating K+ concentration in ECF(hyperkalemia)
Effect of acidosis
H+ buffered by protein in ICF thus causing membrane HYPERPOLARIZATION
- nerve and muscle cells are hard to stimulate (CNS depression may lead to death)
Alkalosis
H+ diffuses out of cells and K+ diffuses in
Effect of alkalosis
- membranes become DEPOLARIZED
- nerves overstimulate muscles causing spasms, tetany, convulsions, respiratory paralysis
Respiratory acidosis and example
rate of alveolar ventilation balls behind CO2 production
EX: emphysema
Respiratory alkalosis and example
CO2 eliminated faster than it is produced
EX: hyperventilation
Metabolic acidosis
- increased production of organic acids (lactic acid, ketones)
- ingestion of acidic drugs (aspirin)
- loss of base (chronic diarrhea, laxative overuse)
Metabolic alkalosis
- overuse of bicarbonates (antacids)
- loss of acid (chronic vomiting)
Process of diagnosing an acid-base imbalance
- Note whether the pH is high or low relative to the normal range (this tells you whether you have acidosis or alkalosis)
- Decide which value of pCO2 or HCO3- could cause the abnormality (this tells you whether you have a respiratory or metabolic problem)
- Look at the NON-CAUSATIVE VALUE and determine if it is appropriately compensating for the problem (this tells you whether r not you have more than one problem going on)
Normal pH value
7.40
Anything below 7.40
acidosis
Anything above 7.40
alkalosis
Normal pCO2 value
40
pCO2 above 40
- tends toward acidosis
- causes low pH
- neutralizes high pH
pCO2 below 40
- tends toward alkalosis
- causes high pH
- neutralizes low pH
Normal HCO3- (bicarbonate) level
24
High pH, high pCO2
metabolic alkalosis
High pH, low pCO2
respiratory alkalosis
Low pH, high pCO2
respiratory acidosis (HCO3- will be high because it’s moving in the right direction to try to compensate for the acidosis)
Low pH, low pCO2, low HCO3-
metabolic acidosis (decreased HCO3- leads to acidosis)
Metabolic causes are in the same direction as…
pH
increase pH, increase bicarb
decrease pH, decrease bicarb
Compensation
when both pCO2 and HCO3- rise or fall together to maintain NEARLY NORMAL pH (between 7.35 and 7.45)
Partial (inadequate) compensation
occurs when pCO2 and HCO3- levels rise or fall together but the pH REMAINS PRETTY ABNORMAL
What does partial (inadequate) compensation tell you?
- tells you that you have more than one problem on your hands
EX:
pH = 7.44
pCO2 = 30
HCO3- = 18
- alkalosis
- respiratory
- complete compensation
Anion Gap =
Na - (Cl + HCO3-)
non-anion gap acidosis
< or = 12
positive anion gap acidosis
> 12
MULEPAK (possibilities that lead to a positive anion gap acidosis)
- Methanol
- Uremia
- Lactic acid
- Ethylene glycol
- Paraldehyde
- Aspirin
- Ketoacidosis
