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Acid-Base Disorders I
Terms in this set (62)
Actual change in arterial pH
Pathologic processes that cause changes in arterial pH
acidosis/alkalosis (can happen simultaneously)
Initiated by changes in PaCO2
How long does it take for kidney function to change in respiratory disorders?
Initiated by changes in arterial HCO3- concentration
How long does it take for changes in ventilation and PaCO2 to happen in metabolic disorders?
In simple disorders, PaCO2 and arterial HCO3- always...
change in the same direction
If PaCO2 and HCO3- move in opposite directions, you can...
rule out simple disorders (is a mixed disorder)
Total CO2 equation
Total CO2 = venous HCO3- + (dissolved PCO2 x .03)
Always given in acid-base problems
arterial blood gasses
Cause of increase in PaCO2 in respiratory acidosis
decreased alveolar ventilation
Body's response to fix acute respiratory acidosis/alkalosis
Change in arterial HCO3- in response to acute respiratory acidosis
increase by 1 mEq per every 10 mmHg PaCO2 increase
Mech of body's response to fix acute respiratory acidosis
high PaCO2 => goes into RBC => CA converts CO2 into H+ & HCO3- => Hb binds H+ => HCO3- builds up => leaves RBC & enters plasma
Body's response to fix chronic respiratory acidosis/alkalosis
Change in arterial HCO3- in response to chronic respiratory acidosis
increases by 3.5 mEq for every 10 mmHg PaCO2 increase
What kinds of patients would have a difficult time responding to chronic respiratory acidosis?
those with acute or chronic kidney failure (can't excrete fixed acid)
Severe pulmonary disease causes...
CNS depression, chest wall issues, and neuromuscular problems all cause
Unique causes of respiratory acidosis (3 categories)
cNS depression, chest wall issues, neuromuscular problems
Clinical manifestation of acute hypercapnia
Clinical manifestation of chronic hypercapnia
Severe hypercapnia causes ... (2)
Acute exacerbation of this pulmonary disease can cause hypercapnic coma
chronic obstructive bronchitis
Acute exacerbation of chronic obstructive bronchitis can cause ...
Patient has warm, flushed skin and mild systolic HTN...dx?
cardiovascular manifestations of respiratory acidosis
Respiratory acidosis has high or low systemic vascular resistance?
low (CO2 is a vasodilator...causes the flushed skin)
Respiratory acidosis has high or low systolic BP?
high (mild systolic HTN from increased CO...causes bounding pulses)
How to tell sepsis from respiratory acidosis?
respiratory acidosis has mild systolic HTN
Most common acid-base disorder
Cause of respiratory alkalosis?
increased alveolar ventilation
Two kinds of people w/o disease that could develop respiratory alkalosis?
pregnant women, people at high altitude
Most common acid-base disorder in critical care units?
Poor prognosis in respiratory alkalosis if PaCO2 is below...
Caused by an acute decrease in PaCO2
acute respiratory alkalosis
Change in arterial HCO3- in response to acute respiratory alkalosis
decrease by 2 mEq for every 10 mmHg decrease in PaCO2
Mech of body's response to acute respiratory alkalosis
low PaCO2 => low CO2 inside RBC => pH increases => Hb releases the H+ it was holding onto => HCO3- gets turned into CO2 & disappears => [HCO3-] inside RBC drops => HCO3- moves down gradient from plasma to inside RBC
Only acid-base disorder where pH can be returned back to normal by the body's adaptations
chronic respiratory alkalosis
Caused by a sustained decreased in PaCO2
chronic respiratory alkalosis
Change in arterial HCO3- in response to chronic respiratory alkalosis
decreases by 5 mEq for every 10 mmHg decrease in PaCO2
Urine profile of patient w/ chronic respiratory alkalosis
>20 mEq/L of HCO3- in urine (aka high urine bicarb)
Causes of respiratory alkalosis are mainly...
CNS driven (anxiety, hepatic failure, CNS lesions, high altitude/hypoxemia, sepsis, aspirin toxicity, pregnancy, hyperthyroidism)
Tetany, paresthesias, carpopedal spasm
clinical manifestations of respiratory alkalosis (low ionized Ca2+)
Levels of ionized Ca2+ in respiratory alkalosis?
Causes of the signs and symptoms in respiratory alkalosis?
low ionized Ca2+
Mechanism for low ionized Ca2+ in respiratory alkalosis?
albumin releases H+ => albumin becomes more negative => attracts & binds more cations
Cerebral blood flow in respiratory alkalosis?
decreased (remember CO2 is a vasodilator and now you have less of it...causes lightheadedness and confusion)
Glycolysis stimulated or inhibited in respiratory alkalosis?
Plasma [phosphate] high or low in respiratory alkalosis?
low. Alkalemia stimulates glycolysis, which uses up phosphate
Reduction in arterial HCO3- and accumulation of fixed acid cause...
3 ways fixed acid can accumulate in metabolic acidosis?
overproduction, underexcretion (renal), loss of HCO3- (renal or intestinal)
Initial change in metabolic acidosis?
decrease in ECH HCO3-
Change in PaCO2 in response to metabolic acidosis?
decreases by 12 mmHg for every 10 mEq/L decrease in HCO3-
2 conditions where HCO3- blood levels can be low
metabolic acidosis, chronic respiratory alkalosis
When the last two digits of the pH equal the value of PaCO2 you know the dx is...
Most characteristic clinical finding of metabolic acidosis
Kussmaul respiration (hyperventilation)
Kussmaul respiration/hyperventilation associated with...
Sympathetic hyper- or hypo-active in metabolic acidosis?
SNS hyperactivity in metabolic acidosis causes venoconstriction which...
raises ventricular EDV
Hypercalcuria & kidney stones assoc w/ ...
How does metabolic acidosis cause heart problems?
too much H+ competes w/ Ca2+ for binding sites on contractile proteins
Abnormalities in myocardial Ca2+ cycling assoc w/...
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