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Patho Acid Base
Reasoning through acid base imbalances -- from Copstead, Banasik Pathophysiology
| Question | Answer |
|---|---|
| normal pH for adults | 7.35 - 7.45 |
| acidosis | high values - low pH |
| alkalosis | low values - high pH |
| compensation | normalizing pH; makes other values abnormal. opposite system, same direction |
| correction | normalizing pH; fixes the problem. same system as problem, same direction |
| blood gases | blood parameters: pH, PO2, PaCO2, bicarbonate |
| Where is carbonic acid produced in the body? Where is it excreted? | Produced in cells; excreted through lungs |
| Where are metabolic acids produced in the body? Where are they excreted? | Produced in cells; excreted by kidneys |
| why is too much acid in the body a problem? | cell enzymes work best at a certain pH |
| bicarbonate: carbonic acid (normal pH) | 20:1 |
| PaCO2 | partial pressure of carbon dioxide |
| HCO3- | bicarbonate |
| H+ | hydrogen ion: concentration of it determines pH |
| CO2 | carbon dioxide |
| H2CO3 | carbonic acid |
| Buffers – types | bicarbonate; phosphate;hemoglobin; protein |
| Buffers – function | prevent large changes in pH |
| If a fluid has too much H+, how does the buffer system return pH to normal? How does the buffer system restore its normal proportions? | base portion takes on H+ and becomes an acid; excretes excess acid |
| If a fluid has too little H+, how does the buffer system return pH to normal? How does the buffer system restore its normal proportions? | acid portion releases an H+ and becomes a base; retains more acid |
| Bicarbonate buffer | HCO3- (base) / H2CO3 (weak acid); found in ECF -- vascular and interstitial |
| Phosphate buffer | intracellular and renal tubular fluid and urine |
| Hemoglobin | buffer inside RBCs |
| Protein buffer | intracellular and vascular |
| What acid is excreted through respiration? Relationship betw change in respiration and excretion of acid? | carbonic acid as CO2 and H2O; rate and depth increases to excrete, decreases to retain |
| What is the role of chemoreceptors in excretion of carbonic acid? | change rate and depth of resp with change in PaCO2, pH |
| What is the difference between correction and compensation with regard to acid-base imbalances? | correction returns all blood values to normal; compensation returns pH to normal but causes imbalances in other blood values |
| In what situation is hyperventilation a compensatory response? In what situation is it a corrective response? | compensatory: metabolic acidosis; corrective: respiratory acidosis |
| What type of acid do the kidneys excrete? Which acid are they unable to excrete? | metabolic acids; not carbonic acid |
| How does renal excretion of acid increase the blood bicarbonate ion concentration? | As H+ is excreted into renal tubular fluid, bicarbonate is obliged to travel opposingly into blood |
| How does renal tubular cell production of ammonia assist the excretion of hydrogen ions? | ammonia (NH3-) combines with H+ to make NH4, which can't go back through to blood and must be excreted |
| How do the kidneys compensate for an excess of carbonic acid? | excrete more metabolic acids, so net pH returns to normal |
| How do the kidneys respond to increased blood pH? | Secrete less H+ and ammonia into renal tubules; make urine more alkaline |
| How would the kidneys respond to a large excess of thyroid hormones (untreated hyperthyroidism)? | Secrete more H+ and ammonia into renal tubules; make urine more acidic |
| How do the kidneys respond to prolonged increase of carbonic acid in the blood? | Secrete more H+ and ammonia into renal tubules; make urine more acidic |
| What is the difference between acidosis and acidemia? Between alkalosis and alkalemia? | acid and alkalosis is presence of factors that tend to lower/raise blood pH; -emia refers to the lowered/raised state of pH of the blood |
| What is metabolic acidosis, and what two general mechanisms cause it? | condition tending toward too much acid in blood, due to acids normally excreted by kidneys. increase of metabolic acid, decrease of base |
| Why is decreased PaCO2 a sign of metabolic acidosis? | Compensatory mechanism in metabolic acidosis |
| Why are confusion, lethargy, stupor symptoms of metabolic acidosis? | decreased intracellular pH in neurons |
| Why are cardiac dysrhythmias symptoms of metabolic acidosis? | decreased intracellular pH in myocardial cells |
| Why is decreased blood bicarbonate a sign of metabolic acidosis? | buffering excess acid |
| Why is low blood pH a sign of metabolic acidosis? | relative increase of metabloic acids in blood |
| Why is abdominal pain a possible symptom of metabolic acidosis? | not well understood |
| What is respiratory acidosis, and what three general mechanisms cause it? | Impaired gas exchange, impaired neuromuscular function (chest wall), impaired respiratory control (brainstem) |
| What conditions may cause impaired gas exchange? | COPD, pneumonia, severe asthma, pulmonary edema, acute (adult) respiratory distress syndrome, obstructive sleep apnea |
| What conditions may cause impaired neuromuscular function? | Guillain- Barre syndrome, Chest injury or surgery (pain), hypokalemic respiratory muscle weakness, kyphoscoliosis, respiratory muscle fatigue |
| What conditions may cause impaired respiratory control? | Respiratory depressant drugs (opiates, barbiturates), central sleep apnea |
| Why is low blood pH a sign of respiratory acidosis? | increased carbonic acid in blood |
| Why is increased blood bicarbonate a sign of respiratory acidosis? | compensatory response by kidneys |
| Why is headache a symptom of respiratory acidosis? | cerebral vasodilation |
| Why are tachycardia and cardiac dysrhythmias symptoms of respiratory acidosis? | decreased intracellular pH in myocardial cells |
| Why are disorientation and lethargy symptoms of respiratory acidosis? | decreased intracellular pH in neurons |
| What is metabolic alkalosis, and what two general mechanisms cause it? | condition that tends to cause relative deficit of metabolic acids (any other than carbonic acid). Caused by increase of base, or decrease of metabolic acid |
| Why is increased blood bicarbonate a sign of metabolic alkalosis? | increased intake or unused buffers |
| Why are slow, shallow respirations a sign of metabolic alkalosis? | compensatory response by lungs |
| Why are paresthesias, muscle twitching and cramping symptoms of metabolic alkalosis? | increased neuromuscular excitability |
| Why is high blood pH a sign of metabolic alkalosis? | relative deficit of metabolic acids |
| How is hypokalemia related to metabolic alkalosis? | cause metabolic alkalosis or be caused by it |
| Why are beligerence or confusion, lethargy, seizures, coma symptoms of metabolic alkalosis? | neuron dysfunction from increased intracellular pH and increased neural excitability |
| What is respiratory alkalosis, and what general mechanism causes it? | condition tending to cause deficit of carbonic acid in blood; hyperventilation |
| What conditions may cause hyperventilation? | hypoxemia, pain, anxiety/distress, prolonged sobbing, alcohol withdrawal, stimulation of brainstem |
| How might the brainstem become stimulated and result in hyperventilation? | salicylate overdose, meningitis, head injury, gram-neg sepsis |
| Why is high blood pH a sign of respiratory alkalosis? | Decreased carbonic acid in blood |
| Why is decreased blood bicarbonate a sign of respiratory alkalosis? | Compensation by kidneys |
| Why are rapid, deep respirations a sign of respiratory alkalosis? | This is hyperventilation, the cause of respiratory alkalosis |
| Why are paresthesias, muscle twitching, and cramping symptoms of respiratory alkalosis? | Less ionized calcium available (dec cell activity) leads to increased neuromuscular excitability |
| Why is confusion a symptom of respiratory alkalosis? | increased intracellular pH in neurons and decreased cerebral blood flow |
| What are mixed acid-base imbalances? How do they affect pH of the blood? | More than one primary imbalance in the same person. If both acidosis or both alkalosis, pH increased or decreased more significantly. If there is a mix of acidosis and alkalosis, pH near normal depending on severity of each. |
| What acid-base imbalance can result from hypoxemia? Why? | respiratory alkalosis; causes rapid, deep breathing (hyperventilation) |
| What acid-base imbalance can result from pain? Why? | respiratory alkalosis; can cause increase in rate and depth of breathing |
| What acid-base imbalance can result from anxiety or psych distress? Why? | respiratory alkalosis; causes increase in rate and depth of breathing |
| What acid-base imbalance can result from prolonged sobbing? Why? | respiratory alkalosis; gasping in between sobs causes deep, fast breathing |
| What acid-base imbalance can result from alcohol withdrawal? Why? | respiratory alkalosis; absence of depressant effect leaves resp center sensitive to CO2, causing hyperventilation |
| What acid-base imbalance can result from stimulation of the brainstem? Why? | respiratory alkalosis; stimulation of respiratory center results in increase of rate and depth of breathing |
| What acid-base imbalance can result from COPD? Why? | respiratory acidosis; Impaired gas exchange |
| What acid-base imbalance can result from Pneumonia? Why? | respiratory acidosis; esp bacterial; exudate builds up in alveoli, leading to Impaired gas exchange |
| What acid-base imbalance can result from severe asthma? Why? | respiratory acidosis; constriction of bronchioles causes difficulty breathing: Impaired gas exchange |
| What acid-base imbalance can result from pulmonary edema? Why? | respiratory acidosis; fluid in alveoli? Causes impaired gas exchange |
| What acid-base imbalance can result from acute respiratory distress syndrome? Why? | respiratory acidosis; Impaired gas exchange |
| What acid-base imbalance can result from obstructive sleep apnea? Why? | respiratory acidosis; Impaired gas exchange |
| What acid-base imbalance can result from guillain-Barre syndrome? Why? | respiratory acidosis; impaired neuromuscular function |
| What acid-base imbalance can result from chest injury or surgery? Why? | respiratory acidosis; impaired neuromuscular function |
| What acid-base imbalance can result from hypokalemia? Why? | respiratory acidosis; impaired neuromuscular function due to respiratory muscle weakness |
| What acid-base imbalance can result from kyphoscoliosis? Why? | respiratory acidosis; impaired neuromuscular function |
| What acid-base imbalance can result from respiratory muscle fatigue? Why? | respiratory acidosis; impaired neuromuscular function |
| What acid-base imbalance can result from opiates or barbiturates? Why? | respiratory acidosis; impaired respiratory control caused by respiratory depressant drugs |
| What acid-base imbalance can result from central sleep apnea? Why? | respiratory acidosis; impaired respiratory control |
| What acid-base imbalance can result from ketoacidosis? Why? | metabolic acidosis; increase in acid due to rapid production of unusual acids that overwhelm renal excretory capability; from diabetes m., starvation, alcoholism |
| What acid-base imbalance can result from severe hyperthyroidism? Why? | metabolic acidosis; increase in acid due to increased cellular metabolism |
| What acid-base imbalance can result from severe infection? Why? | metabolic acidosis; increase in acid due to increased cellular metabolism |
| What acid-base imbalance can result from burns? Why? | metabolic acidosis; increase in acid due to increased cellular metabolism |
| What acid-base imbalance can result from circulatory shock? Why? | metabolic acidosis; increase in acid due to decreased renal acid excretion |
| What acid-base imbalance can result from tissue anoxia? Why? | metabolic acidosis; increase in acid due to rapid production of lactic acidosis, overwhelms excretory capability |
| What acid-base imbalance can result from oliguric renal failure? Why? | metabolic acidosis; increase in acid due to decreased renal excretion |
| What acid-base imbalance can result from intake of acids, precursors? Why? | metabolic acidosis; increase in acid; precursors include salicylates, methanol, boric acid, ethylene glycol |
| What acid-base imbalance can result from diarrhea? Why? | metabolic acidosis; increased excretion of bicarb (normal route) |
| What acid-base imbalance can result from gastrointestinal fistula that drains intestinal or pancreatic secretions? Why? | metabolic acidosis; loss of bicarb (abnormal route) |
| What acid-base imbalance can result from intestinal decompression (suction)? Why? | metabolic acidosis; loss of bicarb (abnormal route) |
| What acid-base imbalance can result from renal tubular acidosis? Why? | metabolic acidosis; increased excretion of bicarb (normal route) |
| What acid-base imbalance can result from profound ECF volume deficit? Why? | metabolic acidosis; inability to excrete acids |
| What acid-base imbalance can result from intake of bicarb or precursors? Why? | metabolic alkalosis; increase in base due to intake; body turns acetate, citrate, lactate into bicarb |
| What acid-base imbalance can result from massive transfusion of citrated blood? Why? | metabolic alkalosis; increase in citrate which body turns to bicarb |
| What acid-base imbalance can result from mild/moderate ECF volume deficit? Why? | metabolic alkalosis (contraction alkalosis); increase in base due to increased renal reabsorption of bicarbonate. Also decrease in acid because of increased excretion |
| What acid-base imbalance can result from emesis? Why? | metabolic alkalosis; decrease in acid due to loss (abnormal route) |
| What acid-base imbalance can result from gastric suction? Why? | metabolic alkalosis; decrease in acid due to loss (abnormal route) |
| What acid-base imbalance can result from hyperaldosteronism? Why? | metabolic alkalosis; decrease in acid due to increased renal excretion of metabolic acids |
| What acid-base imbalance can result from hypokalemia? Why? | metabolic alkalosis; decrease in acid due to potassium ion shift into cells |
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hezasan
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