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21 Cards in this Set
- Front
- Back
What are acid/base disorders?
What's the normal [H] concentration of the ECF? |
*Acid base disorders are disorders of the concentration of hydrogen ion (H) in the extracellular fluid.
*In the extracellular fluid, the normal H concentration is 40 nEq/L. |
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If the H concentration is 40 nEq/L, what is the pH?
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7.4. This is normal blood pH.
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What are the [H] ranges for acidemia and alkalemia, in both nEq/L and in pH?
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*Keep in mind that [H] falls as pH rises.
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How abundant is H compared to other cations?
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*It's not. [Na] is thousands of times more abundant.
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What happens As H+ rises and pH falls?
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*Myocardial contractility decreases.
*Vascular responsiveness to catecholamines decrease (hypotension due to decreased arteriolar function). *Renal and hepatic plasma flow decrease. *Skeletal muscle contractility decreases. *Protein degradation increases, protein synthesis decreases. *K+ leaves the intracellular space and hyperkalemia increases in the extracellular fluid. *Calcium dissociates from albumin, increasing the level of ionized (bioactive) calcium in the extracellular fluid. |
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What happens As H+ falls and pH rises?
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*Increased vasoconstriction.
*Increased muscular contraction. *K+ enters the intracellular space and hypokalemia develops in the extracellular fluid. *Calcium binds to albumin, decreasing the level of ionized (bioactive) calcium in the extracellular fluid. *Decreased oxygen release by erythrocytes, decreasing tissue oxygenation.* |
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At what pH and [H] is life possible?
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*Outside of 7.3 and 7.5, life is only possible for a few hours.
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What two processes constantly increase the H+ concentration?
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What happens to H2CO3 when it is added to the body?
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It is converted to CO2 and water: CO2 diffuses from alveolar capillaries to alveolar space in the lung and is expired.
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What happens to dietary acids when we take them in?
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An acid added to the ECF is buffered by HCO3, producing H2CO3 and a molecule of the salt of the added acid, consuming a H2CO3 molecule in the process.
HA + NaHCO3 --> NaA + H2CO3 H2SO4 + NaHCO3 --> NaHSO4 + H2CO3 H3PO4 + NaHCO3 --> NaH2PO4 + H2CO3 *H2CO3 then --> CO2 + H2O and is expired. |
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How do the concentrations of H2CO3 and CO2 affect [H]?
How does HCO3 level affect the [H]? |
*Note normal PCO2 level.
*Note normal bicarb level. *H2CO3=CO2 |
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What is the HH equation for the human body?
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What's more important for us to know than the HH equation for understanding the level of acidity of the blood?
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*States that pH and H+ are dependent on pCO2 and HCO3. Normal body values are listed in the image.
*Note the measurement units of all the values in this equation. Note that the constant is a value of 24. |
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So...what are the 4 ways that your pH can become ABNORMAL?
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*Increase in H+ (ACIDEMIA):
1) Increase in pCO2 2) Decrease in HCO3- *Decrease in H +(ALKALEMIA): 3) Decrease in pCO2 4) Increase in HCO3- |
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WHAT DO THESE 4 CHANGES LEAD TO?
*Increase in H+ (ACIDEMIA): 1) Increase in pCO2 2) Decrease in HCO3- *Decrease in H +(ALKALEMIA): 3) Decrease in pCO2 4) Increase in HCO3- |
*Increase in H+ (ACIDEMIA):
1) Increase in pCO2: RESPIRATORY ACIDOSIS 2) Decrease in HCO3: METABOLIC ACIDOSIS *Decrease in H +(ALKALEMIA): 3) Decrease in pCO2: RESPIRATORY ALKALOSIS 4) Increase in HCO3: METABOLIC ALKALOSIS |
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You are in the emergency room and an unidentified man, who appears to be in his twenties, is brought to the critical care area after passing out at a bar. An arterial pH is done and is 7.28. The pO2 is 97 mmHg and the pCO2 is 36 mmHg. The HCO3- level is 31 mEq/L. What is the acid base disturbance?
a) metabolic acidosis b) metabolic alkalosis c) respiratory acidosis d) respiratory alkalosis e) a mixed acidosis and alkalosis f) the lab values must be incorrect. |
*The lab values must be incorrect.
*THE POINT: this is an impossible combination of lab numbers. |
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What 3 organ systems determine the body's pH?
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*The normal, or physiologic [H] in the extracellular fluid is 40 nEq/L; this correlates to a pH of 7.40. The [H] is determined (as per the Henderson equation) by the [HCO3] and the partial pressure of CO2 (pCO2).
*The [HCO3] is regulated to be closely around a value of 24 mEq/L, the pCO2 is closely regulated around a value of 40 mmHg. *The lungs are responsible for the pCO2 level and the gastrointestinal and renal systems determine the HCO3 level. Therefore, three organ systems: pulmonary, GI, and renal, regulate and determine the [H] and pH of the ECF. |
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How is pH maintained in the upper GI tract?
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*As parietal cells secrete HCl into the lumen of the upper GI tract, NaHCO3 is simultaneously transported into the capillaries that line the stomach. Therefore, neutrality is maintained.
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How is pH maintained in the lower GI tract?
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*In the jejunum, ileum, and proximal large intestine, the reverse process occurs: NaHCO3- is secreted into the intestinal lumen, and HCl- diffuses into the surrounding capillaries. Neutrality is maintained.
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What happens to bicarb in the proximal tubule?
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*It's freely filtered by the glomerulus (negative charge, small size).
*One molecule of bicarb combines with one molecule of secreted [H]; H2CO3 is formed. *It dissociates, and CO2 and H20 diffuse freely into the cell. H2CO3 is formed again. This H2CO3 dissociates into HCO3- and H+. *The H+ gets secreted into the TF, and the bicarb is reabsorbed. |
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What happens to bicarb in the distal tubule and the proximal CCD?
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*Restores our pH by secreting acid that was taken in in the diet, regenerating the bicarb that gets used up.
*Occurs in INTERCALATED cells. *Distal tubular cell: 1) Secretion of H+ into the tubular lumen (as free H+, as titratable acid, or as ammonium (NH4+). 2) In this process, there is regeneration of HCO3- and passage of HCO3- into the systemic circulation. 3) Both of the above processes stimulated by aldosterone. |