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acid base
WVSOM -- Physiology -- Acid Base
Question | Answer |
---|---|
Once initial change is identified, what is determined next? | If the other parameter is abnormal to determined if it is mixed |
What does PTH do to the kidney? | makes them pee out more phosphate |
When does chronic respiratory acidosis begin? | after a few hours |
Whatn is chronic respiratory acidosis complete? | after a few days |
What happens during chronic respiratory acidosis? | kidneys increase excretion of itratable acids and there is an increased generation of bicarb |
What causes chronic respiratory acidosis? | COPD, CNS diseases that affect respiration, drugs that inhibit respiration and disease of respiratory muscles |
What buffers are used to compensate for acute respiratory acidosis? | serum proteins, hemoglobins and phosphates |
What happens in acute respiratory alkalosis? | H+ moves form cells and hemoglobin combines with HCO3, increased lactic acid production due to decrease in O delivery to tissues |
When is chronic respiratory alkalosis complete? | complete in a few days |
What causes respiratory alkalosis? | phsychogenic hyperventilation, altitude, improper use of mechanica ventilator, drugs (aspirin) fever |
What happens in chronic respiratory alkalosis? | kidneys reduce H excretion and HCO3 is lost in urine |
When is a decreased Pa Co2 normal? | pregnancy because of increased metabolic demand |
If there is a respiraotyr disorder what do you need to evaluate for? | is it acute or chronic and is there adequate compensation |
A patient has a pH of 7.29, pCO2 of 65, pO2 of 55mm Hg and an HCO3 of 32 mEq/liter. Does this patient have an acid base disorder? | Yes respiratory acidosis |
A patient has a pH of 7.29, pCO2 of 65, pO2 of 55mm Hg and an HCO3 of 32 mEq/liter. Is compensation taking place and is it appropriate? | yes because bicarb went up and CO2 went up and bicarb increases 3.5/10mmHg PCO and it is appropriate |
What causes metabolic acidosis? | acidemia due to accumulation of acids other than carbonic or loss of bicarbonate |
What happens to equilibrium of the carbonic equation if there is an accumulation of acids? | equilibrium shifts left |
What happens to the equilibrium of the carbonic equation if there is a loss of bicarb? | equilibrium will shift right |
What is the anion gap useful in discerning? | if metabolic acidosis si due to accumulation of acid or loss of bicarb |
What is an anion gap? | when acid is added to the body, H increases, but also has an accumulation of its conjugate (base) anion. The change in [anion] is the anion gap |
Anion gap = | [Na+] – [Cl-] + [HCO3-] |
What is the anion gap like with hypercholoremic metabolic acidosis? | increased Cl- |
What is normocholemic metabolic acidosis? | increase in unmeasured anions but normal Cl- |
What is normal range for anion gap? | 9-16 mEq/L |
What kind of metabolic acidosis has a normal anion gap/ | hyperchloremic metabolic acidosis |
What causes hyperchloremic metabolic acidosis? | diarrhea, renal tubular acidosis, drugs (glaucoma) and ammonium chloride ingestion |
How does the body compensate for hyperchloremic metabolic acidosis? | hyperventilation and the kidneys increase acid excretions (except with RTA |
What metabolic acidosis has a WIDE anion gap? | normochloremic metabolic acidosis |
What causes normochloremic metabolic acidosis? | (mudpiles) Methanol, uremia, diabetic ketoacidosis, paraldehyde, insulin (lack of) lactic acidosis, ethylene glycol and salicyclic acid |
How does the body compensate for normochloremic metabolic acidosis? | hyperventilation and kidneys increase acid excretions (except with kidney failure) |
What fluids have a pH of 7.35-7.45? | Plasma and interstitial fluid |
What fluids when loss could lead to alkalosis? | parietal gastric juice (ph < 1.0) and mixed gastric secretions (pH of 1-2) |
What fluid loss lead to acidosis? | Liver bile, pancreatic juice, jejuna fluid, and ileal fluid |
What are the two types of acids produced by physiological proceses? | volitile and fixed |
What is a volatile acid and why? | carbonic acid because it can be converted to CO2 |
Where are volatile acids handled? | lungs |
What are examples of Fixed acids? | lactic, acetoacetic, sulfuric |
Where are fixed acids handled? | kidneys |
What are the 5 processes that produce H+? | metabolism of carbs/fa/aa, anaerobic glycolysis, catabolism of phospholipids and nucleic acids |
What does anaerobic glycolysis produce? | lactic acid |
What does metabolism of FA produce? | urea and h2o secreted, co2 blown off, ketone bodies |
What does metabolism of carbs produce? | Urea/H20/CO2 |
What does metabolism of AA produce? | sulfuric acid, HCl, urea/H2O, CO2 blown off |
What does catabolism of phospholipids and nucleic acids produce? | phosphoric acid and uric acid |
What processes consume H=? | oxidation of lactic acid, lactic acid to glucose, oxidation of ketone bodies, catabolism of AA to NH4, metabolism of citrate |
What are foods with an acidifying effect? | proteins, cranberries, plums, prunes, tea and cocoa |
What foods have an alkalizing effet? | citrus, tomatoes and vegetables |
What kind of environment do vegetarians have? | alkalizing because they don’t eat much meat and eat alkalizing foods |
What do buffers do? | minimize changes in pH |
Do buffers prevent changes in pH? | NO |
What is most effective pKa? | if it is -1 to 1 of desired pH |
What limits physiologic buffers? | exceeding capacity, response of kidneys and lungs, and compromised function of respiratory/renal systems |
What are the 4 buffering systems of the body? | bicarb/CO2, inorganic/organic phosphates, proteins, bone |
What is the first buffering systems in extra cellular fluid? | bicarb/CO2 |
What is the first buffer in intracellurlar buffers? | inorganic/organic phosphates |
What does bone formation do to pH? | deposition of hydroxyapatite produces H+ |
What does bone resportion do to pH? | hydroxyapatite breakdown consumes H_ and carbonate released from bone can accept H+ |
What enzyme makes physiologic process of bicarb/CO2 buffer system possible? | carbonic anhydrase |
How do proteins act as buffers? | AA side chain components like histidine in hemoglobin |
What is the buffering system in plasma? | bicarb/CO2, protein, inorganic Phophates |
What is the buffering system in interstitial fluid? | bicarb/CO2 and inorganic phosphates |
What is the buffer system in intracellular fluid? | protien, organic phosphates, bicarb/CO2, phosphates |
What is the buffer system in RBC? | hemoglobin, organic phosphates, bicarb/CO2, inorganic phosphates |
What is the buffer system in bone? | hydroxyapatite and carbonate |
What is normal PaCO2? | 35-45 |
What is normal HCO3-? | 21-28 |
What is normal Na venous values? | 135-145 mEq/L |
What isnormal K venous value? | 3.5-5 mEq/L |
What is normal Cl- venous value? | 95-105 mEq/L |
pH = ? | -log[H+] |
What is hednerson-hasselbalch equation? | pH = pK + log[A-]/[HA} |
What is A- in H-H equation? | bicarbante |
What is HA in H-H equation? | PaCO2 to estimate H2CO3 |
What is normal body temp pK ? | 6.1 |
What is normal solubility of CO2? | 0.03 |
If bicarb is 24 and PaCO2 is 40 what is the pH? | pH = 6.1 + log[24/0.03(40)] = 7.4 |
How do you figure out carbonic acid in H-H equation? | PaCO2 times 0.03 |
What do the terms academia and alkalemia relate to? | abnormal pH of the blood |
What is a primary acid/base disorder? | it is respiratory or metabolic |
What is responsible for a respiratory acid/base disorder? | PaCO3 is responsible for abnormal pH |
What is responsible for a metabolic acid/base disorder? | HCO3- is responsible for abnormal pH |
What is a simple disorder? | only one primary acid/base disturbance |
What is a mixed(complex) acid/base disorder? Two or more primary disturbances in acid/base balance are present | |
Can a pH in normal range also have an acid/base disturbance? | yes, mixed alkalosis and acidosis |
What is compensation? | response to disturbance in acid/base balance in attempts to restor pH to normal |
When will the body over compensate? | NEVER |
Are body buffer systems a compensation mechanism? | NO because they help prevent academia or alkalemia |
What are the two compensatory mechanisms? | respiratory and renal |
What is respiratory compensation? | regulate rate of respiration to blow off/conserve CO2 |
What is renal compensation? | eliminate excess H+/HCO3-; regenerate HCO3; titratable acids/NH3:NH4 |
What is initial chemical change in respiratory acidosis? | increased pCO2 |
What is the compensatory response to respiratory acidosis? | increased HCO3 |
What is the initial chemical change in respiratory alkalosis? | decreased PCO2 |
What is the compensatory response to respiratory alkalosis? | decreased HCO3- |
What is the initial chemical change to metabolic acidosis? | decreased HCO3 |
What is the compensatory response to metabolic acidosis? | decreased PCO2 |
What is the initial chemical change in metabolic alkalosis? | increased HCO3 |
What is the compensatory response to metabolic alkalosis? | increased PCO2 |
What is assessed in arterial blood gas? | pH, PaCO3 and HCO3- |
How do pH and PaCO2 move in respiratory disorders? | opposite directions |
How do pH and HCO3- move in metabolic acid base disorders? | same direction |
A patient as a pH of 7.22, PaCO2 of 55 and HCO3- of 25. What does the patient suffer form? | respiratory acidosis |
A 44 y/o moderately dehydrated man admitted with 2 days of diarrhea. Na 134, K 2.9, Cl 108, pH 7.21, pCO2 43mmHg, HCO3 16. What is the man’s acid base disorder, what is the evidence for a mixed disorder and is compensation occurring and/or adequate? | metabolic acidosis. Not mixed. Anion gap is 10 (normal) so it is hypercholoremic metabolic acidosis |
22 y/o female with type I DM, presents with 1 day history of nausea, vomiting, polyuria, polydypsia and vague abdominal pain. Kussmaul resporations, dry mucous membranes. | Na 132, K 6.0, Cl 93, glucose 720. Urine has pH 5, + glucose. ABG shows pH of 7.27, HCO3 11, Pco2 23. What is acid/base disorder. What is compensation? |
What is delta ratio? | to determine if a mixed acid/base disorder is present |
Delta ratio = | Δ in anion gap/ Δ[HCO3-] |
When is delta ratio calculated? | when there is a metabolic acidosis with a high anion gap |
What is a delta ratio of 1-2 mean? | no confounding acid/base disorder |
If delta ratio < 1 what does that indicate? | simultaneous normal anion gap acidosis. Much greater fall in HCO3 compared to increase in anion gap |
If delta ratio is > 2 what does that indicate? | simultaneous metabolic alkalosis or compensatory chronic respiratory acidosis |
What is metabolic alkalosis associated with? | renal imparment of some kind. |
What results from accumulation of bicarb in plasma? | metabolic alkalosis |
What causes metabolic acidosis? | vomiting, nasogastric suction, posthypercapneic alkalosis, rapic infisu of bicarb, lactate or citrate and renal causes |
How do you compensate for metabolic alkalosis? | hypoventilation and kidneys attempt to excrete excess bicarb |
Patient has been sick for a week, vomiting several times every day. Dehydrated and fainted at work. pH 7.5, pCO2 43mmHg, PO2 95 mmHg, hemoglobin-O2 sat 97%, HCO3- 32 mEq/L. What is the acid base disorder? | metabolic alkalosis |
What is the expected compensation in metabolic acidosis? | PCO2 should be last 2 digits of pH |
What is expected level of compensation in metabolic alkalsois? | incresed PCO2=.7 X changeHCO3 |
What are the respiratory effects of acidosis? | hyperventilation, shift of oxyhemoglobin dissociation cure to the right and a decrease in 2,3DPG in RBG(after 6 hours of academia) |
What are the cardiovascular effects of acidosis? | depresion of contractility, sympathetic over-activity, resistance to the effects of catecholamines, peripheral arteriolar vasodilation, venocontriction of peripheral veins, vasoconstriction of pulmonary arteries |
What are the effects of CNS with acidosis? | cerebral vasodilation which leads to an increase in cerebral blood flow and intracranial pressure. Very high pCO2 levels will cause central depression |
What happens to bone in acidosis? | increased bone resoprtion |
What happens to K+ in acidosis? | K+ leaks out of cells causing Hyperkalemia |
What happens to phosphate in acidosis? | increase in extracellular phosphate concentration |
What are the respiratory effects of alkalosis? | sift of oxyhemoglobin dissociation cure to the left, increase in 2,3 DPG levels in RBC. Inhibition of respiratory drive via the central and peripheral chemoreceptors |
What are the effects on the cardiovascular with alkalosis? | depression of myocardial contractility and arrhythmias |
What is the effect of alkalosis on the CNS? | cerebral vasoconstriction leads to decreased blood flow and altered LOC. |
What happens to H+ ions with alkalosis? | shifts into cells leading to hypokalemia |
What is the role of K+ in acid/base balance? | is moved into and out of cells to compensate for changes in H+ |
What is the H+/K+ in alkalosis? | H+ moves out of the cell and K+ moves into the cells (Hypokalemia) |
What is the H+/K+ in acidosis? | H+ moves into cells and K+ moves out resulting in hyper kalemia |
What happens with Ca++ in alkalosis? | thre are more anionic proteins so Ca bind sto it resulting in hypocalcemia |
What happens with Ca++ in acidosis? | there are less anionic proteins so there is less Ca binding and hypercalcemia results |