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Nephrology 2 > Nephrology Acid Base > Flashcards

Nephrology Acid Base Flashcards

1
Q

Acid Base balance is maintained what 3 major mechanisms?

A

Respiratory: CO2 is exhaled

Metabolism: Metabolic utilization of organic acids

Renal: excretion of non-volatile acids

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2
Q

Respiratory Buffer:

  • explain how this works
  • compensation time
  • amount of compensation in metabolic acidosis? Alkalosis?
A

How: pH will trigger an increase or decrease in the rate and depth of ventilation until appropriate amount of CO2 has been re-established.

-compensation occurs within minutes

Compensation Metabolic acidosis: PCO2 will decrease by 1.3mmHg for every 1mEq/L drop in serum HCO3

Compensation Metabolic Alkalosis: PCO2 will increase 0.7mmHg for every 1mEq/L inrease in HCO3

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3
Q

What system maintains the balance of HCO3 and H+?

A

Renal system

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4
Q

Kidneys affect changes in the pH, how long does it take to see these effects?

A

3-5 days, after just 6-12hrs the kidneys kick in

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5
Q

Bicarbonate Buffer:

-amount of compensation in acute/chronic respiratory acidosis/alkalosis?

A

Acute respiratory acidosis HCO3 will increase for every increase in PCO2, Chronic respiratory acidosis HCO3 will need to increase a greater amount than usual(acute) to compensate for the increased CO2 (b/c its chronically elevated)

vice versa for resp alkalosis

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6
Q

Respiratory Acidosis

  • whats the main problem?
  • how do you correct that?
  • causes
A

Problem: increased CO2 retention, hypoventillation

Correction: hyperventillation/ventillation

Causes:

  • CNS depression; meds, head injury
  • Impaired resp. function; spinal cord injury, neuromuscular dz
  • pulmonary disorders: atelectasis, PNA, pulm edema, massive PE
  • hypoventilation d/t pain, chest wall injury, abd distension, obesity, trauma l
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7
Q

Respiratory Alkalosis

  • whats the main problem?
  • how do you correct this?
  • causes
A

Problem: hyperventillation, not enough CO2

Correct: slow the resp rate, correct the underlying cause

Causes:

  • anxiety, pain, fear
  • fever, sepsis, pregnancy, thyrotoxicosis
  • meds; resp stimulants
  • CNS lesion
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8
Q

Metabolic acidosis

  • whats the problem?
  • causes
A

Problem: not enough HCO3 to buffer the acid

  • HCO3 can be lost via GI or renal
  • too much acid can build up via excretion problem(renal dz), overdose, metabolism issues

Causes: Absolutely need to know these

  • renal failure
  • DKA
  • diarrhea
  • anaerobic metabolism (from tissue hypoxia)
  • starvation
  • salicylate intoxication
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9
Q

The presence of metabolic acidosis should spur a search for what?

A

hypoxic tissue somewhere in the body!!!!

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10
Q

Anion Gap:

  • What is this?
  • what is this used for?
  • what is normal range?
  • what may alter this?
  • formula
A

WHat: the difference between primary measured cations Na and K and the primary measured anions Cl and HCO3 in the serum.

-used in Metabolic Acidosis to narrow down the etiology (of metabolic acidosis)

Normal range is 12 +/- 4

Anion gap may be thrown off by non-measured ions, Na, Cl, and HCO3 compensate for the unmeasured ions.

AG= Na - (HCO3+Cl)

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11
Q

What non acid base disorders may cause errors in Anion gap interpretation?

A
  • hyper/hyponatremia
  • low albumin
  • certain abx
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12
Q

Why should anion gap always be calculated?

A
  • it is possible to have an abnormal AG even if the Na, Cl, and HCO3 levels are normal.
  • A large AG (greater than 20) suggest a primary metabolic acid-base disturbance regardless of pH or serum HCO3 levels.
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13
Q

If you have an increased AG metabolic acidosis what do you need to calculate?

A

HCO3, this is the predicted HCO3 value that you compare the pts HCO3 value to. If the pt has a HCO3 higher or lower than predicted it indicates concomitant presence of metabolic alkalosis or normal AG metabolic acidosis.

??? if this doesnt make sense wait for the winters and summers cards…

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14
Q

What are the causes onf INCREASED anion gap metabolic acidosis

A

MUDPILES

Methanol intoxication

Uremia

diabetic or alcoholic ketoacidosis

Paraldehyde

isoniazide or iron overdose

lactic acid

ethylene glycol intoxication

Salicylate overdose

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15
Q

Causes of Non-anion gap metabolic acidosis

A

USED CAR

Ureteral-sigmoid diversions (accumulate urine in intestine)

Small bowel fistula

Endocrinopathies

Diarrhea

Carbonic anhydrase inhibitors

A: hyperAlimentation (TPA)

Renal tubular acidosis

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16
Q

Metabolic Alkalosis

  • whats the problem?
  • causes
A

Problem: too much HCO3, can occur with excessive H+ loss(GI/renal) or just gain in HCO3.

Causes;

  • excess base or loss of acid
  • -excess base: antaicds, use of lactate in dialysis, excess use of bicarb
  • -loss of acids: protracted vomititng, gastric suction, hypochloremia, excess admin of diuretics, high aldosterone levels
17
Q

Symptoms of alkalosis

A

increased neuromuscular irritability: paresthesias, tetany, seizures

Severe alkalosis; pt may become belligerent, CNS depression (confusion, lethargy, death 7.8pH)

18
Q

What are the three main causes of H+ loss in metabolic alkalosis?

A

If you have an excess loss of chloride from vomiting or suction, chloride never gets a chance to invite H+ into the stomach from the blood stream. If that never happened then you odnt have the H+ later on in the small intestine. The HCO3+ from the bloodstream down by the small bowel never gets invited into the small bowel and remains in the blood stream.

Renal H+ loss has to do with exchange of Na in the presence of excessive aldosterone. Too much aldosterone can lead to renal loss of H+ b/c it is retaining Na, they both have the same charge but Na has a higher pull so it remains in the blood and H+ gets excreted.
H+ loss in metabolic alkalosis may be caused by loop or thiazide diuretic or excess aldosterone via the renal system.

Posthypercapnic alkalosis: Rapid lowering of chronically elevated PCO2 results in metabolic alkalosis

19
Q

What is contraction alkalosis?

A

the increase in blood PH that occurs as a result of fluid losses (volume contraction). The change in PH is especially pronounced with acidic fluid losses causes by problems like vomiting.

20
Q

Metabolic alkalosis can be characterized by urinary chloride: what are the two categories?

A

-Chloride responsive (less than 10mEq/L); renal loss, or GI loss

OR

-chloride resistant (greater than 10mEq/L); excess mineralocorticoid such as cushings, hyperaldosteronism, exogenous steroids

21
Q

What is chloride sensitive metabolic acidosis? Chloride resistant?

Tx of each.

A

Chloride sensitive: chloride depletion resulting in renal Na conservation leading to reabsorption of HCO3 by the kidney.

Chloride resistant: direct stimulation of the kidneys to retain bicarb irrespective of electrolyte intake or losses.

Tx:
-Give NaCl, Cl sensitive will respond to tx and chloride resistant will not.

Chloride sensitive: NaCl, correct hypokalemia if present. Can give acids(NH4Cl and HCl) in extreme cases but can be dangerous and push them the other way.(acidic)

Chloride resisitant: treat underlying problem (e.g hyperaldosteronism)

22
Q

Alkali administration can cause milk-alkali syndrome. what is this?

A

post-correction metabolic alkalosis by admin of NaHCO3 to treat lactic acidosis or ketoacidosis.

administration of large quantities of citrate, large quantities of blood, or FFP.

citrate generates bicarb

23
Q

What are the most common causes of high serum anion gap and metabolic acidosis?

A

DKA and lactic acidosis

24
Q

High serum anion gap is d/t and increase in _____ and is almost always caused by on of the organic metabolic acidoses (lactic acidosis, ketoacidosis)

A

unmeasured ions!

25
Q

Use Delta Gap if the anion gap is _____ for ____.

What is Delta aniongap?

What is Delta HCO3?

A

Use delta gap if the anion gap is elevated fro metabolic acidosis.

AG measured - 12 = delta gap.

24-measured HCO3 = delta bicarb

26
Q

Delta gap:

  • metabolic alkalosis
  • metabloic acidosis
  • no additional disturbances
A

metabolic alkalosis: change in AG is greater than the change in bicarb

metabolic acidosis:
change in anion gap is less than the change in bicarb.

-if the AG and bicarb are equal or +/- 2 then no additional distrubance on top of their metabolic acidosis.

27
Q

Winters Formula:

  • equation
  • when do you use this?
  • results of the equation
A

Predicted PaCO2 = 1.5(HCO3) + 8… +/- 2

  • use this in metabolic acidosis only, looking for respiratory compensation.
  • If actual CO2 is high than the predicted CO2 they also have a resp acidosis
  • if actual CO2 is lower than predicted CO2 then they also have resp alkalosis
  • normal (+/2) appropriate response. no underlying resp disorder.
28
Q

Summers formula

  • equation
  • when do you use this?
  • results of equation
A

CO2= 0.7(HCO3 + 21)….+/- 2

-use this in metabolic alkalosis to determine if there is resp compensation

results:
if actual CO2 is higher than predicted CO2 then concomitant respiratory acidosis

if actual CO2 is less than predicted CO2 concomitant resp alkalosis.

29
Q

What are the main three causes of metabolic acidosis? metabolic alkalosis?

A
  • DKA
  • lactic acidosis
  • alcoholic acidosis

Alkalosis:
-Vomiting, NG suction, diuretics, dehydration, antacid overdose

30
Q

When might it be helpful to measure a urine chloride?

A

to determine the cause of metabolic alkalosis, whether the pt is resistant or responsive to Cl- administration. Cl- resistant means mineralcorticoid problem, responsive indicates GI or renal proble

Nephrology 2 (7 decks)

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