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Miller Basics of Anesthesia > Chapter 21: Acid-Base > Flashcards

Chapter 21: Acid-Base Flashcards

1
Q

base excess definition

A

amount of strong acid (HCL for BE >0) or strong base (NaOH for BE <0) required to return 1L of whole blood exposed in vitro to a PCO2 of 400 mm hg to a pH of 7.4

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2
Q

does base excess refer to respiratory or metabolic component of acid base disturbance

A

metabolic

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3
Q

at 37 degrees C the normal hydrogen ion concentration in arterial blood and ECF is what

A

35-45 nmol/L

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4
Q

normal plasma bicarb concentration is what

A

24 +/-2meQ/L

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5
Q

buffer systems are composed of what

A

base molecule and its weak conjugate acid

base buffer system and bind excess hydrogen, weak acid protonates excess base

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6
Q

what is the PKA

A

pH at which an acid is 50% protonated and 50% deprotonated

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7
Q

most important buffer systems in blood in order of importance

A

1) bicarb buffer system
2) hemoglobin buffer system
3) other protein buffer systems
4) phosphate buffer system
5) ammonia buffer system

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8
Q

CO2 + H20 —>

A

CO2 + H20 —> H2CO3 –> H+ + HCO3-

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9
Q

Hgb buffering system is important buffering system bc of its multiple _____ residues which is an effective buffer from ___ to ___ pH because it contains multiple what. this buffering depends on what

A

histidine
5.7-7.7

multiple protonatale sites on the imidazole side chains

depends on bicarb buffer to move CO2 intracellularly

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10
Q

CO2 diffuses freely into erythrocytes then what happens

hamburger shift

A

carbonic anhydrase resides, H+ and HCO3- formed, H+ are bound by hemoglbin and bicarb exchange back into plasma with extracellular chloride

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11
Q

at the lungs the reverse process of hamburger shift occurs: explain

A

chloride ions move out of the RBCs as bicarb enters for convresion back into CO2 which is then released back into the plasma and eliminated by the lungs

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12
Q

oxygenated vs deoxygenated hgb. ____ takes up more hydrogen ions which shifts the co2/bicarb equilibrium to produce more ___ which facilitates removal of ___ from peripheral tissues

A

deoxygenated hgb takes up more H ions which shifts the equation to the right to make more bicarb and facilitates removal of CO2 from peripheral tissues

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13
Q

central chemoreceptors lie on the ____ surface of the ___ and respond to changes in CSF pH

A

anterolateral medulla

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14
Q

doses CO2 diffuse across the BBB

A

yes then dissocates into H+

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15
Q

peripheral chemoreceptors are located where

A

common carotid arteries and aortic arch

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16
Q

carotid body chemoreceptors are sensitive to changes in what and communicate with the central respiratory centers via what

A

PaO2, PaCO2, pH, arterial perfusion pressure

communicate via glossopharyngeal nerve

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17
Q

peripheral chemoreceptors are most sensitive to what

A

PaO2

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18
Q

pts with bilateral carotid endarterectomies have almost no what drive

A

hypoxic vent drive

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19
Q

how many days does it take for renal response to acid base disturbance to be maximal

A

can be 5 days

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20
Q

renal response of ph changes occurs via what 3 things

A

1) reabsorptino of filtered HCO3-
2) excretion of titratable acids
3) ammonia

21
Q

where in the kidney is bicarb absorbed

A

80-90% in PCT

10-20% in DCT

22
Q

ammonia buffer system: describe it

A

its formed from deamination of glutamine to NH3 which passes cell membrane to enter the tubular fluid where it combines with hydrogen to form NH4+ which is trapped within the tubule and excreted in urine

23
Q

the kidneys are highly effective in protecting the body against alkalosis except in association with what deficiency or what excess

A

Na deficiency

mineralocortiocoid excess

24
Q

venous pH is only ____ to ___ less than arterial values

A

.03 to .04

25
Q

both PCo2 and PO2 ____ during hypothermia but ____ ___ is unchanged

A

decrease, serum bicarb, leads to increased pH

26
Q

alpha stat refers to what

A

protonation state of imidazole side chain of histidine

the pka of histidine changes with temp so its protonation state is relatively constant regardless of temp

27
Q

pH stat is different from alpha stat how

A

requires keeping a pts pH static at 7.4 based on core temp

28
Q

during cardiopulmonary bypass an anesthesia provider using ___ ____ would manage the pt based on an ABG measured at 37 degrees C and strive to keep that pH at 7.4 but the pts true pH would be higher. no extra adjustments needed for pts hypothermia

A

alpha stat

29
Q

during cardiopulmonary bypass an aneshtesia provider using ___ ____ wouidl manage the pt based on an ABG that is corrected for pts temp

A

pH stat

30
Q

the PO2 is decrfeased approxitamely ___% for every 1 degree C that pts temp is below 37

what about above 37

A

6% decrease

6% increase

31
Q

acedemia and myocardial contractility and catecholamines

A

decreased and release of catecholamines

32
Q

mild vs severe acidosis, myocardial contractility and catecholamines

A

with mild >7.2 the catecholamine release can make up for decreased contractility

with severe the myocardial response to catetcholamines decrease –> hypotension`

33
Q

severe alkalemia pH >___ can lead to what

A

7.6, decreased cerebral and coronary blood flow bc of arteriolar vasoconstirction

34
Q

3 main categories of respiratory acidosis causes

A

increased CO2 production

decreased CO2 elimination

Increased CO2 rebreathing or absorption

35
Q

what must be avoided in pts with chronic respiratory acidosis

A

avoid hyperventilation

36
Q

each of the following does it cause respiratory acidosis or alkalosis

intrinsic pulmonary dz like pna, ards, fibrosis, edema

pregnancy

liver disease

restrictive lung diseasse

upper airway obstruction

lower airway onstruction

chest wall restrtciton

PE

tumor, infection, trauma (CNS)

salicylates, progesterone, doxapram

A

intrinsic pulmonary dz like pna, ards, fibrosis, edema: acidosis

pregnancy: alkalosis

liver disease: alkalosis

restrictive lung disease: alkalosis

upper airway obstruction: acidosis

lower airway obstruction: acidosis

chest wall restriction: acidosis

PE: alkalosis

tumor, infection, trauma (CNS): acidosis

salicylates, progesterone, doxapram: alkalosis

37
Q

causes of nongap acidosis

A

renal losses
acetazolamide
GI losses
chloride administration (excessive)

RAG C

38
Q

normal anion gap value is

A

8-12

39
Q

an increase in the anion gap occurs when what happens

A

the anion replacing bicarb is not one that is routinely measured

40
Q

chronic metabolic acidosis as seen with chronic renal fialure is associated with what and why

A

loss of bone mass bc bufferse present in bone are used to neutralize acids

41
Q

administering sodium bicarb generates _____ which unless eliminated by ventilation can worsen any intracellular and extracellular acidosis

A

CO2

42
Q

causes of metabolic alkalosis

A 
chloride responsive
-Renal loss (diuretics)
-alkali administration (citrate in blood, acetate in TPN, nicarb
G- GI loss
respond to the RAG
chloride resistant
HRH
hyperaldosteronism
refeeding
hypokalemia
43
Q

compensatory response to metabolic alkalosis kidney

-dependent on what ions

A

sodium, potassium and chloride, if not sufficient cannot excrete bicarb. can treat by giving slaine and KCl so they can excrete more

44
Q

respiratory compensation for pure metabolic alkalosis is never more than ___% complete

A

75

45
Q

how to determine if a respiratory process is acute or chronic

acute process: pH cahnge of ___ for every 10mm hg change in Pco2 from 40 mm hg

chronic is a ___ change for every 10 mm hg change Pco2 from 40 mm hg

A
  1. 08

0. 03

46
Q

metabolic alkalosis formula for compensation

A

Pco2 = (0.7 x HCO3-) +21

47
Q

metabolic alkalosis compensation

if measured Pco2 is > calculated then concurrent ___ present

if measured PCO2 < calculated then concurrent

A

concurrent resp acidosis

respiratory alkalosis

48
Q

metabolic acidosis winters formula

if measured PcO2 > calculated then concurrent what

if measure PCO2 < calculated then concurrent what

A

PCO2 = (1.5 x hco3-) + 8

respiratory acidosis

respiratory alkalosis

Miller Basics of Anesthesia (1 decks)

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