3. Acid Base Management Flashcards
1
Q
venous CO2 normal value
A
24-30 mEq/L
(CO2 + HCO3-)
2
Q
arterial CO2 normal value
A
22-26 mEq/L
(HCO3-)
3
Q
PaCO2 normal
A
35-45 mmHg
4
Q
PvCO2 normal
A
40-50 mmHg
5
Q
PvCO2 is normally _______ compared to PaCO2
A
PvCO2 is 5 mmHg higher than PaCO2
6
Q
if a pt is poorly perfused, what happens to the PvCO2:PaCO2 gradient
A
increases
7
Q
PaO2 of atmosphere normal
A
160 mmHg (sea level)
8
Q
PaO2 normal value
A
70-100 mmHg
9
Q
what happens to PaO2 as you age?
A
it decreases
10
Q
PvO2 normal value
A
30-40 mmHg
11
Q
CaO2 normal value
A
16-20 mL/dL
12
Q
CvO2 normal value
A
12-16 mL/dL
13
Q
DO2
A
total delivery of O2 per minute
14
Q
DO2 normal
A
1000 mL of O2 delivered per minute
15
Q
normal Hb
A
15 g/dL
16
Q
normal SaO2
A
93-98%
17
Q
normal CO
A
5 L/min
18
Q
mvO2 normal
A
60-80%
(up to 90%)
19
Q
ScvO2 normal
A
70-75%
20
Q
difference between PAO2 and PaO2
A
A-a gradient
21
Q
A-a gradient: room air
A
5-15 mmHg
22
Q
A-a gradient: elderly
A
15-25 mmHg
23
Q
A-a gradient: 100% FiO2
A
10-110 mmHg
24
Q
normal MV
A
7-8 L/min
25
Va =
2/3 of MV
26
Vd =
1/3 of MV
27
VCO2
200 mL/min
28
what happens to VCO2 under GA
decreased by up to 60%
29
VO2: normothermic adult
250 mL/min
30
VO2: infants
6-8 mL/kg/min
31
VO2: adults
3-4 mL/kg/min
32
pH
7.35-7.45
33
%MetHB on ABG
<2%
34
%COHb on ABG
<3%
35
HCO3-/PaCO2 ratio
20:1
36
PaO2/Fio2 ratio
480
37
Anion Gap
8-16 mEq/L
38
Base Excess
-2.0 - 2.0 mEq/L
39
serum lactate concentration
< 2 mmol/L
40
lactic acidosis
serum lactate > 5 mmol/L
41
Vt
volume of air expired in 1 breath
including dead space
42
MV
total volume of air breathed in 1 min
including dead space
43
MV =
MV = RR*Vt
44
Vd
volume of dead space in 1 breath
45
Vd: pulmonary dz
> 1/3 of Vt
46
Vd/Vt
amount of dead space ventilation that occurs in 1 min
47
Vd/Vt =
Vd/Vt = Vd*RR
48
alveolar volume
amount of air in 1 breath that reaches the alveoli and participates in gas exchange
49
alveolar volume =
alveolar vol = Vt - Vd
50
Va
amount of air in 1 min that reaches the alveoli and participates in gas exchange
51
Va =
Va = (Vt - Vd) *RR
52
blood gas: technically
gas under ordinary conditions
dissolved in our blood
53
blood gas: clinically
collection of values that may include actual blood gases but also include other values
54
ABG measures (6)
1. pH
2. PaCO2
3. HCO3-
4. PaO2
5. SaO2
6. Base excess
55
ABG additional values (6)
1. Hb/Hct
2. K+
3. Glu
4. Ca2+
5. COHb
6. MetHb
56
3 forms of CO2 in the body
1. PaCO2
2. HCO3- (plasma)
3. HCO3- (Hb-bound)
57
PaCO2 accounts for ________ of all CO2
5-10%
58
HCO3- in plasma accounts for _______
60-65%
59
HCO3- bound to Hb accounts fo
30%
60
HCO3- total in body
90-95% of all CO2
61
lechatlier principle: drive RIGHT
incr CO2
or
decr HCO3-
62
lechatlier principle: drive LEFT
decr CO2
or
incr HCO3-
63
acids drive reaction
RIGHT
64
acids ____ H+
incr H+ ions
65
bases drive reaction
LEFT
66
bases ____ H+
decr H+ ions
67
respiratory acidosis cause
hypoventilation
incr PaCO2
68
respiratory acidosis diagnosis
low pH
high PaCO2
69
respiratory alkalosis cause
hyperventilation
decr PaCO2
70
respiratory alkalosis diagnosis
high pH
low PaCO2
71
metabolic acidosis cause
decr HCO3-
72
metabolic acidosis diagnosis
low pH
low HCO3-
73
metabolic alkalosis cause
incr HCO3-
74
metabolic alkalosis diagnosis
high pH
high HCO3-
75
pH is determine by
HCO3- to PaCO2 ratio
76
acidosis SE (6)
1. decr contractility
2. decr catecholamine response
3. decr coag / incr bleeding
4. incr PVR
5. incr risk of Vfib
6. incr plasma K+
77
alkalosis SE (6)
1. shifts O2-Hb LEFT
2. incr SVR
3. cerebral vasoconstriction
4. decr pVR
5. decr plasma K+
78
pH ~
pH ~ HCO3- / PaCO2
79
base excess: technically
amount of acid or base needed to return the blood to pH 7.4 and PaCO2 to 40 mmHg
80
base excess: clinically
tells us if pt has too much or too little base in the blood
81
normal Base excess
-2 to 2 mmol/L
82
base excess > 2mmol/L
too much base
metabolic alkalosis
83
base excess < -2 mmol/L
not enough base
metabolic acidosis
84
what indicates metabolic acid/base status
base excess
85
what indicates respiratory acid/base status
PaCO2
86
PaCO2 should be _______ to EtCO2
PaCO2 should be 3-5 mmhg higher than EtCO2
87
if PaCo2 is significantly higher than EtCO2, then what might that suggest?
1. lung disease
2. hypotension
3. low CO
88
PaCO2 =
PaCO2 = [(VCO2)*0.863]/Va
89
PaCO2 is proportional to
VCO2
90
PaCO2 is inversely proportional to
Va
91
with each subsequent minute of apnea
CO2 will increase exponentially
92
venous labs names
BMP
Chem 7
Electrolyte panel
93
venous sample includes which form of CO2
CO2
HCO3-
94
tCO2
venous CO2 (CO2 + HCO3-)
95
normal Venous CO2/HCO3-
24-30 mEq/L
96
normal arterial HCO3-
22-26 mEq/L
97
PAO2
partial pressure of O2 in the alveoli
98
PAO2 is determined by
FiO2
barometric pressure
99
PAO2 is minimally effected by
minute venilation
100
incr barometric pressure causes _____ FiO2
incr FiO2
101
can you measure PAO2
no - you can calculate it
102
PaO2
partial pressure of O2 dissolved in the arteries
103
PaO2 is what % of total body O2
1.5%
104
what determines PaO2
PAO2
105
PaO2 is not affected by
[Hb]
SaO2
CarboxyHb
MetHb
CyanoHb
106
normal PaO2 on room ari
80-100 mmHg
107
PaO2 estimate
5*FiO2
108
how to measure PaO2
blood sample
109
SaO2
% of Hb saturate w/O2
110
SaO2 measured
blood sample
pulse ox
111
SaO2 represents what % if total body O2
98.5%
112
what is SaO2 primarily determined by
PaO2
113
effect of CarboxyHb and MetHb on SaO2
decreases SaO2
114
right shift
Hb bind less tightly
115
left shift
Hb bind more tightly
116
right shift causes
acidosis
hypercarbia
hyperthermia
anemia
incr 2,3-DPG
117
left shift causes
alkalosis
hypocarbia
hypthermia
carboxyhb
methb
118
supp O2 effect on PAO2
incr PAO2
== incr PaO2
== incr SaO2
119
calculating PAO2 allows for assessment of
lung function
120
A-a gradient
PAO2 compared to PaO2
121
normal A-a gradient
5-15 mmhg
122
wide A-a gradient
>15 mmHg
123
wide A-a gradient indicates
impaired gas exchange
or
increased R-L pulm shunting
124
normal A-a gradient indicates
normal lung function
125
equation used to calculat PAO2
alveolar gas equation
126
PAO2 =
PAO2 = PiO2 - (1.2)(PaCO2)
== PAO2 = (FiO2)(Pb-WVP) - 1.2*PaCO2
== PAO2 = (FiO2*713) - 1.2*PaCO2
(sea level)
127
primary determinant of PAO2
FiO2
128
PAO2 estimation
PAO2 ~ 102 - [age/3]
129
normal PaO2/FiO2 ratio
> 400
130
does PaO2/FiO2 vary with supp O2
nope
131
ALI PaO2/FiO2
< 300
132
ARDS PaO2/FiO2
< 200
133
CaO2 =
CaO2 = SaO2*Hb*1.34 + PaO2*0.003
134
what factors contribute to total arterial O2 content
PaO2
SaO2
Hb
135
which has a greater effect on CaO2: SaO2 or Hb
equal effect
136
which has a greater effect on CaO2: SaO2 or PaO2
SaO2
137
CvO2 =
CvO2 = (SvO2)*Hb*1.34 + PvO2*0.003
138
normal SvO2
70-75%
(draw off central line)
139
VO2 =
VO2 = CO*(CaO2-CvO2)*10
140
DO2
delivery of O2
amount of O2 available to tissue perfusion per minute
141
DO2 =
DO2 = CaO2*CO*10
142
DO2 is mostly dependent on
SaO2 and Hb
143
DO2 is minimally dependent on
PaO2
144
DO2 units
mL/min
145
hyper/hypoventilation refer to
CO2 removal not respiratory rate
146
hypoxia
impaired O2 perfusion
147
hypoxemia
decr in blood O2 content (CaO2)
148
hypoxemia hypoxia
hypoxia due to reduced arterial O2 saturation (SaO2)
149
anemic hypoxia
hypoxia due to decr [Hb] which leads to decr total O2 content in blood (CaO2)
normal SaO2
150
anemic hypoxia SaO2
normal
151
ischemic hypoxia
hypoxia due to decr blood flow to the tissues
152
causes of ischemic hypoxia
low CO
hypovolemia
severe vasoconstriction
etc
153
histotoxic/cytotoxic hypoxia
hypoxia due to inability of tissues to take up or use the O2 from the bloodstream
normal blood content
normal O2 delivery
154
causes of histotoxic/cytotoxic hypoxia
cyanide poisoning
carbon monixide posioning
methemoglobinemia
septic shock
impaired mitochondrial function
155
what happens to cerebral blood flow in hypoxic pt?
cerebral blood flow increases to deliver more O2 to brain
156
what pts should hypoxia be avoided in?
pts w/closed head injury
pts w/increased ICP
157
below what PaO2 does cerebral BF increase rapidly?
60 mmHg
158
Bohr effect
O2 being displaced from Hb as PaCO2 increases
159
Haldane effect
CO2 being displaced from Hb as O2 concentration increases
160
what Hb is more affinitive for CO2
deoxy Hb in peripheral veins
161
what Hb is less affinitive for CO2
oxy Hb in pulm capillaries
162
respiratory acidosis
incr PaCO2
163
respiratory acidosis diagnosis
low pH
high PaCO2
164
respiratory acidosis compensation
kidneys reabsorb HCO3- causing
1) incr HCO3-
2) incr pH
3) incr PaCO2
165
respiratory acidosis treatment
incr pt MV
166
respiratory alkalosis
decr PaCO2
167
respiratory alkalosis diagnosis
high pH
low PaCO2
168
respiratory alkalosis compensation
kidnesy excrete HCO3- causing
1) decr HCO3-
2) decr pH
3) decr PaCO2
169
respiratory alkalosis treatment
decr MV
170
metabolic acidosis
decr HCO3-k
171
metabolic acidosis diagnosis
low pH
low HCO3-
172
metabolic acidosis compensation
pt hyperventilates causing
1) decr PaCO2
2) incr pH
3) decr HCO3-
173
metabolic acidosis treatment
give bicarb
174
bicarb dosing
0.3*weight*base excess
175
metabolic alkalosis
incr HCO3-
176
metabolic alkalosis diagnosis
high pH
high HCO3-
177
metabolic alkalosis compensation
pt hypoventilates causing
1) incr PaCO2
2) decr pH
3) incr HCO3-
178
metabolic alkalosis treatment
reverse the cause
179
normal PaCO2
40 mmHg
180
normal HCO3-
24 mEq/L
181
in respiratory acidosis, for each 10 mmHg increase in PaCO2: acute HCO3- effects
HCO3- incr 1 mEq/L (acute)
182
in respiratory acidosis, for each 10 mmHg increase in PaCO2: chronic HCO3- effects
HCO3- incr 4 mEq/L (chronic)
183
in respiratory alkalosis, for each 10 mmHg decrease in PaCO2: acute HCO3- effects
HCO3- decr 2 mEq/L
184
in respiratory alkalosis, for each 10 mmHg decrease in PaCO2: chronic HCO3- effects
HCO3- decr 4 mEq/L
185
in metabolic acidosis, PaCO2 should
PaCO2 should decrease 1.2x the HCO3- decrease
186
in metabolic alkalosis, PaCO2 should
PaCO2 should increase 0.7x the HCO3- increase
187
if pt has a respiratory distrubance, the body adjusts
HCO3-
188
if pt has metabolic disturbance, the body adjusts
PaCO2
189
routinely measured cations
Na+
K+
190
routinely measured anions
HCO3-
Cl-
191
plasma charge
neutral
192
"anion gap"
difference in the number of measured cations and measured anions
193
2 ways to calculated AG
1. AG = measured Cat - measured anions
2. AG= unmeasured anions - unmeasured cations
194
AG =
AG = (Na+ + K+) - (HCO3 + Cl-)
195
what can be omitted from AG equaation
K+
(relatively small)
196
AG ==
AG = Na+ - (HCO3- + Cl-)
197
normal AG
12 +/- 4 mEq/L
198
anion gap increases if (4)
1. # measured cations incr
2. # measured anions decr
3. # unmeasured anions incr
4. # unmeasured cations decr
199
anion gap decreases if (4)
1. # measured cations decr
2. # measured anions incr
3. # unmeasured anions decr
4. # unmeasured cations incr
200
why is anion gap useful
helps with differential diagnosis of disease states
201
lactic acidosis anion gap
high (widen) anion gap acidosis
202
lactic acid breaks down into
lactate
H+
203
why does lactic acidosis incr anion gap?
1. incr unmeasured anions (lactate)
2. decr measured anions (HCO3- binding H+)
204
excess NaCl
hyperchloremic
acidotic
start losing base
205
normal anion gap acidosis (2)
1. direct loss of HCO3-
2. incr [Cl-]
206
common cause of direct HCO3- loss
GI (diarrhea)
renal dysfunction
207
common cause of hyperchloremic metabolic acidosis
excess 0.9% N/S
208
low anion gap acidosis
209
low anion gap alkalosis
hypoalbuminemia
loss of albumin (-)
retention of HCO3-/Cl-
210
DKA pts most likely have
T1D
211
what causes DKA
lack of insulin
212
what does lack of insulin cause
cells break down fats in order to create sugar
== produced ketone bodies
213
are ketone bodies acids or bases
acids
214
what happens when blood sugar gets too high
kidneys cant keep up with filtration
-- sugar spills into renal tubules
-- incr osmotic diuresis
-- hypovolemia
215
what should we give with insulin
K+
216
DKA symptoms
1. hyperkalemia
2. acidosis
3. hypovolemia
4. K+ disturbnaces
5. Na+ disturbances
6. hyperosmlarity
217
hyponatremia is seen in what amount of pts with DKA
2/3
218
DKA: K+ disturbance
hyperkalemia most common
219
DKA: Na+ disturbance
hyponatremia most common
220
DKA treatment
1. admin insulin
2. K+ infusion
3. add glu w/insulin infusion
4. give bicarb
5. fluid resuscitation
221
when do you give insulin
K+ > 3.3 mEq/L
222
what should you correct prior to starting insulin therapy?
correct K+ level
223
when should you start adding glu to insulin infusion
glu = 250-300 mg/dL
224
glucose insulin infusion dosing
1 unit insulin per 5g glu
(5 units insulin per amp D50)
225
how much fluid is lost in DKA
6-9L
226
how much fluid should be replaced in DKA
total volume of loss within 24-36 hrs
227
how much fluid is given in DKA resucitation during the first 8-12 hrs
50% of volume
228
which fluid for DKA resuscitation?
crystalloid
- NS more popular than LR due to hyponatremia
229
air in blood sample: CO2 diffusion
CO2 diffuse OUT of blood INTO air
230
air in blood sample PaCO2
falsely lowerd PaCO2 reading
231
*pt on 100% O2*
air in blood: O2 diffusion
O2 diffuse OUT of blood INTO air
232
* pt on 100% O2*
air in blood PaO2
falsely lowerd PaO2 reading
233
*pt on room air*
air in blood: O2 diffusion
O2 diffuse OUR of air INTO blood
234
*pt on room air*
air in blood: PaO2
falsely elecated PaO2
235
blood samples colder than 37C
wil be warmed
236
blood samples warmer than 37C
will be cooled
237
what happens to PaO2 and PaCO2 when blood is warmed
PaO2 Incr
PaCO2 incr
238
what happens to PaO2 and PaCO2 when blood is cooled
PaO2 decr
PaCO2 decr
239
cold blood samples have
falsely elevated PaO2/PaCO2
240
warm blood samples have
falsely lowered PaO2/PaCO2
241
pregnancy PaO2
increases
(due to incr MV)
242
pregnancy pH
increases
(due to incr MV and resp alkalosis)
243
pregnancy HCO3-
decreases
244
neonate pH
lower
(7.2)
245
neonate PaO2
lower
50-80 mmHg
246
neonate PaCO2
normal
35-45 mmhg
247
