Final Review - Personalized Pt 2 Flashcards
Oxygen used by cells at rest…
250 ml/min
Why doesnt CO2 need as large a gradient as oxygen to diffuse?
CO2 diffuses 20 x faster than O2
Hypoxic Hypoxia
inadequate O2 uptake
COPD
Stagnant/Ischemic Hypoxia
inadequate blood flow
clot
Anemic Hypoxia
inadequate oxygen carrying capacity
inactivated hgb
Histotoxic Hypoxia
interference with mitochondrial respiration
cyanide poisoning
Methods of O2 Transport
97% carried by RBC’s
dissolved in plasma - low capacity
Amount of O2 that can be dissolved in blood
0.0003 ml/100ml plasma
Hemoglobin
oxygen carrier protein
4 subunits, 2 alpha, 2 beta
only Fe2+ can bind to O2
How much O2 can 1gm of Hgb carry?
1.31 ml
Oxyhemoglobin curve axis & rightward
x axis = PaO2
y axis = saturation
rightward shift –> release O2 more
saturation will be less for a given PO2
Causes of rightward shift
increased CO2
increased temp
increased H+
increased 2,3 DPG
Average CO2 production in resting adult
200 ml/min
Mechanisms of CO2 transport
3% dissolved in blood
90% bicarb, HCO3 and carbonic acid
7% bound to hgb
** all reversible at lungs
What causes increased minute ventilation
hypercapnia and acidosis
Which materials act directly on the respiratory centers to increase strength inspiratory and expiratory motor signals?
carbon dioxide
hydrogen ions
**oxygen acts peripherally at carotid and aortic bodies
DRG
controls respiration at rest and provides basic rhythm
-vagal and glossopharyngeal sensory info to DRG
VRG
inactive during normal respiration
contributes to drive to increase respiration
stimulates abdominal muscles
Pneumotaxic Center
control switch off point
primarily limits inspiratory phase
also increases rate
Apneustic
works with pneumotaxic to control intensity of respiration
Hering-Breuer Reflex
protective feedback mechanism that limits overinflation
- stretch receptors send signals via vagus nerve to DRG when TV >1.5 L
- also increases rate
Chemo-Sensitive Area
on ventral medulla, responsive to CO2 and H+
Which ions can cross blood brain barrier?
CO2, not H+
CO2 stimulates H+ ions in CSF to stimulate resp center
Mountain climbing
adjusts in 2-3 days, loss of sensitivity to CO2, or H=, oxygen runs resp center
Alveolar ventilation curves
curves are displaced to the right at higher pH and left with lower pH
What controls voluntary respiration
cortex and higher centers
Is the potential for Cheyne-Stokes breathing present in everyone?
yes
- low CO
- brain damage
High risk PFT results
FEV1 <2L
FEV1/FVC < 0.5
VC <15 cc/kg in adult, <10 cc/kg in child
VC <40 - 50% predicted
To decrease air trapping…
change I:E ratio.
Histamine releasing drugs
pentothal (STP) Morphine atracurium mivacurium neostigmine abx
Extubation criteria
resp rate <30
ABG on FiO2 of 40% –> PaO2 >70, PaCO2 <55
NIF more negative than -20 cm H2O
VC >15 cc/kg
Extubation and FEV
FEV >50% –> not affected
FEV 25-50% –> some hypoxemia and hypercarbia, prolonged intubation probable
FEV <25% –> may not be able to wean
Intubation criteria
RR >35, VC <15 cc/kg
oxygenation PaO2 <70 on FiO2 of 40%
PaCO2 >55
-airway burn, chemical burn, epiglotitis, etc
TV
500 ml
IRV
3 L
ERV
1.1 L
RV
1.2L
IC
3.5 L
FRC
2.3 L
VC
4.6 L
TLC
5.8 L
Normally, FRC represents about ___% of TLC
40%
FVC
volume of air which can be forced exhaled out of lungs after pt has taken deepest breath possible
FEV1
forced volumes in 1 second
effort dependent
3-5L
**most important clinical tool in assessing severity of airway obstructive disease
Normal FEV1/FVC
75%
Flow-Volume Loops
help distinguish between obstruction and generalized pulmonary disease
-extrathoracic obstruction = decreased inspiratory flow
MVV or MBC
“will to live”
max amount they can exchange in 1 minute
Carboxyhemoglobin
from CO poisoning, shows 100%
Methemoglobin
shows 85%, absorbs equally at both wavelength
-benzocaine, NTG, nitrates
tx: methylene blue
cyanosis when 15% hgb is methgb
Gold standard for tracheal intubation…
EtCO2
*will not detect endobronchial intubation
Mainstream circuit
inline
connects to ETT, fast, do not need water trap
adds weight and dead space
Sidestream
diverting
pumps to outside circuit, takes longer
need water trap
dCO2
normal end tidal CO2 to arterial CO2 gradient
arterial is higher by 2-5 mmHg
-reflects alveolar dead space
increase dCO2
increased dead space
One lung positioning: down lung
dependent lung
nondependent lung = upper lung
Where does the axillary roll go?
upper chest wall, no axilla
during apnea…
PCO2 increases 5 mmHg for the first minute, then 3 mmHg for each additional minute
Hypoxia during one lung ventilation
add 5 cm CPAP to nondependent lung
add 5 cm PEEP to dependent lung
ask surgeon to clamp nondependent PA
double lumen tube sizes
women: 39 (insert 27 cm)
men: 41 (insert 29 cm)
Left double lumen tube
more common, easier to place
longer bronchial, shorter tracheal
MH
rare, inherited skeletal muscle syndrome, hypermetabolic rxn
triggered by volatile anesthetics, succ
ryr1 receptor
most specific indicator of MH
abrupt increase in EtCO2
earliest sign of MH
tachycardia
early signs of MH
abrupt increased in EtCO2 tachycardia cardiac arrhythmias generalized rigidity masseter rigidity metabolic/resp acidosis mottling
late signs of MH
acute renal failure circulatory failure myoglobinuria DIC elevated blood creatine phosphokinase hyperkalemia hyperthermia hypotension rhabdomyolosis cardiac arrest
MH treatment
dantrolene 2.5 mg/kg q5 mins, max 10 mg/kg
Dantrolene
inhibits Ca release from SR directly at ryanodine receptor
*Ca channel blockers cannot be given with dantrolene –> hyperkalemia and heart depression`
MAC amnesia
25% MAC
blocks anterograde memory in 50% of pts
MAC awake
50% MAC
prevents eyes opening on verbal command
MAC intubation
130% MAC
prevents movement/coughing with ETT placement
MAC Bar
150% MAC blocks autonomic response
lower mac =
higher potency
things that increase MAC..
age - term infant at 6 mo has highest MAC requirement hyperthermia chronic ETOH hypernatremia drugs that increase SNS catecholamines
things that decrease MAC…
hypothermia preop meds neonates/preemies, elderly pregnancy hyponatremia alpha 2 agonists, ca channel blockers
2nd gas effect
ability of fast uptake of N2O to accelerate rate of rise of alveolar partial pressure of 2nd agent
Diffusion Hypoxia
dilution of alveolar O2 concentration by large amount of N2O entering alveolus when N2O is d/c’d
-give 100% O2, dont extubate
Most important for speed of induction…
solubility
A larger partial pressure difference will…
enhance uptake and speed induction
Nitrous Oxide
good analgesic, safe in MH, PONV
avoid use with closed gas spaces
PVR, esp with pulm HTN
Halothane
vagal stimulation, esp >1 MAC –> pretreat with atropine
thymol preservative
sensitizes heart to catecholamines, caution w/ epi
avoid with liver dx
Isoflurane
heart cases
coronary steal
Desflurane
need special vaporizer
rapid wash in and wash out
not readily taken into fat
Sevoflurane
good for inhalation induction
rapid induction and emergence
compound A, avoid in renal failure
keep FGF atleast 2 L/min
Enflurane
can cause tonic clonic muscle activity,
avoid with renal failure and seizure pts
COPD
emphysema & bronchitis
**smoking
Chronic Bronchitis
symptoms- cough, sputum production, recurrent infections
mucous gland hyperplasia, mucous plugging, inflammation, edema
“blue bloaters”
Emphysema
*progressive dyspnea structural changes destruction of lung tissue, enlarged air spaces *alpha 1 antitrypsin deficiency "pink - puffer"
Pre-Op smoking cessation
-advise to stop atleast 12 hrs pre-op
reactivity decreases after 2 days, after 10 near nonsmoker
cessation >8 wks = reduced post op complications
How does smoking effect SNS…
- nicotine stimulates SNS catecholamines released from adrenal medulla - increased HR, BP & SVR
- persists 30 mins
- pre-oxygenate well and avoid airway manipulation until deep
Neuroaxial block >T10
diminished ability to cough
COPD and interscalene block
frequently blocks ipsilateral phrenic nerve
Asthma
hyper-reactivity
triad: wheezing, cough, dyspnea
Asthma treatment
pregnant - terbutaline oxygen, albuterol corticosteroids atrovent (ipratropium bromide) theophylline helium induction - ketamine, will increase secretions. pretreat with glyco
EtCO2 phases
A-B (1) - exhalation of anatomic deadspace
B-C (2) - exhalation of deadspace and alveolar
C-D (3) - alveolar
D-E (4) - inspiration
