Startprep 1 Flashcards
Pressure control vs support ventilation
Support: always pt-triggered; flow-cycled
Control: pt- or machine-triggered; time-cycled
In pressure-support, inspiration is terminated by ?
When inspiratory flow falls to a certain percentage (typically 25%) of peak inspiratory flow
Decelerating flow waveform in volume control
lower peak inspiratory pressure
In volume-control, which ventilator settings affect peak inspiratory pressure?
- TV
2. Inspiratory flow
What does a ventilator control?
- Volume
- pressure
- flow
- time
assisted vs controlled breath?
Assist control breath (hybrid mode)
- assisted: Pt initiates breath, which then triggers the ventilator.
- controlled: Ventilator initiates breath based on values prescribed by clinician.
auto-peep
Given that the alveoli are propped open by the positive pressure you are giving and not allowed time to deflate, this phenomenon is also known as auto-peep.
breath stacking
each breath is increasing the volume of lungs in the thorax
Assist-control mode (AC)
Detect pt-triggered breath—–>deliver full ventilator driven TV
Coronary perfusion pressure
DBP - LVEDP
Mitral vs tricuspid vavle
- MV: anterior & posterior leaflet
2. TV: septal, anterior, posterior leaflet
aorta
- intima
- media
- adventitia
coronary circulation
- Aortic root—>L & R Ostia–>L & R coronary artery
2.
SA node (Sinoatrial node)
- @ junction of SVC & RA
- single nodal artery: RCA (55-60%), LCX (40-45%)
- 60-100 bpm
AV node
- @ A-V junction
- 40-55 bpm
- RCA (80%), LCX (20%)
Note: SA–>atrial–>AV node–>bundels of His–>Purkinje fibers (slowest)–>
Heart-Ach
M2
Components of AV valve
leaflets, annulus, chordae, papillary muscles
phase of ventricular relaxation
(1) Isovolumetric: energy dependent
(2) Rapid filling phase
(3) Slow filling=diastasis (5%)
(4) Final filling during atrial systole (15-25%)
Baroreceptor reflex
carotid sinus reflex
- Maintenance of BP
- Carotid Sinus & aortic arch: circumferential & longitudinal receptors
- HTN–>(-) symp–>(-)HR, contractility, vascular tone; HypoNT–>reverse
- Blunt: anesthetics
Chemoreceptor reflex
- Carotid & aortic bodies: chemosensitive cells–>pH, PO2
- PaO2sinus nerve of Hering or Vagus–>medulla–>+ventilation
- para or symp via adrenal
Bainbridge reflex =atrial reflex
- stretch receptor: RA & cavoatrial junction
- (+) stretch—>vagal afferent—>CV center in medulla–>(-)para–>(+) HR
- EA or SA–>(-)sym–>vasodilation–>(-)atrial stretch–>(-)HR
Bezold-Jarisch reflex (BJR)
- noxious ventricular stimuli—> chemo- & mechano-receptors: LV wall–>hypoTN, bradycardia, coronary A dilatation
- bradycardia: atropine
Valsalva Maneuver
think
Cushing reflex
- Increased ICP–>medullary vasomotor center ischemia–>+symp–>HTN–>reflex bradycardia; –>irregular breathing or apnea
- Cushing’s triad: HTN, bradycadia, irregular breathing
Oculocardiac Reflex
- pressure on eye or traction on surrounding structure–>+para–>bradycardia: atropine
principal determinants of myocardial oxygen demand
- wall tension
- contractility
- heart rate
Predominant autonomic input to hear
parasympathetic via vagus at rest –>normal HR 60-80
Diastolic dysfunction is a major cause of heart failure: true or false?
True. Vernticular stiffening causing impaired ventricular filling is a major cause of heart failure
oculo-cardiac reflex is modulated by which CN
‘Five & dime’: afferent via trigeminal (V) & efferent via vagus (X) causing bradycardia
chief determinants of wall tension
- preload
2. afterload
Major determinant of osmotic pressure In capillary
Plasma proteins
Phase I vs phase II
I: train of four ratio>0.7
II: anticholinesterase drugs–>block
Fade on train of four stimulation
I + II: none has sustained tetanu
High vs low gas flow —> accuracy measuring gas flowing a Thorpe tube w/ a bobbin float
High: turbulence, gas density
Low: laminar, viscosity
A 50 year-old African-American woman has a history of chronic pain that has been stable on multimodal daily pain medication. She presents to the emergency room complaining of vivid dreams and feeling weird, which developed about a day after she started taking Isoniazid for tuberculosis.
Her pain medication regimen likely includes ketamine, and coadministration of isoniazid would likely decrease the metabolism of ketamine as a result of competitive hepatic metabolism. This increased plasma concentration of ketamine could lead to new side effects.
airway nerve innervation
- CN V: mucous membranes of nose: V1 anteriorly (anterior ethmoidal nerve), V2 posteriorly (sphenopalatine nerve); palatine N. (sensory fibers from V): palate; lingual N. (br. of V3): anterior 2/3 tongue
- CN IX (glossopharyngeal): posterior 1/3 tongue, roof of pharynx, tonsil, undersurface of soft palate; easily blocked where it crosses the palatoglossal arch
- Sensation of taste: VII anteriorly, IX posteriorly
- X: sensation bellow epiglottis–>superior laryngeal N–>external br. (motor–cricothyroid muscle) & internal br. (sensory–>larynx between epiglottis & vocal cords, hypopharynx posterior to those structures); recurrent laryngeal N–>sensory: larynx below vocal cords & trachea; motor: all laryngeal muscles except cricothyroid muscle
pharynx extends from base of skull to ?
cricoid cartilage
larynx
- epiglottis - lower end of cricoid cartilages
- 9 cartilages: 3 single (thyroid, cricoid, epiglotic), 3 paired (arytenoid, coniculate, cuneiform)
- cricothyroid membrane: best access–>percutaneous airway
recurrent laryngeal nerve
- Sensation below vocal cord
- all intrinsic muscles of larynx except chricothyroid muscle
- can be damaged during thyroid surgery & by ETT cuff laying just below vocal cord
- block: transtracheal injection via cricothyroid membrane
superior laryngeal nerves
- external branch: motor–>cricothyroid muscle
2. Internal: sensoryminimal; bil–>hoarseness & loss of sensation above vocal cords–>aspiration
Vocal Cord Palsies
- recurrent laryngeal N: unilateral –>hoarseness; bil–>aphonia, stridor, airway obstruction
- vagus N bil injury–>both
6 major anatomic differences between infant vs adult airway
(1) relatively large tongue
(2) relatively large occiput
(3) more cephalad larynx
(4) epiglottis is narrow, omega shaped, and floppy
(5) vocal cords slant anteriorly(6) narrowest part of the larynx is the cricoid cartilage
* persist until 8 yo
Airway topicalization
nebulized 4% lidocaine
which arteries provide blood supply to larynx?
laryngeal branches derived from superior & inferior thyroid arteries
Where does trachea become intrathoracic?
At 6th cartilaginous ring
When doing bronchoscopy, which important landmark helps to distinguish right from left mainstem bronchus?
Trifurcation of right upper lobe bronchus with 3 segments is a very important landmark
DLco
- diffusing capacity of the lung for carbon monoxide
- independent risk factor for pulmonary resections
- preoperative DLCO < 40% of predicted is a reliable marker of severe lung disease
- low HCT–> partially correctible cause
Apneic Oxygenation
- relative ability to maintain oxygen saturation in blood during absent ventilatio
CO2 rise in apneic person
- First min–>6 mmHg
2. Thereafter–>3 mmHg/min
How is CPAP able to maintain oxygenation?
CPAP stents lungs open–inhibiting shunting—>oxygen tension in blood to remain relatively constant
Bohr effect?
Increased oxygen release from hemoglobin in response to higher carbon dioxide tension or lower pH
hypopharynx
the laryngeal part of the pharynx extending from the hyoid bone to the lower margin of the cricoid cartilage
each 1 mmHg increase in PaCO2 (w/I physiologic range (20 -80mm Hg)
- CBF increase by 1.8ml/100 g brain tissue /min
2. CBV increase by 0.04 ml/100 g brain tissue/min
Robin Hood effect
In areas of focal ischemia, where vessels are already maximally dilated, the ability of hypoxia to induce vessel dilation is lost. The Robin Hood effect describes the fact that under this circumstance of lost vessel responsiveness to hypoxia in an ischemic region, intentional hyperventilation (by inducing vasoconstriction of surrounding normal vasculature) may transiently improve perfusion of the ischemic tissue bed (shunting blood flow to the “neediest” areas). However, the Robin Hood effect is not predictable. When focal ischemia is suspected, the usual approach is mild hyperventilation.
hypercarbia vs MAC
Hypercarbia does not affect MAC significantly until PaCO2 exceeds 90-100 mm Hg.
PaO2 vs SaO2
PaO2 95 mm Hg -->SaO2 of 97% 95-->97% 40-->75% 26.8-->50% (P50) 40-50-60--->70-80-90
apneic threshold
normal adult: PaCO2 = 32 mmHg
Threshold for substantial increase in ventilation is a PaO2<
60 mmHg
Which chemoreceptor is more involved in maintaining ventilation: peripheral or central?
Central
The apneic threshold is___mmHg (above /below) the resting PaCO2
The apneic threshold is usually 4-5 mmHg below the resting PaCO2 & is usually about 32 mmHg in normal awake adults
fluid requirement of 1 degree centigrade above 37
addition of 2.5 mL/kg for every 24 hours
diruretics–>? Na+
—>hypernatremia
glucose treatment
Adults can use glucose at a rate of 3 to 5 mg/kg/min, and less in a stress state such as surgery. The rate of disposition of glucose in young children is 4 to 8 mg/kg/min. Healthy infants become hyperglycemic when 5% dextrose is included in maintenance fluids, and 1% dextrose is adequate to prevent hypoglycemia in infants.
Clinical signs of hypovolemia
Dry mucous membranes, positional blood pressure changes, decreased urine output, decreased sensorium
MCC of fluid loss during surgery
- Evaporation
- fluid shift
- blood loss
FSBG
Finger Stick Blood Glucose
NS
- higher osmolality, Chloride
- lower pH
- w/o K, Ca
- > 3 L–>hyperchloremic metabolic acidosis
LR
- Lactate: may not –>pyruvate efficiently during lactic acidosis or severe liver failure
- K, Ca
Normosol
- most expensive
- critically ill ps w.diminished compensatory mechanisms
- No Ca–>may used w/ pRBC
- K
- same as plasmalyte expt pH
colloid: protein vs non-protein
- protein: albumin, gelatin-based (not used in USA)
- albumin: well-tolerated: w/o anaphylaxis, infection, coag
- Non-protein: Dextrans (used in vascular, but not volume resuscitation) & hydroxyethyl starches (anticoag if hetastarch>20 ml/kg/day; pruritis; higher M & M in critically ill pts)
What percentage of anesthetized patients develop atelectasis?
90%
RBF
- RBF>20% of resting CO
- consume 10% body’s O2 received
- 90-95% to cortex
- autoregulation: 80-180 mmHg MAP
nephron
- two million/ per kidney
- glomerulus + tubule
- cortical (85% RBF) vs juxtamedullary (10%); # 7:1
- filtriation +reabsorption + secreation –>urine
mTAL
- thick portion of ascending limb of loop of Henle
- impermealble to H2O
- most energy consuming–>greatest risk of ATN
distal tubule
major site of parathyroid hormone and vitamin D-mediated calcium reabsorption
Cr vs GFG
inverse & exponential: doubling of serum Cr = 1/2 GFR)
tubular function test :FENa vs FEUrea
FENa = Fractional Excretion of sodium–>tubular Na reabsorption
- express Na clearance as % of CCr
- (U Na/ S Na)/(U Cr/S Cr)x100%
- hypovolemic: 3%
- inaccurate: diuretic mes
FEUrea
- tubular reabsorption of urea
- % of CCr
- FEUrea= ( UUrea × PCr ) / ( UCr × PUrea ) × 100%
- normal: 35-55%
- pre-renal AKI: 55-60%
- useful in diuretics used
What substances are renal vasodilators?
PG E2, D2, I2 Kinns Endothelin Atrial natriuretic peptide NO dopamine Fenoldopam
How is oliguria is defined?
- in previously normal kidneys: UOP <0.5 mL/Kg/hr
What substances are renal vasoconstrictors?
Epi Norepi AT II Endothelin Vasopressin PG F2 Thromboxane
Carbonic anhydrase
- acetazolamide
- methazolamide)
- Na-H exchanger: proximal tube
- (-) carbonic anhydrase–(-) reabsorption of Na & HCO3–>alkalinized urine–>mild systemic metabolic acidosis
- weak: distal compensation
- used: alkalinized urine, altitude sickness, open-angle glaucoma
osmoticdiuretics
- mannitol
- urea
- filtered and no reabsorption
2. In poor cardiac reserve–>acute pulm edema
Loop diuretics
- furosemide
- bumetanide
- torsemide
- (-) Na-K-Cl symporter: ascending limb of loop of Henle
- Increase venous capacitance–>LVEDP–>LVF
- cirrhosis, renal dz, HF
- –>hyponatremia, hypokalemia
- ototoxicity: rapid use
- Increase non-albumin bound warfarin & clofibrate
Thiazide diuretics
- (-) Na-CI symporter: distal convoluted tubule
2. kypokalemia, hyponatremia, kypercalcemia, metabolic alkalosis
K sparing diuretics
(-)Na channels–>hyperkalemia
1. triamterene
2. amiloride
mineralocorticoid receptor anagonist: spironolactone–>hyperkalemia, metabolic acidosis, gynecomastia, hirsutism
jugular notch
- at superior aspect of manubrium between prominent medial portions of clavicles
- at level of inferior border of T2
sternal angle
- T4-T5 intervertebral disc
- 2nd costal cartilage
- tope of aortic arch
- tracheal bifurcation
nipple
- Male: 4th intercostal space
2. female: lower
sternum
- T5-9
2. xiphoid process
tension pneumothorax—-> emergency thoracocentesis
midclavicular line in the second intercostal space
Posterior thoracic wall
- C7: most prominent # palpable
- T2 process–>superior angle of scapula
- T3 process–>most medial aspect of scapula
- T7–>inferior angle of scapula
midaxillary line
point of bifurcation of intercostal nerves into anterior and posterior branches
costal groove
- inferior internal surface of each rib
- contains corresponding intercostal neurovascular bundle
- superior–> inferior: V->A->N
how many segments in L & R lungs
Right: 10
Left: 8
lung
- 3 borders: anterior, posterior, inferior
- 3 surfaces: costal, medial, inferior (diaphragmatic)
- cupola of pleura & apex of lung: 2 cm superior to medial third of clavicle
fissure
- oblique (R & L): below T3 spine posterior–>6th costal cartilage anterior
- horizontal (R): 4th costal cartilage anterior–>horizontally to oblique
costodiaphragmatic recess
- at junction of costal & diaphragmatic pleura
2. 8th to 10 th rib along midaxillary line
mediastinum
- superior: manubriumT1-4 vertebrae
2. inferior: below line from sternal angle to disc between T4-5: anterior, middle, posterior
heart surface
- anterior: RV
- diaphragmatic: LV + portion of RV
- R pulmonary: RA, 1 cm from sternal boder, posterior to 3rd R costal cartilage
- left pulmonary: LV
describe surface anatomy of heart
- One cm Right of sternal border between 3rd & 6th costal cartilage
- Left 2nd intercostal space 1 cm from sternal border
- Left 5th intercostal space @ midclavicular line
