16 Critical Care Flashcards
1
Q
Mean arterial pressure
A
MAP = CO x SVR
2
Q
Cardiac index
A
CI = CO/BSA
3
Q
Define preload
A
Left ventricular end-diastolic length
Lineraly related to LV end diastolic volume and filling pressure
4
Q
What percentage of CO does kidney get? Brain? Heart?
A
Kidney 25%
Brain 15%
Heart 5%
5
Q
Define afterload
A
Resistance against the ventricle contracting
SVR
6
Q
Define stroke volume
A
Determined by LVEDV, contractility and afterload
SV = LVEDV - LVESV
7
Q
Define ejection fraction
A
EF = SV/LVEDV
8
Q
Determinants of end-diastolic volume
A
Preload
Distensibility of the ventricle
9
Q
Determinants of end-systolic volume
A
Contractility
Afterload
10
Q
Define Anrep effect
A
Automatic increase in contractility secondary to increased afterload
11
Q
Define Bowditch effect
A
Automatic increase in contractility secondary to increase heart rate
12
Q
How do you determine the arterial O2 content?
A
CaO2 = Hgb x 1.34 x O2sat + (Po2 x 0.003)
13
Q
How do you determine O2 delivery?
A
O2 delivery = CO x CaO2 x 10
14
Q
How do you determine O2 consumption?
A
Vo2 = CO x (CaO2 - CvO2)
15
Q
Normal O2 delivery-to-consumption ratio?
A
5:1
CO increase to keep this ratio constant
O2 consumption is supply independent (until very low levels of delievery are reached)
16
Q
Causes of right shift of Oxyhemoglobin curve?
A
O2 unloading Increased CO2 Increased 2,3-DPG Increased temp Increased ATP Increased H+ ions (decreased pH)
17
Q
Increased SvO2 occurs when:
A
Increased shunting of blood
Decreased oxygen extraction (i.e. sepsis, cirrhosis, cyanide toxicity, hyperbaric O2, hyptohermia, paralysis, coma, sedation)
18
Q
Decreased SvO2 occurs when:
A
Increased O2 extraction
Decreased O2 delivery
19
Q
Things that can effect pulmonary wedge pressure?
A
Pulmonary hypertension Aortic regurgitation Mitral stenosis Mitral regurg High PEEP Poor LV compliance
20
Q
Hemoptysis after flushing Swan-Ganz catheter?
A
Increase PEEP (tamponade the pulmonary artery bleed) Mainstem intubate non-affected side Fogarty balloon down mainstem on affected side Possible thoracotomy and lobectomy
21
Q
Relative CI to swan-ganz catheter?
A
Previous pnumonectomy
Left bundle branch block
22
Q
Approximate Swan-Ganz catheter distance to wedge?
A
RSCV 45cm
RIJ 50cm
LSCV 55cm
LI 60cm
23
Q
What is the only way to measure pulmonary vascular resistance?
A
Swan-Ganz catheter (NOT ECHO)
24
Q
When should you take wedge pressure?
A
End-expiration
Ventilatory method does not matter
25
Primary determinants of myocardial O2 consumption?
Increased ventricular wall tension
| Heart rate
26
Normal A-a gradient in a non-ventilated patient?
10-15mmHg
27
Blood with lowest venous saturation?
Coronary sinus blood (30%)
28
Adrenal insufficiency
MCC - withdrawal of exogenous steroids
Acute: cardiovascular collapse, unresponsive to fluids or pressors, nasuea/vomiting, abdominal pain, fever, lethargy, decreased glucose, hyperkalemia
Tx: Dexamethasone
29
Steroid potency?
1x - cortisone, hydrocortisone
5x - prednisone, prednisolone, methylprednisolone
30x - dexamethasone
30
Neurogenic shock
Loss of sympathetic tone
Associated with spine or head injury
Decreased HR, decreased BP, warm skin
Tx: give volume 1st, phenylephrine after resuscitation
31
Initial alteration in hemorrhagic shock?
Increased diastolic pressure
32
Cardiac tamponade
Causes cardiogenic shock
Decreased ventricular filling
ECHO shows impaired diastolic filling of right atrium first (weakest wall)
Tx: Rescucitation, pericardial window/pericardiocentesis
33
Beck's triad
Hypotension
Jugular venous distention
Muffled heart sounds
34
Decreased CVP/PCWP
Decreased CO
Increased SVR
Hemorrhagic shock
35
Decreased CVP/PCWP
Increased CO
Decreased SVR
Septic shock (hyperdynamic)
36
Increased CVP/PCWP
Decreased CO
Increased SVR
Cardiogenic (i.e. MI, cardiac tamponade)
37
Decreased CVP/PCWP
Decreased CO
Decreased SVR
Neurogenic (i.e. head or spinal cord injury)
| Adrenal insufficiency
38
Early sepsis triad
Hyperventilation
Confusion
Hypotension
39
Early gram-negative sepsis
```
Decreased insulin
Increased glucose (impaired utilization)
```
40
Late gram-negative sepsis
```
Increased insulin
Increased glucose (insulin resistance)
```
41
Neurohormonal response to hypovolemia - Rapid
Epinephrine and norepinephrine release
Adrenergic release
Results in vasoconstriction and increased cardiac activity
42
Neurohormonal response to hypovolemia - Sustained
Renin (from kidney - vasconstriction and water resorption)
ADH (from pituitary - reabsorption of water)
ACTH (from pituitary - increases cortisol)
43
Fat emboli
Petechia, hypoxia, confusion
Sudan red stain may show fat in sputum and urine
Most common from LE fractures, orthopedic procedures
44
Pulmonary emboli
```
Chest pain and dyspnea
Decreased PO2 and PCO2
Respiratory alkalosis
Increased HR and RR
Hypotension and shock if massive
```
Tx: HEparin, coumadine; consider open or percutaneous emboliectomy if in shock despite massive pressors and inotropes
45
Most common source of PEs?
Iliofemoral region
46
Treatment of air emboli?
Patient head down and roll to left (keeps air in RV/RA)
| Aspirate air out with central line to RA/VA
47
When does an intra-aortic balloon pump inflate? Deflate?
Inflates on T wave (diastole)
| Deflates on P wave (systole)
48
CI to intra-aortic balloon pump?
Aortic regurgitation
49
Uses/effect of intra-aortic balloon pump?
Used for cardiogenic shock (after CABG or MI)
Refractory angina awaiting revascularization
Decreases afterload (deflation during ventricular systole)
Improves diastolic BP (inflation during ventricular diastole)
Which improves diastolic coronary perfusion
50
Alpha-1 receptors
Vascular smooth muscle constriction
Gluconeogenesis
Glycogenolysis
51
Alpha-2 receptors
Venous smooth muscle contriction
52
Beta-1 receptors
Myocardial contraction and rate (ionotrope and chronotrope)
53
Beta-2 receptors
Relaxes bronchial smooth muscle
Relaxes vascular smooth muscle
Increases insulin, glucagon, renin
54
Dopamine receptors
Relaxes renal and splanchnic smooth muscle
55
Dopamine (2-5ug/kg/min initially)
2-5ug/kg/min - dopamine receptors (renal)
6-10ug/kg/min - beta-adrenergic (heart contractility)
>10ug/kg/min - alpha-adrenergic (vasoconstriction and increased BP)
56
Dobutamine (3ug/kg/min initially)
Beta-1 receptors
| Increased contractility, tacycardia with higher doses
57
Milrinone
Phosphodiesterase inhibitor - increases cAMP
Results in increased Ca flux and increased myocardial contractility
Vascular smooth muscle relaxation and pulmonary vasodilation
58
Phenylephrine (10ug/kg/min initially)
Alpha-1
| Vasoconstriction
59
Norepinephrine (5ug/min initially)
Low doses - Beta-1 (increased contractility)
| High dose - Alpha-1 and Alpha-2 (veno and vaso constriction)
60
Epinephrine (1-2ug/min initially)
Low dose - Beta-1 and B-2 (increased contractility and vasodilation; can decrease BP at low dose)
High dose - Alpha-1 and Alpha-2 (veno and vaso constriction; can increase cardiac ectopic pacer activity and myocardial O2 demand)
61
Isoproterenol (1-2ug/min initially)
B-2 and B-2 (increased contractility, vasodilates)
| AE: extremely arrhythmogenic, increased heart metabolic demand, may actually decrease BP
62
Vasopressin
```
V1 receptors - vasocontriction of vascular smooth muscle
V2 receptors (intrarenal) - water reabsoprtion at collecting ducts
V2 receptors (extrarenal) - mediate release of factor VII and vWF
```
63
Nipride
Arterial vasodilator
Cyanide toxicity at dose >3ug/kg/min for 72hrs
Check thiocyanate levels and signs of metabolic acidosis
64
Treatment for cyanide toxicity
Amyl nitrate
| Then sodium nitrite
65
Nitroglycerin
Predominately venodilation with decreased myocardial wall tension from decreased preload
Moderate coronary vasodilator
66
Hyrdalazine
a-blocker
| Lower BP
67
Compliance
Change in volume / change in pressure
High compliance means lungs are EASY to ventilate
Decreased: ARDS, fibrotic lung disease, reperfusion injury, pulmonary edema, atelactasis
68
Effect of aging on the lungs?
Decreased FEV1
Decreased vital capacity
Increased functional residual capacity
69
V/Q ratio
Ventilation/perfusion ratio
Highest in upper lobes
Lowest in lower lobes
70
Why does increasing PEEP improve oxygenation?
Increased alveoli recruitment
| Improves FRC
71
How to you decrease CO2?
Increase respiratory rate
| Increase tidal volume
72
Normal weaning parameters?
```
NIF > 20
FiO2 < 40%
PEEP 5
Pressure support 5
RR < 24
HR <120
PO2 > 60mmHg
PCO2 < 50mmHg
pH 7.35-7.45
Saturation >93%
Off pressors
Follows commands
Can protect airway
```
73
Puts you at risk for barotrauma? How do you decrease the risk?
Plateau > 30
Peak > 50
Need to decrease TV
Consider pressure control ventilation
74
Complications of excessive PEEP?
```
Decreased RA filling
Decreased CO
Decrease renal blood flow
Decease urine output
Increase pulmonary vascular resistance
```
75
Total lung capacity
Lung volume after maximal inspiration
| TLC = FRC + RV
76
Forced vital capacity
Maximal exhalation after maximal inhalation
77
Residual volume
Lung volume after maximal expiration (20% TLC)
78
Tidal volume
Volume of air with normal inspiration and expiration
79
Functional residual capacity
Lung volume after normal exhalation
| FRC = ERV + RV
80
What can decrease functional residual capacity?
Surgery (atelectasis)
Sepsis (ARDS)
Trauma (contusion, atelectasis, ARDS)
81
Expiratory reserve volume
Volume of air that can be forcefully expired after normal expiration
82
Inspiratory capacity
Maximum air breathed in from FRC
83
FEV1
Forced expiratory volume in 1 second after maximal inhalation
84
Minute ventilation
MV = TV x RR
85
Decreased TLC
Decreased RV
Decreased FVC
Restrictive lung disease
| FEV1 can be normal or increased
86
Increased TLC
Increased RV
Decreased FEV1
Obstructive lung disease
| FVC can be normal or decreased
87
Dead space
```
Normally to the level of the bronchiole (150mL)
Area of lung that is ventilated but not perfused
Increases with:
- Drop in CO
- PE
- Pulmonary HTN
- ARDS
- Excssive PEEP
```
88
COPD breathing changes
Increased work of breathing due to prolonged expiratory phase
89
ARDS
Mediated by PMNs, increased proteinaceous material, increased A-a gradient, increased pulmonary shunt
Causes: Pnuemonia*, sepsis, multi-trauma, severe burns, pancreatitis, aspiration, DIC
90
Diagnostic criteria for ARDS
Acute onset
Bilateral pulmonary infiltrates
PaO2/FiO2 <300
Absence of heart failure (Wedge <18mmHg)
91
Mendelson's syndrome
Chemical pneumonitis from aspiration of gastric secretions
92
Atelectasis
Collapse of alveoli resulting in reduced oxygenation
Sx: Fever, tachycardia, hypoxia
Tx: IS, pain control, ambulation
93
What can make a pulse-ox inacurate?
Nail polish, dark skin, low-flow state, ambient light, anemia, vital dyes
94
Causes pulmonary vasodilation?
PGE1
Prostacyclin (PGI2)
Nitric oxde
Bradykinin
95
Causes pulmonary vasoconstriction?
HYpoxia
Acidosis
Histamine
Serotonin, TXA2
96
Alkalosis - effect on pulmonary vasculature?
Pulmonary vasodilator
97
Acidosis - effect on pulmonary vasculature?
Pulmonary vasoconstrictor
98
Drugs that cause pulmonary shunting?
Nitroprusside
Nitroglycerin
Nifedipine
99
Most common cause of postoperative renal failure?
Intra-op hypotension
100
Amount of nephron that needs to be damaged before renal dysfunction?
70%
101
FeNa
Fractional excretion of sodium
(Urine Na/Cr) / (plasma Na/Cr)
Best test for azotemia
102
```
Urine Osm >500
U/P osmolality >1.5
U/P creatinine >20
Urine sodium <20
FeNa < 1%
```
Prerenal azotemia
103
```
Urine Osm 250-350
U/P osmolality <1.1
U/P creatinine <10
Urine sodium >40
FeNa > 3%
```
Parenchymal azotemia
104
Treatment of oliguria
Make sure patient is volume loaded (CVP 11-15mmHg)
Try diuretic trial (Lasix)
Dialysis if needed
105
Indications for dialysis
```
Fluid overload
Hyperkalemia
Metabolic acidosis
Uremic encephalopahty
Uremic coagulopathy
Poisoning
```
106
Renin
Released in response to decreased pressure (JGA), increased Na (macula densa) concentration, beta-adrenergic stimulation and hyperkalemia
107
Aldosterone
Acts at distal convoluted tubule to reabsorb water by up-regulating the Na/K ATPase (Na re-absorbed, K secreted)
108
Effect of Angiotensin II
```
Stimulates release of aldosterone
Vasoconstricts
Increases HR
Contractility
Glycogenolysis
Gluconeoenesis
Inhibits renin
```
109
Atrial natriuretic peptide
Released from atrial wall with atrial distention
Inhibits Na and water resoprtion in the collecting ducts
Vasodilator
110
Antidiuretic hormone (ADH, vasopressin)
Released by posterior pituitary gland when osmolality is high
Acts on collecting ducts for water resorption
Vasoconstrictor
111
What controls GFR?
Efferent limb of the kidney
112
Renal toxic drugs
NSAIDs (inhibit PGE - renal arteriole vasoconstriction)
Aminoglycoside (direct tubular injury)
Myoglobin (DTI)
Contrast dye (DTI)
113
Causes of SIRS
```
Shock
Infection
Burn
Multi-trauma
Pancreatitis
Severe inflammatory responses
```
114
What is the most potent stimulus for SIRS?
Endotoxin (lipopolysaccharide - Lipid A)
| Stimulates TNF release
115
Effect of TNF-a and IL-1 release?
SIRs
| Capillary leakage, microvascular thormbi, hypotension, eventually end-organ dysfunction
116
Criteria for SIRS
Temp >38 or < 36
HR >90
RR >20 or PaCO2 <32
WBC >12000 or < 4000
117
Diagnostic criteria: end organ dysfunction.
| Pulmonary
Need for mechanical ventilation
| PaO2:FiO2 ratio <300 for 24hrs
118
Diagnostic criteria: end organ dysfunction.
| Cardiovascular
Need for ionotropic drugs
| CI <2.5 L/min/m2
119
Diagnostic criteria: end organ dysfunction.
| Kidney
Creatinine >2x baseline on 2 consecutive days
| Need for dialysis
120
Diagnostic criteria: end organ dysfunction.
| Liver
Bilirubin >3mg/dL for 2 days
| PT > 1.5
121
Diagnostic criteria: end organ dysfunction.
| Nutrition
10% reduction in lean body mass
albumin 2.0
Total lymphocyte count <1
122
Diagnostic criteria: end organ dysfunction.
| CNS
GCS <10 without sedation
123
Diagnostic criteria: end organ dysfunction.
| Coagulation
Platelet count < 50
Fibrinogen <100
Need for factor replacement
124
Diagnostic criteria: end organ dysfunction.
| Host defenses
WBC < 1000
| Invasive infection including bacteremia
125
What precludes a diagnosis of brain death?
Temp <32
BP <90
Drugs (i.e. phenobarbital, pentobarbital, ETOH)
Metabolic derangemetns (hyperglycemia, uremia)
Desaturation with apnea test
126
What must exist for 6-12 hours to diagnose brain death?
```
Unresponsive to pain
Absent cold caloric oculovestibular reflexes
Absent oculocephalic reflex
No spontaneous respirations
No corneal reflex
No gag reflex
Fixed and dilated pupils
Positive apnea test
```
Still have deep tendon relfexes with brain death
127
Apnea test
Patient is pre-oxygenated, catheter delivering O2 at 8L/min is placed at the carina through the ET-tube and CO2 should be normal before the start of the test
- Disconnect from vent for 10 minutes
- CO2 > 60mmHg or increase in CO2 by 20 is POSITIVE for apena
128
What is a negative result for an apnea test?
```
BP drops (<90mmHg)
Patient desaturates (<85%)
Spontaneous breathing
```
129
Carbon monoxide
Can increase O2 sats on pulse-ox
Carboxyhemoglobin - HA, nausea, confusion, coma, death (<10% in normal, <20% in smokers)
Corrects with 100% O2
130
Methemoglobinemia
From nitrates
O2 sat reads 85%
Tx: methylene blue
131
Critical illness polyneuropathy
Motor > sensory neuropathy
Occurs with sepsis
Causes failure to wean from ventilation
132
Xanthine oxidase
Is in endothelial cells
Forms toxic oxygen radicals with reperfusion
Also involved in metabolism of purines to uric acid
133
DKA
Nausea/vomiting, thirst, polyruia, increased glucose, increased ketones, decreased sodium, increased potassium
TX: normal saline and insulin
134
ETOH withdrawal
HTN, tachycardia, delirium, seizures (After 48hrs)
| Tx: Thiamine, folate, B12, Mg, K, PRN lorazepam
135
ICU psychosis
```
Third POD day - preceded by lucid interval
Address metabolic (hypoglycemia, DKA< hypoxia, hypercarbia, electrolyte imbalances) and organic (MI, CVA) causes
```
