Critical Care

Question 1

What determine tissue perfusion?

Answer 1

1) CO = SV x HR
2) SV = Preload x contractility
2) SVR = (MAP - CVP)/CO
3) BP = CO x SVR

Question 2

Hypovolemic shock

Answer 2

Reduced venous return, pump is working

Low preload. Low CO

Bleeding, vomiting/diarrhea, and third spacing (burns, bowel obstruction, pancreatitis)

Tachy, ortho hypo, cool skin

Will become hypotensive, low pulse pressure, confused, cold clammy skin due to clamping down of peripheral vessels via increased sympathetic tone

in trauma, assume shock is hypovolemic until proven otherwise

Question 3

First vital organ to succumb to shock?

Answer 3

kidney - in hypovolemic or cardiogenic ( the cold shocks)

Blood shunted away from constricted renal arteries

CRUCIAL to monitor for renal failure. A good urine output is a great sign that treatment is working

Question 4

What factors suppress the tachycardic response in hypovolemia?

Answer 4

Beta blockers

Athletes

Damage to autonomic nervous system (spinal shock)

Never use dextrose-containing solution for resuscitation

Question 5

SIRS criteria

Answer 5

2+ of following:

Temp > 38C or 90
RR > 20 or PaCO2 12 or 10% bands

Question 6

Sepsis

Answer 6

Identifiable source of infection + SIRS

Question 7

Severe sepsis

Answer 7

Sepsis + organ dysfunction

Question 8

Septic shock

Answer 8

Sepsis + cardiovascular collapse (requiring vasopressor support)

Question 9

What kind of bacteria are notorious for causing septic shock?

Answer 9

gram-negative bacteria

E Coli
Kleb
Pseudomonas

Top 3 gram positives are:
Staph aureus
Enterococcus
Coag-neg staph

Question 10

HR issues leading to shock

Answer 10

too slow

too fast (not enough time to fill)

Question 11

Preload issues leading to shock

Answer 11

More blood into heart = more blood out

Volume down
Hemorrhage
Obstruction (tension pneumo, pericardial tamp)

Question 12

Contractility issues leading to shock

Answer 12

HF

MI or myocardial contusion

Question 13

SVR and shock

Answer 13

Massive vasodilation - sepsis/anaphylaxis

Spinal trauma (ANS is lost)

Anesthetics

ANS dysfunction (elderly diabetic)

Question 14

Neurogenic shock

Answer 14

CNS injury causing disruption of sympathetic system, resulting in unopposed vagal outflow and vasodilation.

Hypotension and bradycardia (absence of reflex sympathetic tachy and vasoconstriction)

Usually secondary to spinal cord injury of cervical or high thoracic region

Tx = IVFs - helps to place patient in trendelenburg

Vasopressors - used early if patient unresponsive to fluids

Question 15

End points of resuscitation for shock of any etiology

Answer 15

Normalization of lactate (marker of O2 debt), base deficit, pH

Normalization of mixed venous O2 sat (marker of O2 delivery and extraction) and CO

Urine output (marker of renal perfusion)***

Question 16

Swan Ganz

Answer 16

Measure PCWP (preload) - normal 6-12 - reflecting pressure in LV

If pump is failing, you’ll see increased wedge

Risks = infection, arrhythmia, injury of pulmonary artery

Question 17

Mixed venous O2 sat

Answer 17

% of O2 bound to hemoglobin in blood returning to heart

It’s the amount of O2 left over after tissues remove what they need

Normal = 60-80%

Low = CO isn’t high enough to meet tissue O2 needs

BUT

Rise in setting of increased lactate means we’re going to anaerobic (late septic shock or in cell poisoning)

Question 18

Side effects of pressors

Answer 18

If B1 stimulation - arrhythmia

If B2 stimulation - vasodilation therefore hypotension

Question 19

The alpha agonists

Answer 19

Phenylephrine, methoxamine (a1 > a2)

Clonidine, methylnorepinephrine (a2 > a1)

Question 20

The mixed alpha and beta agonists

Answer 20

Norepi a1=a2; B1> B2

Epi a1=a2; B1=B2

Question 21

Beta agonists

Answer 21

Dobutamine B1 > B2

Isoproterenol B1 = B2

Terbutaline, metaproterenol, albuterol, ritodrine B2 > B1

Question 22

Dopamine agonists

Answer 22

Dopamine D1 = D2

Fenoldopam D1 > D2

Question 23

Dobutamine

Answer 23

Strong B1 stimulator (ionotropic/chronotropic) wit mild B2 stimulation (vasodilation)

Causes increase in CO and decrease in SVR

Usually used in: Cardiogenic shock

Question 24

Isoproterenol

Answer 24

Similar to dobutamine

Strong stim of B1 (ionotropic/chronotropic) and B2 (vasodilation)

Increased CO and decreased SVR

Use: Cardiogenic shock with bradycardia

Question 25

Milrinone

Answer 25

Phosphodiesterase inhibitor, which results in increased cAMP. This has positive ionotropic effects on heart and also vasodilates Increased CO and decreased SVR Use: HF/Cardio shock

Question 26

Dopamine

Answer 26

Different actions depending on dose 1) Low dose (1-3ug/kg/min) = renal dose. Stimulates dopamine recepters (dilates renal vessels) and mild B1 stim Use: None 2) Intermed dose (5-10) = cardiac dose. Stimulation of dopamine receptors, moderate stim of B1 (heart ionotropy/chrono) and mild a2 (vasoconstriction) ``` Result = Increased CO Use = cardiogenic shock ``` 3) High dose (10-20). Stim D, B1, and strong a1 (vasoconstict) ``` Result = Big increase in SVR Use = septic shock (replaced by norepi) ```

Question 27

Norepinephrine

Answer 27

Strong stim of a1 (vasoconstrict), moderate B1 (heart ionotrope/chrono) Result: higher SVR and higher CO Use = septic shock

Question 28

Epinephrine

Answer 28

Strong stim of B1 and B2. Also A1 and A2 Result = Increased SVR +/- Increased CO, bronchodilation Use = Anaphylaxis, septic shock, cardiopulmonary arrest

Question 29

Phenylephrine

Answer 29

Strong stim of A1 (vasoconstrict) Result = Increased SVR Use = septic shock, neurogenic shock, anesthesia-induced hypotension

Question 30

Indications for intubation

Answer 30

Airway protection (GCS

Question 31

Complications of mechanical ventilation

Answer 31

Ventilator-associated pneumonia Barotrauma and tension pneumo Decreased venous return (preload) and CO

Question 32

Ventilator settings

Answer 32

Must define mode (AC, IMV, PS, CPAP) RR (10-20) TV (for AC or IMV only) - usually 400-600cc (6-8cc/kg) FiO2 - always start at 100% and go down. Maintain the pulse ox >90%. Keep FiO2 below 60% to minimize oxygen-induced free radical injury

Question 33

What are some strategies to improve oxygenation on a vent?

Answer 33

Increase FiO2 Increase PEEP

Question 34

What happens when you change minute vent?

Answer 34

Increased minute vent: lowers PCO2 and increases pH PCO2 is marker of ventilation PO2 is marker of oxygenation

Question 35

Causes of failure to wean off vent

Answer 35

1) Anxiety/agitation 2) Drugs (sedatives) 3) lytes (low phosphate) 4) Diaphragm dysfunction (neuromuscular dysfunction) 5) Hypothyroidism/malnutrition 6) Excess CO2 production (overfeeding)

Question 36

What is a potential problem of PEEP?

Answer 36

Hypotension | Decreases preload

Question 37

CPAP

Answer 37

Noninvasive vent that applies constant positive pressure with no variation in breathing cycle Keeps inspiratory airway pressure above atmospheric w/o increasing work of breathing Patient must breathe on own Can be used to help avoid intubation. Mode of choice for OSA

Question 38

Synchronized Intermittent Mandatory Ventilation

Answer 38

Patient breathes on own, plus receives a preset rate of MV synchronized to and delivered with patient's breath. Pressure support is often added to spontaneous breathing (gives Pt initial boost of pressure to overcome airway resistance)

Question 39

Assist-control

Answer 39

Each breath initiated by the patient triggers machine to deliver set tidal volume (volume control) or set peak inspiratory pressure (pressure control) A set volume/pressure is given a set number of times per minute even if patient is breathing less than the preset rate

Question 40

Pressure support

Answer 40

Each breath started by patient triggers machine to deliver an initial boost of pressure with variable flow of air into lungs. Patient determines rate, duration of inspiration and tidal volume Good mode for weaning

Question 41

Causes of ARDS

Answer 41

1) Direct lung injury - pneumonia - aspiration - near drowning 2) Indirect - Sepsis (#1 of all causes) - Massive transfusion - severe trauma, burns, toxins - pancreatitis

Question 42

Diagnostic criteria for ARDS

Answer 42

1) Bilateral fluffy infiltrates on CXR (3 out of 4 lung fields) 2) PaO2/FiO2 ratio

Question 43

ARDS

Answer 43

Acute lung injury due to inflammatory process in both lungs causing increased permeability of capillaries and severe V/Q mismatch. Disease of altered lung compliance Tachypneic and hypoxic with b/l crackles on exam

Question 44

Management of ARDS

Answer 44

Intubate Treat underlying cause, esp infections Low tidal volume ventilation (6-8cc/kg) PEEP often used to improve gas exchange and keep lungs open at relatively low volumes FiO2 kept at less than 60% to avoid free radical injury