Shock

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Shock
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Outline

1. Definition of Shock
2. Signs and Symptoms of Shock
3. Categorization of Shock
4. The PA Catheter
5. Replacement Fluids
6. Vasopressors and Inotropes
7. Example Cases

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What is Shock?

• Shock is a physiologic state characterized by a
  systemic impairment in oxygen delivery as a
  result of reduced tissue perfusion, almost
  universally mediated by low blood pressure.

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What is Shock?

• The general physiologic mechanisms of how shock
  leads to irreversible cell damage and death
  include
• Cell membrane ion pump dysfunction
• Intracellular edema
• Leakage of intracellular contents into the
  extracellular space
• Inadequate regulation of intracellular pH

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Signs/Symptoms of Shock

• Cardiovascular Hypotension
• Nervous Agitation ? Delirium ? Coma
• Pulmonary Tachypnea hypoxia
• Epidermal Cool, clammy skin peripheral
  cyanosis
• Kidneys Oliguria increased BUN/Cr ratio
• GI Ileus, hemorrhage hepatic dysfunction
• Hematologic Coagulopathy ? DIC
• Diffuse Cellular Injury Lactic acidosis

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Physiologic Description of Shock
Pressure Gradient Flow x Resistance (i.e. Ohms
Law ? VIR)

• Perfusion Pressure MAP CVP
• Perfusion Pressure CO x SVR
• Perfusion Pressure HR x SV x SVR
• SV is dependent upon preload, afterload, and
  myocardial contractility

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Categories of Shock

• Hypovolemic

Decreased Preload (from an extracardiopulmonary
process) Decreased SVR Decreased
Contractility Decreased Preload (from an
intracardiopulmonary process)
Distributive Cardiogenic Obstructive
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Etiologies of Shock

• Cardiogenic
• MI
• Heart failure
• Myocarditis
• Arrhythmias
• Paplillary muscle rupture
• Acute AI
• Obstructive
• Massive PE
• Tension pneumothorax
• Cardiac tamponade

• Hypovolemic
• Loss of blood volume
• Loss of plasma volume
• Distributive
• SIRS / Sepsis
• Anaphylaxis
• Myxedema Coma
• Neurogenic Shock

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The Pulmonary Artery (PA) Catheter
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The PA Catheter

• The PA catheter allows measurement of 3 types of
  data
• 1. Central venous, pulmonary artery, and
  pulmonary capillary occlusion (or wedge)
  pressures
• 2. Cardiac output and vascular resistence
• 3. Sampling of mixed venous blood
• Situations in which PA catheters are most
  helpful
• 1. Guiding the management of severe CHF
• 2. Estimating fluid status in non-cardiogenic
  pulmonary edema
• 3. Diagnosing pulmonary hypertension
• 4. Diagnosing right heart infarction

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The PA Catheter

• As the catheter is floated from either the
  internal jugular or subclavian veins, and
  advanced from the RA to the RV, and from the RV
  to the PA, a number of specific pressure
  waveforms should be observed.

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The PA Catheter

• Right Atrium

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The PA Catheter

• Right Ventricle

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The PA Catheter

• Pulmonary Artery

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The PA Catheter

• Pulmonary Capillary Wedge Pressure (PCWP)

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Replacement Fluids

• IV replacement fluids can be divided into two
  categories based on whether they do or do not
  have a tendency to stay intravascular
• Crystalloid Normal saline, lactated Ringers,
  D5W
• Colloid Fresh frozen plasma, albumin

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Replacement Fluids

• Although there are theoretical reasons to favor
  colloids over crystalloids for volume
  resuscitation in patients with shock, no data to
  date has shown any significant outcome
  difference.
• Therefore, crystalloid is almost always the
  preferred choice, given its decreased cost and
  decreased risk.

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Vasopressors and Inotropes

• Vasopressors Act to increase SVR, and
  subsequently increase BP.
• Inotropes Act to increase CO. BP may either be
  increased or decreased.

Together, vasopressors and inotropes are
colloquially known as pressors.
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Vasopressors and Inotropes

• A given drug may have an effect on multiple
  receptors, and which receptors it interacts with
  may be dose dependent.
• Hypovolemia must be corrected prior to the
  institution of vasopressor therapy. Therefore,
  pressors are generally not helpful in hypovolemic
  shock.
• A given agent may affect systemic blood pressure
  through both direct actions, as well as indirect
  reflex actions.

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Vasopressors and Inotropes
Drug Alpha-1 Beta-1 Beta-2 Dopa. Effect on SVR Effect on HR Effect on contractility Typical Dose
Phenylephrine 0 0 0 ?? ? / ? ? 20-200 µg/min
Vasopressin (mechanism of action poorly understood) 0 0 0 0 ?? ? ? 0.01-0.04 U/min
Norepinephrine 0 0 ?? ? ? 0.5-20 µg/min
Epinephrine 0 ? (low dose) ? / ? (high dose) ? ? 2-10 µg/min
Dopamine 0.5 2 5 10 10 20 (µg/kg/min) 0 0 0 0 ? ? ?? ? ? ? ? ? ? 1-20 µg/kg/min
Dobutamine 0 / 0 ? ? ? / ? 2.5-20 µg/kg/min
Isoproternol 0 0 ? ? ? 1-10 µg/min
Milrinone (acts as a phosphodiest- erase inhibitor) 0 0 0 0 ? ? ?? Load 50 µg/kg over 10 min Maintenance 0.375 0.75 µg/kg/min
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Vasopressors and Inotropes(Generalized Summary)

• Phenylepherine
• Norepinepherine
• Epinepherine
• Dopamine
• Dobutamine
• Milrinone

? SVR No effect on contractility ?
SVR ? Contractility
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Case 1

• A 35 year old construction worker is brought in
  to the ER following a 20-30 foot fall off a
  ladder. His past medical history is unknown. On
  exam, his vitals are HR120, BP82/45, and RR8.
  He is on a backboard and in a cervical collar.
  He withdraws from painful stimuli, but is
  otherwise non-responsive. Upon a quick
  superficial examination, he has an obvious
  fracture of his right femur and numerous mild
  lacerations.

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Case 2

• A 68 year old woman is brought to the ER by
  ambulance after developing severe shortness of
  breath 30 minutes ago. Although her symptoms
  were initially only respiratory in nature, upon
  arriving in the ER she is now complaining of
  lightheadedness and nausea. Vitals are as
  follows HR95, BP84/36, RR32, O2 sat89 on
  2L, temperature36.5. Exam is otherwise
  significant for loud bilateral crackles, an S3.
  She is mildly agitated, but otherwise has a
  grossly intact neurologic exam.

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Case 3

• A 76 year old nursing home patient is brought to
  the ER by ambulance after becoming progressively
  incoherent over the preceding 24 hours. His past
  medical history is unavailable. On exam, his
  vitals are HR127, BP78/45, RR24, O2 sat 97
  on RA, temp34.7. He is acutely ill-appearing,
  cachectic, and non-responsive. His neurologic
  exam is non-focal. Aside from the vital sign
  abnormalities, his cardiac and respiratory exams
  are unremarkable.

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Case 4

• As the on-call intern, you are called on a
  cross-cover patient on another service for low
  blood pressure and shortness of breath. All you
  initially know about the patient is that they are
  a 64 year old man who was admitted for an
  uncomplicated NSTEMI 4 days ago, who was supposed
  to be discharged to home tomorrow. The patient
  had been feeling fine all day until 10 minutes
  ago when he very acutely developed shortness of
  breath. He is now complaining of lightheadedness
  and is developing a visibly waning level of
  consciousness.
• Vitals now HR130, BP 82/64, RR28, O2
  sat94 on 2L.
• Vitals 5hrs ago HR84, BP 134/70, RR20, O2
  sat99 on 2L.

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Case 5

• You are on-call in the ICU, and are paged in the
  middle of the night regarding a patient 3 days
  post-op from a CABG that had been complicated by
  a intraoperative cardiac arrest from ventricular
  fibrillation. He continues to be on pressors and
  is intubated, due to concerns regarding
  hemodynamic instability in the immediate post-op
  period, which continues to be incompletely
  explained. His nurse has noted that his blood
  pressure has been trending downward over the past
  6 hours, requiring progressively higher doses of
  dopamine to maintain mean arterial pressures
  (MAP) of 60mmHg. His exam is notable for a 2/6
  systolic murmur over the right upper sternal
  border, and coarse crackles at the left lung
  base. As you have never examined him before, you
  have no idea if these findings are old or new.
  His CXR from the previous morning was notable
  only for mild pulmonary edema, that you remember
  the team did not seem particularly worried about.

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Case 5(continued)
Time HR MAP CO (L/min) SVR (dynes/sec/cm5) Dopa (µg/kg/min) Dobut (µg/kg/min) Epi (µg/min)
12pm 90 72 3.5 1460 5 4 2
8pm 105 68 3.8 1260 5 4 2
10pm 113 64 4.2 1100 6 4 2
12am 118 58 4,9 865 8 4 2
2am 123 56 6.1 670 12 4 2