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MBBS IV - Junior Clerkship WCS > JC 11 (Surgery) - Shock > Flashcards

JC 11 (Surgery) - Shock Flashcards

1
Q

Define Shock

A

state of cellular and tissue hypoxia due to reduced O2 delivery, increased O2 consumption or inadequate O2 utilization

inadequate oxygen delivery (DO2) to meet cellular metabolic demands

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2
Q

3 methods to assess for tissue hypoperfusion clinically

A

o Skin: Decreased capillary refill/ Cool and pale skin
o Renal: Decreased urine output < 0.5 mL/kg/hr
o CNS: Anxiety/ Lethargy/ Confusion

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3
Q

Equations for oxygen delivery and oxygen content

A

□ Oxygen delivery (DO2) = CO × CaO2

□ Oxygen content (CaO2) = Hb × SaO2 × 1.34 + PaO2 × 0.027

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4
Q

Hypotension is a pre-requisite to shock
True or False, explain

A

Circulatory failure may not present as occult hypotension

o Patients in the early stages of shock can be normotensive or hypertensive
o Patients who have hypotension does NOT necessarily have shock:
chronic hypotension, drug-induced hypotension, autonomic dysfunction, vasovagal syncope and peripheral artery disease

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5
Q

Define absolute, relative and orthostatic hypotension

A
  • Absolute = SBP < 90 mmHg (OR) MAP < 65 mmHg
  • Relative = Reduction in SBP > 40 mmHg from baseline
  • Orthostatic = Reduction in SBP > 20 mmHg (OR) DBP > 10 mmHg on standing
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6
Q

Stages of shock

A

□ Pre-shock: compensated shock to tissue hypoperfusion
→ tachycardia, modest increase BP, low urine output, mild lactate

□ Shock: compensatory changes overwhelmed
→ Low BP and S/S of tissue hypoperfusion, eg. oliguria, cold and clammy skin

□ End-organ dysfunction: multiorgan failure and death
→ acute renal failure, severe hypotension, mental obtundation and coma

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7
Q

4 severities of hypovolemic shock and associated volume blood loss

A
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8
Q

Compare the HR, BP and RR response in 4 severities of shock

A
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9
Q

List all assessments for severity of shock

A
  1. Volume of blood loss
  2. HR
  3. BP
  4. RR
  5. Mental status
  6. Capillary refill
  7. Bowel sounds
  8. Urine output
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10
Q

Compare the Mental status between 4 severities of shock

A
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11
Q

Compare capillary refill time, bowel sounds and urine output for 4 severities of shock

A
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12
Q

4 classes of shock

A

Hypovolemic

Cardiogenic

Obstructive

Distributive: Sepsis, anaphylaxis, Neurogenic

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13
Q

Causes of hypovolemic shock

A

Causes:

haemorrhagic

  • trauma, GI bleed

non-haemorrhagic

  • excessive vomiting and diarrhea,
  • skin burns,
  • 3rd space loss,
  • dehydration
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14
Q

Causes of cardiogenic shock

A

Causes:

  1. cardiomyopathic (eg. MI, severe dilated cardiomyopathy, myocarditis),
  2. arrhythmogenic,
  3. mechanical (eg. severe valvular heart disease, ruptured LV aneurysm, atrial myxoma)
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15
Q

Causes of obstructive shock

A

 Cardiac tamponade
 Pulmonary embolism
 Tension pneumothorax

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16
Q

Causes of distributive shock

A

Sepsis

Anaphylaxis: severe systemic allergic reaction to an antigen precipitated by abrupt release of chemical mediators in a previously sensitized patient

Neurogenic: traumatic brain injury or spinal cord injury, Interruption of autonomic pathways leading to loss of sympathetic tone and unopposed vagal tone

17
Q

Compare anaphylaxis reaction to anaphylactoid reaction

A

Anaphylaxis refers severe systemic allergic reaction to an antigen precipitated by abrupt release of chemical mediators in a previously sensitized patient

Anaphylactoid reaction refers to direct histamine release from mast cells without need for prior sensitization

18
Q

Common causes of anaphylactic shock

A

Common causes for anaphylactic shock
o Drugs: Penicillin/ Aspirin/ NSAIDs/ Colloids/ TCM
o Food: Peanuts/ Egg/ Shellfish
o Venoms: Bees/ Wasp/ Hornets
o Environment: Latex/ Dust/ Pollen grains
o Infections: EBV/ HBV/ Coxsackie virus/ Parasites

19
Q

Pathophysiology of hypovolemic shock

A

Pathophysiology - Intravascular blood volume depletion
↓ Preload (e.g. due to blood loss)
↓ SV (Frank-Starling curve: Decrease preload = Decrease stroke volume)
↓ CO, BP and LV filling pressure
↑ Sympathetic compensation to increase HR and Total Peripheral resistance

>> Increase HR

>> Increase Systemic vascular resistance

>> Decrease JVP

20
Q

Pathophysiology of cardiogenic shock

A

Pathophysiology
↓ Blood flow to heart due to intrinsic cardiac function deficit
↓ Contractility
↓ SV + Increase LV filling pressure (Backward failure - pulmonary edema)
↓ CO
↑ Sympathetic compensation to increase HR and Total Peripheral resistance

Increase HR, Systemic vascular resistance, JVP

21
Q

Pathophysiology of obstructive shock

Triad of symptoms

A

Mechanical obstruction to cardiac filling > Low LV filling > ↓CO and BP + Backward failure of right heart (Increase JVP)

Beck’s triad of cardiac tamponade
• Hypotension (Low BP)
• Distended neck veins (High CVP)
• Muffled heart sounds

22
Q

Pathophysiology of Distributive shock

A

Peripheral vascular dilatation > Increase CO (opposite to hypovolemic and cardiogenic shock), but perfusion of vital organ remains compromised as the body lose ability to distribute blood properly

  1. Hypotension with wide BP (↓DBP due to peripheral vasodilatation)
  2. Compensatory tachycardia and tachypnoea
  3. Warm peripheries
  4. Bounding peripheral pulses
  5. Features of hypoperfusion
     Hyperlactataemia and lactic acidosis
     Oliguria
     Mental status changes

>> Increase HR (except neurogenic shock with low HR)

>> Decrease systemic vascular resistance

>> Decrease JVP

23
Q

Pathophysiology of Neurogenic shock

A

Neurogenic shock
Due to interruption of neurogenic vasomotor control → inappropriate ↓HR, ↓SVR

>> Paradoxically slow HR due to loss of SN control
>> Decrease systemic vascular resistance

>> Decrease JVP

24
Q

Features of anaphylactic shock

A

Due to severe type I hypersensitivity reaction

Anaphylactic S/S
□ Severe bronchospasm and angioedema
□ Urticaria, widespread flushing and pruritus

25
Q

Airway protective measures

A

→ Airway management measures as required: Head-tilt, chin lift, jaw thrust (for suspected C-spine injury), remove foreign bodies…etc
→ Rapid sequence intubation

26
Q

Breathing protective measures

A

→ High flow O2 (15L/min) using face-mask and reservoir for ALL pt

→ Mechanical ventilation if intractable hypoxaemia/hypercapnia, resp distress or ↓consciousness

27
Q

Circulation protective measures

  1. Hypovolemia (2)
  2. Cardiogenic (3)
  3. Distributive (3))
A

Hypovolemia:

  • Optimize preload by volume resuscitation ± short-term vasopressors (adrenaline, noradrenaline)
  • Secure large-bore IV access (14-18G)

Cardiogenic

  • Optimize afterload by vasodilators and intra-aortic balloon pump (IABP)
  • Optimize contractility by inotrope (dobutamine) or antiarrhythmics (if in arrhythmia)
  • Optimize Hb by RBC transfusion to keep Hb 7-9mg/dL

Distributive

  • As above
    • Optimize MABP by vasopressors
    • eradicate infective focus
28
Q

First-line monitoring for suspected shock

A

Clinical evaluation for type of shock and aetiology

Clinical monitoring: BP/P, UO, fluid balance charts, cardiac monitor

29
Q

First-line tests/ investigations for suspected shock with rationale (7)

A

Cardiogenic: ECG, Cardiac enzymes/BNP

CBC/D: anaemia w/ bleeding (haemorrhagic shock), ↑eosinophil (anaphylaxis), ↑/↓WBC (sepsis or stress response), ↓PLT (bleeding tendency)

L/RFT: ↑U/Cr (shock-induced AKI), ↑ALT/AST (shock liver), electrolyte disturbance, dehydration (hypovolemia)

V/ABG + lactate: lactic acidosis (poor tissue perfusion), assess need for ventilation

Clotting + D-dimer: ↑PT/INR (haemorrhagic shock, septic APR), ↑D-dimer (PE, DIC)

  • *CXR:** pneumonia, pneumothorax, pulmonary oedema, widened mediastinum (obstructive
    shock) , aortic dissection…
30
Q

Acute management of Cardiac arrest

A
  1. CPR with 30:2 compression -ventilation ratio
  2. Shock for Ventricular defibrillation
  3. Adrenaline (or amiodarone/ Lidocaine for refractory)
  4. Airway: ET tube or supraglottic advanced airway
  5. Monitor return of spontaneous circulation: Pulse, BP, ECG
31
Q

Acute assessment of hypovolemia

A

Straight leg raise if unsure of hypovolemic shock

  • If BP goes up > hypovolemic shock

Fluid challenge: 100-500mL of fluid infusion to see If BP goes up

32
Q

Acronym for causes of traumatic cardiac arrest

A

HOTT

Hypovolemia

Oxygen

Tension pneumothroax

Tamponade

MBBS IV - Junior Clerkship WCS (131 decks)

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