Ch 6 - Shock Flashcards

1
Q

List and briefly describe the 4 main types of shock

A
  • Hypovolaemic - Reduction in curculating intravascular volume
  • Cardiogenic - Inability of heart to propel blood through circulation. Includes obstructive shock by decreasing to preload
  • Distributive - Maldistribution of vascular volume and massive vasodilation resulting in relative hypovolaemia. Sepsis and SIRS, anaphylaxis, drugs, severe CNS damage
  • Hypoxic - Adequate perfusion but inadequate arterial oxygen content or cellular oxygen utilisation
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2
Q

What are the basic factors determining oxygen delivery?

A
  • Cardiac output
  • Arterial oxygen content
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3
Q

What is the Frank-Starling mechanism?

A

In an intact heart, an increase in end-diastolic volume (pre-load) augments the strength of cardiac contractions

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4
Q

What factors influence the affinity of Hb for Oxygen

A

pH, temperature, 2,3-DPG, CO2

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5
Q

List the ALTS (Advanced Trauma Life Support) classed of haemorrhage

A
  • Class 1 - loss of up to 15% blood volume. Clinical signs absent or mild
  • Class 2 - Loss 15-30%. Tachycardia, tachypnoea, weak pulses
  • Class 3 - Loss 30-40%. mms pale, CRT prolonged, arterial hypotension
  • Class 4 - Loss of >40%. Severe and immediately life-threatening. Cold extremities, altered mentation, profound hypotension
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6
Q

List the possible defect of oxygen uptake in which the central venous oxygen saturation can be normal but tissue oxygenation can be impaired

A
  • Diffussional shunting - slow blood velocity cause diffusion of oxygen from arterial into venous blood instead of into the tissues
  • Diffusional resistance - Tissue oedema increases diffusion distance and limits oxygen availability
  • AV shunting - Loss of capillary bloodflow due to SIRS/sepsis, thrombi etc
  • Perfusion/metabolic mismatch - increased metabolic oxygen demands
  • Cytopathic hypoxia - mitochondrial dysfunction such as in sepsis
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7
Q

What is the normal resting oxygen extraction ratio?

A

20%

Can increase to 60-70% in cases of increased metabolic demand or decreased oxygen delivery

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8
Q

What are the three main hypotheses to explain acute coagulopathy of trauma?

A
  • A fibrinolytic variant fo DIC
  • Enhance thrombomodulin-thrombin protein C pathway (decreased thrombin degradation and increased activation of anticoagulant and profibrinolytic protein C)
  • Neurohumoral response (Catecholamine induced glycocalyx damage and expression of prothrombotic phenotype. Counterregulatory increase in anticoagulants and fibrinolytics leads to systemic anticoagulation and hyperfibrinolysis
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9
Q

What are considered the shock organs in the dog and cat?

A

dog - GIT
cat - Lungs

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10
Q

Over what MAP ranges will perfusion be maintained to the kidneys, myocardium and the brain?

A

Kidneys - 70-130mmHg
Myocardium - 60-140mmHg
Brain - 50-180mmHg

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11
Q

What is the recommended blood pressure cuff width?

A

40% limb circumference in dogs, 30-40% in cats

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12
Q

What is considered physiologic central venous pressure for dogs and cats?

A

0-5cmH20

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13
Q

What is a Swan-Ganz catheter?

A

A pulmonary artery catheter for the measurement of cardiac output

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14
Q

What factors effect lactate measurement?

A
  • Liver and kidney clearance can cause normal lactate in hypoperfusion
  • Severe hepatic failure can cause hyperlactataemia with normal production
  • Inadequate collection and handling
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15
Q

What are the 2 types of lactic acidosis?

A
  • Type A - inadequate oxygen delivery
  • Type B - mitochondrial dysfuntion with normal oxygen delivery (sepsis, DM, neoplasia, drugs, toxins)

Prolonged hypoxia can lead to mitochondrial damage leading to complex (Type A and B) lactic acidosis

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16
Q

List some methods of evaluating regional perfusion

A
  • Rectal temperature
  • Gastric tonometry
  • Sublingual capnometry
  • Near-infrared spectroscopy
17
Q

What is considered normal Pa02 on room air? With supplemental O2?

A

Normal PaO2 >90mmHg on room air
When supplemental O2, Pa02 should be 5x the % of FiO2 (PaO2/FiO2 ratio should be approx 500)