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Medical Studies 1 > Module 4 > Flashcards

Module 4 Flashcards

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USMLE® Step 1 flashcards
1
Q

What is shock?

A

A generalised state of hypotension or the inability of the circulation to adequately perfuse the tissues of the body. Shock is a cascade of events due to decreased perfusion.

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2
Q

What is perfusion?

A

Adequate supply of oxygen and nutrients to the cells.

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3
Q

What is hypoperfusion?

A

Any malfunction that causes a decrease in cellular oxygen.

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4
Q

What is needed for adequate perfusion?

A
  • Heart: Sufficiently pumps fluid
  • Blood Vessels: Maintains integrity and enables blood flow
  • Lungs: Adequately on/off loads oxygen
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5
Q

What is cardiac output and how do you calculate it? Additionally what variables need to be considered?

A

The amount of blood pumped out by the ventricles in one minute.
Cardiac output = Heart Rate x Stroke Volume*
*Stroke volume is the amount the ventricles in one contraction. The healthy average adult is 70ml.
Variables to be considered are Strength and rate of the contraction and the volume of venous return to the ventricles (pre-load).

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6
Q

What is starling’s law?

A

The greater the preload, the greater the stretch on the heart, and therefore the greater the strength of the contracts.

^ Preload = ^ Stretch on heart = ^ strength of contractions

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7
Q

Define Preload.

A

The amount of blood returning to the ventricles; it’s the end diastolic volume (EDV).

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8
Q

Define Afterload.

A

is the amount of pressure that the heart needs to exert to eject the blood during ventricular contraction.

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9
Q

What is mean arterial pressure and how do you calculate it?

A

The mean value of the blood pressure in the arterial portion of the circulation.
Diastolic BP x2 + Systolic ÷ 3 = mean arterial pressure

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10
Q

How do you calculate pulse pressure?

A

Systolic BP – diastolic PB

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11
Q

Why is mean arterial pressure an important consideration for paramedics?

A

Cerebral perfusion in head/brain trauma

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12
Q

Why do patients in the early stages of shock have pale, sweaty skin, and a rapid, thready pulse?

A

Lack of perfusion to extremities due to sphincteral contractions redistributing blood to vital organs. Rapid pulse is due to stroke volume dropping.

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13
Q

What is DIC and what causes this condition?

A

Disseminated intravascular coagulation – cause by stagnant blood in the capillary bed

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14
Q

What are Rouleaux formations?

A

When stagnant the erythrocytes become sticky and stick together causing obstruction of capillaries. This decreases tissue perfusion, resulting in cell necrosis.

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15
Q

What causes organ failure in Shock?

A

Obstructed capillaries leading to micro-infarct within the organs.

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16
Q

What are the three broad categories/stages of shock?

A

Compensated shock: there is some decreased blood flow and perfusion to tissues. Initial signs and symptoms increase pulse, BP, RR, HR, pale cool clammy, GCS – normal but potentially agitated or confused.
*children stay in this phase longer than adults however they crash into irreversible sock much quicker than adults
Decompensated shock: compensatory mechanisms fail and SBP can no longer be maintained. Falling BP, tachycardia, pale clammy cold, altered conscious stage.
Irreversible shock: there is cellular ischemia and necrosis and subsequent organ failure.

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17
Q

Give three signs or symptoms of irreversible shock.

A
  1. Bradycardia
  2. Hypotension
  3. Significantly altered conscious state <8 GCS
  4. Peaked T wave, significant arrythmia on ECG
  5. Cyanosis
  6. > 2 cap refill
  7. Cold skin
18
Q

Rouleaux formations and capillary obstruction occur in which stage of shock?

A

Decompensating

19
Q

Give signs and symptoms for the following systems in relation to compensated shock: CNS (GCS), Skin & Cardiac

A

CNS: GCS near to normal 13/14
Skin: Pale and sweaty
Cardiac: Increased HR and BP

20
Q

What are the 5 Classifications of shock?

A
  • Hypovolemic Shock: loss of circulating volume
  • Cardiogenic Shock: pump is failing
  • Neurogenic Shock: neurogenic signals interrupted due to head or spinal trauma.
  • Anaphylactic Shock: hyperreaction of the immune system to allergen
  • Septic shock: presence of bacteria/infection in the blood stream causing
21
Q

What is hypovolemic shock and examples of its causes?

A

Shock due to insufficient circulatory volume.

Causes:

  • Haemorrhage
  • Burns
  • Severe or prolonged diarrhoea
  • Internal third space losses – peritonitis
  • Vomiting
22
Q

What is cardiogenic shock and what are its causes and some conditions that may result in it?

A

Shock that occurs due to the inability of the heart (cardiac pump) to deliver adequate circulating blood volume for tissue perfusion.

Causes of cardiogenic shock include:

  • Inadequate filling of the heart
  • Poor contractility of the heart
  • Obstruction of blood flow from heart to the central circulation

Patients in cardiogenic shock may have:

  • Acute MI
  • Serious cardiac rhythm disturbance
  • Cardiac tamponade
  • Tension pneumothorax
23
Q

What is neurogenic shock?

A

Shock that results in the loss of normal vasomotor tone and sympathetic impulses throughout the sympathetic nervous system, as a result of injury, leading to widespread vasodilation & relative hypotension.

24
Q

What is anaphylactic shock and what is its pathophysiology?

A

Anaphylactic shock is the hyperreaction of the immune system to the presence of an allergen. When this presence is detected plasma cells within the blood form immunoglobulin E antibodies that then attach to mast cells triggering the release of histamine. The release of histamine then triggers signs and symptoms including

  • Arterioles and capillaries dilate
  • Increases in capillary membrane permeability
  • Intravascular fluid leaks into interstitial space = decrease in intravascular volume
  • Constriction of upper and lower airways - secondary potential for complete airway obstruction
25
Q

What is septic shock and what are some of its causes?

A

Shock that occurs due to serious systemic bacterial infections. The immune system attempts to fight the infection however inevitably causes microvascular injury to the endothelium triggering pro-inflammatory molecules, coagulation and complement cascades. Due to the damage to the endothelium NO goes unregulated resulting in widespread vasodilation and permeability.
Septic shock is often associated with the following: Staphylococcal and streptococcal infections, pneumonia, postoperative patients, patients with indwelling lines, elderly and immuno-compromised.

26
Q

Why does cardiogenic shock develop in a patient who has had a severe myocardial infarction?

A

Death of tissue > heart can’t constrict efficiently > decreased cardiac output

27
Q

What secondary problems can arise from anaphylactic shock?

A
  • Vasodilation
  • Leaky capillaries
  • Laryngeal oedema
  • Broncho constriction
  • Hypotension
28
Q

Explain the causes of neurogenic shock.

A
  • Spinal injury above T6
  • Head injury
  • Stroke
  • OD
  • Tumour
29
Q

Give 5 possible causes of hypovolaemic shock.

A
  • Burns
  • Haemorrhage
  • Dehydration
  • Vomiting and diarrhoea
  • Diabetes
  • Endocrine disorders
30
Q

Name 3 types of patients who may be susceptible to septic shock.

A
  • Patients with indwelling lines
  • Post op patients
  • Elderly
  • Immune compromised
31
Q

What is the A-E treatment approach for shock patients?

A

A: AIRWAY: must be open, patent and protected
B: BREATHING: respiratory patterns often reflect the adequacy of ventilation and can offer clues to the presence of shock. Closely monitor pulse oximetry.
C: CIRCULATION: assess circulatory status thoroughly and prioritise uncontrolled bleeding.
Bleeding: Internal bleeding should be suspected in any patient with signs of shock. Rapid transport to definitive care is critical. IV fluid therapy should be performed en-route to avoid delay of definitive care
Perfusion: Evaluate rate, character, and location of pulses as part of circulatory assessment, colour, moisture, and temperature of skin. Cap refill test.
D: DISABILITY: a rapid assessment of GCS is essential to assess cerebral perfusion. Note agitation, confusion, combativeness as an indicator of poor cerebral perfusion. Any significant change in a patient’s GCS or senses should be considered an indicator of critical perfusion deficit.
E: EXPOSURE: close visual inspection can reveal conditions that may be life threatening: get down to the skin!

32
Q

What is Peggy’s Number 1 rule of shock?

A

Shock is always hypovolemic shock until proven otherwise.

33
Q

What are crystalloid solutions and list three examples?

A

Solutions created by dissolving crystals such as salts and sugars in water. They are

  • Low osmotic pressure
  • Equilibrates quickly between vascular and extravascular space
  • Cannot carry oxygen

Examples of crystalloids include Hartman’s solution, normal saline glucose solutions in water (eg: Dextrose)

34
Q

What are the dosage for glucose solutions?

A
  • PO Glucose gel (first line agent): 15g
  • IV Glucose 10% (second first line agent): 15g in 150ml drawn up in 6x 25 ml syringes and piggybacked on saline line.
  • IM Glucagon (third line agent): 1mg/1ml using hypokit
35
Q

What are colloid solutions and give three examples?

A

Solutions that contain molecules that are too large to pass through the capillary membrane therefore exhibit osmotic pressure and remain within the vascular compartment for a considerable time. E.g. Whole blood, Packed RBC, Plasma.

36
Q

What is the difference between Normal Saline and Hartman’s Solution?

A

Hartmann’s has extra electrolytes - calcium, potassium, and lactate

37
Q

What chief complaints may a patient in cardiogenic shock have?

A
  • Chest pain

- History of MI

38
Q

Why is skin perfusion an unreliable indicator in elderly patients?

A

May have reduce perfusion to extremities already

39
Q

List four s/s that might indicate poor cerebral perfusion.

A
  • Confusion
  • Agitation
  • Lethargy
  • Combativeness
40
Q

Shock Management:

A
  • Establish and maintain open airway: administer high-concentration O2 – nonrebreather 100% oxygen, assist ventilations.
  • Control external bleeding
  • Initiate IV fluid: two large-bore IV lines of volume-expanding fluid
  • Maintain normal body temperature: patients in shock often are unable to conserve body heat and can become hypothermic easily
  • Position: In absence of spine or head injury and if hypovolaemia is suspected, consider positioning patient in with legs raised
  • Monitor: cardiac rhythm and O2 saturation
  • Reassess: frequently reassess vital signs en-route

Medical Studies 1 (11 decks)

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