Shock and Resuscitation Flashcards

1
Q

what is shock? Definition:

A

– Inadequate oxygen delivery to the tissues

– A condition of severe hemodynamic & metabolic dysfunction characterized by reduced tissue perfusion, impaired oxygen delivery & inadequate cellular energy production

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Clinical Signs of Shock

A
  • Reduced level of mentation
  • Hypothermia / Cool extremities
  • Tachycardia (bradycardia in cats)
  • Increased respiratory rate & effort
  • Poor peripheral pulses
  • Decreased blood pressure
  • Pale mucous membranes
  • Prolonged capillary refill time
  • Decreased urine production
  • Decreased GI blood flow/ GI ulceration
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Shock - Physiologic Response

A

– Increased sympathetic output
* Epinephrine (adrenaline) & Norepinephrine released from adrenal glands

  • Increase in
    – Heart rate
    – Cardiac contractility
    – Vasoconstriction
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

how does vasoconstriction occur during shock? what parts of the body are more affected and why?

A
  • Organ selective
    – Affects organs with large numbers of a–adrenoreceptors * Skin, Skeletal mm, splanchnic organs, kidneys
    – Perfusion maintained to
  • Carotid, coronary & hepatic arteries
    – Allows preservation of blood flow to vital organs, but can result in ischemia of less vital tissues
  • Ie. Renal ischemia / failure
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

endocrine response to shock?

A
  1. Epinephrine & norepinephrine
    – Released from adrenal glands & vasomotor endplates
    – Immediate response
  2. Antidiuretic hormone
    – Released from the pituitary
    – To conserve water
    – Response within minutes
  3. Renin–Angiotensin–Aldosterone (RAAS) system
    – At the level of the kidneys
    – Stimulated to conserve Na+ & water
    – Response within hours
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

3 Stages of Shock

A
  1. Early compensatory shock
    – Physiologic responses maintain blood pressure
  2. Early decompensatory shock
    – Associated with clinical signs of shock
  3. Decompensatory / terminal shock
    – Irreversible shock
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Early Compensatory Shock; what is it, what are clinical signs? how is it created by the body?

A
  • Appropriate cardiovascular compensation
  • Clinical signs:
    – Tachycardia, normal or elevated BP, normal or increased pulses, hyperemic mm, CRT< 1 sec
  • Easily missed, animal essentially normal
  • Result of baroreceptor mediated release of catecholamines
    – successful increase in CO
  • Heart rate is KEY
  • Good response noted to volume replacement, good outcome
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Early Decompensatory Shock; what is it? why does it occur and what do we see? clinical signs? prognosis?

A
  • The 2nd stage of shock
  • Compensatory mechanisms tiring
  • Redistribution of blood flow:
    – decreased blood flow to the kidneys, gut, skin & muscles
  • Clinical signs:
    – Tachycardia, tachypnea, poor peripheral pulses, hypotension, prolonged CRT, pale mm, hypothermia, depressed mentation
  • Prognosis
    – Fair to good with immediate intervention
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Late Decompensatory Shock; what is it, when does it occur? what are the clinical signs? prognosis?

A
  • Terminal Shock
  • Compensatory mechanisms exhausted
  • Clinical signs:
    – Slowed heart rate (relative), pale cyanotic mm, absent CRT, weak / absent pulses, severe hypotension, hypothermia, mentally unresponsive / coma, no urine production
  • Generally irreversible
    – Not responsive to aggressive fluid resuscitation
  • Damage has overwhelmed the body’s natural protective mechanisms
    – Multiple organ dysfunction / failure
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

four broad categories of shock, based on pathophysiologic mechanisms:

A
  1. Hypovolemic
  2. Obstructive
  3. Distributive = vasodilatory = hyperdynamic
  4. Cardiogenic
  • Patient can suffer from more than one category
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what is cardiogenic shock?

A
  • Inadequate ventricular pump function
  • Inadequate delivery of oxygenated blood to vital organs
    > Hypoperfusion
  • Maybe due to:
    – Myocardial failure (ie. Cardiomyopathy)
    – Valvular dysfunction (ie. Severe mitral valve disease) – Arrhythmias
  • To be dealt with outside of this lecture
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what is Hypovolemic Shock?

A
  • Profound decrease in intravascular (blood) volume
    – Loss of ≥ 30-40% of circulating blood volume OR
    – 10-15% dehydration
  • Inadequate blood volume to deliver to vital organs
    >Hypoperfusion
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Etiology of hypovolemic shock

A
  1. Blood loss / hemorrhage
    * External
    * Internal
  2. Dehydration
    * Polyuria
    * GI loss
    * Burns
    * 3rd space losses (eg. ascites)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

signs of shock suggest how much blood loss?

A

> 30%

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

as you become dehydrated, where will your body draw water from?

A

interstitial fluid,
then intracellular fluid,
then intravascular fluid

-body will spare intravascular compartment via fluid shifts until profound dehydration is encountered

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

phases of hemorrhage

A
  1. interstitial fluid shifts
  2. water retention
17
Q

what is phase 1 of hemorrhage? when and why does it occur? what are the observable signs?

A
  • Phase 1 – Interstitial fluid shifts
    – Within 1 hour
    – Attempt to restore intravascular volume & organ perfusion
    – Fluid shift dilutes
  • Red cell mass (PCV)
  • Total solids (TS)
    – Splenic contracture in the dog & horse
  • Spleen can sequester up to 30% of the RBCs
18
Q

what are the immediate effects of fluid shifts in dogs (vs cats) during hemorrhage?

A

Within minutes
Splenic contracture in dogs (not cats):
Release of sequestered RBCs
*PCV falling but is boosted
*TS - falls

19
Q

what is phase 2 of hemorrhage/hypovolemic shock? what happens and what can we observe?

A
  • Phase 2– Water retention
  • Activation of the renin – angiotensin-aldosterone (RAAS) system
    – Promotes Na+ and H2O retention by the kidneys
    – Further drop in PCV noted
  • Within 8 hours – 36-50% of ultimate change in PCV
  • Within 24 hours – 70%
    – Administration of crystalloids or colloids will cause a more rapid decrease in PCV & Total Solids
20
Q

what is the etiology of non-cardiogenic, obstructive shock?

A

– Diminished cardiac output secondary to compression on the vascular system or obstruction to blood flow
– Blood can’t get to the heart!
– Blood can’t be ejected from the heart!
– Examples
* Gastric dilation volvolus
* Tension pneumothorax
* Pericardial tamponade
* Pulmonary embolism

21
Q

what are the causes of distributive (vasodilatory) shock?

A
  • Maldistribution of blood flow
    – Microvascular circulation
    – Failure of the vascular smooth muscle to constrict
    > Vasodilatory shock
  • Most common causes:
    – Sepsis, anaphylaxis, a hypoadrenocorticism, drug reactions
    & massive trauma

Normally 70% of blood volume is in the venous system
>Massive vasodilation leads to ….. Relative hypovolemia

“Relative Hypovolemia” - vessels dilate
1. Underfilled venous system… Poor venous return…..decreased arterial blood pressure
2. Decreased systemic vascular resistance (SVR)
3. Initially improved cardiac output

22
Q

what do we observe clinically in the initial phase of distributive shock?

A

Initially Hyperdynamic Phase
* Normal to increased CO
* Brick red mucous membranes
* Rapid (<1 sec) CRT
* Tachycardia
* Bounding pulses
* Warm extremities

23
Q

how do the clinical signs of distributive/septic shock differ from those of other types of shock (eg. hypovolemic)?

A
  • Reduced level of mentation
  • Hypothermia / Cool extremities (warm extremities)
  • Tachycardia (bradycardia in cats)
  • Increased respiratory rate & effort
  • Poor peripheral pulses (bounding peripheral pulses)
  • Decreased blood pressure
  • Pale mucous membranes (injected mucous membranes)
  • Prolonged capillary refill time (rapid)
  • Decreased urine production
  • Decreased GI blood flow/ GI ulceration

=> Distributive/Septic shock in parentheses

24
Q

….Final common pathway for shock of any cause:

A

Decompensation
* Decreased cardiac contractility
* Decreased CO
* Poor peripheral pulses
* Hypotension
* Pale mm
* Prolonged CRT > 2-3 seconds

25
Patient Assessment for shock; what do we look at
* Heart rate & rhythm * MM colour & CRT * Pulse quality & Blood Pressure * Urine output * PCV/TS * Lactate production * Blood gases
26
how often should we re-evaluate parameters when monitoring for shock?
– Every 5 – 15 minutes
27
heart rate and rhythm during shock; what do we expect, what do we look for and how?
* Shock is associated with tachycardia 1. Auscultate the heart * Heart sounds – are they there? * Heart rate * Arrhythmias 2. Feel a pulse * Pulse rate * Rhythm – note pulse deficits * Pulse pressure * Recommend ECG if available
28
MM Colour & CRT during shock; what are we looking for?
* Assessment of tissue perfusion * CRT is evaluated by blanching the mm & noting the time to return of colour * Normal is < 2 seconds (1-1.5 seconds) * Shock causes a prolongation of the CRT – Except vasodilatory shock – CRT is shortened
29
what does blood pressure have to fall to for us to consider it hypotension?
* Normal: ~ Systolic 120 mmHg ; MAP 100 mmHg ; Diastolic 80 mmHG * Hypotension – Systolic < 90 mmHg – MAP <60 mmHg – Severe hypotension is the hallmark of shock!
30
what blood pressure does cerebral, renal, and muscle perfusion require?
* Cerebral perfusion requires MAP > 40mmHg * Renal perfusion requires MAP > 60 mmHg * Muscle perfusion requires MAP >70mmHG
31
what does pulse quality depend on? what pulses are normally most prominent and when will they be absent? when will peripheral pulse generally be absent?
* Dependent on difference palpated between systolic & diastolic pressures = pressure difference * But, pressure difference; – 120/80 mmHg = 40 mmHg – 90/50 mmHg = 40 mmHg > thready * Femoral pulses – Most prominent – Absent once systolic BP < 40 mmHg * Peripheral pulses (dorsal pedal, radial) – Absent when systolic BP < 60 – 70 mmHg
32
* Arterial blood pressure (BP) product of:
– BP = CO x SVR – BP = (HR x SV) x SVR
33
in compensatory shock, BP may be;
normal or increased
34
how will BP change with decompensation
decrease
35
what is urine output a measure of? what is a normal value? how can we monitor this easily?
* Measure of organ perfusion * If there is pee, the kidneys are being perfused * Normal urine production – 1-2 ml/kg/hr * Palpate & monitor the size of the bladder routinely
36
how should we monitor PCV and total solids during a shock case? how often?
* Establish at admission (baseline) – May be normal on admission as fluid shifts have not had time to occur – Do not help assess degree of acute hemorrhage * Repeat in: – 15 minutes – 30-60 minutes
37
why is lactate production useful to measure during a shock case? what is the normal value? how valuable is this measurement for checking response to therapy?
* Lactic acid is a by-product of anearobic metabolism * With hypoperfusion of organs, anearobic metabolism prevails >increased production of lactate * Normal lactate <2 mmol/L * Trending an improvement in lactate is the best & most current way to note response to therapy