Perfusion: Shock Flashcards
Define Shock
a clinical syndrome characterized by a systemic imbalance between oxygen supply and demand
What is needed by the cardiovascular system to keep the body running?
- Sufficient cardiac output
- an uncompromised vascular system, in which the vessels have a diameter sufficient to allow unimpeded blood flow and have good tone
- a volume of blood sufficient to fill the circulatory system, and a BP adequate to maintain blood flow
- Tissues that are able to extract and use the oxygen delivered through the capillaries
What happens in the body when shock occurs?
- one or more cardiovascular components do not function
- inadequate tissue perfusion
- the body attempts to maintain vital organs and to preserve life following a drop in cellular perfusion
- A drop in MAP (decrease in CO or an increase in the size of the vascular bed)
How many classes of shock are there?
4
Describe Class I: Early Shock
- drop in MAP of less than 10 mmHg from normal
- circulating blood volume decreases
- body reacts to a decrease in arterial pressure by increasing HR and signaling SNS response
- SNS response causes peripheral vasoconstriction= increased SVR and a rise in arterial pressure
Describe Class II: Compensatory Shock
- The body tries to make up for the loss of one of the cardiovascular components
- MAP below 10-15 mmHg/blood volume decreases by 15-30%
- Stimulation of SNS: fight or flight hormones, vasoconstriction, decreases perfusion to skin and abdominal viscera, increase heart rate and force= increase in CO and oxygenation
- Renin-angiotensin response: aldosterone stimulated= reabsorb water and sodium, loss potassium; water retention increases blood volume, raises BP
- ADH stimulated: reabsorption of more water
- MAP falling causes decreased capillary hydrostatic pressure= fluid shift from interstitial space into the capillaries= more blood volume
Describe Class III: Decompensated Shock (progressive shock)
- decrease in MAP of 20 mmHg or more below normal levels/ blood volume loss of 30-40%
- Vasoconstriction response limits blood flow to the point that cells become oxygen deficient
- Lactic acid is formed as a byproduct of anaerobic metabolism
- cell damage
- increased hydrostatic pressure= fluid shift back to interstitial space
- perfusion to the skin, skeletal muscles, kidneys, and GI organs decreases
- cells in the heart/brain become hypoxic; other tissues become ischemic and anoxic
Describe Class IV: Refractory Shock (irreversible)
- widespread and generalized anoxia (no treatment can reverse damage)
- Death of cells and tissues
- death of organs
What happens to the respiratory system during shock and what is a potential complication?
- increased respiratory rate
- respiratory acidosis
Potential complication: ARDS
What happens to the urinary system during shock, and what are some potential complications with the urinary system?
- decreased renal perfusion
- decreased GFR
- Late: Oliguria
Potential complications: - acute tubular necrosis
- kidney failure
What happens to the hepatic system during shock, and what is a potential complication with the liver?
- Early: increased glucose production
- Progressive: decreased glucose production= hypoglycemia
- Progressive: decreased lactic acid conversion= metabolic acidosis
Potential complication: destroyed Kupffer cells= systemic bacterial infections
What happens to the GI system during shock, and what is a potential complication?
- Early: decreased GI motility
- Late: paralytic ileus
- Late: ulceration of the GI mucosa
potential complication: bowel necrosis
What happens to the neurologic system during shock?
- decreased cognition
- decreased sympathetic activity
- decreased consciousness
- early: restlessness, apathy
- Progressive: Lethargy
- Late: coma
What happens to the cardiovascular system during shock?
- Early: no change
- Progressive: lightly elevated pulse and slowly rising heart rate
- Progressive: Sinus tachycardia
- Progressive thready pulse
- Late: Map <60 mmHg
- Late: Steadily decreasing BP and Steadily decreasing Cardiac output
- Late: imperceptible pulses
What happens to the integumentary system during shock?
- Pallor (skin, lips, oral mucosa, nail beds, conjunctiva)
- cool, moist skin
- Late: edema
What happens to the metabolic processes in the body during shock?
- decreased temperature
- thirst
- acidosis (metabolic and respiratory)
What is hypovolemic shock?
shock caused by a decrease in intravascular volume of 15% or more (amount of venous blood returning to the heart decreases, and ventricular filling drops)
What things can trigger hypovolemic shock?
- loss of blood volume from hemorrhage
- loss of of intravascular fluid from the skin because of injuries such as burns
- Loss of blood volume from severe dehydration
- Loss of body fluid from the GI system because of persistent and severe vomiting or diarrhea or continuous NG suctioning
- Renal losses of fluid because of diuretic use or endocrine disorders, such as diabetes insipidus
- conditions causing fluid shifts from the intravascular compartment to the interstitial space
- Third spacing because of disorders such as liver diseases with ascites, pleural effusion, or intestinal obstruction
Describe stage 1 of hypovolemic shock?
- loss of blood volume
- decreased Cardiac output= decreased MAP
- compensatory mechanisms (increased stroke volume x increased heart rate= increased cardiac output)
- peripheral vasoconstriction= increased stroke volume
Describe stage 2 of hypovolemic shock
- continued loss of blood volume
Compensatory Mechanisms: - Vasoconstriction: periphery, skin, abdominal organs
- Vasodilation: heart, skeletal muscles, respiratory retention of H2O and Na+
- up SV x up HR= up CO + up SVR= up MAP
Describe stage 3 of hypovolemic shock
- continued loss of blood volume
- decreased CO= Decreased MAP
- decreased tissue perfusion and oxygenation
- Cellular anaerobic metabolism
- Cellular hypoxia and death
Describe stage 4 of hypovolemic shock
Irreversible sock–> Multisystem organ failure–> death
What is cardiogenic shock?
the heart’s pumping ability is compromised to the point that it cannot maintain CO and adequate perfusion
What can cause cardiogenic shock?
- MI/cardiac arrest
- cardiac tamponade
- restrictive pericarditis
- Dysrhythmias such as VF or VT
- pathologic changes in valves
- cardiomyopathies from HTN, alcohol, bacterial or viral infections, or ischemia
- complications of cardiac surgery
- electrolyte imbalances, especially changes in normal potassium and calcium levels
- drugs affecting cardiac muscle contractility
- head injuries causing damage to the cardio regulatory center
Describe what happens in the body with cardiogenic shock
- decrease in MAP
- myocardium depleted of oxygen causing further myocardial ischemia and necrosis
- Cyanosis because of stagnating blood increasing the demand for blood out of the capillaries
- left-ventricular end-diastolic pressure increases
- Possible pulmonary edema
- possible right atrial pressure= JVD
What is obstructive shock?
Shock that is caused by an obstruction in the heart or great vessels that either impedes venous return or prevents effective cardiac pumping action
What things can cause obstructive hock?
- impaired diastolic filling (obstructive shock, pneumothorax)
- increased right ventricular afterload (PE)
- increased left ventricular afterload (aortic stenosis, abdominal distention)
What is distributive shock (vasogenic shock)?
Several types of shock that result from widespread vasodilation and decreased peripheral resistance
What is septic shock (septicemia)?
Altered perfusion resulting from a systemic infection that manifests with hypotension, delayed capillary refill, and inadequate perfusion and oxygen of vital body tissues
What is neurologic shock?
The result of an imbalance between parasympathetic and sympathetic stimulation of vascular smooth muscle
What conditions can cause neurologic shock?
- head injuries
- spinal cord trauma
- insulin reactions (which cause hypoglycemia, decreasing glucose to the medulla)
- Use of CNS depressants
- . Anesthesia
- severe pain
- prolonged exposure to heat
What happens to the body during neurogenic shock?
- bradycardia
- tachycardia when compensatory mechanisms are initiated
- CVP drops as veins dilate
- venous return to the heart decreases
- Stroke volume decreases and MAP falls
- Early stages: extremities are warm and pink
- Shock progressing: skin is pale and cool
What are some ways to prevent cardiogenic shock?
- control BP and avoid HTN
- no smoking
- regular exercise
- maintain a healthy weight
- reduce the intake of cholesterol and saturated fats
What are some ways to prevent hemorrhagic and neurogenic shock?
- avoid risk taking behaviors (driving while under the influence, dangerous sports)
- wear seatbelts, helmets, and other protective gear
3 prevent infection
What is the best way to prevent septic shock?
recognize the signs and prevent infection (good hand hygiene and infection control measures)
What are the general manifestations of shock?
Early: body compensating for hypotension or hypovolemia: 1. tachycardia 2. increased respiratory effort 3. decreased urine output 4. sweating Progressive: 1. systolic BP drops 2. pulse pressure narrows 3. cerebral blood flow reduced (Decreased LOC)
What are the clinical manifestations of the early stage of hypovolemic shock?
- BP: normal- slightly decreased
- Pulse: Slightly increased from baseline
- Respirations: normal (baseline)
- Skin: cool, pale (in periphery), moist
- Mental status: alert and oriented
- Urine output: Slight decrease
- other: thirst, decreased capillary refill time