Unit 2: Overview of Shock Flashcards
How do the tissues maintain cellular functioning?
the tissues of the body require a continuous supply of oxygen in order to maintain cellular functioning
Shock
life-threatening syndrome
- occurs when the circulatory system is unable to supply adequate amounts of oxygen to the tissues to meet basic metabolic requirement
- creates a state of tissue hypoxia; an imbalance of cellular oxygen and demand
- w/o immediate tx to reverse this imbalance, organ system failure and death may result
Cardiac Output
amount of blood ejected by the heart every minute
-function of stroke volume and heart rate
Stroke Volume
amount of blood ejected w/ each ventricular contraction
-influenced by preload, afterload, and contractility
Preload
amount of blood in the ventricles at the need of diastole
- reflection of fluid volume status
- “filling pressures”
- a decrease in preload = decreased CO
- increase in preload = increased CO
Afterload
resistance to flow that the ventricles must overcome to eject its contents
-increasing the afterload may make it harder for the heart to eject blood into systemic circulation
Contractility
refers to the force of the mechanical contraction
-poor contractility decreases stroke volume, thus decreasing CO
Oxygen Delivery (DO2)
amount of oxygen delivered to the tissues
-assessed through evaluation of CO and arterial oxygen content
>Arterial oxygen content: hemoglobin levels, percentage of hemoglobin saturated w/ oxygen, and amount of 02 dissolved in plasma (Pa02)
Oxygen Consumption (V02)
amount of oxygen extracted from the blood at tissue level
-measured through evaluation of blood sample: venous oxygen saturation (Sv02)
Venous Oxygen Saturation (Sv02)
blood sample
-reflects amount of oxygenated blood returned to the right heart by the pulmonary veins
-Normal Sv02: between 60 and 75%
-Decreased = tissues are extracting more oxygen than normal
>results from decreased oxygen delivery (DO2), which may be a decrease in oxygen content, hemoglobin, and CO
-also may reflect an inability to increase delivery in response to stressor such as pain or fever
Oxygen Debt
difference between normal V02 and V02 during the low-D02 state
(V02 = oxygen consumption)
-longer the imbalance between cellular oxygen supply and demand, the larger the debt becomes
Stages of Shock
- Initial
- Compensatory
- Progressive
- Refractory
Initial Stage of Shock
decreased oxygen delivery to the tissues
> Clinical Manifestations:
-subtle or none
Compensatory Stage of Shock
Initiation of compensatory mechanism in an effort to maintain an effort to maintain adequate volume, cardiac output, and blood flow to the tissues
- Vasoconstriction
- Increased sodium + water reabsorption
- Shunting of blood away from non-essential organs
- Increased glucose production
> Clinical manifestations:
- restlessness, confusion
- increased HR
- tachypnea
- respiratory alkalosis
- oliguria
- hyperglycemia
- decreased bowel sounds
- weak pulses
- cool, moist skin
Progressive Stage of Shock
failure of compensatory mechanisms to maintain adequate blood pressure and circulating volumes
- extensive shunting of blood away from nonessential organs
- failure of sodium potassium pump
> Clinical manifestations:
- lethargy or coma
- hypotension
- dysrythmias
- anuria
- absent bowel sounds
- severe metabolic acidosis
- respiratory acidosis
- cold extremities
- weak or absent pulses
Refractory Stage of Shock
prolonged inadequate blood supply to the cells
- cell death and multisystem organ failure
- inefficient anaerobic metabolism
- extreme tissue hypoxia
> Clinical Manifestations:
- coma
- severe hypotension
- severe metabolic + respiratory acidosis
- hepatic failure
- renal failure
- peripheral tissue ischemia + necrosis
Physical Assessment of Shock
- Central Venous System (CNS)
- Cardiovascular System
- Respiratory System
- Renal System
- GI System
Physical Assessment: Central Nervous System (CNS)
- changes in CNS perfusion may be initial indication of inadequate D02 to tissues
- restlessness, confusion, and irritability are beginning indicators of poor cerebral perfusion
Physical Assessment: Cardiovascular System
- BP valuable indicator of fluid status and CO
- a low BP = problem
- In Shock, BP decreases b/c of inadequate venous return to the heart, vasodilation, or decreased contractility of heart muscle
- Prolonged hypotension = continued presence of shock
- Finding indicative of a compensatory stage of shock -> a narrow pulse pressure which results from compensatory vasoconstriction causing an increase in diastolic BP w/ only slight increase in systolic pressure
- tachycardia d/t stimulation of the sympathetic nervous system as a way to increase CO
- if shock progresses, heart rate may slow
- b/c of shunting of blood to vital organs, the skin and periphery become cool, pale, mottled, or cyanotic w/ thready pulses and sluggish capillary refill
Physical Assessment: Respiratory System
- early stages show increased respirations in an effort to increase oxygenation and decrease carbon dioxide levels (CO2) d/t metabolic acidosis
- oxygenation measured through pulse oximetry
- ABGs for accurate assessment
Physical Assessment: Renal System
- poor peripheral perfusion if urine output is decreased
- oliguria in early stages (small amount)
- Anuria in later stages
- increased creatinine (renal failure)
Physical Assessments: GI System
- indicates poor perfusion through sluggish, hypoactive bowel sounds
- nausea + vomiting
- cell damage in GI tract allows translocation of intestinal bacteria to the systemic circulation; increased risk of sepsis
Hemodynamic Monitoring
- monitoring of BP, CO, and variables that affect CO
- done through an arterial line, central venous catheter, or pulmonary artery catheter
Arterial Line
- BP continually displayed
- provides easy access for blood analysis (ABGs)
