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)
Pulmonary Artery Catheter
a flexible, balloon tipped catheter that is guided through the right side of the heat and into the pulmonary artery
- info about CO and variables that affect it: preload, afterload, contractility
- 4 Lumens: Proximal, Distal, Thermistor, and Inflation
PA Catheter: Proximal Lumen
- monitors right atrial pressure
- reflection of right heart preload, and right ventricular end-diastolic volume
- port used to inject the solution to obtain a thermodilution CO
PA Catheter: Distal Lumen
- rests within pulmonary artery
- monitors systolic, diastolic, and mean PA pressures
- monitors pulmonary artery wedge pressure/ pulmonary artery occlusion pressure (PAOP)
- PAOP obtained when the balloon located at the end of the inflation lumen is inflated w/ 1.5 ml of air; balloon floats into a wedge position in the PA, which occluded that branch of PA, obscuring data from the right heart
- the values obtained reflect left heart pressures; PAOP reflects left heart preload or the amount of blood in the left ventricle at the end of diastole
- also be used for drawing a venous oxygen saturation (SvO2)
SvO2
provides a “mixed” sample of blood from both the superior and inferior vena cava
-provides info on oxygenation extraction throughout the body
PA Catheter: Thermistor Port
- built into the tip of PA catheter
- continuously measures the ambient blood temperature around it
- Normal CO: 4 to 6 L/min
- Normal CI: 2.5 to 4 L/min
- small bolus of cooler saline is inserted through the proximal lumen
Central Venous Catheter
uses a long catheter threaded through the superior vena cava w/ distal port resting in the superior vena cava above the junction w/ the right atrium
- allows central venous pressure monitoring (CVP); right heart preload
- Decreased CVP = low volume state
- Increased CVP = increased volume
- can also draw a central venous oxygen saturation (SvO2), if a PA line is not in place; provides info on oxygen extraction in the brain and upper body
Laboratory Analysis For Shock
- ABGs
- SvO2 or ScvO2
- Base Deficit
- Lactate Level
- Hemoglobin + Hematocrit
- Electrolytes
- Renal Studies
- Liver Studies
- Glucose
Arterial Blood Gases (ABGs)
provide info on oxygenation, ventilation, and presence of acidosis or alkalosis (metabolic or respiratory)
- hyperventilation in early shock = respiratory alkalosis
- later stages of shock –> metabolic acidosis
- presence of hypoxemia, or decreased PaO2 = development of complications (acute respiratory distress syndrome; ARDS)
SvO2 or ScvO2
evaluates VO2 (oxygen consumption) -if falls below normal = tissues are extracting more oxygen than normal; results from decreased oxygen delivery (DO2)
Lactate
elevated = increased anaerobic metabolism d/t tissue hypoperfusion
Base Deficit
- obtained through ABGs
- amount of base required to achieve a pH of 7.4
- a higher level of base required to achieve a normal pH (a negative base deficit) is consistent w/ acidosis
