Perioperative Temperature Flashcards
Lecture 1 (153 cards)
1
Q
What happens to patients’ ability to regulate body temperature under General Anesthesia?
A
Patients lose their normal mechanism to regulate body temperature
70% of all surgeries experience unintended hypothermia.
2
Q
What is the normal body temperature range?
A
36o-37.5o C
3
Q
How much can body temperature decrease within 30 minutes of anesthesia?
A
0.5o-1.5o C
4
Q
What primarily accounts for the drop in body temperature during anesthesia?
A
Redistribution
5
Q
in terms of the human body, heat is derived from _______ occuring in all living cells
A
biochemical reactions
6
Q
at rest, more than _____ of the body’s heat is generated as a result of the inefficiency of the biochemical processes that convert food energy into free energy pool
A
more than HALF
7
Q
What is thermo homeostasis?
A
The balance between heat production (thermogenesis) and heat loss (thermolysis)
8
Q
What is the most effective mechanism for maintaining the body’s core temperature?
A
Behavior
9
Q
under normal conditions, the body’s core temp is ______ warmer than the temperature of the periphery?
A
2-4 Degrees Celsius
10
Q
What role does the hypothalamus play in temperature regulation?
A
It is the thermoregulatory center for the body that regulates temperature and controls the release of hormones.
11
Q
name all the roles the hypothalamus plays:
there’s like 5
A
controls the release of the 8 major hormones
regulates temp
controls food and water intake
sexual behavior and reproduction
control of daily cycles in physiological state and behavior
mediation of emotional responses
shes important
12
Q
What is hypothermia defined as?
A
A core temperature of less than 36oC
13
Q
What are some anesthetic agents that interfere with the hypothalamus?
A
- Desflurane
- Alfentanil
- Dexmedetomidine
- Propofol
14
Q
TRUE or FALSE: patients under anesthesia have their ability to thermoregulate?
A
false, we take that shit away from them HA
15
Q
What occurs in the body as a response to cold?
A
Vasoconstriction and an increase in basal metabolic rate
16
Q
during the activation of sympathetic centers (SNS), what releases from sympathetic fibers and constricts skin vessels?
A
norepinephrine
17
Q
during the activation of sympathetic centers (SNS), what is secreted from adrenal medualla and increases thermogenesis by the combustion of fatty acids and glucose?
A
epinephrine
18
Q
what is a centrally mediated neural response which causes involuntary rhythmic contractions of muscles producing heat?
A
shivering
19
Q
what % can shivering increase O2 consumption by?
A
300-400%
sheeeeesh
20
Q
what is the most effective involuntary heat fighting response in man?
A
sweating
21
Q
What are the phases of intraoperative hypothermia?
A
- Phase I: Core temperature drops 1-2o C
- Phase II: Gradual decrease of core temperature over 2-4 hours
- Phase III: Core temperature plateaus and stabilizes
22
Q
What are the types of heat loss in the OR?
A
- Conduction
- Convection
- Evaporation
- Radiation
23
Q
what % of heat loss is attributed to conduction?
A
3-5%
24
Q
what % of heat loss is attributed to convection?
A
15-20%
25
what %n of heat loss is attributed to evaporation?
20%
26
What percentage of peri-operative heat loss is attributed to radiation?
40-50%
27
true or false: conduction requires direct contact between objects for heat transfer?
true
28
what method of heat loss involves heat being transferred from one object to another through contact with fluid or air?
convection
29
OR air is circulated how many times per hour?
14
30
what are the 3 reasons for OR air circulation?
to prevent infection
to removal anesthetic trace gases
and the comfort of staff
31
what rate does insensible water loss evaporation from the skin and lungs occur at?
30 mL/hr
32
what method of heat loss in the OR occurs by diffusion?
radiation
33
what is the most significant factor of patient heat loss int he OR?
radiation
34
name all the factors affecting incidence of unintentional hypothermia:
extremes of age
the type of surgery
the length of surgery
the ambient temp of the room
35
how much does core temp drop during the first hour of anesthesia?
1-2 degrees Celsius
36
core temp plateus and stabilizes how many hours after induction?
3-4 hours
37
What can happen to cardiac function in response to hypothermia during anesthesia?
Leads to sinus bradycardia
prolonged PR
wide QRS
prolonged QT, ST, and T wave changes
38
reversible hypokalemia associated with hypothermia places the patient at increased risk for:
cardiac failure
myocardial ischemia
arrhythmias
asystole
39
Arrhtymias are most common at what temperature?
what about vfib?
<31 celsius
<30 Celsius
40
How does hypothermia affect drug metabolism?
Decreases liver metabolism and renal excretion, prolonging drugs' circulation time.
41
What physiological changes occur during phase I of intraoperative hypothermia?
Core temperature drops due to anesthesia-induced vasodilation and heat redistribution.
42
What is the impact of hypothermia on the immune system?
Increases the incidence of surgical wound infections 3 fold.
43
What happens to the oxyhemoglobin dissociation curve during hypothermia?
It shifts to the left, increasing hemoglobin's affinity for oxygen., leading to lower o2 delivery to tissues
44
pH rises ______ units per Celsius decreae in temp
0.015 units
45
What is the relationship between temperature and clotting times?
Hypothermia leads to prolonged clotting and bleeding times.
46
Is coagulapathy reversible with re-warming the patient?
yessssss
47
Fill in the blank: The hypothalamus releases _______ to increase metabolic rate in response to cold.
[Thyroid Stimulating Hormone (TSH)]
48
True or False: Hypothermia can lead to decreased drug effectiveness due to altered pharmacokinetics.
True
49
What happens to the duration of action of Vecuronium with a 2°C drop in core temperature?
Duration of action is doubled
## Footnote
This indicates the impact of hypothermia on neuromuscular blockade.
50
How much does the MAC of volatile anesthetic agents decrease for each 1°C drop in core temperature?
Decreased by 5-7%
## Footnote
This suggests that less anesthetic is needed to maintain anesthesia.
51
What is the effect of hypothermia on muscle twitch strength?
Decreases by 10-15%
## Footnote
This occurs even without muscle relaxants.
52
What is the onset of action of Neostigmine in a normothermic patient?
How about a cold patient?
11 minutes
## Footnote
In cold patients, it rises to 23 minutes.
53
How much does operative hypothermia prolong the length of stay in the PACU?
30-45 minutes
## Footnote
This is particularly significant for elderly patients.
54
What factors put elderly patients at risk for hypothermia?
* Less muscle and adipose tissue
* Less heat waste
## Footnote
These factors contribute to increased vulnerability to temperature changes.
55
What can lower the incidence of shivering in patients?
* Use of narcotics
* Warming devices
## Footnote
Narcotics like Demerol are particularly effective.
56
What is the cost of complications from unintentional hypothermia in an uncomplicated MI?
$3700
## Footnote
This highlights the financial impact of hypothermia-related complications.
57
What is the cost associated with a new onset of A Fib due to hypothermia?
$4500
## Footnote
This emphasizes the importance of preventing hypothermia.
58
What is a significant cost associated with a sternal wound infection?
Over $100,000
## Footnote
This illustrates the severe financial repercussions of surgical complications.
59
What techniques can CRNA/NAR use to minimize hypothermia?
* Limit cutaneous heat loss
* Prevent evaporative cooling
* Limit conductive cooling from cold IV fluids
## Footnote
These methods are crucial in maintaining patient temperature during surgery.
60
What is the best heat/cost ratio method for preventing hypothermia?
Forced-air warmers
## Footnote
They are effective even with less than 50% body coverage.
61
how many minutes of pre-warming can prevent or minimize phase I hypothermia?
30 minutes
62
What is the mean body temperature decrease per liter of room temperature IV fluid administered?
0.250 °C
## Footnote
This indicates the significant impact of IV fluid temperature on body temperature.
63
What is the maximum temperature to which IV fluids should be heated?
43 °C
## Footnote
Heating above this can cause burns.
64
What is a passive method of warming patients during surgery?
Warmed cotton blankets and thermal drapes
## Footnote
This method can reduce heat loss by 30%.
65
What is the most effective method to prevent hypothermia?
Forced-air warming systems
## Footnote
They are efficient in warming patients in the OR.
66
What are Heat and Moisture Exchangers (HMEs) often referred to as?
Artificial nose
## Footnote
They help humidify inspired air but add dead space to the circuit.
67
maintenance of ambient temperature ____ needed to maintain normothermia without the use of heat conservation devices
>21 C
68
name 4 pros of the HME
small size/light weight
inexpensive
good filtration
work failry quickly
69
name some cons of the HME
adds dead space to circuit
can contribute to increased airway resistance
can add weight
may not be necessary for short cases
can take up to 20 min to even be fully functional
70
what is the second means of adding humidity to the anesthesia circuit
humidifiers
71
What is the difference between electricity and electrical energy?
Electricity is the flow of electrons; electrical energy is the work done by that flow
## Footnote
This distinction is crucial in understanding electrical systems.
72
What is the standard unit for measuring electrical current?
Ampere (A)
## Footnote
This is a fundamental unit in electrical engineering.
73
electrical energy (aka power) is measured in what?
watts
74
true or false: metals are always full of movable charge
trueeeee
75
the electrical force that causes free flow electrons to move from one atom to another is known as what?
voltage
76
how is electrical resistance to flow measured?
in Ohms
77
What does Ohm’s Law state?
E = I x R
## Footnote
This equation relates voltage (E), current (I), and resistance (R).
78
What are the three categories of electricity?
* Conductors
* Insulators
* Semiconductors
## Footnote
Each category has different properties regarding electron flow.
79
Any substances such as metal which have outer electrons that are loosely bound are good conductors of electricity:
conductors
80
what Are materials that have their electrons firmly bound and therefore not normally able to move and form electrical current.
insulators
81
in a ______ the outer electrons are bound to atoms less firmly than an insulator
semiconductors
82
what is a flow of electrical charge through carriers, usually electrons.
electrical current
83
what describes a steady flow of electrons along a wire or through a component in one direction only
direct current
84
what describes the flow of electrons in one direction then in the opposite direction along a wire.
alternating current
85
It takes approximately ___ times as much DC current than Alternating Current current to cause ventricular fibrillation.
3x
86
What is skin impedance?
Resistance to the flow of electrical energy through the skin
## Footnote
It varies with moisture levels and can indicate autonomic activity.
87
skin impedence is high or low with dry and damp skin?
high-dry
low-damp
88
What two factors affect the successful use of defibrillation?
* Energy output
* Resistance to flow
## Footnote
These factors are critical for effective defibrillation.
89
What is the primary determinant of resistance to current flow during defibrillation?
Transthoracic impedance
## Footnote
This is influenced by factors such as paddle size and contact pressure.
90
What happens when a person contacts an electrical circuit at two points?
They complete the circuit and may receive an electrical shock
## Footnote
This can lead to serious injuries or death.
91
What is required for current to flow through an individual?
A voltage source
92
true or false: all electrical equipment leak current?
true
the magnitude of such leaks are normally imperceptible to touch (<1mA)
93
How can electrical current damage cells?
By disrupting normal electrical function
94
what o Refers to large amount of current flowing through a person, which can cause harm or death?
macroshock
95
what o Refers to very small amounts of current and applies only to electrically susceptible patients?
microshock
96
are macroshocks electrically susceptible?
nope
| idk what this means
97
What can electrical current cause depending on its magnitude?
* Muscle contraction
* Altered brain function
* Respiratory paralysis
* Disruption of heart function leading to v-fib
98
What happens to the body when electrical current is dissipated?
Resistance is encountered and temperature elevates
99
What is the typical outcome of accidents involving household currents?
Usually do not result in severe burns
100
What determines the severity of an electrical shock?
Amount of current (amperes) and duration of current flow
101
Define macroshock.
Refers to a large amount of current flowing through a person that can cause harm or death
102
What is microshock?
Refers to very small amounts of current that applies only to electrically susceptible patients
103
What are electrically susceptible patients?
Patients with an external conduit in direct contact with the heart
104
What amount of current can cause ventricular fibrillation in electrically susceptible patients?
Minute amounts of current (microshock)
105
What is the impact of prolonged contact with an electrical source?
More energy is released, causing more tissue damage
106
what is the most important factor in preventing microshock?
an intact equipment ground wire
107
What are the two types of grounding?
* Grounding of electrical power
* Grounding of electrical equipment
108
What are the functions of the equipment ground wire?
* Provides a low-resistance path for fault current
* Dissipates leakage currents
* Provides information to the Line Isolation Monitor
109
What is the purpose of an Isolation Transformer?
To supply ungrounded power to the operating room
110
What does a Line Isolation Monitor do?
Monitors the integrity of an isolated power system
111
What happens if a faulty piece of equipment is connected to an isolated power system?
The system may change back to a conventional grounded system
112
What is the acceptable phase for Line Isolation Monitor alarm?
Set between 2 and 5 mA
113
what the heck do you do if the line isolation monitor alarm is triggered?
| besides cry
check the gauge to determine if its a true fault
are too many shits plugged in?
114
true/false: a life supporting device is faulty, its fine to just disconnect it
false, it might be necessary to continue using the faulty equipment
115
what does it mean if the line isolation monitor alarm is >5mA?
a piece of equipment iwth a broken ground wire is in use
116
What is the function of an Electrosurgery Unit (ESU)?
Generates very-high frequency currents for cutting and coagulation
117
how many Hz is coming out of the wall of the ESU?
60 hz
118
the amount of heat generated in ESU is proportional to ______ and inversely proportional to ____
- to the square of the current
- area thru which the current passes
119
modern ESU can produce heat in excess of what temp?
300 C
120
What is the temperature threshold for protein denaturation?
Above 45°C
121
What is the temperature range for coagulation in electrosurgery?
60 – 70°C
122
What is electrotomy?
Rapid evaporation of fluid within the cell membrane at temperatures above 100°C
123
What differentiates monopolar from bipolar cautery?
Monopolar uses two connections; bipolar uses one side of forceps for current flow
124
What can happen if the dispersive electrode is improperly placed?
Substantial burns can occur
125
What is the significance of the ASA Closed Claims Project regarding burn injuries?
Burn injuries are a significant source of morbidity and liability for anesthesia providers
126
what cautery technique should be used if the patient has an AICD?
bipolar
127
What percentage of surgical fires are considered preventable?
75%
128
what demographics/characteristcs is more prone to OR fires?
females
> 56 yrs old
ASA 1 or 2
outpatient
MAC or room air cases
129
What are the most common causes of burn claims in the operating room?
* IV bags or bottles
* Warming devices
* Cautery fires/burns
130
What are the risks associated with electrosurgery in patients with pacemakers?
Impairment of pacemaker function and potential for ventricular fibrillation
131
What is the role of an anesthetist regarding fire safety in the operating room?
Protecting the patient from fire hazards
132
What is a significant cause of burn injuries in the operating room according to the ASA Closed Claims Database?
Cautery fires
133
What is the impact of improper use of warming devices in the operating room?
Can result in burn injuries
134
what anatomic location is at highest risk for a surgical fire?
face, head, chest, neck
| 44%
135
What are the three components of the Fire Triad?
* Flammable agent (fuel)
* Oxidizers (gas to support combustion)
* Source of ignition (heat)
## Footnote
Each component is essential for fire ignition.
136
What is the primary responsibility of the anesthetist in the operating room?
Patient's safety
## Footnote
The anesthetist plays a crucial role in preventing operating room fires.
137
What are the toxicants produced by fires in the operating room?
* Carbon monoxide
* Ammonia
* Hydrogen chloride
* Cyanide
## Footnote
These substances can harm airways and lung tissues.
138
What percentage of fires in patients occur IN the airway?
28% to 40%
## Footnote
This statistic varies depending on the study referenced.
139
What is a common method to prevent fires during surgery?
Mix oxygen with air to keep inspired oxygen concentrations low
## Footnote
This reduces the risk of ignition.
140
What should be done immediately if a fire occurs in the operating room?
Call for help and extinguish the fire
## Footnote
Interrupt the fire triad by removing one of the components.
141
What is the best method to extinguish a fire on a patient?
Use a basin of saline or smother with a towel
## Footnote
This method is often the most rapid and effective.
142
What should be done with the endotracheal tube during an airway fire?
Extubate the trachea
## Footnote
This removes the source of fuel and oxidizer.
143
True or False: Operating room fires often produce enough heat to activate the sprinkler system.
False
## Footnote
OR fires seldom get hot enough to trigger sprinklers.
144
What should be avoided regarding patient hair before surgery?
Hair spray
## Footnote
It is flammable and increases fire risk.
145
What are some flammable anesthetic agents that have been discontinued in the U.S.?
* Diethyl ether
* Cyclopropane
## Footnote
These agents posed significant fire risks.
146
Fill in the blank: An oxygen enriched environment allows materials to burn at a much _______ temperature.
lower
## Footnote
This increases the risk of fires in the OR.
147
What are some sources of ignition in the operating room?
* Static electricity
* Electrical equipment
* Electrosurgical cautery units
* Lasers
* Fiber optic light sources
## Footnote
These sources can lead to fires if not managed properly.
148
What should be done with flammable substances in the operating room?
Store them away from ignition sources
## Footnote
This minimizes the risk of fire.
149
What is the recommended oxygen delivery method for spontaneously breathing patients?
Use air only if possible
## Footnote
This minimizes flammability and risk during surgery.
150
name 3 gases that support combustion:
air
oxygen
nitrous oxide
151
if a fire occured in the airway and I extubated the patient, can i oxygenate them now?
yes because the source of fuel and oxidizer have been removed from the airway and it should stop burning
152
whats the moral of this whole damn lecture
avoid open mask anesthesia
no open oxygen
153
