Chem and Phys Test 1 Flashcards
Perioperative Heat Loss Timeframe
The patient core temperature drops the most in the first hour of induction.
Due to impairment of vasoconstriction and shivering responses.
Temperature stops dropping once it reaches 34.5 C
General anesthesia and temperature
Vasoconstriction is reduced and heat in the core moves to the periphery allowing core temperature to drop to anesthetic induced lowered threshold for vasoconstriction. Core to peripheral heat redistribution causes 0.5-1.55C drop in core temperature in the first hour of anesthesia
Thermoregulatory Vasoconstriction
Maintains temperature gradient between the core and periphery between 2-4C. Core (head, chest, and, pelvis) is insulated from environment by peripheral compartment
Most significant process in which patients experience heat loss during anesthesia
Radiation; accounts for 60% of heat loss
Which type of heat loss occurs when skin is prepped Chloaprep
Evaporation: warm heat from body causes liquid skin prep to turn to vapor.
Evaporation
Process in which liquid is changed to gas; requires energy to break hydrogen bondsBreathing causes heat loss through exhaled water vapor. Decrease gas flow rates, use humidification with patient who are intubated.
Complications of Hypothermia ( <35C)
surgical site infection due to impaired vasoconstriction and decreased blood flow to area dehiscence bleeding due to impaired coagulation ventricular ectopy delayed drug metabolism increased length of hospital stay higher blood transfusion rates impaired host defenses thermal discomfort
Newton’s first law of motion
A body at rest or moving at a constant speed in a straight line will remain at rest or continue in a straight line at a constant speed unless it is acted upon by a force
Newton’s second law of motion
Force = mass x acceleration
The rate of change of momentum of an object is directly proportional to the momentum of the force applied.
Newton’s third law of motion
Every action has an equal and opposite reaction
When one object exerts a force on a second object, the second object exerts a force that is equal in magnitude and opposite in direction
Heat loss
Transfer of energy from a higher concentration of the a lower concentration
Radiation
Charged particles are accelerated and release electromagnetic wavelengths. Heat is then transferred from body to cooler environment. Vasodilation effect of anesthesia causes increased blood flow from body’s core to periphery. Cover body surfaces not being operated on lessens heat loss.
Convection
Heat has higher kinetic energy and rises due to less density. Cold air lower energy molecules due to greater density. As heat rises from body, colder molecules fall and are heated by the body’s warmth; creating air currents. Heat is lost from the body and air is warmed. Decrease the temperature in the room.
Conduction
Heat is transferred from warmer object physically touching cooler object. Ex: warm patient body on cool OR table. Place warm blankets on OR table.
Standard measure of force
Newton; kg*meter/second^2
average gravity on Earth
9.80665 m/s^2
1 newton
force of 100,000 dynes, Ex: SVR, PVR measurement
Vectors
magnitude and direction displacement: distance with direction velocity: speed with direction acceleration: how quickly speed changes force
Scalars
magnitude only; volume density speed mass time temperature distance work pressure
Resultant
addition of 2 vectors; must take into account value and direction
Velocity
displacement/time, 0 if end at the same location
meter/sec
Work
Work = force x distance (or displacement)
Amount of energy necessary to move an object from one point to another
If work is done on you –> you gain heat
If you do work on something –> you lose heat
Unit: Joule = kg* m^2 / s^-2
(no change in volume/energy/distance = no work done)
penetrating injury damage depend on what 3 factors
- type of wounding instrument (knife, missile (bullet or fragment)
- velocity of the missile at time of impact
- characteristics of tissue which it passes (bone, fat, muscle, blood vessels, nervous tissue, organs)
Lower velocity wounds
inflict injury by lacerating and cutting tissue.
Moderate to high velocity wounds
result from deceleration of object as it passes through tissue, causing kinetic energy to transfer to surrounding tissue.
Most significant determinant of wound potential
velocity; bullet wounds have greater potential to inflict serious injury compared with a knife of handheld projectile
speed
distance traveled/time elapsed; m/s, mph
rate at which something moves of changes position
Blunt trauma injuries
Fractures, lacerations, external wounds, tearing by shearing forces, coup-contrecoup injuries
Pressure units
force/area; Pascal (Pa) = N/m^2
Gauge pressure
Pressure of a system above or below atmospheric pressure
Gauge pressure = total pressure -atmospheric pressure
0 reference point
1KPa
1000 Pa (Pascals)
1atm
101.3KPa
Second law of thermodynamics
Heat naturally flows from hot to cold; the only way for cold to flow to hot is via the addition of energy
Ex: Ball naturally flows from high position to low position at the top of a hill, but the ball cannot naturally go back up the hill
Change in entropy is > 0
Entropy
Natural processes move toward disorder; universal trend toward equilibrium; unidirectional
Low energy = energy concentrated
High energy = more spread out energy
Force
Push or pull required to produce an acceleration
Newtons or N
Kinetic Energy
Ability to do work; energy of motion
KE = 1/2 mv^2 (mass * speed)
Power
Rate at which energy is spent; rate of doing work
Power = work/time
Unit: Watts (W) = Joule/second
Syringe size and pressure
Syringe is an example of pressure generated by force over area
Pressure = force/area
Increase area over which same force is generated, decease pressure
Decrease area over which same force is generated, increase pressure
Barometer
tube closed at one end and open on the other; pressure of the atmosphere and the weight of mercury column = opposing forces. More air pressure = more force = increased height of mercury
P(atm) = density x gravity x height (pgh)
* Measure actual or absolute pressure
Total pressure = gauge pressure + atmospheric pressure
Manometer
U-shaped tube filled with a fluid of a known density; measures pressure difference
delta P = P (system) - P (atmosphere)
* measure gauge pressure
Bourdon Gauge
Used on gas cylinders; type of aneroid gauge bc they don’t use liquid.
Measure pressure difference btw pressure exerted by gas on cylinder and atmospheric pressure. Gas above atmospheric pressure enters coiled tube –> slight uncoil and pointer moves to show gauge pressure
*Measure gauge pressure
1 pascal
N/m2
Potential energy
stored energy
PE = mass * gravity * height
Ex: battery, plane in the air, chemical energy stored in food
Internal energy
kinetic energy + potential energy
First Law of Thermodynamics
Law of conservation of energy; energy cannot be created or destroyed
Third Law of Thermodynamics
Absolute; is considered void of energy, theoretically impossible to reach