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Week 5 Chemistry/Physics
Class Outline

I. Issues of safety in the operating room:

  1. Ohm’s Law and principles of electricity: Ohm’s Law is E = I x R where E is electromotive force, I is current, and R is resistance. This law of electricity can also be used for fluids with a slight variation. Q = Delta P/R where Q is flow, Delta P is change in pressure, R is resistance. This law has significance in that if forms the basis for the physiological equation for BP where
  2. BP = CO x SVR

  3. Direct and alternating currents: Direct current (DC) electrons flowing through a conductor always flow in one direction. i.e. Batteries. Alternating current (AC) or the wall outlet – alternates the direction of current between positive and negative 60 x per second. Watt is the amt of electricity work being done per unit of time. One watt = E X I where E is volts and I is current. A watt is the product of voltage and amperage. Wattage can be used for a term to measure work and heat produced in electrical circuit. Wattage = square of amperage x resistance. You can calculate amps if you know the volts and current. A 60 watt Light bulb on 120 volt circuit = ½ amp of current to operate since 60 is divided by 120. Another measure to consider is the amt of electrical work being done in terms of the joules. Ohm’s Law will apply only to DC not AC since AC has more complex form of resistance known as impedance. Impedance is the sum of forces that oppose electron movement in AC circuits. Ohm’s Law for AC is E = I x Z where Z is impedance which is measured by resistance plus capacitance. An insulator is a substance that opposes the flow of electrons and therefore has high impedance to flow. It is the opposite of conductor. A conductor allows the flow of electrons. Current is the flow of electrons in one direction. Capacitance consists of 2 parallel conductors separated by an insulator and has an ability to store a charge. It can measure the substance’s ability to store a charge. A battery or DC is a source of power. 2 plates with an insulator in between. The circuit is not complete so no discharge of stored energy. When you attach a conductor it will then complete the circuit and have DC. AC flow will not need anything to complete the circuit.
  4. Shock hazards: Macro: Large amt of current – experienced at body surface through intact skin. Severity is r/t density of current, amt of contact time and resistance of skin (i.e. – wet or dry skin) and Micro: Small amts of current directed through a conduit – sources such as an indwelling IV, temp pacer wire, swans. It needs a source to direct it through the body to the heart. You may not even notice if you received these shocks.
  5. Types of shocks: Sensations – 60 hertz AC for 1 second

    1 milliamp = macroshock – tingling

    10-20 mamp = "let go threshold" when exceed 20 mamps – muscle contract and can’t let go

    50 mamps = pain

    100-300 mamps= Vfib (possibly) – resp system remains intact

    6000 mamps = or 6 amps = sustained myocardial contraction, temp resp paralysis and if current density is high enough will burn.

    Micro:

    100 microamps = Vfib

    10 microamps – max Number that machine can leak into environment. If machines leak more than that they need to go get fixed.

  6. Concepts of power grounding: Grounding to electrically oriented people means grounding electrical power where in the OR grounding is of electrical equipment. Differences btw power equipment – power supply at home is grounded, in the OR it is not grounded. All equipment and not the power supply in the OR are grounded. Normally power is grounded – place to ground to is earth. Hospital is not earth grounded but equipment is grounded. If power in the OR were grounded to earth then anyone in the room could complete the circuit and become grounded. If the patient were to become grounded would receive shocks.
  7. Grounding pads for the electrocautery machine – the pad is placed on the pt’s thigh usually to prevent them from being grounded. It needs to be a large surface area to dissipate the heat and you must look at the site and monitor it for burns.

  8. Line isolation monitors: In the OR it monitors the integrity of source of power. It will alarm when power flows to ground at 2-5 microamps. If it leaks more than that it will throw off the circuit breaker. It means a piece of equipment is not working well so you must find the piece of equipment. The alarm could also be a result of the cumulative affect of all the pieces of equipment plugged in and each one having a small leak. If this happens then unplug the unessential pieces. Each OR has its own system. The patient is the most vulnerable in the room for suffering from shocks. The alarm doesn’t necessarily mean that current is flowing but that there is a potential flow and there are affects if it leaks. The patient grounding pads are so large to increase the surface area that current passes through. If the area is small the current would cause a burn. "Is patient grounded" Means that you are isolating the pt from being grounded to ground which would complete the loop so it goes through the pad and to the machine rather than using the pt as the ground.
  9. Current flow: ECG, pacemaker, MRI, CAT scan, fluid and invasive monitors, peripheral nerve stimulators, defibrillator:
  10. Patterns of nerve stimulation: There are two types of neuromuscular blockers used 1. Depolarizing blocker and 2. Nondepolarizing agent.
  11. The depol agent is succinalcholine which mimics acetylcholine. It is 2 ach molecules bound together. It comes on fast and goes off fast.

    The nondepol come in 3 flavors. They are slow to work and slow to wear off and are variable with each pt. 1. Short, 2. Intermediate, 3. Long. Terms determine how long they work

    1st nondepol was curare, detubocurare is long acting, rockuronium works faster and is intermediate acting 80-95 dose should last 45 minutes to one hour, vecuronium is intermediate, pancuronium is pavulon, is long acting and is cheaper, mivacurium is short acting, slow onset, rapid metabolism, is broken down by pseudocholinesterase in the blood and can get a large histamine release; cisatricurium is interm – special in that it isn’t metab like the rest but is broken down by Hoffman’s elimination thus is used in pt’s with renal disease.

    The actual nerve stimulators: Use the ulna most frequently with wrist pads. Can use tetanus or TOF (Train of Four) The depol agent will give you twitches 30 sec after the agent, you should see tetany (sustained muscle contraction) Causes general depol of all skeletal muscles which causes a contraction. Will not have tetany for succs until after 5-6 minutes. With the nondepol 30minutes later will have "fade" 1st electrical stim will give a good response then the next 3 stims will be less since there is a partial blocking at the neuromuscular junction. Succs will never have fade. It is an
    "all or none" response. The TOF complete depol of al and have no twitches until after 5-6 min and then see all 4 twitches back and no fade. Succs uses the TOF and even if sees 4/4 twitches can still have 70% of neuro blockade. Judge the extent of block by the depth of breathing and you can always reverse with anticholinergic agents, which moves the drug off the ach receptor sites. Can use the facial nerve at temple or ulna nerve, which is a closer indication of diaphragmatic blockade. The diaphragm will come back before the ulna and facial nerves. IN order to give a reversal agent you must have a least one twitch back and no longer need muscle relaxation. If you give the reversal without any twitches you can further the block.

  12. Principles of defibrillation: Use joules which is power in watts x seconds. The most effective time to defib is at end expiration since there is less resistance and if using ventilator will have more control over breathing. With each subsequent defib the resistance decreases by 10%. With each defib myocardial muscle sustains more damage. Must be aware of this and know that if the pt received multiple shocks will probably need inotropic support especially in the heart room and coming off bypass pump. The proper placement of electrodes are ant/post – higher success rate but this position can be modified if need be. Usually don’t need to defib anyone except in Cath lab with AICD insertions, pacers. Can have pt awake or asleep.
  13. Lasers: Must know the type of laser being used and what the appropriate eye protection is. Different lasers absorb different things. LASER = light amplification by stimulated emission of radiation.
  14. Argon lasers – show up as blue-green. The Hgb in pigments absorbs it. It is used for eye surgery since it is poorly absorbed by water and can then be used for the vessels in the back of the eye – it can be used to irradiate tissue and hgb since it isn’t absorbed by vitreous of the eye.

    CO2 laser – mostly used for ENT surgery – emits infrared beam, which you can’t see so they’ve put Helium/Neon laser with it, which emits a red beam (aiming beam), tissues poorly absorb He/Ne. CO2 is very precise, almost no blood loss. The heat generated produces immediate coagulation and it creates minimal edema, which is important in airways. CO2 is absorbed by water in all tissues.

    Yag laser – works can penetrate tissues deeper than CO2 laser. Used for gyn procedures – lap and regular abd. It is absorbed by dark tissue not by water. It also has no color so the He/Ne is added for the infrared siting device.

  15. Hazards of laser use: Must cover the pt’s eyes with wet NS or H2O soaked gauze. Must also wear goggles for you.
  16. CO2 – wear pink glasses or clear plastic

    Yag – wear brown or dark color glasses such as green

    Argon – yellow colored glasses

    Must also wear a highly filterable mask esp if they are doing gyn surgery to laser off venereal warts or cancerous tissue since there is a plume of laser produced here and you don’t want to breathe in this plume of viral disease or cancer.

  17. Anesthetic care of patients during laser surgery: If pts are having ENT laser surgery you should use an ETT specific for laser surgery. The laser tube contains a cuff that you fill with NS or water and blue dye in it so you can see it if the cuff leaks. If this happens then reduce the FiO2 to minimum you can for pt tolerance. If after all this you still have an airway fire then:
  18. Airway fire management: Turn off O2 source. Flood the area with irrigation and suction and remove the burning plastic thing in the trachea. Reintubate and bronch and lavage. Avoid using N2O since it can propagate a fire. PVC is very flammable and will have flame and smoke. This is detectable right away so you flood the field. The pt will have a very sore throat like an inhalation burn from a fire.
  19. Operating room fire management:

II. Introduction and Review of Organic Chemistry

  1. Carbons - has 6 electrons and 6 protons. It usually shares its electrons with other elements and it forms covalent bonds. Carbons are the basis for organic chemistry. Carbons bond easily with hydrogen hence the name hydrocarbons. The simplest of these is methane, which is one carbon bonded to 4 hydrogen. Carbon is in the second row of the periodic table and thus has 2 electrons in its inner most shell, the outer shell has only 4 electrons and to fill its outermost shell needs 4 more electrons. It can then bond with 4 other things here or share its electrons with 4 other things. Usually reactions involving carbons are slow and complex with lots of secondary reactions occurring at the same time. Organic solutions are usually nonionic and are therefore poor conductors or are nonconductors. The properties of each substance involved with carbon will depend on the # of carbon molecules, the types of bonds present, and the types of side chains of functional groups breaking off the carbons.
  2. Bonding – is the holding together of atoms that compose molecules
    1. Covalent is where electrons are shared to complete the outermost shell. It is a loose bond and can have reversible complexes, can be single where a single pair of electrons are shared btw 2 atoms like in methane, CH4; double where there are 2 pairs of shared electrons like in ethylene, C2H4; or triple where there are 3 pairs of shared electrons like acetylene, C2H2. Single bonded things are the least active chemically. Double bonds are more reactive but then are also more volatile. Triple bonds are the most reactive and the most volatile. Covalent bonds result in creating compounds that are insoluble in water. Usually nonpolar with weak intramolecular forces and have low melting and low boiling points.
    2. Ionic bonds – substances will dissociate into anions and cations. These solutions tend to be capable of conducting a charge.
    3. Van der Waal’s forces – where center of one nuclei attracts electrons of another so one end tends to be more – and one end more +
    4. Hydrogen – H atoms lose electrons and become charged + therefore it makes it easier to attract other molecules to their charge.

Strongest bond is covalent then hydrogen and equal ionic and van der Waal’s

  1. Structural and empirical formulas – The simplest of hydrocarbons is methane. A formula can be used to figure out the alkanes, which are single bonded hydrocarbons. C = 2 x H + 2 or CnH2+2.
  2. Know the prefixes for first 8

    Methane CH4

    Ethane C2H6

    Propane C3H8

    Butane C4H 10

    Pentane C5H12

    Hexane C6H14

    Heptane C7H16

    Octane C8H18

 
  1. Saturated vs unsaturated hydrocarbons- the alkanes are saturated since all the carbons have formed single bonds with the hydrogen or other functional group. Alkenes have a carbon-carbon double bond. Their formula is CnH2n. This can be a ring structure. Alkynes have a carbon-carbon triple bond with the formula CnH2-2. Unsaturated hydrocarbons are more reactive and will result in the splitting of a bond – can then add a functional group on each carbon. If you take ethylene, C2H4 and add bromide would get the double bond to break and would end up with C2H4Br2. A substitution reaction involves single covalent bonds where one atom replaces a functional group with another.
  2. Isomers – have the same molecular formula but different physical and chemical properties and the structural layout is different. The structural relationship is similar. This is possible since carbon can rotate about its central axis, which then appears to change the position of the bond. There are several types of isomers.
    1. Structural which differ in both physical and chemical properties
    2. Stereoisomers which have similar structure but differ in spatial relationship
    1. Optical – groups attached differ from one another this causes them to bend or rotate. Compounds that are able to rotate a plane of polarized light – if it bends to the right it is dextro and to the left it is levo-rotary. The two images are mirror images of each other. If a gas is a mixture of both it will stay straight and not bend.
    2. Geometrical – formed by 2 hydrocarbons joined by a double bond, which locks carbon so no axial rotation can occur. Cis means the functional groups are on the same side either both above or both below, while trans means they are opposite each other diagonally
  1. Aromatic compounds- Structure is related to the benzene ring which is a C6 ring configuration containing 3 double bonds that oscillate the electron sharing between the carbons. This is the difference from other alkene compounds. To join the benzene ring to form polynuclear aromatic compounds phenanthene has 3 benzene rings and is r/t morphine . The catechole structure is a benzene ring with 2 –OH groups coming off one side. This is the basis for norepi and epinephrine.
  2. Alicylic compounds – refers to any ring configuration different from benzene - refers to cyclopropane. It has a different ring structure than a benzene ring but this can have a ring of 3 carbons with just 2 H attached to each C

 

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