Safety lecture Part 3

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Patient and Provider Safety in Anesthesia: Part 3:

Professor: Maribeth Massie, CRNA, MS, Ph.D.(c) ANE 507: Basic P rinciples of Anesthesia I Patient and Provider Safety in Anesthesia: Part 3

Radiation badges:

Radiation badges Luxel body badge contains sheet of radiation-sensitive aluminum oxide sealed in a light and moisture proof packet When atoms in the aluminum oxide sheet are exposed to radiation, electrons trapped in excited state until irradiated with a specific wavelength of laser light The released energy of excitation, which is given off as visible light, is measured to determine radiation dose

Luxel radiation badge:

Luxel radiation badge

Radiation badges:

Radiation badges The packet contains series of filters designed so the energy and type of radiation can be determined In order for the radiation type and energy to be determined, the dosimeter must be worn so that the front of the dosimeter faces towards the source of radiation Luxel body dosimeters are among most sensitive dosimeters available The minimum detectable dose is 1 millirem for x-rays and gamma rays and 10 millirem for energetic beta radiation. If a dose of "M" is reported, the total dose received was minimal, i.e., less than the minimum reportable dose

Guidelines for monitoring badge use:

Guidelines for monitoring badge use Never share your badges or wear another person’s badges. Each badge is intended to be worn by only the designated person Do not intentionally expose badges to radiation. Intentional tampering with badges is a very serious matter If you discover that your badges are contaminated, notify EHS promptly and request replacement badges No matter how curious you are, do not wear your badges when you receive a medical x-ray or other medical radiation treatment. Your badges are intended to document occupational dose, not medical dose

X-Ray exposure:

X-Ray exposure Goal is the ALARA principle: maintain exposure as low as reasonably achievable  time, distance, shielding X-Rays can cause DNA damage and be mutagenic Inverse square law explains how energy intensity decreases with distance Minimum recommended distance from X-Ray source is 6 feet Greatest intensity of X-Ray is directly in front of beam generator Stand behind or to the side of bean to lessen exposure Lead barriers, lead aprons, thyroid shields should be utilized

CT scan:

CT scan 10/17/2011 7 Useful to detect abnormal pathology (intracranial, intrathoracic, abdominal) and detect long bone, spinal, pelvic fractures and herniated discs Uses Xray beam in a tube; 2D, 3D, Spiral, Multislice, etc Does not interfere with monitoring Challenges: May need sedation to decrease pt movement Kinking/disconnect of airway circuit Inaccessibility to patient Use of ionizing radiation (cumulative over lifetime!) Allergic reactions to IV contrast dye

Iodine contrast media (ICM):

Iodine contrast media (ICM) 10/17/2011 8 HOCM: high-osmolar contrast media Contains few dissolved particles and iodine atoms Causes fluid shift from cell to vein LOCM: low-osmolar contrast media Contains greater numbers of dissolved particles with iodine Less fluid shift from cell since iso-osmolar Causes fewer allergic reactions…more expensive

Allergic reaction to contrast dye:

Allergic reaction to contrast dye 10/17/2011 9 <10% of patients receiving IV contrast experience allergic reaction Allergy to shellfish or seafood more prone to reactions Method of injection (slow or bolus), type of dye used and dose

Treatment of allergic reactions:

Treatment of allergic reactions 10/17/2011 10 Supportive care for mild reactions: Diphenhydramine 0.5-1 mg/kg or 50-100 mg IV Moderate to severe reactions: Fluids (1-5 liters LR) 100% Oxygen Epinephrine 10-100 mcg IV bolus for hypotension; 0.1-0.5 mg IV for cardiac collapse; gtt 0.05 -0.1 mcg/kg/min IV titrated to blood pressure Norepinephrine /Dopamine/ Dobutamine gtts Aminophylline 5-6 mg/kg IV over 20 minutes Sodium bicarbonate 0.5-1 mEq /kg Corticosteroids: Methylprednisolone 1-2 gm, hydrocortisone 0.25-1 gm (research shows no help in acute anaphylactoid /anaphylactic reactions)


MRI 10/17/2011 11 Radiofrequent pulses in cylindrical large-bore magnet surround the patient, rotate protons into transverse plane and produce image Nuclei of certain atoms absorb or emit radiation Hydrogen atom selected because 70-85% of human cells contain water and also contains one proton and one electron Electron spin aligns atoms parallel to magnetic field Patient’s water-containing tissues are exposed to radiofrequencies and proton emits energy as observed via 3-D spatial information Magnetic strength is measured in tesla (T); a typical scanner is approximately 1.5 tesla (range 0.3 – 4 T) 1 T = 10,000 gauss or oersted The force of the field is greatest and is homogenous at the center of the scanner; the area of maximal force is about the size of a basketball

Magnetic Field :

Magnetic Field As the distance to the bore decreases , the force of the field increases exponentially

Challenges :

Challenges No ferromagnetic objects can be in the Suite  lethal projectiles Implantable ferromagnetic devices: older cerebrovascular clips, surgical clips and pacemakers (newer ones can become disabled) Cochlear implants, prostheses, plates, wires, screws “NICS” Inaccessibility to patient Can stay in room but very loud (60-90 dB); may have to wear ear plugs No known emission of radiation and studies show magnetic fields <2.5 T do not cause adverse effects Electronic instruments may not function properly Remove watch, credit cards, beeper, stethoscope


Challenges Pregnant providers should not be in room Some studies found that the radiofrequent pulses could raise the temperature of the fetus to unsafe levels Morbidly obese patients may have difficulty dissipating heat and have an unsafe rise in temperature also Infants may become hypothermic; ask tech to turn fan off and place hot packs SAFELY on patient Patients with programmable shunts will need to arrange to see neurosurgeon or EP tech post-procedure Implantable insulin pumps may become nonfunctional If need to conduct CPR, quickly move patient outside of MRI suite so as not to create lethal projectile action

Monitoring in MRI :

Monitoring in MRI 10/17/2011 17 Only use MRI compatible monitors!!!! EKG Blood in the major vessels, most specifically the aortic arch, can act as a conductor With each systole blood moves rapidly around the aortic arch inducing a small current Although probably not clinically significant, this current can register on the EKG and manifest as alterations in the ST segment and/or peaked T waves Place leads close to magnetic center and to one another Twist/braid cables helps to minimize changes from magnetic field Blood pressure Remove all metal connections from noninvasive cuff Arterial catheters must pass through a radiofrequency filter Dampening of the waveform reduced when transducer < 1.5 meters from patient Blood flow decreased by magnetic field  compensatory rise in BP

Monitoring in MRI:

Monitoring in MRI Pulse oximetry Signal may be distorted Burns Place probe as far away from site scanned as possible Capnography Follow trends; waveform may show prolonged upstroke and decreased value


Quench MR scanners are supercooled with inert gases such as helium; if these cryogens escape either intentionally or unintentionally, a quench has occurred. Usually done in an emergency to remove projectile from scanner Can happen spontaneously Occurs over 5 -15 seconds thus magnetic field does not drop immediately If a quench should occur but the cryogens should not exit via the designed pressure valve, the most immediate risk to occupants of the room is asphyxiation and frost bite Later  fire hazard as flammable liquid oxygen develops with the rapid drop in room temperature


Quench Don’t touch Quench button! If an unanticipated quench should occur, retrieve and stabilize the patient, then evacuate the MR site immediately. For an anticipated quench, be certain it is indicated, push the indicated button and evacuate the room immediately.

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