In this 174th episode I welcome back Dr. Gillian Isaac to discuss another 2 highly tested ABA keywords, OR fires and electrical safety in the OR.
CME: https://earnc.me/Adkacw
OR Fires
Fire Triangle (2:52)
Most important aspect of OR fire management? (3:22)
Risk for airway fire during laser resection of tracheal tumor DECREASED in
A. CO2 rather than GAD laser
B. Helium > 60%
C. N2O > 60%
D. PVC ETT
E. Halothane in mixture
Discussion (5:24)
Reasons for selecting cuffed ETT over uncuffed include all of the following except
A. Few intubations w/ ETT needed
B. Less chance for airway fires
C. Spontaneous breathing easier
D. Aspiration of gastric contents less likely
Discussion (7:53)
Reduction of airway fire during laser surgery of airway best accomplished by use of
A. Continuous mode laser emissions
B. Nitrous oxide, opioid, relaxant technique
C. PVC ETT and cuff
D. Topical lido
E. Saline filled sponges over exposed tissues
Discussion (9:41)
During surgery CO2 lasers, which inhaled gas mixture is least likely to promote combustion of endotracheal tube?
A. O2 25%, He 75%
B. O2 25%, N2 75%
C. O2 25%, N2O 75%
D. O2 50%, N2 50%
E. O2 50%, N2O 50%
Discussion (10:38)
What to do in airway fire? “Stop O2” or “pull ETT”, which first? (12:03)
During laser microsurgery of larynx w/ ETT, fire occurs in airway. Most appropriate initial management?
A. Decrease FIO2
B. Saline into ETT
C. Perform cricothyroidotomy
D. Remove ETT
E. Ventilate w/ air
Discussion (13:32)
During laser excision, dark smoke suddenly appears in surgical field. Trachea intubated, anesthesia maintained w/ halothane, nitrous, oxygen. Most appropriate initial step?
A. Change gas to air
B. Fill oropharynx w/ water
C. Water into ETT
D. Remove ETT
E. Ventilate w/ CO2
Discussion (14:06)
Two hours after sustaining burn to head/chest/neck, patient has stridor and difficulty breathing. Most appropriate initial management?
A. Admin aerosolized norepinephrine
B. Admin helium oxygen
C. Intubate
D. Admin dexamethasone
E. Tracheostomy
Discussion (15:15)
Laser safety eye protection for OR staff needed. Clear wrap around goggles adequate with what kind of laser?
A. Argon
B. Nd-YAG
C. CO2
D. None of the above
Discussion (16:39)
Of the following lasers, which penetrates tissue most?
A. Argon
B. Helium neon
C. Nd-YAG
D. CO2
Discussion (17:11)
If you plug in bear hugger, and LIM goes off, what should you do? (22:43)
Which of following is indicated by an alarming LIM?
A. Electrical shock to patient
B. Power surge in main hospital supply
C. Disconnection of patient to electrocautery grounding pad
D. Overload of OR circuit
E. Presence of current leak between OR electrical device and ground
Discussion (23:15)
Line isolation monitor
A. Prevents microshock
B. Prevents macroshock
C. Provides electrical isolation in OR
D. Sounds alarm when grounding occurs in OR
E. Provides safe electrical ground
Discussion (24:13)
Which of following causes LIM to alarm?
A. Discharge static electricity
B. Flow of current to ground in isolating circuit
C. Interruption of current to electrical outlets caused by circuit breaker
D.Total electrical current exceeding circuit capacity
Discussion (24:38)
In the OR
A. Conductive floors necessary for electrical safety
B. ECG monitors may be used as grounding source
C. Improperly grounded electrocautery causes VF
D. Isolation transformer offers no protection against micro-electrocution
E. LIM will interrupt power automatically when excess leakage to ground detected
Discussion (25:17)
Minimum macroshock required to deliver defibrillation
A. 1mA
B. 10 mA
C. 100 mA
D. 500 mA
E. 5000 mA
Discussion (27:38)
Fundamental difference of macroshock vs microshock?
A. Location
B. Duration
C. Voltage
D. Capacitance
E. Lethality
Discussion (28:38)
Leakage current and microshock hazards has been eliminated by
A. Isolation transformer
B. Conductive flooring
C. 3-wire grounding system
D. LIM
E. None above
Discussion (29:45)
Reason patient not burned by return of energy from patient to Bovie?
A. Coag side is + relative to ground side
B. Resistance in body attenuates energy
C. Exit current density much less
D. Overall energy delivered too small
Discussion (31:39)
Which of following decreases risk for burns during Bovie?
A. Conductive flooring
B. Grounding of patient to OR table
C. Increase resistance of current at return electrode
D. Isolation of current output of ESU
E. Replacement of return electrode at distance from surgical site
Discussion (32:15)
After removing electrocautery pad from thigh, burn noted. Which of following most likely contributed to injury?
A. LIM fault
B. Leak from ECG module
C. Defective grounding of ESU
D. Dry gel on pad
E. Excessive current settings
Discussion (33:19)
Burn found at site of Bovie pad. Which of following most likely?
A. ESU in bipolar mode
B. Pad partially detached
C. ESU line severed
D. LIM alarm that patient became grounded
Discussion (33:51)
Outline by Dr. Brian Park
See other interactive posts
I have listened to every keyword episode more than once and find them extremely helpful for test prep – thank you both! The one thing I would request is for Dr. Isaac to not stop Dr. Wolpaw from talking through how he thinks about the questions she poses. Hearing his thought process is incredibly valuable but she often starts commenting before he can completely finish.
Just to clear since the numbers confused me, and I had to go and check clinical anesthesia:
0.01 mA max recommended micro shock
0.1 mA VF with micro shock
0.5-1 mA perception threshold (t)
10-20 mA Let go t
50 mA pain and injury t
100-300 mA Vfib t
6000 mA disaster t
Thank you.
Just a little comment for one of the question.
Which of following decreases risk for burns during Bovie?
A. Conductive flooring
B. Grounding of patient to OR table
C. Increase resistance of current at return electrode
D. Isolation of current output of ESU
E. Replacement of return electrode at distance from surgical site
I think the answer is D.
Most ESU now have isolated output. This means that the ESU is not grounded. So if the patient touches the OR table (grounded), the current would not be able to flow through the table because it cannot complete a circuit with the ESU.
Here is my reference from Morgan & Mikehail’s (7th ed.) :
«The isolated output electrosurgical unit (ESU) is much less likely than the ground-referenced ESU to provoke burns at ectopic sites. […] Newer ESUs are isolated from grounds using the same principles as the isolated power supply (isolated output versus ground-referenced units). Because this second layer of protection provides ESUs with their own isolated power supply, the operating room’s line isolation monitor may not detect an electrical fault. […] Equipment casings—but not the electrical circuits—are grounded through the longest blade of a threepronged plug (the safety ground). If a live wire is then unintentionally contacted by a grounded patient, the current will not flow through the patient because no circuit back to the secondary coil has been completed. Of course, if both power lines are contacted, a circuit is completed, and a shock is possible. In addition, if either power line comes into contact with a ground through a fault, contact with the other power line will complete a circuit through a grounded patient.»