Somatosensory Evoked Potentials (SSEP) Flashcards

Which filter settings are typically used for intraoperative SSEP recording?

Answer: 30–3000 Hz bandpass

SSEP recordings typically use a bandpass filter of 30–3000 Hz to capture the relevant frequency components of evoked potential waveforms while reducing low-frequency drift and high-frequency noise.

What is the recommended number of averages to obtain a reliable SSEP waveform in the operating room?

Answer: 200–500

Typically 200–500 sweeps are averaged intraoperatively to achieve an acceptable signal-to-noise ratio for SSEP waveforms.

Bilateral loss of SSEP signals with preserved baseline recordings most likely indicates:

Answer: A systemic physiological change such as hypotension or hypothermia

Simultaneous bilateral SSEP loss typically suggests a systemic cause such as severe hypotension, hypothermia, or anesthetic changes rather than a focal surgical injury.

Which anesthetic agent has the least suppressive effect on cortical SSEP amplitudes?

Answer: Propofol-based total intravenous anesthesia (TIVA)

Propofol-based TIVA has the least suppressive effect on cortical SSEP amplitudes compared to volatile inhalational agents, making it preferred for cases requiring sensitive monitoring.

The stimulation rate for median nerve SSEP should avoid multiples of 60 Hz to prevent:

Answer: Electrical line noise contamination

Stimulation rates that are multiples of 60 Hz can alias with power line frequency, contaminating the averaged SSEP with electrical noise rather than canceling it.

During prone positioning for spinal surgery, SSEPs are lost immediately after positioning. The most appropriate first step is to:

Answer: Check for brachial plexus stretch or peripheral nerve compression at pressure points

Immediate post-positioning SSEP loss most often results from peripheral nerve compression or brachial plexus stretch due to improper positioning rather than spinal cord injury.