Complex Spinal Cord Surgeries: D-Wave Monitoring

D-Wave Stimulation is Anodal or Cathodal?

Anodal around the C or FC line. Can be quadripolar.

D-Wave Intensity

Up to 100V (usually 150-250 V)

D-Wave Pulse Width

50-75 usec, max 500 usec

D-Wave of Pulses

1

D-Wave ISI

N/A because one train

D-Wave Frequency

1 Hz

D-Wave decreases 30-50% and TceMEPs are stable

No deficit

D-Waves decreases 30-50% but MEPs are lost

transient deficit

If D-Wave is decrease by more than 50% and MEPs are lost

permanent deficit

What should an NP do if their D-Waves attenuate

Any decrease in D-Wave should be reported and MEPs should be ran

What is the impact of inhalational agents on D-Waves?

They are resistant to inhalational agents

What is the impact of muscle relaxants on D-Waves?

Might be beneficial to D-Wave signals as they will quiet scalp muscle activity

How does TIVA (propofol and a narcotic such as fentanyl) affect D-Waves?

TIVA is the preferred anesthetic regimen, especially when TceMEPs are also being run, this case make sure to ask anesthesiologist for bite block. Boluses will not negatively impact D-Wave signals (not generated in synapses)

What morphology would you expect to see in the D-Waves of a patient with an intramedullary spinal cord tumor?

Desynchronized; this will make running signals too unreliable and thus impossible.

What morphology would you expect to see in the D-Waves of a patient with post radiation myelopathy?

Desynchronized; this will make running signals too unreliable and thus impossible.

Can you run D-Waves when there is extensive dural scar tissue on the cord?

No as you will not be able to place electrodes.

What do you expect to see in regards to D-Waves during a scoliosis correction surgery?

Amplitude changes that do not actually represent significant changes.

What additional modality do you need to run when monitoring a scoliosis correction surgery with D-Waves?

TceMEPs; they will help determine if amplitude changes in the D-Wave are actually significant during cord placement manipulation.

What should the NP offer when both D-Waves and TceMEP amplitudes are attenuated during a scoliosis correction surgery>

Stagnara Wake up test to see if patient is paralyzed.