Chapter 18 - spine sx Flashcards
What factors are you looking for in deciding if patient will be difficult intubation and difficult ventilatoin? What is your goal with intubation in a patient with cervical stenosis?
Goal: minimize neck movement with mask ventilation and laryngoscopy + intubation
Factors for difficult ventilation:
- MP3 or 4, OSA, snoring, edentulous, neck circum > 40 cm, short + stocky neck, large beard, large tongue, prior history
Factors for difficult intubation:
- MP3 or 4, OSA, neck circum >4 cm, poor cervical ROM, unable to assume sniff position, large tongue, TM < 6cm, poor upper lip bite, poor submandib compliance (head/neck radiation), interincisor distance < 3 cm, prior history
does severe cervical stenosis necessitate awake FOB? what is your goal with intubation?
Goal: minimize neck movement with mask ventilation and laryngoscopy + intubation
Awake vs Asleep:
- indicators of difficult vent
- indicators of difficult intub
- cooperative vs uncooperative
- full stomach
- large amount of secretions or blood or debri (trauma patient; will obscure FOB view)
Asleep
- consider if patient not full stomach + does not have predictors of difficult ventilation
- use glidescope to minimize neck movement (or glidescope assisted FOB)
- manual in-line stabilization (if not in C-Collar)
how is chronic pain managed during spine surgery (how would you manage patient in pre-op period and intra-op period)?
Preop
- if patient on chronic pain meds, tell patient to take their usual pain meds
- Patients who fail to take their chronic pain meds:
- calculate daily oral morphine equivalent, and provide some opiod morning of surgery
- multi-modal analgesia: gabapentin, celebrex (if allowed by sx), long acting opioid
Intra-op
- methadone or ketamine -> shown to reduce pain 48hrs post-op
- methadone - 0.2 mg/kg IV
- ketamine - 0.5mg/kg IV + infusion 10 mcg/kg/min intraop (stop at closure)
- use
Describe SSEPs and MEPs
SSEPs
- integrity of dorsal columns of spinal cord
- stimulation delivered on a peripheral nerve, sensed at cerbral cortex
MEPs
- integrity of anterior spinal cord (motor tracts)
- stimuli delivered at cerebral cortex, sensed at peripheral motor nerve
- cannot use NMBD
- very sensitive to anesthesia
what could loss of neuromonitoring signal represent (loss of signal at surgical site, loss of signal at non-surgical site, global loss of signal)?
neuromonitor signal loss: dec amplitude, inc latency
Surgical site signal loss:
- ischemia from trauma
- compression
- transection
non-surgical site signal loss:
- check position of affected limb (nerve compression, arterial compression) 2/2 positioning of patient
global loss of signal:
-
anesthetic overdose
- high volatile anes conc, bolus of IV agent, muscle relaxant
- hypotension
- severe anemia (decrease O2 tissue perfusion)
what does propofol, volatile anes, etomidate, and ketamine do to waveform amplitude and latecy of neuromonitoring?
Propofol + volatiles anes
- increase latency, dec amplitutde
Etomidate + ketamine
- no change in latency, inc amplitutde
What will your anesthesia plan be for patients undergoing neurophysiologic monitoring (SSEPs, MEPs, or both)?
goal - constant depth of anesthesia
- serve as baseline neuromonitoring signal
MEPs more sensitive to anesthesia
Maintenance
- amnesia, unconsciousness, autonomic control -
- low dose volatile anes (MAC < 0.7 - 0.5)
- or low-mod dose propofol infusion
- analgesia + reduce anesthetic conc
- opioid infusion (remi) -> does not affect monitoring
- muscle relaxation
- SSEP -> provide
- MEPs - > do not give
- during intubation, use sux or antagnoize Roc before baseline signal obtained
- IV boluses during sx
- avoid; let OR team know if you have to give
what are considerations for prone positioning in a patient undergoing spine surgery?
1) Neutral position of cervical spine
* maintain neck in neutral position with foam headrest or cervical traction devices
2) eye and ear pressure
- avoid turning face to one side
- assoc with blindness and stroke
- frequent checks of eye and ear position q30-60 min
3) Arm positioning (minimize brachial plexus injury)
- c-spine surgery -> arms secured at sides
- lumbar surgery -> superman; arms positioned at 90degres in all planes, arm boards, avoid excessive abduction
4) abdomen and breast protection
- bolsters from tip of shoulders to iliac crest
- decrease pressure of breast and abdomen (hang freely)
- allows for venous return and diaphragmatic excrusion during ventilation
patient is undergoing spine surgery, and the surgeon asks you for induced hypotension to minimize blood loss. would you do this? are there other ways to minimze blood loss?
- brain and spinal cord autoregulate b/w 50 - 150 mmHg
- pathology may disrupt autoregulation -> blood flow becomes pressure dependent
Induced Hypotension
- cardiac ischemic injury
- ischemic optic neuropathy (esp in prone position)
- end organ hypo-perfusion
- cause reigonal ischemia to surgical site (esp since autoregulation may be disrupted)
minimize blood loss
- consier antifibrinolytics
What is context sensitive half-time? How would you use your knowledge of propofol pharmacology to ensure a rapid but safe emergence?
context sens half time
- time it takes to decrease plasma concentration of a drug by 50% after a steady-state infusion has been turned off
- Propofol - turn off approx 40 minutes before surgical finish (if this was a long procedure)
- keep in mind, propofol does not cause muscle relaxation -> self extubate in prone position
- Can use EEG to give some insignt into tapering anesthesia.