BIS monitor after Anesthesia and it’s awesome

Post Anesthesia monitoring is must be required

1. BIS and Neurophysiological monitoring Moderated By: Presented By: DR.A.SASHANK DR.SHALU KUSHWAHA

2. Neurophysiological monitoring Also called ( IONM ) intraoperative neurophysiological monitoring. Refers to the use of specialized techniques to asses the functional integrity of the nervous system during surgeries like brain spinal cord and peripheral nerves . Why we need IONM : Prevent neurological injuries during surgery. Detect early signs of damage to nerve and neural structure. Guide the surgeon in real time for safer outcome.

3. Common surgeries where IONM is used : Spine surgeries ( scoliosis correction, disc herniation) Brain tumor resection Carotid endarterectomy Aneurysm clipping ENT procedures ( Acoustic neuroma) Peripheral nerves surgeries

4. Brain Spinal cord 1.Motor mapping 2. Sub cortical mapping MEP SSEP

5. Different modalities for IONM : Modality Monitor Motor evoked potential (MEP) Motor tracts Spine/ tumor surgery Somato -sensory EP (SSEP) Sensory pathway Spinal surgery Brain stem auditory EP (BAEP) Brain stem function Acoustic neuroma Electromyography nerve root / muscle Nerve decompression EEG Brain cortex Brain surgeries

6. Motor mapping :

7. E voked potential basics : Stimulation electrode : corkscrew electrode Enter directly into scalp Recording electrode : inserted into muscles depends on the myotome. C5 – Deltoid L4-L5 - Tibialis anterior L5- S1 – Gastroneumus , adductor hallucis lon gus Mechanism : Stimulate Corticospinal tract individual muscle

8. Motor evoked potential : 10- 20 system : Centre point is CZ Left side is odd number right is even number. Identify the center point and stimulate C3 and C4 MEP setup : Each signal goes in a train The train overcome inhibition so the action potential can cross synapse. Each individual muscle will generate a particular wave. Upper limb latency will be shorter than lower limb latency. If amplitude decreases >50% or latency >10% - Positive alert

9. SSEP : Elicited in a cyclical repetative manner from peripheral nerve (median, ulnar and posterior tibial). Measured at the level of the subcortex (upper cervical spine, inion) and cortex (scalp). Monitor the integrity of the peripheral nerves dorsal column of spinal cord, brain stem, subcortex and sensory cortex of brain. Commonly used during spine surgeries specially when postero -lateral sensory elements are at risk of ischemia. Significant to the SSEP waveform includes a decrease of amplitude >50% and increase in latency by >10% .

10. Latency depends on nerve stimulated : Median nerve : N20 Post. tibial : P40

11. BAER : Nerve involved : VIII Stimulated by : sound 80-100 db of sound generated to stimulate BAER wave form Reference point connected between A1 and A2. A device that produces auditory stimuli is placed in the EAC travel through pathway and responses are recorded from the scalp. Used in CP angle surgeries and brain stem glioma. Any injury to CN VIII will affect all of the waves after wave 1, decreasing their amplitude prolong their latency .

12. VEP : Used to assess the integrity of the visual pathway, including the eye, optic nerve, optic chiasma and visual cortex in the occipital lobe. A bright stimulus is applied to the eye and response are recorded from scalp electrode. Useful during surgeries at or near the optic chiasma or the occipital cortex. Sensitive to almost any anesthetic regimen produced difficulty in the ability to obtain and interprete the signal

13. EMG : Records electrical activity produced by skeletal muscles. It helps monitor the functional integrity of motor nerve. EMG is not sensitive to ischemia changes like MEP and SSEPs TYPE : Spontaneous EMG : Continuous monitoring of muscle activity. Detects irritation or mechanical trauma to nerve.

14. Triggered EMG : Nerves are electrically stimulated to test their functional and anatomical integrity. surgeon can also use stimulated EMG to find and protect cranial nerve during surgeries Special use, called “Triggered EMG” performed with pedicle screw testing during spine surgeries, relies on direct stimulation of the screw being placed within the bony pedicle. If there is disruption of bony pedicle and hence contact or near contact between the screw and neural elements, the amount of current necessary to stimulate the corresponding nerve root will be much less than if the pedicle were intact.

15. D wave :

16. BIS monitor : Pharmacogenetics : Study of effect of genes on metabolism of medicines. Time to think beyond mg/kg

17. Why we are doing this ??

18. Stages of anaesthesia : Stage I : stage of analgesia or disorientation Stage II : stage of excitement or delirium Stage III: stage of surgical anesthesia Stage IV : stage of medullary paralysis

19. Origin of EEG signal : Electric signal from the brain Signal is not rhythmic like the heart Electric signal from the superficial part (cortex and grey matter) are recorded in EEG. These neurons are called pyramidal neurons.

20. Anteriorization of alpha wave : In an awake patient, alpha rhythm is located in parieto-occipital area. When anesthesia is given alpha rhythm shifts to the frontal area. Quantifying anteriorization provides objective indicator of level of anesthesia

21. Different plane of anesthesia an EEG : When patient us shifted to OT : Fast frequency and less amplitude. When induction started : large amplitude and less frequency. When induction is deeper : alpha on delta activity. Even more deeper : Burst supression . Further deeper : Total isoelectric line

22. Spectral analysis : Determine the frequency of waves at a particular point of time. Two separate demarcated red bands seen in alpha and delta frequency. This is the good target for depth of anesthesia.

23. BIS monitoring The US Food and Drug Administration cleared BIS monitoring in 1996 for assessing the hypnotic effects of general anesthetics and sedatives. It is a processed EEG. The BIS monitor collect raw EEG data through its sensor and uses an algorithm to analyze and interpret data .

24. BIS setup : BIS monitoring involve the application of four electrode on the forehead. The skin of forehead is cleaned with an alcohol swab, and 2-5 secs of digital pressure is applied over the sensor leads.

25. BIS monitor displays : BIS number Trend graph of Bis values over time. Raw EEG waveforms in real time. Various signal quality indicators as SQI, EMG. Alarm indicator and messages.

26. Limitations of BIS : Anesthetic Agents : The anesthetic agents used affect BIS values. The patient anesthetized with one anesthetic drug may be more sedated than another patient with same score anesthetized with a different combination of drugs. BIS monitor is unreliable with certain anesthetics such as ketamin and nitrous oxide. Children: It is difficult to titrate anesthetic agents in infants younger than 6 months of age with BIS this could be due to difference in EEG in this population as brain maturation and synapse formation occur during this period.

27. Hypothermia : Studied shows there is wide variation in BIS values during the decrease in body temperature. The BIS goes down by 1.12 units for each degree Celsius reduction in body temperature. Neurological disorders : IT alters the ability of the BIS to monitor the depth of consciousness, it is not reliable tool to assess depth of anesthesia in these population. Generally BIS values are lower in these patients

28. Artifacts with BIS : Interference with medical devices causes artifacts and impairs the ability of BIS monitor to assess the depth of anesthesia. Current evidences found that time to extubation and discharge from the PACU is reduced with the use Of BIS monitoring.

29. THANK YOU