Anesthesia For Neurosurgery PowerPoints Flashcards
Presentation of Acute Increase in ICP in Adults (4)
1) HA
2) N/V
3) AMS
4) Visual Disturbances
Presentation of Acute Increase in ICP in Peds
Lethargy & Vomiting
Bulging Fontanel
Presentation of CHRONIC changes in ICP adult (5)
1)HA
2)Lethargy in varying degrees
Cognitive changes
3)6th CN ( Abducens )palsy = Lateral Rectus weak= eyes cross inward toward nose (esotropia)
4)Parinauds’s disturbances : inability to move the eyes up or down
5) Gait disturbances
Kids Presentation of chronic ICP changes (4)
1) Failure to thrive
2) Head Circumference Gradually increases
3) Fontanel may bulge
4) CN palsies ( Again dependent on etiology )
WHat is ICH ?
ICP > 20 mmHg
Acute ICH features
Irregular Respiration
Bradycardia
HTN
Ipsilateral fixed , dilated pupils ( CN 3 compression on the same side of the mask .
Chonic ICH features
Papilledema
Treatment for ICH
ABC Intubation + hyperventilation PCO2 maintained 25- 30 ish mmHg Mannitol Sedation Steroids * wean those off ventilator slowly
2 auto regulation Failure
Either you get
Hypoperfusion» Ischemia or
Hyperperfusion and Breakthrough :
Breaking BBB, Swelling, Vessel rupture , hemorrhage.
Cerebral Steal
Steal from the poor( ischemic area) to give the rich ( non ischemic area). It’s a vasodilator response that decreased CBF to the ischemic area
What therapy do you implement to enhance perfusion ( 3 things )
Maintain High Perfusion pressure
Hypocapnia = constricts vessels to counteract the cerebral steal
Barbituates
GCS
Severe Brain Injury defines as < 8-9
Moderate = 8-12
Minor ≥ 13
Monitor ICP when GCS <7 *
6 times when you monitor ICP
Trauma GCS <7 SAH Hydrocephalus Tumor AV malformation
Lumbar ICP should not be done when ?
When you have IC disorders . It can’t amuse downward her nation bc the there is inaccuracy due to small caliber and Lon length catheter .
What are the 2 modalities of ICP modalities preferred ?
Intraventricular : cannulate the ventricular FRONTAL HORN
Intraparenchymal : held in place by bolt screw
What is the effect of ICP on cerebral Blood Flow ?
Reduce CBF
What Is CPP , when use it ? What Is normal CPP ? What CPP is considered critical
Used as a surrogates for CBF
Used when Stats are rapidly changing i.e during herniation
CPP= MAP - ICP or CVP ( whichever higher)
< 40 is critical
Maintain CPP 50 - 55 but book says 60
Hydrocephalus Communicating vs Non Communicating
Communicating :
BLOCKAGE of flow around base of brain or of arachnoid villi = fluid collects outside brain and some collect in the ventricles
Non Communicating :
Aqueduct of Sylvius is blocked ! Lateral 3 rd ventricles is backed up ! Volume increase
Blood Brain Barrier
Low permeability of these barriers is due to the “tight junctions” that join the endothelial cells of the brain tissue capillaries…
What is BBB permeable to ?
What is BBB slightly permeable to ?
What is BBB Impermeable to ?
Permeable to : Water/CO2/O2/ Most lipid soluble stuff Slightly permeable to:Electrolytes, Na+ Cl- K+ Impermeable to : Plasma Proteins Non Lipid Soluble large molecules
Viscous cycle of Brain edema
Edema»_space; decrease blood flow»_space;Ischemia»_space; more edema
What is MOA of Brain edema ( 2)
Either capillary pressure increase or
Capillary is damaged = leaky wall
Brain CMRO2 vs Total body’s .
Brain CRMO2 is 15% of total body ‘s CRMO2
Can brain do aneorobic metabolism
No!
Most brain energy supplied by
Glucose
Only 2 minute of glucose stored as glycogen in neurons
MC 1º brain tumor
Astrocytoma Grave prognosis < 1 year life expectancy Found in cerebral hemisphere Treatment: Resection, radiation and chemo
2nd MC 1º tumor:
Meningioma
Occurs in convexities of brain and parasagittal region
Arise from arachnoid cells external to brain (NOT dura)
Slow growing
Resectable
Pituitary Adenoma
Most commonly prolactinoma
Bitemporal hemianopia “ tunnel vision”
Hyper or hypo pituitarism are sequelae
Shwannoma
3rd MC 1º tumor
Origin is : Schwann Cell
Often in CN VIII»_space; acoustic Shwannoma
Respectable
Seizure causes in Children
Causes
Children- genetic, infection (febrile), trauma, congenital, metabolic
Seizures causes in adult
Adults- tumors, trauma, stroke, infection
Seizure causes in Elderly
Elderly- stroke, tumor, trauma, metabolic, infection
IV anesthetic effect on CMR and CBF
Decrease CMR and CBF in a parallel fashion
Whereas …
Most Inhalation decrease CMR while increasing CBF ( vasodilation )
With IC pathology responses to anesthetics may be ≠ from those of normal subjects . They may have :
Brain tissue hypoxia, acidosis, edema
Cerebral vasoparalysis may occur and coupling b/w blood flow and metabolism can be impaired…
Under these circumstances… Autoregulation and CO2 reactivity are also disturbed…
What strict parameters are required during neuroanesthesia ?
Strict BP
Strict Resp management
Why is Hyperventilation NOT recommend in pts with stroke ?
Low CO2»_space; divert blood from normal area to Ischemia bc of cerebral vasoconstriction»_space;not recommended in stoke
Reverse Steal
2) Marked decreased in CBF in pts w/ head trauma
HYPOCAPNEA = reverse steal or steal ?
Steal bc of vasodilation of good healthy vessels, blood shunts from Ischemic area to vasodilated area
Does Anesthesia cause a steal effect ?
Yes !
What other way outside of increase in CBF do anesthetic agents affect ICP ?
Change the rate of production and reabsorption of CSF
ICH can be rapidly controlled by doing ____but after a while it will cause
Hyperventilation ( decrease ICP )
Marked decreased in CBF in pt w/ head trauma ( another reason why not to give it to stroke patients)
N2O effect on CBF CMR ICP
CBF : 2 arrows up
CMR: little or none
ICP : 2 arrows up
Isoflurane ( Furane ) effect on CBF CMR ICP
CBF : little or nine
CMR 2 arrows down ( decreased )
ICP : none, or slightly or up ( dose dependent)
Sevo effect on CBF CMR ICP
CBF : decreased , none , or slightly up
CMR : 1 or 2 arrows down
ICP : None , Slightly or up
Des effects on CBF , CMR, ICP
CBF : Up or down
CMR: 2 Arrows down
ICP: Up or one
Which Fossa is : Cerebellum , Midbrain, Pons, Medulla
/
Posterior Fossa
S/of ICP inc, Initial non specific ( Post Fossa Sx topic )(6)
Listlessness HA Fatigue Vomiting Anorexia Personality change
What are the Cerebellar or brainstem signs
Dysmetria ( Lack of coordination )
Hemoparesis ( Unilateral weakness )
Crania Nerve Deficits
Specific clinical syndromes occur with elevated ICP due to what kind of Tumor ?
Acoustic Neuroma CP angle tumors (cerebellarPontine Angle tumor ) Brainstem glioma Carotid body tumor * they rapidly involve neural structures
Midline and 4th Ventricle lesions have what s/s?
Truncal ataxia Wide based gait Nystagmus Extraocular Movement abnormalities Truncal titubation ( Nodding head/body- nervous) Hydrocephalus ( early & common) Frequent papilledema Signs of brainstem lesion
S/S of lateral cerebral hemisphere
Lots
Herniation of cerebellar tonsils through the Foramen _____especially in _____ appear as
Magnum ; children; appear as Meningismus : (neck stiffness, photophobia , HA ) Head Tilt Muscle Spasm Opisthotonus Vomiting Skew deviation of eyes Downbeat/vertical nystagmus
Typical posturing from tonsillitis herniation may be mistaken for
Cerebral fits
how do you know , you have brainstem involvement ?
Ocular Problems : pupil size, ocular mobility , nystagmus
Sensory + motor deficits
Resp changes : vary depending on brainstem compression i.e hyperventilation vs apnea
Multiple CN dysfunction including bulbar palsy
Progressive compression on brainstem = gaze + facial palsies»_space;rapid loss of consciousness, Resp changes , brady, HTN
Posterior fossa is home to
Brainstem Major motor and sensory pathways CV & Resp center RAS Lower CN nuclei
Challenge for anesthesia providers with post fossa sx
1) facilitate surgical Acces while minimizing nervous tissue trauma/ischemia , while maintaining Resp and CV stability
Pre op a Post Fossa patient please
Complete Medical Hx Review List of Meds Physical Exams Neuro Exam Routine investigation ( labs, imaging)
What is the monitoring goal for PFS ?
Adequate CNS perfusion
Maintain Cardiorespiratory Stability
Detect & treat VAE
Positions for PFS?
Sitting
1) Head in 3 pin holder
2) LA infiltration of scalp and periosteum at pin site= reduces hypertensive response
3) pad bony prominences
4) thigh high stockings
5) support elbows w/ pillow/pads so they don’t touch table = avoid streth or brachial plexus injury ,
6) legs feee of pressure at level of common Peroneal just distal and lateral of fibula head
How to prevent cervical cord stretching and obs of venous drainage from the face and tongue
Maintain 1 inch space btw chin and chest
What do you avoid during PFS?
AVOID Large airway and bite block placement
AVOID Excessive neck rotation
Avoid excessive flexion of knees toward chest = prevent abdominal compression , LE ischemia & sciatic nerve injury
What are advantages of sitting position ?
1) Lower airway pressure
2) Eases of diaphragmatic excursion ?
3) Better able to hyperventilate
4) Easy Acces to extremities for monitoring fluid / blood administration & blood sampling
5) Number of blood transfusion less in sitting position
6) can see the face for obs of motor response in face during CN stimulation
7) better surgical exposure , less tissue retraction , less cranial nerve damage , more complete resection of tumor
Contraindications for PFS? ( 8)
Intra cardiac defects Severe hypovolemia Cachexia Severe hydrocephalus Lesion vascularity Extremes of age / impaired cardiac function Degenerative Disease of cervical spine Significant CVD
What physio changes happen during sitting position ?
Head elevated higher than Rt Atrium
Decrease in Dural sinus pressure up to 10 mmHg = 1) increased risk VAE( 45% ) & 2) decreases venous bleeding
PFS in prone position . Advantage vs Disadvantage
Advantage :
Heap is elevated to decrease venous bleeding
No face compression by keeping head elevated, and shoulders at/or above the edge of the OR table
Less VAE
Disadvantage:
Surgical field not clear
Eye compression = blindness from retinal artery thrombosis
Conjunctival edema
Venous pooling in the lower ext sufficient to impair venous return and hypotension especially in elderly , debilitated patients
What positions can posterior fossa surgery be in ?
Sitting Prone Lateral 3/4 prone Park Bench
When to use lateral position in PFS ?
When unilateral in upper post fossa
What advantages do Three Quarter prone and park bench have ?
Greater head rotation and access to more axial structures
Complex tangle of abnormal dilated channels directly shunt blood btw artery & vein
Nidus
Where are aneurysms often found
On the arteries feeding the AVM
AVMs present with symptoms?
Seizures, hemorrhage, progressive neurological dysfunction and or HA
Complications of AVMs
Hemorrhage into surrounding tissue
Ischemia
Seizures
Brain cell death
S/S of AVM
Seizure HA Whooshing sound in skull Other : Subtle behavioral changes Paralysis/weakness in one part of body Loss of coordination /balance Visual disturbances Abnormal sensations
