Ch 26 Anesthesia for Neurosurgery
- Neurophysiologic monitoring & effects of surgical brainstem manipulation
- Encephaloceles and myelodysplasia
- Chiari malformations
- Hydrocephalus
- NCraniosynostosis
- Epilepsy
- Venous air embolism
Review in Book
- _______(a) matter injury is a major cause of persistent brain injury in small preterm infants.
o This may occur as a result of IVH or as a consequence of prematurity, hypoxia, ischemia, and _______(1).
o _______(2) therapy may reduce the incidence of severe IVH. - IVH (grades 1 – IV) can occur during the first few days of life.
o IVH is the leading cause of morbidity and mortality in small, preterm infants.
o Predisposing factors to IVH include:
■ _______(3), _______(4), _______(5) (3 hyps)
■ fluctuations in arterial or venous pressure, low hematocrit, overtransfusion,
■ rapid administration of _______(6) solutions (i.e., _______(7)). - Avoid procedures that increase ICP, blood pressure and anterior fontanelle pressure such as “_______(b)” intubations and aggressive _______(c) of the ETT.
- Analgesia and anesthesia should be provided during surgery and painful procedures
o Consider comfort measures to _______(8) _______(9). - Consider _______(d) glucose (i.e., “Sweet-Ease”) in the infant population.
Answers:
1. inflammation
2. Indomethacin (NSAID)
3. hypoxia
4. hypercarbia
5. hypernatremia
6. hypertonic
7. sodium bicarbonate
8. minimize
9. stress
a. Periventricular white
b. awake
c. suctioning
d. 24%
Cerebrospinal fluid (CSF) and hydrocephalus
- CSF, which occupies the cerebral ventricles and the subarachnoid spaces surrounding the brain and spinal cord, is formed by the _______(1) in the temporal horns of the lateral ventricles, the posterior portion of the third ventricle, and the roof of the fourth ventricle.
o Meningeal and ependymal vessels and blood vessels of the brain and spinal cord also contribute small amounts of CSF.
- The choroid plexuses are cauliflower-like structures consisting of blood vessels covered by thin epithelium through which CSF continuously exudes.
o In the adult, the rate of secretion is ~_______(2) mL/day.
▪ About ~_______(3) mL circulating at any given time. - In the adult, CSF is formed at ~_______(4) mL/Hr.
o _______(5) are similar for babies - CSF flow is initiated by pulsation in the choroid plexus.
o From the lateral ventricles, CSF passes into the third ventricle via the foramen of Monro and along the aqueduct of Sylvius into the fourth ventricle, with each ventricle contributing more fluid by secretion from its choroid plexus.
o CSF then flows through the two lateral foramina of Luschka and the midline foramen of Magendie into the cisterna magna and throughout the subarachnoid spaces.
o CSF is reabsorbed into the blood by _______(a) filtration through the _______(6), which project from the subarachnoid space into the venous sinuses. - Goals of anesthesia for neurosurgery are neuroprotective.
o Avoid cerebral _______(7)
o Avoid cerebral _______(8)
o Avoid cerebral _______(9)
o Avoid cerebral _______(10)
o Avoid _______(11)
Answers:
1. choroid plexus
2. 500
3. 150
4. 20
5. Proportions
6. arachnoid villi
7. edema
8. hypoxia
9. hypoperfusion
10. hypermetabolism
11. neuronal membrane damage
a. hydrostatic
**Review Table 26.1 below Neurophysiologic Effects of Common Anesthetic Agents
**Review Table 26.2 Maneuvers of Neuroprotection
Table 26.2: Maneuvers of Neuroprotection
- Goals: table 26.2 maneuvers of neuroprotection
- Avoid cerebral _______(1)
- Avoid cerebral _______(2)
- Avoid cerebral _______(3)
- Avoid cerebral _______(4)
- Avoid _______(5)
Maneuvers: table 26.2 maneuvers of neuroprotection
- Head of bed at _______(6) degrees in midline:
o Increases cerebral venous drainage while maintaining CPP
- Corticosteroids:
o May improve outcomes in spinal cord injury.
o Decrease vasogenic cerebral edema in children with tumors.
o Stabilize neuronal membranes. Free-radical scavengers
- Controlled ventilation:
o Maintaining PaCO2 at normal to slightly low levels prevents both cerebral vasodilation and increased ICP.
- Muscle paralysis:
o Avoids coughing, straining, child movement, and other causes of increased ICP
Answers:
1. edema
2. hypoxia
3. hypoperfusion
4. hypermetabolism
5. neuronal membrane damage
6. 30
Maneuvers for Neuroprotection
- Ventricular drainage: Decreases ICP.
- Antihypertensives:
o Prevent further cerebral edema, ischemia, and cerebral hemorrhage.
o Severe _______(1) can significantly decrease CPP. - Anticonvulsants: Prevent seizure activity and increased ICP
- Hypothermia: Decreases _______(a) consumption
- Barbiturate coma: Membrane-stabilizing agents. ______(b) CBF and CMRO2.
- General principles of intraoperative management
o Increased ICP
■ PaCO2; volatile anesthetics; induction/emergence
o Risk for bleeding
■ Adequate IV access, Type & Cross with blood available in the OR
■ Consider monitoring CVP and/or arterial line - General principles of intraoperative management
o Difficult airway
■ Have difficult airway cart in the room; have additional experienced staff on hand; have multiple back up plans in accordance with the difficult airway algorithm
o Risk for VAE
o Possible CVL to aspirate air
■ _______(2) (millwheel murmur)
■ You need to aspirate the air very _______(3)
Answers:
1. hypotension
2. Precordial doppler
3. quickly
a. CMRO2 and CMRglu
b. Decreases
Maneuvers for Neuroprotection
- Ask the surgeon if nerve monitoring is planned before choosing to use a NMB. Surgeon may need to identify nerve roots before patient is paralyzed.
- Do you need to use a paralytic?
o Low dose Rocuronium (_______(a) mg/kg) may be used to facilitate endotracheal intubation.
o Nowadays, with _______(1), you don’t necessarily need to do low dose anymore - In infants and children, _______(2) or _______(3) may be given before intubation to prevent reflex bradycardia and to decrease secretions.
- Special Pediatric Neurosurgical Conditions
o Encephalocele
o Myelodysplasia
o Chiari malformations
o Tumors
o Hydrocephalus
o Craniosynostosis
o Epilepsy
o Vascular malformations
Answers:
1. Sugammadex
2. atropine
3. glycopyrrolate
a. 0.3
Myelodysplasias
- Neural tube defect causing defective development of any part of the spinal cord
- Results from failure of the neural tube to fuse during early fetal development (during the first _______(1) weeks of gestation).
- Much less common now thanks to prenatal vitamins and PO _______(2)
Encephalocele
- Encephalocele: a protrusion of the _______(3) and _______(4) through a defect in the skull, resulting in a _______(a)-like structure.
- Typically diagnosed in-utero via _______(5)
- Most occur in the _______(6) area; however, it may also occur in the frontal, parietal, and nasopharyngeal regions.
Answers:
1. four
2. Folate
3. brain
4. meninges
5. ultrasound
6. occipital
a. sac
Encephalocele Repair Procedure
- Most often repaired through _______(1): The dura is opened, the sac is removed, the dura is closed, and the skull is closed with bone or artificial plate applied to repair the skull defect.
- Encephalocele protrusion in the nasopharynx is repaired _______(2) by visualization of the defect, a layered repair using bone or cartilage, followed by a free mucosal graft.
- Craniofacial surgery is performed for protrusions in the skull (nose, sinuses, forehead) affecting the _______(3) and _______(4).
Answers:
1. craniotomy
2. endoscopically (FESS)
3. cribriform plate
4. nasal defect
Myelomeningocele Repair Procedure
- The defect is dissected and layers are separated and repaired.
- The edges of the spinal cord are mobilized from the adjacent epithelium and overlapped to form a closed tube.
- The dura is dissected from the fascia and closed over the spinal cord.
o The lamina defect is _______(1).
o The lamina defect may be addressed when the child is _______(2) if kyphosis or vertebral angulation develops.
- An attempt is made to separate and repair the lumbosacral fascia.
- Finally, the subcutaneous tissue and skin layers are arranged and closed.
o For more severe cases, _______(3) may be used to cover the spinal defect.
Answers:
1. not reconstructed
2. older
3. skin or muscle flaps
Neurosurgical Procedures
Considerations
- Maintain “defect” covered with sterile dressing
- Positioning for induction and intubation may be challenging:
o Place the meningomyelocele or encephalocele inside a doughnut pillow or in between rolls to prevent pressure injuries.
■ May need additional padding for shoulder and head.
o Alternatively, place patient in the _______(1) position with an assistant applying forward pressure from the back of the head and backward pressure on the shoulders to prevent neck extension.
o Goal: Avoid _______(2) on the defect, and also optimize the airway
o Likely to use the _______(3)
- Position for surgery: _______(4)
- Body temperature maintenance may be challenging:
o Pre-warm OR to 24°C (75°F)- often hotter than that
o Avoid unnecessary exposure of body parts
o Warm all fluids; warm and humidify all gases
o Use infrared heating lamp (during induction and emergence)
o Warm skin preparation solutions to _______(5)
o Use warm incubator postoperatively. - Blood loss may be significant: Have cross-matched blood available
- Only use _______(6) free equipment/supplies
Answers:
1. left lateral decubitus
2. direct pressure
3. videoscope
4. prone
5. 40°C
6. latex
Neurosurgery
Anesthesia
- Maintenance
o Muscle relaxation as needed and allowed by surgeon.
o Controlled ventilation to maintain EtCO2 _______(1).
o Check positioning, padding, and ETT placement after every position change and periodically.
o Maintain body temperature and hemodynamic stability
o Monitor & maintain fluid balance carefully.
o _______(a) blood pressure and _______(2) can be used as guide for replacement as accurate measurement of blood loss may be difficult.
- Emergence:
o patients almost always remain intubated for the first _______(3) hours. - Arnold-Chiari Malformation
o an anatomic anomaly of the cerebellum, brainstem and craniocervical junction.
o Results in a downward displacement of the cerebellum through the foramen magnum into the spinal canal.
Answers:
1. 35-40
2. HCT
3. 24
a. Arterial systolic
Table 26.3: Types of Chiari Malformation
- Type I:
- _______(a) displacement of cerebellar _______(1) below the plane of the _______(2)
- Type II (Arnold-Chiari; associated with myelomeningocele):
- ______(a) displacement of the cerebellar _______(3), _______(4), and _______(b) brainstem below the plane of the foramen magnum
- Dysplastic brainstem with characteristic kink, elongation of the fourth ventricle, beaking of the quadrigeminal plate, hypoplastic tentorium with small posterior fossa, polymicrogyria, enlargement of the massa intermedia
- Type III:
- Caudal displacement of the cerebellum and brainstem into a _______(5) meningocele
- Type IV:
- Cerebellar _______(6)
Answers:
1. tonsils
2. foramen magnum
3. vermis
4. fourth ventricle
5. high cervical
6. hypoplasia
a. Caudal
b. lower
Patients with Arnold Chiari malformations may present with
- Difficulty Swallowing
- Recurrent _______(1)
- Stridor
- Apneic episodes
- _______(2) or absent gag reflex - Can’t protect their own airways
- Elevated ICP
- Pain (mainly _______(3) and _______(4) headaches)
- Tongue _______(5)
Abnormal control of ventilation
- Stridor → may _______(6) preoperatively
- May not improve immediately postoperatively
- Possible postoperative apnea
Recurrent aspiration
- Impaired pulmonary function → difficult _______(7) possible
Patient positioned prone with neck flexed
- _______(8) tube may be used; less likely to kink
o tape is unlikely to be loosened by saliva
Increased ICP may be present resulting in N/V, electrolyte disturbances
Blood loss may be rapid, massive and difficult to measure accurately requiring invasive monitoring, IV access, have blood products available
Intraoperative neurophysiologic studies or cortical ______(a) may be necessary; high concentrations of inhalational agents may interfere with the recording; consider _______(9)
Answers:
1. aspiration
2. Depressed
3. neck
4. occipital
5. atrophy
6. intubate
7. ventilation
8. Nasotracheal
9. TIVA
a. SSEPs
Arnold-Chiari Considerations
Prone position
- Consider a _______(1) tube in small children à secure appropriately
- Prone on a frame or pins or bolsters with, _______(2) head-up tilt
- Monitor vital signs carefully during manipulation in the region of the brain stem
Sitting position
- Concern for air embolism → use precordial _______(3) probe and capnograph;
■ place _______(4) line to aspirate air in case of embolism and to guide fluid therapy
o Zero arterial transducer at level of the _______(5) and CVP transducer at level of the _______(6)
o CV stability → Lower limbs bandaged to promote venous return
Procedure may be performed in prone or _______(7) position.
- Head placed in _______(a) fixation: NOT Babies
- Midline incision made and dissection is carried down to the skull and the posterior arch of _______(8)
- Paramedian burr holes are placed to aid in the _______(9) craniectomy.
Answers:
1. nasotracheal
2. 15°
3. Doppler
4. CVP
5. ear
6. heart
7. seated
8. C1
9. suboccipital
a. Mayfield pin
Arnold-Chiari Considerations
Full recovery from anesthesia for extubation
- Gauge your anesthetic so the surgeon can do a neuro exam shortly after extubation
- Smooth extubation
o IV Lidocaine 1.5 mg/kg
If the patient is unresponsive, or shows signs of respiratory depression, then the patient should remain intubated.
- Preserve Optimal Intracranial Conditions
o Blood Pressure (_______(1) – _______(2) = _______(3))
o Support Cerebral Autoregulation
o Fluid Status
o Routine Monitoring of Neurologic Signs
o Anticonvulsants
Alterations in Neuro-Hormonal Regulatory Systems (i.e., ADH)
Bleeding, Infection
Local anesthesia (_______(4))
- Postoperative Analgesia
Answers:
1. MAP
2. ICP
3. CPP
4. 0.25% bupivacaine with 1:200.000 epinephrine 0.5ml/kg
Neurosurgery: Tumors
- Clinical presentation:
o Visual impairment
o Endocrine deficits
o Growth hormone, gonadotropins, ACTH, TSH, ADH
- Tumor infiltration into hypothalamus:
o Leads to disturbances of memory, attention, impulse control, motivation, socialization
- _______(1) have been shown to increase intra- and post- operative morbidity rates
- Children were found to be more likely to present with _______(2)
o reflecting the increased incidence of increased intracranial pressure and hydrocephalus in this patient population.
Answers:
1. Diabetes insipidus, hypoadrenalism and hypothyroidism
2. headache, nausea/vomiting, and papilledema (swelling of the optic nerve)
Neurosurgery Tumors
Endocrine Disturbances
- _______(a) thirst or urination
- Unusual sleepiness or change in energy level
- Unusual changes in personality or behavior
- Short stature, slow growth, or delayed puberty
- _______(1) 5 senses?
- Obesity
Increased ICP
- Headaches including _______(2) that goes away after vomiting
- Vision changes
- Nausea and vomiting
- Loss of balance or trouble walking
- Increased head size
Steroid therapy may be warranted as part of the anesthetic care plan
- _______(3) therapy may begin preoperatively
Agents to help decrease ICP:
- _______(4)
- _______(5)
- _______(6)
- _______(7)
Avoid the following:
- Agents that may increase ICP:
■ SCh. _______(8), etc.
- Overstimulation
■ Prolonged laryngoscopy
■ Noisy environment
- _______(9)Breathing?
■ It is more difficult for the surgeon to confirm that the entire tumor has been removed.
Answers:
1. Hearing loss
2. morning headache or headache
3. Corticosteroid
4. Mannitol
5. 3% saline
6. Propofol
7. Isoflurane
8. Ketamine
9. Hyperventilation
a. Increased
Neurosurgery Tumors
What to look for:
- Monitors
- Positioning
- Blood loss
How to be ready
- Standard monitors plus:
o A-line
o _______(1)
o Urine output
o ± _______(2)
Long surgery
- Positioning
■ Semi-sitting (possible a.)
- Pressure points
- Table turned 180°
Minimal blood loss unless there is accidental perforation of internal carotid or cavernous sinus
Answers:
1. CVP
2. Doppler
a. VAE
Neurosurtgery Tumors
Review Figure 26.6 for relative sensitivities of air embolism monitoring modalities.
What to Look For:
- Diabetes insipidus
- Optimal neurosurgical conditions
How to be ready
- Fluid replacement
o Rapid correction - seizures, coma, cerebral edema
o Serial serum _______(1) should be checked
o Vasopressin (_______(2) U/kg/hour)
- Blood pressure control
o High blood pressure
■ Leads to higher _______(3)
o Low blood pressure
■ Leads to _______(4) - Increased _______(5) may occur and/or be severe
o Avoid use of _______(6)
o Vomiting may ensue d/t increased ICP → check _______(7) preoperatively
o Acute symptoms of increased ICP demand immediate _______(8)
o Doll’s Eyes: Clear appearance of ICP - _______(9) extubation (to permit rapid neurologic assessment)
- Large and secure IV access
- Latex precautions
Answers:
1. osmolalities
2. 0.001-0.01
3. ICP
4. ischemia
5. ICP
6. succinylcholine and/or ketamine
7. electrolytes
8. surgery
9. Awake
Hydrocephalus
- an abnormal accumulation of CSF within the cranium that may either be obstructive or non-obstructive.
- _______(1) hydrocephalus is caused by a blockage in the flow of CSF.
- Considered ‘_______(2)’ when the fluid’s pathway proximal to the subarachnoid space is obstructed
o as in aqueduct _______(3).
- Non-obstructive hydrocephalus, or “communicating,” occurs when the CSF pathway into the subarachnoid space is _______(4), such as may occur after chronic _______(5).
o Caused by a reduction in the volume of brain substance, with secondary dilation of the ventricles
■ and/or an overproduction of CSF as in _______(6)
■ and/or _______(7) reabsorption of CSF due to scarring.
- Hydrocephalus is often managed surgically with placement of a shunt.
o Hydrocephalus shunting involves the implantation of two catheters and a flow control valve system to drain the excess accumulation of cerebrospinal fluid (CSF) from the brain’s ventricles (or the lumbar subarachnoid space) to another part of the body where it can be absorbed (the _______(8) or the right atrium).
Answers:
1. Obstructive
2. non-communicating
3. stenosis or Arnold-Chiari
4. open
5. arachnoiditis
6. choroid plexus papilloma
7. reduced
8. peritoneum
Hydrocephalus
Considerations
- Blood loss usually minimal but have a large bore IV ready
- Inject local anesthetic to block _______(1) nerve for frontal shunt or to block _______(2) nerve for posterior shunts.
- The use of LA _______(3) but does not eliminate the postoperative pain medication requirements.
- The part of the surgery that is most stimulating is the _______(4) process used to place the distal catheter.
- Discontinue inhalational agents before the end of surgery so child is completely _______(5) before leaving OR to facilitate neurologic evaluation.
Craniosynostosis
- the premature _______(6) of cranial sutures occurring within the first _______(7) months of life.
■ The early fusion prevents normal skull expansion and results in facial deformities.
■ Compression and increased ICP can lead to neurologic damage if not repaired.
Answers:
1. supraorbital
2. posterior auricular
3. reduces
4. tunnelling
5. awake and responsive
6. fusion
7. 20
Blood Loss During Repair of Craniosynostosis
Type of suture being repaired | Typical blood loss, % of blood volume
— | —
Sagittal | a.
Unicoronal |b.
Metopic | c.
Bicoronal | d.
- Males are affected _______(1) times more frequently than females.
- Although the exact _______(2) is unknown, it has been linked to alterations in the _______(3) signaling pathways during fetal development.
Answers:
a. 24 ± 15
b. 21 ± 12
c. 42 ± 12
d. 65 ± 35
1. two
2. cause
3. cytokine
Scaphocephaly
- the most common form of craniosynostosis and is caused by the fusion of the _______(1) suture resulting in elongation in the _______(2) direction.
Brachycephaly/Plagiocephaly
- the next most common form and results from the fusion of the _______(3) suture causing an expansion in the _______(4) directions
- Half of these children also have _______(5) delays.
- Non-syndromic craniosynostosis has no identifiable genetic cause and is classified as simple, involving only one suture, or compound, involving two or more sutures.
- Syndromic craniosynostosis is associated with genetic abnormalities and is most commonly seen in _______(6) and _______(7) syndrome.
o It has been linked to alterations in _______(8) signaling pathways.
Answers:
1. sagittal
2. anteroposterior
3. coronal
4. lateral
5. developmental
6. Apert
7. Crouzon
8. fibroblastic growth factor
Craniosyntosis
History/physical exam
- Patient age, body weight (<_____(4) kg) are associated with increased blood loss
- length of time to surgery increases the risk of associated neurological issues
- Associated neurological issues (>_______(5) suture involvement = increased ICP; possible developmental problems; potential for _______(1) atrophy)
It is common for these patients to have other congenital disorders such as difficult airways, cardiac defects, and cleft palates.
Airway assessment
- Potential for difficult airway (may have associated craniofacial conditions)
- _______(2) syndrome (beaked nose, hypoplastic maxilla = difficult mask ventilation and risk for airway obstruction)
- _______(3) syndrome (hypoplastic maxilla, fusion of cervical vertebrae, narrow/fused trachea = difficult mask ventilation and breathing issues/airway obstruction)
Answers:
1. optic
2. Crouzon
3. Apert
4. 5
5. 1
Crow’s Nose for beaked (Crouze)
Atlas for Apert (cervical fusion)
