Neuroanesthesia involves maintaining cerebral perfusion pressure, blood flow, volume and oxygen levels while minimizing intracranial pressure. Key principles include autoregulation of blood flow, responsiveness to CO2, and effects of anesthetic agents. Common procedures require tumor resection, pituitary or aneurysm surgery. Positioning, hemodynamics and ventilation must be carefully managed due to risks of hypotension, hypertension and increased intracranial pressure. Close monitoring of fluids, glucose and electrolytes is also important.

1. Neuroanesthesia
BY
BASSIM MOHAMMED JABBAR
MSC ANESTH &INTENSIVE CARE
TUMS

2. Neuroanesthesia
The practice of neuroanesthesia is technique that the target
organ of both the surgeon and the anesthetist is one and the same
.
In order to appropriately anesthetize the patient for neurosurgery,
an understanding of the interrelationships of neurophysiology,
pathophysiology and pharmacology is important

4. Basic principles of neurophysiology
There are six interrelated components that are important
to the practice of neuroanesthesia they are :-
1. Maintenance of cerebral perfusion pressure (CPP)
2. Cerebral blood flow (CBF)
3. Cerebral blood volume (CBV)
4. Intracranial pressure (ICP)
5. CO2 responsiveness (CO2R)
6. Cerebral oxygen metabolism (CMRO2)

5. Cerebral Perfusion Pressure :- CPP is the difference between
mean arterial pressure (MAP) and intracranial pressure (ICP)
[CPP = MAP – ICP]
Both intracranial pathology and drugs may
compromise CPP through effects on MAP and/or ICP
CPP is usually >70 mmHg. An optimal CPP has not been
defined but in the context of head trauma
a CPP < 60 is associated with a poorer outcome.

6. Cerebral Blood Flow
The average CBF is ~40-50ml/100gm/min.
CBF is autoregulated – that is, blood flow is maintained
over a wide range (~50 – 150 mmHg) of perfusion
pressures in order to:
 avoid ischemia when blood pressure is reduced
edema or hemorrhage and disrupt BBB at higher blood
pressures

8. Autoregulation
Ability of the cerebral blood vessels to alter their caliber (diameter) to
maintain a constant flow in face of variation in blood pressure.
CBF is autoregulated – that is, blood flow is maintained over a wide range of MAP
(~50 – 150 mmHg)
Increase MAP cerebral vasoconstriction
Decrease MAP cerebral vasodilatation
Constant CBF is maintained

11. Cerebral Blood Volume
Approximately 15% of CBV is in the arterial tree and
~15% in the major venous sinuses. The remainder is in
the capillary and venous systems.
Changes in CBF and CBV are generally proportional to
one another but, for instance, changes in head position
from standing to supine to head down can increase CBV
without changing CBF
e.g Propofol decreases CBV in humans and sevoflurane
increases it but less than isoflurane

12. Intracranial Pressure ICP
Maintenance or reduction of ICP (normal value ~10 mm Hg) is
one of the important aims of neuroanesthesia.
As ICP increases above ~20 mmHg, focal reductions in CBF
occur and further increases eventually result in global cerebral
ischemia.
The three major components of the intracranial cavity are:
brain (~80%), cerebrospinal fluid (CSF) (~10%) and CBV
(~10%).
If one component increases its volume, it must be compensated
for by a decrease in another to prevent ICP from increasing.

13. CO2 Responsiveness
CO2R of the cerebral arterial tree is important in that hypercarbia
results in vasodilation and increased CBV.
Conversely, hyperventilation causes cerebral arterial vasoconstriction,
decreased CBF & CBV and a decreased ICP.
While the reduction in ICP is beneficial, the reduced CBF can result
in ischemia so that caution must be exercised with the extent and
duration of hyperventilation

14. Clinical neuroanesthesia
The common types of neurosurgery can be divided
into
1- excision of intracranial mass lesions, especially
supratentorial tumors.
2-decompressive procedures in major head trauma
3- aneurysm clipping

15. Anesthetic Influences
1. Anesthetic agents have a variable influence on CBF and
metabolism, CO2 reactivity, and auto regulation.
2. Inhalation anesthetics tend to cause vasodilatation in a dose-related
manner.
3. during low-dose inhalation anesthesia, CBF is either unchanged or
slightly increased.
4. Compared with other inhaled agents, sevoflurane in clinically
relevant doses does not increase CBF.
5. Intravenous (IV) agents, including thiopental and propofol, cause
vasoconstriction and reduction in metabolism.
Ketamine, on the other hand, increases CBF and metabolism

16. 6. Cerebrovascular CO2 reactivity is a robust
mechanism and is preserved under all
anesthetic conditions.
7. Cerebral autoregulation, on the other hand, is
abolished by inhalation agents in a dose-
related manner but is preserved during
propofol anesthesia.

23. ANESTHETIC MANAGEMENT
A. Preoperative Evaluation
B. Induction and Airway Management
C . Maintenance of Anesthesia
D. Ventilation Management
E. Fluids and Electrolytes
F. Glucose Management

24. A. Preoperative Evaluation
1.Assesment of the patient’s medical and surgical history.
2. Preoperative risk stratification for a cardiac complication is important to consider.
Current guidelines include delaying surgery for at least 2 weeks after simple balloon
angioplasty,
4 to 6 weeks after placement of a bare metal stent,
and 1 year after placement of a drug-eluting stent.
3. Many patients presenting for spine surgery have weakness or paralysis that may present
a contraindication to the use of succinylcholine (Sch).
4. Many neurosurgical patients have been exposed to antiepileptic medications. Previous
allergies or reactions to these
medications, especially phenytoin, should be elucidated

25. B. Induction and Airway Management
1. During induction of anesthesia, three iatrogenic consequences
(hypotension, hypertension, apnea) may be significant hazards for
neurosurgical patients.
a. Hypertension caused by laryngoscopy is poorly tolerated by
patients after aneurysmal SAH because systolic hypertension is
thought to be a cause of recurrent hemorrhage from the aneurysm.
b. Hypertension may worsen elevated ICP and possibly lead to
herniation of cranial contents into the foramen magnum
c. Apnea results in a predictable increase in PaCO2 and corresponding
cerebral vasodilatation.

26. 2. A cervical collar for known or suspected cervical spine
injury may make tracheal intubation more difficult.
3. Many neurosurgical and spine surgery patients have conditions in
which Sch is contraindicated.
a. In the setting of acute stroke or spinal cord injury (SCI), it remains
safe to use Sch for Approximately 48 hours from the time of injury.
b. Alternatively, a rapid-acting non depolarizing muscle relaxant is
appropriate in many neurosurgical patients to achieve acceptable
intubating conditions.

27. C. Maintenance of Anesthesia
1-The primary considerations for maintenance of anesthesia include the type of
monitoring planned for the procedure, brain relaxation, and the desired level of
analgesia at the end of the surgical procedure.
2. Remifentanil is appropriate for neurosurgical procedures
in which tracheal extubation is planned at the end of the surgery and minimal
residual sedation is desired to facilitate the neurologic examination.
3- Replacement of a volatile anesthetic with a continuous infusion of propofol
(TIVA) is desirable when brain relaxation is inadequate with a volatile
anesthetic.

28. D. Ventilation Management
1. Hypocapnic cerebral vasoconstriction provides anesthesiologists
with a powerful tool for manipulating CBF and CBV.
2. Hyperventilation is routinely used to provide brain relaxation and
optimize surgical conditions.
3. Because hyperventilation decreases CBF, it has the theoretical
potential for causing or exacerbating cerebral ischemia.
4. During neurosurgical procedures, it is reasonable to maintain the
PaCO2 between 30 and 35 mm Hg .
5. The duration of effectiveness of hyperventilation is limited.

29. E. Fluids and Electrolytes
1. To maintain adequate cerebral perfusion, adequate intravascular volume should be
maintained (euvolemia to slight hypervolemia).
2. To minimize brain edema, it is important to maintain serum tonicity.
F. Glucose Management
1. The combination of hyperglycemia and cerebral ischemia appears to be particularly
deleterious. Nevertheless,
tight glycemic control (80–110 mg/dl) with insulin may be associated with an increased
mortality rate at 90 days.
In the neurosurgical population, intensive insulin treatment
results in increased variability in the blood glucose concentration, leading to cerebral
osmotic shifts and higher incidences of hypoglycemia, leading to worse outcomes.

30. Anesthesia for the Sitting Position
The sitting position may be used for
posterior approaches to the cervical
spinal column and for operations
involving the posterior cranial fossa

31. Figure show the Standard sitting position. (From Milde LN. The
head-elevated positions. In: Martin JT, Warner MA, eds.
Positioning inAnesthesia and Surgery. 3rd ed. Philadelphia: WB
Saunders: 1997:71-93

32. Alternative positions for these procedures include park
bench, prone, and supine with the head turned to the
side.
Patients requiring cervical spine operations should be carefully
evaluated preoperatively because decreased cervical range of
motion.
Positioning for patients with posterior fossa tumors should be
approached with the knowledge that brainstem structures may be
adversely affected by compression and that obstructive
hydrocephalus may result in elevated intracranial pressure

33. Advantages to the Sitting Position for Surgery
 Decrease Blood loss
 Increase Surgical exposure with less tissue retraction
 Increase Access to the tracheal tube, extremities, and chest
 Decrease Facial swelling
 Decrease Intracranial pressure by increase drainage of both venous
blood and cerebrospinal fluid

34. Complications Associated with the Use of the
Sitting Position for Surgery
 Circulatory instability
 Cranial nerve dysfunction
 Impaired venous drainage
 Paradoxical air embolism
 Peripheral nerve injury
 Postoperative central apnea
 Quadriplegia
 Tension pneumocephalus
 Venous air embolism

35. COMMON SURGICAL PROCEDURES
A. Surgery for Tumors
B. Pituitary Surgery
C. Cerebral Aneurysm Surgery
and Endovascular Treatment

36. A. Surgery for Tumors
The fundamental anesthetic considerations in tumor surgery are:
1-proper positioning of the patient to facilitate the surgical approach
2. Preoperative assessment of the level of consciousness and a
review of relevant radiologic studies should be performed.
3. Adequate brain relaxation is typically achieved with a standard
anesthetic, including (sub-MAC volatile anesthesia, an opioid
infusion, mild to moderate hyperventilation, and mannitol).

37. B. Pituitary Surgery
1. These patients should undergo a preoperative evaluation of their
hormonal function to detect hypersecretion of pituitary hormones.
2. Intraoperative monitoring of glucose and electrolytes is essential

38. C. Cerebral Aneurysm Surgery and Endovascular Treatment
Patients with aneurysmal SAH are at risk for numerous
complications that may affect the anesthetic plan.
These complications include:
cardiac dysfunction, neurogenic or cardiogenic
pulmonary edema, and hydrocephalus, as
well as further hemorrhage from the aneurysm.

39. ANESTHESIA FOR SPINE TRAUMA AND COMPLEX
SPINE SURGERY
a. Patients with a confirmed cervical spine injury should be
immobilized in either a cervical collar or halo device.
b. A rapid sequence induction RSI remains a viable option, particularly
in patients who are unable to cooperate with an awake procedure.
c. The most conservative approach to airway management in the
presence of known cervical spine injury is
awake fiberoptic endotracheal intubation

40. Patient Positioning
The prone position provides unique challenges to the
anesthesiologist with respect to achieving adequate
protection of the patient from pressure
points (eyes, face, breasts, genitals, knees, toes).

41. Complications of Anesthesia for
Spine Surgery
1. Autonomic Hyper reflexia
2. Postoperative visual loss
(POVL)

42. Thank you