posterior cranial fossa anatomy,physiology,tumours,various positions,complications, treatment ,anaesthetic management

1. Anaesthetic management of posterior
cranial fossa surgeries
21-Apr-14 1
Moderator:
Dr.Uma.B.R
Associate professor,
Department of anaesthesia,
JJMMC,Davangere.
Presenter:
Dr. Naven Kumar .S
PG in Anaesthesia

2. Introduction
 The duramater is folded on itself
to form partitions which divide the
cranial cavity into compartments
which lodge different parts of
the brain.
 The various folds are falx
cerebri, falx cerebelli,
diaphragm sellae and the
tentorium cerebelli.
 Tent shaped fold of dura mater
21-Apr-14 2

3. 21-Apr-14 3

4. Posterior Fossa Surgery
 Posterior cranial fossa: It is the
deepest and most capacious of the 3
cranial fossae.
 It contains the cerebellum, pons, and
medulla oblongata with many vital
centers.
 Tumors in the posterior fossa are
considered critical brain lesions.
 This is, primarily, because of the
limited space within the posterior
fossa and the potential involvement
of vital brain stem nuclei21-Apr-14 4

5. 21-Apr-14 5

6. Anatomy
Boundaries :
 Anteriorly : clivus, petrous part
of temporal bone
 Posteriorly : occipital bone
 Laterally : squamous and
mastoid part of the temporal
bone
 Superiorly : tentorium cerebelli
 Inferiorly : Foramen magnum
21-Apr-14 6

7. Contents :
 Cerebellar hemispheres, large
portion of the brainstem (lower
midbrain, pons and upper medulla)
 3rd to 12th cranial nerves nuclei
and many efferent and afferent
fiber tracts that connect the
brain with the rest of the body.
Blood supply :21-Apr-14 7

8. Contents
21-Apr-14 8

9.  Tumors arising from the
structures above the
tentorium cerebelli are
called supratentorial (80%)
and those arising from below
are called infratentorial
tumors(20%).
 Supratentorial are seen more
commonly in adults and
infratentorial are seen more
commonly in children.21-Apr-14 9

10. Classification of Brain Tumours
1. Neuroepithelial tumors
a) Gliomas; astrocytomas,
oligodendromas, ependymoma,
b) Pineal tumors
c) Neuronal tumors-gangliomas ,
neuroblastoma
d) Medulloblastoma
2. Nerve sheath tumor-acoustic
neuroma
3. Meningeal tumor
4. Pitutary tumor
5. Germ cell tumor-germinoma,
teratoma
6. Lymphoma21-Apr-14 10

11. ANATOMICAL REGION CLINICAL SIGNS
Supratentorial (forebrain) Seizures
Headache
Motor/ sensory deficits
Infratentorial (brainstem)
(RAS, CN, Cardiac & resp
centres)
- CN deficit (3-12)- ocular
palsy, dysphagia,
laryngeal dysfunction
(chronic aspiration).
- Arrhythmias/ respiratory
irregularities
Sleep abnormality
Infratentorial
(cerebellum)
Ataxia
Tremors
Vestibular signs
Hydrocephalus
Infratentorial (vestibular
system)
Head tilt
Postural deficit
Nystagmus
How do they present ?
21-Apr-14 11

12. Herniation / midline shift
HTN
Tachy/ brady
arrythmias
3 & 6th CN palsy
(I/L pupil
dilation + no
light reflex)
C/L hemiplegia/21-Apr-14 12

13. Cerebellar Herniation Through Foramen Magnum
21-Apr-14 13
Vomiting Opisthotonus
Head tilt Downbeat nystagmus
(vertical nystagmus)
Meningismus Bulbar palsies with
vocal cord paralysis
Muscle spasm
Skew deviation of the
eyes
typical ‘posturing’
from tonsillar
herniation may be

14. Cerebellar herniation:
 Swallowing and gag dysfunction
 Occipital headache
 Neck pain
 Coughing may induce paroxysms of
increased symptoms including loss of
consciousness as the tonsils are further
impacted into the foramen magnum
 Further herniation compresses the
medulla
irregular respiration and death may21-Apr-14 14

15.  Success with surgical intervention
has become possible because of:
1.Advances in imaging and
microsurgical techniques
2.Improved understanding of
physiology
3.Advances in perioperative care
of the patient
4.Excellent anaesthetic
techniques available21-Apr-14 15

16. Treatment
Chemotherapy
Surgical
resection
Radiotherapy
21-Apr-14 16

17. Goals of Anaesthesia
1.Preserve both injured &
uninjured cerebral territories
by global maintenance of
cerebral homeostasis.
2.Maintain normocarbia,
normotension, normoxia,
euthermia, euglycemia.
3.Avoid secondary brain insults
4.Optimizing operative conditions21-Apr-14 17

18. Anaesthetic implications
Depending on type (vascularity) and location
(supra/ infratentorial) of tumor
Supratentorial
ICP management
Monitoring brain function
Massive intraoperative
hemorrhage
Seizures
Air embolism (if venous
sinuses traversed)
Infratentorial
Positioning
Care during vital
structure handling
Air embolism
Higher mortality
21-Apr-14 18

19. Secondary insults:
INTRACRANIAL SYSTEMIC
Increased intracranial
pressure
Hypercapnia/hypoxemia
Epilepsy Hypo-/hypertension
Vasospasm Hypo-/hyperglycemia
Herniation: falx, tentorium,
foramen magnum, craniotomy
Low cardiac output
Midline shift: tearing of
cerebral vessels
Hypo-osmolality
Shivering/pyrexia
21-Apr-14 19

20. Tumors
Disruption of cerebral
autoregulation
BP fluctuation poorly tolerated
↑BP – Vasogenic edema, ↑ tumor /
aneurysm size, aneurysmal
rupture
↓ BP – Ischemia/ infarction
WHY CONTROL BP ?
21-Apr-14 20

21. Pre Op Assesment:
HISTORY
 Level of consciousness
 Seizures - ↑ CMRO2 , ↑ ICP
 ↑ ICP – headache, vomiting, blurred
vision, ocular palsy (CN 6)
 Hydration – fluid intake, NPO status,
diuretics
 Focal neurological signs
 Paraneoplastic syndromes
 Regurgitation of solids and liquids
 Disturbances in balance and
21-Apr-14 21

22. •History of drug intake:
I.Diuretics-elecrolyte
disturbances
II.Steroid therapy-hyperglycemia
(cerebral ischemia),HPA
suppression,mucosal effect on the
GIT
III.Antiepiletic drugs-phenytoin,
carbemazapine increase the dose of
NMJ blockers21-Apr-14 22

23. History :
 CN palsies- dysphagia, laryngeal
dysfunction.
Associate systemic illness-
 Cardiac – HTN
 Respiratory – aspiration, pulmonary
infections.
 SIADH, DI.
21-Apr-14 23

24. Physical examination
1.General physical examination
2.Detailed CNS examination - GCS
 ↑ICP – papilloedema, cushing response
(↑BP, ↓HR), sutural diastasis, bulging
fontanels.
 Focal signs (CN palsies) - Dysphagia,
strabismus, focal seizures, speech
deficit, motor & sensory examination.
 Midline shift - I/L Pupillary dilatation
and absent light reflex (3rd CN)
21-Apr-14 24

25. a)Cardiorespiratory status evaluation-)
 Respiratory- effect of positioning, resp.
pattern, neurogenic pulm. Edema
 Significant for elderly and those with
cardiac disease
 Limited cardiorespiratory reserve may
limit the positioning
 Risk of orthostatic hypotension
increased in people with uncontrolled
hypotension
 CVS – HTN (resets limits of cerebral
autoregulation), BP (cerebral
b)Evaluation for patent foramen ovale-
21-Apr-14 25

26. Investigation:
For surgery:
1. Complete hemogram
2. Blood sugar(hyperglycemia –
cerebral edema , ↑ischemic brain
injury),Electrolytes
3. Renal function tests
4. Coagulation profile
5. ECG – ischemic changes, arrhythmias
6. CXR, Cervical spinal x-ray if planned
for sitting position
21-Apr-14 26

27. For diagnosis of lesion: various
modalites like CT/MRI are used in
imaging of tumour helps in anaesthetic
plan
21-Apr-14 27
Location Silent/Eloquent Area
Size Degree Of Compromise Of
Intracranial Dynamics
Including Auto Regulation
Midline Shift Ventricular
Distortion/Csf
Obstruction
Perilesional Edema Makes Tumor Functionally
Better
Contrast
Enchancement
Degree Of Bbb Disruption
Proximity To Venous
Sinuses
Blood Loss

28. Premedication
Advantage
It can decrease
the stress
ICP
vasogenic edema
Disadvantage
Hypercapnia
Hypoxia
Airway
obstruction ICP
21-Apr-14 28
Midazolam- 0.5mg to 2.0mg i.v
Fentanyl -1-2 μgm/kg
Sufentanil – 0.1- 0.4μgm/kg iv

29. Premedication
 Steroids should be started atleast 2-3
days before an elective surgery and
continued upto the day of surgery
 In case if HPA axis supression 100mg
methylprednisolone should be given
before surgery
 H2 blockers – ranitidine – 50mg iv
 Prokinetic agents - metoclopramide
10mg iv
 Anticonvulsant therapy – phenytoin –
loading dose 10-15mg/kg iv and the21-Apr-14 29

30. Monitoring
21-Apr-14 30
Non invasive monitoring Invasive monitoring
ECG Invasive blood pressure
NIBP Intra-arterial catheter
Oxygen saturation Central venous pressureCVP
-VAE (diagnostic +
therapeutic )
Temperature Pulmonary artery
pressure/cardiac output
ET-CO2
•urinary output
Neuromuscular
monitoring

31. Special monitoring
• Multiorifice right atrial
catheter
• precordial doppler
• et-N2
• Transesophageal echo (TEE)
• Transcranial Doppler
• jugular venous bulb monitoring
• Eletrophysiological monitoring
21-Apr-14 31

32. Electrophysiological monitoring during
posterior fossa surgery:
 Information about the integrity and
function of spinal cord, brainstem,
cranial nerves and cortex can be
obtained to assist in detecting
intraoperative compromise or to predict
postoperative function.
 EEG, Somatosenory evoked potentials
(SSEP), Motor evoked potentials (MEP),
and BAER and cranial nerve monitoring
can be used singly or in combination.
21-Apr-14 32

33. Special monitoring
 SSEP useful for detection of
cervical cord ischemia or stretch
injury in sitting position.
 Volatile anesthetic agents, N20,
physiologic changes and
temperature may affect the
latency and amplitude of cortical
components.
 Also damage to posterior
descending motor tracts may be
21-Apr-14 33

34. Special monitoring
 BAER: Brain stem auditory evoked
responses are robust and are
resistant to depressant effects
of anesthetics.
 Monitoring of BAER provides a
means of assessing
intraoperative function of eighth
cranial nerve and brainstem.
21-Apr-14 34

35. Special monitoring
 Facial nerve potentials: Facial
motor evoked potentials (MEP)
occur when facial nerve is
stretched or stimulated
successful preservation of facial
nerve during resection of CP
angle tumors has been reported
using Facial MEP. Use of muscle
relaxants must be limited during
these procedures.21-Apr-14 35

36. Induction
GOALS – Normotension, Normocarbia,
Normoxia
Preoxygenation
P/M – opioid (fentanyl 1-2 μg/kg )
I/W – Thiopentone (3-5 mg/kg)
Propofol (1.5 – 2.5 mg/kg)
Myorelaxation – Sch (transient ↑ ICP)
Use intermediate acting relaxants
Atracurium – histamine release ( cerebral vasodilatation)
Vecuronium, Rocuronium – commonly used
Only after adequate muscle relaxation achieved, perform quick + gentle laryngoscopy
Intubation – armoured ETT
Tape on opposite side of surgery
Bandaging may ↓cerebral venous return
Controlled ventilation
Lignocaine , Esmolol, 2nd
dose of i.v induction agent
60-90 sec earlier
21-Apr-14 36

37. Positioning
GOAL- Slow and gentle positioning with 15-
20⁰ head up tilt to aid cerebral venous drainage
Verify cautiously – 1. All potential pressure points p
2. Eyes protected & padded
3. Peripheral pulses palpable
4. Nerve compression absent
5. Ventilation adequate ( PEEP, ETT posit
ETT – Kinking in post. Oropharynx
Advancement / extubation
Neck – Extreme rotation / flexion may cause ↑ ICP,
quadriparesis, tongue swelling
Head pins – Adequate plane of anaesthesia
Local infiltration / bolus opioid (fentanyl)
21-Apr-14 37

38. Positioning
 It very important in posterior
cranial fossa surgeries as it
causes various hemodynamics
changes
 Positioning per se will be
discussed after the anaesthetic
part
21-Apr-14 38

39. Dural opening in presence of high ICP –
- sudden decompression &
transcalvarial herniation
- herniated tissue cannot be
interposed back
- permanent neural damage
ICP to be brought within normal limits
before opening the dura.
Methods – head elevation, mannitol,
Optimization of ICP
21-Apr-14 39

40. Factors that Increase ICP
 Inadequate
muscle
relaxation
 Poor cerebral
venous drainage
 Jugular venous
obstruction
 Extreme neck
rotation/
flexion
 PEEP
 Raised
intrathoracic
presure
 Hypoxia
 Hypercarbia
21-Apr-14 40

41. Mannitol (20%)
Hyperosmolar agent
Dose : 0.5 – 1g/kg i.v. (0.5-1 g/kg over
15 min just before opening dura)
Action reaches peak at 20-30 min.
 Advantages : Draws water from
brain (↓ brain bulk)
↓ Hct (↑CBF , O2 delivery)
 Disadvantages: 1. Transiently ↑
intravasular volume
2. Hypokalemia21-Apr-14 41
Management of ICP

42. Furosemide
Loop diuretic (Na K 2Cl channel
blocker)
Dose : 0.5 – 1 mg/kg i.v.
Steroids
Dexamethasone 8mg iv stat followed
by 4mg q6h
21-Apr-14 42
Management of ICP

43. CSF drainage
1. Lumbar subarachnoid drainage
system
2. Ventriculostomy drain (EVD)
(connected by tubing to a CSF
collection device which can be
elevated or lowered)
 CSF drainage (↑ICP, aneurysm / ENT
surgeries)
 ICP measurement
CSF drainage
– Slow
– bolus ≤ 20-30 ml
Complications
– herniation
– infection
21-Apr-14 43

44. Maintenance OF
Anaesthesia
ANAESTHETIC
AGENT
VOLATILE
ANAESTHETIC
I.V. ANAESTHETIC
PROS 1. Easy
2. Extensively
available
1. Intact CBF – CMRO2
coupling
2. ↓brain bulk
CONS 1. ↑ICP 1. Short acting
RECOMMENDATION 1. Use in short,
uncomplicated
surgeries
2. At < 1.5 MAC
3. Avoid
combination
with N2O
1. Use in cases with
high risk of ↑ICP/
brain bulk
21-Apr-14 44

45.  Commonly used technique are opioid-
inhalation anesthetics-NMBA or nitrous
oxide -opioid -NMBA techniques along
with controlled ventillation.
 Isoflurane and sevoflurane are the
preferred inhaled anesthetics (do not
increase the CBF upto 1-1.5 MAC.)
 Concomittant use nitrous oxide and
volatile agents is avoided due to
increase in the CBF.
21-Apr-14 45
Maintenance OF Anaesthesia

46. Maintenance (cont…)
FLUID THERAPY
Principle – BBB is selectively permeable
Water crosses freely, most ions
(Na+) don't.
If BBB disrupted (ischemia, head injury,
tumors) – hyperosmolar agents may ↑brain
water instead of drawing water out.
21-Apr-14 46

47. RECOMMENDATIONS (FLUID RESTRICTION)
1.FLUID LOSS – Maintain euvolemia
2.BLOOD LOSS – Assessment difficult (drapes
+ continuous irrigation)
3.SERUM OSMOLARITY –
 Maintain at 305- 320 mosm/L
 Give NS (309 mosm/L)
 Use RL ( 272mosm/L) alternately
 Avoid glucose containing solutions
(5%D , DNS)
 Mannitol (0.5 – 2 mg/kg)
 Furosemide (0.5 - 1mg/kg)
21-Apr-14 47

48. NEUROPROTECTION
a)PaO2
b) PaCO2 (30-35mm Hg)
c) BP
d) Glucose ( <170 mg/dL )
e) Temperature ( controlled
hypothermia 32-34⁰C)
f) Analgesia (opioid infusion)
g) Adequate depth of anaesthesia
h) Seizure prophylaxis
21-Apr-14 48

49. The chemical brain retractor concept
 Mild hyperosmolality
 Adequate head-up positioning
 Lumbar cerebrospinal fluid
drainage
 Intravenous anesthetic agent
(propofol)
 Avoidance of brain retractors
 Venous drainage: jugular veins free
21-Apr-14 49

50. Reversal
 Most patients undergoing craniotomy
can be extubated if neurological
status is intact.
 Extubation as smooth, without coughing
,straining or bucking against the
tracheal tube.
 To avoid bucking muscle relaxation
should be reversed after the head
dressing .
 Inj lidocaine 1.5mg/kg iv or esmolol
1mg/kg can be given to suppress the
hemodynamic responses.
 Neuromuscular blockade reversed with
21-Apr-14 50

51. Emergence
Most important but often neglected
“ A well planned procedure is often
rewarded by a fully awake patient who is
appropriately responding to verbal
commands and neurological
examination.”
Due to pain and shivering, associated with
•↑ catecholamine release
•↑ O2 Consumption
AIMS
 To maintain intra + extracranial
homeostasis
(MAP- CPP- CBF- ICP- CMRO2 - PaO2 - PaCO2-
temp)
Avoid intracranial bleed ( coughing,
ventilator fight)
21-Apr-14 51

52. Emergence (cont…)
EARLY AWAKENING LATE AWAKENING
1.Early
neurological
examination &
reintervention
2.Less ↑BP/
catecholamine
burst
3.↓ cost of postop
1.Less risk of
↓O2,↑CO2
associated with
anaesthesia
hangover
2.Better
respiratory &
hemodynamic
control21-Apr-14 52

53. Emergence (cont…)
Checklist for early extubation
1. Good preop GCS (>8)
2. CVS stability + normothermia + normoxia
3. Durationbrain surgery
4. No extensive post fossa manipulation ( CN
9 – 12)
21-Apr-14 53

54. Indication of late extubation
1. Low GCS
2. Inadequate airway control
3. Intraop catastrophe
4. Brain edema/ deranged cerebral
homeostasis
(long duration/ extensive/ repeat
surgery)
5. Surgery around vital areas
Emergence (cont…)
21-Apr-14 54

55. Immediate postoperative concerns
1.Failure to awaken
Nonanaesthetic causes – seizures,
cerebral edema, intracranial
hematoma, pneumocephalus,
metabolic/ electrolyte
disturbance.
Anaesthesia hangover – opioid,
volatile anaesthetic, muscle
relaxant.
21-Apr-14 55

56. Immediate postoperative concerns (cont….)
2. Post operative care
a) Head end elevation (15-30⁰)
b) Adequate ventilation & oxygenation
c) Monitoring of neurological function
d) Check for serum electrolytes and
osmolarity (mannitol, frusemide to
continue)
e) Seizure prophylaxis (phenytoin /
fosphenytoin)
f) Seizure treatment (thiopentone 50-100
mg, midazolam 2-4 mg , lorazepam 2 mg)
21-Apr-14 56

57. Immediate postoperative concerns (cont….)
g) SIADH
Hyponatremia, S. hyposmolarity,
high U. osmolarity
T/T restrict free water intake
h) DI
After pituitary surgery
Hyponatremia, S. hyposmolarity,
low U. osmolarity
T/T ↑ water intake, vasopressin ,
desmopressin
i) Tension pneumocephalus
 Skull X ray / CT
T/T opening the dura
21-Apr-14 57

58. Concerns:
Cranial nerve palsies (IX, X) may
impair gag reflex- aspiration
Hydrocephalus
Cerebellar dysfunction
Edema in floor of fourth ventricle-
damage to resp. centers
Bradycardia and hypertension – due
to V nerve stimulation (resolve with
cessation of stimulus)
Bradycardia, asystole/21-Apr-14 58

59. Positioning
Various positions:
 Sitting
 Prone
 lateral(park bench) &
 Semilateral (janetta) positions
21-Apr-14 59

60. Sitting Position
Advantages:
– Excellent surgical access
– Facilitates hemostasis (decreased
blood loss)
– Improved venous and CSF drainage
– Exposes face for monitoring
response to cranial nerve
stimulation (though this can also
be done electronically
21-Apr-14 60

61. Disadvantages:
 Hemodynamic Instability
 Venous Air Embolism
 Paradoxical Air Embolism
21-Apr-14 61

62. Physiologic changes in sitting position
 CVS-decreased MAP,SBP,SV,CO,CI,PCWP,
reflex tachycardia, and increased
SVR
 RS-Increased FRC ,FVC, easier
diaphragmatic excursion, lower
airway pressures.
 CNS-decreased CBF&CPP. MAP
decreases by 0.77mmHg for every cm
gradient above the heart
 In patients who cannot tolerate an21-Apr-14 62

63. Contraindications
 Known intracardiac shunts (ASD, VSD,
PDA, PFO)
 Known pulmonary arteriovenous shunts
 Severe hypovolemia
 Orthostatic hypotension
 Symptomatic cervical spine disease
 Elderly(>65 years)
 Uncontrolled hypertension
21-Apr-14 63

64. Sitting Position
 Patient is semi recumbent
 Back increased to 60 degrees
 Leg elevated to promote venous return
 Knees flexed at level of the heart
 Head is fixed in a three point holder
with the neck flexed
 Poles have to be attached to the back
of the table (thoracic piece)-easy for
resuscitation
 Arms remain at the sides with hands
resting on the lap21-Apr-14 64

65. Optimized sitting position—the legs are elevated to the level of the heart.
Engelhardt M et al. Br. J. Anaesth. 2006;96:467-472
21-Apr-14 65

66. Sitting Position
Measures to avoid hypotension
 Pre-positioning hydration
 Wrapping of legs with elastic
bandage to counteract
gravitational shifts of blood
 Incremental adjustment of
table position
 Pressor administration may be
required
21-Apr-14 66

67. Lateral Position
 Increased risk of bleeding from the
sinuses(transverse and sigmoid)
 Less incidence of air embolism
 Shoulder roll-to protect the inferior
shoulder and axillary neurovascular
structures
 Lateral popliteal nerve palsy
 The superior shoulder in broad
shouldered or short neck patients may
hinder surgeons line of sight21-Apr-14 67

68. Prone Position
 Useful for lesions at or near the
midline or near the fourth
ventricle
 More commonly used in children
 Head is usually elevated to assist
in gravity dependent venous
drainage
 Does not avoid problems of
hypotension or air embolism
21-Apr-14 68

69. PARK BENCH POSITION
 Allows rapid access to the
cerebellar hemisphere-rapid
positioning
 Used for both lateral and midline
lesions
 By turning prone, the upper
shoulder is moved out of the
surgeons way
 High risk of neck twisting and
venous obstruction
21-Apr-14 69

70. Complications in Posterior Fossa
Surgeries
– Air embolism (venous and arterial)
– Cardiovascular instability
• Hypotension
• Venous pooling
• Cardiac arrhythmias
– Neurologic complications
• Quadriplegia
• Nerve injuries (e.g. ulnar, sciatic,
lateral peroneal)
– Pneumocephalus
– Airway obstruction
– Airway swelling (head and tongue)21-Apr-14 70

71. Venous Air Embolism (VAE)
 Facilitation of air entry by sub
atmospheric pressure in an opened vein
 Presence of non collapsible venous
channels such as diploic veins and dural
sinuses
 Children experience greater haemo
dynamic derangements from VAE than
adults
21-Apr-14 71

72. Severity Of VAE
Depends on:
 Rate and volume of air entrained
 Degree of head elevation
 Negative pressure between RA and
surgical site
21-Apr-14 72

73. Pathophysiology Of VAE
 Slow continuous entrainment-
mechanical obstruction and local
hypoxemia, reflex vasoconstriction
& pul HTN, decreased venous return
and CO
 Release of cytokines &
inflammatory mediators , further
vasoconstriction &
Bronchoconstriction.
 Hypoxemia, increase dead space
ventilation, impaired gas exchange,
increased airway pressure.
21-Apr-14 73

74. Pathophysiology Of VAE
 Rapidly entrained air bolus
results in air lock within the right
side of the heart
 Volume of 5ml/kg exceeds the
pulmonary arterial capacity
 Blockage of RVOT ,acute RV
dilatation and failure, myocardial
and cerebral ischemia,
dysrhythmias and cardio vascular
collapse21-Apr-14 74

75. Diagnosis of VAE
 Hypotension
 Dysrhythmias
 Tachycardia
 Drop in etCO2
21-Apr-14 75

76. Complications of VAE
21-Apr-14 76

77. Detection of VAE
 Esophageal stethoscope
– Mill wheel murmur
 Precordial Doppler
– Most sensitive noninvasive device
(0.2ml/kg)
– 2.5 MHz continuous ultrasonic signal
– Small volumes of air are detected
as air is a good acoustic reflector
– Place just to the right of sternum
above the xiphoid between second –
fourth intercostal space21-Apr-14 77

78. Detection of VAE
 Capnography
– Has a specific role for air embolism
– Detects increased arterial to end-
tidal CO2 gradient
 End tidal Nitrogen monitoring
– More specific for air
– Earlier detection than ETCO2
 Pulmonary artery catheter
– Detects pulmonary hypertension
resulting from mechanical
obstruction
21-Apr-14 78

79. Detection of VAE
 Transesophageal echocardiography
– 3.5 – 5 MHz probe
– Detects even 0.02ml/kg of air when it
is in the right side of the heart
– Used for screening anesthetized
sitting patient for PFO
 Transcranial monitoring of MCA
 Standard of care – Precordial doppler
and etCO2
21-Apr-14 79

80. Relative sensitivity of techniques to monitor for
VAE
21-Apr-14 80

81. Prevention of VAE
 No maneuver is 100% effective
 Incidence is decreased by
– Adequate hydration
– Avoiding hypovolemia
– Proper wrapping of lower extremities
– Good surgical exposure with careful
dissection
– Liberal use of bone wax
– Avoidance of nitrous oxide
– Minimizing head elevation
21-Apr-14 81

82. Management of VAE
 Prevent further air entry
– Notify surgeon
– Pack or flood surgical field
– Jugular compression
 Change patient position
–Lower head end
–Lateral position with right
side up (Durant position)
21-Apr-14 82

83. Management of VAE
 Treat intravascular air
– Aspirate via right heart catheter
– Discontinue nitrous oxide
– FIO2 of 1
– Pressors or inotrope to support
cardiovascular instability
 Chest compressions
21-Apr-14 83

84. Treatment of VAE
 Postoperative Goals
– Provide supplemental O2
– Perform ECG, chest X ray
examination
– Measure serial arterial blood
gases
– If arterial air emboli are
suspected, provide hyperbaric
compression if available21-Apr-14 84

85. Paradoxical Air Embolism
 Passage of air across the
interatrial septum through a
probe patent foramen ovale
 PFO present in 25% of all adults
 Incidence of 5-10%
 Predisposing factors- significant
increase in pressure in the right
side of the heart and hypovolemia
 TEE -more sensitive in picking up PFO
21-Apr-14 85

86. Pathophysiology
 Occurs when RA pressure is more than LA
pressure.
 Pressure gradient required to open a
PFO is 5 mm of Hg.
 Use of PEEP increases the incidence of
PAE.
 Consequences of PAE- systemic emboli
(cerebral and coronary emboli)
21-Apr-14 86

87. PNEUMOENCEPHALUS
 Presents as delayed awakening or
non awakening in the immediate
post operative period or as severe
headache
 Air enters the supratentorial
space in the upright position
 Use of nitrous increases the
incidence of Pneumoencephalus
 Diagnosis- brow up lateral
radiograph21-Apr-14 87

88. Brainstem Stimulation
 Irritation of lower portion of
pons, upper portion of medulla
and extra axial portion of the
5th cranial nerve
 Manipulation of 9-12th cranial
nerves
 Bradycardia with hypotension
 Tachycardia with hypertension
 Ventricular dysrhythmias21-Apr-14 88

89. Quadriplegia
 Neck flexion resulting in
stretching or compression of the
cord
 Patients with degenerative disease
of the spine may need preoperative
radiologic studies
 May warrant SSEP monitoring
during positioning
21-Apr-14 89

90. Macroglossia
 Swelling of the upper airway
due to edema
 Neckflexion also causes
macroglossia due to edema
occurring at the time of
reperfusion
 Excessive reduction of
anteroposterior diameterof21-Apr-14 90

91. Conclusion
 A thorough knowledge of
Intracranial lesions, adequate
preparation, vigilant monitoring
& post operative care
Results in good patients outcome.
21-Apr-14 91

92. 1. miller’s anesthesia. 7th ed.
2. Stoelting's Anesthesia and Co-Existing
Disease, 5th ed.
3. Handbook of neuroanaesthesia. James
E Cottrell. 4th ed.
4. Clinical anaesthesia procedures of
massachusettes general hospital. 7th
ed.
5. morgan’s clinical anaesthesiology.4th
ed.
6. Wylie 7th edn.
References:
21-Apr-14 92

93. 21-Apr-14 93
THANK Q