Sub arachnoid block failure

By Dr.Ayshvarya
M.D Post-Graduate
Guide: Dr Sendhil Kumar Mohan
Dr.R.Selvakumar.M.D.D.A.DNB
Moderator: Dr.N.Jothi
K.A.P.Viswanatham Govt Medical College
Trichirapalli
Tamilnadu-India

Neuraxial Blockade involving injection of local anaesthetic in the
sub-arachnoid space
Spinal anesthesia can be classified as a failure if the surgical
operation cannot be performed without the addition of general
anesthetic or an alternative regional block
No blockade
Inadequate Block for the surgery

The incidence of failure with spinal
anesthesia varies in different studies,
ranging from 3% to 17%.
In some smaller studies, failure rates
as high as 30% have been reported
More among unsupervised trainees

clinical technique
inexperience
failure to
appreciate the
need for a
meticulous
approach

Lumbar
Puncture
Drug
Solution
Injection
Spreading
Of Drug
Through
CSF
Drug
Action On
The
Spinal
Nerve
Roots And
Cord
Subseque
nt Patient
Managem
ent

Patient positioning
Needle insertion
Failed lumbar puncture

Aim is to optimize the pt’s position
& prevent any movement
anxiolytic premedication
local anaesthetic infiltration at the
puncture site

 Abolishing the natural lumbar lordosis by flexing maximally the whole
spine (including the neck), the hips, and knees increases the space
between the lumbar laminae and spines
 Sitting or Lateral
Lateral Position

 Sitting position confers the advantage of
making the midline easier to identify, particularly in obese
patients
increases hydrostatic pressure in the CSF, which may make
spinal needle placement and fluid aspiration easier

 Approach
 Midline approach
 Can be angulated cephalad when resistance
is felt
 Lateral/Paramedian approach- when the
ligaments are calcified
Mental picture of the spinal anatomy &
Appreciation of loss of resistance

 Size 18 to 25G do not affect the
success rate
 Thinner needles, greater tendency to
deviate, slower appearance of CSF in
the hub, more chances of failure

 Opening is proximal to the tip to prevent PDPH
 Small displacement can cause drug deposition in epi/subdural space
 Opening is longer than in Quincke’s, resulting in dura acting as a flap valve
across the opening

Dry tap
The needle & stylet should be
checked for any block
Pseudolumbar puncture
Needle should not be
inserted without the stylet

 A fully effective dose
should be both chosen
and actually deposited
in the CSF
DRUG
SOLUTION
INJECTION
ERRORS

Determines the quality & duration of the
block
Factors influencing intrathecal drug
spread & the LA drug
With low-dose, selective or U/L spinal
anesthesia, the proper technique more
important than with higher doses.
whole of the dose must be delivered into
the CSF, including the dead space of the
needle.
DOSE
SELECTION

 Connection between
syringe and needle
provides a ready
opportunity for leakage
of solution
The syringe containing
the injectate must be
inserted very firmly into
the hub of the needle to
prevent such leaks
LOSS OF
INJECTATE

Anterior or posterior displacement of the needle tip, while
 attaching the syringe to the needle
 aspiration to confirm free flow of CSF
 force of the injection of the syringe contents
Misplaced
injectionSubdural
injection
of drug
High sensory block,
sparing of
sympathetic & motor
Failure of block

Good fixation of the needle -prevents displacement
Rotation of the needle

• Kyphosis, or scoliosis
• Ligaments can form complete septae
within the theca acting as barriers to the
spread
• Spinal stenosis
• Sequelae of previous intrathecal
chemotherapy
• Cysts within the subarachnoid space-
saccular dilatations of the septum
posticum
Anatomical
Abnormalities
INADEQUATE
INTRATHECAL SPREAD

Lumbar CSF volume variability
• dural ectasia in marfan’s, & some connective
tissue disorders
Pre procedural USG can be of help in
identification & managament of difficult spinal

 Iso & Hypobaric – spread is less predictable
 If lumbar puncture is performed at L4-L5 or the lumbo-sacral interspace, the
LA may be ‘trapped’ below the lumbar curve (sitting posture)-saddle block
SOLUTION DENSITY

Identification
errors
Concentration
errors
Alkaline pH of
CSF altering pKa
of LA, bloody
tap
Loss of potency
Chemical
incompatibility
• Precipitation or
decreasing the
concentration of the
un-ionized fraction
Local
anaesthetic
resistance
INEFFECTIVE DRUG ACTION

Anxious patients
Requires good preoperative patient counseling followed
by a supportive approach, with intraoperative sedation
FAILURE OF SUBSEQUENT MANAGEMENT

Advisable to start testing in the lower segments, where
onset will be fastest, and work upwards.
Proving early on that there is some effect encourages
patient confidence; testing too soon does the opposite

 Problems of inadequacy & duration can
be solved by using either continuous
spinal or combined spinal–epidural
techniques
 Introducing a catheter may be difficult in
subarachnoid space
 To Avoid misdirection of LA solution- not
more than 2-3cm in intrathecal space

Salvage the
block
Repeat Spinal
Technique
General
Anaesthesia
Choice for correct
option
Time of onset of failure
Technical difficulty
Complete/Partial
Comorbidities

Partial block No block
Reduced dose Full dose
 It should be performed by an experienced
senior anaesthesiologist.
 Preferably in a sitting position, to avoid high
spinal
 In Partial block, the combination of the 2 doses
should not exceed that considered reasonable
as a single injection for spinal anesthesia

Advantages
• Simple to perform
• Avoids the complications
associated with GA
Complications
• Excessive cephalic spread,
Exaggerated hypotension
• Risk of direct nerve damage
• PDPH
• Multiple attempts- epidural
haemotoma
• If the initial failure-
anatomical reasons, Repeat
spinal- same effect
• Local anaesthetic toxicity

Aspiration of CSF should be attempted before & after injection of
anaesthetic
Sacral dermatomes should be included in evaluation of spinal block
If CSF is aspirated after anaesthetic injection – LA has been delivered
into Subarachnoid space
Avoid reinforcing the same restricted distribution
If CSF not aspirated after injection- tincture of time, carefully assess
the blockade and repeat full dose only if there is no evidence of block

Technique of choice
in Failed spinal
Unpreparedness
Difficult airway
Presence of comorbid
illnesses
Aspiration risk in
emergency
surgeries/CS
Hypotension due to
sympathetic blockade
due to SAB
Advantages:
Disadvantages:

Inadequate spread due to vertebral canal pathology-
 R/O any signs & symptoms of Neurological disease
Investigating local anaesthetic effectiveness
 When series of failures in a short period of time
 Performing skin infiltration with some of the solution intended for
the spinal injection should demonstrate that it is effective

In 1907 Alfred E. Barker wrote that for successful spinal analgesia
it is necessary
‘to enter the lumbar dural sac effectually with the point of the
needle, and to discharge through this, all the contemplated dose of
the drug, directly and freely into the cerebrospinal fluid, below the
termination of the cord’ (Barker, 1907).
Failure to follow the details of this advice is the commonest cause
of a poor result

 Cousins & Bridenbaugh’s Neural Blockade In Clinical Anaesthesia & Pain Medicine
 Complications of Regional Anaesthesia, Brendan T. Finucane
 Br. J. Anaesth. (2009) 102 (6):739-748.doi: 10.1093/bja/aep096First published
online: May 6, 2009
 Pokharel, A. "Study of Failed Spinal Anesthesia Undergoing Caesarean Section and
Its Management." Post-Graduate Medical Journal of NAMS 11.02 (2011).
 Analgesia & Anesthesia in Labor and Delivery By D. K. Baheti
 Basics of Anesthesia, 6th Ed by Ronald Miller

Sub arachnoid block failure

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