By Dr.AyshvaryaM.D Post-Graduate

Guide: Dr Sendhil Kumar MohanDr.R.Selvakumar.M.D.D.A.DNB

Moderator: Dr.N.JothiK.A.P.Viswanatham Govt Medical College

TrichirapalliTamilnadu-India

Sub-arachnoid Block Failure

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

Spinal Anaesthesia

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

Incidence of Failure

clinical technique

inexperience

failure to appreciate the

need for a meticulous approach

Reasons for failure

Lumbar Puncture

Drug Solution Injection

Spreading Of Drug Through

CSF

Drug Action On The Spinal

Nerve Roots And

Cord

Subsequent Patient

Management

Phases in administering a

Spinal anaesthesia

Mechanisms of failure &

their Prevention

Patient positioning

Needle insertion

Failed lumbar puncture

Lumbar Puncture

Aim is to optimize the pt’s position & prevent any movement

anxiolytic premedication

local anaesthetic infiltration at the puncture site

Patient Positionin

g

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

Poor Patient Positioning

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

Needle Insertion

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

NEEDLE FACTORS

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

Pencil point needles

Dry tapThe needle & stylet should be checked for any block

Pseudolumbar puncture

Needle should not be inserted without the stylet

Failed Lumbar

Puncture

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 injection

Subdural injection of drugHigh

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 Abnormaliti

es

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

TESTING THE BLOCK

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

Catheter and

combined

techniques

MANAGEMENT OF

FAILURE

Salvage the

block

Repeat

Spinal Technique

General

Anaesthes

ia

Options in

Managing a

Failed Spinal

Choice for correct option

Time of onset of failure

Technical difficulty

Complete/Partial

Comorbidities

REPEAT SPINAL

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

REPEAT SPINAL

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

Recommendations for Anesthetic Administration after a “FAILED SPINAL”

Technique of choice in Failed spinal

UnpreparednessDifficult airwayPresence of comorbid illnessesAspiration risk in emergency surgeries/CSHypotension due to sympathetic blockade due to SAB

Advantages

:

Disadvanta

ges:

GENERAL ANAESTHESIA

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

FOLLOW-UP INITIATIVES

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