Sub arachnoid block failure

By Dr.Ayshvarya

Guide: Dr Sendhil Kumar Mohan

Moderator: Dr.N.Jothi

K.A.P.V.G.M.C, TRICHY

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

Prevention

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 & motorFailure 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 anaestheticresistance

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

MANAGEMENT

OF

FAILURE

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

Ad

van

tage

s :

Disad

vantages:

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