ACCIDENTAL SUBDURAL ACCIDENTAL SUBDURAL INJECTIONINJECTION

Presenter :- Dr Teena ChaudharyPresenter :- Dr Teena Chaudhary

Moderator :- Dr Avnish BhardwajModerator :- Dr Avnish Bhardwaj

CASE REPORT

Anaesthesia and Intensive Care, 2010,Vol 38, No. 1D Agarwal, M Mohta, A Tyagi, AK Sethi Department of Anaesthesiology and Critical Care, University College of Medical Sciences and Guru Teg Bahadur Hospital, Delhi, India

A 32-year-old primigravid woman at 41 A 32-year-old primigravid woman at 41 weeks gestation was admitted to the weeks gestation was admitted to the hospital for induction of labor.hospital for induction of labor.

She requested an epidural block for pain She requested an epidural block for pain relief. relief.

Before the procedure, an intravenous Before the procedure, an intravenous infusion of lactated Ringer’s solution 500 infusion of lactated Ringer’s solution 500 ml was given.ml was given.

With the patient in a left lateral With the patient in a left lateral decubitus position, the L1-2 epidural decubitus position, the L1-2 epidural space was easily identified using the space was easily identified using the loss of resistance to air technique loss of resistance to air technique with an 18-gauge Tuohy needle with the with an 18-gauge Tuohy needle with the bevel oriented cephaladbevel oriented cephalad. .

An epidural catheter with an open end An epidural catheter with an open end and three lateral eyes was threaded and three lateral eyes was threaded through the needle with minimal through the needle with minimal resistance without eliciting paresthesia or resistance without eliciting paresthesia or other discomfort. other discomfort.

An estimated 5 cm was left in the An estimated 5 cm was left in the presumed epidural space and aspiration presumed epidural space and aspiration revealed no blood or cerebrospinal fluid revealed no blood or cerebrospinal fluid (CSF).(CSF).

A test dose of 3 ml of 0.67% lidocaine A test dose of 3 ml of 0.67% lidocaine and fentanyl 3 µg/ml with 1:300,000 and fentanyl 3 µg/ml with 1:300,000 epinephrine was injected and the epinephrine was injected and the epidural catheter was secured. epidural catheter was secured.

The test dose produced no detectable The test dose produced no detectable sensory or motor changes after 3 sensory or motor changes after 3 minutes and subsequently 12 ml of minutes and subsequently 12 ml of the same mixture was given by slow the same mixture was given by slow incremental injection over 8 minutes incremental injection over 8 minutes after the patient turned to the supine after the patient turned to the supine position. position.

Fifteen minutes after loading dose Fifteen minutes after loading dose was given, the parturient felt that was given, the parturient felt that contraction pains were much contraction pains were much improved without any motor block. improved without any motor block.

Maternal vital signs and the fetal heart Maternal vital signs and the fetal heart beat recording were within the normal beat recording were within the normal ranges.ranges.

Thirty minutes later, the patient began Thirty minutes later, the patient began to notice numbness in both arms. to notice numbness in both arms.

Testing of sensation to cold revealed Testing of sensation to cold revealed sensory block from T10 to C6. No sensory block from T10 to C6. No significant motor weakness was found. significant motor weakness was found.

The conjunctiva were injected, and she The conjunctiva were injected, and she complained of a stuffy nose.complained of a stuffy nose.

However, neither ptosis nor miosis was However, neither ptosis nor miosis was notednoted. .

There was no loss of consciousness or There was no loss of consciousness or impairment of respiration and speech.impairment of respiration and speech.

Vital signs and fetal heart rate remained Vital signs and fetal heart rate remained stable. Over the next 60 minutes the stable. Over the next 60 minutes the block slowly regressed and labor pains block slowly regressed and labor pains ensued. ensued.

The obstetrician then decided to perform The obstetrician then decided to perform a cesarean section due to failure of labor a cesarean section due to failure of labor progression. progression.

Because of the unusual block pattern, Because of the unusual block pattern, the anesthesiologist decided to perform the anesthesiologist decided to perform spinal anesthesia at a lower level spinal anesthesia at a lower level with enough space for betadine with enough space for betadine skin cleansing skin cleansing

The catheter was retained to facilitate The catheter was retained to facilitate further investigation. further investigation.

After placing the patient in the right After placing the patient in the right lateral position, a lumbar puncture lateral position, a lumbar puncture was performed via the paramedian was performed via the paramedian approach at the L3-4 level using a 26-approach at the L3-4 level using a 26-gauge Greene spinal needle with the gauge Greene spinal needle with the bevel aligned parallel to the long axis bevel aligned parallel to the long axis of the meninges of the meninges

When free flow of CSF was confirmed, When free flow of CSF was confirmed, 0.5% heavy bupivacaine solution 2.2 0.5% heavy bupivacaine solution 2.2 ml was slowly injected without ml was slowly injected without barbotage. barbotage.

A dense lower extremity motor A dense lower extremity motor blockade was obtained and the blockade was obtained and the patient reported sensory block up to patient reported sensory block up to the C6 level without ventilatory the C6 level without ventilatory impairment. impairment.

The operation proceeded smoothly The operation proceeded smoothly and a vigorous male baby, body and a vigorous male baby, body weight 3660 g, was deliveredweight 3660 g, was delivered..

•On the second On the second postoperative day, with postoperative day, with the patient’s permission the patient’s permission and consent, 10 ml of and consent, 10 ml of nonionic contrast medium, nonionic contrast medium, iotrolan, was injected iotrolan, was injected through the catheter to through the catheter to investigate the catheter investigate the catheter position. position. •The spread of the dye The spread of the dye was shown to extend was shown to extend exclusively in the cephalic exclusively in the cephalic direction with some direction with some delineation of the roots delineation of the roots which is characteristic of which is characteristic of subdural injection. subdural injection. Subsequent computed Subsequent computed tomographic (CT)scanning tomographic (CT)scanning confirmed the dye was confirmed the dye was within the subdural spacewithin the subdural space

Lateral post-contrast image suggesting subdural spread (black arrow pointingto “convex anterior bulging” consistent with subdural spread patterns

The patient had an uneventful The patient had an uneventful recovery after the cesarean section recovery after the cesarean section and was discharged with no and was discharged with no neurological deficitsneurological deficits..

ANATOMY OF SUBDURAL ANATOMY OF SUBDURAL SPACESPACE

The subdural space is a narrow potential space The subdural space is a narrow potential space between the arachnoid mater and the dura between the arachnoid mater and the dura mater containing a minute quantity of serous mater containing a minute quantity of serous fluid.fluid.

It extends into the cranial cavity throughout It extends into the cranial cavity throughout the distribution of the meninges, covering all the distribution of the meninges, covering all neural structures.neural structures.

The space ends distally at the lower border of The space ends distally at the lower border of the second sacral vertebra S2, where the filum the second sacral vertebra S2, where the filum terminale becomes invested closely by the terminale becomes invested closely by the dura mater.dura mater.

•The spinal subdural space has greater potential capacity dorsally and The spinal subdural space has greater potential capacity dorsally and laterallylaterally•It is widest in the cervical region and most narrow in the lumbar region. It is widest in the cervical region and most narrow in the lumbar region. •The usual sparing of sympathetic and motor functions associated with a The usual sparing of sympathetic and motor functions associated with a subdural block is due to the anatomy of this spacesubdural block is due to the anatomy of this space•The space is known to extend laterally like a cuff over the exiting dorsal The space is known to extend laterally like a cuff over the exiting dorsal nerve roots. nerve roots. •The arachnoid mater is fixed proximal to the dorsal ganglia and the dura The arachnoid mater is fixed proximal to the dorsal ganglia and the dura mater distal to it, thereby also extending the subdural space over the mater distal to it, thereby also extending the subdural space over the dorsal root ganglia The dura and arachnoid mater are attached together dorsal root ganglia The dura and arachnoid mater are attached together on the ventral root and hence the potential space is much smaller on the ventral root and hence the potential space is much smaller ventrally.ventrally.•Subdural injections thus usually pool in the posterior segment, sparing Subdural injections thus usually pool in the posterior segment, sparing the anterior nerve roots that carry the sympathetic and motor nerve fibresthe anterior nerve roots that carry the sympathetic and motor nerve fibres

•Under electron Under electron microscopy,subdural space has microscopy,subdural space has been studied,wherein the been studied,wherein the arachnoid mater had an outer arachnoid mater had an outer compact laminar portion compact laminar portion attached to the inside of the attached to the inside of the dural sac and a separate inner dural sac and a separate inner trabeculated portiontrabeculated portion•Between the laminar arachnoid Between the laminar arachnoid portion and the dura, a portion and the dura, a compartment termed the dura-compartment termed the dura-arachnoid interface was seen.arachnoid interface was seen.•This dura arachnoid interface This dura arachnoid interface was seen to be composed of was seen to be composed of neurothelial cells having neurothelial cells having relatively few intercellular joints relatively few intercellular joints and large intercellular lacunae and large intercellular lacunae filled with an amorphous filled with an amorphous material material

•This suggested that This suggested that iatrogenic dissection of iatrogenic dissection of this cellular plane can this cellular plane can occur if neurothelial occur if neurothelial cells break up on cells break up on application of pressure application of pressure by mechanical forces by mechanical forces such as air or fluid such as air or fluid injection.injection.•Thus fissures can be Thus fissures can be created within the created within the dura-arachnoid dura-arachnoid interface, with interface, with considerable variability considerable variability in formin form

INCIDENCEINCIDENCE The first case of radiologically confirmed The first case of radiologically confirmed

accidental subdural block was published in accidental subdural block was published in 19751975

Although a number of case reports of accidental Although a number of case reports of accidental subdural injection have been published since subdural injection have been published since then, the incidence of this complication after then, the incidence of this complication after epidural is usually considered low.epidural is usually considered low.

A retrospective study of 2182 consecutive A retrospective study of 2182 consecutive lumbar epidurals showed an incidence of 0.82%lumbar epidurals showed an incidence of 0.82%

Most of the reported cases of accidental Most of the reported cases of accidental subdural blockade have been in obstetric subdural blockade have been in obstetric patients receiving neuraxial analgesia for labourpatients receiving neuraxial analgesia for labour

According to their findings, up to 7% of According to their findings, up to 7% of epidural needles may be partly placed in epidural needles may be partly placed in the subdural space during the the subdural space during the performance of an epidural block.Thus the performance of an epidural block.Thus the actual incidence may be much higher than actual incidence may be much higher than reported in studies using only clinical reported in studies using only clinical criteria for diagnosiscriteria for diagnosis. .

PREDISPOSING FACTORSPREDISPOSING FACTORS

Difficult block placementDifficult block placement Rough handling and rotation of an epidural Rough handling and rotation of an epidural

needle in the epidural space (dural needle in the epidural space (dural laceration)laceration)

Subdural placement may occur however, Subdural placement may occur however, independently of the level of experience of independently of the level of experience of the operatorthe operator

Patients having previous back surgery were Patients having previous back surgery were . potentially more prone to accidental . potentially more prone to accidental subdural injection, because of altered subdural injection, because of altered anatomy secondary to scarring and anatomy secondary to scarring and retraction and possible obliteration of the retraction and possible obliteration of the epidural space epidural space

A recent lumbar puncture : CSF may A recent lumbar puncture : CSF may leak through the dural rent and leak through the dural rent and distend the subdural space. Any distend the subdural space. Any attempt to inject local anaesthetics at attempt to inject local anaesthetics at the same intervertebral space may the same intervertebral space may cause deposition in the subdural cause deposition in the subdural spacespace

Use of multi hole epidural catheters.Use of multi hole epidural catheters. Long-bevelled needles used during Long-bevelled needles used during

subarachnoid block.subarachnoid block.

PRESENTING FEATURESPRESENTING FEATURES

A subdural block can have a variable A subdural block can have a variable presentation depending upon the extent of presentation depending upon the extent of the spread of local anaesthetic, which in the spread of local anaesthetic, which in turn is dictated by the highly variable turn is dictated by the highly variable anatomy of the space itself.anatomy of the space itself.

The onset of the block is somewhat The onset of the block is somewhat intermediate between that of a intermediate between that of a subarachnoid and epidural block, because subarachnoid and epidural block, because the nerves in the subdural space are the nerves in the subdural space are covered with pia and arachnoid maters, as covered with pia and arachnoid maters, as compared to the subarachnoid space compared to the subarachnoid space where the nerves are sheathed by pia where the nerves are sheathed by pia mater only and the epidural space where mater only and the epidural space where arachnoid, pia and dura mater envelop the arachnoid, pia and dura mater envelop the nerves.nerves.

The block is thus often characterised by a The block is thus often characterised by a slow onsetslow onset (approximately 15 to 20 (approximately 15 to 20 minutes after drug injection) and usually minutes after drug injection) and usually lasts for up to two hours, followed by a full lasts for up to two hours, followed by a full recoveryrecovery

The The sensory blocksensory block produced by subdural produced by subdural injection is usually injection is usually high and high and disproportionatedisproportionate to the volume of drug to the volume of drug injected, as the limited capacity of the injected, as the limited capacity of the space results inextensive spread moderatespace results inextensive spread moderate

There is usually sparing of, or minimal There is usually sparing of, or minimal effect on sympathetic and motor effect on sympathetic and motor functions, due to the relative sparing functions, due to the relative sparing of the ventral nerve rootsof the ventral nerve roots

Thus, hypotension is likely to be only Thus, hypotension is likely to be only moderate.moderate.

Development of Development of motor weaknessmotor weakness is is slow slow and and less profoundless profound, with , with progressive respiratory inco-ordination progressive respiratory inco-ordination rather than sudden apnoea.rather than sudden apnoea.

This presentation helps to This presentation helps to distinguishdistinguish an unexpectedly high sensory level an unexpectedly high sensory level due to subdural placement from that due to subdural placement from that caused by an inadvertent caused by an inadvertent subarachnoid placement during subarachnoid placement during epidural anaesthesia, wherein the epidural anaesthesia, wherein the onset is fast with complete, bilateral onset is fast with complete, bilateral sympathetic, sensory and motor sympathetic, sensory and motor blockade below a certain level blockade below a certain level

unusual presentations of unusual presentations of subdural blockadesubdural blockade

Significant motor weakness in Significant motor weakness in the intercostal muscles and the intercostal muscles and upper extremities upper extremities

A faster than usual onset of blockA faster than usual onset of block A delayed onset of up to 30 A delayed onset of up to 30

minutes with unduly prolonged minutes with unduly prolonged blockadeblockade

Subdural blockade leading to Subdural blockade leading to significant hypotension has also been significant hypotension has also been observed These differences could be observed These differences could be explained by the amount of drug explained by the amount of drug actually injected into the subdural actually injected into the subdural space and interpatient variation in the space and interpatient variation in the anatomy and distensibility of the anatomy and distensibility of the space. space.

Unilateral blocks are common with Unilateral blocks are common with subdural injectionsubdural injection

Permanent neural damage : can occur Permanent neural damage : can occur as a result of unintentional subdural as a result of unintentional subdural injection due to the compression of injection due to the compression of nerve roots or the radicular arteries nerve roots or the radicular arteries traversing the space, causing traversing the space, causing ischaemia of neural tissues. ischaemia of neural tissues.

Unconsciousness and apnoea : Unconsciousness and apnoea : Because the subdural space extends Because the subdural space extends intracranially, local anaesthetic block intracranially, local anaesthetic block of the brainstem is also possible of the brainstem is also possible

Horner’s syndrome and trigeminal nerve Horner’s syndrome and trigeminal nerve palsy : A trigeminal nerve palsy is a more palsy : A trigeminal nerve palsy is a more serious consequence than Horner’s serious consequence than Horner’s syndrome, because this could signify syndrome, because this could signify cephalad spread of the anaesthetic agent cephalad spread of the anaesthetic agent into the cranial cavity. into the cranial cavity.

MECHANISMSMECHANISMS

The various mechanisms by which an The various mechanisms by which an accidental subdural block can occur accidental subdural block can occur while performing central neuraxial while performing central neuraxial blockade include the following: blockade include the following:

subdural placement of intended subdural placement of intended epidural catheters ,well knownepidural catheters ,well known

An epidural or spinal needle may An epidural or spinal needle may pierce the dura as well as the pierce the dura as well as the arachnoid, such that it lies partly in arachnoid, such that it lies partly in both the subarachnoid and the both the subarachnoid and the subdural spacessubdural spaces

In this scenario, drug injection distributes In this scenario, drug injection distributes preferentially to the subdural rather than preferentially to the subdural rather than the subarachnoid space despite the ability the subarachnoid space despite the ability to aspirate CSF. this may be due to the to aspirate CSF. this may be due to the CSF leaking into and distending the CSF leaking into and distending the subdural space.subdural space.

Following initial successful epidural Following initial successful epidural analgesia, subsequent subdural migration analgesia, subsequent subdural migration has been reported.has been reported.

The catheter position relative to the The catheter position relative to the dura and the pressures used during dura and the pressures used during injection of the drug may affect the injection of the drug may affect the orifice from which the drug is ejected.orifice from which the drug is ejected.

Thus, a particular dose of local Thus, a particular dose of local anaesthetic may produce a composite anaesthetic may produce a composite subarachnoid, subdural and/or subarachnoid, subdural and/or extradural blockade, depending upon extradural blockade, depending upon the pressure used to inject the drug.the pressure used to inject the drug.

DIAGNOSISDIAGNOSIS

Accidental injection into the subdural Accidental injection into the subdural space should be suspected if a less space should be suspected if a less than distinct loss of resistance is felt than distinct loss of resistance is felt on inserting the needle into the on inserting the needle into the epidural space or if the patient epidural space or if the patient complains of a frontal headache (due complains of a frontal headache (due to the intracranial displacement of to the intracranial displacement of CSF at the time of drug injection). CSF at the time of drug injection).

Lubenow et al described two major Lubenow et al described two major and three minor clinical criteria for and three minor clinical criteria for the diagnosis of a subdural block.the diagnosis of a subdural block.

Major criteria included:Major criteria included:

A) negative aspiration test A) negative aspiration test

B) unexpected extensive sensory block. B) unexpected extensive sensory block. Minor criteria included :Minor criteria included :

A) a delayed onset by 10 minutes or more A) a delayed onset by 10 minutes or more of a sensory or motor nerve blockof a sensory or motor nerve block

B) a variable motor block and B) a variable motor block and

C) sympatholysis out of proportion to the C) sympatholysis out of proportion to the administered administered

four-step diagnostic four-step diagnostic algorithm to detect algorithm to detect

subdural blocksubdural block FIRST STEPFIRST STEP : determine whether the block is : determine whether the block is

presumed to be the epidural or presumed to be the epidural or subarachnoid space based on the tactile subarachnoid space based on the tactile feel during the insertion and the presence or feel during the insertion and the presence or absence of CSFabsence of CSF

SECOND STEPSECOND STEP : dermatomal spread is : dermatomal spread is assessed as excessive, restricted or neither assessed as excessive, restricted or neither

THIRD STEPTHIRD STEP : minor criteria such as onset : minor criteria such as onset >20 minutes, cardiovascular stability, motor >20 minutes, cardiovascular stability, motor sparing, patchy or asymmetrical spread, sparing, patchy or asymmetrical spread, respiratory failure and cranial involvement respiratory failure and cranial involvement are appliedare applied

•FOURTH STEPFOURTH STEP : : Radiological Confirmation Radiological Confirmation using X-ray computed using X-ray computed tomography scan or tomography scan or magnetic resonance imagingmagnetic resonance imagingAs the subdural space is a As the subdural space is a potential space and normally potential space and normally not visible on scans, the not visible on scans, the presence of deliberately presence of deliberately injected contrast media or injected contrast media or fluid in the space is required fluid in the space is required to confirm the subdural to confirm the subdural placementplacementThe subdural injection of The subdural injection of contrast media is seen as a contrast media is seen as a dense collection confined to dense collection confined to the posterior aspect of the the posterior aspect of the spinal canal, spreading spinal canal, spreading mainly in a cephalad mainly in a cephalad direction. A small amount of direction. A small amount of contrast may extend contrast may extend laterally, delineating the laterally, delineating the nerve rootsnerve roots

AP post-contrast image suggesting subdural injection with contra-lateral (black arrows) and lateral (white arrows) spread of contrast within the dural sleeve

The spread is not affected by a change in The spread is not affected by a change in posture and can be unilateral.posture and can be unilateral.

On an anteroposterior view of the lumbar On an anteroposterior view of the lumbar spine X-ray, the appearance of subdural spine X-ray, the appearance of subdural contrast medium is similar to contrast medium is similar to subarachnoid contrast media. However, subarachnoid contrast media. However, on lateral view and computed on lateral view and computed tomography scan the difference is tomography scan the difference is appreciable. Contrast in the subarachnoid appreciable. Contrast in the subarachnoid space rapidly descends in the CSF with space rapidly descends in the CSF with gravity and outlines the exiting nerve gravity and outlines the exiting nerve roots.roots.

The CSF dilutes contrast The CSF dilutes contrast and it appears less opaque and it appears less opaque than subdural contrast. than subdural contrast. With epidural injection of With epidural injection of contrast media, a wide contrast media, a wide distribution is seen which distribution is seen which tends to flow outward tends to flow outward through the intervertebral through the intervertebral foraminaforamina..

CT sagittal reconstruction demonstrating a left subduralspread (white arrow)

CT and MRI are not always possible.CT and MRI are not always possible. Electrical stimulation of the epidural Electrical stimulation of the epidural

catheter has been used to diagnose catheter has been used to diagnose subdural placement.subdural placement.

The fluid injected into the subdural The fluid injected into the subdural space can spread a considerable space can spread a considerable distance, thus a diffuse motor distance, thus a diffuse motor response involving multiple segments response involving multiple segments can potentially be elicited at a low can potentially be elicited at a low current (<1 mA). current (<1 mA).

MANAGEMENTMANAGEMENT There are no clear guidelines for the There are no clear guidelines for the

management of a potential subdural management of a potential subdural catheter.catheter.

A patient with an accidental subdural block A patient with an accidental subdural block should be monitored closely and managed should be monitored closely and managed according to the signs and symptoms. If a according to the signs and symptoms. If a high sensory level develops, in conjunction high sensory level develops, in conjunction with cardiovascular and respiratory support, with cardiovascular and respiratory support, patients should be considered for intubation patients should be considered for intubation and mechanical ventilation and pressor and mechanical ventilation and pressor support.support.

The epidural catheter should be removed The epidural catheter should be removed and if mandatory, be relocated to another and if mandatory, be relocated to another space.space.

If a subarachnoid block is planned, If a subarachnoid block is planned, enhanced cephalad spread of local enhanced cephalad spread of local anaesthetic should be anticipated, anaesthetic should be anticipated, because of the potential compression because of the potential compression of the subarachnoid space by the of the subarachnoid space by the subdural injectionsubdural injection

If general anaesthesia is If general anaesthesia is administered, succinylcholine should administered, succinylcholine should be used with caution as it may induce be used with caution as it may induce severe bradycardia in the presence of severe bradycardia in the presence of a high sympathetic blocka high sympathetic block

Also, the presence of a catheter in the Also, the presence of a catheter in the subdural space may cause arachnoid subdural space may cause arachnoid rupture, particularly on injection of a rupture, particularly on injection of a large dose, leading to the risk of a large dose, leading to the risk of a post-dural puncture headache and post-dural puncture headache and leakage of local anaesthetic leakage of local anaesthetic producing a subarachnoid blockproducing a subarachnoid block

PREVENTIONPREVENTION

Unrecognised subdural placement of Unrecognised subdural placement of epidural needle or catheter may epidural needle or catheter may account for many complications. A account for many complications. A number of precautions can be taken number of precautions can be taken in order to avoid or detect subdural in order to avoid or detect subdural placement: placement:

Care should be taken when rotating a Care should be taken when rotating a Tuohy needle once it has entered the Tuohy needle once it has entered the epidural space. epidural space.

There should be a high index of There should be a high index of suspicion of subdural placement in suspicion of subdural placement in patients with difficult block or patients with difficult block or previous back surgery. previous back surgery.

Once the dura mater has been Once the dura mater has been punctured, it may be advisable to punctured, it may be advisable to choose another interspace if a repeat choose another interspace if a repeat neuraxial block is required on the same neuraxial block is required on the same occasion. occasion.

During continuous epidural catheter During continuous epidural catheter techniques, every top-up should be techniques, every top-up should be given in a fractionated manner, as per given in a fractionated manner, as per usual safe practiceusual safe practice..

Single orifice catheters may be Single orifice catheters may be preferable to multiple orifice catheterspreferable to multiple orifice catheters

CONCLUSIONCONCLUSION All anaesthetists should be aware of the All anaesthetists should be aware of the

possibility of subdural block during central possibility of subdural block during central neuraxial anaesthesia.neuraxial anaesthesia.

The differential diagnosis of a possible The differential diagnosis of a possible subdural injection should be considered in subdural injection should be considered in cases of extensive sensory blockade cases of extensive sensory blockade despite apparently small volumes of despite apparently small volumes of epidurally administered local anaesthetics, epidurally administered local anaesthetics, unexpected failure of block or atypical unexpected failure of block or atypical presentations following otherwise presentations following otherwise uncomplicated regional block.uncomplicated regional block.

Once subdural injection is suspected, Once subdural injection is suspected, it is advisable to avoid further local it is advisable to avoid further local anaesthetic injections through the anaesthetic injections through the catheter and the patient should be catheter and the patient should be monitored carefully for any adverse monitored carefully for any adverse effects effects

REFERENCESREFERENCES

Review article ,anaethesia n Review article ,anaethesia n intensive care, vol 6,2010.intensive care, vol 6,2010.

Miller’s anaesthesiologyMiller’s anaesthesiology

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