combined spinal-epidural anaesthesia techniques.......... a ... - medIND

450 Indian J. Anaesth. 2005; 49 (6) : 450 - 458 

INDIAN JOURNAL OF ANAESTHESIA, DECEMBER 2005 450 

REVIEW ARTICLE 

SUMMARY 

COMBINED SPINAL-EPIDURAL ANAESTHESIA 

TECHNIQUES.......... A REVIEW 

Dr. Chandola H.C. 1 Dr. Zubair Umer Mohamed 2 Dr. Asok Jayaraj Pullani 3 

Combined Spinal Epidural (CSE) anaesthesia commands a unique place among the various techniques used for neuraxial blockade. In 

this article we delve into the history of CSE and try to enumerate the types of specialised needles devised for this technique. The 

spinal needles that are, and in the future may well be associated with this technique are also discussed. The methods used to locate 

the epidural space have been researched exhaustively and an attempt has been made to classify the various options available for CSE. 

Controversial aspects such as the preferred approach, catheter threading prior to or after subarachnoid block and the need for test dosing 

have also been addressed. 

Keywords : Combined Spinal Epidural, CSE, Tuohy Needle, Spinal needle, Catheter. 

Introduction 

Among the various techniques used for neuraxial 

blockade, CSE commands a unique place. The singularity 

lies in its ability to combine the rapidity, density, and 

reliability of the subarachnoid block with the flexibility of 

continuous epidural block to titrate a desired sensory level, 

vary the intensity of the block, control the duration of 

anaesthesia, and deliver postoperative analgesia. Of late, 

this procedure has come back in a big way, the fact justified 

by its use extended to paediatric and even infant 

laparotomies, apart from its use in orthopedic surgery, 

obstetrics, very old patients and in other high-risk patients. 1 

Although at first sight the CSE technique appears to be 

more complicated than either epidural or spinal block, 

intrathecal drug administration and placement of the epidural 

catheter are both facilitated by the various modifications of 

the combined spinal-epidural technique. 1,2 In this article 

we try to follow the evolution and also summarise the 

various developments in this technique described by various 

authors over the years. 

History 

Leafing through the archives of anaesthesia, we find 

that CSE was first described in 1937 by Soresi 3 , who used 

the “episubdural” technique by first injecting a dose of 

local anesthetic epidurally and, after advancing the needle 

inside the dural cavity, injecting the spinal dose. Curelaru 4 

1. M.D., Asso. Prof. 

2. M.B.B.S., PG Student 

3. M.B.B.S. PG Student 

M.L.N. Medical College, Allahabad, UP. 

Department of Anaesthesiology, 

M.L.N. Medical College, Allahabad, Uttar Pradesh - 211001. 

Correspond to : 

Dr. H. C. Chandola 

E-mail : chandola@sancharnet.in 

(Accepted for publication on 30 - 08 - 2005) 

performed the first combined spinal anesthesia and 

catheter-based epidural anaesthesia in 1979. He introduced 

an epidural catheter through a Tuohy needle, administered 

a test dose, and then performed a traditional dural puncture 

1–2 lumbar segments distally using a 26-gauge spinal 

needle. CSE was performed in 1982 on a single spinal 

segment for lower limb surgery by Coates 5 and Mumtaz 6 

et al. Epidural anaesthesia was performed using a 16-gauge 

Tuohy needle, after which a 25-to 26-gauge spinal 

needle, approximately 1 cm longer than the epidural 

needle, was introduced with the Tuohy needle as introducer. 

After the injection of local anesthetic, the spinal needle 

was withdrawn and the epidural catheter inserted. In 

1986, Rawal described a single segment sequential CSE 

for caesarean delivery. (see below “Sequential CSE”). 

Over the years, a variety of spinal, epidural and specialised 

combined spinal-epidural needles have been devised and a 

myriad of techniques described to refine this procedure. 

Classification 

The various options in CSE can be classified broadly 

according to the number of interspaces used for performing 

the procedure (table 1). If both the epidural and the spinal 

punctures are performed in the same interspace it is called 

single segment technique (SST) or single interspace CSE 

technique and the others are named double segment techniques 

(DST) or double interspace CSE technique. These can be 

further classified according to the type of needle used and 

the approach. 

Single and double segment techniques 

The reduced number of skin punctures in SST 

decreases the incidence of patient discomfort, trauma, pain, 

infection at puncture sites, epidural venous puncture and 

formation of hematomas. 1 The use of an epidural needle as 

an introducer for the spinal needle lessens the likelihood of 

contamination of the spinal needle with skin-borne

CHANDOLA, MOHAMED, PULLANI : COMBINED SPINAL-EPIDURAL ANAESTHESIA 451 

microorganisms 7 . However, no quantitative studies have been 

performed to confirm these assumptions. In DST, there is 

always a theoretical possibility of damaging the epidural 

catheter with the spinal needle if the catheter is threaded 

before subarachnoid block. The advantage of DST is that it 

does not require specialised CSE needles that are more 

expensive than the usual epidural and spinal needles. 

Table - 1 : Classification of CSE Techniques 

Single Segment 

Needle-Through-Needle 

Without Spinal Needle Support 

Median Approach 

Paramedian Approach 

With Spinal Needle Support 

Spinal Needle Sleeve 



Spinal Needle Lock 



Needle-Beside-Needle (Double Barrel/Lumen) 

Without Attached Spinal Needle Guide/Separate Needle 


aramedian Approach 

Combined Median/Paramedian Approach 

With Attached Spinal Needle Guide 

Guide alongside Epidural Needle 



Guide incorporated within Epidural Needle 



Double Segment 



Each of these can be performed with or with out epidural and/or spinal 

catheters 

Fig. 1: Different types of needles used for CSE technique. 

A : needle through needle, B: Huber and Hanaoka needle, 

C: Eldor needle, D: Eldor, Coombs and Torrieri needle. 

Needles 

Single Lumen Epidural Needles (Needle-Through- 

Needle technique) 

1. Epidural Needle with Single Aperture: This most 

commonly used set consists of a conventional 16-18 

gauge epidural needle (Fig. 1A) to locate the epidural 

space. A spinal needle is then introduced through the 

epidural needle to exit it through the Huber eye and 

proceed to puncture the dural wall and enter the 

subarachnoid space. 

2. CSE Needle with Additional Aperture (Huber and 

Hanaoka Needles): This is basically an epidural needle 

with an additional aperture (‘back eye’) situated at 

the end of the longitudinal axis. 8,9 (Fig. 1B) 

The usual technique is used for identification of 

the epidural space. The spinal needle is then introduced 

through the proximal port of the epidural needle to exit 

at the ‘back eye’ and after dural puncture and drug 

administration the spinal needle is withdrawn and the 

catheter inserted. The larger diameter of the catheter 

causes it to pass through the usual Huber opening. These 

modified needles function as a suitable introducer for even 

the thinnest spinal needle, as kinking and friction in the 

Huber eye of the epidural needle is avoided. Advancing the 

spinal needle through the “back eye” may offer a more 

distinct sensation of dural puncture. 10 To accomplish 

proper passage through the “back eye,” however, the distal 

end of the spinal needle must face the same way as the 

Huber opening of the epidural needle; otherwise the spinal 

needle may pass through the Huber eye. 11 But a traditional 

insertion of the epidural needle with the Huber eye facing 

cephalad will then cause the cutting bevel of the spinal 

needle to cut the dural fibers perpendicular to its alignment, 

which may increase the risk of postdural puncture 

headache. 12 With the needle through needle technique, there 

is a concern about the tip of the spinal needle scraping the 

inner wall of the epidural needle and thereby leading to 

deposition of metal particles in the epidural and/or 

subarachnoid spaces and possible, subsequent neurological 

sequelae. 13 However, studies by Herman et al 14 failed to 

find any evidence of additional metal particles produced by 

the needle-through-needle technique and puts these doubts 

to rest. The risk of damage to the bevel of the spinal needle 

has been circumvented by the introduction of a plastic sleeve 

for the spinal needle by the Espocan® system. 1 The plastic 

sleeve keeps the spinal needle centrally in the epidural 

needle and guides it through the back eye. 

In this technique, the spinal needle is in contact 

with only dura and the epidural needle, which may increase 

the risk of displacement of the spinal needle at the time of

452 

INDIAN JOURNAL OF ANAESTHESIA, DECEMBER 2005 

syringe connection, aspiration of CSF or injection of local 

anaesthetic. 1 A study conducted by Tanaka N and coworkers 

15 and Hoffmann et al 16 clearly demonstrated that 

the lockable CSE provided safe and stable conditions and 

a good success rate of subarachnoid block. But the feel of 

the “dural click” was diminished when lockable CSE was 

used. 

larger distal side port of the Sprotte needle, as well as its 

greater distance from the tip, may account for the slightly 

greater deflection observed with Sprotte needles compared 

to Whitacre needles. (Fig. 2) 

Double-Lumen Needles: (Needle-Beside-Needle 

technique) 

In this technique, an epidural needle and spinal needle 

are introduced through separate lumen or barrels. The spinal 

needle guide may or may not be attached to the epidural 

needle. 

Separate Needle 

In the technique described by Eldor and Olshwang, 

the epidural needle is first placed in the epidural space by 

the usual method followed by the introduction of the spinal 

needle beside the epidural needle to perform the subarachnoid 

puncture. 17 

A recent article by Cook described a variation from 

this sequence by first locating the spinal needle in the 

subarachnoid space and observing the free flow of CSF. 

The stylet of the spinal needle is then replaced. The epidural 

needle is then introduced via the median or paramedian 

approach and catheter threaded, following which the 

intrathecal drug is administered. 18 

Attached Needle 

A parallel tube is attached to the epidural needle, 

which acts as the introducer for the spinal needle. The 

parallel tube may be either bent at the proximal end or 

straight through out. The Eldor Needle (Fig. 1C) has a 

straight tube attached while the Eldor, Coombs and Torrieri 

Needle (Fig. 1D) has a bent spinal needle attached. 7,9,19 

The T-A needle is a further modification where both the 

needles are welded together and the distal ends of the 

needles make a common tip. The epidural needle points 

cephalad and the spinal needle points caudad. 20 The more 

recently introduced E-SP needle has a needle wall 

configuration that is “over-under” rather than parallel. 1 

Spinal Needles 

The gauge and type of the spinal needle influences 

the success of the procedure and the incidence of outcome. 

The use of smaller gauge needles and ones with a conical 

tip reduces the incidence of post dural puncture headache. 21,22 

Lipov 23 et al. demonstrated that the axial force needed to 

deform the Sprotte needle tip was less than that needed for 

the Whitacre and Quincke needles of similar size. The 

Fig. 2 : Tip of different types of spinal needles. 

A: Sprotte, B: Whitacre, C: modified pencil-point, 

D: ball pen, E: double-hole pencil-point, F: Quincke, G: Atraucan. 

Newer needles have been designed to improve 

efficacy. The Atraucan needle has a double bevel with the 

distal cutting bevel making a cutting incision in the dura. 

The second part of this needle dilates this incision rather 

than cutting through the fibres leaving only a small hole in 

the dura. The sharp tip however is prone to damage. 24 A 

new pencil-point spinal needle described is the double-hole 

pencil-point (DHPP) spinal needle, and is composed of a 

blunt ogival tip and two circular holes opposing each other 

just proximal to the tip. The area of the two windows is 

almost the same as of the single holed Sprotte needle’s 

area, which enables more rapid CSF reflux. The anesthetic 

solution injection spreads through both windows. This allows 

a more diffuse anesthetic distribution and less anesthetic 

solution dosage. The DHPP spinal needle allows anesthetic 

solution injection even when a tissue fragment obstructs 

one of the holes. More recently, the ball pen needles have 

been marketed in France. The tip of this needle is actually 

the tip of the stylet leaving a hollow cannula when the 

stylet is removed. The proposed advantages of this needle 

are that the tip of the needle is always completely in the 

subarachnoid space and on removal of the stylet there is no 

needle tip projecting beyond the orifice causing damage to 

the neurological tissue. There is no mechanical weakening 

at the tip caused by the presence of a lateral orifice. The 

open end of the needle allows laminar flow of cerebrospinal 

fluid, which results in faster identification of the subarachnoid 

space. 24 Optimal Length of the Spinal Needle Beyond the 

Epidural Needle Tip 

The distance from the tip of the epidural needle to 

the posterior wall of the dural sac in the midline varies 

considerably among patients (0.3-1.03 cm). 25,26 Further, the


anteroposterior diameter of the dural sac varies considerably 

during flexion and extension of the spinal column. At L3- 

L4, the diameter increases from a range of 9-20 mm in 

extension to a range of 11-25 mm in flexion. 27 Additionally, 

these findings are only valid when the epidural puncture is 

performed in midline. This is because the dural sac is 

triangular with its base resting on the vertebral body and 

the triangle top points posteriorly to ligamentum flavum. 28 

A minimum of 13 mm length of the spinal needle protrusion 

beyond the epidural needle tip is recommended for the CSE 

sets for a reasonably high success rate. 10 Also, because of 

needle design, the length of protrusion for needles with side 

orifice should be greater than that for end orifice needles. 29 

Techniques 

The first neuraxial blockade performed by Corning 

must have been an epidural rather than a spinal block. 30 

The earlier methods to identify the epidural space were the 

feel and hear method of Pages, positive plunger pressure by 

Dogliotti, “hanging drop” method by Gutierrez and the 

balloon deflation technique by Macintosh and Oxford. 31 Most 

of these techniques were based on the concept of “negative” 

pressure in the extradural space. However, the experiments 

of Urayama 32 and Shah JL 33 showed that 77% of the lumbar 

cerebrospinal fluid pulse wave, which is directly transmitted 

to the extradural space as an extradural pressure wave 

originates in the vascular system (arteries and veins), and 

not in the brain. So, any rise in the blood pressure, which 

is not an infrequent observation during epidural needle 

insertion, can give a concomitant rise in the extradural 

pressure with the loss of the “negative” pressure in the 

extradural space and “unreliable” hanging drop and balloon 

indicator techniques. Many feel the loss of resistance to 

saline or demonstration of a free flow of the saline column 

is a superior method for properly identifying the epidural 

space. However, when administering CSE, the use of air 

has been advocated so that there is no confusion that the 

fluid returning is CSF when the spinal needle is subsequently 

placed. These techniques have the disadvantage of identifying 

only the epidural space and not the subarachnoid space. 

Kopacz et al 34 describes a further modification of this 

technique which may increase the success rate and ease 

with which it is performed. The modification described 

allows the continued use of saline for loss of resistance 

using an epidural needle with a transparent hub. First, 

close attention is paid to the location of the saline meniscus 

left within the epidural hub after demonstrating the loss of 

resistance using saline. If a loss of resistance to air technique 

is used, a small amount of saline can be introduced to 

create this meniscus. The spinal needle is advanced in the 

usual fashion until it is felt to exit the epidural needle. As 

the spinal needle is advanced further to contact and indent 

the dura, the tenting of the dura generates a negative pressure 

within the epidural space, causing the meniscus to be drawn 

in. This is similar to what is seen when performing the 

“hanging drop” technique of identifying the epidural space. 

As the spinal needle is advanced further, the dura is punctured 

and the meniscus returns to near its original location as the 

pressure within the epidural space returns to baseline. 

Finally, CSF is observed to flow into the spinal needle to 

ultimately drip from its hub. The point at which the meniscus 

starts to advance is dependent on the dimensions of each 

particular patient’s epidural space and to what distance the 

needle has traversed the epidural space. This phenomenon 

is reported to be a very specific indicator of needle location 

and is most easily seen when a Whitacre spinal needle is 

used. When a Quincke or Sprotte needle is used, the 

movements of the meniscus may occur so suddenly that 

often only a “pop” or “splash” of the fluid is detected, or 

no movement is seen at all. These observations agree with 

the studies showing that more force is required to penetrate 

the dura with a Whitacre needle compared to a Quincke 

needle. 35 The ‘membrane in syringe’ technique is, in principle, 

a modification of the loss of resistance technique for 

identifying the epidural space. 36 A novel method to identify 

the epidural space using an acoustic device was described 

by Jacob S and Tierney E. 37 The traditional loss of resistance 

technique is combined with amplification of the sound made 

by the epidural needle as it traverses the interspinous 

ligament and the ligamentum flavum and then enters the 

epidural space. Lechner TJ and associates 38 described a 

variant of the previous method. This consisted of translating 

the pressure generated during the epidural puncture procedure 

into a corresponding acoustic signal. Both these methods 

combine the loss of resistance techniques with a newer 

approach to improve the success rate by giving an early 

warning of entry into epidural space. In addition, these can 

be excellent teaching aids for beginners. 

A still newer method to locate the epidural space 

using real-time ultrasonic guidance has been described by 

Grau T and colleagues. 39 Epidural space localization has 

also been reported by using an electronic device known as 

Episensor but with limited success. 40 

Sequential CSE Technique 

Rawal first described this variation of the standard 

CSE technique. 1 The spinal block is performed in the sitting 

position and a low dose of hyperbaric bupivacaine is 

administered to achieve a S5 to T8-T9 block. The patient 

is placed supine with a left lateral tilt. When the spinal 

block is “fixed” it is extended to T4 by injecting fractionated 

doses of local anaesthetic into the epidural catheter.

454 


Two Catheter CSE Technique 

A technique of providing CSE anaesthesia using 

both spinal and epidural catheters in the same and 

different interspace was described by Dahl et al 41 and 

Vercauteren et al 42 respectively. The main advantage was 

the possibility of titrating the intrathecal dose of the local 

anaesthetic to the desired dermatomal level and to test the 

correct position of epidural catheter before injecting the 

drugs. Because of the requirement of a large diameter 

spinal needle (22-gauge), the risk of catheter penetration 

may be high; knotting of the catheters is also a theoretical 

risk. 42 

Approach 

Blomberg et al, 43 Gaynor A 44 and Hatfalvi BI 45 

compared the midline and paramedian approaches for lumbar 

epidural block and concluded that the paramedian approach 

was superior due to the following reasons. 

1. Easier to locate the epidural space and reduced 

incidence of technical and catheter-related problems - 

extreme flexion of the back to open up the interlaminar 

space is not required; 

2. Reduced risk of trauma to the epidural veins and 

lower incidence of epidural vein cannulation; 

3. Easier catheter insertion - the needle is angulated 

substantially more cephalad resulting in less “tenting” 

of the dura and a straighter catheter path; 

4. Lower incidence of dural puncture; 

5. Less paresthesia on catheter insertion and fewer 

traumas to the ligaments of the back, with fewer 

complaints of postpartum backache; 

Muranaka K and colleagues 46 concluded that though 

the paramedian approach may be extremely useful for 

patients with a midline scar or for those with a rigid spine, 

it requires a longer spinal needle “compared to the median 

approach. 

Rotation of Epidural Needle 

Rotation of the epidural needle by 180° between 

administration of the subarachnoid injection and threading 

of the epidural catheter had been advocated so that the site 

of the dural puncture is away from the point at which the 

catheter impinges. 47,48,49 This was presumed to decrease the 

chance of subarachnoid placement of the catheter. But, in 

fact, rotation of the epidural needle increased the chance 

of inadvertent dural tear or puncture and subarachnoid 

catheter placement. 10,50 This practice has hence been 

condemned. 1 

Catheter 

Holmström et al 51 states that the distribution of 

fat, rather than any dorso median connective tissue band, 

influences the course of epidural catheter in epidural 

space. Single-holed, open-end (uniport) and multiple 

lateral holed, closed-end (multiport) epidural catheters are 

commonly used; however, the risks and benefits associated 

with each are controversial. Advantages cited in favor of 

the blunt-tipped multiport epidural catheter include a reduced 

likelihood of intravenous (IV) cannulation, since the catheter 

tip is less likely to traumatize an epidural vein during 

insertion, 52 and a reduced incidence of inadequate analgesia, 

since local anesthetic distribution may be enhanced by the 

total separation of the three lateral ports. In contrast, 

multiport epidural catheters have the theoretical disadvantage 

of multicompartment placement when at least one port is 

intrathecal, subdural, or IV, while the other port lies within 

the epidural space. Multicompartment placement increases 

the risk of high spinal blockade or local anesthetic toxicity 

when local anesthetics are rapidly administered. But 

D’Angelo et al 53 found that multiport epidural catheters 

were associated with less inadequate analgesia and required 

manipulation less often than uniport epidural catheters. 

A newer version of epidural catheter is the combined 

end-multiple lateral hole (CEMLH) catheter. It has 7 holes 

within its 1.5 cm head: One at the tip; the first 3 lateral 

holes are arranged circumferentially at 1 mm from each 

other; the other 3 holes have a 4 mm distance from one to 

the other. 

Beilin 54 et al found that women in labor, who had 

multi-orifice epidural catheters threaded 5 cm into the 

epidural space through a cranially directed epidural needle 

orifice at the L2-3 or L3-4 interspace, had the highest 

incidence of successful analgesia with 0.25% bupivacaine, 

as compared to women with catheters threaded 3 or 7 cm 

into the epidural space. The studies of Holmström et al 51 

indicate that the risk of epidural catheter migration through 

the dural hole during uncomplicated combined spinal epidural 

block is very small. 

Among the blind end catheters the softer tip ones 

were least likely to cause transient paresthesias during 

epidural catheter placement but the wire reinforced ones 

were easier to insert and maneuver. 55,56,57,58 Threading of 

the epidural catheter may at times be a tricky affair and 

consume a considerable amount of time. There are two 

schools of thought regarding whether the catheter should be 

threaded before or after the subarachnoid block. If catheter 

insertion is attempted after spinal drug administration, 

1. This may lead to the spinal drug “fixing” before the 

patient is positioned.


2. There is also a theoretical risk of the spinal anaesthetic 

obscuring paresthesia during the epidural catheter 

insertion. 

3. It may be difficult to verify the position of the catheter 

because of difficulty identifying unintentional 

subarachnoid injections in the presence of existing 

spinal anaesthesia. 1 

These problems can be overcome if the double 

segment technique is used and the epidural space location 

and catheter threading is performed prior to subarachnoid 

puncture, by using Cook’s technique or by using the double 

lumen needles. 

However the problems of prior placement of the 

epidural catheter has been enumerated by Rawal. 1 

1. Epidural test dose may make differentiation between 

spinal and epidural block difficult. 

2. A portion of epidural test dose may appear in the hub 

of the spinal needle and cause confusion. 

3. The final direction of epidural catheter is unpredictable. 

And may even tie itself in a knot. 

4. Because, epidural catheter migration can occur over 

time, only a recent test dose holds significance. 

5. The incidence of epidural catheter penetration through 

the dura has been reported to be more common with 

double segment technique than the single segment 

technique. 

Tseng CH et al 59 found that injection of 10 ml saline 

into the epidural space before catheter insertion could 

significantly diminish the incidence of epidural venous 

puncture by the catheter. Another method to ease the insertion 

of the catheter into the epidural space is by asking the 

patient to hold breath in deep inspiration so as to expand the 

epidural space cross-sectional area. 60 Withdrawing the 

catheter 1-2 cm, rotating it along the long axis and 

re-advancing may also help in some cases of difficult 

catheterisation. 57 

Long term indwelling epidural catheters are best 

cleaned with pledgets impregnated with 10% povidoneiodine. 

61 The removal of catheter in the lateral position is 

reported to have a higher success rate than removing in the 

sitting position. 62 Blackshear et al reported that catheters 

of high tensile strength should be used to minimize the 

chance of catheter tip breaking in the epidural space. 63 

Position 

Yun et al 64 found that hypotension was more severe 

and more difficult to treat when CSE for cesarean section 

was induced in the sitting versus the lateral position. 

Test Dose 

The location of the epidural catheter cannot be tested 

by injecting the usual volume of local anesthetic 65 , because 

of the risk of total spinal anesthesia if the catheter is 

placed spinally. The conventional epidural catheter test 

dose consists of either 1 ml of hyperbaric lidocaine with 

adrenaline or 2 ml of 0.5% bupivacaine with adrenaline. 66 

With a correctly inserted epidural catheter, the block height 

will increase only approximately two segments. If the 

catheter has entered the spinal canal, the resulting block 

will not extend to a level causing diaphragmatic paralysis. 

Crawford in his review of 27,000 lumbar epidural blocks 

concluded that “the requirements for safety are that all top 

ups are given in divided dose, with an interval of 

approximately 5 minutes between two increments”. 67 

When CSE is used in labour analgesia, a traditional 

epidural test dose causes unwanted loss of motor and 

proprioceptive functions, defeating the whole purpose of 

ambulatory analgesia or walking epidural in labour. In 

addition, traditional test doses frequently fail to detect 

subdural catheter placement. 68 These concerns have urged 

some workers to advocate that when low-dose mixtures of 

opioid and local anesthetic are used, as in the CSE technique 

or for epidural analgesia alone for labour, epidural test 

doses are unnecessary. 69 

The debate on test dosing the epidural catheter with 

local anaesthetic may well be put to rest if the method 

described by Tsui BC et al 70 and Ozawa T et al 71 becomes 

simpler and more applicable. This method was to electrically 

stimulate the catheter tip and see the neuromuscular response 

and was reported to be more sensitive and specific than the 

standard test dose (3 ml lidocaine 1.5% with 1:200,000 

epinephrine). The main drawbacks of this method being that 

the epidural catheter has already been placed and this method 

only verifies whether the catheter tip is in contact with a 

nerve or not. It cannot differentiate between an epidurally 

and a subdurally placed catheter. 

Dosage in CSE 

CSE often produces a more extensive block than 

expected. The following possible mechanisms have been 

postulated for the reduced epidural drug requirement in 

CSE. 

1. Leakage of epidural local anaesthetic through the dural 

hole into the subarachnoid space. 72 

2. Continuing spread of initial subarachnoid block 

(unrelated to the epidural injection). 1 

3. Existence of “subclinical” analgesia at a higher level 

which is enhanced and becomes evident by perineural 

or transdural spread of epidural local anaesthetic. 73

456 


4. Change in epidural pressure. The pressure becomes 

atmospheric which may result in better spread of 

local anaesthetic because of an effect on volume and 

circulation of CSF. 74 

5. Epidural Volume Extension (EVE): Compression of 

subarachnoid space by the presence of epidural catheter 

and by the volume of local anaesthetic, resulting in a 

“squeezing” of CSF and more extensive spread of 

local anaesthetic. 50,65,75,76,77,78 

The necessary epidural dose for extension of a spinal 

block varies between 1.5 and 3 ml per added segment, less 

than needed for extending a conventional epidural 

anesthesia. 50 

Various aspects of the combined spinal epidural 

anaesthesia, discussed above have been incorporated in many 

of the commercially available kits. Research is on and 

further improvements are expected in the near future. 

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CAUSES OF DIFFICULT INTUBATION 

(PNEUMONICS/ACRONYMS FOR EASY REMEMBRANCE) 

A – Ankylosis of TM joint, Acromegaly, 

Adentulous. 

B – Bull neck, Beard individual, Big breasts, Burns 

contracture. 

C – Collapsible pharynx, Cervical spine injuries, 

Cystic Hygroma, Cleft Lip, Cleft palate. 

D – Down syndrome, Dentures. 

E – Epiglotitis, Excessive pharynzeal tissue. 

F – Fascio-maxillary injuries/abnormalities, F.B. 

G – Goitre, Golden har’s Syndrome. 

H – Hydrocephalus, High arched palate. 

I - Inter Incissor Distance > 3.8 cm., Irradiation 

causing fixity of Larynx. 

J – Junior (Improperly trained) Anaesthesiologist. 

K – Kippel – Feil Syndrome. 

L – Laryngeal oedema, Ludwigs Angina, Large 

Tonsills, Large tongue, Lock jaw, Large 

Incissors. 

M – Micrognathia, macroglossia, Mallampati score 

> 3. 

N – Neck mobility, Neoplasms, No teeth. 

O – Obesity, Odema in Ac. Burns, Over confidence 

of Anaesthesiologist. 

P – Peritonsillar abscess, Pierre Robbinson 

Syndrome, Poor illumination of laryngoscope. 

Q – Quinsy. 

R – Retrognathia, Rheumatoid arthritis of TMJ/ 

Cervical spine, Retropharyngeal abscess. 

S – SAS, Short Neck, Snorer. 

T – Tongue tie, Tracheal stenosis, Trismus, 

Treacher – collin syndrome. 

U – Uvulitis/abscess. 

V – Visualisation of only Epiglotis/only soft palate. 

W – Wrong tube size, wrong laryngoscope blade, 

wrong assistant, wrong position and place, 

Webbed neck. 

X – X-ray evidence of increased in mandibulo – 

hyoid distance. X – ray evidence of decreased 

space between C1 and occiput. 

Y – Younger children – infants, new borns/ 

Neonates. 

Z – Zygomatic bone # and/dislocation. 

Dr.I.Rathnakar 

Karimnagar (AP)

combined spinal-epidural anaesthesia techniques.......... a ... - medIND

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