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Original Article

201 Combined spinal-epidurals for anaesthesia using a separate needle technique*

Cook, T. M.

Author Information
European Journal of Anaesthesiology: September 2004 - Volume 21 - Issue 9 - p 679-683

Abstract

Use of combined spinal-epidural (CSE) techniques has become more widespread in the last decade [1]. There are varying techniques. The needle-through-needle (NTN) technique involves placement of a needle in the epidural space, through which a spinal needle is then placed into the subarachnoid space. The epidural catheter is necessarily placed after subarachnoid drug injection. In the separate needle technique (SN) the spinal and epidural components of the block are placed as individual injections. This allows epidural catheter placement either before, or after, subarachnoid drug administration [2,3]. NTN CSE is most widely practised (Blanshard H, Morris J, Cook TM, unpublished UK survey data 2001). Audit data on NTN CSE is available [4]. This paper reports one operator's consecutive series of 201 patients undergoing SN CSE anaesthesia using a novel technique designed to avoid potential problems associated with the NTN technique.

Methods

Data was recorded prospectively from 201 consecutive patients who were receiving CSE as part of their anaesthetic technique (Table 1) between 1998 and 2002. Ethical approval was sought from the local research Ethics Committee to publish this data and was granted. Anaesthetic management was not altered in any way as a result of data collection and therefore anaesthesia was not standardized. Patient data, technical aspects of the procedure, complications and failure rates were recorded.

Table 1
Table 1:
Patient and operation characteristics.

SN CSE was performed awake or with conscious sedation (i.e. verbal contact retained throughout). Sedation was achieved using a target-controlled infusion of propofol with a target of 0.8-1.3 μg mL−1 depending on age and condition of the patient. All blocks were performed with the patient in the sitting position (supported by an assistant), unless the patient was unable to sit up (two patients with painful hips).

CSE technique was as previously described [3]. Firstly a 25-G Whitacre needle was placed in the subarachnoid space and after observing free flow of cerebrospinal fluid (CSF) the stylet was replaced. Secondly a 16-G Tuohy needle was used to identify the epidural space and a catheter was inserted. Finally the stylet was removed from the spinal needle and, after confirming free flow of CSF, subarachnoid drug was injected. The epidural was then managed as required. For young patients, with good flexibility, both spinal and epidural were placed in the midline, usually at the same vertebral level. For elderly patients a paramedian approach to the epidural space was used. Plain bupivacaine or lidocaine was used for all spinal blocks. Technical problems during performance of the CSE were recorded.

Sedation was stopped after block insertion to allow assessment of block level. Blockade level was tested at 5 min with ethyl chloride. If block level was too low for surgery an epidural bolus of 10 mL normal saline (within the first 10 min after block insertion) or 5-10 mL local anaesthetic (beyond 10 min after block insertion) was used to elevate the block level.

Anaesthetic management did not follow a formal protocol. However fluid management followed the author's routine practice. Patients were not preloaded with fluid. All patients received 1 L of crystalloid and 0.5 L of colloid during the first hour after block insertion. Further fluid management varied according to operation and clinical need. If blood pressure fell more than 20% below preoperative levels or below 100 mmHg and the heart rate was below 60 bpm, glycopyronium 0.2 mg was administered. Methoxamine 0.5 mg was used if the blood pressure remained low or if otherwise clinically indicated.

The first dose of epidural local anaesthetic was routinely administered in theatre after aspiration of the epidural catheter. Block level was re-checked on admission to the recovery unit.

Failure of spinal blockade was recorded if no block developed or the block was so low as to suggest partial drug loss from the subarachnoid space. Failure of epidural blockade was recorded if the neurological blockade regressed 4-6 h after spinal administration, despite epidural drug administration and analgesia or if demonstrable blockade could not be established with further epidural drug administration. If an effective epidural subsequently stopped working this was not considered a failure of the CSE technique.

All patients who received postoperative epidural analgesia were visited by the acute pain team at least once each day. All patients were followed up by the author until mobile and, as well as seeking other complications, were specifically asked about headache and backache.

Results

Data was collected on 201 patients (male 94, female 107; median age 70 years (range: 15-97) and mean weight 72 kg (range: 32-165)). Patient and operation details are listed in Table 1. All blocks were performed awake or with sedation. Six patients received general anaesthesia after completion of SN CSE. None of these was because of block failure. Sedation with propofol infusion was administered to 148 patients and 47 received no sedation.

CSE was technically successful in 200 (99.5%). In one case the spinal needle could not be sited. After several attempts the spinal block was abandoned and the epidural placed. An attempt was made at passing a long needle through the Tuohy needle but again CSF could not be aspirated. In all other 200 patients CSE was technically successful. In 179 cases plain bupivacaine 0.5% was used and in 21 cases isobaric lidocaine 2% was used. Lidocaine was used for four day cases, five overnight stay cases and 12 high risk cases in which a 'sequential CSE' technique was used.

Of 200 spinals, 194 were midline and six paramedian. Of 201 epidurals, 132 were midline and 69 paramedian. All spinal injections (and all epidural injections except one at T12/L1) were performed at L2/3 to L4/5. CSEs were performed with both injections at one interspace in 163 cases. Of the same interspace insertions 103 were midline for both spinal and epidural, 54 were midline for spinal and paramedian epidural, and six were paramedian for both. Thirty-eight CSEs were performed with injections at separate interspaces. The epidural was always placed above the spinal needle in these cases.

All spinal blocks produced neurological block. One (0.5%) was unexpectedly low. The epidural catheter was used in 179 cases and was not used in 22. One epidural failed completely (no block could be demonstrated after boluses) and in one case it was equivocal (after spinal block regression, analgesia improved with epidural boluses but no block could be demonstrated). This represents a 0.6-1.1% failure rate. After insertion of the epidural catheter and removal of the spinal needle stylet CSF flowed without delay in all cases, except one (0.5%). In this case minor adjustment resulted in CSF flow.

Minor problems occurred during the procedure in 31 cases (15.4%). These were paraesthesiae (n = 13 with epidural catheter, n = 2 with spinal needle), inability to feed the epidural catheter (n = 4), or blood in the epidural catheter (n = 12). In 14 (7%) of cases the epidural catheter was immediately re-sited to overcome the problem. Inadvertent subarachnoid catheter placement, subarachnoid catheter migration, epidural catheter migration into vein or subarachnoid space, unexpected high block, unexpected motor block, temporary and permanent neurological sequelae were all sought but none occurred. There was no significant morbidity in any patient that might be attributed to the regional technique. In the last 97 cases, the use of vasoconstrictors was recorded and they were used in three cases (maximum 3 mg methoxamine).

One hundred and ninety-seven patients were followed up until mobile (including the four day-case patients). On the day they mobilized all patients were specifically asked if they had headache or backache. In two cases reliable data on complications was impossible to obtain due to dementia, but no complications were evident. Two patients were lost to follow up. One typical post-dural puncture headache occurred in a patient following elective Caesarean section. One other patient reported a headache, which was nonspecific in nature. Backache was reported on direct questioning by four patients (2%). This was mild and localized in all cases.

Discussion

The study shows the reliability of this SN CSE technique in one experienced individual's hands. The study is, however, limited in several respects. Firstly the dataset was collected as part of audit. It was therefore inappropriate to standardize anaesthetic technique. Lack of formal standardization makes comparison with other techniques difficult, but as all procedures were performed by one individual the technique was consistent throughout the study. Secondly as all procedures were performed by one person experienced in this technique, comparison with other reports of different techniques may be unreliable. Thirdly this series is unusual in the literature as it contains few obstetric cases. However CSE is widely used for non-obstetric cases in the UK (Blanshard H, Morris J, Cook TM, unpublished UK survey data 2001) and in Europe [5] and the results are therefore relevant.

Two points should be made about the SN CSE technique described. Firstly there is potential for movement or displacement of the spinal needle during placement of the epidural needle. However after epidural placement, when the spinal needle stylet was removed, CSF was seen to flow from the spinal needle in all but one case. In this case minor needle adjustment produced CSF flow. This observation and the low failure rate for spinal anaesthesia suggest that spinal needle movement, or displacement, are not major problems of this technique.

Secondly the technique might be considered 'crowded' if two needles are used at a single interspace. The reason to consider this technique is that it limits the sites of local anaesthetic infiltration to one space, which might be more acceptable to some patients [6]. Minor adjustments can minimize difficulties. If using the midline approach for spinal and epidural components the spinal needle is placed as caudad as possible in the interspace before inserting the epidural needle more cephalad. Alternatively the anaesthetist may use two interspaces or use a midline approach for the spinal needle and a paramedian approach for the epidural.

Accepting the limitations of this descriptive study, what can be learnt from this case series? Firstly although NTN CSE is used for approximately 80% of CSEs in the UK (Blanshard H, Morris J, Cook TM, unpublished UK survey data 2001) this study suggests that this SN CSE technique is superior, because it is less prone to failure and to minor technical complications with important potential sequelae [3]. The results of this report add some support to that contention but comparative studies between the two techniques are needed to confirm or refute this.

Regarding success, this series shows that the separate needle CSE technique can achieve a low failure rate (0% for spinal and 1% for epidural). In papers reporting NTN CSE, failure of the spinal component is generally reported between 10% and 20% [4,6,7]. In experienced hands failure as low as 1-5% may be achieved [8,9] and the largest series available reports a 4.9% failure rate (Plaat F, Collis RE, personal communication). The equivalent literature on the failure rate for the epidural component of CSE suggests a failure rate of approximately 1.2% [10]. A group from Finland in a study of three groups of 30 patients recently reported a 100% success rate with a SN technique (epidural before spinal), 90% with parallel needles and 63% with NTN technique [11].

In 29 (14.4%) cases problems were noted while advancing the epidural catheter (paraesthesia, bleeding into the catheter or inability to advance the catheter). In 14 (7%) of these cases the problem necessitated re-siting the epidural. Importantly as no subarachnoid injection had occurred at this time, there were no sequelae. In contrast, if a technique were used with subarachnoid injection before epidural catheter placement (which is inevitable with NTN CSE), the delay while re-siting the epidural has the potential to lead to problems of inadequate or malpostioned block or of cardiovascular instability. Each of these complications has been reported [12-15] but the frequency of the problem has not been examined. The avoidance of these complications might be seen as a potential advantage of the SN technique.

When paraesthesia occurs during placement of a spinal needle, long-term neurological sequelae are more common than in the absence of paraesthesia [16], although the association is weak. A large series of subarachnoid anaesthesia reports paraesthesia in up to 6% [16]. In this series paraesthesia during spinal needle placement occurred in two (1%) patients. The incidence of paraesthesia during CSE may be higher: during NTN CSE the incidence in one study was between 16% and 29% [1]. A survey of UK Obstetric Anaesthetic Departments suggested that the incidence of paraesthesia and nerve injuries following CSE (technique not specified) and subarachnoid block was not different, but the nature of the study makes the conclusions far from robust [17]. The lowest reported incidence of paraesthesia during spinal needle insertion with a NTN technique is 2.6% [18]. During SN CSE technique with epidural insertion followed by spinal needle placement, in a small series the incidence of paraesthesia during spinal needle insertion was 26% [2].

Paraesthesia while advancing the epidural catheter occurred in 13 patients (6.5%) in this study. Other reports range from 11% to 30% of cases and clinical sequelae are rare [19,20]. In theory not all paraesthesia due to catheter insertion will be detected when the catheter is sited after the initiation of subarachnoid block (e.g. in all NTN CSE) however this has not been demonstrated [19].

The incidence of major complications in this study was zero but this must be interpreted cautiously. It has been suggested that CSE, and in particular NTN CSE with pencil point needles, may be associated with an increase in neurological injuries [17,21,22]. Major complications of regional blockade are rare, but devastating. In this small series safety cannot be inferred from the absence of serious complication, but the results are reassuring, as there were neither major neurological complications nor near misses.

This series has shown the clinical utility of a separate needle CSE technique with spinal needle inserted before the epidural needle and subarachnoid drug administered after epidural catheter placement. In particular the technique described was effective and safe. The high success rate of both spinal and epidural components and the lack of complications, relative to other published series, suggest this technique might be studied further.

References

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Keywords:

Technique; regional anaesthesia; combined spinal epidural

© 2004 European Academy of Anaesthesiology