Description of the condition
This review is an update of a previously published review in the Cochrane Database of Systematic Reviews, 2005, Issue 4 (and updated in the Cochrane Database of Systematic Reviews, 2010, Issue 1), on local anaesthetic sympathetic blockade for complex regional pain syndrome.
Complex regional pain syndrome (CRPS) is an umbrella term for a variety of clinical presentations characterised by chronic persistent pain that is disproportionate to any preceding injury and that is not restricted anatomically to the distribution of a specific peripheral nerve (Bruehl 2010). The diagnostic label of CRPS was introduced in the 1990s by the International Association for the Study of Pain (IASP) (Merskey 1994), and has since been updated in an attempt to improve its specificity (Harden 2006). These modified diagnostic criteria (the "Budapest criteria") can be seen in Table 1. It encompasses a variety of earlier diagnostic terms including reflex sympathetic dystrophy (RSD), reflex neurovascular dystrophy, Sudeck's atrophy, causalgia and algodystrophy/algoneurodystrophy. CRPS can be classified into two subtypes: CRPS-I, in which no peripheral nerve injury can be identified, and CRPS-II where symptoms are associated with a definable nerve lesion (Harden 2006). This distinction is not always easily made (Harden 2006). Both subtypes of CRPS are characterised by severe pain that is disproportionate to the inciting event, most commonly affecting the hand or foot but which can spread to other body regions (Stanton-Hicks 2002). Additionally CRPS presents with some or all of the following symptoms in the affected body parts: sensory disturbances, temperature changes, abnormal patterns of sweating, swelling/oedema, reduced joint range of motion, movement abnormalities such as weakness, tremor or dystonia, trophic changes such as skin atrophy, altered hair and nail growth or localised osteoporotic changes (Bruehl 2010; De Mos 2009; Shipton 2009), and alterations in body perception/schema (Lewis 2007; Lotze 2007; Moseley 2006). CRPS occurs most commonly following wrist fracture and subsequent immobilisation. However cases can potentially occur after any, often relatively minor, trauma and may even occur spontaneously, albeit rarely (De Mos 2007; De Mos 2008; Sandroni 2003). The underlying pathophysiological mechanisms of CRPS are incompletely understood although there is growing consensus that it is primarily a disorder of the nervous system. Abnormalities in the tissues of the affected area and the peripheral and central nervous systems have been identified (for review see Jänig 2003; Marinus 2011). These include signs of increased neurogenic inflammation (Birklein 2001; Schinkel 2006; Schmelz 2001), an altered local immune response (Tan 2005), altered activity in the sympathetic nervous system (SNS) (Drummond 2004; Niehof 2006) or increased sensitivity to normal SNS activity (Albrecht 2006; Ali 2000; Drummond 2001), and local tissue hypoxia (Birklein 2000; Koban 2003). Changes have also been demonstrated in the brain in CRPS (Swart 2009), including alterations of the cortical (higher brain) representation of the affected body part (Maihöfner 2004; Pleger 2006), localised reductions in grey matter density and connectivity (Geha 2008), and altered inhibitory control (Schwenkreis 2003).
Description of the intervention
Sympathetic blockade includes procedures that aim to temporarily impede the function of the sympathetic nervous system. This involves the injection of local anaesthetic directly into sympathetic neural structures that serve the affected limb(s) such as the stellate ganglion or the lumbar sympathetic chain (Nelson 2006). Accuracy of needle location is often ensured using radiologic guidance such as fluoroscopy or computerised tomography (CT) scan and successful blockade is often monitored by direct (e.g., galvanic skin response) or indirect (increase in lower extremity blood flow or increase in temperature) assessment (Breivik 2009). This approach is distinct from the injection of neurolytic agents in an effort to destroy sympathetic nerves.
How the intervention might work
People with persistent pain following nerve injury have long been observed to have abnormalities of autonomic nervous function in the affected limb (temperature, blood flow, sweating) and abnormal skin texture or hair and nail growth attributed, at least in part, to local autonomic dysfunction (Bruehl 2010; De Mos 2009). Early uncontrolled observations of persistent improvement in signs and symptoms following local anaesthetic sympathetic blockade in people with what is now termed CRPS suggested that excessive sympathetic activity provoked or perpetuated this type of persistent pain. However, recent evidence regarding adrenaline content in venous effluent from affected limbs has not supported this hypothesis (Binder 2009) and suggests instead that any benefit of sympathetic blockade in CRPS may reflect transient reversal of a heightened local sensitivity to adrenaline.These clinical impressions of persistent benefit from transient local anaesthetic sympathetic blockade in CRPS, reinforced by similar longstanding impressions of prolonged benefit after temporary local anaesthetics blockade in peripheral neuralgias (Carr 2011) led to the incorporation of sympathetic block into current consensus treatment algorithms for CRPS, although doubt remains over the contribution of the sympathetic nervous system to pain and the concept of sympathetically maintained pain in CRPS (Harden 2013).
Why it is important to do this review
Despite preclinical evidence that suggests that the sympathetic nervous system is involved in the pathophysiology of CRPS, there is debate surrounding the contribution of the sympathetic nervous system to the clinical syndrome (Ochoa 1995; Schott 1995; Verdugo 1994a; Verdugo 1994b) and on the value of blocking the sympathetic nervous system (Fine 1994;, Hogan 1997; Jadad 1995; Verdugo 1994a). It is therefore important to evaluate the efficacy of sympathetic blockade with local anaesthetic in the treatment of CRPS. A meta-analysis of the effect of sympathetic blockade with local anaesthetics in people with CRPS reported that up to 44% of those subjected to sympathetic blockade would be expected to have no pain relief. Due to the lack of randomised controlled trials this estimate was obtained from pooling the results of observational studies (Cepeda 2002). Moreover, the review only evaluated English-language studies and it could have overlooked relevant RCTs. Hence, to overcome this limitation, we decided to perform a systematic review of the literature with no language restriction to determine both the efficacy and the effectiveness of sympathetic blockade with local anaesthetics to alleviate pain in people with CRPS.
1. If local anaesthetic sympathetic blockade (LASB) is effective for providing pain relief to people with complex regional pain syndrome (CRPS);
2. How long the pain relief persists;
3. The incidence of adverse effects of the procedure.
Criteria for considering studies for this review
Types of studies
We considered for inclusion randomised controlled trials (RCTs). As blinding of sympathetic block is not always possible, we included trials that were either double-blind, single-blind, or open.
Types of participants
We included studies that evaluated the effect of sympathetic blockade with local anaesthetics to treat CRPS in children or in adults. Studies were included even if the authors did not describe the constellation of symptoms necessary to diagnose CRPS and stated only that, "patients with RSD/CRPS were included". We took this approach to avoid excluding any of the relatively few RCTs of this intervention. We placed no restrictions regarding the number of participants recruited to trials.
We excluded trials that evaluated sympathetic blockade for other pain syndromes such as radiculopathy, herpes zoster, postherpetic neuralgia, fibromyalgia or phantom pain.
Types of interventions
We included studies that evaluated selective sympathetic blockade with local anaesthetics. We excluded studies that only evaluated somatic nerve blocks or studies that evaluated the effect of local anaesthetics or sympatholytic drugs administered orally, intravenously or epidurally. The following were also exclusion criteria, added for this updated review: we excluded studies that reported the results of combined sympatholytic therapies, such as surgical sympathectomy or guanethidine regional block plus local anaesthetic blockade of the sympathetic chain. For this update we also excluded studies of ganglionide local opioid analgesia (GLOA), a technique in which opioids such as buprenorphine are injected locally into the stellate ganglion, because this technique does not block sympathetic activity; we also excluded studies in which sympathetic blocks were performed in people with herpes zoster and people with postherpetic neuralgia and fibromyalgia.
Types of outcome measures
The outcomes of interest were reduction in pain intensity levels, pain relief, or duration of pain relief, and the presence of adverse effects in each treatment arm. We excluded studies that did not present quantitative outcome data.
Search methods for identification of studies
For this update we expanded the search strategy to capture all the search terms for CRPS that are commonly used and all the search terms for sympathetic injections. Specifically we have added numerous versions of block/blockades for the various names that are used for these injections. We have also added botulinum toxin as this has only recently been used to block sympathetic activity (2009). Due to the small number of studies identified in the previous review, the goal was to create a search strategy that was as sensitive as possible. For the updated search strategies, please see Appendix 1 for MEDLINE, Appendix 2 for the Cochrane Central Register of Controlled Trials (CENTRAL), Appendix 3 for EMBASE, and Appendix 4 for LILACS.
The search for the original review was run from November 2003 to January 2004. We ran our updated search for the original review on November 17, 2011 and subsequent searches were run on November 22, 2012.
We evaluated non-English papers for inclusion.
We searched the following databases for the update of this review:
- Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2012, Issue 11, November)
- MEDLINE (1966 to November 2012)
- EMBASE (1974 to November 2012)
- LILACS (1982 to November 2012)
Searching other resources
We searched the bibliographies of retrieved articles for additional studies.
In order to minimise the impact of publication bias, we reviewed conference abstracts of the World Congresses of the International Association for the Study of Pain from 1995 up to 2011. For this update, we expanded the search of the original review by also searching relevant clinical trial registers (from inception) for upcoming trials. The following clinical trial registers were searched: the controlled trials register (November 30, 2012; www.controlled-trials.com/), the United States National Institute of Health service ClinicalTrials.gov (November 15, 2012; www.clinicaltrials.gov/); the Australian New Zealand Clinical trials register (November 15, 2012; www.anzctr.org.au/) and the European Clinical Trials Register (December 7, 2012; www.clinicaltrialsregister.eu/).
We attempted to communicate with authors if additional information was needed that was not provided in the trial report. In addition, we provided the reference list of included studies to experts in the field to determine if any additional references were appropriate for the review.
Data collection and analysis
Selection of studies
Two independent review authors read each of the titles and abstracts of the reports identified by the search and discarded narrative reviews, case series, or case reports. If there was no abstract, the report was retrieved in full. If there was disagreement, the authors met to reach consensus and if consensus could not be reached an independent third review author was consulted. All abstracts and reports that made reference to a trial of sympathetic blockade with local anaesthetics were retrieved in full. Two review authors then independently assessed the full-text articles. The reports were not anonymised for the assessment.
Data extraction and management
Assessment of risk of bias in included studies
For this update we adopted a modified version of the Cochrane 'Risk of bias' (RoB) tool with additional criteria added in response to the recommendations of Moore 2010. On this basis we added two criteria, 'Size' and 'Duration', using the thresholds for judgement suggested by Moore 2010. We have not added the 'Outcome' criterion as this is covered already by our choice of primary outcome measures. Thus in addition to the standard items in the RoB tool:
- selection bias (random sequence generation, allocation concealment),
- performance bias (blinding of participants and personnel),
- detection bias (blinding of outcome assessment)
- attrition bias (incomplete outcome data; consideration of analysis methods, e.g., imputation method)
- reporting bias (selective reporting)
- other sources of bias.
We also assessed the following criteria as recommended by Moore 2010:
- Size (studies with fewer than 50 participants per arm were rated as being at high risk of bias, those with between 50 and 199 participants per arm at unclear risk of bias, and 200 or more participants per arm at low risk of bias)
- Duration (studies with follow-up of two weeks were rated as being at high risk of bias, two to seven weeks at unclear risk of bias and eight weeks or longer at low risk of bias).
Two independent review authors extracted the data. If there was disagreement, a meeting was held to reach consensus and if consensus could not be reached an independent third review author was consulted. We extracted the following data from each study:
1. Study details: Study design (parallel or cross-over), method of randomisation, presence or absence of blinding;
2. Demographic characteristics: age, gender, number of participants recruited, number of study withdrawals or drop-outs, if any;
3. Participant disease characteristics: duration of pain before sympathetic block, site of pain (arm, leg, mixed or other such as facial);
4. Type of noxious initiating event: surgery, fracture, crush injury, projectile, or stab injury;
5. Type of tissue injured: nerve, soft tissue, bone;
6. Presence of medico-legal factors (that may influence the experience of pain and the outcomes of therapeutic interventions);
7. Concomitant treatments that may affect outcome: antidepressants, physical therapy, etc;
8. Treatment characteristics: site of sympathetic block (cervical or lumbar), type of local anaesthetic used, evaluation of the technical adequacy of the block, duration of follow-up, duration of the pain relief, number of blocks performed, method of pain assessment, and presence of complications or adverse effects;
9. Information on post-procedure analgesic requirements.
If pain intensity was reported using a visual analogue scale or numeric rating scale, we extracted the mean and standard deviation of pain intensity in each study arm. If pain relief was reported, we extracted the proportion of participants in each category of pain relief.
Measures of treatment effect
For this update we compared the post-treatment pain intensity scores between the treatment arms. Where possible, we calculated the proportion of participants with specific degree of pain relief and converted it into dichotomous information to yield the number of participants who obtained a moderately important benefit (30% pain relief) or a substantially important benefit (50% or more pain relief) as defined by the IMMPACT recommendations (Dworkin 2008). We calculated the risk ratio (RR) as the measure of treatment effect and used this to calculate the number-needed-to-treat (NNT) for 30% and 50% pain relief.
Dealing with missing data
Where insufficient data were presented in the study report to enter a study into the meta-analysis, we contacted study authors to request access to the missing data.
We pooled results where adequate data supported this, using Review Manager 5 software (RevMan 2012). Separate preplanned meta-analyses included sympathetic blockade versus sham/placebo procedure and sympathetic blockade versus no treatment or usual care. We used a random-effects model to combine the studies. We considered separate meta-analyses for short-term (0 to two weeks postintervention), mid-term (more than two to less than seven weeks postintervention) and long-term (seven weeks or longer postintervention) outcomes where adequate data were identified.
Subgroup analysis and investigation of heterogeneity
We assessed heterogeneity and its impact using the Chi² test and the I² test (Higgins 2003; Higgins 2011). Where significant heterogeneity (P < 0.1) was present we planned to conduct subgroup analyses. Preplanned comparisons included CRPS-I versus CRPS-II, children versus adults, and continuous versus single block.
Where possible we used the proportion of people with adverse side effects in each treatment group to calculate the number-needed-to-harm (NNH).
Assessment of reporting biases
We considered the possible influence of publication/small study biases on review findings. Where possible for studies that have utilised dichotomised outcomes we tested for the possible influence of publication bias on each outcome by estimating the number of participants in studies with zero effect required to change the NNTB to an unacceptably high level (defined as an NNTB of 10) as outlined by Moore 2008.
When sufficient data were available, we conducted sensitivity analyses on the following study factors: the effect of including/excluding studies classified as being at unclear or high risk of bias.
Description of studies
For this update we included an additional ten studies (Aydemir 2006; Bonelli 1983; Carroll 2009; Meier 2009; Nascimento 2010; Raja 1991; Rodriguez 2005; Toshniwal 2012; Wehnert 2002; Zeng 2003, combined n = 363). Overall we included 12 studies (n = 386).
Figure 1 presents a flowchart of the search screening process for the present update. A total of 1880 studies were identified by the database search strategy with an additional 968 studies identified through: hand-searching (n = 21); International Association for the Study of Pain (IASP) conference abstract searches (n = 356); clinical trial register searches (n = 591). After removal of duplicates and screening of titles and abstracts, we retrieved the full text for 34 studies. From these, we included 12 studies in the review. We excluded 16 studies as they did not use a randomised study design (Ackerman 2006; Arias 1989; Dellemijn 1994; Erickson 1993; Farcot 1990; Garrido 2005; Geurts 2006; Glynn 1993; Hartrick 2004; Linson 1983; Malmqvist 1992; Quevedo 2005; Schurmann 2001; Steinbrocker 1953; Wang 1985; Yucel 2009), two studies did not evaluate a local sympathetic blockade (Perrigot 1982; Tran 2000), two studies could not be confirmed as a new sample versus continuation of a previous study (Rodriguez 2006; Rodriguez 2008), and one study could not be retrieved (Salinas Cerda 1997). One additional study from a clinical trial registry met the inclusion criteria (Rocha 2012), but completion of data collection was estimated at November 2013. See the table Characteristics of excluded studies for summary details.
|Figure 1. Study flow diagram for updated searches|
The percentage agreement rate between the review authors (TS, BW) for screening of titles and abstracts was nearly perfect (99.9%) with only nine disagreements out of 2623 potential studies. The percentage agreement between the review authors for inclusion of studies was 88.2% with disagreements on 3 of 34 studies (Raja 1991; Wehnert 2002; Tran 2000). Two studies were included after discussion between the two review authors (Raja 1991; Wehnert 2002) and one was excluded (Tran 2000) after consultation with a third review author (NO).
We attempted to contact the authors of six papers; one for clarification of study population (Rodriguez 2005; two papers), two for retrieval of essential data (Nascimento 2010; Toshniwal 2012), one to determine if any data were present (Rocha 2012), and one to retrieve a manuscript that we were unable to source (Salinas Cerda 1997). Of these, we received correspondence and subsequent data from only two authors (Nascimento 2010; Toshniwal 2012). Two authors had been contacted in the original Cochrane review: Verdugo 1995 was contacted to determine if a paper in abstract form was published and the author reported that the trial had not been published in full (Verdugo 1995); Price 1998 was contacted to determine if a trial was randomised and the author confirmed that the trial was randomised.
Full details of the studies can be found in the Characteristics of included studies tables.
Eleven studies (Aydemir 2006; Bonelli 1983; Carroll 2009; Nascimento 2010; Price 1998; Raja 1991; Rodriguez 2005; Toshniwal 2012; Verdugo 1995; Wehnert 2002; Zeng 2003) included only adults and one study specifically included only children with CRPS (Meier 2009).
Seven studies (Aydemir 2006; Bonelli 1983; Nascimento 2010; Rodriguez 2005; Toshniwal 2012; Verdugo 1995; Zeng 2003) included only people with upper limb CRPS (treated with stellate ganglion blockade), two studies (Carroll 2009; Meier 2009) included only people with lower limb CRPS (treated with lumbar sympathetic blockade), and three studies (Price 1998; Raja 1991; Wehnert 2002) included a mixed group with either upper or lower limb CRPS.
Six studies used a cross-over design (Carroll 2009; Meier 2009; Price 1998; Raja 1991; Verdugo 1995; Wehnert 2002) and six a parallel design (Aydemir 2006; Bonelli 1983; Nascimento 2010; Rodriguez 2005; Toshniwal 2012; Zeng 2003). All included studies were small with total number of participants ranging from 7 to 82.
LASB versus placebo
We identified one new study comparing local anaesthetic sympathetic blockade (LASB) with placebo (Aydemir 2006) in addition to those identified for the previous update. Therefore only three studies (Aydemir 2006; Price 1998, Verdugo 1995) inform this comparison.
Price 1998 (n = 7) compared stellate ganglion block (four participants, 15 ml lidocaine 1%) or lumbar sympathetic block (three participants,10 ml bupivacaine 0.125%) with normal saline injection in people with CRPS of the upper or lower extremities based on the IASP diagnostic criteria. Verdugo 1995 (n = 16) compared a stellate ganglion block with bupivacaine (0.125%) to a normal saline injection in participants with CRPS of the upper extremity. Both studies investigated the proportion of participants who experienced 50% pain relief and Price 1998 also measured the duration of pain relief and the mean between-group difference in pain relief on a visual analogue scale (VAS). Aydemir 2006 compared stellate ganglion lidocaine block (10 ml lidocaine 1%) plus sham stellate ganglion ultrasound block (n = 9) to a double-sham condition (sham stellate ganglion lidocaine [10 ml saline] and ultrasound blocks; n = 7). Both groups received rehabilitation treatment. Spontaneous pain was measured post-treatment and at one-month follow-up.
LASB versus other interventions
In contrast to the previous version of this review we included studies which compared LASB to other interventions. Ten such trials were included (Aydemir 2006; Bonelli 1983; Carroll 2009; Meier 2009; Nascimento 2010; Raja 1991; Rodriguez 2005; Toshniwal 2012; Wehnert 2002; Zeng 2003).
Aydemir 2006 compared stellate ganglion lidocaine block (10 ml of 1%) plus sham stellate ganglion ultrasound block (n = 9) to stellate ganglion ultrasound 'block' (consisting of ultrasound delivered non-invasively over the stellate ganglion) plus sham stellate ganglion lidocaine block (10 ml of saline; n = 9). Both groups received rehabilitation treatment. The primary outcome of spontaneous pain was measured post-treatment and at one-month follow-up.
Bonelli 1983 (n = 19) compared stellate ganglion block with bupivacaine (15 ml of 0.5%; n=10) to intravenous regional blockade (IVRB) with guanethidine (20 mg; n=9) in patients with reflex sympathetic dystrophy. The primary outcome was the intensity of pain (measured using a 100mm linear scale) measured post-treatment at 15 minutes, 60 minutes, 24 hours and 48 hours as well as at one and 3 months.
Carroll 2009 (n = 9, of whom seven completed the study) compared sympathetic block with botulinum toxin A (75 units) plus bupivacaine (10 ml of 0.5%) with just bupivacaine (10 ml of 0.5%) in people with complex regional pain syndrome (CRPS) of the lower extremity. The primary outcome was the duration that pain (measured using a VAS) remained below baseline levels.
Meier 2009 (n = 23) compared lidocaine delivered intravenously (1% lidocaine; 0.1 ml/kg, maximum 6 ml) with lidocaine sympathetic block (1% lidocaine; 0.1 ml/kg, maximum 6 ml) in children with lower limb CRPS-I or CRPS-II. In a cross-over trial participants received intravenous (IV) lidocaine and a placebo sympathetic block or a lidocaine sympathetic block and placebo IV. Pain intensity (global 4-point verbal scale and colour analogue scale) was measured 30 minutes post-treatment.
Nascimento 2010 (n = 43) compared sympathetic block with lidocaine (70 mg 1% lidocaine) with sympathetic block with lidocaine (70 mg 1% lidocaine) plus clonidine (30 μg) or with IVRB with lidocaine plus clonidine (7.0 ml solution, 1% lidocaine, 1.μg/kg clonidine). Intensity of pain (VAS) and duration of pain relief were measured post-treatment and at one-week follow-up.
Two studies (Raja 1991; Wehnert 2002) compared lidocaine LASB with IV phentolamine. The primary aim of these studies was to investigate the utility of phentolamine in diagnosing sympathetically maintained pain, but given the design (cross-over) and outcome used we considered that they present efficacy data for single doses of these interventions in CRPS. Raja 1991 used 0.25% bupivacaine hydrochloride (10 ml for stellate ganglion blockade (SGB) and 20 ml for lumbar block) versus phentolamine at three- to eight-minute intervals in increasing dose (from 1 - 10 mg to 25 - 35 mg). Pain intensity (VAS) was measured post-treatment (exact length of follow-up unclear). Wehnert 2002 used 0.1 ml per 0.25%/cm in height (plus 500 mL NaCl 0.9%) versus 0.5 mg phentolamine/kg (plus 500 mL NaCl 0.9%) for 15 minutes. Pain intensity (VAS) was measured hourly post-treatment for 8 hours.
Rodriguez 2005 evaluated physical therapy plus pharmacological treatment with or without SGB (n = 41 per group,10 cc, equal parts 2% lidocaine and 0.5% bupivacaine) in people with upper limb CRPS with a confirmed sympathetic component to their pain (50% pain reduction with screening, pre-randomisation SGB). Pain intensity, therapeutic efficacy (proportion with at least 50% pain reduction) and relapse rate were measured at two months post-treatment.
Toshniwal 2012 compared continuous SGB (n = 18; 280 ml, 0.125% bupivacaine at 2 mL/hour for seven days) to continuous infraclavicular brachial plexus block (n = 12; 400 ml, 0.125% bupivacaine at 5 mL/hour for seven days) in people with CRPS Type I of the upper extremity. Physiotherapy sessions were given concurrently in both groups. The primary outcome was the subscale scores on the Neuropathic pain scale measured over a 4 week period post-treatment.
Zeng 2003 compared SGB (dose not reported) plus rehabilitation to rehabilitation only in a group (n = 60) with shoulder-hand syndrome following stroke. Pain (verbal rating scale) was measured at 10 and 20 days post-treatment.
Risk of bias in included studies
The results of the 'Risk of bias' assessment can be found in Figure 2 and Figure 3. Percentage agreement between review authors (TS, BW) for risk of bias ratings was 90.9% for the items of adequate sequence generation, blinding of participants/assessors, and presence of other bias; 81.8% for the item of freedom from cross-over effects, and 63.6% for the items of selective reporting of results and incomplete outcome data adequately addressed. There was perfect agreement for the remaining items. The two review authors resolved disagreements through discussion. No studies were considered to be at low risk of bias across all criteria.
|Figure 2. Risk of bias summary: review authors' judgements about each risk of bias item for each included study.|
|Figure 3. Risk of bias graph: review authors' judgements about each risk of bias item presented as percentages across all included studies.|
Only two studies (Meier 2009; Toshniwal 2012) clearly described an adequate randomisation process; the other ten studies were judged to be at unclear risk of bias for this criterion. Three studies were rated as being at a low risk of bias for allocation concealment (Aydemir 2006; Rodriguez 2005; Toshniwal 2012), three studies were at an unclear risk of bias (Bonelli 1983; Nascimento 2010; Zeng 2003); the remaining studies used a cross-over study design (risk of bias for allocation concealment not applicable).
Five studies were judged to have blinded participants and assessors adequately (Aydemir 2006; Carroll 2009; Meier 2009; Price 1998; Verdugo 1995). Five studies were judged to be at unclear risk of bias across these criteria (Bonelli 1983; Nascimento 2010; Raja 1991; Toshniwal 2012; Wehnert 2002) and in two studies blinding of the treatment conditions was not achievable, and were therefore judged to be at high risk of bias (Rodriguez 2005; Zeng 2003).
Incomplete outcome data
Two studies (Raja 1991; Wehnert 2002) were judged to be at high risk of bias for incomplete outcome data and three studies were judged to be at unclear risk (Aydemir 2006; Carroll 2009; Rodriguez 2005).
Data clearly free of carry-over effects?
Adequate sample size?
All studies were judged to be at high risk of bias with regard to sample size.
Adequate duration of follow up?
Other potential sources of bias
Two studies were judged to be at high risk of bias for other reasons. In Bonelli 1983 the LASB group had a significantly shorter duration of symptoms than the IVRB guanethidine group and were significantly older. In Rodriguez 2005, no baseline data were provided on pain intensity.
Sources of funding and conflicts of interest
While not formally included within the 'Risk of bias' assessment, we extracted information regarding study funding and potential conflicts of interest. Six study reports offered no details regarding these issues (Aydemir 2006; Bonelli 1983; Nascimento 2010; Price 1998; Wehnert 2002; Zeng 2003).
Carroll 2009 declared that the authors had filed a patent for the inclusion of botulinum toxin in sympathetic blocks. Four studies (Meier 2009; Raja 1991; Rodriguez 2005; Verdugo 1995) all declared financial support from governmental or non-profit organisations. No study declared funding from industry sources.
Effects of interventions
LASB versus placebo
Short-term pain relief
The first aim of this systematic review was to determine the likelihood of pain alleviation after sympathetic blockade with local anaesthetics:
In Price 1998 there was no difference between lidocaine or normal saline; the same number of participants (6/7) achieved at least 50% pain relief. In Verdugo 1995 12 of 16 participants had at least 50% pain relief while receiving bupivacaine versus 8 participants of 16 while receiving normal saline. The combined effect of these two small randomised double-blind trials produced a risk ratio (RR) to achieve at least 50% of pain relief 30 minutes to two hours after the sympathetic blockade of 1.18 (95% confidence interval (CI) 0.76 to 1.84, p=0.46); Analysis 1.1). In Aydemir 2006: spontaneous pain scores were no different from baseline to post-treatment in either the group receiving lidocaine (plus sham ultrasound SGB; Z = -0.18, P = 0.86) or in the group receiving sham lidocaine and sham ultrasound (Z = -0.76, P = 0.45). No between-group comparisons were reported.
Duration of pain relief
The second aim was to determine how long any pain relief persists:
Studies evaluated different long-term outcomes, which precluded the combination of the results. Price 1998 evaluated the duration of pain relief and Verdugo 1995 evaluated the number of participants who had at least 50% of pain relief. Verdugo 1995 found that 5 out of 16 patients had at least 50% of pain relief receiving local anaesthetic versus 8 out of 16 receiving normal saline 48 hours after the blockade; Price 1998 found that when local anaesthetic was administered the mean duration of relief was longer (three days) versus 19.9 hours when saline was administered. Interestingly, this study found that short-term relief was similar in both groups. In Aydemir 2006, spontaneous pain scores were no different from baseline to one-month follow-up in either the group receiving lidocaine (plus sham ultrasound SGB; Z = -1.05, P = 0.29) or in the group receiving sham lidocaine and sham ultrasound (Z = -0.68, P = 0.50). No between-group comparisons were reported. None of the included studies reported postintervention analgesic requirements.
LASB versus other interventions
Most comparative studies demonstrated no significant difference in pain between groups (Bonelli 1983; Nascimento 2010; Raja 1991; Wehnert 2002; Zeng 2003). One study did not explicitly report between-group differences (Aydemir 2006) although no within-group differences in spontaneous pain scores were found between baseline and post-treatment nor at one-month follow-up in either the group receiving lidocaine SGB plus sham ultrasound SGB (Z-scores listed above) or in the group receiving ultrasound SGB plus sham lidocaine (Z = -0.59, P = 0.55; Z = -0.63, P = 0.53, respectively). Due to the variation in the interventions there were not adequate data to allow pooling of the results.
Carroll 2009 reported a significantly longer duration of analgesia in the botulinum toxin group (median time to analgesic failure 71 days (95% CI 12 to 253)) compared with bupivacaine alone (< 10 days, 95% CI 0 to 12; P < 0.02). However, while the authors reported that pain intensity declined significantly in the botulinum toxin group they did not provide numeric pain scores for either treatment group.
Meier 2009 compared lumbar sympathetic blockade (LSB; via lidocaine given through the lumbar catheter) and IV saline to IV lidocaine and saline given through the lumbar catheter. They reported a significant improvement in verbal pain scores in the LSB group; 11 participants reported greater improvement in pain scores with LSB compared with IV (P = 0.05, Wilcoxin signed-ranks test), three participants reported a trend towards greater improvement with IV than with LSB, and improvement in pain scores was no different between groups in nine participants. No significant between-group difference was observed in mean spontaneous pain scores (colour analogue scale, mean difference LSB - IV = -0.5, 95% CI -1.4 to 0.5). There were no significant differences between pre- and post intervention spontaneous pain scores for either group (LSB group: pre-intervention median (range) pain scores: 5.4 (1.5 - 10), postintervention: 4.8 (1.4 - 10); IV group: pre-intervention: 6.0 (1.8 - 9.8), postintervention: 5.8 (1.6 - 10)).
Rodriguez 2005 reported the treatment efficacy at the two-month follow-up to be 46% in favour of the SGB group, an absolute risk reduction of 17% in favour of the SGB group with a number-needed-to-treat for an additional beneficial outcome (NNTB) of 6. The NNTB suggests that six people with CRPS would need to be treated with SGB (in addition to physical and pharmacological therapy) to prevent one relapse. There was a higher relapse rate in the control group (37%) versus the SGB group (20%); Hazard ratio: 2.7, 95% CI 1.1 to 6.7. The Kaplan-Meier estimates of the cumulative probability of not having a relapse at two months was 80% in the SGB group and 63% in the control group. However this study did not report the data for pain intensity, or the proportion who achieved meaningful pain relief.
Toshniwal 2012 reported significantly lower short-term pain scores in favour of the group receiving the continuous infraclavicular brachial plexus block versus the group receiving the continuous stellate ganglion block. Specifically,at 30 minutes, 2 hours and 12 hours, those receiving the continuous brachial plexus block had significantly lower intensity of pain (0.7, 0.5, 0.7, respectively) and unpleasantness of pain (0.7, 0.7, 0.8, respectively) scores compared with those receiving a continuous stellate ganglion block (intensity: 3.3, 2.7, 1.9; unpleasantness: 3, 2.7, 1.9; all P < 0.05). Dull pain scores were significantly reduced for the brachial plexus block group versus the stellate ganglion block group at 2 hours (0.1 versus 2.4), 12 hours (0.6 versus 1.9) and 24 hours (1.3 versus 2.6) with deep pain also significantly reduced at these time points (2 hours - 0.1 versus 2.3; 12 hours - 0.7 versus 1.6; 24 hours - 1.4 versus 2.4), as well as at 30 minutes post-cannulation (0.1 versus 2.3). There were no statistically significant differences between groups for short-term scores on any of the other Neuropathic Pain Scale components. Furthermore, there was no evidence of increased effectiveness of long-term pain relief for one group over the other, and no between-group differences were found at any other time points. Quality of pain score differences between groups were not statistically compared.
There were insufficient data to support a formal statistical analysis of reporting/small study biases for any comparison.
Reporting of adverse events was generally limited or missing from study reports. Only five studies provided specific data regarding adverse events.
Carroll 2009 reported moderate side effects in one participant (14.2%) following the botulinum toxin type A LASB. This participant had significant nausea and emesis that began 5 hours after the injection and lasted 2 days, resolving spontaneously.
Meier 2009 found mild side effects for both groups. They reported a higher frequency of adverse effects in the IV lidocaine group (placebo sympathetic block) including headaches (17.4%; 4/23), lightheadedness (30.4%; 7/23), nausea (4.4%; 1/23), blurred vision (4.4%; 1/23), muffled sounds (4.4%; 1/23) and oral numbness (4.4%; 1/23). In the sympathetic block group (placebo IV), only lightheadedness was reported by 26.1% (6/23).
Nascimento 2010 also found mild side effects for all three groups. The SGB group receiving lidocaine and clonidine (Group 2) reported the highest frequency of side effects: 93.3% reported drowsiness (14/15), 13.3% dizziness (2/15), 13.3% hoarseness (2/15), 6.7% reported pain at the injection site (1/15), and 26.7% reported a feeling of dry mouth (4/15). The SGB group receiving only lidocaine (Group 1) reported the lowest frequency of side effects with nausea occurring in 6.5% (1/14), dizziness in 14.3% (2/14), hoarseness in 6.5% (1/14), and pain at the injection site in 6.5% (1/14). Lastly, the group receiving the IV regional block with lidocaine and clonidine (Group 3) reported drowsiness (46.1%; 6/13) and dizziness (7.7%;1/13).
Raja 1991 found mild side effects for the IV phentolamine group, with 55.6% (10/18) reporting nasal stuffiness, 16.7% (3/18) reporting headache and 11.1% (2/18) reporting dizziness. It is unclear whether adverse events were present for the lidocaine LASB group as this was not reported.
Toshniwal 2012 found side effects in both groups. In the continuous stellate ganglion block group, Horner's syndrome was most common (94.7%) while initial motor weakness was the most common side effect in the continuous infraclavicular brachial plexus group (100%). Positive catheter tip culture occurred in 61.1% (11/18) of the stellate ganglion block group and in 8.3% (1/12) in the brachial plexus group; no signs of infection at the catheter site were observed in either group. Catheter migration was found in 5.2% (1/19) of the stellate ganglion block group (versus 7.1% (1/14) of the brachial plexus group). Lastly, hoarseness of voice (for initial 12 hours) was found in 16.7% (3/18) of participants in the stellate ganglion block group.
Summary of main results
This systematic review had three objectives:
- To determine if local anaesthetic sympathetic blockade (LASB) is effective for providing pain relief to people with complex regional pain syndrome (CRPS);
- to assess how long pain relief persists;
- and to evaluate the incidence of adverse effects of the procedure.
Previous versions of this review revealed the scarcity of published evidence to support the use of LASB for CRPS and raised questions about its efficacy.
LASB versus placebo or no treatment
This update reveals little progress in developing high quality evidence to support this intervention since the last updates in 2005 and 2010. There are only three placebo-controlled randomised studies that met our inclusion criteria (Aydemir 2006; Price 1998; Verdugo 1995), all of which have very small sample sizes. No firm conclusions can be drawn from this evidence. It is notable that the results to date are not suggestive of a significant effect of LASB over placebo even in the very short term (30 minutes to two hours). We could not estimate the duration of pain relief, if any.
LASB versus other interventions
In a change from previous versions of this review we took the decision to include trials which compared LASB with alternative interventions, or that evaluated the effect of adding LASB to other treatments. We identified a number of such studies which investigated a range of comparisons, and the majority of these demonstrated no significant difference between the intervention and control groups. It is notable that in one small study (Bonelli 1983) LASB did not demonstrate superior effectiveness when compared to intravenous regional blockade (IVRB) with guanethidine, an intervention for which there is consistent evidence of inefficacy (Jadad 1995; McQuay 1997).
One small study provided limited evidence that, compared with LASB alone, sympathetic blockade with botulinum toxin A added to local anaesthetic (LA) may prolong analgesia (Carroll 2009). Another single study provided limited evidence to suggest that when added to usual physical therapy and pharmacological treatment LASB may reduce the risk of relapse (Rodriguez 2005) but this study was found to be at high risk of bias across multiple criteria, did not report data for pain relief, and the lack of a sham condition raises the possibility that the observed improvement may have resulted from non-specific effects. In contrast, Zeng 2003 found no benefit of adding cervical sympathetic blockade to usual comprehensive rehabilitative treatment for pain outcomes. In children with CRPS, Meier 2009 did not clearly demonstrate the superiority of LASB compared with IV lidocaine for our primary outcome of pain relief (termed 'spontaneous pain' by Meier 2009), although larger reductions in forms of evoked pain (outcomes not included in this review) were seen after LASB.
There is limited evidence that, compared with continuous infraclavicular brachial plexus blocks, continuous stellate ganglion LASB results in less relief in short-term pain intensity, pain unpleasantness, deep pain and dull pain (Toshniwal 2012). The same study also provides limited evidence of no difference in longer-term pain relief (up to four weeks) between groups (Toshniwal 2012).
Given the limited evidence available and the various sources of potential bias and uncertainty, we would conclude that there is little to no credible evidence to support the use of LASB for CRPS and that the majority of the limited evidence available suggests that LASB may be ineffective.
The reporting of adverse events in the identified studies was inconsistent and limited. Only four studies provided complete data (Carroll 2009; Meier 2009; Nascimento 2010; Toshniwal 2012). Given this lack of reporting and the small size of all of the included studies we can draw no confident conclusions regarding the safety of LASB. While those adverse events that have been reported appear to be minor, the potential for rare but serious adverse events can not be ruled out. It is likely that to get a better estimate of the incidence and nature of adverse events we would need to review evidence from non-randomised observational study designs, but that was beyond the scope of this review.
Overall completeness and applicability of evidence
By undertaking a systematic search of unpublished and grey literature and consulting experts in the field we have limited the risk of excluding important and relevant evidence. Of the included studies, all were judged as being at unclear risk of bias on at least one criterion, reflecting a common lack of clarity in many study reports, and three were judged as being at high risk of bias specifically for the selective reporting of outcomes. This represents a significant challenge to a confident interpretation of an already limited evidence base. Two of the included studies (Raja 1991; Wehnert 2002) primarily aimed to investigate the comparative utility of LASB as a method of diagnosing sympathetically-maintained pain (SMP), rather than the efficacy of LASB as a treatment. We included these studies to provide evidence regarding the effectiveness of a single LASB.
We attempted to contact the authors of five studies, with mixed success. Two responded and provided necessary data (Nascimento 2010; Toshniwal 2012). However, as we were unable to source one study despite numerous efforts (Salinas Cerda 1997), and unable to include two studies (Rodriguez 2006; Rodriguez 2008) due to lack of clarity over the participant population (i.e., different from previously published studies?), it is possible that we are missing relevant data.
Quality of the evidence
None of the included studies was judged as being at low risk of bias across all criteria. Indeed, all but two studies were judged as being at unclear risk of bias for random sequence generation and for allocation concealment. These factors have been demonstrated to exaggerate the effects of studies, particularly those with subjective outcomes, such as pain (Schulz 1995; Wood 2008). All studies were judged to be at high risk of bias for inadequate sample size and only two studies were judged as being at low risk of bias for adequate duration of follow-up. Small studies may well be underpowered to detect a clinical effect but conversely there is empirical evidence that small published clinical trials in pain have a tendency to exaggerate treatment effects (Moore 2010; Nüesch 2010).These numerous sources of potential bias might alone explain any observed positive effects in the included studies. As such, all of the evidence identified should be interpreted with caution.
Potential biases in the review process
While we have attempted to identify all eligible trials using a comprehensive search strategy, it remains possible that we may have missed some key literature. The inclusion of two studies (Raja 1991; Wehnert 2002) that primarily sought to investigate the utility of LASB as a diagnostic tool for sympathetically-maintained pain may be contentious. These studies recruited participants with CRPS in which sympathetic dysfunction had not been demonstrated. However the same can be said for the majority of included studies. Only three included studies used a positive response to a prior LASB to attempt to establish SMP as part of their inclusion criteria (Carroll 2009; Price 1998; Rodriguez 2005). This speaks to a wider issue concerning the use of LASB in CRPS. It is possible that LASB might only be effective in a subgroup of people with CRPS with sympathetic dysfunction, or perhaps characterised by other factors. However, to date evidence of predictors of a positive response to LASB are elusive (Sethna 2012).
Agreements and disagreements with other studies or reviews
Our results do not change the overall conclusions of earlier versions of this review. Similarly a number of earlier systematic reviews have included evaluations of the evidence for LASB (Forouzanfar 2002; Perez 2010; Tran 2010) and all have similarly agreed that the evidence is limited and that there is no clear evidence for the efficacy of LASB.
Implications for practice
The limited data available, both in terms of size and quality, do not suggest that local anaesthetic sympathetic blockade (LASB) is superior to placebo in the treatment of complex regional pain syndrome (CRPS) or to a range of other interventions. Only one study, judged to be at high risk of bias, suggests that LASB may reduce the risk of recurrence of pain when added to rehabilitation and standard pharmacological care. However on the basis of such evidence it is not possible to make any clinical recommendations. There is currently little credIble evidence to support the use of LASB for CRPS.
Implications for research
If LASB is to continue to be offered to people with CRPS, there is a clear need for further, better quality research into its efficacy. It seems likely that the best chance of delivering high quality trials is through multi-centre, international collaborative research projects which might recruit from larger clinical populations. Future trials should use established diagnostic criteria and clearly report the type of CRPS under investigation. Trials should also consider the recent IMMPACT recommendations (Dworkin 2008; Dworkin 2009; Dworkin 2010; Turk 2008a; Turk 2008b) for the design of trials in pain to ensure that outcomes, thresholds for clinical importance and study designs are optimal. Furthermore, future trials should adhere to the CONSORT guidance (Altman 2012) on standards of reporting, and should clearly report all adverse events.
We thank the Pain, Palliative and Supportive Care Review Group for running the searches and supporting the review process.
We would also like to thank Arturo Lawson, Murat Dalkilinc, Luciana Macedo, Ann Meulders, Eric Parent, Andrea Wand and Eva Bosch for their assistance in interpreting non-English language trials.
Data and analyses
- Top of page
- Authors' conclusions
- Data and analyses
- What's new
- Contributions of authors
- Declarations of interest
- Sources of support
- Differences between protocol and review
- Index terms
Appendix 1. MEDLINE search strategy
1 exp Complex Regional Pain Syndromes/
2 complex regional pain syndrome.mp.
4 reflex sympathetic dystrophy.mp.
5 reflex neurovascular dystrophy.mp.
6 (RSD or RND).mp.
7 shoulder hand syndrome.mp.
12 (sympathetic* adj3 pain*).mp.
14 ((posttraumatic or post-traumatic) adj dystrophy).mp.
15 neuralgia.mp. or exp Neuralgia/
16 1 or 2 or 3 or 4 or 5 or 6 or 7 or 8 or 9 or 10 or 11 or 12 or 13 or 14 or 15
17 exp Sympatholytics/
18 exp Nerve Block/
19 exp Anesthetics, Local/
23 (nerve* adj5 block*).mp.
24 (stellate adj5 block*).mp.
25 (sympathetic* adj5 block*).mp.
27 (local adj5 (anaesthetic* or anesthetic*)).mp.
28 17 or 18 or 19 or 20 or 21 or 22 or 23 or 24 or 25 or 26 or 27
29 16 and 28
30 randomized controlled trial.pt.
31 controlled clinical trial.pt.
34 drug therapy.fs.
38 30 or 31 or 32 or 33 or 34 or 35 or 36 or 37
39 29 and 38
Appendix 2. CENTRAL search strategy
#1 MeSH descriptor: [Complex Regional Pain Syndromes] explode all trees
#2 complex regional pain syndrome
#3 reflex sympathetic dystrophy
#4 reflex neurovascular dystrophy
#5 (RSD or RND)
#6 shoulder hand syndrome
#11 (sympathetic* near/3 pain*)
#13 ((posttraumatic or post-traumatic) next dystrophy)
#15 MeSH descriptor: [Neuralgia] explode all trees
#16 #1 or #2 or #3 or #4 or #5 or #6 or #7 or #8 or #9 or #10 or #11 or #12 or #13 or #14 or #15
#17 MeSH descriptor: [Sympatholytics] explode all trees
#18 MeSH descriptor: [Nerve Block] explode all trees
#19 MeSH descriptor: [Anesthetics, Local] explode all trees
#23 (nerve* near/5 block*)
#24 (stellate near/5 block*)
#25 (sympathetic* near/5 block*)
#27 (local near/5 (anaesthetic* or anesthetic*))
#28 #17 or #18 or #19 or #20 or #21 or #22 or #23 or #24 or #25 or #26 or #27
#29 #16 and #28
Appendix 3. EMBASE search strategy
1 exp Complex Regional Pain Syndromes/ (6878)
2 complex regional pain syndrome.mp. (4608)
3 CRPS.mp. (1726)
4 reflex sympathetic dystrophy.mp. (2181)
5 reflex neurovascular dystrophy.mp. (22)
6 (RSD or RND).mp. (13575)
7 shoulder hand syndrome.mp. (522)
8 algoneurodystrophy.mp. (77)
9 algodystrophy.mp. (1014)
10 sudeck*.mp. (691)
11 causalgia.mp. (1077)
12 (sympathetic* adj3 pain*).mp. (1851)
13 SMP.mp. (1349)
14 ((posttraumatic or post-traumatic) adj dystrophy).mp. (39)
15 neuralgia.mp. or exp Neuralgia/ (67140)
16 or/1-15 (83936)
17 exp Sympatholytics/ (323887)
18 exp Nerve Block/ (23581)
19 exp Anesthetics, Local/ (176914)
20 bupivacaine.mp. (28226)
21 lidocaine.mp. (60809)
22 guanethidine.mp. (9806)
23 (nerve* adj5 block*).mp. (26239)
24 (stellate adj5 block*).mp. (1455)
25 (sympathetic* adj5 block*).mp. (4992)
26 sympatholytic*.mp. (1986)
27 (local adj5 (anaesthetic* or anesthetic*)).mp. (40074)
28 or/17-27 (514951)
29 16 and 28 (9126)
30 random$.tw. (778937)
31 factorial$.tw. (20300)
32 crossover$.tw. (45775)
33 cross over$.tw. (20846)
34 cross-over$.tw. (20846)
35 placebo$.tw. (187218)
36 (doubl$ adj blind$).tw. (138732)
37 (singl$ adj blind$).tw. (13056)
38 assign$.tw. (216590)
39 allocat$.tw. (73290)
40 volunteer$.tw. (168077)
41 Crossover Procedure/ (35530)
42 double-blind procedure.tw. (224)
43 Randomized Controlled Trial/ (334989)
44 Single Blind Procedure/ (16651)
45 or/30-44 (1279784)
46 (animal/ or nonhuman/) not human/ (4530619)
47 45 not 46 (1128169)
48 29 and 47 (1039)
49 (201111* or 201112* or 2012*).dd. (1342582)
50 48 and 49 (133)
Appendix 4. LILACS search strategy
"complex regional pain syndrome" or CRPS or "reflex sympathetic dystrophy" or "reflex neurovascular dystrophy" or RSD or RND or "shoulder hand syndrome" or algoneurodystrophy or algodystrophy or sudeck$ or causalgia or sympathetic pain$ or SMP [Words] and bupivacaine or lidocaine or guanethidine or (nerve$ block$) or (stellate block$) or (sympathetic$ block$) or sympatholytic$ or (local anaesthetic$) or (local anesthetic$) [Words]
Last assessed as up-to-date: 31 July 2013.
Protocol first published: Issue 1, 2004
Review first published: Issue 4, 2005
Contributions of authors
TRS: Led the modification and writing of the protocol; performed the literature search; screened, identified and evaluated studies; extracted data; led the data synthesis and the writing of the manuscript.
BMW: Informed the modification of the protocol; screened, identified and evaluated studies; extracted data and contributed to the writing of the manuscript.
DBC: Designed the original protocol and consulted on the modifications; contributed to the writing of the manuscript.
GW: Informed the modification of the protocol and contributed to the writing of the manuscript.
FB: Informed the modification of the protocol; assisted in the clinical trial register searches and contributed to the writing of the manuscript.
NEO: Informed the modification of the protocol; acted as the arbiter reviewer; informed the data synthesis and contributed to the writing of the manuscript.
Declarations of interest
Sources of support
- No sources of support supplied
- Saltonstall Foundation, USA.
- Javeriana University School of Medicine, Colombia.
Differences between protocol and review
This updated review used an expanded search strategy. In particular, additional search terms were utilized and we also searched clinical trial registers for potentially relevant studies. Further, an updated version of the Risk of Bias (ROB) assessment was used - specifically, 'size of treatment groups' and 'duration of follow-up' of the studies were included in the ROB evaluation. Last, this updated review also included studies in which local anaesthetic blockade (LASB) was compared with other active treatments (original review compared LASB with placebo/inert treatments only).
Medical Subject Headings (MeSH)
*Anesthetics, Local; Autonomic Nerve Block [*methods]; Causalgia [drug therapy]; Complex Regional Pain Syndromes [*drug therapy]; Randomized Controlled Trials as Topic; Reflex Sympathetic Dystrophy [drug therapy]
MeSH check words
Adult; Child; Humans