Systematic Reviews and Meta-analyses in Regional Anesthesia and Pain Medicine (Part I): Guidelines for Preparing the Review Protocol.

Comprehensive resources exist on how to plan a systematic review and meta-analysis. The objective of this article is to provide guidance to authors preparing their systematic review protocol in the fields of regional anesthesia and pain medicine. The focus is on systematic reviews of health care interventions, with or without an aggregate data meta-analysis. We describe and discuss elements of the systematic review methodology that review authors should prespecify, plan, and document in their protocol before commencing the review. Importantly, authors should explain their rationale for planning their systematic review and describe the PICO framework-participants (P), interventions (I), comparators (C), outcomes (O)-and related elements central to constructing their clinical question, framing an informative review title, determining the scope of the review, designing the search strategy, specifying the eligibility criteria, and identifying potential sources of heterogeneity. We highlight the importance of authors defining and prioritizing the primary outcome, defining eligibility criteria for selecting studies, and documenting sources of information and search strategies. The review protocol should also document methods used to evaluate risk of bias, quality (certainty) of the evidence, and heterogeneity of results. Furthermore, the authors should describe their plans for managing key data elements, the statistical construct used to estimate the intervention effect, methods of evidence synthesis and meta-analysis, and conditions when meta-analysis may not be possible, including the provision of practical solutions. Authors should provide enough detail in their protocol so that the readers could conduct the study themselves.

Systematic Reviews and Meta-analyses in Regional Anesthesia and Pain Medicine (Part II): Guidelines for Performing the Systematic Review.

In Part I of this series, we provide guidance for preparing a systematic review protocol. In this article, we highlight important steps and supplement with exemplars on conducting and reporting the results of a systematic review. We suggest how authors can manage protocol violations, multiplicity of outcomes and analyses, and heterogeneity. The quality (certainty) of the evidence and strength of recommendations should follow the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach. It is our goal that Part II of this series provides valid guidance to authors and peer reviewers who conduct systematic reviews to adhere to important constructs of transparency, structure, reproducibility, and accountability. This will likely result in more rigorous systematic reviews being submitted for publication to the journals like Regional Anesthesia & Pain Medicine and Anesthesia & Analgesia .

Standardizing nomenclature in regional anesthesia: an ASRA-ESRA Delphi consensus study of upper and lower limb nerve blocks.

BACKGROUND: Inconsistent nomenclature and anatomical descriptions of regional anesthetic techniques hinder scientific communication and engender confusion; this in turn has implications for research, education and clinical implementation of regional anesthesia. Having produced standardized nomenclature for abdominal wall, paraspinal and chest wall regional anesthetic techniques, we aimed to similarly do so for upper and lower limb peripheral nerve blocks. METHODS: We performed a three-round Delphi international consensus study to generate standardized names and anatomical descriptions of upper and lower limb regional anesthetic techniques. A long list of names and anatomical description of blocks of upper and lower extremities was produced by the members of the steering committee. Subsequently, two rounds of anonymized voting and commenting were followed by a third virtual round table to secure consensus for items that remained outstanding after the first and second rounds. As with previous methodology, strong consensus was defined as ≥75% agreement and weak consensus as 50%-74% agreement. RESULTS: A total of 94, 91 and 65 collaborators participated in the first, second and third rounds, respectively. We achieved strong consensus for 38 names and 33 anatomical descriptions, and weak consensus for five anatomical descriptions. We agreed on a template for naming peripheral nerve blocks based on the name of the nerve and the anatomical location of the blockade and identified several areas for future research. CONCLUSIONS: We achieved consensus on nomenclature and anatomical descriptions of regional anesthetic techniques for upper and lower limb nerve blocks, and recommend using this framework in clinical and academic practice. This should improve research, teaching and learning of regional anesthesia to eventually improve patient care.

Systematic reviews and meta-analyses in regional anesthesia and pain medicine (Part II): guidelines for performing the systematic review.

In Part I of this series, we provide guidance for preparing a systematic review protocol. In this article, we highlight important steps and supplement with exemplars on conducting and reporting the results of a systematic review. We suggest how authors can manage protocol violations, multiplicity of outcomes and analyses, and heterogeneity. The quality (certainty) of the evidence and strength of recommendations should follow the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach. It is our goal that Part II of this series provides valid guidance to authors and peer reviewers who conduct systematic reviews to adhere to important constructs of transparency, structure, reproducibility, and accountability. This will likely result in more rigorous systematic reviews being submitted for publication to the journals like Regional Anesthesia & Pain Medicine and Anesthesia & Analgesia.

Systematic reviews and meta-analyses in regional anesthesia and pain medicine (Part I): guidelines for preparing the review protocol.

Comprehensive resources exist on how to plan a systematic review and meta-analysis. The objective of this article is to provide guidance to authors preparing their systematic review protocol in the fields of regional anesthesia and pain medicine. The focus is on systematic reviews of healthcare interventions, with or without an aggregate data meta-analysis. We describe and discuss elements of the systematic review methodology that review authors should prespecify, plan, and document in their protocol before commencing the review. Importantly, authors should explain their rationale for planning their systematic review and describe the PICO framework-participants (P), interventions (I),comparators (C), outcomes (O)-and related elements central to constructing their clinical question, framing an informative review title, determining the scope of the review, designing the search strategy, specifying the eligibility criteria, and identifying potential sources of heterogeneity. We highlight the importance of authors defining and prioritizing the primary outcome, defining eligibility criteria for selecting studies, and documenting sources of information and search strategies. The review protocol should also document methods used to evaluate risk of bias, quality (certainty) of the evidence, and heterogeneity of results. Furthermore, the authors should describe their plans for managing key data elements, the statistical construct used to estimate the intervention effect, methods of evidence synthesis and meta-analysis, and conditions when meta-analysis may not be possible, including the provision of practical solutions. Authors should provide enough detail in their protocol so that the readers could conduct the study themselves.

Standardizing nomenclature in regional anesthesia: an ASRA-ESRA Delphi consensus study of abdominal wall, paraspinal, and chest wall blocks.

BACKGROUND: There is heterogeneity in the names and anatomical descriptions of regional anesthetic techniques. This may have adverse consequences on education, research, and implementation into clinical practice. We aimed to produce standardized nomenclature for abdominal wall, paraspinal, and chest wall regional anesthetic techniques. METHODS: We conducted an international consensus study involving experts using a three-round Delphi method to produce a list of names and corresponding descriptions of anatomical targets. After long-list formulation by a Steering Committee, the first and second rounds involved anonymous electronic voting and commenting, with the third round involving a virtual round table discussion aiming to achieve consensus on items that had yet to achieve it. Novel names were presented where required for anatomical clarity and harmonization. Strong consensus was defined as ≥75% agreement and weak consensus as 50% to 74% agreement. RESULTS: Sixty expert Collaborators participated in this study. After three rounds and clarification, harmonization, and introduction of novel nomenclature, strong consensus was achieved for the names of 16 block names and weak consensus for four names. For anatomical descriptions, strong consensus was achieved for 19 blocks and weak consensus was achieved for one approach. Several areas requiring further research were identified. CONCLUSIONS: Harmonization and standardization of nomenclature may improve education, research, and ultimately patient care. We present the first international consensus on nomenclature and anatomical descriptions of blocks of the abdominal wall, chest wall, and paraspinal blocks. We recommend using the consensus results in academic and clinical practice.

A pilot randomized-controlled trial evaluating the erector spinae plane block in thoracic and breast surgery.

PURPOSE: This pilot study evaluated the feasibility of investigating the effect of the erector spinae plane (ESP) block on the patient-centred outcomes of quality of recovery-15 (QoR-15), and brief pain inventory (BPI) in thoracic and breast surgery patients. METHODS: In this randomized-controlled pilot trial, 82 patients undergoing video-assisted thoracoscopic surgery (n = 77) and mastectomy (n = 5) received either continuous ESP block with ropivacaine (ropivacaine group) or the same procedure with 0.9% saline (saline group). All patients received surgical intercostal block (thoracic surgery) or local anesthetic infiltration (breast surgery). Feasibility as the primary outcome was evaluated on recruitment (three patients per week), catheter retention (above 90% at 24 hr), and patient attrition (less than 10%). Secondary outcomes comprised of QoR-15, BPI, and opioid consumption. RESULTS: Recruitment rate was 1.8 patients per week. Catheters were retained in 77 patients (94%) at 24 hr. At three months, five patients were lost to follow-up (6%). At 24 hr compared with baseline, the ropivacaine group had a smaller decline in QoR-15 score (median difference, 14; 95% confidence interval [CI], 2 to 26; P = 0.02) and a smaller increase in BPI global score (median difference, 14; 95% CI, 0 to 24; P = 0.048). There was no difference in opioid consumption (P = 0.08). CONCLUSIONS: In this pilot study, the target recruitment rate was not met, but catheter retention and patient attrition rates were both satisfactory. A definitive trial with QoR-15 as the primary outcome would require 300 study participants. TRIAL REGISTRATION: Australian New Zealand Clinical Trials Registry (ID12618000701224); registered 30 April 2018.

RéSUMé: OBJECTIF: Cette étude pilote a évalué la faisabilité d'explorer l'effet d'un bloc du plan des muscles érecteurs du rachis sur des résultats centrés sur le patient, soit la qualité de récupération (QoR-15) et le Questionnaire concis de la douleur (QCD ou BPI 'Brief Pain Inventory'), chez les patients de chirurgie thoracique et mammaire. MéTHODE: Dans cette étude pilote randomisée contrôlée, 82 patients subissant une chirurgie thoracoscopique (n = 77) ou une mastectomie (n = 5) ont reçu soit un bloc continu du plan des muscles érecteurs du rachis avec de la ropivacaïne (groupe ropivacaïne), ou la même intervention avec une solution saline à 0,9 % (groupe salin). Tous les patients ont reçu un bloc intercostal chirurgical (chirurgie thoracique) ou une infiltration d'anesthésique local (chirurgie mammaire). La faisabilité a été évaluée par les critères de recrutement (trois patients par semaine), de la rétention du cathéter (plus de 90 % à 24 h), et du taux d'attrition des patients (moins de 10 %). Les critères d'évaluation secondaires comportaient la QoR-15, le QCD et la consommation d'opioïdes. RéSULTATS: Le taux de recrutement était de 1,8 patients par semaine. Les cathéters sont restés en place chez 77 patients (94 %) à 24 h. À trois mois, cinq patients ont été perdus au suivi (6 %). Après 24 h, par rapport aux valeurs de base, le groupe ropivacaïne présentait un déclin plus léger du score de QoR-15 (différence médiane, 14; intervalle de confiance [IC] 95 %, 2 à 26; P = 0,02) ainsi qu'une augmentation moindre du score global de QCD (différence médiane, 14; IC 95 %, 0 à 24; P = 0,048). Aucune différence n'a été observée en matière de consommation d'opioïdes (P = 0,08). CONCLUSION: Dans cette étude pilote, le taux de recrutement cible n'a pas été atteint, mais les taux de rétention des cathéters et d'attrition des patients étaient tous deux satisfaisants. Une étude définitive de la QoR-15 en tant que critère d'évaluation principal nécessiterait le recrutement de 300 participants. ENREGISTREMENT DE L'éTUDE: Australian New Zealand Clinical Trials Registry (ID12618000701224); enregistrée le 30 avril 2018.

Ultrasound-guided blocks for cardiovascular surgery: which block for which patient?

PURPOSE OF REVIEW: Regional anesthesia blocks may benefit patients undergoing cardiovascular surgery. This review coincides with the evolution of ultrasound-guided fascial plane blocks, societal concerns regarding opioid misuse and changing expectations regarding surgical recovery. RECENT FINDINGS: Paravertebral block and thoracic epidural analgesia have comparable postoperative analgesic profiles following thoracotomy; however, the former has a more favorable complication profile. Limited trials have compared these modalities in cardiac surgery. The mechanism of action of continuous paravertebral blockade may be systemic. Bilateral continuous paravertebral (and other continuous peripheral nerve blocks) should be used with caution in adult patients having cardiac surgery because of the risk of systemic local anesthetic toxicity and bleeding. Novel ultrasound-guided blocks: erector spinae, serratus anterior, pectoral, transversus thoracic muscle and pecto-intercostal fascial plane blocks potentially reduce postoperative opioid requirements; however, they require further investigation before their routine use can be recommended in adult cardiovascular surgical practice. The mechanism of action of erector spinae block is not fully elucidated. SUMMARY: Ultrasound-guided fascial plane blocks may reduce postoperative opioid requirements. Investigation into the safety and efficacy of bilateral continuous ultrasound-guided blockade for cardiac surgery is required. Trial protocols should be embedded into enhanced recovery after surgery programs. Patient-reported and long-term outcomes are recommended.

Quality of Recovery After Breast Surgery: A Multicenter Randomized Clinical Trial Comparing Pectoral Nerves Interfascial Plane (Pectoral Nerves II) Block With Surgical Infiltration.

BACKGROUND: Pectoral nerves (PECS II) block is a popular regional analgesia technique for breast surgery. PECS II block or local infiltration by surgeon may improve outcomes including quality of recovery (QoR). METHODS: In this multicenter randomized clinical trial, 104 female patients undergoing breast surgery received: (1) PECS II block with local anesthetic and surgical infiltration with 0.9% saline (PECS group) or (2) PECS II block with 0.9% saline and surgical infiltration with local anesthetic (infiltration group). Patients, anesthetists, surgeons, nursing staff, and research assistants were blinded to group allocation. Patients received standardized general anesthesia and multimodal analgesia. The primary outcome was the global score (maximum score, 150; good recovery, 118) of the multidimensional (pain, comfort, independence, psychological, emotional) QoR-15 questionnaire measured 24 hours postoperatively. Secondary outcomes were pain, and its functional interference measured 24 hours and 3 months postoperatively using the Brief Pain Inventory (BPI) short form (0, optimal; 120, worst possible). Randomly assigned groups were compared on outcomes using the Wilcoxon rank-sum test, and the results were reported as median difference with 95% confidence interval. RESULTS: One hundred eight patients were recruited from August 17, 2016 to June 8, 2018, and 4 patients were withdrawn. Twelve patients from 104 had mastectomy, with the remainder having less invasive surgery. Baseline QoR-15 global scores reported as median [quartiles] were 135 [129, 143] in the PECS group and 139 [127, 143] in the infiltration group. The 24-hour QoR-15 global score reported as median [quartiles] was 131 [116, 140] in the PECS group and 123 [117, 143] in the infiltration group (P = .60), with median difference (95% confidence interval) of -2 (-9 to 5). The median difference reported as infiltration minus PECS for QoR-15 domains was pain 0 (-2 to 1), physical comfort -1 (-3 to 2), physical independence 0 (-2 to 1), psychological support 0 (0-0), and emotions 0 (-1 to 2) (P > .28). The BPI pain subscale at 24 hours (0-40, lower score indicates less pain), reported as median [quartiles], was 7 [2, 13] in the PECS group and 10 [5, 17] in the infiltration group (P = .15). The BPI global score at 24 hours, reported as median [quartiles], was 20 [7, 36] in the PECS group and 23 [10, 43] in the infiltration group (P = .34) and at 3 months was 0 [0, 14] and 0 [0, 11] (P = .85). CONCLUSIONS: After mostly minor surgery for breast cancer, PECS II block was not superior to local infiltration by the surgeon.

Impact of Local Infiltration Analgesia on the Quality of Recovery After Anterior Total Hip Arthroplasty: A Randomized, Triple-Blind, Placebo-Controlled Trial.

BACKGROUND: Local infiltration analgesia (LIA) is commonly used in anterior total hip arthroplasty (THA) surgery; however, evidence for its efficacy is lacking. We hypothesized that LIA with 0.2% ropivacaine when compared with injection of placebo (0.9% saline) would improve patient quality of recovery on postoperative day (POD) 1, as measured by the Quality of Recovery-15 (QoR-15) score. METHODS: Patients scheduled to have a primary unilateral anterior THA with a single surgeon in a tertiary level metropolitan hospital were randomized to receive LIA with either 2.5 mL/kg of 0.2% ropivacaine or 0.9% saline as placebo. Patients and clinical and study personnel were blinded to group allocation. Perioperative care was standardized and this included spinal anesthesia and oral multimodal analgesia. The primary outcome was a multidimensional (pain, physical comfort, physical independence, emotions, and psychological support) patient-reported quality of recovery scale, QoR-15, measured on POD 1. RESULTS: One hundred sixty patients were randomized; 6 patients were withdrawn after randomization and 2 patients had incomplete outcome data. The intention-to-treat analysis included 152 patients. The median (interquartile range [IQR]) QoR-15 score on POD 1 of the ropivacaine group was 119.5 (102-124), compared with the placebo group which had a median (IQR) of 115 (98-126). The median difference of 2 (95% confidence interval [CI], -4 to 7; P = .56) was not statistically or clinically significant. An as-per-protocol sensitivity analysis of 146 patients who received spinal anesthesia without general anesthesia, and the allocated intervention, also showed no evidence of a significant difference between groups. Secondary outcomes (worst pain numerical rating scale at rest and with movement on POD 1, opioid consumption on PODs 1 and 2, mobilization on POD 1, Brief Pain Inventory severity and interference on POD 90, and length of stay) were similar in both groups. CONCLUSIONS: LIA with 0.2% ropivacaine when compared with 0.9% saline as placebo did not improve quality of recovery 1 day after anterior THA.

Opioid use prior to elective surgery is strongly associated with persistent use following surgery: an analysis of 14 354 Medicare patients.

BACKGROUND: Persistent opioid use following total joint replacement (TJR) surgery is common; however, the association between pre-surgical opioid use and surgery type has not been established. The objective of this study was to determine the association between pre-surgery opioid use and persistent post-surgery opioid use in TJR patients compared to other elective surgical patients. METHODS: This is a retrospective cohort study, of univariate and multinomial logistic regression of linked, de-identified Medicare Benefits Schedule and Pharmaceutical Benefits Schedule data, adjusted for perioperative opioid use, age and sex. Oral morphine equivalents daily doses (OMEDD) were calculated and opioid use was categorized into three mutually exclusive categories for each observation window: low (0-5 OMEDD), moderate (5-10 OMEDD), high (10+ OMEDD). Persistent opioid use was defined as opioid use between 180 and 270 days after the date of surgery. RESULTS: Persistent opioid use was associated with older age, female gender and pre-surgery opioid use. There was no increased risk for persistent opioid use for TJR patients compared to other surgical patients. The intensity of pre-surgery opioid usage is strongly associated with persistent opioid use in all observed surgical patients. CONCLUSIONS: Our results suggest that many patients who use opioids prior to surgery will persist in their opioid use following surgery. No association was found between persistent opioid use and TJR surgery, but rather a risk reduction compared to other elective surgeries when associations with opioid use are controlled for. Primary care clinicians and surgeons should monitor the duration and dosage of perioperative opioid use.

Local Anesthetic Systemic Toxicity: A Narrative Literature Review and Clinical Update on Prevention, Diagnosis, and Management.

BACKGROUND: The objective of this narrative review of local anesthetic systemic toxicity is to provide an update on its prevention, diagnosis, and management. METHODS: The authors used a MEDLINE search of human studies, animal studies, and case reports and summarize findings following the American Society of Regional Anesthesia and Pain Medicine practice advisories on local anesthetic systemic toxicity. RESULTS: Between March of 2014 and November of 2016, there were 47 cases of systemic toxicity described. Twenty-two patients (47 percent) were treated with intravenous lipid emulsion and two patients (4.3 percent) died. Seizures were the most common presentation. The spectrum of presenting neurologic and cardiovascular symptoms and signs are broad and can be obscured by perioperative processes. Local anesthetic type, dosage, and volume; site of injection; and patient comorbidities influence the rate of absorption from the site of injection and biodegradation of local anesthetics. Consider discussing appropriate dosages as a component of the surgical "time-out." A large-volume depot of dilute local anesthetic can take hours before reaching peak plasma levels. Oxygenation, ventilation, and advanced cardiac life support are the first priorities in treatment. Lipid emulsion therapy should be given at the first sign of serious systemic toxicity with an initial bolus dose of 100 ml for adults weighing greater than 70 kg and 1.5 ml/kg for adults weighing less than 70 kg or for children. CONCLUSION: All physicians who administer local anesthetics should be educated regarding the nature of systemic toxicity and contemporary management algorithms that include lipid emulsion therapy.

Anaesthetic care of patients undergoing primary hip and knee arthroplasty: consensus recommendations from the International Consensus on Anaesthesia-Related Outcomes after Surgery group (ICAROS) based on a systematic review and meta-analysis.

BACKGROUND: Evidence-based international expert consensus regarding anaesthetic practice in hip/knee arthroplasty surgery is needed for improved healthcare outcomes. METHODS: The International Consensus on Anaesthesia-Related Outcomes after Surgery group (ICAROS) systematic review, including randomised controlled and observational studies comparing neuraxial to general anaesthesia regarding major complications, including mortality, cardiac, pulmonary, gastrointestinal, renal, genitourinary, thromboembolic, neurological, infectious, and bleeding complications. Medline, PubMed, Embase, and Cochrane Library including Cochrane Database of Systematic Reviews, Cochrane Central Register of Controlled Trials, NHS Economic Evaluation Database, from 1946 to May 17, 2018 were queried. Meta-analysis and Grading of Recommendations Assessment, Development and Evaluation approach was utilised to assess evidence quality and to develop recommendations. RESULTS: The analysis of 94 studies revealed that neuraxial anaesthesia was associated with lower odds or no difference in virtually all reported complications, except for urinary retention. Excerpt of complications for neuraxial vs general anaesthesia in hip/knee arthroplasty, respectively: mortality odds ratio (OR): 0.67, 95% confidence interval (CI): 0.57-0.80/OR: 0.83, 95% CI: 0.60-1.15; pulmonary OR: 0.65, 95% CI: 0.52-0.80/OR: 0.69, 95% CI: 0.58-0.81; acute renal failure OR: 0.69, 95% CI: 0.59-0.81/OR: 0.73, 95% CI: 0.65-0.82; deep venous thrombosis OR: 0.52, 95% CI: 0.42-0.65/OR: 0.77, 95% CI: 0.64-0.93; infections OR: 0.73, 95% CI: 0.67-0.79/OR: 0.80, 95% CI: 0.76-0.85; and blood transfusion OR: 0.85, 95% CI: 0.82-0.89/OR: 0.84, 95% CI: 0.82-0.87. CONCLUSIONS: Recommendation: primary neuraxial anaesthesia is preferred for knee arthroplasty, given several positive postoperative outcome benefits; evidence level: low, weak recommendation. RECOMMENDATION: neuraxial anaesthesia is recommended for hip arthroplasty given associated outcome benefits; evidence level: moderate-low, strong recommendation. Based on current evidence, the consensus group recommends neuraxial over general anaesthesia for hip/knee arthroplasty. TRIAL REGISTRY NUMBER: PROSPERO CRD42018099935.

Did ultrasound fulfill the promise of safety in regional anesthesia?

PURPOSE OF REVIEW: Ultrasound guidance has become the accepted standard of practice for peripheral regional anesthesia. Despite evidence supporting the efficacy of ultrasound-guided regional anesthesia, its impact on patient safety has been less clear. RECENT FINDINGS: Evidence has been consistent that ultrasound guidance reduces the incidence of vascular injury, local anesthetic systemic toxicity, pneumothorax and phrenic nerve block. Within the limited global scope of the epidemiology and etiologic complexity of perioperative (including block-related) peripheral nerve injury, there has not been consistent evidence that ultrasound guidance is associated with a reduced incidence of nerve injury. However, a recently published retrospective cohort study has demonstrated that the incidence of short-term nerve injury was decreased with ultrasound guidance compared with nerve stimulation. Ultrasound has led to development of novel blocks, approaches and refinement of existing ones, which may contribute to patient safety. SUMMARY: Ultrasound has revolutionized the way we approach regional anesthesia and contributed to patient safety. It is important to note that patient safety does not hinge on one single technology. Patient safety in regional anesthesia relies on a well trained practitioner to pay meticulous attention to indication, block and patient selection, anatomy, pharmacology, equipment and technique.

A Cadaveric Study Investigating the Mechanism of Action of Erector Spinae Blockade.

BACKGROUND AND OBJECTIVES: Erector spinae block is an ultrasound-guided interfascial plane block first described in 2016. The objectives of this cadaveric dye injection and dissection study were to simulate an erector spinae block to determine if dye would spread anteriorly to the involve origins of the ventral and dorsal branches of the spinal nerves. METHODS: In 10 unembalmed human cadavers, 20 mL of 0.25% methylene blue dye was injected bilaterally into the plane between the fifth thoracic transverse process and erector spinae muscle. An in-plane ultrasound-guided technique with the transducer orientated longitudinally was used. During dissection, superficial and deep muscles were identified, and extent of dye spread was documented in cephalocaudal and lateral directions. The ventral and dorsal rami of spinal nerves and dorsal root ganglion at each level were examined to determine if they were stained by dye. RESULTS: There was extensive cephalocaudad and lateral spread of dye deep and superficial to the erector spinae muscles. Except for 1 injection (from 20), the ventral rami were not stained by the dye. In only 2 injections did the dye track posteriorly through the costotransverse foramen to the dorsal root ganglion. In all other cases, the dorsal root ganglia were not involved in the dye injection. The dye stained the dorsal rami posterior to the costotransverse foramen. CONCLUSIONS: There was no spread of dye anteriorly to the paravertebral space to involve origins of the ventral and dorsal branches of the thoracic spinal nerves. Dorsal ramus involvement was posterior to the costotransverse foramen.