Hubert A. Benzon

Piriformis syndrome: anatomic considerations, a new injection technique, and a review of the literature.

Background Piriformis syndrome can be caused by anatomic abnormalities. The treatments of piriformis syndrome include the injection of steroid into the piriformis muscle and near the area of the sciatic nerve. These techniques use either fluoroscopy and muscle electromyography to identify the piriformis muscle or a nerve stimulator to stimulate the sciatic nerve. Methods The authors performed a cadaver study and noted anatomic variations of the piriformis muscle and sciatic nerve. To standardize their technique of injection, they also noted the distance from the lower border of the sacroiliac joint (SIJ) to the sciatic nerve. They retrospectively reviewed the charts of 19 patients who had received piriformis muscle injections, noting the site of needle insertion in terms of the distance from the lower border of the SIJ and the depth of needle insertion at which the motor response of the foot was elicited. The authors tabulated the response of the patients to the injection, any associated diagnoses, and previous treatments that these patients had before the injection. Finally, they reviewed the literature on piriformis syndrome, a rare cause of buttock pain and sciatica. Results In the cadavers, the distance from the lower border of the SIJ to the sciatic nerve was 2.9 ± 0.6 (1.8–3.7) cm laterally and 0.7 ± 0.7 (0.0–2.5) cm caudally. In 65 specimens, the sciatic nerve passed anterior and inferior to the piriformis. In one specimen, the muscle was bipartite and the two components of the sciatic nerve were separate, with the tibial nerve passing below the piriformis and the peroneal nerve passing between the two components of the muscle. In the patients who received the injections, the site of needle insertion was 1.5 ± 0.8 (0.4–3.0) cm lateral and 1.2 ± 0.6 (0.5–2.0) cm caudal to the lower border of the SIJ as seen on fluoroscopy. The needle was inserted at a depth of 9.2 ± 1.5 (7.5–13.0) cm to stimulate the sciatic nerve. Patients had comorbid etiologies including herniated disc, failed back surgery syndrome, spinal stenosis, facet syndrome, SIJ dysfunction, and complex regional pain syndrome. Sixteen of the 19 patients responded to the injection, their improvements ranged from a few hours to 3 months. Conclusions Anatomic abnormalities causing piriformis syndrome are rare. The technique used in the current study was successful in injecting the medications near the area of the sciatic nerve and into the piriformis muscle.

Comparison of the particle sizes of different steroids and the effect of dilution: a review of the relative neurotoxicities of the steroids.

Background:Central nervous system injuries after transforaminal epidural steroid injections have been ascribed to occlusion of the blood vessels supplying the spinal cord and brain by the particulate steroid. Methods:The authors compared the sizes of the particles of the steroids methylprednisolone acetate, triamcinolone acetonide, dexamethasone sodium phosphate, betamethasone sodium phosphate/betamethasone acetate (both Celestone Soluspan®; Schering-Plough, Kenilworth, NJ, the commercial betamethasone; and betamethasone repository, a betamethasone preparation that can be ordered from a compounding company), and betamethasone sodium phosphate. Both undiluted and diluted samples were examined. The samples were examined with a laser scanning confocal microscope, and images were analyzed and measured. The particles were categorized (or tabulated) into groups: 0-20, 21-50, 51-1000, and greater than 1000 &mgr;. Chi-square analyses, with Bonferroni correction, were used to compare the proportion of particles among the undiluted and diluted drug formulations. Results:Dexamethasone and betamethasone sodium phosphate were pure liquid. The proportion of larger particles was significantly greater in the methylprednisolone and the compounded betamethasone preparations compared with the commercial betamethasone. There was no statistical difference between the commercial betamethasone and triamcinolone, although betamethasone had a smaller percentage of the larger particles. Increased dilution of the compounded betamethasone with lidocaine decreased the percentage of the larger particles, whereas increased dilution of methylprednisolone 80 mg/ml with saline increased the proportion of larger particles. Conclusion:Commercial betamethasone is the recommended preparation if a nonsoluble steroid is preferred. Dexamethasone is a nonparticulate steroid, but its routine use awaits further studies on its safety and efficacy.

Factor VII levels and international normalized ratios in the early phase of warfarin therapy.

Background:Factor VII is the most affected clotting factor during the early phase of warfarin therapy. An international normalized ratio (INR) of more than 1.4 is considered unsafe for epidural catheter placement or removal, according to the American Society of Regional Anesthesia and Pain Medicine. The authors tested the hypothesis that factor VII activities would be consistent with safe removal of the epidural catheter on postoperative day (POD) 1 regardless of INR value. Methods:Data from 121 patients who took warfarin after undergoing total joint surgery and had INRs and factor VII levels determined were reviewed. Patient characteristics and factor VII activities were compared between patients with INRs of more than 1.4 and those with INRs less than or equal to 1.4 on PODs 1, 2, and 3. Results:Eleven patients had INRs of more than 1.4 on POD 1; their mean ± SD factor VII activities were 60 ± 28% (normal: 50–160%). On POD 2, 78 patients with INRs more than of 1.4 had factor VII activities of 32 ± 15%, whereas on POD 3, 84 patients with INRs of more than 1.4 had factor VII activities of 44 ± 19%. Variables included in the final multiple logistic regression model as predictors of an INR of more than 1.4 on POD 2 were warfarin dose on POD 1 and factor VII activity on POD 2. Conclusions:The range of factor VII activities in the patients with INRs of more than 1.4 within 12 h of warfarin therapy was compatible with adequate hemostasis. The authors found no evidence that epidural catheters should not be removed even with INRs up to 1.9, the highest INR on POD 1 noted in their study.

Determination of residual antiplatelet activity of clopidogrel before neuraxial injections

BACKGROUND Guidelines recommend discontinuation of clopidogrel for 7 days before a neuraxial injection, while other directives suggest that 5 days might be adequate. We examined the time course of antiplatelet activity after clopidogrel discontinuation in patients undergoing epidural injections. METHODS Thirteen patients were studied at baseline, 3, 5, and 7 days after discontinuation of clopidogrel. P(2)Y(12) determinations were performed using the VerifyNow(®) assay (Accumetrics, San Diego, CA, USA), and clot closure times with stimulation by collagen/epinephrine and collagen/adenosine diphosphate using the PFA-100(®) (Platelet Function Analyzer, Siemens Diagnostics, Deerfield, IL, USA). Repeated-measures ANOVA was used to evaluate P(2)Y(12) platelet reaction units, PFA-100 closure times, and per cent P(2)Y(12) inhibition values. Wilcoxons signed-rank test was used to compare the frequencies of ≥30%, 11-29%, and ≤10% platelet inhibition between the baseline and subsequent sampling points after discontinuation of clopidogrel. RESULTS On day 3 after clopidogrel discontinuation, two subjects had ≥30%, seven subjects had 11-29%, and four subjects had ≤10% platelet inhibition; the corresponding numbers were 0, 3, and 10 subjects on day 5 (P=0.04). There were no differences between the ≥30%, 11-29%, and <10% platelet inhibition groups between days 5 and 7 (0, 0, and 13 subjects, P=1.0). PFA-ADP closure times were normal throughout the study period except in one patient. CONCLUSIONS These findings support the recommendation that discontinuation of clopidogrel for 5 days allows >70% of platelet function and might be adequate before a neuraxial injection is performed.

Update on the 2012 guidelines for the management of pediatric traumatic brain injury – information for the anesthesiologist

Traumatic brain injury (TBI) is a significant contributor to death and disability in children. Considering the prevalence of pediatric TBI, it is important for the clinician to be aware of evidence‐based recommendations for the care of these patients. The first edition of the Guidelines for the Acute Medical Management of Severe Traumatic Brain Injury in Infants, Children, and Adolescents was published in 2003. The Guidelines were updated in 2012, with significant changes in the recommendations for hyperosmolar therapy, temperature control, hyperventilation, corticosteroids, glucose therapy, and seizure prophylaxis. Many of these interventions have implications in the perioperative period, and it is the responsibility of the anesthesiologist to be familiar with these guidelines.

Ultrasound-Assisted and Evoked Motor Response Stimulation of the Deep Peroneal Nerve

BACKGROUND: We performed an observational volunteer study to document an ultrasound-guided evoked motor response blockade of the deep peroneal nerve. METHODS: Sixteen volunteers had deep peroneal nerve blocks in each foot. After visualization of the artery and the deep peroneal nerve with an ultrasound, the nerve was stimulated with a nerve stimulator. Evoked motor responses and/or paresthesia were noted before injection of the local anesthetic. RESULTS: Any evoked motor response (extension of the toes or muscle contractions on the dorsum of the lateral aspect of the foot) or elicitation of paresthesia resulted in complete sensory blockade of the web between the big toe and second toe. CONCLUSIONS: Visualization of the deep peroneal nerve with ultrasound followed by elicitation of an evoked motor response, or paresthesia, predicts successful blockade of the deep peroneal nerve.

Prescription Patterns of Pain Medicine Physicians

Our study surveyed physician members of 3 American pain societies to determine prescription patterns and whether these practices reflect current expert opinion.

A randomized comparison of a modified intertendinous and classic posterior approach to popliteal sciatic nerve block.

INTRODUCTION: In this prospective randomized study, we compared a single-injection modified intertendinous (n = 55) with the classic posterior (n = 54) popliteal sciatic nerve block for patients undergoing ankle/foot surgery. METHODS: Nerve stimulator-guided blocks were performed 7–8 cm (classic posterior) or 12–14 cm (modified intertendinous) above the popliteal crease. Levobupivacaine 0.625% with epinephrine 1:300,000 (Chirocaine®, Purdue Pharma, Stamford, CT), was injected in 5 mL aliquots to a total volume of 0.4 mL/kg (range, 25–35 mL). The needle position was considered acceptable if an evoked motor response of plantar flexion, inversion, eversion or a dorsiflexion of the ipsilateral foot was elicited at ≤0.4 mA. Complete block was defined as pinprick anesthesia and motor paralysis of the foot within 60 min. RESULTS: The median distance from the popliteal crease to the modified intertendinous site was 14.0 cm (interquartile range, 13.5–15 cm) compared to 7.5 cm (interquartile range 7.0–8.0 cm) for the classic posterior site (P < 0.01). Complete block was achieved in 44 of 55 patients (81.5%) in the modified intertendinous compared to 39 of 54 patients (70.9%) in the classic posterior group (P = 0.26). Complete block frequency was greater with an evoked motor response of inversion 49 of 56 patients (87.5%) and plantar flexion 23 of 30 patients (76.7%) compared with dorsiflexion/eversion 11 of 23 patients (47.8%) (P = 0.001). The median (95% CI) time (min) to complete block with an evoked motor response of inversion was 10 (0–22 min) for the modified intertendinous compared to 30 (4–56 min) with the classic posterior approach (P = 0.04). CONCLUSIONS: Potential advantages of the modified intertendinous approach include more rapid onset of anesthesia with an evoked motor response of inversion compared to a classic posterior popliteal sciatic nerve block.

Relationship Between Ultrasound Imaging and Eliciting Motor Response During Femoral Nerve Stimulation

Objective. Nerve stimulator–assisted localization of the femoral nerve is well described; however, direct ultrasound imaging of the femoral nerve branches may be challenging. The purpose of this study was to correlate the evoked motor responses obtained by femoral nerve stimulation and the topographic orientation of the femoral nerve branches during ultrasound examinations of the infrainguinal region. Methods. Eighty‐two patients undergoing total knee replacement were enrolled in this study. A 25‐mm, 5‐ to 10‐MHz broadband linear array transducer was used to identify the femoral nerve at the inguinal crease. The medial and lateral aspects of the femoral nerve were stimulated under ultrasound imaging. Twenty cadavers were dissected to support our clinical findings. Results. A quadriceps contraction was elicited in 1.2% and 96% of the patients when stimulating the medial and lateral aspects of the femoral nerve, respectively. In contrast, a sartorius muscle contraction was elicited in 94% and 0% when stimulating the medial and lateral aspects of the femoral nerve. Our findings during anatomic dissection revealed that the femoral nerve branch to the quadriceps muscle, when compared with the branch to the sartorius muscle, originated laterally in 95% and medially in 5% of the specimens. Conclusions. When using out‐of‐plane ultrasound imaging at the inguinal crease, directing the stimulating needle to the lateral half of the femoral nerve may be associated with a higher probability of encountering the motor branch to the quadriceps muscle.

Perioperative Outcomes and Management in Pediatric Complex Cranial Vault Reconstruction: A Multicenter Study from the Pediatric Craniofacial Collaborative Group

Background: The Pediatric Craniofacial Collaborative Group established the Pediatric Craniofacial Surgery Perioperative Registry to elucidate practices and outcomes in children with craniosynostosis undergoing complex cranial vault reconstruction and inform quality improvement efforts. The aim of this study is to determine perioperative management, outcomes, and complications in children undergoing complex cranial vault reconstruction across North America and to delineate salient features of current practices. Methods: Thirty-one institutions contributed data from June 2012 to September 2015. Data extracted included demographics, perioperative management, length of stay, laboratory results, and blood management techniques employed. Complications and outlier events were described. Outcomes analyzed included total blood donor exposures, intraoperative and perioperative transfusion volumes, and length of stay outcomes. Results: One thousand two hundred twenty-three cases were analyzed: 935 children aged less than or equal to 24 months and 288 children aged more than 24 months. Ninety-five percent of children aged less than or equal to 24 months and 79% of children aged more than 24 months received at least one transfusion. There were no deaths. Notable complications included cardiac arrest, postoperative seizures, unplanned postoperative mechanical ventilation, large-volume transfusion, and unplanned second surgeries. Utilization of blood conservation techniques was highly variable. Conclusions: The authors present a comprehensive description of perioperative management, outcomes, and complications from a large group of North American children undergoing complex cranial vault reconstruction. Transfusion remains the rule for the vast majority of patients. The occurrence of numerous significant complications together with large variability in perioperative management and outcomes suggest targets for improvement.