A Comparison of BREAST-Q Scores between Prepectoral and Subpectoral Direct-to-Implant Breast Reconstruction.

BACKGROUND: Subpectoral breast implant placement has in recent history predominated in breast reconstruction, but there has been more recent adoption of prepectoral implant reconstruction. There has been limited study to date of patient-reported outcomes comparing the two techniques. METHODS: Patients who underwent direct-to-implant breast reconstruction between 2013 and 2018 were included in this retrospective cohort study. Eligible patients were asked to complete BREAST-Q domains comparing quality of life and satisfaction. Descriptive, t test, chi-square test, and multivariate linear regression analyses were performed to compare BREAST-Q scores. Significance was defined as p ≤ 0.05. RESULTS: There were 64 patients (114 breasts) who underwent prepectoral reconstruction and 37 patients (68 breasts) who underwent subpectoral reconstruction. Among the 101 women (182 breasts), there were no significant differences between BREAST-Q scores and implant position for the Satisfaction with Breasts domain (adjusted p = 0.819), Psychosocial Well-being domain (adjusted p = 0.206), or Physical Well-being Chest domain (adjusted p = 0.110). The subpectoral implant cohort was associated with higher scores, 53 versus 47, for the Sexual Well-being module (adjusted p = 0.001). CONCLUSIONS: Patients undergoing direct-to-implant breast reconstruction had comparable BREAST-Q satisfaction scores for most modules regardless of implant plane. The subpectoral implant cohort scored higher for sexual well-being.

Outcomes After Central Wedge Labiaplasty Performed Under General Versus Local Anesthesia.

PURPOSE: Interest in labiaplasty as a way to alter and improve genital appearance has been on the rise. Labiaplasty procedures can be performed in the office setting under local anesthesia. However, these procedures are often performed under general anesthesia for patient comfort and to facilitate the operative technique and to potentially improve outcomes. Outcomes after labiaplasty performed under general anesthesia as compared with that performed under local anesthesia in the office setting have not been well-defined. This article aimed to compare outcomes after central wedge labiaplasty performed under general anesthesia versus that performed under local anesthesia. METHODS: A retrospective chart review identified patients who underwent central wedge labiaplasty performed by a single surgeon from 2011 to 2019. Demographic, clinical, and operative information were reviewed and recorded. Outcomes were assessed by evaluating postoperative complications and the need for revision surgery. RESULTS: Thirty-two women with a mean age of 32.8 ± 11.2 years and a mean body mass index of 22.0 ± 3.5 kg/m2 underwent central wedge or extended central wedge labiaplasty during the study period. Ten (31.2%) labiaplasties were performed under local anesthesia in an office setting, and 22 (68.8%) were performed under general anesthesia. Demographic, clinical, and operative characteristics were comparable between labiaplasties performed under local anesthesia and those performed under general anesthesia. Postoperative asymmetry and wound dehiscence were the most common complications. Outcomes after labiaplasty performed under general anesthesia were comparable to those performed under local anesthesia, with regard to asymmetry (27.3% vs 10.0%; P = 0.387), dehiscence (27.3% vs 40.0%; P = 0.683), scarring (4.5% vs 0.0%; P = 1.000), and the need for revision surgery (31.8% vs 40.0%; P = 0.703), respectively. There were no cases of infection, hematoma, decreased sensation, or dyspareunia. CONCLUSIONS: Postoperative asymmetry and dehiscence were the most common complications after labiaplasty performed under general or local anesthesia. Outcomes after labiaplasty performed under general anesthesia were comparable to those performed under local anesthesia. Further studies are needed to assess outcomes after labiaplasty performed under general anesthesia versus that performed under local anesthesia.

The Impact of Premastectomy Versus Postmastectomy Radiation Therapy on Outcomes in Prepectoral Implant-Based Breast Reconstruction.

PURPOSE: Prepectoral implant-based breast reconstruction is being increasingly performed over subpectoral reconstruction because of the reduced invasiveness of the procedure, postoperative pain, and risk of animation deformity. Radiation therapy is a well-known risk factor for complications in implant-based breast reconstruction. The effect of premastectomy versus postmastectomy radiation therapy on outcomes after prepectoral breast reconstruction has not been well-defined. The purpose of this study was to compare the impact of premastectomy versus postmastectomy radiation therapy on outcomes after prepectoral breast reconstruction. METHODS: A retrospective chart review was performed on all patients who underwent prepectoral implant-based breast reconstruction with inferior dermal flap and acellular dermal matrix performed by a single surgeon from 2010 to 2019. Demographic, clinical and operative data were reviewed and recorded. Outcomes were assessed by comparing rates of capsular contracture, infection, seroma, hematoma, dehiscence, mastectomy skin flap necrosis, rippling, implant loss, local recurrence and metastatic disease, between patients receiving premastectomy and postmastectomy radiation therapy and nonradiated patients. RESULTS: Three hundred and sixty-nine patients (592 breasts) underwent prepectoral implant-based breast reconstruction. Twenty-six patients (28 breasts) received premastectomy radiation, 45 patients (71 breasts) received postmastectomy radiation, and 305 patients (493 breasts) did not receive radiation therapy. Patients with premastectomy radiation had higher rates of seroma (14.3% vs 0.2%), minor infection (10.7% vs 1.2%), implant loss (21.4% vs 3.4%) and local recurrence (7.1% vs 1.0%), compared with nonradiated patients (P < 0.05). Patients with postmastectomy radiation had higher rates of major infection (8.4% vs 2.4%), capsular contracture (19.7% vs 3.2%), implant loss (9.9% vs 3.4%), and local recurrence (5.6% vs 1.0%) when compared with nonradiated patients (P < 0.03). Outcomes after prepectoral breast reconstruction were comparable between premastectomy and postmastectomy radiation patients, respectively, with regard to major infection (7.1% vs 8.4%), dehiscence (3.6% vs 1.4%), major mastectomy skin flap necrosis (7.1% vs 2.8%), capsular contracture (10.7% vs 19.7%), implant loss (21.4% vs 9.9%), and local recurrence (7.1% vs 5.6%) (P ≥ 0.184). However, premastectomy radiation patients had a higher rate of seroma compared with postmastectomy radiation patients (14.3% vs 0%; P = 0.005). CONCLUSIONS: In prepectoral implant breast reconstruction, premastectomy and postmastectomy radiation therapy were associated with higher rates of infection and implant loss compared with nonradiated patients. Postmastectomy radiation was associated with a higher rate of capsular contracture compared with nonradiated patients, and a comparable rate of capsular contracture compared with premastectomy radiation therapy patients. Premastectomy radiation was associated with a higher rate of seroma compared with postmastectomy radiation and nonradiated patients.

Assessing Patient-Reported Outcomes After Female Cosmetic Genital Surgery.

PURPOSE: Patient-reported outcomes after female cosmetic genital surgery (FCGS) have been well documented; however, methods vary widely between studies and are often very detailed, time-consuming, and difficult to reproduce. The purpose of this study was to assess patient-reported outcomes after FCGS using a novel method and survey as well as to present the results of a pilot study aimed at validating this survey. METHODS: A retrospective chart review identified patients who underwent FCGS. Demographic, clinical, operative, and outcome characteristics were recorded. A novel survey, including 14 items administered by telephone interview, was developed and extrapolated from the BREAST-Q for augmentation mammaplasty, to assess patient-reported outcomes after FCGS with regard to satisfaction with outcome and physical, psychosocial, and sexual well-being. RESULTS: The survey response rate was 50.6% (39 patients). Over a mean time after surgery of 56 months, 14 complications occurred in 11 patients (28.2%), and 10 complications required revision surgery. Postoperative asymmetry and dehiscence were the most common complications. Despite the higher complication and revision surgery rates, 97.4% agreed that the surgery was a good experience and were satisfied with the results after surgery. In addition, patient-reported outcomes after FCGS showed significant improvement in physical well-being, psychosocial well-being, and sexual well-being (P < 0.001). CONCLUSIONS: This novel survey can be used to assess patient-reported outcomes after FCGS in an efficient approach. Despite the potential complications and need for revision surgery, the vast majority of patients who undergo FCGS feel that it is a good experience, are satisfied with the results after surgery, and show significant improvement in physical, psychosocial, and sexual well-being after surgery.

Dual-Plane Gluteal Myocutaneous Flap for Reconstruction of Ischial Tuberosity Pressure Wounds.

PURPOSE: Ischial tuberosity pressure wounds are the most common type of pressure wound and contribute to a large percentage of the total cost of surgical and nonsurgical management of pressure wounds. Gluteal myocutaneous and fascocutaneous flaps are well-documented methods of coverage for ischial pressure wounds. This study aimed to describe results using a novel dual-plane gluteal myocutaneous flap technique for reconstruction of ischial tuberosity pressure wounds. METHODS: A retrospective chart review was performed of all patients who underwent dual-plane gluteus maximus myocutaneous flap reconstruction for ischial tuberosity pressure wounds performed by a single surgeon from 2012 to 2018. Patient demographic, clinical, and operative characteristics were reviewed. Outcomes were assessed by analyzing complication rates including recurrence, need for revision surgery, dehiscence, necrosis, wound infection, seroma, and hematoma. RESULTS: Eight dual-plane gluteus maximus myocutaneous flaps were performed for reconstruction of ischial tuberosity pressure wounds in 7 male patients with a mean age of 49.1 ± 14.9 years (mean ± SD) and mean body mass index of 26.7 ± 6.4 kg/m. All patients were nonambulatory secondary to spinal cord injury or congenital neurological disease. Two patients (28.6%) were diabetic, and 1 patient (14.3%) was an active smoker. The mean defect size after debridement of ischial pressure wounds was 60.7 ± 29.4 cm. After a mean follow-up of 16.4 months, partial wound dehiscence occurred in 1 patient (14.3%) and was managed with local wound care only. Infection and recurrence occurred in another patient (14.3%) and required revision surgery. CONCLUSIONS: The dual-plane gluteal myocutaneous flap is an effective method for reconstruction of ischial tuberosity pressure wounds. Partially elevating the cutaneous layer off the gluteus maximus muscle allows for greater mobility and rotation of the muscle flap into the ischial pressure wound defect and closure of the flap and donor site with the cutaneous layer.

Outcomes, Techniques, and Risk Factors for Dehiscence in Central Wedge Labiaplasty.

PURPOSE: Outcomes after female cosmetic genital surgery (FCGS) performed by plastic surgeons working in a group practice setting have not been well documented. This article aimed to assess outcomes and to describe FCGS techniques used in a large group private plastic surgery practice. METHODS: A retrospective chart review identified patients who underwent FCGS from 2009 to 2018. Demographic, clinical, and operative information was reviewed and recorded. Outcomes were assessed by evaluating postoperative complications and the need for revision surgery. RESULTS: Seventy-seven women between the ages of 14 and 53 years underwent FCGS performed by 1 of 6 surgeons. Forty-five patients underwent central wedge excision for labia minora hypertrophy, whereas 32 patients underwent extended central wedge excision for labia minora and clitoral hood hypertrophy. Four patients underwent liposuction of the mons pubis as an additional procedure. Over a mean follow-up of 37.4 months, postoperative asymmetry/redundancy occurred in 12 patients, requiring revision in 10. Wound dehiscence occurred in 12 patients, requiring revision in 9. There was one hematoma postoperatively requiring evacuation, one case of dyspareunia, and one case of decreased sensation. A single-layer wound closure (P = 0.050) and mons liposuction (P = 0.011) were risk factors for wound dehiscence. CONCLUSIONS: Central wedge excision and extended central wedge excision labiaplasty were the techniques used in a large group plastic surgery practice. Postoperative asymmetry and dehiscence were the most common complications, and the revision surgery rate was high. A single-layer wound closure and additional mons liposuction were risk factors for dehiscence after central wedge labiaplasty.

Extra-articular Metacarpal Fractures: Closed Reduction and Percutaneous Pinning Versus Open Reduction and Internal Fixation.

BACKGROUND: There is no consensus on the optimal operative treatment of isolated closed metacarpal fractures as every technique is associated with advantages and shortcomings. This retrospective study aims to compare the outcomes of single metacarpal, extra-articular fractures treated with closed reduction and percutaneous pinning (CRPP) versus open reduction and internal fixation (ORIF). METHODS: The charts of all patients who underwent surgical repair of closed metacarpal fractures at our institutions from 2009 to 2016 were reviewed. 70 patients met the inclusion criteria, 44 had undergone CRPP and 26 ORIF with plate or lag screws. Subgroup analyses of all patients stratified by both fracture pattern and fracture location were performed. Additionally, subgroup analyses of outcomes based on the time from injury to surgery were conducted. Clinical outcomes included immobilization time, total active motion, stiffness, complication and reoperation rates, as well as occupational therapy referral rates and duration. Functional outcomes were determined using the Quick-DASH (Disabilities of the Arm, Shoulder and Hand) score via telephone questionnaire administered retrospectively. RESULTS: Overall, there was no significant difference in functional outcome parameters including total active motion (CRPP 91% of normal vs. ORIF 87% of normal), stiffness, therapy referrals, and complications between treatment groups. Patients treated with CRPP, regardless of fracture pattern or location, were operated on earlier than those treated with ORIF (avg. 7 days vs. 15 days). The immobilization time for patients treated with ORIF was significantly less than those treated with CRPP (19.7 vs. 30.7 days; p=0.001). This difference in the immobilization time also reflected the outcomes of the subgroup analyses based on the post-injury time of surgery. When transverse shaft fractures were examined independently as a subgroup, ORIF resulted in improved post-operative range of motion vs. CRPP (100% normal vs. 91% normal). The mean DASH score for each group was satisfactory and the difference was not statistically significant (16.3 for the CRPP and 18.7 for the ORIF group, p=0.805). CONCLUSION: Both CRPP and ORIF are viable techniques with good clinical outcomes and low complication rates. ORIF of closed metacarpal fractures allowed for earlier mobilization when compared with CRPP without compromising fracture stability, clinical or functional short-term outcomes.

Limberg flap reconstruction for sacrococcygeal pilonidal sinus disease with and without acute abscess: Our experience and a review of the literature.

BACKGROUND: The efficacy of Limberg flap reconstruction for pilonidal sinus with acute abscess remains unclear. This study aimed to compare outcomes after Limberg flap reconstruction for pilonidal sinus disease with and without acute abscess. A secondary objective was to perform a review of the literature on the topic. METHODS: A retrospective chart review was conducted of all patients who underwent excision and Limberg flap reconstruction for pilonidal sinus from 2009 to 2018. Patient demographics, wound characteristics, and complication rates were reviewed and analyzed. RESULTS: Group 1 comprised 19 patients who underwent Limberg flap reconstruction for pilonidal sinus disease without acute abscess and group 2 comprised four patients who underwent reconstruction for pilonidal sinus disease with acute abscess. The average defect size after excision was larger in group 2 than group 1 (107.7±60.3 cm2 vs. 61.4±33.8 cm2, respectively). There were no recurrences, seromas or cases of flap necrosis postoperatively. There was only one revision surgery needed for evacuation of a postoperative hematoma in group 1. There were comparable rates of partial wound dehiscence treated by local wound care, hematoma, need for revision surgery and minor infection between group 1 and group 2. CONCLUSIONS: Limberg flap reconstruction for pilonidal sinus in the setting of acute abscess is a viable option with outcomes comparable to that for disease without acute abscess. This practice will avoid the pain and cost associated with a prolonged local wound care regimen involved in drainage of the abscess prior to flap reconstruction.

The Double-reverse Wedge Excision Technique: A Novel Approach to Reconstruction of Stahl's Ear Deformity.

Stahl's ear deformity presents with an abnormal third crus of the antihelix and varying degrees of severity. This paper aims to describe a novel technique for reconstruction of Stahl's ear involving a double-reverse wedge excision of the third crus cartilage and skin, as well as use of Mustardé sutures to recreate the superior crus and Furnas sutures to complete the auricular setback. This novel technique for correction of Stahl's ear deformity produces a more stable aesthetic result versus classic otoplasty with desired auricular setback, minimal reduction in the size of the ear, and limited scarring on the anterior auricular surface. Reconstruction of Stahl's ear deformity can be accomplished using this double-reverse wedge excision technique of the third crus cartilage and skin with Mustardé and Furnas sutures to recreate the superior crus and complete auricular setback, effectively restoring anatomic harmony to the ear.

Impact of Postmastectomy Radiation Therapy in Prepectoral Versus Subpectoral Implant-Based Breast Reconstruction.

BACKGROUND: This study aimed to compare the impact of postmastectomy radiation therapy (PMRT) on outcomes after prepectoral versus subpectoral implant-based breast reconstruction with local deepithelialized dermal flap and acellular dermal matrix (ADM). METHODS: From 2010 to 2017, 274 patients (426 breasts) underwent prepectoral reconstruction. In this group, 241 patients (370 breasts) were not exposed to PMRT, whereas 45 patients (56 breasts) were exposed to PMRT. Of 100 patients (163 breasts) who underwent partial subpectoral reconstruction, 87 (140 breasts) were not exposed to PMRT, whereas 21 patients (23 breasts) were exposed. The outcomes were assessed by comparing complication rates between the pre- and subpectoral groups. RESULTS: A higher rate of capsular contracture was found for the prepectoral patients with PMRT than for those without PMRT (16.1 vs 3.5%; p = 0.0008) and for the subpectoral patients with PMRT than for those without PMRT (52.2 vs 2.9%; p = 0.0001). The contracture rate was three times higher for the subpectoral patients with PMRT than for the prepectoral patients with PMRT (52.2 vs 16.1%; p = 0.0018). In addition, 10 (83.3%) of 12 cases with capsular contracture in the subpectoral cohort that received PMRT were Baker grades 3 or 4 compared with only 2 (22.2%) of 9 cases of the prepectoral group with PMRT (p = 0.0092). CONCLUSIONS: The patients undergoing subpectoral breast reconstruction who received PMRT had a capsular contracture rate three times greater with more severe contractures (Baker grade 3 or 4) than the patients receiving PMRT who underwent prepectoral breast reconstruction.

Incidence of Cellulitis in Lower Extremity Burns: 6-Year Analysis.

INTRODUCTION: Patients with burn wounds of the lower extremities are at increased risk of developing cellulitis. The probability of developing burn-associated cellulitis is presumed to be correlated with a medical history of diabetes, the etiology of the burn, delay in hospitalization of the patient during their initial presentation, and depth of the burn itself. This study aims to identify factors that place patients at increased risk for developing lower extremity burn wound cellulitis. MATERIALS AND METHODS: A retrospective chart review was performed of all Nassau University Medical Center Burn Center admissions from January 2010 to January 2016. All patients admitted with burns of any etiology isolated to the lower extremity were included in this study. Patients who were evaluated and followed as an outpatient were not included in this study. Pediatric patients less than or equal to 12 years of age were excluded from this study. RESULTS: Of the 218 admissions for lower extremity burns during the 6-year study period, 34% of patients developed cellulitis. Risk factors for developing lower extremity burn wound cellulitis included being male, greater depth of burn, and burn-to-admission delay. This was true in both univariate and multivariate analysis. total body surface area was a risk factor on univariate analysis but was not found to be an independent risk factor on multivariate analysis. No difference was observed in the development of cellulitis in patients discharged on oral antibiotics compared with those not given antibiotics. CONCLUSIONS: Burn wound cellulitis is the second most common complication observed in burns. Identification of patients at risk for developing cellulitis is important. Admitting these patients at increased risk and excising and grafting the burned area is a reasonable solution in preventing this costly complication.

Levobupivacaine versus ropivacaine for sciatic nerve block in the rat.

BACKGROUND AND OBJECTIVES: Ropivacaine and levobupivacaine, both single S- enantiomers, are being promoted as safer alternatives to racemic bupivacaine. To determine whether levobupivacaine produces a more potent and longer lasting peripheral nerve block than ropivacaine, we compared functional blockade of sciatic nerve in the rat at several doses with these 2 agents. METHODS: Percutaneous sciatic nerve blocks were performed in 6 groups of rats (n = 8) with 0.1 mL of 0.0625%, 0.125%, and 0.25% of levobupivacaine or ropivacaine, with and without 1:200,000 epinephrine. In the 2 different hindlegs of the same 8 rats, we measured the degree and duration of deficit of 3 functions of peripheral nerve (proprioception, motor function, nociception) effected by the 2 respective drugs at the same concentration, using a blinded cross-over design. RESULTS: In general, both degree and duration of functional deficits produced by levobupivacaine were slightly greater than those from ropivacaine at the same dose. At the lowest concentration (0.0625%), no functions were completely blocked and the only significant difference was a longer motor impairment by levobupivacaine. At the highest concentration (0.25%), all formulations completely blocked the 3 functions, all of which lasted longer with levobupivacaine than ropivacaine. There were no significant differences in degree and duration of deficits between the 2 drugs at midconcentration (0.125%). The actions of both drugs were generally potentiated by epinephrine, but the rank order of potency was not altered. CONCLUSIONS: At the lowest concentration (0.0625%), levobupivacaine produces a greater degree of motor impairment and a longer duration of proprioceptive impairment relative to ropivacaine. At the middle concentration (0.125%), there no differences between the 2 drugs. At the higher concentration (0.25%), which is within the range used clinically for peripheral nerve block (0.25%-0.5%), levobupivacaine produces approximately a 30% longer duration of complete block in each modality compared with that by ropivacaine.

Multiple phases of relief from experimental mechanical allodynia by systemic lidocaine: responses to early and late infusions.

Systemic lidocaine can relieve various forms of neuropathic pain that develop after nerve injury. Mechanical allodynia, defined by a significant drop in paw withdrawal threshold force following spinal nerve ligation (L5-L6) in rats, can be reversed by one 30min lidocaine infusion at a constant plasma concentration as low as 1-2 microg/ml, an effect that is still present when the rats are tested days and weeks afterwards. In this study, we resolved the detailed time course of reversal of ipsilateral and contralateral allodynia in rats with spinal nerve ligation by a single systemic infusion of lidocaine, to 4 microg/ml, given either 2 days after ligation (POD2) or 7 days after ligation (POD7). Male Sprague-Dawley rats were examined for 21 days after undergoing sham operation or spinal nerve ligation to produce allodynia, which was quantified by a lower force of von Frey hairs at the plantar hind paw just required to produce paw withdrawal (paw withdrawal threshold, PWT). Six experimental protocols were followed: rats were infused with lidocaine on POD2 (L2) or on POD7 (L7), or with saline on POD2 (S2) or on POD7 (S7), and sham operated rats were infused with lidocaine on POD2 or on POD7. PWTs were measured during the last 5min of a single 30min lidocaine infusion; at 30, 60, 90, 120, 240 and 360min, and 24, 48 and 72h after beginning infusion, and then every 1-3 days up to 21 days. Three distinct sequential phases of ipsilateral relief were apparent in both L2 and L7 groups: (1) an acute elevation of PWT during the infusion, returning to the pre-infusion allodynic level within 30-60min after infusion; (2) a second, transient elevation of PWT within the next 360min; (3) a sustained elevation of PWT developing slowly over 24h after infusion and maintained over the next 21 days. A significant, although weaker contralateral allodynia developed more slowly (>POD8) than the ipsilateral condition, and could be delayed for more than 2 weeks by lidocaine infusion on POD2 but for only 1 week by the same treatment on POD7. None of the sham operated animals had any allodynic signs and no saline infusions elevated PWT in ligated, allodynic rats. These results of separate phases imply that there are mechanistic differences between the acute relief and the sustained relief of allodynia after a single infusion of lidocaine, and may present an experimental paradigm for investigating the advantages of earlier rather than late therapeutic intervention.

On the mechanism by which epinephrine potentiates lidocaine's peripheral nerve block.

BACKGROUND: Adding epinephrine to lidocaine solutions for peripheral nerve block potentiates and prolongs the action, but by incompletely understood mechanisms. In an effort to discriminate the pharmacokinetic from the pharmacodynamic effects of epinephrine, the authors measured the lidocaine content of peripheral nerve over the course of block produced by 0.5% lidocaine, with and without epinephrine, and correlated it with the degree of analgesia. METHODS: Percutaneous sciatic nerve blocks were performed in 18 groups of rats (10 in each) with 0.1 ml of either 0.5% lidocaine or 0.5% lidocaine with epinephrine (1:100,000). Over the full course of nerve block, the authors regularly measured analgesia to toe pinch and then rapidly removed nerves to assay intraneural lidocaine content at 2-120 min after injection. RESULTS: The kinetics of lidocaine's clearance from nerve was composed of a fast-decaying transient superimposed on a very slowly decaying component. The effect of epinephrine on the intraneural lidocaine content was to increase the amount of lidocaine in the slow-decaying component by threefold to fourfold, although the total neural content was not altered by epinephrine for the first 10 min after injection. Epinephrine prolonged blockade by almost fourfold and enhanced the intensity of peak analgesia, as well as the fraction of rats with complete block, almost throughout the 2-120-min period of behavioral observation. CONCLUSIONS: Adding epinephrine to lidocaine solutions increases the intensity and duration of sciatic nerve block in the rat. The early increase in intensity is not matched with an increase in intraneural lidocaine content at these early times, although the prolonged duration of block by epinephrine appears to correspond to an enlarged lidocaine content in nerve at later times, as if a very slowly emptying "effector compartment" received a larger share of the dose. The increase in early analgesia without increased lidocaine content may be explained by a pharmacodynamic action of epinephrine that transiently enhances lidocaine's potency, but also by a pharmacokinetic effect that alters the distribution of the same net content of lidocaine within the nerve.

Differential efficacy of intravenous lidocaine in alleviating ipsilateral versus contralateral neuropathic pain in the rat.

In the this study we have investigated the threshold plasma concentration of lidocaine for reversal of mechanical 'allodynia' in a neuropathic pain model in the rat, defined the concentration-dependent limits of that reversal and compared the acute reversal during intravenous drug infusion with the persistent relief of allodynia assayed 48 h later. Actions of i.v. lidocaine on ipsilateral and contralateral legs were also assessed. Forty rats were sorted into five groups (n = 7-10) and underwent spinal root (L5-6) ligation to produce allodynia, as quantified by a lower force of von Frey hairs at the plantar hindpaw required to elicit paw withdrawal (PWT, paw withdrawal threshold). During surgery, intravenous catheters were placed for programmed lidocaine infusion and in some animals arterial catheters were also inserted for assaying lidocaine blood levels. PWTs were measured in ipsilateral and contralateral paws before and after ligation and during infusions which, beginning at 5 days after surgery, were conducted every other day to incrementing levels (1.1-9.7 microg/ml plasma). Ligation produced allodynia in ipsilateral paws (PWT = 1.22 +/- 0.42 g (+/-SEM)) and in contralateral paws (PWT = 4.99 +/- 0.61 g), both markedly lower than pre-operative control values for either paw (11.31 +/- 0.41 g). The ipsilateral allodynia was partially, but significantly and permanently reversed (to PWT = 6-8 g) after a lidocaine infusion to 2.1 microg/ml in two separate groups (n = 7, 8). Lower concentrations resulted in elevation of PWT during infusion but no sustained relief. The elevation of PWT during infusion at this threshold level among individual animals was positively correlated with the relief measured 48 h later, but higher lidocaine concentrations infused in subsequent dosings could exact no further sustained relief. The residual PWT level, after reversal by threshold lidocaine and greater, was constant for each individual rat tested over the next 14 days but varied substantially among individuals; some were restored to pre-operative PWTs and some were totally unresponsive to drug. Retrospective analysis revealed a significant and unanticipated correlation between the incidence of low pre-operative PWTs (< 10 g) and a lack of sustained reversal of post-operative allodynia by lidocaine. Contralateral allodynia, despite its acute reversal during infusion to 2.1 microg/ml and higher, was not persistently relieved after infusion of lidocaine to any concentration. Repeated infusions to subthreshold levels (<2 microg/ml) did not provide persisting relief of allodynia on either side, and infusions of saline were impotent. These findings show that experimental allodynia results from multiple factors, only some of which are sensitive to lidocaine treatment, and that prolonged reversal of allodynia is limited in extent and likely influenced by pre-existing factors.