Anterior "3-in-1" blockade: partial, total or overdimensioned block? Correlation between anatomy, clinic and radio images

Abstracts

JUSTIFICATIVA E OBJETIVOS: O clássico bloqueio "3 em 1" por via anterior tem suscitado divergências quanto ao envolvimento anestésico de seus três nervos participantes, o femoral, o cutâneo lateral da coxa e o obturador. O objetivo deste estudo é verificar o desfecho do bloqueio "3 em 1" por via anterior, através das técnicas: injeção única (G1), cateteres curtos (G2) e cateteres longos (G3). Os bloqueios "3 em 1", clinicamente identificados como completos ou superdimensionados foram, adicionalmente, investigados por meio de rádio imagem. MÉTODO: A identificação do espaço subfascial ilíaco nos bloqueios "3 em 1" com injeção única ou com cateteres foi feita pela perda de resistência ao ar. Em vários eventos dolorosos, o volume anestésico administrado variou entre 30 e 40 ml e a introdução cranial dos cateteres foi até 18 cm no espaço subfascial ilíaco. Quando a pesquisa clínica apontava envolvimento do nervo obturador ou de outro nervo adicional ao bloqueio "3 em 1", complementava-se a investigação com estudo radiográfico e tomodensiométrico com o propósito de estabelecer correspondência com a anatomia pélvica. RESULTADOS: O envolvimento dos nervos fêmoro cutâneo lateral e obturador não foram constantes, ao contrário do nervo femoral. No estudo, nenhum bloqueio "3 em 1" completo com injeção única (G1) se manifestou, e sim um bloqueio "2 em 1", com a participação eventual do ramo femoral do nervo genitofemoral (bloqueio "2,5 em 1"). Contudo, quando foram utilizados cateteres curtos (G2), obteve-se bloqueio "3 em 1" em apenas um paciente, ao passo que com cateteres longos (G3) introduzidos no sentido cefálico até 18 cm no espaço subfascial ilíaco, três bloqueios "3 em 1" superdimensionados foram registrados, pelo envolvimento adicional dos nervos fibular comum em dois pacientes e o nervo tibial em um paciente. CONCLUSÕES: Apesar da pequena amostra, com injeção única (G1), sempre se obteve um bloqueio "2 em 1" ou "2,5 em 1", sem a participação do nervo obturador. Com cateter curto (G2), o bloqueio "3 em 1" foi classificado como completo em 6,6% dos casos (um paciente). Porém, com cateter longo (G3), o resultado tende a ser mais previsível em relação aos outros grupos, especialmente quando o cateter alcança o espaço paravertebral lombossacral, resultando num bloqueio "3 em 1" completo em 20% dos casos (três pacientes) ou, raramente, num bloqueio "3 em 1" superdimensionado em 13,2% dos casos (dois pacientes).

TÉCNICAS ANESTÉSICAS; TÉCNICAS ANESTÉSICAS

MISCELLANEOUS

Anterior "3-in-1" blockade: partial, total or overdimensioned block? Correlation between anatomy, clinic and radio images^*

Bloqueo "3 en 1" por vía anterior: bloqueo parcial, completo o superdimensionado? Correlación entre anatomía, clínica y radio imágenes

Karl Otto Geier, M.D.

Anestesiologista do Hospital Municipal de Pronto Socorro de Porto Alegre/RS; Anestesiologista Colaborador da Clindor do Hospital São Lucas da PUC/RS; Mestre em Cirurgia pela UFRGS

^{Correspondence}

SUMMARY

BACKGROUND AND OBJECTIVES: Classic anterior 3-in-1 blockade has been questioned as to the anesthetic involvement of its three participant nerves: femoral, lateral cutaneous of thigh and obturator. This study aimed at evaluating the outcome of anterior 3-in-1 blockade through: single injection (G1), short catheters (G2) and long catheters (G3). 3-in-1 blockades identified as total or overdimensioned were additionally investigated by radio images.

METHODS: The identification of iliac subfascial space in 3-in-1 blockades with single injection or catheters has been made by loss of resistance to air. In several painful events, anesthetic volume has varied 30 to 40 mL and cranial catheters introduction was up to 18 cm in the iliac subfascial space. When clinical research would point to the involvement of the obturator nerve or other nerve additional to 3-in-1 blockade, investigation was complemented by radiographic or TC-Scan studies aiming at establishing correspondence with pelvic anatomy.

RESULTS: The involvement of lateral cutaneous of thigh and obturator nerves has not been constant, as opposed to the femoral nerve. No total 3-in-1 blockade with single injection (G1) was observed in our study, but rather 2-in-1, with eventual participation of the femoral branch of the genitofemoral nerve (2.5-in-1 blockade). However, when short catheters were used (G2), there has been 3-in-1 blockade in just one patient, while with long catheters (G3) introduced in the cephalad direction until 18 cm in the iliac subfascial space, three overdimensioned 3-in-1 blockades were recorded, with the additional involvement of common fibular nerve in two patients and tibial nerve in one patient.

CONCLUSIONS: In spite of the small sample size, single injection (G1) has always provided 2-in-1 or 2.5-in-1 blockade without the participation of the obturator nerve. With short catheters (G2) 3-in-1 blockade was classified as total in 6.6% of cases (one patient). With long catheters (G3), however, results seem to be more predictable as compared to the other groups, especially when the catheter reaches the lumbosacral paravertebral space, resulting in total 3-in-1 blockade in 20% of cases (3 patients) or more uncommonly, in overdimensioned 3-in-1 blockade in 13.2% of cases (2 patients).

Key Words: ANESTHETIC TECHNIQUES, Regional: 3-in-1 block

RESUMEN

JUSTIFICATIVA Y OBJETIVOS: El clásico bloqueo "3 en 1" por vía anterior ha suscitado divergencias cuanto al envolvimiento anestésico de sus tres participantes, el nervio femoral, el nervio cutáneo lateral del muslo y el nervio obturador. El objetivo de este estudio es verificar el resultado del bloqueo "3 en 1" por vía anterior, a través de las técnicas: inyección única (G1), catéteres cortos (G2) y catéteres largos (G3). Los bloqueos "3 en 1", clínicamente identificados como completos o superdimensionados fueron, adicionalmente, investigados por medio de radio imagen.

MÉTODO: La identificación del espacio subfascial ilíaco en los bloqueos "3 en 1" con inyección única o con catéteres fue hecha por la pérdida de resistencia al aire. En varios eventos dolorosos, el volumen anestésico administrado varió entre 30 y 40 ml y la introducción cranial de los catéteres fue hasta 18 cm en el espacio subfascial ilíaco. Cuando la pesquisa clínica apuntaba envolvimiento del nervio obturador o de otro nervio adicional al bloqueo "3 en 1", se complementava la investigación con estudio radiográfico y tomodensiométrico con el propósito de establecer correspondencia con la anatomía pélvica.

RESULTADOS: El envolvimiento de los nervios femoro cutáneo lateral y obturador no fueron constantes, al contrario del nervio femoral. En el estudio, ningún bloqueo "3 en 1" completo con inyección única (G1) se manifestó, y si un bloqueo "2 en 1", con la participación eventual del nervio genitofemoral (bloqueo "2,5 en 1"), uno de los ramos del nervio femoral. Todavía, cuando fueron utilizados catéteres cortos (G2), se obteve bloqueo "3 en 1" en apenas un paciente, al paso que con catéteres largos (G3) introducidos en el sentido cefálico até 18 cm en el espacio subfascial ilíaco, tres bloqueos "3 en 1" superdimensionados fueron registrados, por el envolvimiento adicional de los nervios fibular común en dos pacientes y el nervio tibial en un paciente.

CONCLUSIONES: A pesar de la pequeña muestra, con inyección única (G1), siempre se obtuvo un bloqueo "2 en 1" ó "2,5 en 1", sin la participación del nervio obturador. Con catéter corto (G2), el bloqueo "3 en 1" fue clasificado como completo en 6,6% de los casos (un paciente). Mas, con catéter largo (G3), el resultado tiende a ser más previsible en relación a los otros grupos, especialmente cuando el catéter alcanza el espacio paravertebral lombosacral, resultando en un bloqueo "3 en 1" completo en 20% de los casos (tres pacientes) o, raramente, en un bloqueo "3 en 1" superdimensionado en 13,2% de los casos (dos pacientes).

INTRODUCTION

Anterior 3-in-1 blockade, originally presented by Winnie et al. in 1973¹, aimed at simultaneously anesthetizing with a single injection femoral, femoral lateral cutaneous of thigh and obturator nerves, components of the lumbar plexus, by accessing paravascular femoral space right below the inguinal ligament. Technique would involve the triggering of paresthesias with needle on the crural nerve, followed by 20 or more mL of anesthetic solution injection. It was recommended to press tissues immediately distal to the needle aiming at favoring anesthetic solution spread in the iliac subfascial space during injection. Initially results were successful¹, with total 3-in-1 blockade. However, as the technique has become popular, it has been observed in the clinical practice that the involvement of the three nerves after single injection was not always true. Several publications have shown that the obturator nerve² would fail more frequently than the lateral cutaneous of thigh³, as opposed to the femoral nerve⁴, characterizing a partial 3-in-1 block or 2-in-1 block. However, very uncommon ipsilateral and overdimensioned 3-in-1 blocks have been reported^5,6. Oriented by superficial anatomic references suggested by Vloka et al.⁷, it has been observed in 45 consecutive 3-in-1 blockades with single injection or catheters, the partial and ipsilateral involvement of the lumbar plexus. Clinical outcomes identifying total or overdimensioned 3-in-1 blockades face to the additional involvement of lumbosacral nerves were correlated to the anatomy and to a corresponding radio image study.

METHODS

After the Hospital Ethics Committee and patients' approval, forty five 3-in-1 blockades were induced through paravascular femoral approach in three groups of 15 patients, with glass or plastic syringes adequate for loss of resistance to air test, disposable sharp tip needles, short catheters with terminal hole and long catheters with three lateral holes:

Group 1 - fifteen 3-in1- blockades performed with single injection and disposable 35 x 7 or 40 x 7 needle coupled to a special syringe for loss of resistance to air test. The needle-syringe set was introduced in 35º to 45º angle with relation to skin until the iliac subfascial space, using 1.5% lidocaine with 1:300,000 epinephrine (30 to 40 mL).

Group 2 - fifteen patients submitted to 3-in-1 blockades with 18G short venous catheters, being six B. Braun's 45 mm length Introcan^® and nine Nipro Medical Ltda's 50 mm length catheters, both with Quincke tip, introduced in acute angle similar to group 1. At iliac subfascial space identification, equivalent to the second loss of resistance, half anesthetic volume was injected, venous catheter needle was immobilized and catheter was cranially introduced throughout its extension, by clock and counterclock rotation movements along the needle's axis, followed by venous catheter needle removal. Anesthetic volume injected would help catheters introduction. It has been administered 0.25% bupivacaine with 1:400,000 epinephrine (30 to 40 mL).

Group 3 - 3-in-1 blockades were performed with long 18G epidural catheters, being nine B. Braun's Perifix^® and six Portex's Minipak^®. All catheters were cranially introduced 15 to 18 cm in the iliac subfascial space. Perifix^® catheters through their guide catheter, without peripheral nerve stimulator help, and Minipak^® catheters through the cannula of an 18G venous catheter, all previously introduced as described for group 2. An antibacterial filter was coupled to all catheters, anesthetic solution has been 0.25% bupivacaine with 1:400,000 epinephrine (40 mL).

Sensory and motor evaluation of 3-in-1 block was achieved by dermatomes (cutaneous innervation) or miotomes (muscle innervation) analgesia in burns and wounds, all with surgical indication, and sclerotomes (bone innervation) in thigh trauma patients with fractured of the femur medium third and knee. When skin, muscle and bone sensory investigation was impossible due to bandages or immobilization, pain relief itself has been the effective referential for 3-in-1 blockade. For elective surgeries under analgesia through catheters extending to the postoperative period, dermatomes sensitivity evaluation has followed the sequence: pain (hair follicles traction/needle pinprick), temperature (ice) and touch, followed by miotomes motility as already described⁸, provided they were compatible with the injury. All clinical investigations were compared to the homologous side.

Anatomic evaluation was coupled to radiological evaluation, the latter performed in blockades with short or long catheters (epidural and Contiplex^®), and resulted in clinical involvement of the classic three nerves and one additional nerve. Initially, 1 to 2 mL contrast would identify the catheter in the iliac subfascial space and then a higher volume of contrast (Omnipaque^® 300 mg/mL) diluted with local anesthetic would record spread in the possible three lumbopelvic radiological zones: zone A (medial pelvic), zone B (lateral pelvic) and zone C (paravertebral)⁵ (Figure 1). If radiological investigation overlapped the anatomic pathway of interested nerves, a CT-scan study was performed.

Brazilian Journal of Anesthesiology, 2004; 54: 4: 560 - 572

Anterior “3-in-1” blockade: partial, total or overdimensioned block?

Correlation between anatomy, clinic and radio images

Karl Otto Geier

Statistical Analysis

Demographics data are shown in mean ± SD. For categorical variables of three groups results are in relative frequencies, followed by chi-square test to determine significance of results, considering significant p < 0.05.

RESULTS

Demographics data and procedures for the three groups are shown in table I and ^II.

Brazilian Journal of Anesthesiology, 2004; 54: 4: 560 - 572

Anterior “3-in-1” blockade: partial, total or overdimensioned block?

Correlation between anatomy, clinic and radio images

Karl Otto Geier

Brazilian Journal of Anesthesiology, 2004; 54: 4: 560 - 572

Anterior “3-in-1” blockade: partial, total or overdimensioned block?

Correlation between anatomy, clinic and radio images

Karl Otto Geier

Femoral dermatome (mixed nerve) involvement was frequent, with femoral quadriceps muscle weakness, and almost as frequently there has been loss of lateral cutaneous of thigh dermatome (sensory nerve) sensitivity. In some cases, there has been loss of sensitivity on the medial face of almost the whole thigh where femoral and obturator dermatomes are overlapped with imprecise limits, however not always followed by adductor muscle paresis. Depending on lower limb morbidity, active (thigh bending - femoral nerve, and thigh adduction - obturator nerve) and passive (maintain bent knee with plantar region supported on bed, without pending the limb laterally - obturator nerve) motility were also evaluated as previously described⁸. Analgesia and anesthesia of additional dermatomes to the three classic 3-in-1 blockade nerves were observed in the territories of the femoral branch of genitofemoral nerve in 7 patients (46.6%) and in the common fibular nerve territory in 2 patients (13.2%), characterizing overdimensioned 3.5-in-1 block. One patient had additional partial tibial nerve involvement (6.6%), practically becoming a 4-in-1 blockade (Table III).

Brazilian Journal of Anesthesiology, 2004; 54: 4: 560 - 572

Anterior “3-in-1” blockade: partial, total or overdimensioned block?

Correlation between anatomy, clinic and radio images

Karl Otto Geier

Notwithstanding the 15 so-called 3-in-1 blockades with single injection have not resulted in obturator nerve motor involvement, such blockades were considered 2-in-1, so no radiological study was performed with the repetition of the same local anesthetic volume and mass. However, the 30 patients with short catheters (15) and long catheters (15) installed in the subfascial space of pelvic-lumbar muscles, who have clinically manifested loss of sensitivity in ectopic dermatome(s) to 3-in-1 blockade, were initially investigated by antero-posterior X-rays with 1 to 2 mL contrast to identify catheter positioning (Figure 2).

Brazilian Journal of Anesthesiology, 2004; 54: 4: 560 - 572

Anterior “3-in-1” blockade: partial, total or overdimensioned block?

Correlation between anatomy, clinic and radio images

Karl Otto Geier

Among patients with short catheters, only one has developed total 3-in-1 blockade (true) with changes in sensitivity of one extra dermatome to the three classic 3-in-1 blockade nerves. Contrasted X-ray images have identified pelvic radiological zones A (psoas muscle subfascial space) and B (iliac muscle subfascial space), however without medial ascending by zone A. Contrast has never reached zone C (paravertebral region). On the other hand, for being long catheters aimed at a more cranial introduction between 15 and 18 cm in the iliac subfascial space, they have not shown clinical manifestations suggesting cranial ascension to radiological zone C with obturator nerve anesthesia. The trend to coiling and bending during introduction of these catheters does not allow their introduction to the lumbar paravertebral region, where the three nerves are confined, what explains the lack of obturator nerve blockade.

From 15 long catheter patients, two had catheter positioned at L₅-L₄ (Figure 3) in a frequency of 13.2%. CT-scans of these patients have shown contrast in radiological zones A, B, C (Figure 4 and 5) with the involvement of additional dermatomes to those of 3-in-1 blockade.

Brazilian Journal of Anesthesiology, 2004; 54: 4: 560 - 572

Anterior “3-in-1” blockade: partial, total or overdimensioned block?

Correlation between anatomy, clinic and radio images

Karl Otto Geier

Brazilian Journal of Anesthesiology, 2004; 54: 4: 560 - 572

Anterior “3-in-1” blockade: partial, total or overdimensioned block?

Correlation between anatomy, clinic and radio images

Karl Otto Geier

Brazilian Journal of Anesthesiology, 2004; 54: 4: 560 - 572

Anterior “3-in-1” blockade: partial, total or overdimensioned block?

Correlation between anatomy, clinic and radio images

Karl Otto Geier

This was observed in a patient with traumatic avulsion of foot dorsum skin and submitted to grafting and in whom 3-in-1 blockade aimed at intermittent postoperative analgesia of the antero-lateral of thigh donor area. For our surprise, in addition to being effective for the donor area, patient has referred loss of tactile/painful sensitivity on the whole lateral face of leg and foot dorsum, corresponding to common fibular nerve dermatome (L₄-L₅-S₁-S₂), followed by sensation of foot increased volume and temperature, characteristic of sympathetic block. This same patient was unable to cross the lower target limb over its homologous due to intense motor block of adductor muscles (obturator nerve), although mildly bending foot and toes (posterior tibial nerve) as opposed to the other foot. Loss of sensitivity in the plantar medial face was confirmed in this patient, corresponding to tibial nerve dermatome. CT images (Figure 4 and 5) have shown diffusion to sacral zones C and A (S₂) (Figure 5).

DISCUSSION

Anatomically, lower limb innervation is made up of lumbar plexus [(T₁₂)-L₁-L₅)] and sacral plexus (L₄-S₃)^9,10. The union of these two plexuses is mediated by lumbosacral trunk (L₄-L₅). Femoral (L₂-L₄) and obturator (L₂-L₄) dermatomes, the latter predominantly motor (through L₃ and L₄ roots), overlap in the internal face of thigh without precise limits¹¹ or with more proximal distribution¹² than distal, or even absent¹³. According to Bouaziz et al.¹⁴ obturator's dermatome is absent in almost 60% of cases. The issue gets more important in one Gray's book edition⁹ where the author does not mention obturator dermatome. Confusion between obturator and femoral dermatome still persists¹⁵. Femoral and lateral cutaneous of thigh nerves are located more laterally between iliac and psoas muscles and the iliac fascia involving them¹⁶. While distal iliac fascia delimits paravascular femoral space in the inguinal region, obturator nerve by going from its origin to the lower limb, is more posterior, outside this space and medially to great psoas muscle¹⁷, making difficult its approach by single injection, differently from when anesthetic solution is released by the tip of a catheter positioned in the radiological zone A, or even posteriorly where the anesthetic is deposited directly in radiological zone C. The obturator nerve follows its caudal pathway not always following femoral and lateral cutaneous of thigh nerves. At L₄-L₅, while the former runs, at variable frequencies, outside or peripherally between the two parts of great psoas muscle, both covered by a thin fascia^17,18, the two latter have a more constant relationship between them within the muscular mass¹⁹, separating at the sacral promontory (L₅-S₁). The obturator nerve goes to the pelvis minor and the other two to the pelvis major. At the foramen receiving its name, the obturator nerve is divided in two branches: anterior or superficial branch and posterior or deep branch. Anterior or superficial branch is directed to hip joint and medial cutaneous surface of the leg, which in anastomosing with the internal saphenous nerve and multiple medial cutaneous branches of the femoral nerve, make up the subsartorial plexus, whose sensory cutaneous projection generate confusions on sensory tests of their corresponding dermatomes. In the medial third of the thigh, the anterior or superficial branch, predominantly sensory, goes toward superficial tissues with poor motor participation on long adductor, gracillis and short adductor muscles¹¹. Deep or posterior branch, predominantly motor, goes toward external obturator, adductor magum and short adductor muscles anastomosing with the superficial branch and projecting to the posterior face of the popliteal region and sinovial membrane of the knee. Most 3-in-1 block clinical observations only check sensory involvement and not motor involvement of the obturator nerve leading to misinterpretations about its extension²⁰. Objective and well-defined criteria²¹ should then orient clinical research of all and any anesthetic block, checking sensory and motor abolishment, respectively, of superficial (cutaneous) and deep (muscles, joints, viscera and veins) tissues.

Technical evidences of 3-in-1 blockade results confirm that, for the identification of the paravascular femoral space it is not always necessary to use peripheral nerve stimulator²¹ or paresthesias¹ through needle contact with the nerve. Loss of resistance is an adequate method for identification of virtual spaces^21-23 between tissues of different densities in several peripheral blocks²⁴.

Different contrasted radiological imaging modalities for regional anesthesia are becoming important, intensively impacting the learning of regional anesthetic techniques¹⁶ for diagnosing and treating painful diseases²⁵. In spite of unidimensional images, contrasted antero-posterior radiological evidences of the three radiographic zones⁵ should be interpreted based on contrast spread in the subfascial compartment of iliac and greater psoas muscles, through which nervous components of 3-in-1 blockade travel.

Obturator nerve distally crosses zone A (medial pelvic region), femoral nerve travels distally between zone A and internal zone B limit (lateral pelvic region) and lateral cutaneous of thigh nerve goes distally to zone A. Zone C (lumbar paravertebral region) corresponds to the proximal half of the psoas muscle⁵ (Figure 1), where with a single posterior injection is more feasible to anesthetize all three nerves involved in 3-in-1 blockade²⁶, as compared to the anterior approach. In a 3-in-1 blockade with long catheters, contrasted images are in general long, spindle-like and well delimited, almost always ending laterally to vertebral bodies L₃-L₄ at the level of intervertebral discs, corresponding to the fourth or fifth more caudal fascicles of the psoas muscle. It is possible that during catheter introduction 15 to 18 cm, catheterization privileges the anatomic origin of these muscle fascicles as shown in figures 2 and 3, and similar to images obtained by Dupré²⁷, Gaertner et al.²⁸ and Capdevila et al.²⁹ although the large psoas muscle mass has been also documented³⁰. In this case, it is to be assumed that larger anesthetic volumes would break the thin fascicle muscle fascia resulting in a global image the thickness of the psoas muscle, partially or totally delimiting it⁸.

Tridimensional CT-scan evidences (Figures 4 and 5) have documented in transverse axial planes that contrast spread by long catheter tip to zones A, B and C (Figure 1), have coincided with patients' clinical manifestations, although the same result has been obtained when contrast was alternatively lodged in radiological zones A and C (Figures 4 and 5). Contrast deposition close to neighbor bone, muscle and vascular structures^18,19 is valuable in the tomographic study because as a function of the anatomic pathway of lumbosacral plexus, it allows us to interpret the results of 3-in-1 blockades. With long catheter (B.Braun's Contiplex^®, 18G, 40 cm length) or 18G epidural catheter, results were a little different. Because catheters are cranially introduced 15 to 18 cm in the iliac subfascial space, coiling and/or bending may occur, preventing the intentional progression to the lumbar paravertebral region. Our study, however, has observed that two out of 15 long catheters (13.2%) introduced without guide, were lodged in zone C (paravertebral) (Figure 2) being in conformity not only with the paralumbar opaque format of psoas muscles at L₅-L₄ as shown^15,27-29 but also with frequency between 11.76%³¹ and 22%³² of catheters reaching this region. Catheters introduced with metallic guides³³ by Seldinger's³⁴ technique have determined a final positioning more programmed and reliable than randomized, translating into more predictable 3-in-1 blockade results. However, advancing the catheter too much may result in epidural block³⁵, being the opposite also true, as it has been recently published³⁶.

From patients observed in this small sample, two had lumbar roots and lumbosacral trunk (L₄-L₅) involvement. Lumbar and sacral plexuses representatives originate the sciatic nerve (L₄-S₃) made up of common fibular nerve (L₄-S₂) and tibial nerve (L₄-S₃), physically separated but involved by a common sheath³⁷. It seems that physical catheter characteristics (Teflon^® semi-rigid) favor its progression through the iliac subfascial compartment. In these patients, additional radiographic (Figure 1) and tomographic (Figures 4 and 5) images have recorded the radiological correlation between clinical results and corresponding pelvic anatomy.

Similar to other publications, it has been observed that with single 30 to 40 mL anesthetic solution injection, surprising results of other studies have not been observed^38,39 because 1) anesthetic spread does not sufficiently ascend; 2) femoral nerve is always involved because anesthetic solution is injected in its pathway; 3) lateral cutaneous femoral nerve is reached in a slightly lower incidence as compared to the femoral nerve because anesthetic spread is preferably diffused to the lateral pelvic face as compared to the medial face, and 4) obturator nerve is difficult or even impossible to be anesthetized because it is more posteriorly located in its difficult to access sealed fascial component. In addition, when sensory changes were observed in the dermatome of the medial face of the whole thigh, which is a territory innervated by femoral nerve cutaneous branches¹², passive motility (maintaining the knee bent on the table without pending laterally)⁸ and active motility of adductor muscles (thigh adduction)⁸ were preserved. Results of our study have coincided with recently published data on the isolated involvement of anterior obturator nerve branch^40,41. Winnie et al.¹ study has enriched regional anesthetic armamentarium. The increasing preference for postoperative analgesia via 3-in-1 blockade in thigh surgeries (skin grafting), fractures/osteotomies of femoral medium third and especially of the knee (anterior cruciate ligament and total knee replacement), is becoming one of the most performed procedures for lower limbs. However, the anesthetic involvement of the obturator nerve is still controversial, more from the anatomic than from the clinical-anesthetic point of view. To define the anesthetic involvement of the obturator nerve (mixed nerve) it is necessary to adopt well-defined approaches and clinical criteria²⁰. Unfortunately, most studies prioritize only the sensory involvement (dermatome) overlooking the motor part (miotomes) of the obturator nerve, probably because the objectives aim at postoperative analgesia with reflex relaxation of femoral quadriceps innervated by the femoral nerve, and not muscle relaxation of adductor muscles of thigh innervated by the obturator nerve. Another acceptable criteria about obturator nerve involvement in 3-in-1 blockades would be the correlation between anesthetic clinic and contrasted radiological and tomographic results⁸. Although CT-scan provides tridimensional images and contrasted radiological provides a unidimensional study about contrast spread, these images projected on different anatomic elements of the lumbopelvic region help the interpretation of 3-in-1 blockade clinical outcomes.

Considering data available in the literature, in which contrast was located in the lateral side of the pelvis major in 37% of cases²⁹, obturator nerve sensory and motor blocks have been observed in 27% and 22% of cases, respectively^33,40, higher than 13.2% observed in our small sample. Face to this, one may assume that:

1) Anesthetic solution spread to the iliac subfascial space during 3-in-1 femoral blockade with single injection or catheter is always random and unpredictable⁴¹.

2) With single injection, blockade obtained is before all 1-in-1 blockade, or exclusively femoral, in 100% of cases, or 2-in-1 blockade⁴² without obturator nerve participation, or even, in a very low incidence (1.3%), 3-in-1 blockade⁴³.

3) There is no need for peripheral nerve stimulator to insert the long catheter in the iliac subfascial space^21,44,45. With the long catheter medially positioned (medial pelvic zone) or in the lumbar paravertebral region (radiological zone C) anesthetic results are more predictable and 3-in-1 blockade may be overdimensioned as 3.5-in-1 blockade with the involvement of lateral cutaneous of thigh, femoral and obturator nerves and, additionally the femoral branch of the genitofemoral nerve⁵ or the common fibular nerve^6,46.

4) According to Singelyn et al., an anterior 3-in-1 blockade is exceptionally identified as epidural block³⁵.

Additionally, as from this small sample, it is possible to conclude that:

1) Single injection has always resulted in 2-in-1 or 2.5-in-1 blockade (with the involvement of the femoral branch of the genitofemoral nerve) without obturator nerve participation;

2) Short catheter (venous catheter) has resulted in 3-in-1 blockade in 6.6% of cases (one patient);

3) Long catheter introduced through the short catheter acting as a guide has resulted in 3-in-1 blockade in 20% of cases (3 patients), when the former has reached the paravertebral space, or more uncommonly, overdimensioned 3.5-in/1 blockade in 13.32% of cases (2 patients) with additional involvement of the common fibular nerve or of the tibial nerve (Figure 4 and Figure 5).

ACKNOWLEDGEMENTS

The author acknowledges students Martin Geier and Gustavo Andreazza Laporte for their help in this study.

REFERENCES

Submitted for publication July 21, 2003

Accepted for publication November 6, 2003

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*

Received from Hospital Municipal de Pronto Socorro de Porto Alegre, RS

Publication Dates

• Publication in this collection
  22 Sept 2004
• Date of issue
  Aug 2004

History

• Received
  21 July 2003
• Accepted
  06 Nov 2003