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Revista Brasileira de Anestesiologia

Print version ISSN 0034-7094On-line version ISSN 1806-907X

Rev. Bras. Anestesiol. vol.56 no.1 Campinas Jan./Feb. 2006 



The lateral midfemoral approach to sciatic nerve block as an anesthetic option to trauma. Case report*


Bloqueo del nervio isquiático por la vía medio lateral de la pierna como opción anestésica en traumatismo. Relato de caso



Karl Otto Geier

Anestesiologista do Hospital Municipal de Pronto Socorro de Porto Alegre/RS; Anestesiologista colaborador da Clindor do Hospital São Lucas da PUC/RS; Certificado na Área de Atuação em Dor pela AMB; Membro Efetivo (Life Member) da Sociedade Européia de Anestesia Regional (ESRA); Mestre em Cirurgia pela UFRGS

Correspondence to




BACKGROUND AND OBJECTIVES: Both nervous plexus block and isolated peripheral nerve block are uncommon procedures for patients with lower limb trauma or full stomach, prevailing epidural and spinal blocks as the primary indication. This case report describes the choice of sciatic nerve block as the best indication for a patient with full stomach and severe foot trauma.
CASE REPORT: Male patient, 50 years old, physical status ASA II, moderately obese (BMI = 29.8), hypertensive, bus driver for 29 years with decompressive lumbar laminectomy (L4-L5 e L5-S1) 10 years ago, under antidepressants, who suffered motorcycle accident soon after having eaten. Mallampati test was class III. After excluding several anesthetic techniques, sciatic nerve block was chosen as the best option. Anesthesia was induced with 10 mL of 2% lidocaine and 15 mL of 0.5% bupivacaine, both with epinephrine 1:200 000, resulting in more than 15 hours of analgesia.
CONCLUSIONS: Lateral midfemoral sciatic nerve block as anesthetic option for foot trauma was based on pre-established criteria, such as the preference for regional anesthesia in patients with full stomach and candidates to urgency limb procedures, postural limitation of patients to perform some techniques, such as spinal procedures, anatomic understanding of somatic limb innervation and the mastering of alternative regional techniques.

Key Words: ANESTHETIC TECHNIQUES, Regional: sciatic nerve block; SURGERY, Orthopedic, lower limb


JUSTIFICATIVA Y OBJETIVOS: En pacientes con traumatismo de los miembros inferiores y que están con estómago lleno, los bloqueos de plexos o de los nervios periféricos son infrecuentes, siendo mas comunes los bloqueos centrales, raquídeo y peridural. Este relato de caso muestra la elección del bloqueo del nervio isquiático como mejor indicación para anestesia en un paciente con estómago lleno y traumatismo de pie.
Paciente masculino, de 50 años, estado físico ASA II, obeso moderado (IMC = 29,8), hipertenso, conductor de ómnibus por 29 años, se le efectuó una laminectomía lumbar hace 10 años, usa anti-depresivos y luego de alimentarse fue víctima de accidente en una motocicleta. El test de Mallanpatti mostró que era de clase III. Luego de excluir varias alternativas de técnicas para la anestesia el bloqueo del nervio isquiático fue elegido como la mejor opción. Se administró una solución con 10 mL de lidocaína a 2% y 15 ml de bupivacaína a 0,5%, ambos con adrenalina a 1:200.000, resultando en más de 15 horas de analgesia.
CONCLUSIONES: La elección de bloqueo del nervio isquiático por la vía medio lateral de la pierna, como opción para la anestesia en traumatismo del pie, se basó en criterios ya establecidos, entre los cuales la preferencia por anestesia regional en pacientes con estómago lleno candidatos a cirugía de urgencia en los miembros, la limitación postural para realizar técnicas por la vía espinal, el conocimiento anatómico de la inervación de los miembros y el dominio de técnicas regionales alternativas.




For trauma patients needing lower limb procedures, the anesthetic technique depends on several factors, such as pain-induced impossibility of positioning the patient for some regional techniques; potential problems associated to trauma such as full stomach, hemodynamic instability, difficult conditions to access airways1, co-morbidities, drug interaction and previous procedures, requiring from the anesthesiologists a precise definition of the most adequate technique. This case report aimed at describing a case of regional anesthesia in trauma patient with full stomach.



Male patient, 50 years old, physical status ASA II, moderately obese (BMI = 29.8), hypertensive, bus driver for 29 years, submitted to lumbar laminectomy (L4-L5 e L5-S1) approximately 10 years ago, who had just eaten and was under fluoxetine activity, suffered a motorcycle traffic accident. Evaluated in the first aid unit and treated with opioids, patient was referred to the operating center for urgency foot procedure. At physical evaluation, patient presented generalized contusions and bruises on hip, upper and lower limbs. Since left foot and leg were banded and immobilized by a high splint, the magnitude of the trauma was initially evaluated by X-rays (Figure 1) which showed multiple comminuted exposed fractures of metatarsi with loss of skin, muscle and bone.



At that point patient was communicative, nauseated, hypertensive (160/100 mmHg), rosy and classified as Mallampati class III1,2. General anesthesia was not indicated as first choice due to full stomach; on the other hand, due to pain, patient’s positioning for possible neuraxial block did not favor epidural or spinal anesthesia. Anesthetic option was then sciatic nerve block. Anterior approach was discarded due to high BMI where evaluation and identification of anatomic references - anterior-superior iliac crest, pubic symphysis and femoral artery - would trigger discomfort and pelvic waist pain.

Lateral sciatic nerve approach along the thigh was more feasible. In the upper lateral third, sciatic tuberosity palpation according to original techniques3,4 indicated operational difficulties; in the lower lateral third, immobilization splint ending above the knee would prevent total access to that region, remaining the mid lateral third for blockade induction. After verbal consent and with the patient immobile and supine, great femoral trocanter and anterior border of the femoral biceps muscle were identified. After subcutaneous infiltration with local anesthetic to a depth of approximately 4 cm, a 22G, 8 cm needle was introduced in the coronal plane toward the sciatic nerve for spinal anesthesia5 (Figure 2).



Disesthesias along the sciatic nerve to the foot were referred at 6 cm depth. After negative blood aspiration, 10 mL of 2% lidocaine and 15 mL of 0.5% lidocaine, both with epinephrine 1:200,000 were injected. Seven milliliters of the same solution were reserved for the possible need to block internal saphenous nerve (ISN) by the transsartorial technique6.

Ten minutes later the patient referred loss of sensitivity (lack of pain) and in less than 15 minutes the left foot was removed from the splint, unbound and prepared for surgery. During initial fractures cleaning, patient referred mild foot discomfort and received fractional doses of intravenous 4 mg midazolam and 50 µg fentanyl to induce conscious sedation. Thorough surgical cleaning, dead tissue debridement and fixation of metatarsi with Kirchner thread took 55 minutes resulting in extensive bloody area due to tissue loss (Figure 3).



Very happy with the anesthetic procedure and residual postoperative analgesia, patient was transferred to another hospital for additional treatment 14 hours after surgery completion.



Multiple trauma or orthopedic trauma patients needing urgency procedures are a challenge to the anesthesiologist. Most patients present with conditions similar to our case and a major concern is full stomach which, associated to pain, may delay gastric emptying for more than 24 hours due to the exacerbation of the sympathetic activity on gastrointestinal parasympathetic system. Another problem is routine medication used by the patient.

Routine drugs interaction with general anesthesia may result in undesirable pharmacological synergism. Although fluoxetine, a non-tricyclic antidepressant drug, does not significantly interact with any anesthetic agent, there may be serotoninergic syndrome7 with simultaneous perioperative administration of opioids.

Mallampati test1 should be routine when general anesthesia is scheduled. With Mallampati III and full stomach, anesthetic induction posed a major risk of gastric content aspiration. Although it should be ideally performed in the sitting position, in our patient it was performed in the supine position to help the posterior “drop” of the tongue in the pharynx, impairing Samsoon Young definitions of classes I (whole palate and uvula visible) to IV (soft palate invisible)2.

Plexus or peripheral nerve blocks are adequate indications for acute extremities trauma because they have advantages as compared to spinal anesthesia, especially for not promoting hemodynamic changes. However, a relevant fact in those cases is the difficulty to move the patient due to pain, to perform such techniques. Other considered aspects were previous laminectomy and patient’s professional activity, requiring long periods in the sitting position8, which would limit the spinal technique.

Foot is innervated by the sciatic nerve, sometimes with minor participation of NSI, major branch of the femural nerve. Recently developed5, midfemoral anesthesia is an attractive alternative to proximal and distal sciatic nerve techniques and there are few published papers on the subject. This technique is more reliable and predictable because in this region the sciatic nerve is not divided in its two branches, common fibular and tibial nerves. Notwithstanding this being present in 15% of cases, both branches are virtually contiguous, in a narrow perineural space, thus easily anesthetized with a single anesthetic injection. Sciatic nerve path posterior to femur, almost in the same sagital plane allowing the indirect monitoring of the skin-sciatic nerve distance and the positioning of the lower limb in the neuter position exposing its largest neural surface to the needle are other interesting anatomic details of this technique9. On the other hand, marked clinical characteristic is the almost simultaneous installation of sensory and motor blocks.

According to radiological results (Figure 1), there was the possibility of NSI blockade. Accesses to SNI at the medial condyle of the tibia with subcutaneous infiltration between the tibial tuberosity and the gastrocnemius muscle or the paravenous approach (internal saphenous vein) were impaired by the immobilization splint, as opposed to the transsartorial approach6. However this was not needed because foot trauma extension has not reached the territory innervated by the NSI. As for the sciatic nerve, we decided for the paresthesias/ disesthesias technique with regard to the peripheral nerve stimulator because motor response was unpredictable due to major foot tendon-muscle destruction making difficult the final location of the needle and the success of the blockade. So, we defined sciatic nerve anesthesia through paresthesias/disesthesias by neural needle contact.

Peripheral anesthetic block duration is in general longer as compared to central blocks (epidural and spinal). Usually, sciatic nerve analgesia lasts more than 15 hours with 2 of 0.5% bupivacaine and epinephrine 1:200,000.

This patient was transferred to a different hospital 14 hours after surgery with residual postoperative analgesia induced by surgical anesthetic block. He is still being treated 40 days after the accident, with orthopedic care and reconstructive microsurgery with satisfactory evolution although foot prognosis is still undefined.

This case allows us to conclude that several variables have oriented the anesthesiologist in the choice of the most adequate anesthetic technique for a specific clinical situation. In this patient with multiples trauma, the clinical history and physical evaluation with a high presence of predictive factors for difficult intubation (as the presence of Mallampati1 and Samsoon Young2 tests among other); the interaction of general anesthesia with drugs used by the patient; the prioritization of regional anesthesia for patients with full stomach and candidates to urgency limb procedures; postural limitations to anesthetic blocks; anatomic understanding of somatic innervation of limbs and the mastering of alternative regional anesthetic techniques, have led to the choice of lateral midfemoral sciatic nerve block as the most adequate technique, with satisfactory results both for anesthesia and postoperative analgesia.



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Correspondence to
Dr. Karl Otto Geier
Address: Rua Coronel Camisão, 172
ZIP: 90540-050 City: Porto Alegre, Brazil

Submitted for publication May 31, 2005
Accepted for publication October 3, 2005



* Received from Hospital Municipal de Pronto Socorro de Porto Alegre, RS
· Apresentado parcialmente no XI Congresso Brasileiro de Trauma Ortopédico, Bento Gonçalves/RS de 19 a 21 de Maio de 2005

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