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Print version ISSN 0034-7094
Rev. Bras. Anestesiol. vol.56 no.5 Campinas Sept./Oct. 2006
Total spinal block after posterior lumbar plexus blockade. Case report*
Raquianestesia total después del bloqueo del plexo lumbar por vía posterior. Relato de caso
Leonardo Teixeira Domingues Duarte, TSA, M.D. I; Renato Ângelo Saraiva, TSAM.D.II
da Rede SARAH de Hospitais do Aparelho Locomotor
IICoordenador de Anestesiologia da Rede SARAH de Hospitais do Aparelho Locomotor
OBJECTIVES: Lumbar plexus blockade can be very useful in surgical procedures
of the hip, thigh, and knee, but it should be performed by an experienced anesthesiologist
due to potential complications. The current report presents a case of total
spinal block after posterior lumbar plexus blockade and discusses the possible
CASE REPORT: Male patient, 34 years old, 97 kg, physical status ASA I, scheduled for total hip arthroplasty. After general anesthesia, a right posterior lumbar plexus blockade was performed with the adjunct of a peripheral nerve stimulator. The needle was introduced to a depth of 8 cm, perpendicular to the skin, 4 cm from the mid line, on a line perpendicular to the spinal process of L4. After identification of a motor response from the quadriceps, the intensity of the current was reduced to 0.35 mA and 0.5% ropivacaine (39 mL) was administered. During the injection, there were intermittent contractions of the quadriceps. After the block, the patient presented apnea, hypotension, and both pupils were dilated. At the end of the surgery, the patient presented motor block of the lower extremities, which reversed only nine hours after the block. In the postoperative period, the patient complained of severe pain; he was discharged 12 days after the surgery without motor or sensitive deficits.
CONCLUSIONS: To identify the psoas compartment, where the lumbar plexus blockade is located, the intensity of the current must be between 0.5 and 1 mA. Motor response with low current indicates that the needle may be inside the sheath that surrounds the nervous root and extends to the epidural and subarachnoid spaces, to where the anesthetic solution might spread. Despite the wide safety margin of the procedure, the anesthesiologist must have keen anatomy knowledge, training on the technique, and be constantly alert to perform a lumbar plexus blockade.
Key Words: ANESTHESIA, Regional: lumbar plexus; COMPLICATIONS: total spinal block.
Y OBJETIVOS: El bloqueo del plexo lumbar puede ser bastante útil
en procedimientos quirúrgicos de la cadera, del muslo y de la rodilla,
pero exige práctica del anestesiólogo teniendo en cuenta sus potenciales
complicaciones. El presente relato tiene como objetivos presentar un caso de
raquianestesia total después del bloqueo del plexo lumbar por la vía
posterior y discutir el probable mecanismo fisiopatológico.
RELATO DEL CASO: Paciente del sexo masculino, 34 años, 97 kg, estado físico ASA I, programado para artroplastia total de la cadera. Fue realizada anestesia general seguida de bloqueo del plexo lumbar derecho por la vía posterior con auxilio de estimulador de nervio periférico. La aguja fue introducida hasta una profundidad de 8 cm, perpendicular a la piel, y a una distancia de 4 cm de la línea media sobre una línea perpendicular al proceso espinoso de L4. Después de la identificación de respuesta motora en el cuadriceps, la intensidad de la corriente de estimulación se redujo hasta 0,35 mA, siendo entonces administrada ropivacaína a 0,5% (39 mL). Durante la inyección, fueron verificadas contracciones intermitentes del cuadriceps. Después del bloqueo, el paciente evolucionó con apnea, hipotensión arterial y midriasis bilateral. Al final de la cirugía, presentaba bloqueo motor en los dos miembros inferiores que solo mejoró nueve horas después de la realización del bloqueo. En el postoperatorio, el paciente se quejó de dolor intenso, recibiendo alta hospitalaria 12 días después de la cirugía sin anormalidades motora o sensitiva.
CONCLUSIONES: La identificación del compartimento del psoas, donde está el plexo lumbar, exige la utilización de intensidad de corriente entre 0,5 e 1 mA. La incidencia de respuesta motora con bajas corrientes puede indicar posicionamiento de la aguja dentro del recubrimiento que envuelve la raíz nerviosa y que continua hasta los espacios peridural y subaracnoideo, para donde la solución anestésica puede se dispersar. A pesar de ofrecer un extenso margen de seguridad, el bloqueo del plexo lumbar demanda del anestesiólogo un conocimiento minucioso de la anatomía, una capacitación en la técnica y una vigilancia constante.
Posterior lumbar plexus blockade is, once more, the focus of special attention in the practice of regional anesthesia after the introduction of the neurostimulator as an adjunct for nerve blocks. It is effective as an anesthetic technique and in relieving postoperative pain in patients submitted to different surgical procedures in the hip, thigh, and knee; total hip arthroplasty is among them 1-3. It is equivalent to the epidural approach in postoperative analgesia, but it has less side effects 4. However, just like other techniques, it is not devoid of complications, and should be performed by an anesthesiologist who knows the technique very well. Although rare, severe complications might occur even with experienced physicians 5.
Total hip arthroplasty is a major surgery associated with severe pain in the first postoperative days. Several anesthetic techniques are used to relieve pain in those patients. The technique chosen must allow the patient to remain mobile, accelerate functional recovery, and decrease postoperative morbidity and mortality 6.
This report presents a case of total spinal block after posterior lumbar plexus blockade and discusses the possible pathophysiological mechanism.
Male patient, 34 years old, 97 kg, 1.87 m, physical status ASA I, scheduled for total right hip arthroplasty for avascular necrosis of the femoral head. The technique proposed was general anesthesia combined with posterior lumbar plexus blockade for the postoperative analgesia.
Monitoring included continuous electrocardiogram, derivations leads DII and V5, noninvasive blood pressure, pulse oximeter, capnograph with gas analyzer, esophageal temperature, and urine output. General venous anesthesia was induced with fentanyl, propofol, and succinylcholine, followed by tracheal intubation. Anesthesia was maintained with isoflurane, oxygen and nitrous oxide.
The patient was placed on left lateral decubitus in order to perform the right posterior lumbar plexus blockade with a peripheral nerve neurostimulator. At this moment, the patient was breathing spontaneously. The technique described by Capdevilla et al. 3 was used for the lumbar plexus blockade. The spinal process of L4 was identified at the line between both antero-superior iliac crests. A line perpendicular to the midline was drawn at the spinal process of L4. The needle was introduced in this line, 4 cm from the midline.
The short-beveled, electrically isolated needle was introduced perpendicular to the skin until there was a motor response from the quadriceps without any contact with the transversal process of L4. The needle reached approximately 80 mm deep. Motor response was initially identified with a current of 1.5 mA, which was then reduced to 0.35 mA.
The anesthesia was not difficult and there was a motor response at the first attempt. Thirty-nine milliliters of 0.5% ropivacaine was then administered (2 mg.kg-1), in small doses, making sure there was no aspiration of blood or CSF. However, during the administration of the anesthetic, and after muscle contractions had ceased, contractions of the muscle were observed once again.
After the block, the patient was placed in the supine position. At this point the patient presented apnea. Approximately 10 minutes after the block, he presented hypotension with a systolic pressure of 75 mmHg. He was treated with increasing fluids infusion and bolus of ephedrine 10 mg. The suspicion of subarachnoid injection of the anesthetic was reinforced when the patient presented dilated pupils bilaterally. He was maintained on controlled pulmonary ventilation and, after he was hemodynamically stable, the surgical procedure started.
At the end of the surgery, which lasted 150 min, the patient recuperated spontaneous breathing, pupils were no longer dilated, and he awakened from general anesthesia quickly, without complications. He presented motor block in both lower extremities (Bromage III).
The patient was transferred to the postanesthetic recovery units for observation and monitoring. He was discharged from the recovery room nine hours after the lumbar plexus blockade without motor anesthesia on the left lower limb but still with a motor anesthesia on the right lower limb (Bromage III). He complained of severe pain on the hip and patient controlled analgesia (PCA) with morphine was prescribed.
He was discharged from the hospital 12 days after the surgery without motor or sensitive deficits.
Even though epidural anesthesia is the anesthetic techniques used most often for the treatment of postoperative pain in total hip arthroplasty, lumbar plexus blockade has some advantages regarding the quality of analgesia, and the reduced incidence of adverse effects and complication. It allows to avoid potential problems that could occur with epidural anesthesia. While epidural block can be technically difficult in this patient population, usually elderly, lumbar plexus blockade is easier to perform and does not require flexion of the hip. Besides, it produces limited and unilateral sympathetic block resulting in decreased hemodynamic instability when compared to epidural block 4. This patient population frequently takes anticoagulants 4. In these circumstances, epidural hematoma is a possible complication, making the lumbar plexus blockade a safer technique for peripheral block. Peripheral nerve blocks present a lower incidence of postoperative nausea, vomiting, and urinary retention 7, increasing patient satisfaction 4. A large, prospective, clinical study demonstrated the significantly lower incidence of severe complications (death, neurological lesion, cardiac arrest) in patients who underwent peripheral nerve blocks than in patients who underwent total spinal blocks 5.
We identified in the literature only two clinical cases of total spinal block after posterior lumbar plexus blockade 8,9. However, it is reported that the subarachnoid spread of anesthetic after posterior lumbar plexus blockade has severe complications (cardiac arrest, respiratory failure, seizures, and death) in those patients 5.
The lumbar plexus is composed of the ventral branches of the L1, L2, L3, and L4 roots and can receive contributions from T12 and L5. It is located inside the major psoas muscle and anterior to the transverse process of the lumbar vertebrae 3,10. Thus, the psoas muscle must be penetrated in any technique of posterior lumbar plexus blockade.
Approaching the lumbar plexus at the level of the transverse process of L4 reduces the possibility that the anesthetic will reach the epidural space and the risk of damaging the inferior pole of the ipsilateral kidney, such as in the L3 approach 11. The epidural spread of the anesthetic may produce unilateral or symmetrical, bilateral, anesthesia. The determining factors are not fully explained. It may be related to the position of the needle at the time of the injection, administration of the drug near the intervertebral foramen when the needle presents a medial inclination, accidental epidural administration, fast administration in the dura-mater sheath of the nerve roots, the use of large volumes of anesthetic drug, and the presence of deformity of the spine 12. Depending on the study, the diffusion of the anesthetic into the epidural space may reach 16% 13.
The different techniques were described according to the point of entrance of the needle, but they all have in common the contact of the needle with the transverse process to guide the depth of insertion. A study using CT scan showed that the distance of the transverse process of L4 to the lumbar plexus is a mean of 18 mm, varying from 15 to 20 mm, and does not depend on the patient's gender or body mass index 3. On the other hand, the depth of the lumbar plexus from the skin, at the level of L4, is a mean of 85 mm in men and 70 mm in women, and is directly related to the patient's body mass index 3. Thus, the transverse process is the reference to avoid introducing the needle too deep and the complications secondary to the penetration of the retroperitoneum or the abdomen.
One should be very careful when inserting the needle. It should be perpendicular to the skin and the depth should be guided by the position of the transverse process of L4. The distance between the medial edge of the psoas muscle and the midline is 2.7 ± 0.4 cm 10. Therefore, approaching the lumbar plexus by a more medial entry point in the skin or pointing the needle medially allows the entrance in the medullar canal or in the nervous root sheath. Even using nerve stimulation to guide the block, the consequence is the same in both situations injection of the anesthetic in the epidural space or in the subarachnoid space 8,9.
Identifying the lumbar plexus by observing contractions of the quadriceps and movement of the patella implies the need of a current of 0.5 and 1.0 mA. A current smaller than 0.5 mA indicates that the tip of the needle is in contact with the lumbar plexus. During the procedure in this patient, motor responses were present with a 0.35 mA current. Thus, the needle could have been inside the sheath that surrounds the nerve root and continues into the epidural and subarachnoid spaces, to where the anesthetic must have spread. A test dose was not injected because the subarachnoid administration would not have been identified under general anesthesia. Besides, its efficacy in identifying intravascular injection is uncertain under general anesthesia.
Despite being supported by studies in the literature 3, the use of large doses of anesthetics, as was the case of our patient (39 mL), may favor the spread of the drug to the epidural space due to the proximity with the paravertebral space and the pressure of administration. Further studies are necessary to evaluate the spread of smaller volumes of anesthetics in the psoas compartment and its efficacy in blocking the different branches of the lumbar plexus.
The epidural spread of anesthetics could manifest as hypotension and hemodynamic instability. However, the findings associated with apnea and dilated pupils are more consistent with subarachnoid administration and total spinal block.
Nervous blocks under general anesthesia are commonly performed in children and non-cooperative patients. However, some authors disapprove its use in adult patients, even using a nerve stimulator 5. On the other hand, lumbar plexus blockade can be very uncomfortable for a conscious patient, and performing it under general anesthesia guarantees both patient comfort and makes it easier for the anesthesiologist.
In this case, it is possible that the peripheral nervous block with the patient under general anesthesia did not change the development and evolution of the complication. Directing the needle medially is a determining factor for a possible administration into the subarachnoid space when reaching the sheath of the nerve root, even without aspiration of CSF. Besides, it is important to know that motor response with low currents (< 0.25 0.30 mA) suggests the proximity to the nervous root. The needle might be inside the nervous root or even intraneural. The persistence of motor response after the administration of part of the anesthetic should have indicated to the anesthesiologist the possibility of intravascular or intraneural injection. Thus, identifying motor response with currents of 0.4 to 0.5 mA, and the slow and fractioned administration of the anesthetic, are effective measures in preventing complication.
Peripheral nerve blocks have become more popular for anesthesia and postoperative analgesia. Besides being safer than neuraxis anesthesia, these blocks demand a keen anatomy knowledge by the anesthesiologist, training in the technique, and constant attention.
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Dr. Leonardo Teixeira Domingues Duarte
SQSW 306, Bloco E, 304
70673-435 Brasília, DF
Submitted for publication
20 de dezembro de 2005
Accepted for publication 27 de junho de 2006
* Received from Hospital Sarah - Brasília, DF