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Print version ISSN 0034-7094
Rev. Bras. Anestesiol. vol.56 no.5 Campinas Sept./Oct. 2006
Accidental spinal block during vertebral artroplasty. Case report*
Bloqueo no percibido del neuroeje durante la artroplastia vertebral. Relato de caso
Michelle Nacur Lorentz, TSA, M.D.; Virgínia Gomes Martins, TSA, M.D.; Raquel Reis Soares, TSA, M.D.
Anestesiologista do Corpo Clínico do Biocor Instituto
OBJECTIVES: Vertebral artroplasty with bone cement has its particularities
and complications. Most often the procedure is performed under local anesthetic
and sedation, but sometimes it is done under subarachnoid or epidural block
with morphine to achieve postoperative analgesia. The objective of this report
is to discuss the possible complications of vertebroplasties.
CASE REPORT: Male patient, 76 years old, presenting pathologic fracture in T12 was admitted for vertebral artroplasty and bone biopsy. Patient was sedated with midazolam and fentanyl, placed in the prone position, and the surgeon injected local anesthetic from the skin until the vertebral body of T12. He then took a biopsy of the vertebra and injected 6 mL of bone cement in T12. At the end of the procedure the patient presented paralysis of the lower limbs.
CONCLUSIONS: Surgeries in the spinal column are not free of complications. When it is associated with spinal block, the diagnosis of surgical complications might be delayed. Besides, anesthesia might be blamed for a problem caused by the surgical procedure.
Key Words: COMPLICATIONS: lower limbs palsy; SURGERY: vertebral artroplasty.
Y OBJETIVOS: A cirugía de artroplastia vertebral con uso del cimiento
óseo tiene sus particularidades y complicaciones. En la mayoría
de las veces el procedimiento se realiza bajo anestesia local con sedación,
pero en algunos casos se realiza el bloqueo subaracnoideo o peridural con morfina
con el interés de suministrar analgesia postoperatoria. El objetivo de
este relato fue el de discutir las posibles complicaciones en cirugías
de artroplastia vertebral.
RELATO DEL CASO: Paciente del sexo masculino, 76 años, presentando fractura patológica en T12, fue admitido para cirugía de artroplastia vertebral y biopsia ósea. Se realizó sedación con midazolam y fentanil, el paciente fue colocado en decúbito ventral y el cirujano le infiltró el anestésico local desde la piel hasta el cuerpo vertebral de T12; a continuación se realizó la biopsia la vértebra e inyectó 6 mL de cimiento óseo en T12. Al final del procedimiento el paciente presentaba parálisis de los miembros inferiores.
CONCLUSIONES: La intervención quirúrgica en la columna vertebral no es un procedimiento exento de complicaciones. Cuando se asocia bloqueo espinal se puede retardar el diagnóstico de complicación quirúrgica; además de eso, se corre el riesgo de imputársele a la anestesia un problema proveniente del procedimiento quirúrgico.
Percutaneous vertebroplasty is a painful surgical procedure, normally used in elderly patients with bone fractures, while in ventral decubitus, with radioscopy. This procedure uses bone cement in the body of the affected vertebra to achieve pain relief and stabilization. The anesthetic techniques used most often are local anesthesia associated with sedation or local anesthesia with clinical monitoring by the anesthesiologist, but this brings discomfort to the patient 1. There are studies suggesting the use of intraosseous lidocaine 2 to avoid general anesthesia in the elderly patient and sedation while in the prone position. Some professionals use epidural block for opioid injection and relief of postoperative pain, but this technique is not used too often. This surgical procedure has achieved good results regarding pain relief, increased mobility, and improved quality of life in 70% to 95% of the patients 3. This procedure is safe and complications are relatively rare, including bleeding at the puncture site, local infection, leakage of the bone cement into the paravertebral tissues, medular canal and perivertebral venous system, and pulmonary embolism. The incidence of complications increases when multiple levels of the spine are operated on 4-10.
The objective of this report was to discuss the possible complications of vertebroplasty.
Male patient, 76 years old, 76 kg, physical status ASA III, with a pathological fracture of T12 and possible multiple myeloma, was admitted for vertebroplasty and bone biopsy. Patient had hypertension, a diagnosis of abdominal aorta aneurysm below the mesenteric arteries measuring 5 cm in diameter, and acute renal failure in remission (secondary to IV contrast). Three years prior to this admission, he had a surgery to place a vascular endoprothesis in the thoracic aorta. He was taking amiodarone hydrochloride (for atrial fibrillation), atenolol, and cadesartan.
Electrocardiogram showed normal sinus rhythm. Echocardiogram demonstrated mild mitral insufficiency, discrete double aortic lesion, and good ventricular function.
The patient did not receive premedication. Monitoring consisted of continuous electrocardiogram, DII derivation, pulse oximeter, and noninvasive, automatic blood pressure. Heart rate (HR) was 68 bpm and blood pressure (BP) 120 x 80 mmHg. On admission to the patient had a venous access on the left upper limb with a 20G catheter. Fentanyl (100 mg) and midazolam (5 mg) were administered without any changes in PA or HR; pulse oximeter showed a SpO2 of 97%, and oxygen was administered through a nasal catheter (2 L.min-1).
The patient was then placed in the prone position and the surgeon injected 2% lidocaine (20 mL) with vasoconstrictor and 0.75% ropivacaine (20 mL), in different syringes, from the skin and subcutaneous tissue until T12 under fluoroscopic guidance. Initially, a 25 x 7 needle followed by an 18G Tuohy needle was used, injecting the anesthetic progressively until the needle touched the body of the vertebra. After administration of local anesthetic, bone biopsy and vertebroplasty of T12 with 6 mL of bone cement in the body of the vertebra were performed.
Twenty minutes after the administration of the local anesthetic, the patient presented hypotension (PA = 90 x 60 mmHg) without changes in heart rate. Five milligrams of ephedrine were administered. After 10 minutes, another dose was administered and the PA stabilized.
At the end of the procedure, which lasted 60 minutes, the patient was placed in the supine position and asked to move the lower limbs. He could not move them and the sensitivity below T10 was reduced. The anesthesiologist suspected of accidental spinal block caused by the surgeon, but the surgeon suspected of injection of bone cement in the spinal channel. A magnetic resonance imaging (MRI) was done immediately, which demonstrated that the spinal channel was free. The diagnostic hypothesis of accidental spinal anesthesia by the surgeon was reinforced (probably in the epidural space). This was confirmed by the clinical evolution, since the patient regained movement of his legs in three hours, being able to walk normally the next day.
Vertebroplasty (or percutaneous vertebroplasty) has been widely used in the last years to treat fractures of the spine. In the USA, osteoporosis is a common cause of fracture and 1.5 million Americans have fractures secondary to osteoporosis each year 8. The efficacy of the procedure is high, the incidence of complications is lower than 10%, and there are studies on new surgical techniques to reduce these complications 11. Reaction to the polymethylmethacrilate present in the bone cement, causing temporary hypotension, reduction in SpO2, and moderate increase in the pulmonary artery pressure, is the most frequent complication. These changes are temporary and well tolerated by the patients with good cardiopulmonary function. Patients with severe cardiopulmonary dysfunction and pulmonary hypertension might not tolerate these changes, which may lead to dysfunction of the right ventricle and myocardial ischemia, especially if multiple levels are treated 12. Although vertebroplasty is considered a minimally invasive procedure, it may result in severe complications, such as the bone cement implantation syndrome 13,14, characterized by severe hypotension, pulmonary hypertension, and hypoxemia caused more by the pulmonary embolism than by the toxicity of the methacrilate. The bone cement increases the intramedullary pressure, forcing the contents of the bone marrow into the blood stream. During the surgical procedure, the contents of the bone cavity, such as air, fat, and bone marrow, may enter the medullar vessels and cause embolism of the pulmonary circulation. Minor embolisms are common and usually are not detected 15,16; more severe cases demand immediate diagnosis and aggressive treatment 17.
The criteria for patient selection are not completely established. However, there are indications that patients with vertebral lesions resulting from metastasis and myeloma, vertebral hemangioma, and fracture secondary to osteoporosis should be treated with vertebroplasty if the following criteria are fulfilled: pain not responding to drug therapy; if other causes of pain, such as herniated disk, were excluded and the vertebra is not completely destroyed. The use of bone cement is contraindicated in patients with infection of the spinal cord, unstable vertebral fractures, fractures with dislodged bone fragments in the spinal channel, and coagulopathies.
In the case reported here, there was a suspicion of injection of bone cement in the spinal channel with compression of the spinal cord because the patient could not move the lower limbs; MRI excluded this hypothesis. Besides the normal MRI, the patient did not complain of worsening lumbar pain; on the contrary, he experienced mild pain (much less severe than prior to the procedure), and the sensitivity below T10 was decreased. The clinical evolution was benign, with complete recovery of movement and sensitivity. The pain, which prior to the surgery was practically incapacitating, also showed a considerable improvement.
Ropivacaine is a long-acting, amide local anesthetic with less toxicity to the central nervous and cardiovascular systems than bupivacaine. This was observed in human volunteers with continuous infusion of local anesthetics. Besides, doses of ropivacaine above 2 mg.kg-1 have been related to central nervous system symptoms, including behavioral changes and seizures. In general, its cardiovascular toxicity causes sinus tachycardia without hemodynamic changes, despite its vasoconstrictor effect. Some authors defend its association with adrenaline in plexus block to reduce its systemic concentration 18. Its half-life is increased considerably in elderly patients while its clearance is decreased. However, those pharmacokinetic changes do not seem to influence systemic toxicity after a single dose of ropivacaine in elderly patients 19. Lidocaine is an amide local anesthetic, with longer action and decreased duration than ropivacaine; it is used in a dose of 7 to 10 mg.kg-1, and its toxicity is manifested especially in the central nervous system as anxiety, vertigo, and seizures. In this case, the dose of the anesthetic used by the surgeon was, if not excessive, at least borderline, since the patient was elderly and debilitated by prior disease; but apparently the hypotensive episode was due to injection of the local anesthetic in the epidural space. Among the complications of spinal anesthesia are hypotension, neurotoxicity of the local anesthetic, epidural hematoma, nerve lesion, and transverse myelitis 20-22.
The prone position may lead to hypotension when associated with abdominal compression, which is more common in obese patients not properly positioned. It can also compromise spinal cord perfusion due to an increase in venous pressure, especially when associated with systemic hypotension. But this position is adequate for surgical procedures in the vertebrae and does not have hemodynamic repercussions if pillows are used, the patient is not obese and is positioned properly 23,24. In this case, the patient was thin and was positioned adequately. Therefore, it is unlikely that the systemic hypotension was somehow related to the decubitus.
Even though vertebroplasty is considered a safe procedure, the anesthesiologist should have deep knowledge about its particularities, as well as be attentive for possible complications. Very often, patients are elderly and invasive blood pressure monitoring is indicated when reduced cardiovascular function is present. When the surgeon performs the local anesthesia, the anesthesiologist should be aware of the doses and volumes of local anesthetic administered to avoid toxic doses. Regarding regional anesthesia, with or without opioids for postoperative pain, one should have in mind its complications and the possibility of surgical complications that may be attributed to the anesthesia. Regional anesthesia also carries the risk of delaying the diagnosis of surgical complication.
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Dra. Michelle Nacur Lorentz
Rua da Paisagem, nº 280 - Vila da Serra
34.000-000 Nova Lima, MG
Submitted for publication
05 de dezembro de 2005
Accepted for publication 02 de junho de 2006
* Received from Hospital Biocor, Nova Lima, MG