Transient Arterial Hypotension Induced by Polymethylmethacrylate Injection during Percutaneous Vertebroplasty

Abstract

Editor: Percutaneous vertebroplasty (PV), ie, the consolidation of a vertebral body with polymethylmethacrylate (PMMA), is a safe and effective image-guided technique for the treatment of benign and malignant lesions of the spine (1). Systemic reactions such as hypotension, bradycardia, and cardiac arrest potentially leading to intraoperative death are welldocumented complications of PMMA application during hip surgery (2,3). We report a case of acute hypotensive reaction occurring during PV. A 65-year-old woman with osteogenesis imperfecta presented with a painful T9 compression fracture. Her medical history was otherwise unremarkable. There were no known allergies. PV was performed under local anesthesia and conscious sedation with use of intravenous fentanyl (50 mg) and midazolam (1 mg). Prophylactic antibiotic therapy (cefazolin 1 g intravenous) was given. A right transpedicular approach with use of an 11-gauge trocar needle was performed without difficulty. PMMA (Osteobond; Zimmer, Warsaw, IN) was prepared by mixing the liquid copolymer (10 mL) with the copolymer powder (13 g) and sterile barium powder (7 g). Three milliliters of PMMA were injected into the vertebral body under continuous fluoroscopic control. A sudden decrease in blood pressure was noted shortly after the beginning of the injection (Fig). The patient immediately reported feeling lightheaded and had a sensation of generalized weakness. There was no other signs or symptoms such as skin redness, hives, sweating, nausea, or dyspnea. A minimal leak in a lateral perivertebral vein was noticed. There was no cement leakage toward the spinal canal, neural foramina, or the adjacent disc spaces. No changes in cardiac electrophysiology, heart rate, or O2 saturation were noted. The blood pressure returned to baseline values within 15 minutes without specific therapeutic measures other than increasing the intravenous saline perfusion rate. A contralateral transpedicular approach was performed and an additional 4 mL of PMMA were injected uneventfully. The patient was discharged pain-free and the follow-up was unremarkable. Systemic reactions related to PMMA during hip arthroplasty have been well documented (2,3). A bone cement implantation syndrome has been characterized, including hypotension, hypoxemia, and cardiac arrhythmia potentially leading to cardiac arrest. Pathogenic mechanisms remain unclear, but possible explanations include pulmonary embolism caused by tissue debris or bone marrow expelled from the medullary cavity, a neurogenic reflex, and direct toxic or vasodilatating effects of the bone cement. Improvements in operative technique such as venting of the medullary cavity and avoidance of bone marrow compression by filling the distal femoral cavity have significantly decreased the incidence of systemic reactions, supposedly by reducing the release of microemboli into the venous circulation. During PV, the risk of cement or bone marrow embolization into the venous system and pulmonary circulation seems to be limited by the small quantities of PMMA used and by the continuous fluoroscopic control of the injection. However, fluoroscopic monitoring shows only the distribution of opacified PMMA, making it impossible to exclude the release of microemboli composed of bone marrow or tissue debris into the venous system. Although the latter possibility seems unlikely considering the minimal mechanical trauma involved with PV, no data exist concerning the increase in intramedullary pressure and the potential release of bone marrow emboli during PV. In our patient, a minimal leak of PMMA into a small perivertebral vein was noticed. Minor leaks into the perivertebral venous system are frequently observed during PV and, to our knowledge, have never been associated with cardiocirculatory changes. Even in a published case of pulmonary embolism caused by PMMA leakage during PV, no cardiovascular changes were observed (4). Direct systemic vasodilation or toxic effects of polymerized PMMA appear unlikely because most of the leaked cement would either remain at the site of implantation or be trapped in the pulmonary circulation. Leaching of the cement constituents during injection with passage of monomer into the blood circulation might, conversely, produce systemic effects. Methylmethacrylate monomer was constantly found in blood samples taken from the radial artery, the pulmonary artery, and the inferior vena cava Figure. Evolution of the systolic and diastolic blood pressure values (in mm Hg) during the procedure (time in minutes). The recording begins with the administration of intravenous sedation; the arrows indicate the time of cement injection. Letter to the Editor