Methylmethacrylate




Abstract


Methylmethacrylate is a bone cement that is commonly used during orthopedic procedures. Its use may be complicated by bone cement implementation syndrome (BCIS), which is a potentially fatal condition characterized by intraoperative hypotension, hypoxia, and possible right ventricular failure. It is important for practioners to be aware of this condition, especially for high-risk patients. In this chapter, we present a typical case as well as discuss the incidence and pathophysiology of BCIS. We also discuss strategies for diagnosis of the problem, other conditions that can present in a similar manner, and management of patients who develop BCIS.




Keywords

bone cement implantation syndrome, fat embolism syndrome, intraoperative hypotension, joint replacement surgery, pulmonary hypertension

 




Case Synopsis


A 75-year-old woman presents for hemiarthroplasty after a femoral neck fracture. She has a history of hypertension, coronary artery disease, moderate pulmonary hypertension, and osteoporosis. Her medications include lisinopril and clopidogrel. The patient undergoes induction of general anesthesia, and the surgery proceeds uneventfully. During cementing of the prosthesis the patient develops severe hypotension, hypoxemia, and tachycardia.




Acknowledgment


The authors wish to thank Dr. Kathryn P. King for her contribution to the previous edition of this chapter.




Problem Analysis


Definition


Methylmethacrylate (MMA) is a pressurized bone cement used in orthopedic surgery. It is a polymer that is formed by mixing methylmethacrylate monomer in liquid form with an accelerator in powdered form. MMA is used in total hip and total knee replacement to implant the prosthesis, as well as for cemented hemiarthroplasty for femoral fractures, among other procedures. The cement is thought to undergo an exothermic reaction and then expand in the space between the prosthesis and the bone.


MMA is associated with bone cement implantation syndrome (BCIS). BCIS is a potentially fatal condition characterized by hypotension and hypoxia, with possible progression to pulmonary hypertension and right ventricular (RV) failure, loss of consciousness, arrhythmia, and even cardiac arrest. It is thought that increased pulmonary vascular resistance causes an acute decrease in RV ejection fraction and a distended right ventricle. The distended right ventricle may bulge into the left ventricle causing decreased left ventricular filling and lowering the cardiac output ( Table 65.1 ). The syndrome can be seen at the time of cementation, femoral reaming, prosthesis insertion, joint reduction, or tourniquet deflation. Until recently there was no widely accepted standardized definition for BCIS, despite the well-known symptoms attributed to it. Therefore the true incidence of the syndrome is unknown. Additionally, there is likely underreporting of lesser degrees of BCIS.



TABLE 65.1

Bone Cement Implantation Syndrome Systemic Effects



















Organ System Effect
Cardiac Decreased MAP, decreased stroke volume with increasing pulmonary vascular resistance → decreased RV ejection fraction
Pulmonary hypertension → right-sided heart failure and eventually left-sided heart failure
Cardiac arrhythmia
Pulmonary Pulmonary emboli → increased pulmonary pressures and V/Q mismatch
Hematology Activation of coagulation cascade and release of vasodilatory mediators
Increased platelet aggregation → increased thrombosis
Central nervous system Confusion, loss of consciousness
If patient has PFO, potential for paradoxic emboli and stroke

MAP, Mean arterial pressure; PFO, patent foramen ovale; RV, right ventricular; V/Q, ventilation/perfusion.

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Feb 18, 2019 | Posted by in ANESTHESIA | Comments Off on Methylmethacrylate
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