Cardiovascular effects of total hip placement in man. With observations on the effects of methylmethacrylate on the isolated rabbit heart

The Bone Cement Hypercoagulation Syndrome: Pathophysiology, Mortality, and Prevention

Since Charnley introduced acrylic cement to seal metallic hip prostheses in the 1950s, reports of perioperative fatal cardiorespiratory and vascular dysfunctions have been published. Studies on humans and animals have shown neurogenic stimulation and substantial local and systemic activation of coagulation are caused by surgical bone marrow damage and chemical cell destruction by toxic monomeric methyl methacrylate from the implanted cement and other tissue-released substances. Venous blood-borne cell fragments and conjugates of activated cells from the surgical site are sequestered and trapped in the pulmonary microcirculation. A substantial hypercoagulation occurs in the lung circulation. Hypercoagulable blood is passed over to the arterial side and may cause vessel obliteration and organ damage. This process may affect the brain, heart, and kidneys and, through the release of vasoactive substances, introduce hemodynamic imbalances that can lead to fatal outcomes in susceptible populations such as elderly patients with hip fractures. The main underlying pathophysiologic processes leading to these occasionally devastating outcomes are a substantial activation of coagulation and cell destruction caused by the toxic substance released by curing bone cement and several vasoactive substances.

Optimizing patient selection in percutaneous vertebroplasty

Percutaneous vertebroplasty has emerged as an effective technique for treatment of painful vertebral compression fractures (VCFs) caused by osteoporosis, malignancy, and some benign bone tumors. In selecting appropriate patients for vertebroplasty, it is important to distinguish the pain caused by VCF from other numerous causes of back pain. Careful adherence to clinical and imaging selection criteria is crucial to procedural success.

Effects of methyl methacrylate on Ca2+ uptake of cardiac sarcoplasmic reticulum

In isolated cardiac sarcoplasmic reticulum (SR) vesicles, methyl methacrylate (2.5-100mM) directly inhibited initial rates of Ca2+ uptake as well as the maximal uptake. Inhibition of SR Ca2+ uptake by methyl methacrylate was concentration-dependent, and the highest concentration of methyl methacrylate (100mM) almost completely inhibited the SR Ca2+ uptake. EC(50) of methyl methacrylate in percent inhibition of SR Ca2+ uptake was 16.1, 31.9, and 53.4mM at pCa 7.0, 6.6, and 6.0, respectively. At low Ca2+ concentrations (0.1-1 microM), SR vesicles treated with 20mM methyl methacrylate showed the decreased Ca2+ uptake rates. However, further increase of Ca2+ concentration to pCa 5.5 abolished the inhibitory effect of methyl methacrylate on SR Ca2+ uptake, showing no difference between the control and the methyl methacrylate-treated SR vesicles. From these results we could conclude that methyl methacrylate exerts a direct inhibition of cardiac SR Ca2+ uptake. This mechanism, at least in part, might contribute to the profound hypotension induced by methyl methacrylate. Supplementation of calcium ion appears to reduce the methyl methacrylate-induced cardiovascular disturbances efficiently.

Cardiorespiratory and vascular dysfunction related to major reconstructive orthopedic surgery

Major orthopedic reconstructive surgery is highly traumatic and may be associated with serious peri-operative cardiorespiratory and vascular complications which occasionally may be fatal. These complications are commonest in patients receiving cemented hip prostheses following femoral neck fractures. The etiology is multifactorial. Bone traumatization induces activation of the hemostatic system, i.e., thrombin generation, in venous blood draining the operation area. When this activated blood passes the lung, more thrombin is generated and the blood becomes hypercoagulable and causes fibrin-formation in the lung vessels, with trapping of cellular debris. Thrombin has many hormone-like effects beyond its function in the coagulation cascade system. It may increase vein wall permeability and cause constriction of vessels, which increases blood pressure in the lung. In addition, impaction of bone cement to fill bone cavities or to fix prostheses causes additional mechanical trauma and further release of procoagulant substances into venous blood. Further, release of the cytotoxic chemical methyl-methacrylate monomer into venous blood is superimposed on the thrombin-primed hemostatic disturbances in the lung microvasculature. All these effects may finally induce hemodynamic insufficiency, which occasionally may be fatal. To prevent these adverse reactions, thrombin activity should be reduced and impaction of bone cement minimized.

The role of the pulmonary circulation in the regulation of coagulation and fibrinolysis in relation to major surgery

Cardiac surgery and hip replacement surgery (HRS) are associated with serious cardiorespiratory and vascular complications. Activation of blood coagulation and fibrinolysis in the lung vasculature seem to play a key role in the pathophysiology of this process. This article reviews the results of several experimental and clinical studies within this field. Animal studies have shown that bone traumatization induces a marked local activation of coagulation and fibrinolysis in femoral vein blood draining from the surgical area as shown by a 2.5-fold increase in plasma levels of thrombin-antithrombin complexes (TAT) and a seven-fold increase in tissue plasminogen activator (tPA) activity. A slight increase in TAT in femoral vein blood on the unoperated side has also been found and indicates increased activation of coagulation in recirculated blood, which had passed the pulmonary microvasculature. In addition, human studies have shown that bone preparation induced a 200-fold increase in systemic circulating fibrinopeptide-A during surgery and a five-fold increase in TAT (when thromboprophylaxis was stopped 1 week after surgery). Both increases are markers of thrombin generation. Furthermore, cellular studies have shown that thrombin and certain cytotoxic chemicals, such as methylmethacrylate monomer (bone cement), separately and together trigger monocytes to tissue factor (TF) expression and cause endothelial cell shape changes and detachment. This may allow pericellular fibrin formation to occur on monocytes and also transforms the nonthrombogenic endothelial coverage into a highly thrombogenic surface that triggers the conversion of fibrinogen to fibrin and releases fibrinopeptide-A. Finally, sequestration of granulocytes caused release of autodigestive proteases, which may have further strengthened this procoagulant process. Synchronous to the massive intrapulmonary activation of coagulation, an increased fibrinolytic activity was found, as evidenced by a marked drop in arterial blood tPA during surgery. This indicated tPA binding to fibrin deposits in the lung capillaries. However, this clearing process, to obtain adequate blood flow and gas exchange, was shut down several hours after surgery by an antifibrinolytic activity (PAI-1). Thus, these studies indicated that bone surgery induces a substantial intraoperative hemostatic activation in the lung capillaries, which is the primary target organ for venous blood-borne bone-marrow debris. Soft-tissue surgery and vascular surgery seem to induce less systemic activation of coagulation and fibrinolysis.

Methylmethacrylate monomer produces direct relaxation of vascular smooth muscle in vitro

Methylmethacrylate bone cement is associated with severe hypotensive reactions during surgery and anesthesia. The purpose of this in vitro study was to determine if methylmethacrylate monomer could produce hypotension by acting directly on vascular smooth muscle. Segments of human saphenous vein or rabbit thoracic aorta were cut into rings. The rings were mounted in isolated tissue chambers in order to measure isometric tension development. Methylmethacrylate monomer (methylmethacrylic acid ester) produced direct relaxation of venous or aortic rings preconstricted with either potassium ion or noradrenaline. The relaxation was concentration-dependent, occurring at concentrations from 10(-3) to 10(-1) M. The relaxation of rabbit aortic rings (preconstricted with noradrenaline) was unaffected by pre-treatment with atropine, propranolol, cimetidine, indomethacin, or methylene blue. Endothelial stripping with Triton X-100, sufficient to completely abolish acetylcholine-induced relaxation, also had little effect on methylmethacrylate-induced relaxation. Methylmethacrylate produced direct relaxation of rabbit aortic rings constricted with either potassium or noradrenaline in calcium-deficient media, and inhibited subsequent calcium-induced constriction. These results suggest that methylmethacrylate monomer may interfere with intracellular and extracellular calcium mobilization and excitation/contraction coupling in vascular smooth muscle. The direct relaxation of venous and arterial smooth muscle produced by methylmethacrylate monomer may contribute in part to the hypotension that can occur when acrylic bone cement is employed during orthopedic procedures.

Toxic effects of methylmethacrylate monomer on leukocytes and endothelial cells in vitro

The influence of methylmethacrylate monomer (MMA) on the cellular integrity of monocytes, granulocytes and endothelial cells in vitro was investigated. Clinically relevant blood concentrations of MMA (i.e., 5-10 micrograms/mL) were clearly cytotoxic to all cell types studied, as evidenced by the release of lactic dehydrogenase (LD) and 51Cr, and increased uptake of trypan blue (vital staining). Scanning electron microscopic examination of cells treated with 10 micrograms/mL MMA showed marked signs of cytotoxicity after 1 min incubation, and after 30 min the majority of the cells were totally disintegrated. These findings may have clinical bearing on intraoperative cardiorespiratory dysfunction and deep vein thrombosis in MMA-fixed joint replacement surgery.

Does the use of methylmethacrylate cement in total shoulder replacement induce hemodynamic or pulmonary instability?

STUDY OBJECTIVE

To investigate whether the use of methylmethacrylate cement causes hemodynamic or pulmonary instability during total shoulder replacement surgery.

DESIGN

Prospective, nonrandomized study.

SETTING

Operating room.

PATIENTS

9 ASA physical status I and II patients.

INTERVENTIONS

A 20-gauge radial artery catheter was placed in the wrist opposite the surgical site. Sedation with midazolam was provided, and a pulmonary artery catheter was placed through an 8.5-Fr introducer into the patient's right internal jugular vein.

MEASUREMENTS AND MAIN RESULTS

Before induction of anesthesia, systolic, diastolic, and mean arterial blood pressures; heart rate; central venous pressure; systolic, diastolic, and mean pulmonary artery pressures; pulmonary capillary wedge pressure; and thermodilution cardiac output measurements were obtained. Arterial and mixed venous blood gas samples also were collected and analyzed for calculation of Qs/Qt. These hemodynamic and pulmonary parameters were measured again just before cementing of each prosthesis with methylmethacrylate cement and at 1, 5, 10, and 20 minutes after cementing. There were no statistically significant changes in any of the measured hemodynamic parameters at any time. There was no statistically significant difference in the calculated intrapulmonary shunt fraction.

CONCLUSION

In this study population, the use of methylmethacrylate for total shoulder replacement was not associated with adverse hemodynamic events or increased intrapulmonary shunting.

Effect of methyl methacrylate on isolated atria and interaction with isoproterenol, atropine and calcium chloride

1. Spontaneous rate and contractile force of isolated rat and rabbit atria suspended in a tissue bath were recorded before and after drugs. Methyl methacrylate monomer (MMA) alone both decreased force and increased rate dose-dependently. 2. Concentrations of calcium chloride or isoproterenol that alone increased both rate and force of rat atrial contraction were fully and only partially able, respectively, to restore force to normal after MMA. 3. Atropine prevented changes in rat atrial function from low-effective doses of MMA, but not higher ones; it also failed to prevent the reduction of contractile force by a calcium channel blocker, verapamil. 4. There are similarities but also differences between actions of MMA and verapamil on rat atria.

Acute cardiovascular effects of methyl methacrylate monomer: characterization and modification by cholinergic blockade, adrenergic stimulation and calcium chloride infusion

1. Methyl methacrylate monomer (MMA) given by i.v. infusion to anesthetized dogs caused a sustained hypotension, bradycardia, reduction of cardiac output and stroke volume, and increased peripheral resistance. 2. Epinephrine i.v. could reverse the hypotension but not the bradycardia; isoproterenol i.v. could reverse the bradycardia but not the hypotension. 3. Bilateral cervical vagotomy prevented bradycardia but not other cardiovascular effects of MMA, and prevented all respiratory effects except hypoxemia. 4. Calcium chloride i.v. reversed all circulatory changes except bradycardia; a combination of atropine and calcium reversed all cardiovascular changes from MMA.

Intra-operative collapse or death related to the use of acrylic cement in hip surgery

Six intra-operative deaths and two episodes of near-fatal hypotension occurred in 52 consecutive Hastings procedures (insertion of metal prosthesis grouted in acrylic cement) for subcapital fracture of the femoral neck. This high complication rate was identified by a system of clinical audit undertaken by members of the anaesthetic department.

Methyl Methacrylate as a Moldable, Implantable Biomaterial for Use with Ultrasound Transducers

Polymethyl methacrylate (PMMA), an arthroplastic implant material, has been explored as an implant medium for Doppler transducers for blood flow detection in the deep and peripheral vascular bed. A mixture ratio of 0.5 parts polymerized PMMA to 1.0 part monomeric methyl methacrylate (MMA) was found to yield satisfactory characteristics. A significant lack of tissue reaction was noted; at worst, a generalized mild inflammation attributable to implantation surgery was found in both test subjects and controls. Signal transmission was found to be unaltered by comparison of signal characteristics with the prepared implant probe and an uncoated transducer in the surgical site. Examination of the probes, after as long as 4 months, demonstrated no failure due to material characteristics. PMMA is an efficient bonding and moldable compound and is desirable because of its acoustic properties for implantable ultrasound applications.

Blood levels and half-life of methylmethacrylate after tourniquet release during knee arthroplasty

The blood levels and the half-life of monomeric methylmethacrylate after tourniquet release were studied in nine patients with osteoarthrosis or rheumatoid arthritis of the knee joint, treated with the Townley prosthesis under spinal anesthesia. Several ventricular extrasystoles were monitored in one patient with high blood levels of monomeric methylmethacrylate (119.80 micrograms/ml). The blood levels of monomeric methylmethacrylate ranged between 0.10 and 1.44 microgram/ml in the rest of the patients. The half-life of monomeric methylmethacrylate in vivo was 47-55 min.

[Determination of methylmethacrylate in expired gases after hip prosthesis cementing]

Total hip replacement using methylmethacrylate can induce early intraoperative hypoxaemia caused, according to some authors, by alveolar gas dilution by acrylic monomer vapour. In order to test this hypothesis, expired monomer was measured in ten patients undergoing total hip replacement carried out under narconeuroleptanalgesia. Methylmethacrylate was collected by adsorption on activated charcoal and measured by gas chromatography. The quality of expired monomer was 25 +/- 10 micrograms after cotyloid sealing. It is of 264 +/- 396 micrograms after femoral sealing; the most important excretion took place in the first three minutes, and its total duration may exceed 18 min. A simple calculation showed quite convincingly that the volume of expired monomer vapour was not sufficient to explain the hypoxaemia: impaired arterial oxygenation associated with the use of methylmethacrylate is not due to a dilution technique.

Perioperative management of a patient with a malignant pheochromocytoma

A case report is presented of a patient with a known malignant pheochromocytoma, who was to undergo an orthopaedic procedure using methylmethacrylate bone cement. Preoperative preparation of the patient included the use of prazosin and metyrosine. Epidural blockade was chosen as the anaesthetic technique for intraoperative management. Surgical fixation with methylmethacrylate did not produce profound or prolonged hypotension despite sudden massive blood loss prior to its use. Epidural morphine was administered for postoperative pain control.

Methylmethacrylate and atrioventricular conduction in dogs

The effect of intravenous methylmethacrylate (MMA) on atrioventricular conduction times was studied in dogs, utilizing His-bundle electrograms. Dogs were anesthetized with halothane or enflurane; then MMA in a dose causing minimal to profound hemodynamic changes was administered and His-bundle electrograms, and arterial, pulmonary artery, and central venous pressures were recorded. This experimental model did not demonstrate a prolongation of atrioventricular conduction intervals which could be implicated as etiologic in MMA-induced dysrhythmias.

Effects of methyl methacrylate monomer vapors on respiration and circulation in unanesthetized rats

A study was conducted in which two groups of female rats were exposed to vaporized MMA-m for a period of 20 minutes daily for 21 and 42 days, respectively. Systolic blood pressure, heart rate, respiration, and ECG were monitored for 5 minutes prior to MMA-m exposure and then during a 20-minute exposure to MMA-m. On the twenty-first and forty-second day, respectively, the aforementioned vectors were monitored again. During the first exposure 63% of the experimental animals displayed marked changes in respiration ranging from a modified Cheyne-Stokes type to periods of very shallow breathing followed by deep breathing. Thirty-eight percent showed ECG changes ranging from premature ventricular contractions and altered QRS complexes to markedly depressed T waves. Continued exposure resulted in an initial decrease followed by an increased systolic blood pressure with an increased respiratory and heart rate. At the final testing period all animals showed abnormal respiratory patterns and ECG changes and demonstrated a heart block pattern. In all animals systolic blood pressure increased the longer they were exposed to MMA-m.