Hypotension during cemented arthroplasty. Relationship to cardiac output and fat embolism

Abstract

An episode ofhypotension is common during cemented joint replacement, and has been associated with circulatory collapse and sudden death. We studied the mechanism of hypotension in two groups of six dogs after simulated bilateral cemented arthroplasty. In one group, with no lavage, the insertion of cement and prosthesis was followed by severe hypotension, elevated pulmonary artery pressure, decreased systemic vascular resistance and a 21% reduction in cardiac output. In the other group, pulsatile intramedullary lavage was performed before the simulated arthroplasties. Hypotension was less, and although systemic vascular resistance decreased, the cardiac output did not change. The severity ofthe hypotension, the decrease in cardiac output and an increase in prostaglandin metabolites were related to the magnitude of pulmonary fat embolism. Pulsatile lavage prevents much of this fat embolism, and hence the decrease in cardiac output. The relatively mild hypotension after lavage was secondary to transient vasodilatation, which may accentuate the hypotension caused by the decreased cardiac output due to a large embolic fat load. We make recommendations for the prevention and management of hypotension during cemented arthroplasty.

Polymethylmethacrylate causes prolonged pulmo-nary hypertension during fat embolism: A study in sheep

“…Other experimental studies on FE have also described an increase in PVR with forward failure of the heart (Wheelwright et al 1993, Woo et al 1995. Wheelwright et al (1993) pressurized the distal femur of dogs with a piston, and observed a 400% increase in PVR within the first 3 min after starting the pressurization.…”

“…It has been suggested that the monomer causes systemic vasodilatation (Peebles et al 1972, Berman et al 1974, Samii et al 1980. However, the currently accepted mechanism is the microembolisation of the arterioles and capillaries in the lungs due to the extravasation of bone marrow particles, leading to cardiovascular deterioration (Breed 1974, Orsini et al 1987, Wheelwright et al 1993, Schemitsch et al 1998, Aebli et al 2002. Other explanations have included a nerve reflex triggered by the increase in pressure within the bone marrow cavity during manipulations (i.e.…”

“…reaming, cement injection or implant insertion), similar to the carotid sinus reflex (Rudigier and Ritter 1983). Furthermore, cardiovascular changes during FE may be a result of vasoactive mediators from the bone marrow cavity gaining access to the circulation (Byrick et al 1991, Wheelwright et al 1993). …”

“…In the past, different animal models have been used to investigate FE (Breed 1974, Rudigier and Ritter 1983, Orsini et al 1987, Wheelwright et al 1993, Schemitsch et al 1998. Recently, an animal model of vertebroplasty has been developed to investigate FE (Aebli et al 2002).…”

Fat embolism

“…Venting the medullary canal reduces the emboli during the insertion of the femoral component of hip arthroplasty [95]. Intramedullary lavage has been shown to reduce the incidence of hypotension, pulmonary fat deposition and arachidonic acid metabolites if used prior to cement and prosthesis insertion [96]. Timing of the operative procedure appears to be important.…”