Intraoperative transesophageal two-dimensional echocardiography in total hip replacement
A number of studies in medical literature suggest that during implantation of hip prostheses pulmonary embolism of medullary contents and of air may occur. Proof of this suggestion was based on histological examination of lung tissue in animal experiments as well as on post mortem examinations of human tissue. In vivo evidence of this suspected embolism has been lacking so far, since an appropriate technique has not been available. Using transesophageal two-dimensional echocardiography, continuous imaging of the right atrium and the right ventricle can be performed in order to prove this suspected embolization in vivo. Thus, in a prospective randomized study of 26 patients undergoing hip surgery, the right atrium and right ventricle were continuously imaged. Simultaneously, the end-expiratory CO2 partial pressure was recorded. The medical literature suggests that a venting hole in the shaft of the femur prevents the rise in pressure in the medullary space and thus also averts embolism. Therefore, prior to the implantation of the shaft prosthesis, and in order to vent the medullary space, in 13 patients a 4.5-mm lateral borehole was drilled into the femoral shaft, located two finger breadths distal to the point were the end of the prosthesis would be positioned. In 12 of 13 patients in the control group without boreholes, transesophageal two-dimensional echocardiography revealed that air bubbles formed during the implantation of the shaft. In the group with boreholes, however, presence of air could be demonstrated in only four patients (P < 0.01). Emboli were detectable in eight patients in the control of group, but in only two patients in the group with boreholes (P < 0.05). In the control group the median end-expiratory CO2 partial pressure dropped from 35 to 33 mmHG (P < 0.01) because of embolism, but in the group with venting holes this value was 35 mm Hg before as well as after implantation. Transesophageal two-dimensional echocardiography proves that embolization of air and medullary space contents occurs during the implantation of hip prostheses. A venting hole in the shaft of the femur may help to reduce the incidence of intraoperative embolization of air and medullary space contents occuring during shaft implantation, but it cannot eliminate this completely.