Large Airway Response to Cemented Arthroplasty: Relationship to Hypoxaemia. An Experimental Study in Dogs

Abstract

Alteration in airway smooth muscle tone has been implicated in the mechanism of hypoxemia, pulmonary hypertension and changes in dynamic thoracic compliance after total hip arthroplasty (THA). We used the pressure within a water-filled cuff of an endotracheal tube as a continuous measure of changes in tracheomotor tone during THA in mongrel dogs, while intermittently assessing gas exchange abnormalities. In all 16 dogs the instillation of polymethylmethacrylate (PMMA) into the femoral medullary shaft resulted in tracheal dilation. In ten dogs we demonstrated simultaneous hypotension, hypoxemia and increase in shunt fraction (Qs/Qt) after THA. In six dogs the medullary canal was thoroughly lavaged prior to PMMA injection, and no hypoxemia, hypotension or increased Qs/Qt was found in spite of persisting tracheomotor relaxation. We conclude that these well-documented gas-exchange abnormalities are not mediated by changes in large airway tone. Since the hypoxemia was abolished by medullary lavage in our animal model, we suggest that this syndrome is mediated by alterations in lung perfusion and associated small airway constriction and not by changes in large airway smooth muscle tone.

Polymethylmethacrylate: a Review of the Implications and Complications of its Use in Orthopaedic Surgery

“…Pa02 dropped following application of the prosthesis by a mean value of 6.1 mmHg (range 0-13.5 mmHg). Pa02 remained significantly depressed for ten minutes (33). Reported concentrations of MMA monomer in the blood recorded after prosthesis application vary markedly.…”

“…Sherman et al (33) measured pressures within the water-filled cuff of endotracheal tubes placed in dogs during THA. MMA injection was found to cause smooth muscle relaxation and vasodilation resulting in tracheal relaxation (43).…”

“…MMA monomer results in large airway dilation, not constriction. It is concluded that the hypoxaemia associated with PMMA and prosthesis implantation is mediated by alteration in lung perfusion and associated small airway smooth muscle tone (33).…”

Detection of Embolic Events by Capnography and Trans-oesophageal Echocardiography during Total Hip Replacement

“…As has been documented for human patients, disturbances in gas exchange, in pulmonary function and in cardiopulmonary haemodynamics also occur in the majority of dogs after insertion of methylmethacrylate bone cement and a prosthesis. Numerous studies have identified these disturbances as decreases in arterial blood pressure, in end-tidal C02 and in arterial and venous 02 and increases in pulmonary vascular resistance and in pulmonary artery pressure (14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31).…”

“…Depending upon their size, these particles then become lodged in pulmonary arteries, arterioles or capillaries, thereby compromising alveolar gas exchange. This leads to further blood stasis, and propagating thrombosis resulting in the occlusion of additional capillaries (15,19,23,24,36,39,45).…”