61 – HYPOXEMIA AS AN INDICATOR FOR PULMONARY EMBOLISM IN THE ACUTE POST-ARTHROPLASTY PATIENT

Purpose: This study was designed to evaluate post-total joint arthroplasty patients who were sent for a chest CT scan in order to determine the clinical factors that were most likely to be associated with, and predictive of, a radiologic diagnosis of pulmonary embolism in the acute, postoperative period. Method: The current study involved a review of 540 total knee replacements and 543 total hip arthroplasty procedures performed from June 2008 to September 2009. All patients received postoperative VTE prophy-laxis using LMWH, as per the protocols established by the Alberta Bone and Joint Initiative, and consistent with the recommendations of the American College of Chest Physicians (2008). A pulmonary CT scan was ordered for patients in situations where 1. a pulmonary embolism was strongly suspected 2. for those who lacked a clear alternative diagnosis as an explanation for their findings 3. when steps to correct the suspected underlying condition failed to normalize results, or 4. in situations where the diagnosis (i.e. new-onset atrial fibrillation) warranted further investigation to rule out a PE as a possible cause. Patients referred for multidetector computed tomography to investigate the possibility of pulmonary embolus were identified, and subjected to a chart review. Results: Forty-two patients underwent a pulmonary CT scan investigation to rule out pulmonary embolus. Of these, 15 patients had undergone hip surgery, and 27 had undergone a total knee replacement. Of the 42 patients, 34 exhibited hypoxemia as their major presenting sign (oxygen saturation less than 90% on room air), with or without other signs or symptoms. Four patients presented with tachycardia alone, and 2 patients presented with chest pain, of which one patient had an associated arrhythmia. Of the 34 patients presenting with unexplained postoperative hypoxemia, 25 were patients who had undergone total knee replacement, and of these 25 patients, 14 (56%) were found to have a pulmonary embolus on CT scanning of the lungs. There were no PE’s identified in the post-hip population. None of the patients with PE’s presented with subjective dyspnea or chest pain. There were no fatalities as a result of PE. Conclusion: The overall high rate of detection of pulmonary embolism in our postoperative population is due the very close monitoring of pulse oximetry combined with the improved sensitivity of imaging modalities. Hypoxemia is emerging as the clinical sign that is most sensitive to the possibility of a PE in the post-knee arthroplasty patient. Reliance on clinical symptoms such as chest pain, dyspnea, or even tachycardia is no longer appropriate. It is recommended that oxygen saturation, as measured by pulse oximetry, should be monitored regularly on all post-arthroplasty patients. Hypoxemia should lead to a prompt and thorough medical workup. If an obvious explanation for the hypoxemia cannot be identified, the patient should undergo a multidetector CT scan to rule out a pulmonary embolus.

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