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Age, operative time associated with increased PE risk
Hetsroni I. J Bone Joint Surg. 2011. doi:10.1302/0301-620X.93B1.25498.
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Investigators have identified the incidence and risk factors for symptomatic pulmonary embolism after arthroscopic outpatient procedures.
“These risk factors can be used when obtaining informed consent before surgery, to elevate the level of clinical suspicion of pulmonary embolism in patients at risk and to establish a rationale for prospective studies to test the clinical benefit of thromboprophylaxis in high-risk patients,” Iftach Hetsroni, MD, of Sapir Medical Center in Tel Aviv, Israel, and colleagues wrote.
The investigators used the New York State Department of Health Statewide Planning and Research Cooperative System database to review information on outpatient arthroscopic knee procedures performed between 1997 and 2006. They identified patients admitted to the hospital with an associated diagnosis of pulmonary embolism (PE) within 90 days of surgery. This study included 374,033 patients who underwent 418,323 outpatient knee arthroscopies.
The potential PE risk factors were age, gender, surgery complexity, operating time — defined as the total time the patient was in the operating room — cancer history, comorbidities and anesthesia type.
There were 117 PE events with 2.8 cases for every 10,000 arthroscopies. Age and operating time had significant dose-response increases in risk for a subsequent hospital admission for PE, according to logistic regression analysis. Women had a 1.5-fold increased PE risk. Patients with a history of cancer had a three-fold increased risk.
The authors used the New York State hospital admission and outpatient surgery database to identify 418,323 arthroscopic knee surgeries. Of this large cohort, 0.028% of patients were noted to have been admitted within 90 days with a diagnosis of pulmonary embolism. The authors found that increased age and increased operating time were significantly associated with an increased risk of PE. They also noted an increased risk in women, but they were unable to determine how many women were on oral contraceptive medication or hormone replacement therapy, which may significantly impact the risk of developing a PE.
The strengths of this study include the incredibly large cohort, which gives the power to analyze a very rare event in a multivariate model. The limitations, as with all administrative database studies, are the reliance on proper coding. The authors did not use ICD-9-CM code 415.19, which refers to “other pulmonary embolism and infarction,” which may have led to under-reporting of the actual PE incidence, and the fact that the individual positive cases were not validated, may have led to over-reporting. The limited dataset the authors had to work with rendered them unable to identify patients who had received thromboprophylaxis or who were taking anticoagulation medication for an unrelated condition; for these patients, this may have decreased the likelihood of developing a PE.
Despite these limitations, the authors report the largest study to date and have shown that the incidence of symptomatic PE after knee arthroscopy is a rare occurrence (0.028%). They have found an increased incidence with age, female gender and increased operating time, all of which can help the clinician in their preoperative patient discussions and postoperative PE surveillance.
— Greg Maletis, MD
Chief of Orthopedics
Kaiser Baldwin Park
Clinical Professor of Orthopedics
USC/Keck School of Medicine