Lack of Difference In Co-Morbidities Associated with Deep Venous Thrombosis In Patients Undergoing Total Knee Replacement

Thromboprophylaxis is the top challenge to patient safety practice in hospitals. Postoperative Deep vein thrombosis (DVT) and pulmonary embolism (PE) are the major cardiovascular killers in the surgical setting. In October 2008, Medicare designated DVT and PE occurring after total knee or hip replacement as ‘never events', and indicated that they will not pay the incremental cost to manage the complication and has made the hospital acquired DVT/PE unacceptable and serious. There are however, limited data on factors contributing to DVT/PE in-patients undergoing total knee or hip replacement.

To ascertain nationwide health care utilization and associated co-morbidities in Total knee replacement (TKR) recipients who do or do not develop DVT/PE.

We used the year 2007, National Inpatient Sample (NIS) to analyze the post operative occurrence of DVT/PE after TKR. We used an analysis similar to AHRQ's Patient Safety Indicator number – 12 (PSI 12) which is Postoperative Pulmonary Embolism or Deep Vein Thrombosis but restricted our analysis only to TKR. We intended to capture cases of postoperative venous thromboses and embolism - specifically, pulmonary embolism and deep venous thrombosis. For our analysis we separated TKR into 2 groups; one without DVT/PE and the other with DVT/PE. We analyzed all surgical discharges age 18 years and older with an ICD-9-CM code for an operating room procedure TKR (ICD-9 8154). From this we excluded those who have principal diagnosis of DVT/PE, as these patients are likely to have had PE/DVT present on admission and not because of TKR and also where a procedure for interruption of vena cava (IVC filter) (ICD-9 387) occurs before or on the same day as the first operating room procedure as these patients likely had DVT/PE even before TKR. We then created a subset from the first group, with discharges ICD-9-CM codes for deep vein thrombosis or pulmonary embolism in any secondary diagnosis field and thus defined the group of patients who developed DVT/PE after TKR. We used the following ICD-9 codes to represent DVT (ICD-9 codes 451.11, 451.19, 451.2, 451.81, 451.9, 453.40, 453.41, 453.42, 453.8, 453.9) and PE (ICD-9 codes 415.1–415.19). IBM SPSS Statistics 18 was used for data mining and analysis.

In the year 2007, there were 550,770 discharges with a procedure for TKR. After excluding primary diagnosis of DVT/PE and IVC filter, we had 550228 as our working number. Of these, 5454 discharges had a secondary diagnosis of DVT/PE (Rate - 10 new cases per 1000 TKR procedures). Demographics and health care utilization between those who did or did not develop are described in Table 1. Co-morbidities associated with those who did or did not develop DVT are described in (Table 2).

DVT & PE are major avoidable complications of Total Knee replacement and are associated with significant mortality and health care costs. These data demonstrate that there may not be any significant differences in age and associated co-morbidities between those who do or do not develop DVT/PE following total knee replacement except for UTI which can be attributed to the difference in length of stay. The absence of serious co-morbidities like AF and CHF in both groups suggest those with serious co-morbidities may not be receiving total knee replacement. That no differences were noticed in associated co-morbidities among those who did or did not develop DVT/PE following TKR provide the rationale for further study of factors contributing to this serious complication of TKR. Such studies may inform future strategies for prevention of post-operative DVT/PE.

No relevant conflicts of interest to declare.