Appropriateness and Timeliness of Initial Thromboprophylaxis in Patients with a Hospital Acquired Venous Thrombosis in a Single Center: A Case Control Study

Venous Thromboembolism (VTE) remains the number one preventable cause of hospital acquired morbidity and mortality (1). To mitigate this, guidelines are published for the prevention of VTE (2). Currently, the rate of adherence to guidelines is between 16 and 60% (3). Studies show even short periods of immobilization can increase risk for VTE (4), thus we postulated that delays in prophylaxis may correlate with more VTEs.

Between January 2009 and December 2011, hospital acquired VTEs were identified at a 600 bed teaching hospital. Control cases were selected from consecutive admissions in February 2011 to match the VTE cases by risk category, age and gender. Patients younger than 18 years, or initiated on therapeutic anticoagulation were excluded.VTE was confirmed by imaging, and timing was recorded from time of presentation to time of administration. Prophylaxis appropriateness was determined according to published guidelines (2).

Categorical variables were compared using Chi-squared test for independence. Normally distributed continuous variables were compared using 2 tailed T-test.

179 cases of hospital acquired VTE were found between 2009 and 2011. 9 cases were excluded due to age or therapeutic anticoagulation. 170 control cases were matched by risk category, age and gender. The patient characteristics are summarized in Table 1. Appropriate prophylaxis rate was lower in the VTE group.(p< 0.0001)(55% vs 80%) There was a higher rate in VTE risk assessment in the VTE group (p=0.021) (90% vs 82%). There was no significant difference (p=0.67) in the timing of initial prophylaxis. (33.4hrs vs 34.8hrs)

Prophylaxis choices are summarized in Table 2. The rate of sequential compression devices (SCDs) ordered but undocumented is high in both groups. In many cases, it was the sole prophylaxis ordered, and would have been sufficient (11% VTE, 12% control). Documented contraindications to chemical prophylaxis are shown in table 3. Notably, several cases were listed as “high bleeding risk” but had no identifiable risk. Also among the cases listing thrombocytopenia, only one had less than 50k platelets.

Between 2009 to 2011, 170 evaluable cases of VTE were compared against matched controls. There was no difference in the time to prophylaxis in both groups; however the 34 hour delay shows a need for improvement. The statistically lower adherence rate to guidelines in the VTE group is in keeping with other published series (3). This is made more poignant by the higher risk assessment rate in the VTE group, which should increase adherence rates. The low documentation rate of SCDs in both groups stresses the need for standardized documentation. Adherence rates would be higher since SCDs would be sufficient in many cases. Incorrect risk assessment, especially with regard to bleeding risk and thrombocytopenia highlight the need for improved understanding of true chemical prophylaxis contraindications. This study demonstrates the importance of continued adherence to prophylaxis throughout hospitalization.

No relevant conflicts of interest to declare.