In this study of heparin dosing practices in a large representative population of elderly Medicare beneficiaries with DVT or pulmonary embolism, we found that approximately two thirds achieved a therapeutic PTT during the first 24 hours of therapy. This is somewhat better compliance with this guideline than was found in studies of practice in hospitals in Tennessee,12
This result is remarkable given that most other studies classified patients who had only a transiently therapeutic PTT during the first 24 hours as therapeutic, while we required that consecutive PTTs be within the therapeutic range in order to avoid giving credit for patient who had had a PTT that was therapeutic following a heparin bolus. When we recalculated our measured compliance using this criterion (but excluding therapeutic PTTs obtained within 4 hours of starting treatment), it rose to 72%.
The reason for the superior performance we found is unclear. It may be that the older age of patients in the present study allows the traditional starting dose of a 5,000-U bolus and 1,000 U/h to put more patients into the therapeutic range, even though there is evidence from a randomized controlled trial that a heparin dosing nomogram using a more aggressive starting dose is more effective than a nomogram using these traditional starting doses.13
Alternatively, evidence in the literature supporting more aggressive heparin dosing may have been translated into improved practice by the physicians practicing in the study hospitals.
The proportion of patients achieving a therapeutic PTT within 24 hours is less, however, than the 77% to 99% proportion reported by a number of hospitals following the introduction of dosing nomograms.8, 10, 13–16
One other study showed that use of a nomogram allowed achievement of this goal in 66% of patients, but this was a marked improvement over the 38% of patients who reached the goal prior to the nomogram.9
None of the hospitals in the study was routinely using a dosing nomogram by the end of 1992; therefore, such protocols likely represent one way to improve heparin dosing practices. Despite the absence of dosing nomograms in any of the hospitals, there was significant variation among hospitals in the proportion of patients who achieved a therapeutic PTT within 24 hours. In visits to present these data at 10 of the hospitals, no clear explanations for this variation emerged.
This is the first study to demonstrate significant differences between clinical practice and a number of other consensus recommendations including routine monitoring of platelet counts, duration of heparin therapy, and early initiation of warfarin in this population. Early warfarin administration might also represent an opportunity for substantial cost savings. Our finding that early warfarin administration was associated with a 1.5-day decrease in median length of stay is supported by randomized trial data demonstrating that this approach is both safe and cost-effective.14, 21
Our data suggest that 3,240 (42%) of the 7,714 Pennsylvania Medicare beneficiaries (unpublished analysis of Medicare claims by KePRO) admitted with DVT during 1992 did not start warfarin therapy within 2 days of starting heparin, therefore, improved compliance with early warfarin initiation could reduce total hospital days for this group by nearly 5,000 days. Similar savings might be expected in other parts of the country.
There are a number of potential reasons for the suboptimal compliance noted in our study. First, the attending physicians might not agree with the consensus recommendations. Indeed, the primary study end point, achievement of a therapeutic PTT within 24 hours, is not supported by any randomized controlled trial, but rather by retrospective comparisons of patients who did and did not achieve this end point.3, 22
Moreover, some researchers have questioned the validity of the assertion that not achieving therapeutic anticoagulation early in the course of treatment leads to unacceptably high recurrence rates.23
This is supported by our observation that, for patients in our study, the rate of readmission for DVT or pulmonary embolism during the 90 days following the index admission was just 2.5%, and was similar in patients who did and patient who did not achieve therapeutic anticoagulation within 24 hours of starting heparin (data not shown). However, in presentations of the data to physicians practicing at 10 of the 21 study hospitals, none disagreed with the consensus recommendations that we used as benchmarks.
Second, the nature of the study population may have made the recommendations inappropriate for the individual patients. However, we restricted our study to those patients in whom intravenous heparin was the initial therapy and excluded those who had placement of a vena cava filter, were transferred, or died during the hospitalization. Further, we note that virtually all of the study population was discharged on warfarin. Each of these factors suggests that the practices seen in our study reflect the results of straightforward treatment of elderly patients with intravenous heparin for DVT and pulmonary embolism.
Third, inadequate monitoring of PTTs and platelet counts might reflect physicians' responses to perceived fiscal constraints. However, the best compliance was with the guideline that 5 days of heparin therapy be provided—perhaps the most expensive of the end points to achieve. Further, the early use of warfarin, which most evidence suggests would lead to cost savings, was not widespread. The wide spectrum of end points examined makes it clear that our results reflect more than a problem with a single aspect of care (e.g., poor turnaround time in the clinical laboratory).
Finally, one might question whether it is reasonable to expect 100% compliance with these recommendations, given the wide diversity of clinical situations faced by individual clinicians and patients. Moreover, dosing of unfractionated heparin is notoriously difficult. We agree that 100% compliance is unlikely to be achieved, but point out that three of five recommendations (for early warfarin use, for therapeutic PTT within 24 hours, and for routine checks of platelet counts) were met by fewer than two thirds of the patients in the sample. Moreover, evidence in the literature suggests that the degree of compliance can be increased with relatively simple interventions. Further, each of the hospitals with which we discussed the study results believed that compliance could be improved with relatively simple interventions, such as physician education or institution of a nomogram. The results of these interventions are currently being evaluated.
In conclusion, we have shown that the delivery of heparin therapy for DVT and pulmonary embolism to Pennsylvania Medicare beneficiaries often fails to achieve a number of process objectives for such therapy set forth in ACCP consensus recommendations published in 1989.5
Unlike previous studies, our study reflects clinical practice with a random sample of patients who were drawn from a diverse sample of hospitals, and thus are likely to reflect representative anticoagulation practices in older patients throughout the state. We found that compliance with at least one of these recommendations, achieving early therapeutic levels of anticoagulation, exceeded that which was reported in the literature.