The anticoagulated patient: Strategies for effective blood loss management

Use of Molecular Dynamics for the Refinement of an Electrostatic Model for the In Silico Design of a Polymer Antidote for the Anticoagulant Fondaparinux

Molecular dynamics (MD) simulations results are herein incorporated into an electrostatic model used to determine the structure of an effective polymer-based antidote to the anticoagulant fondaparinux. In silico data for the polymer or its cationic binding groups has not, up to now, been available, and experimental data on the structure of the polymer-fondaparinux complex is extremely limited. Consequently, the task of optimizing the polymer structure is a daunting challenge. MD simulations provided a means to gain microscopic information on the interactions of the binding groups and fondaparinux that would have otherwise been inaccessible. This was used to refine the electrostatic model and improve the quantitative model predictions of binding affinity. Once refined, the model provided guidelines to improve electrostatic forces between candidate polymers and fondaparinux in order to increase association rate constants.

The effects of clopidogrel (Plavix) and other oral anticoagulants on early hip fracture surgery

OBJECTIVE

Risk for bleeding complications during and after early hip fracture surgery for patients taking clopidogrel and other anticoagulants have not been defined. The purpose of this study is to assess the perioperative bleeding risks and clinical outcome after early hip fracture surgery performed on patients taking clopidogrel (Plavix) and other oral anticoagulants.

DESIGN

Study design is a retrospective cohort analysis using data extracted from hospital records and state death records.

SETTING

Regional medical center (level II trauma).

METHODS

Data for 1118 patients ≥60 years of age who had surgical treatment for a hip fracture between 2004 and 2008 were reviewed. Eighty-two patients undergoing late surgery (>3 days after admission) were excluded. Patients taking clopidogrel were compared against those not taking clopidogrel. In addition, patients taking clopidogrel only were compared against cohorts of patients taking both clopidogrel and aspirin, aspirin only, warfarin only, or no anticoagulant.

RESULTS

Seventy-four of 1036 patients (7%) were taking clopidogrel, although control groups included 253 patients on aspirin alone, 90 patients on warfarin, and 619 taking no anticoagulants. No significant differences were noted between patients taking clopidogrel and those not taking clopidogrel in estimated blood loss, transfusion requirement, final blood count, hematoma evacuation, hospital length of stay (LOS), or mortality while in hospital or at 1 year. A higher American Society of Anesthesiologists score was seen in the clopidogrel and warfarin groups (P = 0.05 each), increased LOS in the clopidogrel group (P = 0.05), and higher rate of deep vein thrombosis seen in those patients taking warfarin (P = 0.05). Clopidogrel only versus aspirin versus both aspirin and clopidogrel, versus no anticoagulant versus warfarin showed no significant differences in estimated blood loss, transfusion requirement, final blood count, bleeding or perioperative complications, or mortality.

CONCLUSIONS

Patients undergoing early hip fracture surgery who are taking clopidogrel, aspirin, or warfarin (with regulated international normalized ratio) are not at substantially increased risk for bleeding, bleeding complications, or mortality. Comorbidities and American Society of Anesthesiologists scores were significantly higher in the clopidogrel group, which may have resulted in the increased postoperative LOS in this group.

Does low-dose aspirin increase blood loss after spinal fusion surgery?

BACKGROUND CONTEXT

Low-dose aspirin for the prevention of cardiovascular disease is recommended to be discontinued at least 7 days before spinal surgery.

PURPOSE

To determine the effect of stopping low-dose aspirin at least 7 days before surgery on the level of the perioperative blood loss or complications related to hemorrhage.

STUDY DESIGN

Retrospective case study.

PATIENT SAMPLE

Patients who underwent spinal fusion surgery for degenerative lumbar disease.

OUTCOME MEASURE

Clinical outcome was measured by the Oswestry Disability Index.

METHODS

The aspirin group included 38 patients who had taken 100 mg aspirin for an average of 40.3 months. They stopped aspirin for at least 7 days before surgery (mean, 9.0 days). The control group included 38 patients who had not taken aspirin. Both groups were matched in terms of age, gender, number of fused segments, and surgical procedures. The diagnosis in all patients was degenerative spinal disease.

RESULTS

The mean age in the aspirin and control groups was 68.5 and 69.1 years, respectively. The mean number of levels fused was 2.0 segments in both groups. During surgery, the estimated blood loss was 855.3 cc in the aspirin group and 840.8 cc in the control group with no significant difference (p=.84). However, there was a significant difference in blood drainage after surgery. The hemovac blood drainage after surgery was 864.4 cc in the aspirin group but only 458.4 cc in the control group (p<.001). Therefore, the transfusion requirement after surgery was significantly greater in the aspirin group than in the control group (p=.03). The rate of complications related to hemorrhage was higher in the aspirin group than in the control group.

CONCLUSIONS

The intraoperative blood loss during spinal fusion surgery was similar in both groups. However, the blood drainage after surgery was significantly higher in the aspirin group despite stopping aspirin 7 days before surgery. Hence, surgeons should pay careful attention to postoperative blood loss and complications related to hemorrhage in patients who have been taking low-dose aspirin.

Case files of the Medical Toxicology Fellowship at Banner Good Samaritan Medical Center in Phoenix, AZ: a non-warfarin anticoagulant overdose

A 50-year-old man presented to the emergency department (ED) following an overdose of his "blood thinners." The patient had become increasingly depressed over financial concerns, prompting a suicide attempt. He declined to provide any details regarding his current medications or his past medical history. A review of the computerized medical record, however, revealed he had a Factor V Leiden mutation with multiple venothromboembolic events. He previously had an inferior vena cava filter placed, and had received tissue plasminogen activator (tPA) for a cerebrovascular accident. A toxicology consult was obtained in the ED.