Prevention of postoperative thrombosis by aspirin.

In a random double-blind trial monitored by 125I-fibrinogen leg scan, impedance plethysmography, and contrast phleobograms if impedance became abnormal, hydroxycholoroquine was shown to be no more effective than placebo for prevention of venous thrombosis after total hip replacement. Subsequently, the combination of hydroxychloroquine with aspirin was shown to be not significantly better than aspirin alone. Although the two parts of the trial were performed in an identical manner, comparison of the two sequential parts of this investigation, which provided a significant tread favoring aspirin, must be interpreted with caution. Further study including concurrent controls is needed.