Letter to the Editor: The “Cough Trick” Reduces Pain During Removal of Closed-suction Drains after Total Knee Arthroplasty: A Randomized Trial

To the Editor,

We read the study by Yuenyongviwat and colleagues [6] with great interest.

In their randomized controlled trial, the authors investigated whether the “cough trick” reduces pain while a surgeon is removing a closed-suction drain after TKA. The authors found that the mean pain level during drain removal was lower in the cough trick group than the control group; the mean difference of 2.1 was more than the minimal clinically important difference (MCID). The authors recommended this trick as a noninvasive method for decreasing potential pain. However, there are certain concerns that need to be addressed before the results and conclusions of this study can be applied to the larger population of TKA patients.

First, the approach requires removing the drain swiftly while coughing. Coughing may be associated with joint movements and muscular spasms, and such spasms can potentially cause entrapment of the drain inside joint and muscles, possibly causing drain breakage when pulled suddenly. There is no information mentioned in the study regarding any complications encountered while removing drain using such maneuver. Such a potential complication merits mention in the discussion to caution the readers reproducing such method. Moreover, the MCID for TKA pain improvement and worsening was previously defined as - 2.26 and - 2.91, respectively [1]; the reported mean difference of 2.1 in current study falls short of those MCIDs. Thus, the trick does not seem to produce any clinically important difference in pain during drain removal. Furthermore, the pain while removing drain was reported to decrease even below the baseline levels in the cough group. It is difficult to understand how momentary cough can reduce even the baseline pain levels after TKA, which other analgesics failed to reduce. Although the postoperative protocol in the two groups was similar, there is no mention regarding the analgesics being given on the day of drain removal, nor the timing of analgesic use in relation to the time of drain removal. Such information may have affected patients’ pain levels while removing drain.

Finally, patients with unsuccessful removal of drain at bedside were already excluded from the study before randomization. There appears to be a flaw in this methodology, as without pulling the drain one cannot know whether the drain removal is successful or not. Tethering or entrapment of drains is a known potential complication often encountered in clinical practice [2-5]. This maneuver may increase pain in such patients and thus cannot be recommended in all TKA patients.