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

Abstract

Background

Drain removal after TKA can be painful. Prior research suggests that the “cough trick,” in which a patient coughs at the same time she or he receives an injection, effectively decreases pain. To our knowledge, this intervention has not been evaluated as a way to reduce pain during other brief but painful interventions, such as removal of closed-suction drains after orthopaedic surgery.

Question/purpose

Does the cough trick reduce pain while a surgeon is removing a closed-suction drain after TKA?

Methods

Fifty-six patients with primary osteoarthritis who underwent primary TKA were randomized into two groups: drain removal as the patient coughed (n = 28 patients; three men, 25 women) or drain removal using the usual process, without the cough trick (n = 28 patients; three men, 25 women). The study groups were not different in terms of gender, BMI, surgical time, or other baseline variables, and other than the addition of the cough trick, there were no differences in surgical treatment or other elements of aftercare. Likewise, at baseline, the verbal numeric rating scale (VNRS) score for pain before the drain was removed was not different between the groups (3.1 ± 1.7 versus 3.3 ± 1.3; p = 0.72). The level of pain before and during drain removal was recorded using a VNRS by an orthopaedic surgeon who was not involved in the care of the study patients. We considered the minimum clinically important difference on the 10-point scale to be 2 points, based on prior evidence.

Results

The mean ± SD VNRS for the pain level during drain removal was lower in the cough trick group than that in the control group (1.6 ± 1.0 versus 3.7 ± 1.9, mean difference 2.1; 95% CI, 1.3-2.9; p < 0.001).

Conclusions

The cough trick during removal of a closed-suction drain tube in patients undergoing TKA reduced the level of pain in this small randomized trial. We suggest that surgeons consider this technique when removing drains after TKA because it is a noninvasive technique and it is easy to perform. Because the cough trick has been shown by others to be effective at reducing pain during venipuncture and parenteral injections, and we found it was effective for that purpose during drain removal after TKA, we believe this finding probably generalizes well to most minor procedures that cause transient, sharp pain. We suggest that it could be used to make such procedures more comfortable for patients, as well as for drain removal in other types of surgery where drains still are commonly used (including spine surgery and tumor surgery).

Level of Evidence

Level I, therapeutic study.

Introduction

Controlling pain after TKA improves patient satisfaction, is associated with shorter hospital stays, and allows for improved early knee range of motion [3, 6]. Many methods to control pain after TKA, including multimodal analgesia (such as a peripheral nerve blockade, local periarticular injection cocktail, and oral and intravenous medications) are commonly used [2, 7]. However, pain and discomfort during removal of surgical drains remains a problem when drains are used [10]. A reported method to decrease pain while removing the drain is injection of lidocaine through the skin around the drain tube [14]. However, this procedure is not popular because it is invasive. The injection is also painful and the pain may last longer than the drain removal procedure.

Some studies have reported that the “cough trick” decreases pain during procedures that cause transient, sharp pain, such as parenteral injections or venipuncture. In this technique, the patient is instructed to cough during the injection or venipuncture procedure [9, 11, 12]. There are many theories as to how this maneuver reduces pain, including distraction, stimulation of the autonomic nervous system (coughing is theorized to do this), and increased pressure in the subarachnoid space, which activates the segmental pain inhibition pathways [11]. However, to our knowledge, although the cough trick has been shown to be effective during venipuncture and injection [9, 11, 12], it has not been evaluated to reduce pain during other brief but painful interventions, such as removal of closed-suction drains after orthopaedic surgery. Although many surgeons no longer use drains after TKA [13], the practice persists in many parts of the world, and drains still are commonly used in other orthopaedic procedures, including spine surgery and tumor surgery. Thus, interventions to reduce pain during drain removal seem to be important. We hypothesized that patients who performed the cough trick during closed-suction drain removal would have less pain than patients who did not perform this maneuver.

We therefore asked, does the cough trick reduce pain while a surgeon is removing a closed-suction drain after TKA?

Patients and Methods

Study Design and Setting

This randomized controlled trial was conducted at a tertiary care hospital from July 16, 2018 to December 31, 2018. The trial was prospectively registered in the Thai Clinical Trials Registry under registration number TCTR20180716004.

The procedures in this study were performed in accordance with the Declaration of Helsinki’s ethical principles for medical research involving human participants. This study was approved by the local ethics committee and institutional review board.

Participants, Randomization, and Intention-to-Treat Analysis

Fifty-eight patients with primary osteoarthritis aged 50 years to 80 years who were scheduled to undergo unilateral primary TKA were approached for possible inclusion in this study. The exclusion criteria were previous knee surgery, communication problems, accidental self-removal of the suction drain, end-stage chronic renal disease, unsuccessful removal of the drain at bedside, or a patient who declined to participate. Two patients declined to participate, leaving 56 patients for randomization, all of whom were randomized, completed the trial, and were analyzed in the groups to which they were randomized (in other words, there was no difference between the intention-to-treat and per-protocol analyses in this study) (Fig. 1). Randomization was performed using a computer-generated sequence using blocks-of-four randomization as well as sealed, opaque envelopes, which were opened immediately before drain removal to minimize the likelihood of subversion of randomization. The sealed envelopes were opened at bedside immediately before the drains were removed. The research protocol was explained to the patients, and each provided signed informed consent.

Fig. 1.

A diagram of the study enrollment process is shown.

The 56 enrolled patients were randomly allocated into two groups. In the treatment group (defined as the cough trick group; n = 28; three men, 25 women), the drain was removed as the patient coughed. In those randomized to the control group (also n = 28; three men, 25 women), the drain was removed using the usual process, without the cough trick (Table 1).

Table 1.

Demographic data

Description of Experiment, Treatment, or Surgery

All TKA procedures were performed using a uniform surgical technique by one surgeon (VY). The medial parapatellar approach with lateral patellar subluxation and a cemented posterior stabilized total knee prosthesis was used in all patients. A pneumatic tourniquet was inflated throughout the operations. A suction drain tube (Redon-Drain, size: CH 08/2.5 mm, pfm medical mepro, Nonnweiler-Otzenhausen, Germany) with a vacuum bottle (Redon-Flasche, OP, 600 mL, pfm medical mepro, Nonnweiler-Otzenhausen, Germany) was placed in the joint before the capsule was closed, while the knee was in full extension. The drain exited 3 cm superior and 1 cm lateral to the superolateral corner of the patella. The exit site was located with a sterile ruler and marking pen when the knee was in full extension. The length of the tube that drained the knee joint was 12 cm. The knee capsule was closed with figure-eight sutures using Number 1 polyglactin 910. Buried knots with 3-0 polyglactin 910 were used for subcutaneous approximation. Adhesive strips were placed on the incision.

Aftercare and Experimental Intervention (Cough Trick)

Ankle pumping and early ROM exercises were started immediately after the operation. The patients were allowed to ambulate with a supportive device on the day after surgery. The suction drain was removed on postoperative day 2. Drains were removed from all patients by an orthopaedic surgeon (KI) who was not previously involved with patient care, and the drain removal process was explained to the patients before it was performed. During this procedure, the patient was asked to lie supine with the knee in full extension. The physician counted to three, and on the count of three, the drain was removed. Patients in the cough trick group were instructed to cough with moderate intensity on the count of three, and at that moment, the drain was removed. The same step was done by patients in the control group, without coughing.

Variables, Outcome Measures, Data Sources, and Bias

No differences were found between the groups in terms of age, gender, side of operation, weight, height, BMI, American Society of Anesthesiologists classification, percentages of patients with diabetes, or operative time (Table 1).

The levels of pain before and during drain removal were recorded with a verbal numeric rating scale (VNRS) score ranging from 0 (no pain) to 10 (worst-imaginable pain) [8]. All patients were evaluated by the same assessor (NM), who was blinded to the groups of patients by remaining outside the room. The assessor could hear neither the instructions given by the surgeon nor the patient cough when the surgeon removed the drain. Immediately after the drain was removed, the assessor was asked to enter the room to record the patient’s pain level.

At baseline, the VNRS score for pain before the drain was removed was not different between the groups (3.1 ± 1.7 in the cough trick group versus 3.3 ± 1.3 in the control group; p = 0.72).

Statistical Analysis, Study Size

Patient demographic data such as age, weight, height, BMI, operative time, VNRS score for the pain level before and during drain removal, and patient satisfaction were evaluated with a t-test. Pearson’s chi-square test was used to compare sex, side of operation, American Society of Anesthesiologists classification, and percentages of patients with diabetes. The analyses were performed with R version 3.1.0 software (R Foundation for Statistical Computing, Vienna, Austria). Statistical significance was assumed if p was < 0.05. The sample size was calculated based on the most relevant previous cough trick study [9] for testing two independent means. Twenty patients per group were required to detect a significance level of 0.01, and power was set at 0.9 to detect a difference of 2 points in the pain level during drain removal. We considered the minimum clinically important difference on the 10-point scale to be 2 points, based on prior evidence [4].

Results

The mean ± SD VNRS score for the pain level during drain removal was lower in the cough trick group than that in the control group (1.6 ± 1.0 versus 3.7 ± 1.9; mean difference 2.1; 95% CI, 1.3-2.9; p < 0.001) (Fig. 2).

Fig. 2.

This figure shows the mean VNRS score for pain before and during drain removal. VNRS = verbal numerical rating scale.

Discussion

In the cough trick method, the patient is asked to cough as a painful procedure is performed. Usichenko et al. [11] introduced this method in 2004. That study stated that the cough trick was a modification of a method used in acupuncture in Chinese medicine for inserting and withdrawing needles during inspiration and expiration. Many mechanisms for pain reduction using the cough trick have been reported [1, 5], including distraction (the process of changing a patient’s attention to a non-noxious stimulus while performing a procedure [5]) and increased pressure in the subarachnoid space while coughing, which activates the segmental pain inhibitory pathways [1]. We thought this method could be adapted from venipuncture or immunization to decrease pain while removing a suction drain tube postoperatively. We found that the cough trick reduced pain during drain removal.

This study had a number of limitations. First, the patients were not blinded to the purpose of the study or the method used because the cough trick required patient participation while the drain tube was removed. This may have caused patient bias or pre-removal expectations that the cough would help lower the level of pain. Second, this study did not blind the surgeon who removed the drains. However, the surgeon who removed the drains attempted to remove the drain tube using the same practice and steps, such as speed and direction, when pulling out the drain tube in all patients, and the individual who assessed the patients’ pain was blinded to the group allocation. Third, our study had a high percentage of women (89%). However, previous studies reporting that the cough trick had good efficacy had higher proportions of men (100%, 59%, and 43% in three prior studies) [9, 11, 12]. Therefore, we believe our findings are generalizable to men. Finally, the effect size of this study, although greater than the minimum clinically important difference, was not large (2 of 10 points on the VNRS pain scale). This was probably because the patients had little pain to begin with (only 3 of 10 points on the VNRS pain scale).

We found that the pain level during drain removal was lower in the cough trick group than that in the control group. A few studies using the cough trick found similar results. A randomized crossover volunteer study reported the effectiveness of the cough trick during venipuncture in 20 healthy volunteers at a 3-week interval [11]. The report stated that the intensity of pain was lower during venipuncture where the cough trick was used than during venipuncture where it was not used. Another randomized, controlled trial in 9- to 12-year-old children [9] also found that pain was less intense in children who used the cough trick during the venipuncture procedure than in those who did not use it. However, one randomized, controlled trial evaluated the cough trick during immunization in pre-kindergarten or pre-junior high school children and found that the cough trick was effective for participants who were Hispanic white or non-Hispanic white but not effective for non-Hispanic black participants [12]. The study hypothesized that people of different races had different pain perception, reports of pain, and coping with pain [12]. In our study, all patients were Asian.

In conclusion, we found that using the cough trick during drain tube removal after TKA reduced the level of pain that patients reported during the procedure. We believe that surgeons might consider using this technique while removing drains after TKA because it is noninvasive and easily performed. Although some orthopaedic surgeons do not use suction drains in TKA based on current evidence [13], we believe that because the cough trick has been shown to be effective in various minor procedures [9, 11, 12,] and because we found it reduced pain during drain removal after TKA, we believe the cough trick may be useful for drain removal in other types of surgery where drains are still commonly used (including spine surgery and tumor surgery). In light of our findings and prior evidence on this technique [9, 11, 12], we believe the cough trick may be helpful to reduce pain during other minor procedures that cause transient, sharp pain. Because it is not associated with any cost or known risks, we suggest that it could be used to make such procedures more comfortable for patients.