A number of methods to reduce venipuncture (VP) pain have been developed to optimize patient comfort and satisfaction. Various local anesthetics (LA), ethyl chloride, ice, or even distraction have all decreased VP pain (1–4).
In traditional Chinese medicine, insertion and withdrawal of acupuncture needles during inspiration and expiration on command is claimed to reduce or reinforce the “vital energy” of the human body (5). Moreover, acupuncture performed simultaneously with this maneuver is almost painless. We have modified this procedure for VP without LA. The patients are asked to cough simultaneously with VP; this is called the “cough trick” (CT). To verify the effectiveness of CT for pain relief during peripheral VP, we performed a prospective, randomized, crossover volunteer study.
This study was approved by the local ethics committee. Twenty healthy (ASA physical status I) male volunteers 20–40 yr old were recruited from the staff of our clinic. They were told that the aim of the study was to compare the intensity of pain during VP with two different sizes of a new kind of indwelling venous catheter.
Because sex might influence pain sensitivity, female subjects were not included (6). The other exclusion criteria were chronic consumption of analgesics, anticoagulants, or antiplatelet drugs; sedative or alcohol abuse; history of peripheral neuropathy; abnormal skin conditions (infection, scars, psoriasis, or eczema) at the site of VP; and alcohol intake the evening before the study. Discontinuation criteria were unsuccessful VP and inflammation of the VP site. Because hypoglycemia accompanies various pain conditions or even aggravates pain, all the subjects were told to take a light breakfast before the VP (7,8). The study was always conducted in the same room between 7:00 and 10:00 am to minimize the influence of circadian differences on pain sensitivity (9).
To diminish situational anxiety, the subjects were asked to visit the study room before the VP session. During this first visit, the ear lobule was punctured to measure the initial serum glucose concentration and to make the subjects acquainted with the pain scoring on a 100-mm visual analog scale (VAS-100). On this scale, 0 mm indicates no pain, and 100 mm indicates the worst imaginable pain.
The subjects were randomly allocated into two groups depending on whether the VP would be performed first with the CT and 3 wk later without it (Group 1) or the other way around (Group 2). The first VP session took place at least 3 days after the primary examination. During that session, the subjects were placed in the supine position, and the tourniquet on the nondominant arm was fastened. After the vein to be punctured (on the dorsum of the hand) was clearly visualized, the subject was asked to turn his head in the direction opposite the side of the VP. Then they were asked to perform a single cough of moderate intensity without moving their arms. Immediately after, the subjects were asked to cough again. VP using a 20-gauge Insyte-W™ cannula was performed simultaneously with the second cough (CT during VP). In each subject, the same vein was punctured twice within 3 wk by the same investigator (“puncturer”), who was experienced in peripheral VP. None of the volunteers had heard about the CT. The CT procedure is our original method that has not been described in the literature. The effectiveness of blinding was verified by asking the volunteers after the second session whether they had any questions about the design of the study. The second investigator (“assessor”), who recorded the outcome measures, was blinded concerning whether the VP was performed with CT or without it and left the room before the moment of VP.
The subjects were asked to report the pain intensity at the moment of VP to the assessor when he came in and showed them the VAS scale. Serum glucose concentration, incidence of hand withdrawal, and palm sweating were also recorded after each VP. Heart rate was registered by means of pulse oximetry, and blood pressure was registered by means of oscillometry taken on the other arm 5 min before, immediately after, and 10 min after the VP and displayed and recorded on the monitor (M1276A; Hewlett-Packard, Palo Alto, CA).
Using the data of our pilot observational study, the number of subjects was set at 20 to ensure statistically significant results. The results of pain measurement on the VAS-100 were analyzed with the Wilcoxon signed rank test; normally distributed heart rate, blood pressure, and serum glucose concentration were analyzed with a Student’s paired t-test. Binary data (incidence of hand withdrawal and sweating) were analyzed with the χ2 test. P < 0.05 was considered statistically significant.
Twenty male volunteers (mean age, 29.2 ± 5.4 yr) were enrolled in and completed the study. The interview on the success of blinding revealed one subject who had doubts about the real purpose of the study and two who received VP with CT first and asked about the purpose of the coughing on command.
The intensity of pain on VP with the CT procedure was less than without it in 19 subjects (Fig. 1). Pain intensity in Group 1, which received the VP without CT first, was less at VP with CT (median VAS, 44 versus 24; P = 0.008). Pain intensity in Group 2, which received the VP with CT first, was also less at VP with CT (median VAS, 34 versus 47; P = 0.014). The intensity of pain in both groups taken together at VP with CT was less than without the CT procedure (median VAS, 31 versus 46; P < 0.001). Only one person reported increased pain intensity on VP with CT in comparison to without CT. In this subject, the serum glucose concentration was 2.2 mmol/L immediately after VP with CT (see the only descending dashed line in Fig. 1). Serum glucose concentration and incidence of hand withdrawal and sweating did not change throughout the study. Heart rate and blood pressure showed a tendency to decrease, although these changes were not statistically significant (Fig. 2).
Our aim was to test the effectiveness of the CT in the reduction of pain during VP in a randomized crossover study to justify its application in clinical practice. This technique is easily performed and not expensive, whereas the other methods of pain reduction for VP require additional efforts by the staff, and some of them (dermal analgesia with eutectic mixture of LAs [EMLA®] cream and jet injection of LA) produce additional costs (1,10). Moreover, EMLA provided sufficient local anesthesia only 90 minutes after application, whereas shorter application times made it ineffective (1,3).
We hesitate to explain the pain-reduction mechanism of CT with the Chinese theory of “energy” fluctuation because it does not offer any further possibility for verification of the causal chain. CT might be a sort of distraction at the moment of VP. Distraction is a well known cognitive method of pain reduction through the direction of attention to a nonnoxious stimulus in the immediate environment (11). However, the results of the studies on VP pain relief using distraction are controversial (4,12). The other potential mechanism that could explain our findings is an activation of the segmental pain-inhibitory pathways because of increased pressure in the subarachnoidal space during coughing. This mechanism was also suggested to explain the pain-relief effect of the counterirritation technique during subcutaneous lidocaine injection administered to alleviate pain of VP (13).
In conclusion, in this study the CT procedure was effective in VP pain reduction, although the mechanism remains unclear. Nevertheless, it is an easily performed and inexpensive method for reducing pain during VP in clinical practice.
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