Mechanisms of "Cough-Trick" for Pain Relief during Venipuncture: An Experimental Crossover Investigation in Healthy Volunteers

Abstract

Objectives: The easily performed "cough-trick" (CT) reduces pain during venipuncture (VP), although the underlying mechanism remains unclear. The aim was to investigate the pain-reducing effect of CT during VP in comparison with two distraction methods, as well as under the influence of naloxone.

Methods: 54 healthy male volunteers participated in 3 investigations. Pain during standardized VP with CT was compared to a "weak" distraction (squeezing a rubber ball; investigation 1; n=20) and to a "strong" distraction (inflating a tourniquet to a given pressure; investigation 2; n=21). In investigation 3 (n=13), pain at a VP without intervention was compared to pain at VP with CT under naloxone; pressure pain thresholds before and after naloxone administration were also measured. Pain was assessed using a 100 mm visual analogue scale. Data were compared within each sample using Student's t-test for paired samples.

Results: Pain intensity at VP with CT was lower than under "weak" distraction (mean difference 5 mm; 95% CI: 0.5 to 9.6; P=0.03). Pain levels under CT and "strong" distraction were comparable. There was no difference between pain under CT after naloxone infusion and pain without intervention. Pressure pain threshold decreased (mean difference 1 mm; 95% CI: 0.1 to 1.0 mm; P=0.02) after naloxone administration.

Conclusion: Pain-reducing effect of CT during VP is superior to that of simple motor distraction and equivalent to a complex distraction method. This might be due to the activation of segmental pain inhibitory pathways during coughing indicated through the lack of pain reduction due to CT under opioid antagonist blockage.

Figure 1

Study design of investigation 1 and investigation 2. Visit 1 was performed at least 3 days prior to the first session with venipuncture (VP) to acquaint subjects to the environment. During the following three weeks, participants performed two sessions in a randomized order with a VP that was accompanied by either a cough-trick (CT) or a distraction method.

Figure 2

Study design of investigation 3. Venipuncture (VP) without intervention was performed prior to the administration of nonselective opioid receptor antagonist naloxone (NX infusion). 30 minutes later, a second VP with a cough-trick (CT) under naloxone impact was performed. Pain intensity was assessed at both VPs and compared.

Figure 3

Time points of outcome measurement. Time point (I): measurement of heart rate (HR) and blood pressure (BP) 5 minutes before the venipuncture (VP). Time point II: assessment of pain intensity at VP on a 100 mm visual analogue scale (VAS-100); incidence of hand withdrawal; and HR, BP, and blood glucose (BG) directly after the VP. Time point III: measurement of heart rate and blood pressure 10 minutes after the VP.

Figure 4

Pain intensity during all conditions and investigations. Pain intensities at venipuncture (VP) were assessed on a 100 mm visual analogue scale (VAS-100). Normally distributed data from investigations 1 and 2 are presented as mean and standard error of the mean. Nonparametric data from investigation 3 median are presented as median, interquartile range, and minimum and maximum values for each condition; circles within the boxes are the mean values of pain intensity. Cough-trick (CT) was performed simultaneously to the VP. Weak distraction: participants squeezed a rubber ball with the nonpunctured hand during the VP procedure. Strong distraction: participants manually inflated the tourniquet, placed on the arm at which VP was performed, to a pressure of 200 mmHg and hold it attentively during VP. Without intervention: VP was performed without pain relief CT intervention prior to the administration of nonselective opioid receptor antagonist naloxone (NX). Cough-trick under NX: VP with CT was performed 30 minutes after naloxone infusion. ^∗P=0.03 for the comparison of cough-trick vs. weak distraction with Student's t-test for paired samples.