Venous cannulation, although a minor procedure, is often painful. The present study was planned to evaluate the efficacy of a diclofenac transdermal patch placed over the venepuncture site in decreasing the pain of cannulation. Seventy-two adults undergoing elective surgery were included in this randomised, prospective, double-blind, placebo-controlled study. Patients were divided into three equal groups. The Control group had a placebo adhesive patch placed on the both the dorsum of hand and the buttock; the Diclofenac-Buttock group had a placebo patch placed on the dorsum of the hand and a diclofenac transdermal patch on the buttock; the Diclofenac-Hand group had a diclofenac transdermal patch placed on the dorsum of hand and a placebo patch on the buttock. The patches were applied 1 h before cannulation. An 18G cannula was used for all venous cannulations. Pain during cannulation was assessed on a non-graduated 10-cm visual analogue scale. Median [interquartile range] pain scores were 3.0 [2.0–4.0] in the Diclofenac-Hand group, 5.0 [4.3–7.8] in the Diclofenac-Buttock group and 6.5 [4.5–7.0] in the Control group, p < 0.05. The numbers needed to treat were six and two in the Diclofenac-Buttock and Diclofenac-Hand groups, respectively. The application of a diclofenac transdermal patch at the cannulation site appears to be effective in decreasing cannulation pain.
Analgesia is an integral part of anaesthesia management. Venous cannulation is painful but is often performed without any analgesia. Cannulation pain has been ranked fifth out of 33 low-morbidity adverse clinical outcomes listed by expert anaesthetists when both clinical importance and frequency were considered . Various methods like application of local anaesthetic cream, ethyl chloride spray, distraction tactics, the ‘cough trick’ and the Valsalva manoeuvre during venous cannulation have been tried in the attempt to minimise pain, but with unreliable results [2–6].
The topical application of non-steroidal anti-inflammatory drugs (NSAIDs) has been reported to be effective in decreasing both acute and chronic pain . Application of NSAID gel to the venous cannulation site has been reported to decrease the incidence of thrombophlebitis  but a literature search did not reveal any study evaluating the efficacy of the application of a NSAID patch on venous cannulation pain. The present study was therefore planned to evaluate the efficacy of a diclofenac transdermal patch placed at the venepuncture site for attenuating cannulation pain.
After Local Research Ethics Committee approval and written, informed consent, 72 adult patients aged 16–60 years, ASA physical status I or II, of either sex, and scheduled for elective minor surgical procedures lasting < 1 h, were included in this prospective, randomised, double-blind, placebo-controlled study. The study was conducted during the period 1 January−26 July 2005. Presuming that therapy would decrease venepuncture pain by 30%, a power calculation with α = 0.05 and β = 0.8 suggested that we would need to enrol 24 patients into each group. Subjects taking NSAIDs regularly, those with an allergy or sensitivity to NSAIDs, communication problems, and abnormal skin conditions such as infection at the site of proposed venous cannulation, scars and eczema were excluded from the study.
Patients were randomly allocated to three equal groups of 24 with the help of a computer-generated table of random numbers. Members of the Control group had a placebo adhesive patch placed on both the dorsum of the non-dominant hand and on the right buttock. Members of the Diclofenac-Buttock group had a placebo patch placed on the dorsum of the non-dominant hand and a diclofenac transdermal patch placed on the right buttock. Members of the Diclofenac-Hand group had a diclofenac transdermal patch placed on the dorsum of the non-dominant hand and a placebo patch placed on the right buttock. Diclofenac transdermal patches (NuPatch 100, Zydus Cadila, Ahmedabad, India) contained diclofenac diethylamine BP 100 mg and had an absorption area of 50 cm2. The appearance of the placebo patches was identical and they were provided by the manufacturer of the diclofenac patches. All patches were applied by an anaesthetic trainee registrar (MK) not otherwise involved in the study 1 h before the patients were transferred to the operating theatre suite. The sites of patch application were cleaned with spirit before application of the patch. Just before each patient was transferred to the anaesthetic room, both patches were removed and the area marked on the dorsum of the hand where the patch had been by the trainee registrar (MK).
Another anaesthetic trainee (YCA), who was unaware of the patient's group allocation, cannulated a vein on the dorsum of the hand with an 18G cannula (Angiocath SPTM, Becton Dickinson Ltd, India) within the area previously covered by the patch. The patient assessed the pain of venous cannulation on a standard non-graduated 10-cm visual analogue scale (VAS).
All patients were observed for the first 24 h after surgery for blanching, erythema or swelling at the venepuncture site. Any patient whose veins could not be cannulated at the first attempt was excluded from further analysis. Age and weight were compared using analysis of variance (anova), and the Chi-squared test was used to analyse sex ratios. VAS data were analysed with the Mann–Whitney U-test and non-parametric analysis of variance. The software package SPSS 9.0 (SPSS Inc., Chicago, IL) was used for statistical analysis. A probability value < 0.05 was considered to be significant.
Seventy-one patients completed the study. The vein of one patient could not be cannulated at the first attempt and the patient was therefore excluded from further analysis. There were no significant differences between the groups with respect to age, weight and sex distribution (Table 1). The median [IQR] VAS scores in the Control, Diclofenac-Buttock and Diclofenac-Hand groups were 6.5 [4.5–7.0], 5.0 [4.3–7.8] and 3.0 [2.0–4.0], respectively (Fig. 1). The VAS score in the Diclofenac-Hand group was significantly lower than that in the other two groups (p < 0.05). No difference in the VAS scores was observed between the Diclofenac-Buttock and Control groups. In the Control group, all patients (23/23) reported venepuncture pain, a significantly higher proportion (p < 0.05) than in the Diclofenac-Buttock group (83%, 20/24) or the Diclofenac-Hand group (50%, 12/24). There was a significantly decreased incidence of venepuncture pain in the Diclofenac-Hand group compared with the Diclofenac-Buttock group (p < 0.05) (Table 2).
Table 1. Demographic data. Values are number or mean (SD).
Control Group (n = 24)
Diclofenac-ButtockGroup (n = 24)
Diclofenac-Hand Group (n = 24)
Sex; M : F
11 : 12
10 : 14
13 : 11
Table 2. Incidence of venepuncture pain in the three groups. Values are numbers. The proportion feeling pain in each group differs significantly from that in the other two groups (p < 0.05).
Control Group(n = 23)
Diclofenac-ButtockGroup (n = 24)
Diclofenac-Hand Group (n = 24)
Absolute and relative risk reduction in the Diclofenac-Buttock group was 17%, and the number needed to treat (NNT) was six. Absolute and relative risk reduction in the Diclofenac-Hand group was 50% and the NNT was two. None of the patients in any of the three groups suffered blanching, erythema or swelling at the venepuncture site.
The results of this study suggest that the application of a diclofenac transdermal patch at the venepuncture site 1 h before venous cannulation will decrease both the incidence and severity of cannulation pain. A diclofenac patch applied to the buttock decreased the incidence of cannulation pain but not its severity. Venepuncture, although a minor procedure, can be painful and frightening for the patient, and may therefore prove problematic for the anaesthetist. A painful experience during venepuncture might lead to significant negative consequences such as anxiety and adverse physiological responses during subsequent procedures .
Non-steroidal anti-inflammatory drugs are known to be effective analgesics. The benefits of topical administration of an NSAID are well established and offer the advantage of enhanced local drug delivery to affected tissues with a lower incidence of adverse systemic effects as a result of decreased plasma concentrations . The topical application of NSAID gel to the cannulation site has been reported to decrease the incidence of thrombophlebitis. However, the authors of that study did not evaluate its effect on venepuncture pain . The topical application of ibuprofen and piroxicam gel at the venepuncture site before cannulation has been reported as being ineffective in decreasing venepuncture pain [11, 12].
The use of a eutectic mixture of local anaesthetic (EMLA) cream is an effective method for the prevention of cannulation pain, but the vasoconstrictive effect of EMLA at the time of venous cannulation may be associated with blanching, and when the vasoconstrictive effect wears off, there is a generalised vasodilation, which may lead to erythema and swelling of the area of application . In our study, we did not find any blanching, erythema or swelling at the sites of application in any of the groups.
In conclusion, the application of a diclofenac patch at the venepuncture site 1 h before venous cannulation decreased both the incidence and severity of venepuncture pain, whereas a diclofenac patch applied to a buttock decreased the incidence of venepuncture pain but was ineffective in decreasing its severity. We therefore suggest that the application of a diclofenac patch at the cannulation site is a safe and effective method of decreasing both the incidence and severity of venepuncture pain.