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Analgesia for venous cannulation by subcutaneous infiltration: effect of lidocaine concentration

Tiwari, A.; Chawla, R.; Kumar, M.

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European Journal of Anaesthesiology: December 2006 - Volume 23 - Issue 12 - p 1063-1064
doi: 10.1017/S0265021506231697


Venous cannulation is the most common invasive procedure performed in clinical practice which is associated with pain and anxiety. Various methods have been investigated to alleviate pain due to venous cannulation. Lidocaine infiltration is the most commonly used technique. The present study was designed to determine the minimum effective concentration of lidocaine that is effective on subcutaneous infiltration for pain relief of venous cannulation.

The Institutional Ethics Committee approved the study, and written informed consent was obtained from all the patients. One hundred and twenty ASA I–II adult patients of either sex undergoing elective surgery under general anaesthesia were included in this study. All patients were visited on the day before surgery, and were introduced to the concept of a 100 point visual analogue scale (VAS) with 0 implying ‘No pain’ and 100 being the ‘Worst possible pain’. They were premedicated with diazepam 10 mg orally on the night before surgery and 5 mg on the morning of surgery. The patients were randomly allocated to four different groups of 30 each that were labelled as L-0.25%, L-0.5%, L-1% and L-2% on the basis of increasing concentration of lidocaine (Xylocaine® 2%; AstraZeneca Pharma India Limited, Bangalore, India). While patients in group L-0.25% received a lidocaine in concentration of 0.25% those in L-0.5%, L-1% and L-2% groups received 0.5%, 1% and 2%, respectively. Each patient received a 0.5-mL subcutaneous injection of lidocaine in the dorsum of one hand 3 min prior to the insertion of an 18-G cannula. In the dorsum of the contralateral hand, which served as the control, no infiltration was given, and an 18-G cannula was inserted without any local infiltration after routine skin preparation. The group and hand allocation as regards subcutaneous infiltration was randomized by draw of lots. Subcutaneous infiltration was given using a 26-G needle with an insulin syringe close to the site of proposed venous cannulation. The observer (RC) assessing the pain on cannulation was blinded to the group. The patients were asked to grade their pain of cannulation in the two hands. Pain score for cannulation without infiltration was recorded as P-0. On the arm where infiltration was given, pain on subcutaneous infiltration of lidocaine and pain on cannula insertion at the infiltration site were recorded as P-1 and P-2, respectively. The data were statistically analysed by using multivariate analysis and Tukey's test.

The patients of all four groups were statistically comparable for age, weight (P > 0.05) and sex distribution. Visual analogue score for pain in different groups at different interventions is shown in Table 1. VAS score on direct cannulation without infiltration of lidocaine (P-0) was comparable among all four groups (P > 0.05) but significantly higher when compared with pain of infiltration (P-1) and pain of cannulation after infiltration (P-2) of respective groups, in all four groups (P < 0.01). Statistical analysis revealed that there was no significant difference between P-1 and P-2 in groups L-0.5%, L-1% and L-2% (P > 0.05). However, in group L-0.25%, P-2 was significantly higher (VAS: 22 ± 26) than P-1 (VAS: 10 ± 10) (P < 0.01), though still much lower than P-0 (VAS: 48 ± 26) in the same group. On comparison of VAS between the groups P-1 and P-2 were comparable (P > 0.05) (Table 1). In over 80% of patients in all four groups, pain of infiltration of local anaesthetic was negligible (VAS 0–20). Further, on cannulation after infiltration, negligible pain (VAS 0–20) was observed in 67% patients of group L-0.25%, 73% patients of group L-0.5%, 80% patients of group L-1% and 83% patients of group L-2%. Thus, increasing concentrations of lidocaine is associated with higher percentage of patients having negligible pain score.

Table 1
Table 1:
Pain score assessed on VAS (mean ± SD) in all four groups at different points of intervention.

Venous cannulation is a painful experience and may provoke significant stress. Pain relief of cannulation has been achieved by various techniques. Lidocaine infiltration is the most commonly employed technique. It has been used in various concentrations, volume, with iontophoresis [{L-End} 1], modifications in pH [{L-End} 2] and temperature [{L-End} 3]. New means of administration like jet injectors have been tried to alleviate pain of cannulation [{L-End} 4]. The present study was designed to determine the minimum effective concentration of lidocaine that is effective for alleviating pain of intravenous (i.v.) cannulation. Questionnaire-based studies have revealed that anaesthetists use local anaesthesia for cannulae of 18-G or larger [{L-End} 5]. So in the present study, 18-G cannula was used to assess pain of cannulation.

The results of the present study revealed a significant reduction in pain on cannulation after infiltration of lidocaine in concentrations as low as 0.25% (VAS: 22 ± 26) when compared to cannulation without infiltration (VAS: 48 ± 26). Further, with an increase in concentration of lidocaine above 0.25%, there was lower VAS score, thereby suggesting that there was an improvement in pain relief on cannulation. It was also observed that by increasing the concentration of lidocaine, larger percentage of patients was benefited and had negligible pain as shown by significantly lower VAS score on cannulation. Thus, while 0.25% lidocaine is the minimum effective dose, increasing concentrations increases the analgesic efficacy for cannulation. VAS score on cannulation after infiltration (P-2) was significantly lower than VAS score on cannulation without infiltration (P-0) (P < 0.01), but comparable to VAS score on infiltration (P-1) in all groups except group L-0.25 where P-2 was higher than P-1. While infiltration was accompanied with local swelling, it did not alter the success of venous cannulation in first attempt. Contrary to results by Rohm and colleagues [{L-End} 6] where infiltration was seen to be beneficial only for 16-G cannula or less, the present study shows effectiveness with 18-G cannula insertion.

In summary, this study shows that subcutaneous infiltration with lidocaine in concentrations as low as 0.25% alleviates pain of i.v. cannulation. Further, while 0.25% lidocaine is the minimum effective dose, increasing concentrations increases the analgesic efficacy for cannulation.


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© 2006 European Society of Anaesthesiology