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RANDOMIZED TRIAL OF BUFFERED VERSUS PLAIN LIDOCAINE FOR LOCAL ANAESTHESIA IN OPEN CARPAL TUNNEL DECOMPRESSION
ARTICLE IN PRESS
RANDOMIZED TRIAL OF BUFFERED VERSUS PLAIN LIDOCAINE FOR LOCAL ANAESTHESIA IN OPEN CARPAL TUNNEL DECOMPRESSION A. C. WATTS, P. GASTON and G. HOOPER From the The Hand Unit, St John’s Hospital, Livingston, West Lothian, UK
We performed a randomized double-blind case–control study in 64 consecutive patients undergoing open carpal tunnel decompression under local anaesthetic to assess the pain experienced on injection of plain lidocaine (pH 6.4) compared with lidocaine buffered with sodium bicarbonate (pH 7.4). The results showed no statistical difference in the pain scores reported by patients. The mean pain scores for all patients were low, and most patients reported that they were ‘‘not at all anxious’’ about receiving a similar injection in the future. Journal of Hand Surgery (British and European Volume, 2004) 29B: 1: 30–31 Keywords: lidocaine, carpal tunnel
There was no difference in the appearance of the two solutions. Syringes were stored in a refrigerator after preparation but allowed to warm to room temperature before injection. In the anaesthetic room the solution was injected subcutaneously over a period of 1 minute into the palm of the hand using a 23 gauge hypodermic needle as described by Gale (1991). One minute after this and before application of the upper arm tourniquet, the patient was asked to score the level of pain felt on injection using a 100 mm visual analogue scale (Scott and Huskisson, 1976) and a four-point pain scale (‘‘no pain’’, ‘‘mild’’, ‘‘moderate’’, ‘‘severe’’). They were also asked to quantify how anxious they would be if they had to have the same injection again in the future (‘‘not at all’’, ‘‘mildly’’, ‘‘moderately’’, ‘‘severely’’). The operation was then carried out as usual. Using a power analysis based on the research of Christoph et al. (1988) who demonstrated a 4.5 times greater pain score on injection of plain lidocaine compared with buffered lidocaine, it was calculated that a minimum of 25 patients would be required in each arm of the trial given a statistical significance of 5% and power of 80%. Student’s t-test was used to analyse the results. As the data were skewed a log-normal transformation of the linear analogue pain scores was done. Correlation was tested using Pearson’s correlation coefficient.
INTRODUCTION Carpal tunnel decompression is routinely performed as an open procedure under local anaesthetic. Vossinakis (2001) identified three distinct causes for discomfort associated with the administration of the local anaesthetic before surgery: the introduction of the hypodermic needle; the acidity of the local anaesthetic solution; and increased tissue tension with the introduction of the local anaesthetic. It has been reported that altering the pH of lidocaine from an acidic solution to a solution with a pH equivalent to living tissue can significantly reduce the pain of injection (Bartfield et al., 1993; Christoph et al., 1988; Masters, 1998). We carried out a randomized double-blind prospective clinical study to test whether altering the acidity of the injected solution to normal tissue pH levels reduces the pain of local anaesthetic infiltration in patients undergoing open carpal tunnel decompression.
PATIENTS AND METHODS The study protocol was approved by the Lothian Regional Ethics Committee. All patients attending for open carpal tunnel decompression under local anaesthetic were invited to take part. On recruitment they were allocated a study number. Allocation of study numbers to the case or control group was performed by block randomization by the hospital pharmacy at the outset of the study. The hospital pharmacy provided syringes containing solutions of either buffered lidocaine (5 ml 2% plain lidocaine + 0.5 ml sodium bicarbonate 8.6%) or plain lidocaine (5 ml 2% plain lidocaine + 0.5 ml sodium chloride 0.9%) prepared on the day of operation. The pH values of the two solutions was 7.4 and 6.4, respectively. The syringes were labelled with the patient’s study number only, in order to blind the investigators to the nature of the solution used.
RESULTS Sixty-four consecutive consenting patients were recruited. There were 14 men and 50 women with a mean age of 57 (range, 28–89) years. There were equal numbers in each group. The mean (SD) pain score in the buffered group was 17.3 (2.7) on the visual analogue scale and 20.0 (2.3) for the plain lidocaine group. There was no statistical 30
ARTICLE IN PRESS
OPEN CARPAL TUNNEL DECOMPRESSION
difference between these results. Likewise there was no difference in the pain or anxiety scores of the two groups. Most patients (46/64) reported ‘‘no pain’’ or ‘‘mild’’ pain and most were ‘‘not at all’’ anxious (46/64) about similar injections in the future. In all patients, regardless of anaesthetic used, there was good correlation between the visual analogue and verbal pain scales (r=0.68, Po0.001). There was correlation between the level of pain and the anxiety score (r=0.48) which was statistically significant (Po0.001).
DISCUSSION Open carpal tunnel decompression under local anaesthesia is well tolerated by patients (Baguneid et al., 1997). In our experience patients do not complain of discomfort from the operation itself but more often of discomfort from the upper arm tourniquet and from infiltration of the local anaesthetic. Some authors have observed that the procedure can be performed with the hand elevated (Cole, 1998) or using lidocaine with adrenaline (Braithwaite et al., 1993) to avoid the use of a tourniquet. The pain of skin puncture with the hypodermic needle, as Vossinakis (2001) pointed out, is not significant if a small (23 gauge) needle is used. Avramidis et al. (2000) recommended application of topical local anaesthetic cream an hour before surgery. However this can be impractical in a day case list and is also expensive. Injecting the anaesthetic solution more slowly into the palm reduces pain caused by increased tissue tension. Vossinakis (2001) also identified the acidity of the local anaesthetic solution as a further contributary factor for pain. Amide anaesthetics such as lidocaine are unstable in alkaline environments and are therefore commercially produced as acidic solutions to prolong their shelf-life (Bartfield et al., 1992). Raising the pH of lidocaine to near body pH reduces the pain experienced at the time of infiltration in healthy volunteers (Bartfield et al., 1993) and in patients receiving ring block digital anaesthetics (Christoph et al., 1988). However, we found no such reduction in pain scores when buffered lidocaine was injected into the palm for carpal tunnel decompression. Our results indicate that the pain of injection is not actually a major problem for most patients undergoing
31
carpal tunnel decompression and there is no benefit in injecting buffered lidocaine. The pain scores for both groups were low and most patients reported that they were ‘‘not at all’’ anxious about having a similar injection again in the future. We did however note a correlation between increased pain score and increased anxiety about future injections.
Acknowledgements We thank Lynn Bennet, Clinical Trial Pharmacist, St John’s Hospital, for her help with this project.
References Avramidis K, Lewis JC, Gallagher P (2000). Reduction in pain associated with open carpal tunnel decompression. Journal of Hand Surgery, 25B: 147–149. Baguneid MS, Sochart DH, Dunlop D, Kenny NW (1997). Carpal tunnel decompression under local anaesthetic and tourniquet control. Journal of Hand Surgery, 22B: 322–324. Bartfield JM, Ford DT, Homer PJ, Sternklar P (1992). Buffered lidocaine as a local anaesthetic: an investigation of shelf life. Annals of Emergency Medicine, 21: 16–19. Bartfield JM, Ford DT, Homer PJ (1993). Buffered versus plain lidocaine for digital nerve blocks. Annals of Emergency Medicine, 22: 216–219. Braithwaite BD, Robinson GJ, Burge PD (1993). Haemostasis during carpal tunnel release under local anaesthesia: a controlled comparison of a tourniquet and adrenaline infiltration. Journal of Hand Surgery, 18B: 184–186. Christoph RA, Buchanan L, Begalia K, Schwartz S (1988). Pain reduction in local anaesthetic administration through pH buffering. Annals of Emergency Medicine, 17: 117–120. Cole RP (1998). Re: carpal tunnel decompression under local anaesthetic and tourniquet control (letter). Journal of Hand Surgery, 23B: 561. Gale DW (1991). Surgical decompression of the carpal tunnel using infiltrative anaesthesia: description of technique. Journal of the Royal College of Surgeons of Edinburgh, 36: 341. Masters JE (1998). Randomized control trial of pH buffered lignocaine with adrenaline in outpatient operations. British Journal of Plastic Surgery, 51: 385–387. Scott J, Huskisson EC (1976). Graphic representation of pain. Pain, 2: 175–184. Vossinakis IC (2001). Re: reduction in pain associated with open carpal tunnel decompression (letter). Journal of Hand Surgery, 26B: 503–504.
Received: 16 April 2003 Accepted after revision: 4 August 2003 G. Hooper, FRCS, Consultant Hand and Orthopaedic Surgeon, St John’s Hospital, Howden Road West, Livingston, West Lothian, EH54 6PP, UK. Tel.: +44-1506-419666; fax: +441506-460592; E-mail: [email protected] r 2003 The British Society for Surgery of the Hand. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.jhsb.2003.08.006 available online at http://www.sciencedirect.com
RANDOMIZED TRIAL OF BUFFERED VERSUS PLAIN LIDOCAINE FOR LOCAL ANAESTHESIA IN OPEN CARPAL TUNNEL DECOMPRESSION A. C. WATTS, P. GASTON and G. HOOPER From the The Hand Unit, St John’s Hospital, Livingston, West Lothian, UK
We performed a randomized double-blind case–control study in 64 consecutive patients undergoing open carpal tunnel decompression under local anaesthetic to assess the pain experienced on injection of plain lidocaine (pH 6.4) compared with lidocaine buffered with sodium bicarbonate (pH 7.4). The results showed no statistical difference in the pain scores reported by patients. The mean pain scores for all patients were low, and most patients reported that they were ‘‘not at all anxious’’ about receiving a similar injection in the future. Journal of Hand Surgery (British and European Volume, 2004) 29B: 1: 30–31 Keywords: lidocaine, carpal tunnel
There was no difference in the appearance of the two solutions. Syringes were stored in a refrigerator after preparation but allowed to warm to room temperature before injection. In the anaesthetic room the solution was injected subcutaneously over a period of 1 minute into the palm of the hand using a 23 gauge hypodermic needle as described by Gale (1991). One minute after this and before application of the upper arm tourniquet, the patient was asked to score the level of pain felt on injection using a 100 mm visual analogue scale (Scott and Huskisson, 1976) and a four-point pain scale (‘‘no pain’’, ‘‘mild’’, ‘‘moderate’’, ‘‘severe’’). They were also asked to quantify how anxious they would be if they had to have the same injection again in the future (‘‘not at all’’, ‘‘mildly’’, ‘‘moderately’’, ‘‘severely’’). The operation was then carried out as usual. Using a power analysis based on the research of Christoph et al. (1988) who demonstrated a 4.5 times greater pain score on injection of plain lidocaine compared with buffered lidocaine, it was calculated that a minimum of 25 patients would be required in each arm of the trial given a statistical significance of 5% and power of 80%. Student’s t-test was used to analyse the results. As the data were skewed a log-normal transformation of the linear analogue pain scores was done. Correlation was tested using Pearson’s correlation coefficient.
INTRODUCTION Carpal tunnel decompression is routinely performed as an open procedure under local anaesthetic. Vossinakis (2001) identified three distinct causes for discomfort associated with the administration of the local anaesthetic before surgery: the introduction of the hypodermic needle; the acidity of the local anaesthetic solution; and increased tissue tension with the introduction of the local anaesthetic. It has been reported that altering the pH of lidocaine from an acidic solution to a solution with a pH equivalent to living tissue can significantly reduce the pain of injection (Bartfield et al., 1993; Christoph et al., 1988; Masters, 1998). We carried out a randomized double-blind prospective clinical study to test whether altering the acidity of the injected solution to normal tissue pH levels reduces the pain of local anaesthetic infiltration in patients undergoing open carpal tunnel decompression.
PATIENTS AND METHODS The study protocol was approved by the Lothian Regional Ethics Committee. All patients attending for open carpal tunnel decompression under local anaesthetic were invited to take part. On recruitment they were allocated a study number. Allocation of study numbers to the case or control group was performed by block randomization by the hospital pharmacy at the outset of the study. The hospital pharmacy provided syringes containing solutions of either buffered lidocaine (5 ml 2% plain lidocaine + 0.5 ml sodium bicarbonate 8.6%) or plain lidocaine (5 ml 2% plain lidocaine + 0.5 ml sodium chloride 0.9%) prepared on the day of operation. The pH values of the two solutions was 7.4 and 6.4, respectively. The syringes were labelled with the patient’s study number only, in order to blind the investigators to the nature of the solution used.
RESULTS Sixty-four consecutive consenting patients were recruited. There were 14 men and 50 women with a mean age of 57 (range, 28–89) years. There were equal numbers in each group. The mean (SD) pain score in the buffered group was 17.3 (2.7) on the visual analogue scale and 20.0 (2.3) for the plain lidocaine group. There was no statistical 30
ARTICLE IN PRESS
OPEN CARPAL TUNNEL DECOMPRESSION
difference between these results. Likewise there was no difference in the pain or anxiety scores of the two groups. Most patients (46/64) reported ‘‘no pain’’ or ‘‘mild’’ pain and most were ‘‘not at all’’ anxious (46/64) about similar injections in the future. In all patients, regardless of anaesthetic used, there was good correlation between the visual analogue and verbal pain scales (r=0.68, Po0.001). There was correlation between the level of pain and the anxiety score (r=0.48) which was statistically significant (Po0.001).
DISCUSSION Open carpal tunnel decompression under local anaesthesia is well tolerated by patients (Baguneid et al., 1997). In our experience patients do not complain of discomfort from the operation itself but more often of discomfort from the upper arm tourniquet and from infiltration of the local anaesthetic. Some authors have observed that the procedure can be performed with the hand elevated (Cole, 1998) or using lidocaine with adrenaline (Braithwaite et al., 1993) to avoid the use of a tourniquet. The pain of skin puncture with the hypodermic needle, as Vossinakis (2001) pointed out, is not significant if a small (23 gauge) needle is used. Avramidis et al. (2000) recommended application of topical local anaesthetic cream an hour before surgery. However this can be impractical in a day case list and is also expensive. Injecting the anaesthetic solution more slowly into the palm reduces pain caused by increased tissue tension. Vossinakis (2001) also identified the acidity of the local anaesthetic solution as a further contributary factor for pain. Amide anaesthetics such as lidocaine are unstable in alkaline environments and are therefore commercially produced as acidic solutions to prolong their shelf-life (Bartfield et al., 1992). Raising the pH of lidocaine to near body pH reduces the pain experienced at the time of infiltration in healthy volunteers (Bartfield et al., 1993) and in patients receiving ring block digital anaesthetics (Christoph et al., 1988). However, we found no such reduction in pain scores when buffered lidocaine was injected into the palm for carpal tunnel decompression. Our results indicate that the pain of injection is not actually a major problem for most patients undergoing
31
carpal tunnel decompression and there is no benefit in injecting buffered lidocaine. The pain scores for both groups were low and most patients reported that they were ‘‘not at all’’ anxious about having a similar injection again in the future. We did however note a correlation between increased pain score and increased anxiety about future injections.
Acknowledgements We thank Lynn Bennet, Clinical Trial Pharmacist, St John’s Hospital, for her help with this project.
References Avramidis K, Lewis JC, Gallagher P (2000). Reduction in pain associated with open carpal tunnel decompression. Journal of Hand Surgery, 25B: 147–149. Baguneid MS, Sochart DH, Dunlop D, Kenny NW (1997). Carpal tunnel decompression under local anaesthetic and tourniquet control. Journal of Hand Surgery, 22B: 322–324. Bartfield JM, Ford DT, Homer PJ, Sternklar P (1992). Buffered lidocaine as a local anaesthetic: an investigation of shelf life. Annals of Emergency Medicine, 21: 16–19. Bartfield JM, Ford DT, Homer PJ (1993). Buffered versus plain lidocaine for digital nerve blocks. Annals of Emergency Medicine, 22: 216–219. Braithwaite BD, Robinson GJ, Burge PD (1993). Haemostasis during carpal tunnel release under local anaesthesia: a controlled comparison of a tourniquet and adrenaline infiltration. Journal of Hand Surgery, 18B: 184–186. Christoph RA, Buchanan L, Begalia K, Schwartz S (1988). Pain reduction in local anaesthetic administration through pH buffering. Annals of Emergency Medicine, 17: 117–120. Cole RP (1998). Re: carpal tunnel decompression under local anaesthetic and tourniquet control (letter). Journal of Hand Surgery, 23B: 561. Gale DW (1991). Surgical decompression of the carpal tunnel using infiltrative anaesthesia: description of technique. Journal of the Royal College of Surgeons of Edinburgh, 36: 341. Masters JE (1998). Randomized control trial of pH buffered lignocaine with adrenaline in outpatient operations. British Journal of Plastic Surgery, 51: 385–387. Scott J, Huskisson EC (1976). Graphic representation of pain. Pain, 2: 175–184. Vossinakis IC (2001). Re: reduction in pain associated with open carpal tunnel decompression (letter). Journal of Hand Surgery, 26B: 503–504.
Received: 16 April 2003 Accepted after revision: 4 August 2003 G. Hooper, FRCS, Consultant Hand and Orthopaedic Surgeon, St John’s Hospital, Howden Road West, Livingston, West Lothian, EH54 6PP, UK. Tel.: +44-1506-419666; fax: +441506-460592; E-mail: [email protected] r 2003 The British Society for Surgery of the Hand. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.jhsb.2003.08.006 available online at http://www.sciencedirect.com