Reducing the pain of local anesthetic infiltration: Warming and buffering have a synergistic effect1
Section snippets
INTRODUCTION
Local anesthetic agents, frequently used in the emergency department, can cause considerable discomfort during injection.1, 2 To decrease the discomfort of local anesthetic administration, it has been recommended that these agents be buffered before use.3, 4, 5, 6, 7 Recently, it has been suggested that warming these solutions to body temperature before use may be equally beneficial.8, 9 This study was conducted to compare the injection discomfort of room-temperature unbuffered lidocaine, warm
MATERIALS AND METHODS
The study was granted approval by the institutional review board. Volunteers were recruited from the ED staff and ancillary services. Participants were both male and female, ranging in age from 21 to 45 years. Exclusionary criteria included pregnancy, known allergy to local anesthetic agents, and poor general health. No compensation was offered.
Twelve hours before beginning our study, six sterile 30-mL multiple dose vials of 1% plain lidocaine HCl injectable were placed in our trauma room IV
RESULTS
The 32 subjects received a total of 128 injections (Figure 2). Mean pain scores are presented (Table). The first three mean pain scores are positive, indicating greater pain than the needle stick. The mean pain score for the fourth solution, however, is negative, indicating less pain.
Solution Mean 95% Confidence Intervals Room-temperature 5.5 —4.8, 15.8 Warmed 2.0 —11.1, 15.1 Buffered 1.1 —7.6, 9.8 Warmed/buffered
DISCUSSION
Lidocaine, an amide local anesthetic frequently used in the ED, is packaged and stored at an acidic pH to enhance stability and extend shelf life.2 Skin infiltration with lidocaine HCl for dermal procedures causes significant discomfort.1 Previous studies have determined that buffering lidocaine to a more neutral pH before use reduces the discomfort of infiltration.3, 4, 5, 6, 7 More recently, warming lidocaine to body temperature has been suggested as an equally effective method to attenuate
CONCLUSION
Based on our results, we conclude that warm buffered lidocaine is superior to room-temperature unbuffered lidocaine, warm lidocaine, and buffered lidocaine for reducing the pain of infiltration. The differences in mean pain scores, in fact, are so great as to suggest a synergistic effect. In an effort to make local anesthesia less painful and more acceptable to patients, we recommend the routine use of lidocaine that is both warm and buffered.
Acknowledgements
The authors thank the members of their department and ancillary staff for their participation in this study. They also thank their colleagues for their review of the manuscript and helpful suggestions.
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Reprint no. 47/1/53103