This is a prospective, randomized, double-blinded controlled trial comparing two different techniques for digital blocks. Participants will be physicians who perform digital blocks as part of their everyday duty. Each participant will undergo two digital blocks and will have the opportunity to perform a digital block on another participant.
This study follows a two-period cross-over design with four groups that are defined by the sequence of treatments within each group. Participants will receive two digital blocks, one using the traditional dorsal technique and one using the volar technique. Of the two injections, one of the syringes will contain 1% lidocaine without epinephrine and the other will contain sterile normal saline. The injections will be to the index finger on each hand. The hand injected first will be up to the participant. The order in which the dorsal technique versus the volar technique is performed will be randomized. Participants will not be told one of the syringes contains normal saline. Injection pain will be measured by visual analog score and recorded after each injection. Sensation in each of the 12 zones of the finger described by Cummings et al will be recorded at each minute mark until loss of sensation in all 12 zones is achieved or 15 minutes has passed, whichever comes first.
Set Up Prior to Study Performance Four-digit codes will be created for all participants. The 4-digit codes will be randomly assigned to a treatment group, A, B, C and D. Group A will undergo the volar technique first with lidocaine (V1) and then the dorsal technique second with sterile saline (D2). Group B will undergo the volar technique first with sterile saline and then undergo the second injection with the dorsal technique with lidocaine. Group C will undergo the dorsal technique first with lidocaine (D1) and then the volar technique second with sterile saline (V2). Group D will undergo the dorsal technique first with sterile saline followed by the volar technique second with lidocaine. Two syringes will be prepared for each 4-digit code, one with 4 mL of 1% lidocaine and 4 mL of sterile normal saline. They will be labelled with the four-digit code and a separate letter-digit code. The letter-digit code will contain one letter, either V or D, and one number, 1 or 2. The letter corresponds to the technique used to perform the injection (V for volar technique, D for traditional dorsal technique). The number corresponds to the order to which the syringe is to be used, first or second. Figure 1 shows a typical example of how a syringe will be labelled. In this example, participant 4883 in Group A would receive a syringe of lidocaine labelled 4883 V1 and a syringe of saline labelled 4883 D2. Each syringe will also be marked with an \* indicating lidocaine and a # indicating sterile saline. This is added to the syringes to immediately determine the syringe contents in case of adverse reaction. The meaning of the \* and # will not be shared with participants but will be known to all members of the study team.
Date of Study
An anonymous survey will be given to all participants with three questions:
1. Which technique do participants use for digital blocks?
2. How many mLs of lidocaine do participants use for digital block of one finger?
3. What specialty of medicine do participants practice? A ten-minute instructional demonstration will be performed demonstrating the volar injection technique and the traditional dorsal digital block technique as well as explaining the pain visual analog scale, the 12 zones of the finger, and how to record the data.
Participants will collect their two syringes with the same four-digit code. They will not be told that one syringe contains normal saline. Participants will then pair into groups of three. Within a group of three, each participant will be assigned the role of subject, injector, or recorder. The recorder will record the 4- digit number code at the top of the data sheet for the subject prior to injection. The injector will prep the base of the subject's index finger and perform the digital block in a sterile fashion using the technique indicated by letter on the syringe labeled 1. The recorder will start the timer. Pain on injection using the Visual Analog Score (VAS) will be recorded. Pinprick sensation will be tested in all 12 zones of the finger and recorded by the recorder at each minute mark up to 15 minutes or loss of sensation in all 12 zones, whichever comes first. The injector will then prep the base of the index finger on the subject's other hand and proceed with the second digital block using the technique corresponding to the letter on the syringe labelled 2. Again, pain on injection using the VAS will be recorded, pinprick sensation will be tested in all 12 zones of the finger and recorded by the recorder at each minute mark up to 15 minutes or loss of sensation in all 12 zones of the finger. Subject will then record which injection they prefer based on the pain on injection, not on the efficacy of technique at achieving loss of sensation. The participants will switch, so that the injector will become the subject, the recorder will become the injector, the subject will become the recorder, and the above-described procedure will be repeated. Then the participants will switch once more, and same procedure will be conducted a third and final time. If the injector in the final round has an insensate index finger, then an injector from another group with a sensate digit will perform the injections.
Participants may withdraw from the study at any time without prejudice to their training. Under certain circumstances the researchers may terminate the participant's participation in the study if: the participant is found to meet exclusion criteria, it is not in the participant's best interest to continue, or the study is stopped for any reason.
