Buffering Lidocaine
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Masters JE
Randomised control trial of pH buffered lignocaine with adrenaline in
outpatient operations
Br J Plast Surg 1998; 51 385-7

Bicarbonate buffering of local anaesthetics is known to significantly
decrease the pain of their administration and yet few practising
surgeons do so. A double-blind randomised cross-over clinical trial was
conducted to confirm the practicality and efficacy of bicarbonate
buffering of lignocaine with adrenaline in the setting of a busy local
anaesthetic operating theatre. 40 patients received either buffered or
control local anaesthetic solutions in equivalent sites on opposite
sides of the body. The pain of each injection was rated from 0 (no pain)
to 10 (extreme pain). The mean pain score for the buffered solution was
significantly lower than the control solution (3.06 vs 4.34, P = 0.002).
Bicarbonate buffering of lignocaine with adrenaline is effective,
inexpensive and simple; its widespread use should be encouraged.

Colaric KB, Overton DT, Moore K
Pain reduction in lidocaine administration through buffering and warming
Am J Emerg Med 1998; 16 353-6

This study compared the pain from intradermal infiltration of (1) plain
lidocaine, (2) warmed lidocaine, (3) buffered lidocaine, and (4) warmed,
buffered lidocaine. A randomized, double-blind, Latin Square design of
20 volunteers was used. Each volunteer was injected with a series of
four test solutions on four separate occasions, for 16 total injections
each. Each volunteer served as his or her own control. The mean pain
scores for the four solutions were: 44.2 for plain lidocaine, 42.2 for
warmed lidocaine, 36.7 for buffered lidocaine, and 29.2 for warmed,
buffered lidocaine. Buffered lidocaine was statistically less painful
than both plain lidocaine and warmed lidocaine. Warmed, buffered
lidocaine was significantly less painful than all other solutions,
including buffered lidocaine (P .005). However, warmed lidocaine did not
yield pain scores significantly different from plain lidocaine. In this
experimental model, warmed lidocaine was not superior to plain
lidocaine, but warmed, buffered lidocaine caused significantly less pain
than plain lidocaine, buffered lidocaine, or warmed lidocaine. Thus,
there may be benefit from heating the buffered lidocaine now in common
clinical use.

Scarfone RJ, Jasani M, Gracely EJ
Pain of local anesthetics: rate of administration and buffering
Ann Emerg Med 1998; 31 36-40

STUDY OBJECTIVE: To determine the impact of administration rate and
buffering on the pain associated with subcutaneous infiltration of
lidocaine. METHODS: Forty-two adult volunteers employed at a tertiary
care center participated in this prospective, single-blinded study. Each
subject received four lidocaine injections prepared and administered as
follows: slow, buffered (SB); slow, unbuffered (SU); rapid, buffered
(RB); rapid, unbuffered (RU). Buffering was accomplished by mixing 1%
lidocaine with 8.4% sodium bicarbonate in a 9:1 ratio. Slow
administration was 30 seconds and rapid was 5 seconds. Needle size
(27-gauge), injection depth (.25 inch), lidocaine volume (1.0 mL), and
temperature (room) were the same for each of the four injections. In all
four conditions, the needle remained in the forearm for 30 seconds, to
ensure blinding. The main outcome measure was the mean pain score for
each condition, as recorded on a 10-cm visual analog scale. RESULTS: The
lowest pain scores (mean +/- SE) were recorded for the SU and SB
conditions at 1.49 +/- 29 and 1.48 +/- 26, respectively, and they were
significantly lower than the scores for RB (2.34 +/- 28; P .01) or RU
(3.11 +/- 33; P .001). Each of the slow conditions was reported to be
the "least painful" of the four significantly more often than either
rapid condition. CONCLUSION: This is the largest blinded study to assess
administration rate and the pain of a local anesthetic. We found that
administration rate had a greater impact on the perceived pain of
lidocaine infiltration than did buffering.

Nelson AL
Neutralizing pH of lidocaine reduces pain during Norplant system insertion
procedure
Contraception 1995; 51 299-301

The acidity of lidocaine used as a local anesthetic during the insertion
of Norplant System capsules can cause patient discomfort. Buffering
lidocaine with sodium bicarbonate significantly reduced pain scores
reported by 46 women who participated in this randomized, double- blind
study. Derived from a pain scale of 1 to 10, the mean difference in
reported pain scores with and without buffering was 1.17 (P = 0.0098)
with women using themselves as controls, for an average reduction in
pain of 29%. Because this added step minimized patient discomfort, it
might make the Norplant System a more attractive option for women
apprehensive about insertion pain

Richtsmeier AJ, Hatcher JW
Buffered lidocaine for skin infiltration prior to hemodialysis
J Pain Symptom Manage 1995; 10 198-203

This study compared the effects of buffered versus unbuffered lidocaine
when used as local anesthetic in preparation for cannulation of the
arterial and venous sites of children requiring hemodialysis. The
subjects for this study were seven children, ages 6-18 years, observed
during 101 dialysis treatments. For each subject undergoing hemodialysis
on a given day, one syringe containing 1% lidocaine (L) and one
containing buffered lidocaine (BL) were prepared. The BL solution was
prepared by adding 2 mL of 8.4% sodium bicarbonate to 20 mL of 1%
lidocaine just prior to use. The choice of local anesthetic used for
cannulation of the arterial or venous site was randomly assigned to be
either L or BL. Nurses, raters, and subjects were blind to contents of
the syringe. The procedures for piercing the skin, pausing, and
infiltrating were standardized, as was the volume administered. Speed of
injection was not controlled. Comparisons of self-reported pain and
behavioral observations for L versus BL revealed no significant
differences for pain of infiltration or pain of cannulation. Technique
variables such as the speed of injection, which tended to be very slow
for these children, appear to significantly influence infiltration pain
and the relative merits of buffering.

Doolan KL
Buffering lidocaine with sodium bicarbonate
Am J Hosp Pharm 1994; 51 2564-5

10.
Mader TJ, Playe SJ, Garb JL
Reducing the pain of local anesthetic infiltration: warming and buffering have
a synergistic effect
Ann Emerg Med 1994; 23 550-4

STUDY OBJECTIVE: To compare room-temperature unbuffered lidocaine, warm
lidocaine, buffered lidocaine, and warm buffered lidocaine to determine
which of the four solutions is least painful during infiltration.
DESIGN: Randomized, controlled, double-blinded, volunteer study. TYPE OF
PARTICIPANT: Thirty-two young healthy adults. MAIN RESULTS: Each subject
received four subcutaneous injections of 1% lidocaine: room- temperature
unbuffered, warm, buffered, and warm buffered. After each injection,
participants recorded their perception of pain associated with
infiltration of the solution on a visual analog scale. Mean pain scores
for the four solutions were determined and analyzed. The mean perceived
pain score for the warm buffered solution was significantly lower than
for any of the other solutions (versus warm: P = .0005; versus buffered:
P = .0028; versus room temperature: P = .0001). There was no
statistically significant difference between either the warm solution or
buffered solution and the room-temperature unbuffered lidocaine. The
difference in mean pain score for the warm buffered solution, compared
with those for the warm, buffered, and room- temperature solutions,
suggests that warming and buffering have a synergistic effect.
CONCLUSION: Skin infiltration with warm buffered lidocaine is
significantly less painful than infiltration with room- temperature
unbuffered lidocaine, warm lidocaine, or buffered lidocaine.

Matsumoto AH, Reifsnyder AC, Hartwell GD, et al.
Reducing the discomfort of lidocaine administration through pH buffering
J Vasc Interv Radiol 1994; 5 171-5

PURPOSE: A prospective, double-blind study was undertaken to evaluate
the effect of using a buffered lidocaine solution on the perception of
pain experienced by a patient during its intradermal injection. PATIENTS
AND METHODS: One hundred fifty patients undergoing diagnostic
angiographic and interventional procedures at the authors' institution
were randomly assigned to receive a 1-mL aliquot of one of three
lidocaine solutions: plain 1% lidocaine, 1% lidocaine diluted with
normal saline in a 10:1 ratio, and 1% lidocaine diluted with 8.4% sodium
bicarbonate in a 10:1 ratio. The lidocaine solutions were administered
intradermally over 10-15 seconds. A numerical value was placed on the
patient's perception of pain, separate from that associated with the
25-gauge needle insertion, with use of a linear visual analog scale.
RESULTS: Mean pain scores were as follows: for the 1% lidocaine
solution, 2.83 +/- 2.60; for 1% lidocaine plus normal saline solution,
2.89 +/- 2.34; and for 1% lidocaine plus sodium bicarbonate solution,
1.37 +/- 1.73 (P = .0018). CONCLUSION: Buffering lidocaine significantly
decreased the discomfort associated with its administration as a local
anesthetic.

Metzinger SE, Bailey DJ, Boyce RG, Lyons GD
Local anesthesia in rhinoplasty: a new twist?
Ear Nose Throat J 1992; 71 405-6

Twenty volunteers were asked to compare pain upon injection during
septorhinoplasty using buffered versus unbuffered local anesthetics. The
concentration of the buffer was one part sodium bicarbonate to five
parts local. The surgeons performing the operation were asked to
identify any difference in hemostasis or duration of anesthesia.
Eighteen of twenty patients found the buffered anesthetic to be less
painful and better tolerated. No difference in hemostasis or duration of
action was noted between the buffered or unbuffered solution, however,
faster onset of action was noted with the buffered solution. The
addition of sodium bicarbonate as a buffering agent to the local
anesthetics lidocaine and bupivacaine can significantly reduce pain upon
injection. A solution of 5cc 2% lidocaine with 1:100,000 epinephrine,
5cc 0.25% bupivacaine with 1:200,000 epinephrine, and 2cc of 7.5% sodium
bicarbonate mixed just prior to injection is a safe, effective, less
painful local anesthetic with rapid onset of action and full efficacy.

Bancroft JW, Benenati JF, Becker GJ, Katzen BT, Zemel G
Neutralized lidocaine: use in pain reduction in local anesthesia [published
erratum appears in J Vasc Interv Radiol 1992 May;3(2):394]
J Vasc Interv Radiol 1992; 3 107-9

The effect of pH neutralization on the pain experienced during
intradermal lidocaine administration was investigated in a prospective
blind study of 20 adult volunteers. A plain solution (pH congruent to
6.1) and three different buffered solutions of 1% lidocaine (pH values
of 6.8, 7.0, and 7.2) were prepared, and a 0.5-mL intradermal injection
of each was administered to the volar aspect of the forearm. Pain
associated with lidocaine infiltration was rated with a linear visual
analogue scale. Solutions with a pH of less than 6.8 (unbuffered
lidocaine in this study) predictably produced a burning pain sensation
on injection. However, buffering of 1% lidocaine above a pH of 6.8
significantly (P less than .05) reduced the mean quantitative pain
estimates compared with the nonbuffered controls.

Sapin P, Petrozzi R, Dehmer GJ
Reduction in injection pain using buffered lidocaine as a local anesthetic
before cardiac catheterization
Cathet Cardiovasc Diagn 1991; 23 100-2

Previous reports have suggested that pain associated with the injection
of lidocaine is related to the acidic pH of the solution. To determine
if the addition of a buffering solution to adjust the pH of lidocaine
into the physiologic range would reduce pain during injection, we
performed a blinded randomized study in patients undergoing cardiac
catheterization. Twenty patients were asked to quantify the severity of
pain after receiving standard lidocaine in one femoral area and buffered
lidocaine in the opposite femoral area. The mean pain score for buffered
lidocaine was significantly lower than the mean score for standard
lidocaine (2.7 +/- 1.9 vs. 3.8 +/- 2.2, P = 0.03). The pH adjustment of
standard lidocaine can be accomplished easily in the catheterization
laboratory before injection and results in a reduction of the pain
occurring during the infiltration of tissues.

McGlone R, Bodenham A
Reducing the pain of intradermal lignocaine injection by pH buffering
Arch Emerg Med 1990; 7 65-8

The effect of pH on the pain of administration and efficacy of 1%
lignocaine was investigated in a prospective, double-blind, randomized
study of 20 adult volunteers. Onset and spread of anaesthesia by intra-
dermal injection were not altered, but there was a significant reduction
in pain scores with a higher pH. Overall, pain scores appear to be more
dependent on the speed of injection rather than alteration of pH.

Pontasch MJ, Brodell RT
pH buffering of local anesthetic solutions: marked reduction in pain with
local infiltration of anesthetic solutions [letter]
J Dermatol Surg Oncol 1988; 14 672