Postarthroscopy analgesia with bupivacaine A

prospective, randomized,

blinded evaluation

RICHARD C. HENDERSON,* MD, PhD, EDMUND R. CAMPION, MD, RALPH A. DeMASI, AND TIMOTHY N. TAFT, MD From the Division of Orthopaedics,

University of North Carolina, Chapel Hill,

North Carolina

into the knee joint,’, 12,22 and bupivacaine does not appear to be harmful to articular cartilage.16 Although safe, the efficacy of this practice is not proven. The purpose of this study is to examine in a prospective, randomized, and blinded fashion the effectiveness of intraarticular bupivacaine as an adjunctive measure to diminish discomfort fol-

ABSTRACT The analgesic effect of intraarticular bupivacaine injected at the conclusion of knee arthroscopy done under general anesthesia was investigated in a prospective, randomized, and blinded fashion. Pain scores, the use of analgesic medications, crutch use, weightbearing, activity level, and difficulty sleeping the night after surgery were all unaffected by the use of bupivacaine. The apparent lack of effect is most likely due to rapid clearance from the knee, leaving only a transient, 1 to 2 hours of potential benefit. In this study, the patients were already quite comfortable during this time period due to the routine use of intraoperative narcotics. The preoperative level of knee discomfort was found to be a major determinant of postoperative discomfort. Other much less important factors were synovial and chondral shaving, sex of the patient, and experience of

lowing knee arthroscopy. In addition, detailed data collection and analysis will enable us to determine to what degree other factors may or may not influence the level of postoperative discomfort. MATERIALS AND METHODS One hundred patients

undergoing elective outpatient knee arthroscopy comprised the study group. During the period of study 275 outpatient knee arthroscopies were performed. Excluded were patients who did not consent to randomization, had bilateral knee arthroscopy, had some other procedure in addition to knee arthroscopy, reported a prior adverse reaction to bupivacaine or similar local anesthetics, had local or epidural anesthesia, failed to return a correctly completed questionnaire, or were regularly taking nonsteroidal antiinflammatory drugs (NSAIDs) preoperatively. Patients regularly taking NSAIDs were excluded because of the well-documented ability of these drugs to diminish discomfort after arthroscopy.3,17 Also excluded were patients who had an arthroscopic lateral release, since the postoperative pain following this procedure was likely to be significantly greater than other arthroscopic procedures. The pa-

the surgeon.

Bupivacaine is a local anesthetic of the amide group with a relatively long duration of action compared to other drugs in its class. It has been used successfully for local,anesthesia during knee arthroscopy.’, lo-lz, ~5, zz Its long-lasting effect has been used to an advantage in stellate ganglion blocks’ and to control vasospasms following microvascular surgery, 18 with a duration of action exceeding 8 hours in both situations. Also, bupivacaine following various surgical procedures has been reported to help diminish postoperative pain.4, 14, ls An informal survey of orthopaedists in our region revealed that many injected bupivacaine intraarticularly at the conclusion of knee arthroscopy to help diminish postoperative discomfort. Serum levels of bupivacaine remain well below toxic levels following injection of 100 mg or less

tients 0.25%

were

randomized to receive

or not receive 30 ml of at the conclusion of their

bupivacaine intraarticularly procedure. A 30 ml injection of saline was not used as a control since the primary purpose of the study was to compare one common clinical practice (injecting bupivacaine) to another common practice (not injecting bupivacaine). The patients were not told whether or not they received bupivacaine until after they had returned the questionnaire. Informed consent, approved by our Committee on the Pro-

*

Address correspondence and reprint requests to: Richard C. Henderson, MD, Division of Orthopaedics, University of North Carolina, 237 BurnettWomack Building 229H, Campus Box #7055, Chapel Hill, NC 27599.

614

615

TABLE 1

tection of the Rights of Human Subjects, was obtained from all patients. Just prior to surgery the patients completed a questionnaire regarding any recent knee injury, their preoperative level of knee discomfort, and recent medications. The surgeon, using the radiographs, clinical examination, and arthroscopic findings, assessed the knee for degenerative

changes, chondromalacia, synovitis, effusion, hemarthrosis, and localized full thickness articular defects. Each of these were

graded

none,

mild,

or severe.

Ligamentous laxity

Demographic data

Chi square analysis: Statistically significant difference in distribution of patients by sex. All other P values >0.15. a

was

assessed and, if present, the specific type of instability was recorded. The arthroscopic procedure(s) performed, portals used, duration of procedure, duration (if any) of tourniquet use, and level of training of each of the primary and assisting surgeons (attending, senior resident, junior resident) were recorded. General anesthesia was used in all cases. The use of intravenous intraoperative narcotics is standard procedure in our hospital and was given in all of the cases. The choice of specific narcotic agent and the dose(s) given were left to the discretion of the anesthesiologist. Portals were closed with tapes or a single stitch. At the time of injection, a small amount of bupivacaine was sometimes observed to leak from the closed portals. Knee immobilizers were not used. Crutches were provided with instructions to use them as needed with ad lib weightbearing. All patients were given a prescription for acetominophen with codeine or an alternative narcotic analgesic if they reported a prior adverse reaction to codeine. Discomfort in the first 18 to 24 hours after surgery was assessed with a questionnaire that was sent home with the patients. A physician not involved in the procedure telephoned the patient the day after surgery to help assure timely completion of the questionnaire, which was then returned by mail. The questionnaire included linear visual analog pain (VAP) scales’~ 20, 21 for various time points (e.g., on arrival home, at bedtime, first arising in the morning) during the first 24 hours following surgery. The earliest time point was the arrival time back home since our preliminary studies had indicated that nearly all patients were quite comfortable until at least that time. This time point varied slightly between patients, but was easily recalled by the patient and was consistently 2 to 5 hours after surgery. VAP scores range from 0 (no discomfort) to 10 (agonizing pain) based on placement by the patient of a mark along a 10 cm line. Narcotic and nonnarcotic analgesics were available on an as-needed basis in the recovery room and postoperative observation area. Any use of these medications was noted. The patients recorded their use at home of prescription and nonprescription analgesics, including the time taken and dose. Questions regarding weightbearing, crutch use, general activity level, and difficulty sleeping the night after surgery were also included.

RESULTS The study group was generally young (average age, 29 years) and predominantly male (66%; Table 1). During the 48 hours

TABLE 2 Technical aspects

°

Chi square

analysis; all other P values >0.15.

b Average times based only on cases in which it was used. patients noted moderate to pain in the knee, and 25% had taken nonprescription analgesics for the discomfort. As expected in a population undergoing arthroscopy, degenerative changes (37%), synovitis (65%), chondromalacia (34%), and an effusion (33%) were common findings. There were no significant differences between the bupivacaine and no bupivacaine groups in any of these findings. Details of the operative procedure(s) are given in Table 2. The most common procedure was partial or complete meniscectomy, with 27% of the patients having medial meniscectomy and 28% lateral meniscectomy (eight patients had both). Simple diagnostic arthroscopy was the next most common procedure (24%). The operative time averaged 48 minutes, with only four cases lasting longer than 70 minutes. A tourniquet was used in 47% of the cases, for an average of 40 minutes. An attending physician was the primary surgeon in most cases (58%), but residents with varying levels of expertise did perform some of the procedures. Due to the synovitis and chondromalacia that were frequently encountered, at least some synovial and/or chondral shaving was often necessary. This was specifically noted because of the potential effect that shaving may have on postoperative prior

to surgery, 18% of the

severe

discomfort. The many factors other than bupivacaine that could potentially affect postoperative discomfort were evaluated using a step-wise linear regression analysis [Statistical

616

Analysis System (SAS) Software, Cary, NC]. The most significant determinant of postoperative VAP scores was the preoperative level of discomfort (r2 0.183, P < 0.0005). =

Other factors that tended to have

a

small, but

not statisti-

cally significant (0.1 < P < 0.15) effect were: synovial and chondral shaving (r2 0.025); sex of the patient (r2= 0.021), with women tending to report more discomfort; and experience of the surgeon (r2 = 0.020). The VAP scores and use of narcotic-containing analgesics (usually acetaminophen with codeine) in the time periods 0 to 6 hours, 6 to 12 hours, and 12 to 24 hours after surgery are shown in Table 3. Nonprescription analgesics were rarely taken. Only 8% of the bupivacaine group and 4% of the no bupivacaine group reported using nonprescription analgesics during the first 6 hours after surgery, and none were reported for the period 6 to 12 hours after surgery. The bupivacaine group had higher VAP scores and used more analgesics than the no bupivacaine group, but a multivariate analysis that =

includes the effects of other factors showed that the differences were

not

statistically significant (P > 0.8).~ Similarly,

there were no significant differences between the two groups with regard to postoperative crutch use, general activity

level,

or

weightbearing.

DISCUSSION

Many factors other than bupivacaine could potentially directly affect or at least correlate with the level of discomfort experienced after knee arthroscopy: the preoperative level of discomfort, the condition of the knee (e.g., degenerative changes, synovitis, effusion, etc.), the specific type of pro-

If

equalization of potentially significant variables is accomplished by randomization, this will help to assure that any difference postoperatively between the two groups is truly due to the effect of bupivacaine and, thus, minimizes the possibility of false-positive findings. However, the presence of multiple relevant factors experimentally controlled only by random equalization increases the possibility of false-negative findings. If the effect of bupivacaine is small relative to the variation in discomfort from patient to patient

produced by other factors, then the bupivacaine effect might not be apparent with simple comparisons of the two groups. To compensate for this, each potential factor was first evaluated for its relationship to knee discomfort after arthroscopy using a forward step-wise linear regression analysis. The VAP scores and medication usage during the first 6 hours, 6 to 12 hours, and 12 to 24 hours after surgery were then compared in the bupivacaine and no bupivacaine groups using a multivariate analysis.’ As shown in Table 3, intraarticular bupivacaine did not diminish postoperative VAP scores or reduce the use of analgesics as compared to the group that did not receive bupivacaine. This was true even during the first 6 hours after surgery when bupivacaine was most likely to be of benefit. Similarly, the use of crutches, weightbearing, activity level, and difficulty sleeping were not affected by the injection of bupivacaine. There are several reasons bupivacaine may not have been

ber of variables are considered. In this series the distribution by sex and the use of a tourniquet were significantly different between the two groups (P 0.05). There was also a strong tendency (0.05 < P < 0.1) for fewer meniscectomies and more simple diagnostic arthroscopies in the bupivacaine group compared to the no bupivacaine group. However, these inequities can be readily adjusted with appropriate statistical

effective. A dose of 100 mg intraarticularly (40 ml of 0.25%) has been shown to result in safe blood levels so, potentially, a larger dose could have been used .5, &dquo; However, toxic reactions to bupivacaine have occurred at blood levels generally felt to be safe6 and several authors have recommended less than 100 mg for arthroscopy.’, 1’, &dquo; Further, in other sites such as the epidural space, less than 75 mg routinely produces a significant effect lasting several hours.13 Therefore, the dose of 75 mg used in this study should have been adequate to produce a positive effect if bupivacaine was going to be significantly beneficial at a safe dose. Some surgeons feel that the portals are a primary source of postoperative pain. Therefore, one common practice is to inject some or all of the bupivacaine around the closed portals rather than into the knee joint. Since routinely only the skin and not the capsule is closed, it is expected that the portals are &dquo;injected&dquo; in a retrograde fashion with intraarticular injection of bupivacaine. This was, in fact, confirmed when in several of our cases a small amount of bupivacaine was seen to leak from the closed portals at the time of the

analysis.

injection.

cedure (e.g., simple diagnostic arthroscopy versus meniscectomy), and various technical aspects of the procedure (e.g., experience of the surgeon, procedure duration, use of a tourniquet, etc.). To accurately assess the effect, if any, of bupivacaine these factors must be considered. By randomization of a large number of patients, these potential factors tend to be equalized in the bupivacaine and no bupivacaine groups. However, randomization does not necessarily guarantee equalization of all factors, particularly if a large num-

=

TABLE 3

Postoperative discomfort

° Mean number of pills taken per

patient during the specified time period. Includes patients who

took

no

medication.

617

The most likely explanation for the lack of apparent effect is rapid uptake of bupivacaine from the knee joint. Serum levels of bupivacaine peak within 30 to 60 minutes of injection into the knee joint, indicating very rapid synovial uptake.5,12, 22 Whether the inclusion of epinephrine would significantly delay this is unproven. The long-acting effect, lasting 3 to 4 hours and longer with bupivacaine in other clinical situations, involves sites without such rapid clearance.4, s,13, ~4, 18, 19 A study on the use of prilocaine (a local anesthetic chemically similar to bupivacaine) for knee arthroscopy has shown that blood levels peak at 1 hour with intraarticular injection of the drug and at 8 hours with subcutaneous injection.’ As a result of rapid clearance, the analgesic effect of intraarticular bupivacaine is probably quite transient, with any significant effect lasting less than 1 to 2 hours. The routine use at our institution of intraoperative narcotics during anesthesia may have masked any transient benefit from bupivacaine. Analgesics were available on an as-needed basis in the recovery area, but only 2 of the 100 patients, both in the no bupivacaine group (4%), requested any medication during the 1 to 3 hours prior to discharge home. This indicates that our patients were already quite comfortable during the time period when bupivacaine may have some small effect. In support of this explanation, a recent study of postarthroscopy analgesia in which intraoperative narcotics were not used found that 62% of the patients required analgesics during the first 2 hours after surgery.1 Of considerable interest was the relative influence of different factors on the postoperative level of discomfort. The preoperative level of discomfort was the major determinant of postoperative discomfort. Other factors with a slight, but not statistically significant, effect were: synovial and chondral shaving, sex of the patient (females tending to report more discomfort), and experience of the surgeon. It is not surprising that there is less discomfort following shorter procedures not requiring synovial or chondral shaving and performed by more experienced surgeons. The combined effect of these factors, however, is still not as significant as the preoperative level of discomfort. All surgeons presumably are already attempting to maximize their technical expertise. In contrast, efforts specifically directed at diminishing the preoperative level of discomfort (such as NSAIDs) are less universal, and if successful, potentially more significant in decreasing postoperative discomfort. Factors not found to be significant included use of a tourniquet and, if used, the duration of tourniquet use. Tourniquets certainly can cause discomfort while inflated. However, with the short periods of use in this study (average 40 minutes), tourniquet pain very quickly resolves when the tourniquet is deflated. Also, the specific procedure performed

to have no direct effect on postoperative discomfort. The average VAP scores for all three time periods were no higher in the group that had a meniscectomy procedure than the group that had only diagnostic arthroscopy. In conclusion, 30 ml of 0.25% bupivacaine injected intraarticularly following knee arthroscopy performed under general anesthesia (including intravenous intraoperative narcotics) does not significantly influence postoperative discomfort.

appeared

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Postarthroscopy analgesia with bupivacaine. A prospective, randomized, blinded evaluation.

The analgesic effect of intraarticular bupivacaine injected at the conclusion of knee arthroscopy done under general anesthesia was investigated in a ...
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