Copyright © 2009 by The Journal of Bone and Joint Surgery, Inc.
Commentary & Perspective
Commentary & Perspective by
Joseph Marino, MD*,
Huntington Hospital, Greenlawn, New York
Posted July 2009
In this issue of The Journal, Coghlan et al. report a prospective randomized placebo-controlled
trial in which they evaluated the postoperative analgesic efficacy of a
continuous subacromial infusion of ropivacaine in two different surgical
populations: arthroscopic subacromial decompression, and rotator cuff repair.
Both groups received a preemptive intra-articular bolus of ropivacaine into the
glenohumeral joint along with intravenous parecoxib and patient-controlled analgesia
with morphine. The study successfully demonstrated a significant (p = 0.003) but
clinically unimportant analgesic difference with the addition of continuous
subacromial ropivacaine for arthroscopic shoulder surgery. This is a
well-designed study that provides important information in light of the
continuing debate among advocates of postoperative subacromial local anesthetic
infusions.
The question being addressed is in fact very interesting.
The context is quite different from the standard practice seen in the United
States, where the two surgical procedures under study are usually performed in
an ambulatory setting. It may be difficult to extrapolate the results from the
inpatient to the outpatient setting because patients remained in the hospital
overnight, used a potent intravenous form of the Cox-2 inhibitors (parecoxib) that
is not available in the U.S., and had access to intravenous morphine, which
would not be the case in an ambulatory setting.
The major methodological strength of this trial is that it
is a prospective, randomized, double-blinded placebo-controlled study.
Furthermore, the authors skillfully considered atypical factors (e.g., dominant
arm used, patient receiving Workers' compensation benefits) that may have affected
postoperative pain (see Table I of the Coghlan paper). Although the authors
successfully demonstrated that a multimodal approach involving the use of
different classes of analgesics and different sites of analgesic administration
provides superior dynamic pain relief, the subacromial infusions that were
administered to patients in this study were preceded by the intra-articular
placement of a high concentration (1%) of ropivacaine. In conjunction with use
of intravenous morphine, such a substantial initial preemptive block
concentration may have provided most of the postoperative analgesia. That being
said, there is evidence questioning the intra-articular placement of local
anesthetic because of the potentially cytotoxic effects on chondrocytes1,2.
Other methodological weaknesses included use of two
different surgical populations with potentially diverse postoperative pain
requirements, hospitalization for twenty-four hours,
the use of parecoxib, and free access to intravenous morphine. Analysis of the
data shows a relatively high morphine use in the first twelve hours in all four
groups (range: 18 to 22 mg); furthermore, the use of parecoxib served as an
opioid-sparing analgesic adjuvant. The exclusion of parecoxib from the trial might
have led to even larger doses of opioid consumed. The extremely low pain scores
seen in all groups may have resulted from the substantial morphine doses used
in the first twelve hours alone.
The data from Coghlan et al. additionally corroborate the
unpredictable rates of infusion with ambulatory infusion pumps that have been
seen in previous studies3. Although the authors demonstrated no
deleterious consequences for those in whom a greater than anticipated volume of
ropivacaine was given, the erratic delivery rate of this ambulatory infusion
pump further calls into question the utility of these instruments. The maximum
recommended upper dose limit of ropivacaine is 300 mg4. The initial
intra-articular dose, coupled with the unpredictable delivery rate, may
predispose patients to approach the threshold of local anesthetic toxicity. It
would have been helpful if, in their Discussion, the authors had provided
evidence regarding whether the 1% bolus and 0.75%
infusion concentrations were any more effective in this setting than, say, 0.5%
and 0.2%, respectively.
In conclusion, this prospective, randomized study adds to
our knowledge regarding the issue of subacromial infusions. The Level-I data
imparted by this study offer important objective evidence that a continuous
subacromial infusion of ropivacaine after arthroscopic shoulder surgery
provides no added analgesic benefit when a multimodal approach utilizing a
preemptive intra-articular bolus of ropivacaine, cox-2 inhibitors, and
intravenous opioids is used. The diligence of Coghlan and her colleagues is
commendable, and their conclusions have the potential to modify current medical
practice.
*The author did not receive any outside funding or grants in support of his research for or preparation of this work. Neither he nor a member of his immediate family received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity.
References
1. Chu CR, Izzo NJ, Papas NE, Fu FH. In vitro exposure to 0.5% bupivacaine is cytotoxic to bovine articular chondrocytes. Arthroscopy. 2006;22:693-9.
2. Hansen BP, Beck CL, Beck EP, Townsley RW. Postarthroscopic glenohumeral chondrolysis. Am J Sports Med. 2007;35:1628-34.
3. Ganapathy S, Amendola A, Lichfield R, Fowler PJ, Ling E. Elastomeric pumps for ambulatory patient controlled regional analgesia. Can J Anaesth. 2000;47:897-902.
4. Naropin (ropivacaine HCl) injection package insert. Astra Zeneca LP, Wilmington, Delaware.
|
