THE EFFECT OF DEXAMETHASONE ON THE DURATION OF

INTERSCALENE NERVE BLOCKS WITH ROPIVACAINE OR BUPIVACAINE

by

KENNETH C. CUMMINGS III, M.D.

Submitted in partial fulfillment of the requirements

For the degree of Master of Science

Clinical Research Scholars Program

CASE WESTERN RESERVE UNIVERSITY

May, 2011

CASE WESTERN RESERVE UNIVERSITY

SCHOOL OF GRADUATE STUDIES

We hereby approve the thesis/dissertation of

Kenneth C. Cummings III, M.D.

candidate for the Master of Science

degree *.

Randall Cebul, M.D. (signed)

(chair of the committee)

Daniel Sessler, M.D.

Denise Babineau, Ph.D. March 3 ,2011

(date)

*We also certify that written approval has been obtained for any proprietary material contained therein.

  2

 

TABLE OF CONTENTS 

List of Tables ........................................................................................................................................ 3 List of Figures ....................................................................................................................................... 4 Acknowledgments ................................................................................................................................ 5 Abstract .................................................................................................................................................. 6 Hypotheses ............................................................................................................................................ 8 Objectives .............................................................................................................................................. 8 Background and Significance .............................................................................................................. 9

Introduction: Interscalene Brachial Plexus Blocks ...................................................................... 9 Prolonging Analgesia from Interscalene Blocks: Catheter Techniques ................................. 10 Prolonging Analgesia from Interscalene Blocks: Adjuvant Drugs ......................................... 11 Prolonging Analgesia from Interscalene Blocks: Glucocorticoids ......................................... 12 Differences between Local Anesthetics ...................................................................................... 13

Materials and Methods ...................................................................................................................... 16 Design and Setting ......................................................................................................................... 16 Participants ...................................................................................................................................... 16 Intervention .................................................................................................................................... 17 Data Analysis: Primary Outcome ................................................................................................ 20 Data Analysis: Secondary Outcomes .......................................................................................... 21 Data Analysis: Subgroups ............................................................................................................. 21 Sample Size Considerations .......................................................................................................... 21

Results .................................................................................................................................................. 24 Primary Outcome ........................................................................................................................... 27 Secondary Outcomes ..................................................................................................................... 28 Subgroup Analyses ......................................................................................................................... 30

Open versus Arthroscopic Procedures ................................................................................... 30 Study Site ..................................................................................................................................... 31 Ethnicity ...................................................................................................................................... 32

Safety ................................................................................................................................................ 32 Discussion ........................................................................................................................................... 34 Appendix ............................................................................................................................................. 40

Appendix 1A—Open Procedures: Pain Scores at Rest and with Movement ....................... 40 Appendix 1B—Arthroscopic Procedures: Pain Scores at Rest and with Movement .......... 40 Appendix 2A—Euclid Hospital: Pain Scores at Rest and with Movement .......................... 41 Appendix 2B—Hillcrest Hospital: Pain Scores at Rest and with Movement ....................... 41 Appendix 2C—Strongsville ASC: Pain Scores at Rest and with Movement ........................ 42

Bibliography ........................................................................................................................................ 43

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LIST OF TABLES 

Table 1—Opioid Equivalent Doses ............................................................................................................... 19

Table 2—Summary of patient characteristics by treatment group ............................................................ 26

Table 3—Total Three-Day Opioid Consumption in Oral Oxycodone Equivalents .............................. 30

Table 4—Median Time to First Analgesic Request and Opioid Use by Procedure ............................... 30

Table 5—Median Time to First Analgesic Request and Opioid Use by Study Site ................................ 31

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LIST OF FIGURES 

Figure 1—Chemical Structures of Ropivacaine and Bupivacaine .............................................................. 14

Figure 2—Stopping Boundaries for Interaction ........................................................................................... 24

Figure 3—CONSORT Study Flow Diagram ................................................................................................ 25

Figure 4—Time to First Opioid Analgesic Use ............................................................................................ 27

Figure 5—Time to Noticeable Increase in Pain ........................................................................................... 28

Figure 6—VRS Pain Scores at Rest and with Movement ........................................................................... 29

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ACKNOWLEDGMENTS

The author thanks Edward Mascha, Ph.D. for assistance with the sample size

calculations and design of the data analysis plan and Jarrod Dalton, M.A. and Linda

Cummings, M.D, M.S. for assistance with the data analysis and statistical programming. The

author also thanks the Committee members for their advice and assistance.

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The Effect of Dexamethasone on the Duration of Interscalene Nerve Blocks with

Ropivacaine or Bupivacaine

Abstract

by

KENNETH C. CUMMINGS III, M.D.

Background: Single-injection interscalene blocks for shoulder surgery are effective but

time-limited. Adjuncts such as dexamethasone may help. This study tested the hypothesis

that adding dexamethasone significantly prolongs the duration of ropivacaine and

bupivacaine analgesia, and that the effect differs between the two local anesthetics.

Methods: At 3 centers in the Cleveland Clinic, 218 patients undergoing shoulder procedures

with interscalene blocks were randomized to 4 groups: 30 ml ropivacaine or bupivacaine

0.5% with or without dexamethasone 8mg. The primary outcome was time to first analgesic

request. Kaplan-Meier curves and Cox proportional hazard models were used to compare

groups.

Results: Dexamethasone significantly prolonged analgesia from both ropivacaine (Kaplan-

Meier curve estimated median [interquartile range] 11.8 [9.7, 13.8] versus 22.2 [18.0, 28.6]

hours) and bupivacaine (14.8 [11.8, 18.1] and 22.4 [20.5, 29.3] hours). This effect was

stronger in ropivacaine than bupivacaine.

  7

 

Conclusions: Dexamethasone prolongs analgesia from blocks using ropivacaine or

bupivacaine, with the effect stronger with ropivacaine.

  8

 

HYPOTHESES

1. Dexamethasone prolongs the analgesic effect of interscalene brachial plexus blocks.

2. This prolongation differs depending on whether dexamethasone is added to bupivacaine

or ropivacaine.

OBJECTIVES 

Primary Objectives

1. To determine the duration of analgesia (time to first analgesic request) after interscalene

blocks when dexamethasone is added to bupivacaine or ropivacaine for patients

undergoing moderately- to severely-painful shoulder procedures.

2. To evaluate any difference in effect of dexamethasone when added to bupivacaine versus

ropivacaine.

Secondary Objectives

1. To evaluate the effect of adding dexamethasone to local anesthetics on postoperative

opioid requirements.

2. To evaluate any difference in postoperative pain scores after interscalene block due to

adding dexamethasone.

3. To determine any increase in intermediate-term (2-week) complications of interscalene

blocks due to adding dexamethasone.

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BACKGROUND AND SIGNIFICANCE 

 

Introduction: Interscalene Brachial Plexus Blocks

Pain after orthopedic surgery can be intense.1 In particular, managing pain after

shoulder procedures poses a challenge to both anesthesiologists and orthopedic surgeons. In

an effort to improve analgesia and facilitate mobilization, regional anesthesia in the form of

an interscalene approach to the brachial plexus is often used either as an adjunct to general

anesthesia or as the primary anesthetic. The brachial plexus of nerves arises from the ventral

rami of C5 to T1 (with variable contributions from C4 and T2) and travels between the

anterior and middle scalene muscles, ultimately providing sensory and motor innervation to

the shoulder, arm, and hand. The upper elements of the plexus (innervating the shoulder and

part of the arm) are more superficial and are readily accessible for deposition of local

anesthetic in the interscalene area.2

Although associated with complications such as plexus injury, unintended spinal or

epidural anesthesia, or intravascular injection, the actual rate of severe acute or long-term

complications is only 0.4%.3 Use of an interscalene block as the primary anesthetic increases

the proportion of patients suitable for PACU bypass and decreases immediate postoperative

pain.4 However, the improved analgesia is short-lived: the block has not been shown to

improve pain scores beyond 24 hours postoperatively.

  10

 

Prolonging Analgesia from Interscalene Blocks: Catheter Techniques

Multiple studies have evaluated perineural catheters as a means to provide

continuous brachial plexus analgesia for both inpatient5-6 and outpatient4 situations. Such

catheters are placed in the perioperative period and then left in place for several days to

provide a continuous supply of local anesthetic to the nerves. These techniques, however,

pose logistical difficulties such as secondary block failure (pain after the initial bolus of

medication diffuses), disconnection, and equipment troubleshooting.7-8 Furthermore,

outpatient use of indwelling peripheral nerve catheters is potentially associated with

infectious complications and unrecognized local anesthetic toxicity, although neither concern

has yet been substantiated.

In addition to these safety and convenience issues, there are significant cost

differences between single-injection blocks and continuous catheter techniques. For

example, the average acquisition cost for 30 ml of 0.5% ropivacaine (Naropin©, APP

Pharmaceuticals, Schaumburg, IL) used for a single-injection block is approximately $10

(personal communication, Department of Pharmacy, Hillcrest Hospital, Mayfield Heights,

OH). For the most commonly-used ambulatory infusion pump (On-Q with Select-A-Flow and

ONDEMAND©, I-Flow Corporation, Lake Forest, CA) filled with 0.2% ropivacaine, the

acquisition cost is roughly $500. Patient charges and reimbursement will vary, so catheters

may make financial sense for a particular institution, but the societal economic benefit of a

simpler, less expensive regimen is clear.

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Prolonging Analgesia from Interscalene Blocks: Adjuvant Drugs

Patients undergoing shoulder procedures with single-injection interscalene blocks are

frequently hospitalized overnight due to inadequate pain relief after resolution of their

blocks. For 0.5% ropivacaine or bupivacaine, the usual local anesthetics, previous studies

report an average analgesic duration of 11 hours without epinephrine9 and approximately 12

hours with epinephrine.10 Consequently, a method of prolonging analgesia from a brachial

plexus block without the extra cost and logistical difficulties of indwelling catheters would

benefit both patients and their caregivers. One promising approach is use of adjuvant drugs

that prolong block duration when added to the local anesthetic.

Many drugs have been studied as adjuvants for single-injection regional anesthetic

techniques. Epinephrine is commonly used as a marker of intravascular injection, but has

minimal effect on the duration of analgesia of long-acting local anesthetics.10 In addition to

epinephrine, drugs including clonidine, opioids, and ketamine have been evaluated for their

effects on anesthesia and analgesia. Results have conflicted depending on the drug used and

the choice of local anesthetic.

Clonidine, an α2 adrenergic agonist, has shown inconsistent results in trials using

axillary brachial plexus blocks. In two trials, it prolonged anesthesia from lidocaine11 as well

as mepivacaine and bupivacaine, but not ropivacaine.12 A separate study, however,

contradicts these results, showing no benefit with bupivacaine or levobupivacaine.13 Any

potential benefit from clonidine must also be weighed against its sedative and hypotensive

effects when absorbed.

Due to their systemic analgesic effects, opioids have also been evaluated for

effectiveness when mixed with local anesthetics. Fentanyl, a synthetic opioid, has been

  12

 

shown to prolong analgesia from axillary brachial plexus blocks with lidocaine and

bupivacaine.14-15 In contrast, other investigators found no benefit with ropivacaine.16

Buprenorphine, an opioid agonist-antagonist, has been demonstrated to modestly prolong

analgesia after axillary blocks with a mixture of local anesthetics17-18 as well as sciatic nerve

blocks using bupivacaine with epinephrine.19 Opioids also have the potential for systemic

effects (sedation, respiratory depression, nausea) after absorption of the local anesthetic

mixture.

Ketamine is a phencyclidine derivative used as a sedative and analgesic. It has been

shown to inhibit axonal conduction when injected intrathecally,20-21 thus providing rationale

for its study in peripheral nerve blocks. Limited data support its use in axillary brachial

plexus blocks22 but not local wound infiltration (“field block”).23 Ketamine also has systemic

effects when absorbed (sedation, dysphoria) and its toxicity to nervous tissue is a subject of

concern.24

Prolonging Analgesia from Interscalene Blocks: Glucocorticoids

Because of the limited efficacy or questionable toxicity of the previously-studied

drugs, some investigators have begun to evaluate glucocorticoids as adjuvants for regional

anesthesia. Known for their anti-inflammatory, analgesic, immunosuppressive, and

antiemetic properties, these corticosteroids exert their effects by inhibition of phospholipase

A2 as well as changes in cell function induced by glucocorticoid receptor activation.

Although these drugs are associated with significant toxicity when administered in large

doses for long periods, the literature suggests that a single perioperative dose of

glucocorticoid is safe.25-26

  13

 

Adding glucocorticoids to local anesthetics for regional anesthesia is an emerging

strategy that has only been evaluated in small trials. One study demonstrated a prolongation

of sensory block from 98 to 242 minutes when dexamethasone 8 mg was added to lidocaine

for axillary blocks.27 Methylprednisolone appears to have similar effects.28 Similar results

were found with supraclavicular blocks when dexamethasone 4-8 mg was added to a mixture

of lidocaine and bupivacaine.29 When added to a single injection of epidural bupivacaine, the

duration of analgesia was increased by a factor of 5.30 Parrington and colleagues31

demonstrated that adding dexamethasone 8 mg to mepivacaine increased the median

duration of supraclavicular blocks from 228 to 332 minutes. Finally, Vieira and colleagues 32

found that adding dexamethasone to a mixture of bupivacaine, epinephrine, and clonidine

increased block duration from 833 to 1457 minutes. The available data, although limited,

thus suggest that combining glucocorticoids with local anesthetics prolongs block duration.

Importantly, however, none of these studies evaluated ropivacaine (or plain bupivacaine)

block duration.

Why dexamethasone would prolong regional anesthesia is a subject of much

discussion and speculation. Steroids induce some degree of vasoconstriction, so one

hypothesis is that it acts in a similar manner to epinephrine by reducing local anesthetic

absorption. A more attractive hypothesis holds that dexamethasone may act locally on

nociceptive C-fibers (via glucocorticoid receptors) to increase the activity of inhibitory

potassium channels, thus decreasing their activity.33-34

Differences between Local Anesthetics

Given the differences seen with other adjuvants (particularly fentanyl and clonidine),

it might not be reasonable to assume that dexamethasone’s effect would be similar with

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different local anesthetics. Although ropivacaine is commonly used for interscalene blocks,

bupivacaine use is still widespread. Bupivacaine is a racemic mixture of stereoisomers,

whereas ropivacaine is supplied as the pure S(-) isomer. Chemically, however, they are similar

amide-class local anesthetics, differing only in the number of carbon atoms on the n-alkyl-

substituted piperidine ring: bupivacaine has a butyl (4-carbon) group whereas ropivacaine

has a propyl (3-carbon) group (Figure 1).35 This slight difference may in fact be clinically

important, as the decreased lipid solubility of ropivacaine is advanced as an explanation for

its enhanced tendency to block sensory nerve fibers more readily than motor fibers

compared to bupivacaine.

Figure 1—Chemical Structures of Ropivacaine and Bupivacaine 

 

 

The relative toxicities and potencies of ropivacaine and bupivacaine are the subject

of much debate. In summary, ropivacaine appears to be 10-25 percent less toxic to the

central nervous system (on a per-milligram basis) and roughly 30 percent less cardiotoxic.

Although ropivacaine may be less potent for spinal anesthesia, it appears to be equipotent to

bupivacaine for peripheral nerve blocks.36 Additionally, the dose-response curves for

bupivacaine and ropivacaine are not significantly different at clinically-relevant

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concentrations for peripheral nerve blocks.37 Therefore, in this paradigm, it is reasonable to

use identical concentrations of ropivacaine and bupivacaine.

Because no direct comparison has been undertaken (and ropivacaine has not been

studied), this study tested the hypothesis that dexamethasone prolongs the analgesic effect of

interscalene blocks using ropivacaine or bupivacaine for shoulder surgery and that this effect

differs between the two local anesthetics.

  16

 

MATERIALS AND METHODS 

Design and Setting

This prospective, randomized, double-blinded, placebo-controlled study was

approved by the Cleveland Clinic Institutional Review Board (protocol 08-647) and

conducted at Hillcrest and Euclid Hospitals and the Strongsville Ambulatory Surgery Center

in the Cleveland Clinic Health System. The trial was registered with ClinicalTrials.gov (#

NCT00801138). A total of 218 patients were enrolled between December, 2008 and

October, 2010 via the preadmission testing centers of the respective facilities.

Participants

Inclusion criteria were patients (age 18-75) undergoing moderately- to severely-

painful shoulder procedures (such as rotator cuff repair, capsular shift, shoulder arthroplasty,

and subacromial decompression) for which an interscalene block was planned.

Exclusion criteria included patient refusal, contraindication to interscalene block

(severe chronic obstructive pulmonary disease, infection, coagulopathy, contralateral

diaphragmatic paralysis), pregnancy, neuropathy of the surgical limb, recent (less than six

months) use of glucocorticoids for at least two weeks, and chronic pain requiring daily use of

opioid medication (greater than 30 mg/day of oral oxycodone equivalent).

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Intervention

Patients were randomized to single-injection interscalene blocks with four possible

drug combinations:

1) Ropivacaine: 30 ml 0.5% ropivacaine mixed with 2 ml 0.9% saline (placebo)

2) Bupivacaine: 30 ml 0.5% bupivacaine mixed with 2 ml 0.9% saline (placebo)

3) Ropivacaine and steroid: 30 ml 0.5% ropivacaine mixed with dexamethasone 8

mg (2 ml)

4) Bupivacaine and steroid: 30 ml 0.5% bupivacaine mixed with dexamethasone 8

mg (2 ml)

Computer-generated treatment assignments, with random permuted block size, were

stratified by clinical site and the invasiveness of the surgical procedure (open vs.

arthroscopic). Randomization assignments were stored in sealed, sequentially-numbered

opaque envelopes and opened immediately before the blocks were performed.

Demographic (age, gender, comorbidities) and morphometric (height, weight)

characteristics of participating patients were recorded. Patients, clinical personnel, and study

staff were blinded to group allocation. To maintain blinding, medications were prepared by

an experienced assistant uninvolved with the study or care of study patients. All blocks were

performed by attending anesthesiologists skilled in the interscalene approach. The choice of

block technique (nerve stimulator and/or ultrasound) was left to the discretion of the

attending anesthesiologist. Both block techniques used 50-mm-long insulated needles

(Stimuplex A, B Braun, Melsungen, Germany). The ultrasound technique consisted of an in-

plane posterior approach at the level of the cricoid cartilage. The nerve roots/trunks were

identified as hypoechoic structures between the anterior and middle scalene muscles. Local

  18

 

anesthetic was injected and needle position readjusted as necessary to ensure appropriate

spread. The nerve stimulation technique used was described by Winnie,38 with muscle

contraction of the deltoid or arm muscles at a stimulating current of <0.4 mA (2 Hz, 0.1 ms

duration) considered evidence of appropriate needle position.

After incremental injection of the designated local anesthetic mixture, patients were

evaluated at 5-minute intervals for 15 minutes for development of sensory and motor block.

Sensory block was assessed by loss of sensation to pinprick over the deltoid muscle. Motor

block was assessed by failure to abduct the shoulder, the so-called “deltoid sign.”39

Per the institutions’ clinical routine, patients were given general anesthesia along with

their interscalene blocks. The type of airway management, antiemetic prophylaxis, and

intraoperative opioid use were left to the discretion of the attending anesthesiologist with the

provision that no other corticosteroids be administered.

The severity of postoperative pain was assessed by a blinded study team member

using a verbal response score (VRS) upon admission to the post-anesthesia care unit

(PACU). Patients reporting pain scores greater than 2 were given intravenous morphine (2

mg) every 5 minutes until comfortable. After discharge from the PACU, supplemental

analgesia for inpatients consisted of acetaminophen 325-650 mg with oxycodone 5-10 mg

orally every 4 hours as needed for a pain VRS greater than 4, administered by the nurse

caring for the patient. Pain unrelieved by oral medication (VRS persistently greater than 4)

was treated with intravenous morphine. Outpatients received a prescription for oral

acetaminophen with oxycodone (or a similar medication according to surgeon preference)

and were instructed to delay administration of analgesics until they felt that their pain

warranted medication.

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A blinded observer interviewed patients each morning for three days postoperatively,

either in the hospital or by telephone. Subjects were given a medication diary to record the

required data. Data collected included time of block duration (the primary outcome; defined

as time from onset of sensory block to first administration of supplemental analgesic

medication after PACU discharge), as well as secondary outcomes: time to a significant

increase in shoulder discomfort, maximum VRS with rest and movement, and total three-day

opioid consumption. The time to initial analgesic use was determined from the medical

record for inpatients and by patient report for those already discharged. The times and VRS

scores for secondary outcomes were based on patient reporting of the corresponding events

at the daily interview. A member of the study staff contacted patients at 14 days

postoperatively to assess for any late or persistent complications such as residual sensory or

motor block. Total opioid doses were converted to oral oxycodone equivalents according to

conversion rates derived from the American Pain Society (Table 1).40

Table 1—Opioid Equivalent Doses 

Drug  Oral Dose (mg) Parenteral Dose (mg) 

Morphine  30 10

Hydromorphone  7.5 2

Oxycodone  20 ‐

Methadone  10 5

Hydrocodone  30 ‐

Meperidine  300 75

Codeine  200 ‐

Fentanyl  ‐  0.1

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Data Analysis: Primary Outcome

The primary outcome measure was duration of analgesia, defined as the interval

between the onset of sensory block and the initial post-PACU use of opioid analgesia for

surgical site pain. Patients who retained deltoid sensation were deemed to have failed blocks,

but were analyzed in their assigned groups according to intention-to-treat principles

(specifically, coded as having the outcome at a time of 0 hours). The duration of analgesia

(defined as time from onset of sensory block to first use of opioid analgesia) was analyzed by

Kaplan-Meier curves (compared via log-rank tests) and Cox proportional hazards regression

(stratified by clinical site). An interaction term between dexamethasone and the type of local

anesthetic was incorporated into the Cox model to investigate if the effect of dexamethasone

on duration of analgesia differed by type of local anesthetic and was assessed using a Wald

test in the stratified Cox model.

To maintain an overall 0.10 significance level for detecting an interaction, the

significance levels for 6 interim analyses were adjusted for the alpha spent during the interim

analysis (see sample size calculations). If the interaction between dexamethasone and type of

anesthetic was statistically significant at any of the interim analyses, a Bonferroni correction

was applied for the two multiple comparisons of the main effects (steroid effect within each

local anesthetic). At the third interim analysis at which the trial was stopped, these

adjustments led to a significance level for the main effects (dexamethasone within each local

anesthetic) of 0.002175 and for the interaction term 0.0087.

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Data Analysis: Secondary Outcomes

Secondary outcomes included time to a noticeable increase in shoulder discomfort,

maximum VRS pain scores with rest and movement on postoperative days 1, 2, and 3, and

total three-day opioid consumption (in oral oxycodone equivalents). Kaplan-Meier curves

and unpaired t-tests or Wilcoxon rank-sum tests were used as appropriate. Group

distributions of continuous variables were assessed visually using histograms.

Data Analysis: Subgroups

In a post-hoc analysis, the primary outcome of block duration and the secondary

outcomes of maximum VRS pain scores and opioid consumption were analyzed by the

invasiveness of the procedure (open versus arthroscopic), by clinical site, and by ethnicity.

Statistical testing was not valid due to the multiple subgroups and small sample sizes.

SAS statistical software version 9.2 (SAS Institute, Cary, NC, USA) and R software

version 2.11.1 (The R Foundation for Statistical Computing, Vienna, Austria) were used for

all statistical analyses.

Sample Size Considerations

Because almost all patients require opioid analgesics after shoulder procedures,

sample size estimation assumed no censoring of block durations. In summary, the study was

designed to have 90% power to detect clinically important interactions and main effects for

the primary outcome of block duration of 3 hours or more. With the planned interim

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analyses (see below), the expected sample size under the alternative hypothesis (interaction

between dexamethasone and type of anesthetic present) ranged between 73 and 436.

More specifically, Casati7 observed a mean (SD) block duration for ropivacaine 0.5%

of 11.1 (5) hours and bupivacaine 0.5% of 10.9 (3.9) hours both for 15 patients. To be

conservative, a SD of 5 hours was assumed. Based on the data from Casati, et al. and clinical

experience, we hypothesize mean block durations of 17 and 11 hours for ropivacaine

patients with and without dexamethasone, and 20 and 11 hours for bupivacaine patients with

and without dexamethasone, respectively. Under this scenario, the dexamethasone effect (vs.

placebo) would be 6 hours for those receiving ropivacaine and 9 hours for those receiving

bupivacaine, for a difference of 3 hours. In fact, regardless of the actual means, the study

was powered to be able to detect an interaction effect as small as 3 hours.

Adjusting for interim analyses (see below), a maximum of 436 patients at the 0.10

significance level of would be needed to detect an interaction of 3 hours or more between

the two factors with 90% power. A significance level of 0.10 was chosen due to the lower

power to detect interactions relative to main effects. Note that if the test for interaction is

non-significant, this sample size would also provide sufficient power to test the main effect

of dexamethasone. In the case of a significant interaction, 2 planned multiple comparisons

(e.g. dexamethasone vs. saline for each type of anesthetic) were performed assuming a

Bonferroni corrected significance level; this sample size (i.e. 73 - 436) also provided ample

power to detect a difference of 3 hours or more in block duration for each of the 2 planned

multiple comparisons.

Six interim analyses were planned to occur at sample sizes of 73, 145, 218, 290, 363

and a final analysis, if necessary, at N=436. Because of a fairly small increase in sample size

  23

 

relative to the number of interim analyses, six were chosen to facilitate early stopping of the

trial. For the test for interaction, stopping boundaries for efficacy (futility) at looks 1-6

respectively were P≤ 0.0018 (>0.9861), P≤ 0.0039 (>0.9556), P≤ 0.0087 (P>0.8534), P≤

0.0191 (P>0.5622), P≤ 0.0411 (P>0.2499) and P≤ 0.0869 (P>0.0869). For the 2 multiple

comparisons of dexamethasone vs. saline for each type of anesthetic, stopping boundaries

for efficacy (futility) at looks 1-6 respectively were P0.0004 (>0.9804), P0.0009 (>0.9120),

P0.0022 (>0.6408), P0.0045 (>0.2632), P0.0096 (P>0.0853), and P0.0202 (P>0.0202).

These boundaries were constructed using the gamma spending approach of Hwang,

et al,41 with gamma parameters of -4 for efficacy and -2 for futility. The gamma parameter

describes the rate at which error is spent, with higher numbers indicating faster spending.

The gamma parameter of -4 approximates the O’Brien-Fleming-type boundaries of the Lan-

DeMets method for type I error spending with slightly lower initial stringency. The

parameter of -2 was chosen for futility to more aggressively spend type II error which would

facilitate earlier stopping if no treatment effect were likely.

The above calculations were made using PROC POWER in SAS statistical software,

Cary NC, and East software, Cytel Corporation, Cambridge, MA.

  24

 

RESULTS 

Enrollment began in December 2008. At the third interim analysis (October 2010,

N=218), the efficacy boundary for interaction between dexamethasone and the type of

anesthetic was crossed (Figure 2; Wald test Z = 2.97, P ≤ 0.0087). In light of this, the trial’s

Executive Committee stopped the study.

Figure 2—Stopping Boundaries for Interaction 

Crosses indicate the test statistic for the interaction between steroid and local anesthetic at each interim analysis 

Figure 3 details the patient flow through the study. Baseline covariates were well-

balanced across the groups (Table 2). Seven patients did not have the primary outcome

(opioid use) and were right-censored at 72 hours in the analysis. They were evenly

distributed across the randomized groups.

  25

 

Figure 3—CONSORT Study Flow Diagram 

 

  26

 

 

Table 2—Summary of patient characteristics by treatment group Data are presented as percent or median [interquartile range]. 

Characteristic    Level    Ropivacaine  Bupivacaine  Ropivacaine+Dex  Bupivacaine+Dex 

        n=54  n=56  n=54  n=54 

Clinical Site    Euclid (%)    50  50  48  46 

    Hillcrest (%)    11  14  15  17 

    Strongsville (%)    39  36  37  37 

               

Age (yr)        55 [44,65]  60 [51,68]  59 [49,68]  58 [53,64] 

               

Body Mass Index 

(kg/m2) 

    29 [26,34]  29 [26,33]  29 [25,34]  28 [26,32] 

               

Gender    Female (%)    39  34  39  41 

    Male (%)    61  66  61  59 

               

ASA 

Classification 

      2 [2,3]  2 [2,3]  2 [2,2]  2 [2,3] 

               

Ethnicity    Caucasian (%)    89  98  96  91 

               

Procedure 

Type 

  Arthroscopic (%)    43  41  44  41 

               

Procedure    Rotator Cuff (%)    54  55  54  61 

    Arthroplasty (%)    17  21  20  22 

    Other (%)    30  23  26  17 

               

Failed Block 

(%) 

 

      4  4  5  4 

No opioid 

used (%) 

 

      2  5  5  0 

Ultrasound‐Guided (%)      69  69  72  69 

Nerve Stimulator Used 

(%) 

    34  30  33  39 

 

  27

 

Primary Outcome

Dexamethasone significantly prolonged the median duration of analgesia (estimated

from the Kaplan-Meier curves) of both ropivacaine (median [interquartile range] 11.8 [9.7,

13.8] versus 22.2 [18.0, 28.6] hours, log-rank test P < 0.001, interim analysis-adjusted

significance level of 0.002175) and bupivacaine (14.8 [11.8, 18.1] versus 22.4 [20.5, 29.3]

hours, log-rank test P < 0.001, Figure 4).

Figure 4—Time to First Opioid Analgesic Use Data presented as Kaplan‐Meier survival curves; shaded areas represent adjusted 95% pointwise confidence intervals. 

Based on the stratified Cox model for time to first opioid use, the block resolution

(hazard) rate among patients given ropivacaine with dexamethasone was 0.17 times (95% CI

0.08, 0.39) that among patients given ropivacaine alone. For bupivacaine, the block

resolution rate in patients given dexamethasone was 0.44 times (95% CI 0.23, 0.83) that of

patients receiving bupivacaine alone. The effect of dexamethasone in prolonging block

duration was significantly stronger in ropivacaine versus bupivacaine (interaction term Wald

test P=0.0029 at an interim-analysis adjusted significance level of 0.0087).

  28

 

An analysis of scaled Schoenfeld residuals (correlation of a predictor with time) and

visual inspection of complementary log-log survival plots did not identify any significant

violations of the proportional hazards assumption in the Cox models. Additionally,

removing influential observations (defined as a standardized DFBETA greater than 0.4) did

not affect the model hazard ratio estimates or change the result of the Wald test for

interaction.

Secondary Outcomes

Consistent with its effect on the primary outcome of first opioid use, dexamethasone

significantly prolonged the length of time until the patients’ first report of surgical site pain

(Figure 5). For ropivacaine, the median time [IQR] to surgical site pain (estimated from the

Kaplan-Meier curves) was 11.9 [9.2, 13.8] hours without dexamethasone and 22.3 [18.0, 27.2]

hours with dexamethasone (log-rank test P < 0.001). The corresponding times for

bupivacaine were 14.7 [13.4, 17.9] and 25.7 [21.7, 29.2] hours (log-rank test P < 0.001).

Figure 5—Time to Noticeable Increase in Pain Data presented as Kaplan‐Meier survival curves; shaded areas represent adjusted 95% pointwise confidence intervals. 

  29

 

Median maximum VRS pain scores at rest (shown in Figure 6) were significantly

lower in the bupivacaine plus dexamethasone group compared to saline on postoperative day

1 (3 versus 5, Wilcoxon rank-sum test P < 0.001 at a significance level of 0.025 adjusting for

the two comparisons within each day), but not in the ropivacaine groups. The only other

significant difference was on postoperative day 3 in the bupivacaine group: the

dexamethasone group had a significantly higher maximum VRS pain score than saline

(median 4 versus 2, P = 0.014).

The median maximum VRS pain scores with movement on postoperative day 1

(also shown in Figure 6) were significantly lower in both the ropivacaine plus dexamethasone

(5 versus 7, P=0.005) and bupivacaine plus dexamethasone groups (4 versus 5.5, P=0.01)

compared to saline. There were no significant differences on postoperative days 2 and 3.

Figure 6—VRS Pain Scores at Rest and with Movement Solid horizontal lines represent medians, boxes are interquartile range, whiskers extend to the range of the data. 

  30

 

Total three-day opioid consumption was obtained from all patients. Opioid

consumption was not significantly different between the randomized groups (Table 3).

Table 3—Total Three‐Day Opioid Consumption in Oral Oxycodone Equivalents (mg) 

Group  Median

[Interquartile Range] 

P‐Value*

Ropivacaine/Dexamethasone  79 [45.2, 100]0.29 

Ropivacaine/Saline  75 [45.2, 152.5]

Bupivacaine/Dexamethasone  60 [46.7, 105.2]0.15 

Bupivacaine/Saline  85 [51.3, 117.6]

*P‐values from Wilcoxon rank‐sum test.  Adjusted significance level=0.025.

Subgroup Analyses

Open versus Arthroscopic Procedures

Comparing open versus arthroscopic procedures, the difference in median time to

first analgesic request between those with and without dexamethasone is similar and

comparable to the overall results (Table 4). Opioid consumption tended to be lower in the

arthroscopic groups. Table 4 also details the opioid consumption of each subgroup.

Table 4—Median Time to First Analgesic Request and 3‐Day Opioid Consumption by Procedure 

Times estimated from Kaplan‐Meier Curves 

Procedure  Anesthetic  Dexamethasone 

(Yes/No) 

Time to First Analgesic

(median [IQR], hours) 

Oxycodone Consumption 

(median [IQR], mg) 

Open 

Ropivacaine Yes (n=30) 21.9 [18.3, 28.3] 80 [55, 97.5] 

No (n=31) 11.3 [10.7, 13.8] 145 [67.3, 175.8]

Bupivacaine Yes (n=32) 25.0 [21.3, 29.1] 81 [53.8, 116.3]

No (n=33) 14.8 [14.0, 18.4] 96 [71, 129.1]

Arthroscopic 

Ropivacaine Yes (n=24) 24.6 [19.3, 27.6] 52.6 [32.5, 98.8]

No (n=23) 11.9 [9.4, 13.8] 47.6 [31.3, 73.8]

Bupivacaine Yes (n=22) 25.2 [20.5, 30.2] 55 [35, 60] 

No (n=23) 14.7 [11.3, 16.8] 50 [40, 95] 

  31

 

Maximum VRS pain scores among open and arthroscopic procedures are consistent

with the overall results. Appendix 1A and 1B display maximum VRS pain scores at rest and

with movement comparing open versus arthroscopic procedures.

Study Site

The difference in median time to first opioid request between those with and

without dexamethasone was similar among all three clinical sites (Table 5). Total three-day

opioid consumption tended to be higher at Euclid hospital. Table 5 also details opioid

consumption by site.

Table 5—Median Time to First Analgesic Request and Three‐Day Opioid Consumption by Study Site 

Times estimated from Kaplan‐Meier curves 

Site  Anesthetic  Dexamethasone 

(Yes/No) 

Median time [IQR]

(hours) 

Oxycodone Consumption 

(Median [IQR], mg) 

Euclid 

Ropivacaine Yes (n=26) 21.9 [18.3, 29.2] 79.5 [45, 111.3]

No  (n=27) 12.3 [9.7, 13.6] 153 [70.5, 182]

Bupivacaine Yes (n=25) 22.9 [21.3, 28.1] 90 [70, 120] 

No  (n=28) 14.8 [14, 18.4] 120 [82.5, 136.2]

Hillcrest 

Ropivacaine Yes (n=8) 22.4 [21.8, 26.8] 72.5 [53.75, 88.5]

No  (n=6) 11.0 [9.8, 15.2] 52.5 [46.25, 88.75]

Bupivacaine Yes (n=9) 27.1 [17.6, 30.9] 50 [45, 75] 

No  (n=8) 14.7 [10.8, 15] 85.1 [63.8, 99.6]

Strongsville 

Ropivacaine Yes (n=20) 23.4 [15.4, 27.6] 72 [33.8, 98.8]

No  (n=21) 11.9 [9.9, 13.9] 55 [27.5, 76.3]

Bupivacaine Yes (n=20) 25.2 [22.3, 30.4] 55 [35, 60] 

No  (n=20) 14.9 [11.6, 18.0] 50 [35, 75] 

Maximum VRS pain scores analyzed by center were also consistent with the main

analysis, namely that pain scores tended to be lower in the dexamethasone groups on

postoperative day 1 and perhaps higher on postoperative day 3. Appendices 2A-2C show

maximum VRS pain scores at rest and with movement at the three study centers.

  32

 

Ethnicity

Removing the small number of non-Caucasian (primarily African-American) patients

(n=14) from the study sample did not appreciably change the primary outcome of time to

first analgesic use (Kaplan-Meier curve estimates median 11.9 [19.9, 13.6] hours versus 21.9

[18.3, 27.6] hours for ropivacaine and 14.8 [12.8, 18.1] hours versus 25.7 [21.8, 29.4] hours

for bupivacaine; log-rank test P < 0.001 for both Kaplan-Meier curve comparisons).

Total opioid consumption also did not significantly differ between groups when only

Caucasian patients were analyzed: 81.4 [50, 154] versus 79 [45, 100] mg for ropivacaine with

and without dexamethasone, respectively (Wilcoxon rank-sum test P=0.1) and 60 [49.2,

101.3] versus 87.5 [53.8, 120.4] mg for bupivacaine with and without dexamethasone,

respectively (Wilcoxon rank-sum test P=0.1).

Maximum VRS pain scores among Caucasians were also consistent with the entire

sample. At an adjusted significance level of 0.025 (for two comparisons within each day),

median VRS pain with movement on postoperative day 1 in the ropivacaine groups was 5

versus 7 for dexamethasone and saline, respectively (Wilcoxon rank-sum test P=0.002). For

bupivacaine, median postoperative day 1 scores at rest were 4 versus 5 (P<0.001) for

dexamethasone versus saline and 5 versus 5.5 with movement (P=0.003). There were no

other detectable differences at the 0.025 significance level.

Safety

All patients were contacted at 14 days postoperatively. At the 14-day interview, no

patient reported persistent numbness, paresthesias, or weakness of the operative limb. There

  33

 

were also no reports of persistent hoarseness, respiratory difficulty, injection site infection,

or hematoma.

  34

 

DISCUSSION 

This study demonstrates that dexamethasone significantly prolongs the analgesic

effect of plain ropivacaine and bupivacaine used as a single-injection interscalene block, and

that this effect differs between the two local anesthetics. This finding is generally consistent

with previous studies, but direct comparisons are difficult because of the variety of local

anesthetic mixtures used, different blocks studied, and different methods of evaluating block

duration.

The magnitude of block prolongation we observed is consistent with that observed

by Parrington and colleagues when dexamethasone was combined with mepivacaine for

supraclavicular blocks.31 Similarly, Vieira and colleagues32 observed that adding

dexamethasone to a mixture of bupivacaine, clonidine, and epinephrine increased

interscalene block duration from 13.9 to 24.3 hours. Their results, however, must be

interpreted in light of the presence of two alpha agonists that were also included in the local

anesthetic mixture.

We were unable to demonstrate the multi-fold prolongation of analgesia found in

one study of bupivacaine/lidocaine supraclavicular blocks29 and a trial of dexamethasone

added to epidural bupivacaine.30 An exaggerated effect may be due to the small size of those

trials, as the accuracy with which treatment effects are estimated in smaller studies is often

low. The balance of the small body of existing literature, however, supports the more

modest—but still highly clinically important—benefit observed in this trial.

As would be expected from longer block duration, maximum VRS pain scores

tended to be lower on the first postoperative day. Beyond this time, however, there appeared

  35

 

to be no lasting benefit in terms of lower in pain scores. It is important to note, however,

that the measured pain scores are maximum values over the time period, a fairly coarse

measure of patient experience over time.

The significant (but small) differences in maximum VRS pain scores seen on

postoperative day 3 in the bupivacaine groups and suggested by some of the subgroups is

concerning. It is unlikely that dexamethasone should lead to increased pain, as a significant

amount of literature describes its analgesic effect. One plausible explanation is that the

prolonged initial analgesia from interscalene blocks containing dexamethasone led to lower

initial opioid consumption. As the blocks resolved, patients would have received fewer

analgesic drugs and might thus experience higher pain scores prior to treatment with

systemic opioids. These results, however, should be interpreted cautiously in light of the

multiple tests being performed and the fact that the differences, while statistically significant,

are small and of questionable clinical importance.

Total opioid consumption over the first 72 hours also did not differ significantly

among groups. In the post-hoc analysis by procedure type, however, there appeared to be

lower opioid consumption in the arthroscopic groups. This is consistent with the less

invasive nature of arthroscopic surgery. When analyzed by site, one clinical location (Euclid

Hospital) appeared to have higher opioid consumption than the others. This most likely

reflects differences in the type of procedures performed, with the majority at Euclid

(91/106) being open and thus leading to more postoperative pain. In contrast, arthroscopic

procedures were more common at the other sites. This did not, however, lead to clear

differences in VRS pain scores between sites.

  36

 

This study is the first to examine the effect of dexamethasone on ropivacaine (or

plain bupivacaine) for interscalene blocks and is by far the largest trial to date examining

adjunctive use of dexamethasone in peripheral nerve blocks. This study was also unique in

that it was designed to detect a modest interaction between dexamethasone and the

particular local anesthetic used: an interaction that proved to be both statistically significant

and clinically important.

Dexamethasone was more effective in prolonging analgesia from interscalene blocks

using ropivacaine than bupivacaine. It is important to note, though, that this effect was

muted by the fact that the median block duration was longer with plain bupivacaine than

ropivacaine (Kaplan-Meier curve estimates 14.8 versus 11.8 hours). Thus although

dexamethasone prolonged the action of ropivacaine more than that of bupivacaine, the

combined effect of dexamethasone and either drug produced nearly the same 22 hours of

analgesia.

Despite the concern surrounding the “off-label” use of perineural adjuvants,42 the

safety profile of dexamethasone is promising. No trial has reported neurotoxicity attributable

to dexamethasone, although sample sizes to date are insufficient to detect rare outcomes and

most studies did not follow patients for weeks after surgery. In this study, with no adverse

events out of 108 patients receiving dexamethasone, the 95% confidence interval for

neurotoxicity is (0-3%). Conclusively demonstrating safety with low event rates would

require enormous sample sizes. For example, to demonstrate a doubling of the baseline

complication rate of 0.4% with 90% power, a total sample size of roughly 16,000 patients

would be required; to detect only a 50% increase would require roughly 52,000 patients.

  37

 

Reassuringly, though, animal studies demonstrate no long-term changes in nerve

structure or function after local steroid administration.43 From a mechanistic point of view,

toxicity attributed to corticosteroids may in fact be due to the particulate nature44 or vehicle

used45 in different steroid preparations—neither of which applies to the formulation of

dexamethasone (dexamethasone sodium phosphate) used in this study. Additionally,

corticosteroids have a long history of safe use in the epidural space for the treatment of

radicular pain arising from nerve root irritation46 and dexamethasone specifically has been

studied as an adjuvant to epidural local anaesthetics.30 The neurologic risk, if any, of

dexamethasone thus appears to be small. In fact, the use of dexamethasone as an adjunct to

local anesthesia for nerve blocks is discussed in popular textbooks.47-48

Systemic toxicity from a single dose of dexamethasone is also unlikely. It is

effective49 and widely administered intravenously by anesthesiologists for prophylaxis against

postoperative nausea and vomiting. Concerns about steroid-induced hyperglycemia have

been borne out in high-dose intravenous regimens,50 but have not been problematic in

practice (American Society of Anesthesiologists Annual Meeting, October 2009, Abstract

A955).

Perineural glucocorticoids are eventually absorbed and thus may exert systemic

effects. Given intravenously, several steroids have been shown to improve postoperative

pain and reduce postoperative nausea and vomiting.51-54 Any systemic analgesic effect,

however, should be minimal due to slow systemic uptake: a human volunteer trial of

intercostal bupivacaine and dexamethasone microsphere injection resulted in negligible

blood dexamethasone levels.34 Nonetheless, it remains possible (although unlikely) that some

  38

 

or even all of the block prolongation observed could have been obtained by intravenous

injection of dexamethasone.

Due to the majority of the patients being discharged before the third postoperative

day, our ability to precisely measure opioid consumption by day was limited; telephone

followup usually did not provide specific times of administration. Hence, it was only possible

to compare 72-hour opioid use between groups. Given the difference in VRS pain scores on

postoperative day 1, it is quite plausible that there were initial differences in opioid

consumption that were obscured by later opioid use. Although clinically unlikely, one

hypothesis to explain the lack of difference in overall opioid use is that patients receiving

dexamethasone, although they had less initial pain, had more pain after block resolution and

thus required more opioid pain medication over days 2 and 3. A more plausible explanation

is that the wide variation in opioid consumption, combined with the relatively small group

sizes, led to insufficient power to detect a true difference.

Due to the largely Caucasian ethnicity of the study sample, examining the effect of

ethnicity on study outcomes is difficult. Removing non-Caucasian patients from the study

sample had little effect on outcomes. Because there may be significant cultural differences in

pain expression and/or use of analgesic drugs, studies with varying ethnic composition may

be biased towards or away from a null result. Future studies should incorporate ethnicity into

their recruitment plans.

The duration of motor block was also not measured, as many patients are discharged

home after surgery and resolution of weakness is too subjective to document in the absence

of direct evaluation. This would need to be evaluated by a trained observer in future trials.

  39

 

In summary, dexamethasone prolonged analgesia from interscalene blocks using

ropivacaine or bupivacaine, with the effect being stronger with ropivacaine. However, block

duration was longer with plain bupivacaine than ropivacaine. Thus although dexamethasone

prolonged the action of ropivacaine more than that of bupivacaine, the combined effect of

dexamethasone and either drug produced nearly the same 22 hours of analgesia. This trial is

the largest to date and the first to demonstrate a difference in block prolongation between

local anesthetics. Although the toxicity profile of dexamethasone is promising, large studies

will be necessary to demonstrate its safety for perineural use.

  40

 

APPENDIX

Appendix 1A—Open Procedures: Maximum VRS Pain Scores at Rest and with Movement 

Solid horizontal lines represent medians, boxes are interquartile range, whiskers extend to the range of the data. 

 

Appendix 1B—Arthroscopic Procedures: Maximum VRS Pain Scores at Rest and with Movement 

Solid horizontal lines represent medians, boxes are interquartile range, whiskers extend to the range of the data. 

  41

 

Appendix 2A—Euclid Hospital: Maximum VRS Pain Scores at Rest and with Movement 

Solid horizontal lines represent medians, boxes are interquartile range, whiskers extend to the range of the data. 

Appendix 2B—Hillcrest Hospital: Maximum VRS Pain Scores at Rest and with Movement 

Solid horizontal lines represent medians, boxes are interquartile range, whiskers extend to the range of the data. 

  42

 

Appendix 2C—Strongsville ASC: Maximum VRS Pain Scores at Rest and with Movement 

Solid horizontal lines represent medians, boxes are interquartile range, whiskers extend to the range of the data. 

  43

 

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