REPORTS OF ORIGINAL INVESTIGATIONS

Transversus abdominis plane block does not improve early or latepain outcomes after Cesarean delivery: a randomized controlledtrial

Le bloc dans le plan du muscle transverse de l’abdomenn’ameliore pas les douleurs precoces ou tardives aprescesarienne : un essai randomise controle

Dolores M. McKeen, MD • Ronald B. George, MD •

John Colin Boyd, MSc • Victoria M. Allen, MD •

Aaron Pink, MD

Received: 14 June 2013 / Accepted: 31 March 2014 / Published online: 24 April 2014

� Canadian Anesthesiologists’ Society 2014

Abstract

Objectives Cesarean delivery is a common surgical

procedure with anticipated substantial postoperative

pain. The addition of a transversus abdominis plane

block (TAPB) to a multimodal analgesic regimen that

includes intrathecal morphine may provide improved early

pain outcomes and decrease the risk of chronic post-

surgical pain. The purpose of this research was to assess

the ability of an ultrasound-guided TAPB with low-dose

ropivacaine to decrease early postoperative pain, opioid

consumption, and risk of developing persistent pain when

compared with a placebo block.

Methods Eighty-three women were randomly assigned to

either a treatment (0.25% ropivacaine) or control group

(0.9% saline) in this double-blind trial, and 74 women were

included in the final analysis. Ultrasound-guided TAPBs were

performed with an injection of 20 mL of study solution per

side. The primary outcome measures of this study were: pain

at rest and pain after movement measured with a numeric

rating scale, results of the Quality of Recovery-40 (QoR-40)

questionnaire, and opioid consumption at 24 hr. These were

used with an a priori sample size calculation to detect a 30%

reduction in pain scores, a 10% improvement in QoR-40

score, and a 50% reduction in opioid consumption. Health

quality and physical functioning were assessed using the Short

Form 36 (SF-36�) Health Survey at 30 days and six months.

Results Assessment at 24 hr after Cesarean delivery

revealed no clinically important differences between

groups in postoperative pain, QoR-40, or opioid

consumption. There were no clinically important

differences between groups regarding measures of nausea,

pruritus, vomiting, urine retention (2, 24, and 48 hr

postoperatively), 24-hr QoR-40 sub-dimensions, or the SF-

36 Health Survey (30 days and six months postoperatively).

Conclusions Ultrasound-guided TAPB did not improve

postoperative pain, quality of recovery, or opioid

consumption 24 hr following surgery. Similar health and

functioning (SF-36) at 30 days and six months were

reported by both groups. This trial was registered at

ClinicalTrials.gov number: NCT01261637.

Resume

Objectifs L’accouchement par cesarienne est une

procedure chirurgicale courante ou l’on anticipe une

Author contributions Dolores M. McKeen, Ronald B. George,Victoria M. Allen, and Aaron Pink contributed to the study design.Dolores M. McKeen, Ronald B. George, and Aaron Pink contributedto data collection. Dolores M. McKeen and Ronald B. Georgecontributed to data analysis. Dolores M. McKeen, Ronald B. George,J. Colin Boyd, and Victoria M. Allen contributed to the interpretationof results. Dolores M. McKeen, Ronald B. George, and J. Colin Boydcontributed to drafting the manuscript. All authors providedfeedback.

D. M. McKeen, MD (&) � R. B. George, MD � J. C. Boyd, MSc

Department of Women’s & Obstetric Anesthesia, Dalhousie

University, IWK Health Centre, 5850/5980 University Avenue,

P.O. Box 9700, Halifax, NS B3K 6R8, Canada

e-mail: dolores.mckeen@iwk.nshealth.ca

V. M. Allen, MD

Department of Obstetrics & Gynaecology, Dalhousie University,

IWK Health Centre, 5850/5980 University Avenue, P.O. Box

9700, Halifax, NS B3K 6R8, Canada

A. Pink, MD

Faculty of Medicine, Dalhousie University, Halifax, NS, Canada

123

Can J Anesth/J Can Anesth (2014) 61:631–640

DOI 10.1007/s12630-014-0162-5

importante douleur postoperatoire. L’ajout d’un bloc dans

le plan du muscle transverse de l’abdomen (TAP) a un

protocole antalgique multimodal incluant la morphine

intrathecale pourrait ameliorer les douleurs precoces et

diminuer le risque de douleur postoperatoire chronique.

L’objectif de cette etude etait d’evaluer la capacite d’une

TAP guidee par echographie, utilisant une faible dose de

ropivacaıne, a diminuer la douleur postoperatoire precoce,

la consommation de morphinique et le risque de

developpement de douleur persistante comparativement a

un bloc avec un placebo.

Methodes Quatre-vingts-trois femmes ont ete

randomisees dans le groupe de traitement (ropivacaıne

0,25 %) ou dans le groupe temoin (serum physiologique

0,9 %) dans une etude a double insu et 74 femmes ont ete

incluses dans l’analyse definitive. Les TAPB guidees par

echographie ont ete pratiquees par injection de 20 mL de

la solution etudiee de chaque cote. Les criteres

d’evaluation principaux de cette etude etaient les

suivants : douleur au repos et douleur apres mouvement

mesurees avec une echelle d’evaluation numerique, les

resultats du questionnaire de la Qualite de la

convalescence-40 (QoR-40) et la consommation de

morphinique a 24 h. Ces criteres ont ete utilises avec un

calcul de taille d’echantillon a priori concu pour detecter

une reduction de 30 % des scores de douleur, une

amelioration de 10 % du score du QoR-40 et une baisse

de 50 % de la consommation de morphinique. La qualite

de la sante et le fonctionnement physique ont ete evalues a

l’aide d’une enquete de sante avec le Formulaire abrege

36 (SF-36�) a 30 jours et six mois.

Resultats L’evaluation effectuee 24 heures

apres l’accouchement par cesarienne n’a revele aucune

difference cliniquement importante entre les groupes pour

la douleur postoperatoire, le QoR-40 ou la consommation

de morphinique. Il n’y a pas eu de difference cliniquement

importante entre les groupes concernant les mesures de

nausees, prurit, vomissements, retention d’urine (a 2 h,

24 h et 48 h postoperatoires), QoR-40 a 24 h ou de

l’enquete de sante avec le Formulaire abrege 36 (30 jours

et 6 mois postoperatoires).

Conclusions La TAP guidee par echographie n’a pas

ameliore la douleur postoperatoire, la qualite de la

convalescence ou la consommation de morphinique 24 h

apres l’intervention chirurgicale. Des scores similaires de

sante et de fonctionnement (SF-36) ont ete decrits dans les

deux groupes a 30 jours et 6 mois. Cette etude a ete

enregistree sur le site www.clinicaltrials.gov:

NCT01261637.

It is recognized that pain during childbirth contributes

significantly to the occurrence of acute and chronic pain

experienced by women worldwide.1 Evidence suggests that

severe acute pain, particularly after Cesarean delivery

(CD), may contribute to the development of chronic post-

surgical pain (CPSP) and postpartum depression.2

Cesarean delivery is a common surgical intervention in

Canada. The rate of (CD) in Canada has increased from

21.9% (2001/2002) to 27.8% (2009/2010),3 and while CD

rates in Canada have recently stabilized, the incidence of

obesity and advanced maternal age, both risk factors for

CD, continue to increase.4-6

Women are known to be at higher risk for severe

postoperative pain.7 In recent publications, there has been

an attempt to characterize the scope of the problem, i.e., to

define, assess the incidence, and investigate the

neurobiological mechanisms of acute post-surgical pain

and the development of CPSP after CD.1,8,9 These

observations emphasize the need to optimize acute pain

management during delivery as well as to identify

individual risk factors to prevent the development of

CPSP.10

Optimal postoperative analgesia regimens for CD

require safe and effective analgesia to prevent

postoperative morbidity so as to facilitate early

mobilization and infant care (breastfeeding and maternal-

infant bonding).11 Pain management achieved solely

through opioids may contribute to adverse maternal and

perinatal events, especially in breastfeeding infants.

Optimal multimodal analgesia regimens and local

anesthesia techniques may minimize or eliminate these

adverse outcomes.12,13 Despite the use of neuraxial opioids

in routine care in Canada, women still experience

significant breakthrough pain and have associated side

effects of nausea, vomiting, and pruritus.14,15

Recently, use of the transversus abdominis plane block

(TAPB) with local anesthetics (e.g., bupivacaine,

ropivacaine) and either a landmark technique (triangle of

Petit) or ultrasound guidance to block the T6-L1 sensory

nerve roots that innervate the lower anterior abdominal

wall have emerged as an effective way to limit initial

postoperative pain after a variety of abdominal surgeries.16

Despite a number of publications with varying

methodologies on TAPB in CD, the efficacy of TABP in

this population is uncertain.17-21 Interpretation of current

publications may be confounded by differences in block

technique and success, type and total dose of local

anesthetic, and inclusion of co-analgesics, including

multimodal analgesics and neuraxial opioids (i.e.,

intrathecal morphine [ITM]). While TAPB alone has

been found to be inferior with respect to acute pain

outcomes when compared with ITM, it was associated with

decreased side effects.22 In two studies that assessed the

benefit of TAPB amongst patients who received ITM,

Costello et al. used an ultrasound-guided approach, while

McMorrow et al. used the originally described landmark

632 D. M. McKeen et al.

123

approach.18,21 Neither group found benefit; however, block

failure and its impact was not assessed, and only one study

evaluated chronic pain six weeks postoperatively.18,21

Consequently, additional studies are needed to determine

whether low doses of local anesthetic in TAPB can be

effective as well as to consider success rates of TAPB

using ultrasound, the benefit of TAPB with co-analgesics

inclusive of ITM / multimodal analgesia, and the impact on

CPSP outcomes.

We hypothesized that the addition of bilateral ultrasound

TAPB using low-dose 0.25% ropivacaine as part of routine

multimodal postoperative analgesia, inclusive of ITM,

would significantly decrease acute surgical pain as

measured by lower pain scores, opioid consumption, and

improved quality of recovery in the first 24 hr

postoperatively. We also planned to explore the impact of

TAPB on the development of CPSP by assessing physical

functioning at 30 days and six months postoperatively.

Accordingly, patients undergoing elective CD with

spinal anesthesia were recruited for the study, and to test

this hypothesis, all patients were to receive 0.1 mg ITM

and multimodal analgesia with ultrasound-guided TAPB

and either 0.25% ropivacaine or 0.9% saline placebo.

Methods

Patients

Research Ethics Board (REB) approval was obtained (IWK

Health Centre REB #1004605 April 15th, 2009). Clinical

Trial registration for this research can be found at www.

ClinicalTrials.Gov (NCT01261637).A Patients scheduled

to undergo CD with planned spinal anesthesia were

approached by research personnel and recruited to partic-

ipate. Eligibility criteria included all patients who were

non-labouring, C 18 yr old, minimum 37 weeks gesta-

tional age, American Society of Anesthesiologists (ASA)

status I or II, and English speaking. Exclusion criteria

included morbid obesity (body mass index C 45 kg�m-2),

emergency CD, severe maternal cardiac disease, significant

obstetric comorbidities, failed spinal anesthesia, and

enrolment in any other studies. A screening log based on

the suggested format in the CONSORT Statement was

maintained to document the number of patients approached

for study enrolment and reasons for refusal.23 After pro-

viding informed consent, patients were assigned a study

number in order of recruitment.

Randomization into either the control (0.9% saline

placebo) or treatment (0.25% ropivacaine) group was

achieved by opening sealed opaque envelopes labelled with

the sequential study numbers. Blinded study group

allocation (A or B) was indicated inside the sealed

envelope. Blinding and matching of the group allocation

was determined by the IWK Health Centre Pharmacy

Department using a computer-generated block randomized

table. Blocks were permuted at ten patients per block with

equal allocation of patients between the two groups. On a

monthly basis (or as needed if supply was exhausted

earlier), the pharmacy supplied sterile blinded study drug

syringes labelled TAP Block Study Drug ‘‘A’’ or ‘‘B’’.24

Study protocol

Prior to the CD, all patients received antacid prophylaxis,

and standard monitors were applied. The spinal anesthetic

technique was standardized and consisted of hyperbaric

bupivacaine 12 mg, fentanyl 15 lg, and preservative-free

morphine 100 lg. Anesthetic management, including

adequacy of spinal block and subsequent operative

delivery, was performed in the usual manner. At the

conclusion of the procedure, each patient received

ketorolac 30 mg, ondansetron 4 mg, acetaminophen

1,000 mg, as well as bilateral TAPBs from one of two

investigators (D.M. or R.G.).

Bilateral TAPBs were performed under ultrasound

guidance using a 38-mm linear high-resolution ultrasound

probe (M-Turbo Ultrasound, SonoSite, Hitchin, UK) and a

100-mm 20G Tuohy needle. Using aseptic precautions, the

Tuohy needle was inserted in an anteroposterior direction

along the long axis of the probe (in plane). The appropriate

tissue plane was identified and observed distending (deep to

the fascial plane between the interior oblique and transversus

abdominis) with an incremental injection of 20 mL of study

solution.24 Bandages were placed over the injection sites.

Postanesthesia care unit (PACU) and ward orders

included routine neuraxial opioid protocol for monitoring

respiratory rate, sedation scores, and hemodynamic

variables, and standardized orders for postoperative

analgesia included Naprosyn 250 mg q8 h,

acetaminophen 1,000 mg q6 h, and oxycodone 2.5-5 mg

q6 h prn. Prior to each patient’s discharge from the PACU

(once spinal motor block had regressed), one of the

investigators (D.M. or R.G.) assessed the adequacy of the

TAPB. Evidence of inadequate TAPB was unilateral or

bilateral sensation to cold (ice) below T10.

Measures

Research personnel unaware of the patients’ randomization

or adequacy of block assessment collected data until the

A www.ClinicalTrials.Gov (NCT01261637) trial registration was not

congruent with the final study protocol and did not include cumulative

opioid consumption at 24 hr postoperatively as a primary outcome.

US guided tap block in cesarean delivery 633

123

patients left the PACU (minimum two hours), then 24 hr

and 48 hr postoperatively via a ward visit. In accordance

with IMMPACT guidelines, pain intensity was measured

with an 11-point numeric rating scale (NRS) (0 = no pain;

10 = pain ‘‘as bad as you can imagine’’) and a verbal rating

scale (VRS) (none, mild, moderate, or severe).25,26 Pain

intensity was measured at rest (supine) and after movement

(log roll). Nausea intensity was assessed using an NRS

anchored at 0 (no nausea) and 10 (nausea ‘‘as bad as you can

imagine’’).26 Vomiting episodes were recorded separately.

Pruritus was assessed at 24 hr and 48 hr with a four-point

scale.27 At 24 hr, patients were asked to complete a Quality

of Recovery-40 (QoR-40) questionnaire that provides an

extensive efficient evaluation of a patient’s quality of

recovery after anesthesia and surgery.28 The QoR-40 scores

can range from 40-200, with higher scores representing

better recovery. Data regarding cumulative oxycodone

tablet consumption were recorded at two, 24, and 48-hr

intervals and converted to oral morphine equivalents at a

ratio of 1:1.5 oxycodone to morphine.29,30 Forty-eight hours

after surgery, patients were asked about their satisfaction

with postoperative pain relief using an NRS anchored at 0

(totally unsatisfied) and 10 (totally satisfied). After

discharge, research personnel contacted patients via

telephone at 30 days and six months to complete a five-

minute Short Form-36 Health Survey (SF-36�). The SF-36,

an 11-question (36 item) measure of health-related quality

of life, is the most commonly used generic measure of

health-related quality of life.25

Statistical analysis

The superiority of pain scales vs opioid consumption as a

surrogate measure of acute pain is unclear.25 For this

reason, we have chosen four primary outcomes; the two

pain scores, the QoR, and cumulative opioid consumption

at 24 hr. As the multiple primary outcomes were to be

interpreted individually, no adjustment for multiplicity was

necessary (i.e., all were required to reach statistical

significance at 0.05).

Sample size calculations

An a priori two-tailed sample size calculation with a

significance level of a = 0.05 and b = 0.20 was completed

for all four measurements at the 24-hr postoperative

assessments. Based on data from Girgin et al., where

intravenous patient-controlled analgesia postoperative

opioid was used for 24 hr following CD with 0.1 mg

ITM, parturients consumed an average (SD) of 28 (18) mg

of morphine.31 Assuming a 50% reduction in opioid

consumption, 28 subjects per group were required for an

estimation of opioid consumption at 24 hr postoperatively.

Based on data from Eisenach et al., parturients who

underwent CD reported a maximum (SD) NRS (worst

pain) of 7.1 (2.3) at 24 hr.2 Assuming a 30% reduction in

NRS, 19 subjects per group were required for an estimation

of maximum NRS pain at 24 hr postoperatively. Based on

personal communication and data from Myles et al., an

average (SD) postoperative QoR score of 167 (23) was

expected.28 Assuming a reduction in QoR score of 10%, 29

subjects per group were required to estimate QoR at 24 hr

postoperatively. Using the largest sample size estimate and

accounting for attrition, violations, and block failure (10%),

we planned to recruit a minimum of 34 patients per group

(total sample size = 68).

Student’s two-sample t test was used for comparison of

the means of continuous normally distributed data.

Categorical data were analyzed using the mid-P variant

of Fisher’s exact test.32 Odds ratios were estimated using

conditional maximum likelihood estimation, and mid-

P exact confidence limits were calculated.33 Most

statistical analyses were performed using GraphPad Prism

version 5.0 (GraphPad Software, San Diego, CA, USA).

The mid-P exact tests were performed using OpenEpi

version 2 (open source calculator). For each of the four

primary outcomes, P \ 0.05 was considered statistically

significant. A value of P \ 0.001 was used for the analyses

relating to other outcomes to account for multiple other

outcomes and repeated testing over time.

Results

Patients

One hundred thirty-seven patients were approached to

participate in this study; 83 patients consented, 51 declined,

and three were further excluded based on study inclusion

and exclusion criteria. Data from nine patients were

withdrawn/not collected due to deviations from the study

protocol: failed spinal (n = 4); no investigator available

(n = 1); surgical complication requiring general anesthesia

(n = 1); abnormal blood work (n = 1); standardized

postoperative analgesia protocol not followed (n = 1);

attrition at follow-up (n = 1). As a result, data from 74

patients were available for protocol analyses (placebo

n = 39; treatment n = 35, Figure).24 All patients were

similar in anthropometric measures, ASA status, and

gravidity/parity at baseline (Table 1). Among participants,

intraoperative spinal anesthesia levels were determined to be

T4-T6, with no patient requiring additional intraoperative

analgesia supplementation.

The primary outcome measures of pain, opioid

consumption, and quality of recovery assessed at 24 hr

are summarized in Table 2. Pain scores at 24 hr were

634 D. M. McKeen et al.

123

slightly higher in the TAPB 0.25% ropivacaine group.

These differences were not statistically significant, and the

confidence interval ranges rule out clinically important

decreases in pain (C 2 points) with the use of ropivacaine.

Opioid consumption (expressed as morphine equivalents)

at 24 hr was slightly higher in the TAPB 0.25% ropivacaine

group; these differences were not statistically or clinically

significant. The global QoR-40 scores at 24 hr

postoperatively were also clinically similar. The

secondary outcome measures of health-related quality of

life collected at a time distant from surgery are also

summarized in Table 2. Total scores in the SF-36 Health

Survey were similar between groups at both 30 days and

six months postoperatively.

Additional information regarding pain intensity, opioid

consumption, and quality of recovery at two different time

periods is summarized in Table 3. The group receiving

ropivacaine reported less pain at rest, less pain with

movement, and had lower morphine consumption at two

hours than the placebo group. This situation was reversed

at 24 and 48 hr. Given the likely non-Gaussian distribution

of data related to morphine equivalents, median values

were also considered. At two hours, the median use was

zero for both groups. At 48 hr, the median [IQR] quantity

of morphine equivalents consumed was 15 [0.0-30.0] mg in

the 0.25% ropivacaine group and 0.0 [0.0-7.5] mg in the

placebo group. Nevertheless, all of the differences were

small and none were statistically significant.

Figure CONSORT 2010 Flow

diagram of patient enrolment,

allocation, follow-up, and

analysis

Table 1 Patient characteristics

Measure Ropivacaine 0.25% (n = 35) Placebo (n = 39)

Age (yr) 32.1 (5.3) 31.4 (5.8)

Weight (kg) 87.7 (18.5) 87.4 (14.8)

Height (cm) 162.6 (6.4) 164.0 (5.2)

ASA Status I 20 (57.1%) 27 (69.2%)

II 15 (42.9%) 12 (30.8%)

Gravidity (n) 1 / 2 / 3 / 4 / 5 1 / 1 / 11 / 16 / 6 2 / 1 / 12 / 15 / 9

% 2.9 / 2.9 / 31.4 / 45.7 / 17.1 5.1 / 2.6 / 30.8 / 38.5 / 23.1

Parity (n) 0 / 1 / 2 / 3 7 / 21 / 7 / 0 10 / 18 / 10 / 1

% 20 / 60 / 20 / 0 25.6 / 46.2 / 25.6 / 2.6

ASA = American Society of Anesthesiologists. Data are presented as mean (SD); median [interquartile range]; n (%)

US guided tap block in cesarean delivery 635

123

We observed no difference in the occurrence of adverse

outcomes of nausea, vomiting, and pruritus and observed a

small, not clinically important difference in the occurrence

of urine retention (Table 4). While sub-dimensions of the

QoR-40 were similar, at 24 hr postoperatively, lower

physical comfort scores were observed in the 0.25%

ropivacaine group compared with placebo, but these were

not clinically different. The SF-36 scores on both the

physical and mental dimensions were similar at 30 days

and six months postoperatively (Table 5).

Severe pain (NRS [ 6) at rest and after movement is

summarized in Table 6. At 48 hr, 20% of patients in the

0.25% ropivacaine TABP group reported severe pain

(NRS [ 6), 17.4% more than those who received placebo

TAPB. Patient satisfaction 48 hr following surgery was

similar between groups (data not shown).

Discussion

In this study, we assessed the effect of the addition of

ultrasound-guided TAPB with 0.25% ropivacaine to a

Table 2 Primary and secondary outcomes at 24 hr postoperatively

Measure n (R/P) Ropivacaine 0.25% Placebo Estimated Difference 95% Confidence Interval P value

Primary Outcomes

NRS Pain at Rest 33/39 2.2 (1.5) 1.7 (1.6) 0.4 (0.4) -1.16 to 0.30 0.24

NRS Pain after Movement 33/39 4.7 (2.2) 3.8 (2.3) 0.9 (0.5) -2.0 to 0.13 0.08

Morphine Equivalents 35/39 15.5 (20.2) 13.4 (14.6) 2.1 (4.1) -10.21 to 6.02 0.61

Quality of Recovery-40 34/39 173 (12) 177 (10) 3.6 (2.6) -1.65 to 8.89 0.17

Secondary Outcomes

SF-36 Total 30 days 34/38 68 (13) 72 (16) 4.16 (3.48) -2.78 to 11.10 0.24

SF-36 Total 6 months 35/36 86 (15) 87 (16) 0.73 (3.62) -6.50 to 7.95 0.84

NRS = numeric rating scale; R/P = ropivacaine/placebo. Data are presented as mean (SD) unless otherwise indicated. All data analyzed by

Student’s two-sample t test

Table 3 Secondary outcomes of pain and morphine consumption at 2

and 48 hr postoperatively

Measure n

(R/P)

Time

(hr)

Ropivacaine

0.25%

Placebo

NRS

Pain at Rest 35/39 2 2.0 (2.1) 3.5 (2.4)

35/39 48 2.1 (1.9) 1.1 (1.5)

Pain after Movement 34/38 2 3.6 (2.7) 4.7 (3.0)

35/39 48 4.3 (2.1) 3.2 (2.0)

Morphine Equivalents 35/39 2 1.4 (2.9) 2.9 (4.3)

(0.0 - 7.5) (0.0 - 17.5)

35/39 48 18.6 (21.4) 6.8 (12.0)

(0.0 - 107.5) (0.0 - 42.5)

NRS = numeric rating scale; R/P = ropivacaine/placebo. Data

presented as mean (SD) and (min - max)

Table 4 Nausea, pruritus, vomiting, and urine retention

Measure n

(R/P)

Time

(hr)

Rating

(/10)

Ropivacaine

0.25%

Placebo

Nausea 35/39 2 0/1-4/5-8 26/5/4 33/5/1

33/39 24 0/1-4/5-8 28/4/1 38/0/1

34/39 48 0/1-4/5-8 27/4/3 37/1/1

Vomiting 35/39 2 2 (5.7%) 2 (5.1%)

35/39 24 2 (5.7%) 2 (5.1%)

35/39 48 1 (2.9%) 1 (2.6%)

Pruritus 34/39 2 0/1/2/3 11/11/10/2 13/14/10/2

33/39 24 0/1/2/3 12/9/11/1 17/13/9/0

35/39 48 0/1/2/3 28/4/3/0 37/0/2/0

Urine Retention 29/28 24 3 (10.3%) 1 (3.6%)

29/28 48 3 (10.3%) 1 (3.6%)

Data presented as rating / n or n (%). R/P = ropivacaine/placebo

Table 5 Secondary outcomes of sub-dimensions of SF-36 and

Quality of Recovery-40

Category n (R/P) Ropivacaine

0.25%

Placebo

Quality of Recovery-40

Emotional State 34/39 40 (4) 41 (3)

Physical Comfort 34/39 50 (5) 52 (4)

Psychological Support 33/39 34 (2) 34 (2)

Physical Independence 34/39 18 (2) 18 (3)

Pain 34/39 31 (3) 32 (2)

SF-36 30 days

Physical 34/38 61 (2) 66 (3)

Mental 34/38 75 (2) 77 (2)

SF-36 6 months

Physical 35/36 84 (2) 85 (3)

Mental 35/36 82 (3) 83 (3)

Data presented as mean (SD). R/P = ropivacaine/placebo

636 D. M. McKeen et al.

123

multimodal approach (inclusive of ITM) to postoperative CD

analgesia. At 24 hr, the pre-specified time point of interest, the

TAPB group had higher pain scores and opioid consumption

and poorer physical functioning compared with placebo;

however, the differences were small and not clinically

important. The confidence intervals for the between-group

differences suggest that clinically important advantages of

TAPB with 0.25% ropivacaine are unlikely.

Scores on the secondary endpoint SF-36 questionnaire

assessing CPSP outcomes at 30 days and six months were

similar and, while exploratory, do not support any benefit

in terms of long-term improvement in functional health and

wellbeing. Similar rates of side effects, including nausea,

pruritus, vomiting, and urine retention, were observed

among all patients. It was reassuring that there were

relatively few occurrences of these adverse outcomes.

Studies of the TAPB technique have reported varying

degrees of success in improving opioid consumption, and

results similar to the current findings have been

shown.17,19,21,34,35 Several studies inclusive of ITM

reported the inability of TAPB to improve pain scores in

the initial 24 hr after surgery.18,21,22 Specifically, Singh

et al. completed an ultrasound-guided TAPB study using

low-dose 0.25% and 0.5% ropivacaine inclusive of ITM

that showed no benefit in pain scores at 24 hr and up to six

weeks with TAPB at either local anesthetic dose.36

We observed slightly higher pain scores in the 0.25%

ropivacaine TAPB group at 24 and 48 hr. This may be a

chance occurrence or may represent a real phenomenon. In

keeping with the duration of action of ropivacaine, the

0.25% ropivacaine TAPB likely delayed return of

abdominal wall pain sensation for up to two to six hours

after initial return of sensation from spinal anesthesia.B

This may have allowed TAPB patients to reduce or delay

early (2-24 hr) opioid use (the desired TAPB effect), yet

with a possible undesired higher opioid consumption

secondary to ‘‘rebound pain’’. Rebound pain phenomenon

has been reported after knee reconstruction with femoral

nerve block, and this was further confirmed with

ropivacaine perineural block in rats.37,38 After perineural

block regression, patients may take larger doses of opioids

to ‘‘catch up’’ to attain therapeutic opioid levels.

Two other alternative explanations can be considered.

Patient expectations may influence their pain perceptions

and postoperative recovery. Transversus abdominis plane

block regression occurs when patients are comfortable and

expecting pain to improve over time rather than worsen.

Transversus abdominis plane block may allow patients to

start to mobilize earlier (desired effect), yet this increased

mobility after TAPB regression may result in an increased

perception of pain. Regardless of the cause, our findings

suggest that TAPB with 0.25% ropivacaine produces no

benefit at 24 hr postoperatively and a possible disadvantage

at 48 hr postoperatively in this population.

The current findings are relevant to the diverse body of

data in the literature related to TAPB following CD.

Differences in block technique and success rates, local

anesthetic type and total dose, as well as the inclusion of

co-analgesics, including multimodal analgesics and

neuraxial opioids, confound interpretation of current

TAPB publications in this CD population.

As accurate placement of local anesthetic in the

transversus abdominis facial plane is critical to its

ultimate success, the technique used to determine its

location warrants consideration. While the first descriptions

of the TAPB technique used anatomical landmarks to

locate the Triangle of Petit, anatomical differences, the

gravid abdomen, and an increasing prevalence of obesity

contribute to difficulties with palpation, particularly in the

pregnant population.16,17,39,40

First described by Hebbard et al., the use of ultrasound

to guide and confirm needle position is a promising

addition to the TAPB technique to improve block accuracy,

efficiency, and safety.41-43 There have been suggestions

that negative studies failing to show TAPB benefit in CD

studies may in fact be due to TAPB failure itself secondary

to inaccurate needle placement or inability of TAPB,

particularly the ultrasound approach to cover L1 nerve

roots.44 It has been recommended that success of TAPB be

routinely assessed in further studies.44,45

Table 6 Secondary outcomes of incidence of severe pain (numeric rating scale [ 6/10)

Measure n (R/P) Time (hr) Ropivacaine 0.25% Placebo Risk Difference 95% confidence interval

Pain at Rest 35/39 2 1 (2.9%) 4 (10.3%) -7.4% -18.4 to 3.6

33/39 24 0 (0%) 1 (2.6%) -2.6% -7.5 to 2.4

35/39 48 0 (0%) 0 (0%) 0.0% 0.0 to 0.0

Pain After Movement 34/38 2 5 (14.7%) 11 (28.9%) -14.2% -32.9 to 4.5

33/39 24 9 (27.3%) 6 (15.4%) 11.9% -7.1 to 30.8

35/39 48 7 (20.0%) 1 (2.6%) 17.4% 3.3 to 31.6

Data presented as n (%). R/P = ropivacaine/placebo

B NAROPIN� Prescribing Information, Table 7. Data on file. 451112E/

Revised: November 2012. Available from URL: http://www.naropin-us.

com/pdf/Naropin_PI_451112E_Nov_2012.pdf (accessed March 2014).

US guided tap block in cesarean delivery 637

123

This current study attempted to assess TAPB duration

and failure rates by dermatome sensory testing to cold

using ice.46 This assessment was conducted after regression

of spinal anesthesia and after the patient was evaluated as

discharge ready (two hours after PACU admission). Spinal

anesthesia block regression, as part of PACU discharge-

ready criteria, includes a modified Bromage score of 5

(knee flexion / hip extension allowing five-second pelvic

lift).47 We found 56% and 76% block success rates in the

placebo and 0.25% ropivacaine groups, respectively. The

success of TAPB in 56% of the placebo group indicates

that this assessment technique was confounded by residual

spinal sensory block. We therefore cannot accurately report

TAPB failure rates. We can comment that TAPB failure

designation was liberal (lack of cold sensation had to be

bilateral for block success), and the two-hour improvement

in the ropivacaine within group NRS/VRS suggests likely

high rates of TAPB success. Subgroup analysis with

removal of TAPB failures (0.25% ropivacaine group

n = 26, data not shown) was similar to the per protocol

analysis and did not reveal any relevant differences for pain

at rest (95% confidence interval [CI]: -1.26 to 0.36), pain

after movement (95% CI: -2.31 to 0.06), morphine

equivalent consumption (95% CI: -11.77 to 6.87), or

QoR (95% CI: -2.61 to 9.04).

To evaluate the duration of TAPB, the patients self-

assessed numbness of the abdominal wall and location of

postoperative pain by means of shading a dermatome

diagram in a self-recorded paper diary at six, 12, and 24 hr

after delivery. On the initial 24-hr ward visit, research

personnel found \ 25% compliance. While the patient

diary itself and data related to the duration of TAPB were

collected, data analysis was not undertaken due to attrition

and missing data points.

Special attention should be paid to reduce the dose of

local anesthetic given its increased potential to induce

systemic toxicity in this highly vascularized and ‘‘at risk’’

pregnant population.48-50 The higher concentration (0.5%

ropivacaine) used for TAPB usually approximates

3 mg�kg-1, exceeds manufacturers’ recommendations, and

may result in plasma concentration levels capable of causing

central nervous system toxicity.B Seizures have occurred

following TAPB in ‘‘at risk’’ patient populations.B,48

While preliminary reports using high-dose local

anesthetic TAPB (0.75% bupivacaine) showed success in

improving pain management and opioid consumption, the

authors acknowledge that the dose used was higher than

that recommended by the manufacturer, but they insist on

its safety.17,51 Follow-up studies attempting to improve on

those findings with lower doses of bupivacaine and

ropivacaine have yielded less promising results,

suggesting the effectiveness of the block may be

intimately linked to dosage.18,21,22,34,50 Several reports of

TAPB with varying levels of bupivacaine (0.25-0.75%)—

known to be more potent than ropivacaine—following CD

have not shown consistent improvement in postoperative

analgesia.17,20-22,52,53 Three reports using moderate- to

high-dose local anesthetic in TAPB (0.5% and 0.375%

ropivacaine) were unable to show an improvement in pain

management following CD up to 48 hr

postoperatively.18,19,34 Considering the threat of

neurotoxicity presented by TAPB using 0.5%

ropivacaine, elicitation of the minimum effective dose of

local amino amide anesthetic is important, and consensus is

needed on the optimal dosage of ropivacaine for the

efficacy of ultrasound-guided TAPB.18,19,34-36

Meta-analyses by Mishriky et al. and Abdulla et al.,

both published in 2012, stratified for the impact of

including ITM on the efficacy of TAPB.54,55 Further

meta-analysis of additional recent publications stratifying

for technique, local anesthetic dosage, multimodal

analgesia, and ITM is needed as these mixed

methodologies currently confound interpretation of TAPB

publications in this CD population.

In the study by Costello et al., residual abdominal pain

was assessed at six weeks, and TAPB did not reduce the

incidence of chronic pain.18 Importantly, our study

provides an assessment of TAPB for long-term health

benefits and prevention of persistent pain at 30 days and

six months. While this study was not powered to detect

significant differences and was considered exploratory, we

can state that we observed no differences in SF-36 follow-

up data at either time point, with almost identical scores six

months postoperatively (Table 5).

There were several limitations recognized in this study.

An alternative strategy to assess block success needs to be

determined. Block success was confirmed by bilateral lack

of cold sensation to ice below T10 after motor block

regression. We did not attempt to assess the lower level,

i.e., L1 coverage of the block. Residual spinal sensory

block and occasional unilateral block (assigned as TAPB

block failure) confounded the assessment of TAPB

adequacy. Unfortunately, this was not discovered until

data analysis and un-blinding of group allocation. Singh

et al. utilized a ‘‘satisfactory review’’ by two anesthesia

staff confirming the ultrasound image of correct needle

placement and local anesthetic spread, which, as a

surrogate marker of block success, is an alternate yet un-

validated approach.

The relatively low values of pain intensity at rest

(NRS* 1-3 /10) reported by the majority of women

through 48 hr of recovery (in association with multimodal

analgesia inclusive of ITM) may have affected the

evaluation of the clinical impact of the TAPB technique.

We emphasize that almost one-third of women in both

groups reported severe pain after movement. Additionally,

638 D. M. McKeen et al.

123

measures capable of isolating psychological and social

influences on the experience of pain associated with

childbirth may be beneficial in future research.

In our study, the use of only one treatment group and a

placebo group limits our ability to discuss specific effect of

anesthetic dose compared with the general effectiveness of

the TAPB technique. As TAPB is relatively new, general

recommendations, including type of local anesthetic and

dosage and standards of practice, e.g., the optimal TAPB

approach, have yet to be established.56

In conclusion, amongst women undergoing CD

inclusive of ITM and multimodal analgesia, ultrasound-

guided TAPB with 0.25% ropivacaine does not improve

self-reported pain, QoR, and opioid consumption when

compared with placebo in the first 24 hr postoperatively.

Transversus abdominis plane block may be associated with

greater pain and opioid consumption later in recovery at

24-48 hr. Continued evaluation of anesthetic dosage is

needed for further exploration of the dose-response

relationship as well as ongoing assessment of the

effectiveness of the ultrasound-guided vs the landmark

technique to improve postoperative analgesia in this CD

population.

Acknowledgements We are grateful to Dr. Colleen O’Connell and

Dr. Christy Woolcott for their assistance with statistical analyses. This

study was completed at the IWK Health Centre. Dr. McKeen

acknowledges the support of the Canadian Anesthesiologists’ Society

(CAS) GE Healthcare Canada Research Award in Perioperative

Imaging Operating Grant. Dr. George held an IWK Recruitment &

Establishment Grant and acknowledges the support of a CAS Career

Scientist Award. Dr. Allen held a Canadian Institutes of Health

Research New Investigator Award and a Dalhousie University Clinical

Research Scholar Award. Dr. Pink acknowledges Dalhousie University

Medical Research Foundation Summer Research Studentship Funding.

Conflicts of interest None declared.

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