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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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