Incidence of self limiting back pain in children

Pediatric Anesthesia 2010 20: 844–850 doi:10.1111/j.1460-9592.2010.03365.x

Incidence of self-limiting back pain in children
following caudal blockade: an exploratory study
T E R E S A V A L O I S M D * ,†, A N N I K O T I S R N †, M A N O N
R A N G E R R N † A N D JO H N G . M U I R F R C P C †
*Department of Anesthesia, †Acute Pain Service, The Montreal Children’s Hospital, Montreal,
Quebec and ‡Department of Pediatric Anesthesia, IWK Health Centre, Dalhousie University,
Halifax, Nova Scotia, Canada

Section Editor: Adrian Bosenberg

Summary
Background: Currently, in pediatric anesthesia, there is no evidence-
based information available to pediatric patients and their parents
regarding the incidence of back pain after neuraxial injections
performed for postoperative analgesia. Back pain postepidural
blockade has been reported in numerous studies with adult patients;
however, it has not been investigated in children. The main objective
of this study is to examine the incidence of back pain symptoms after
caudal blockade (early and late onset) in children.
Methods: Patients under the age of 18 years, who received caudal
blockade at the Montreal Children’s Hospital between July 2006 and
December 2008 were recruited in this prospective observational study.
Back pain was measured prospectively by patient self-report and
parental observation during the 15-day postoperative period. Patients,
or their parents, were contacted by phone on postoperative day 2
(POD2) and postoperative day 15 (POD15) to answer a seven-item
symptom questionnaire.
Results: In a sample of 135 children, the incidence of back pain
symptoms was 4.7% and 1.1% on POD2 and POD15, respectively.
Conclusions: The results of this study provide support that transient
self-limiting back pain after caudal blockade does occur in pediatric
patients. Clinically, this is useful information for physicians to provide
to their patients. An exploration of factors that may be associated with
back pain following caudal blockade in children is an interesting area
of future research.

Keywords: caudal blockade; back pain; pediatric regional anesthesia

Introduction
Correspondence to: Teresa Valois, MD, The Montreal Children’s In spite of a paucity of published evidence to guide
Hospital, Department of Pediatric Anesthesia, 2300 Tupper Street,
Room C-1118, Montreal, Quebec H3H 1P3, Canada (email: clinical practice, caudal blockade, a neuraxial tech-
teresa.valoisgomez@mcgill.ca). nique, is a common practice in pediatric anesthesia.

844 Ó 2010 Blackwell Publishing Ltd

BACK PAIN FOLLOWING CAUDAL BLOCKADE 845

Continuous and single-injection neuraxial tech- Wittum et al. (10) described a case where after a
niques are considered effective and are commonly single caudal injection the patient developed a
used in practice as the analgesic technique of choice. sacral osteomyelitis that resolved with antibiotic
Complications following epidural blockade have treatment.
been studied extensively in the adult population Back pain symptoms among children following
and include back pain, postdural puncture head- neuraxial blockade have not received a great deal of
ache and neurologic deficits (1–5). Back pain has attention in a research capacity. Clinically, children
been shown to occur in 18–30% of obstetric (1,2) are rarely followed-up after ambulatory surgery for
and nonobstetric (4) adults following epidural. symptoms related to the caudal procedures. This
However, prior history of back pain has been found gap in knowledge leaves the physician with little
to be highly associated with back pain following information to provide to parents and patients on
epidural, fueling controversy over whether new what to expect regarding back pain symptoms in the
onset back pain following epidural actually exists days and weeks following a caudal blockade proce-
(2–4). Complications following caudal blockade dure. The objective of this study is to prospectively
have also been studied among the pediatric popu- evaluate the incidence of back pain symptoms
lation with a reported overall rate of complications following caudal blockade in children.
of <1% (6,7). A recent review of the literature
revealed that the most common complications
Methods
among pediatric patients are bradycardia, and
apnoea (8). The author noted that while pain was The study received approval from the Institutional
not found to be a common concern among the Ethics Board of the Montreal Children’s Hospital,
pediatric population, complications are likely McGill University. Written informed consent or
underestimated, particularly among younger chil- assent was obtained for each study participant.
dren. Two large surveys on the rate and type of Patients under the age of 18 years, in American
complications following anesthesia in children have Society of Anesthesiologists Physical Status (ASA
´
been conducted (6,7). Giaufre et al. (6) examined the PS) Class I or II and who received caudal blockade
incidence of complications in 24 409 pediatric anes- before a surgery were eligible for participation in
thetics with a local or regional block procedure. The this prospective, observational study. Potential
rate of complications was low (1.5 per 1000 central study subjects were identified from the operating
blocks) with no cases of back pain reported. This room schedule of the Montreal Children’s Hospital.
study, however, did not follow up on patients Data on anesthetic technique used during surgery
posthospitalization and patients were not asked was collected by the anesthesiologist and the recruit-
specifically about back pain. In a recent update of ing team. Patients who received caudal blockade
this audit, the authors reported on the compli- were identified by the postanesthesia care unit
cations following 2278 single shot central regional (PACU) nursing staff, and the parent(s) of eligible
techniques (92% were caudal blockades) (8). Back patients were approached by the research team (TV
pain after caudal blockade was not reported. In or KR) for recruitment.
2007, Llewellyn et al. (7) conducted a national The main outcome of interest in this study was
survey examining complications following epidural back pain symptoms during the 15-day postopera-
infusion analgesia in children over a 5-year period. tive period. Back pain was measured prospectively
The authors predetermined a list of nine reportable by patient self-report and parental observation.
complications; however, back pain was not included Parents were asked to keep a diary of their child’s
as one of them. postoperative course and to complete a question-
We found two reports in the literature of back naire regarding the patient’s back pain on post-
pain after caudal blockade in children: Mackersie operative day 2 (POD2) and postoperative day 15
(9) described a case of subperiosteal hematoma (POD15). Parents were instructed to look for any
that presented as pain at injection site (sacrum), touching or pointing near the caudal area or verbal
which resolved after 24 h treatment with nonste- complains (i.e., ‘bobo’, ‘ouch’, ‘ow’) in younger
roidal analgesia, without any sequelae. Also, children.

Ó 2010 Blackwell Publishing Ltd, Pediatric Anesthesia, 20, 844–850

846 T. VALOIS ET AL.

The questionnaire included seven items assess- injected, volume injected, number of attempts and
ing the presence of back pain, discomfort at the the training level of the anesthesiologist.
injection site, pain at the injection site, itching,
bruising and nausea or vomiting as well as one
Data analysis
open-ended question intended to capture compli-
cations not assessed in the questionnaire (see Summary descriptive statistics will be used to
Appendix 1). The symptom ‘back pain’ was further present the data.
quantified by severity (mild, moderate, and severe) Continuous demographic variables (e.g., age,
and was meant to capture pain in the back (vs weight) are summarized by the arithmetic mean
pain at the injection site) resulting from the and standard deviation. Categorical data (e.g., gen-
procedure or the position the child was in during der, ASA PS, type of surgery, etc.) are summarized
the procedure. Pain and ⁄ or discomfort at the by frequency counts and percentages.
injection site referred to pain resulting from the The outcome data on back pain symptoms is
caudal technique itself. Itching and nausea ⁄ vomit- presented as frequency counts and percentages
ing are common complications following caudal (categorical variables) and mean and standard devi-
blockade and were included to differentiate back ation (continuous variables). SPSS Ver 16.0 (SPSS Inc.,
pain and other caudal technique related events, Chicago, IL, USA) was used for statistical analysis.
which may be difficult for children to distinguish. No statistical inference was performed.
Bruising has not been well documented in the
literature and was included to examine its inci-
Results
dence as well as relationship with back pain.
Patients were also asked about prior history of A total of 135 patients were recruited between July
back pain, as this is a known predictor of back 2006 and December 2008. The baseline characteris-
pain following epidural in adults (2–4). tics of the patients are displayed in Table 1. Ninety-
Parents were contacted by phone 2 days postsur- six percent of participants were boys and the mean
gery (POD2) and 15 days postsurgery (POD15) for a age of the study subjects was 31.3 ± 26.9 months
telephone audit to discuss their child’s postoperative (range 0–147 months). The most frequent type of
period as assessed on the questionnaire and diary. surgery was orchidopexy (23%) followed by hernia
Telephone audits were conducted by one of three repair (21%), hypospadias repair (20%) and then
members of the research team, who were blinded to circumcision (15.6%). The remaining surgeries were
the details of the caudal blockade technique. Parents infrequent (<9% each).
were asked if their child was experiencing any of the Details of the caudal technique are given in
symptoms on the questionnaire on that day. Parents Table 2. Although there was some variability, most
were further queried on all reported events to ensure patients (82.2%) received a mean of 11.7 ml of
correct classification of the symptoms and to assess bupivacaine 0.25% + epinephrine 1 : 200 000. Sev-
the need for medical follow-up. enty percent of the patients required only one
They also had an opportunity to add any other attempt at the caudal blockade, and 20% required
observations they noted during the postoperative two attempts.
period, which were not captured on the question-
naire. A maximum of three attempts were made to
Response rates
contact the parents on POD2 and POD15, after
which point the patient was considered a non- Response rates for the postoperative telephone audit
responder. were 78% (106 ⁄ 135) at POD2 and 70% (94 ⁄ 135) at
Data was also collected on patient age, weight, POD15. Parents were the sole respondents in the
ASA PS, type and duration of surgery and position telephone audit. There were no relevant differences
during surgery. clinically in demographic variables or caudal tech-
Details of the caudal technique were collected, nique details between the responders and non-
including type of needle, needle gauge, solution responders at POD2 or POD15.



Table 1 Table 2
Patient characteristics Caudal technical details

Patient Mean ± SD Type of needle N (%)
Age (months) 31.3 ± 26.9 IV cannula 120 (89.5)
Weight (kg) 14.3 ± 6.5 Spinal needle 3 (2.3)
Gender N (%) Hypodermic needle 1 (0.7)
Male 130 (96.3) Caudal needle 6 (4.4)
ASA N (%) Blunt needle 3 (2.2)
Physical Status 1 111 (85.3) Whitacre 1 (0.7)
Physical Status 2 19 (14.1) Needle Gauge N (%)
Type of surgery N (%) 20 1 (0.7)
Orchidopexy 31 (22.9) 22 119 (92.2)
Hernia repair 28 (20.7) 24 6 (4.6)
Hypospadias repair 27 (20.0) 25 3 (2.3)
Circumcision 21 (15.6) Solution injected N (%)
Hydrocelectomy 11 (8.1) Bupivacaine 0.25% + epinephrine 1 : 200 000 111 (82.2)
Hydrocelectomy + hernia 5 (3.7) Bupivacaine 0.125% + epinephrine 1 : 400 000 18 (13.3)
Club feet 3 (2.2) Bupivacaine 0.125% + epinephrine 1 : 200 000 5 (3.7)
Correction of buried penis 2 (1.5) Epimorphine 1 (0.7)
Ureter reimplantation 1 (0.7) Inserter (operator) N (%)
Cystoscopy 1 (0.7) Staff 78 (57.7)
Laparotomy 1 (0.7) Fellow 34 (25.2)
Pyeloplasty 1 (0.7) Resident 19 (14.1)
Orchidopexy + circumcision 1 (0.7) Resident + staff 4 (2.9)
Chordee repair 1 (0.7) Number of attempts N (%)
Position during surgery N (%) 1 86 (70.5)
Supine 127 (94.0) 2 24 (19.7)
Left lateral decubitus 6 (4.4) 3 8 (6.5)
Right lateral decubitus 1 (0.7) 4 1 (0.8)
Other 1 (0.7) 5 1 (0.8)
6 2 (1.6)
Volume injected Mean ± SD
Volume (ml) 11.7 ± 5.45
Back pain symptoms
The incidence of all back pain symptoms combined
(back pain, pain at injection site and discomfort at Table 3
injection site) in our study population was 4.7% Reports of complications following caudal blockade

(5 ⁄ 106) at POD2 and 1.1% (1 ⁄ 94) at POD15 (Table 3). POD2 POD15
(n = 106) (n = 94)

POD2 N (%) N (%)

Total patients back pain symptoms 5 (4.7) 1 (1.1)
One patient reported back pain at POD2, and four
Back pain 1 (0.9) 1 (1.1)
patients reported discomfort and ⁄ or pain at the Pain at injection site 2 (1.9%)a 0
injection site. All reports of back pain were consid- Discomfort at injection site 4 (3.8%)a 0
ered mild in severity. The ﬁve patients who reported Bruising 3 (2.8) 0
Itching 4 (3.8) 2 (2.1)
back pain symptoms at POD2 are described in Nausea or vomiting 9 (8.5) 0
Table 4. Four of the ﬁve patients were boys with an Limitation of activity 5 (4.7) 0
age range from 1.3 to 7.2 years. The surgeries a
Two patients had both pain and discomfort at injection site (See
included orchidopexy (n = 2), hydrocelectomy Table 4 for further details).
(n = 2) and hernia repair (n = 1). All patients were
in ASA PS 1. Sixteen nonback pain symptoms were
reported by another 13 patients: 3 (2.8%) reports of
POD15
bruising, 4 (3.8%) reports of itching and, there were
more reports of nausea and vomiting (n = 9, 8.5%). All reported symptoms at POD2 were transient and
Four patients reported limitation of activity that was had resolved by day 15 postcaudal blockade. One
reported spontaneously. patient (1.1%) reported new onset back pain on



POD15, and two patients (2.1%) reported new onset

14 ml Bupivacaine 0.25% + epinephrine 1 : 200 000
itching.
One serendipitous finding was the presence of
Injection volume and solution and motor block in the immediate postoperative period,
which 5 (4.7%) parents reported spontaneously with
concerns owing to its duration despite our PACU
nurses having explained this side effect at the
hospital.

Discussion
Despite the controversy that back pain following
epidural generates in adults, in particular the
obstetric population (2,11,12,13), there has been
little research on this area in the pediatric popula-
tion. We report the presence of self-limiting back
Needle: type; gauge

22
22
22
22
22

pain in 4.7% (n = 5) of children 2 days after caudal
cannula;
cannula;
cannula;
cannula;
cannula;

blockade and in 1% (n = 1) of children 2 weeks
later. Of the five patients reporting back pain
symptoms at day 2, four of these were pain or
IV
IV
IV
IV
IV

discomfort at the injection site, likely related to the
caudal technique itself (local inflammation of the
position ⁄ duration

Supine ⁄ 105

skin and the subcutaneous tissue) (10). Only one
Supine ⁄ 90
Supine ⁄ 90
Supine ⁄ 40

Supine ⁄ 30
Surgery:

(min)

patient reported back pain not related to the
injection site, positioning of the patient could also
have played a role in this finding; however,
duration and procedure were similar among the
Hydrocelectomy

Hydrocelectomy

five patients. Another 13 unique patients (12%)
Hernia repair
Orchidopexy

Orchidopexy

reported 16 events of bruising, itching and ⁄ or
Surgery

1 = back pain; 2 = discomfort at injection site; 3 = pain at injection site.

nausea ⁄ vomiting at 2 days postcaudal blockade.
This resulted in a total of 17% of the study
population reporting at least one symptom related
ASA PS, American Society of Anesthesiologists Physical Status

to their ambulatory surgery 2 days postsurgery. All
ASA PS

of these symptoms were transient and had resolved
1
1
1
1
1

by day 15 postcaudal blockade. One patient
reported new onset back pain on POD15, and two
Wt (kg)

patients reported new onset itching.
19.8
10.5
14.0
13.6
25.0
Patients with back pain symptoms at POD2

Less than 1% of children are expected to have
complications following caudal blockade (6,7). While
(years)

complications following anesthesia have been
Age

1.3
2.1
3.3
7.2
4.7

looked at to a certain extent (6,7), they are consid-
ered to be underestimated in the literature (8). This
Female
Male
Male
Male
Male
Sex

study has attempted to obtain an evidence-based
estimate of the rate of complications following
caudal blockade. The results of this study support
Back pain
symptom

the assertion that complications following anesthesia
2; 3
2; 3
1
2
2

are likely underestimated in the pediatric popula-
Table 4

tion. Up to 17% of children should expect to have
Pt

some symptoms in the short-term period following
1
2
3
4
5



caudal blockade, including 5% who are expected to common when dealing with children (14). When
experience mild pain in the back area. trying to infer what their child may be experiencing,
We looked at key demographic variables between parents have a strong propensity to color what they
patients who reported back pain symptoms at POD2 are observing with their own preconceived mean-
(n = 5) and patients who reported no back pain ings. Thus, when analyzing and discussing results of
symptoms (n = 101) to see if there were any obvious parental reports, this important limitation should be
differences. Because of the small number of patients taken into account.
reporting back pain, it is difficult to draw conclu- In addition, merely participating in a study can
sions on differences between the two groups. How- affect the outcomes. The awareness of the study
ever, patients who reported back pain symptoms often influences the participant’s behavior, often
tended to be slightly older than those who did not referred to as the ‘Hawthorne effect’ which relates
report back pain (3.7 vs. 2.7). This was mainly to the effect of being observed or looking for
because of one older patient with back pain who was cues ⁄ indicators ⁄ behaviors, being cared for, or
7.2 years old. Other than this difference, which is receiving increased attention and support (15). It is
largely attributed to the one patient, the five patients difficult to quantify the extent with which the
who reported back pain symptoms at POD2 did not Hawthorne effect may have influenced the out-
differ in any known or clinically significant way comes and its consequence could be an overestima-
from patients who did not report back pain. tion of the outcomes. Although this is an important
Although there is discrepancy regarding the factor that may bias our results and limit the
causal relationship between epidural blockade and generalizability of our findings, the low incidence
back pain, there is agreement that prior history of of our main outcome seem to indicate that the
back pain predisposes to back pain following epid- Hawthorne effect seems to have had minimal
urals in the adult population (2–4). As expected influence in our findings.
among a pediatric population, all of the children in
this study reported no prior history of back pain.
Conclusions and areas of future research
At the end of our audit, we discover yet another
Limitations
outcome in pediatric anesthesia that supports the
Our sample included 135 patients who agreed to promotion of follow-up of patients after ambulatory
participate in this study. The average age of the surgery (day surgery). We know from the literature
participants was 2.7 years. The young age of the that serious complications following caudal block-
participants required that in most cases there was ade are rare (<1%) (6,7,10). However, our study
parental involvement in the assessment of pain, and shows that up to 17% of pediatric patients may have
this imposes certain limitations to our study. nonserious caudal blockade–related symptoms dur-
Seventy-eight percent and 70% of study partici- ing the 2 -week follow-up period, including 5% who
pants completed the telephone audit at POD2 and can expect to experience back pain and ⁄ or discom-
POD15, respectively. fort at the injection site.
The potential for selection bias exists in any The findings from this study lead us to believe
response rate <100% participation. In an attempt to that there is need for a more thorough follow-up of
determine if the results of our study were biased our patients after anesthesia care to be able to better
because of a difference between patients who understand the impact of our anesthesia practices.
responded and patients who did not respond to An exploration of factors associated with back pain
the telephone audits, we examined key variables symptoms following caudal blockade in children is
between these two groups at POD2 and POD15. No an interesting area of future research.
differences in clinical features could be identified,
supporting our belief that the risk of selection bias in
Acknowledgments
this study is minimal.
Inferring pain from various behaviors can be quite Donna Coffin, MSc and Roula Cacolyris assisted in
challenging and complex, which is a situation quite the editing and preparation of the manuscript for



submission. We would like to thank Julie Brouillard 15 McCartney R, Warner J, Iliffe S et al. The Hawthorne effect: a
randomized, controlled trial. BMC Med Res Methodol 2007; 7:
for her collaboration for the completion of this study.
30.

References Accepted 6 June 2010
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