This retrospective analysis examined 509 patients who received interscalene catheters for ambulatory shoulder surgery. Adverse events occurred in 34 patients (6.7%), most commonly catheter dislocation diagnosed in the recovery room or at home with pain. Twelve patients (2.4%) were re-admitted to the hospital, most commonly for pain. The study found that with appropriate patient selection, trained staff, and protocols for managing adverse events, interscalene catheters can be safely used to provide analgesia for ambulatory shoulder surgery.

1. Original Article
A retrospective analysis of 509 consecutive interscalene catheter
insertions for ambulatory surgery
P. Marhofer,1
W. Anderl,2
P. Heuberer,3
M. Fritz,4
O. Kimberger,1
D. Marhofer,5
W. Klug5
and
J. Blasl6
1 Professor, 4 Medical Student, 5 Staff Member, Medical University of Vienna, Vienna, Austria
2 Director of the Surgical Division, 3 Staff Member, 6 Director of the Anaesthesia Division, St. Vincent Hospital,
Vienna, Austria
Summary
Effective pain therapy after shoulder surgery is the main prerequisite for safe management in an ambulatory setting.
We evaluated adverse events and hospital re-admission using a database of 509 interscalene catheters inserted during
ambulatory shoulder surgery. Adverse events were recorded for 34 (6.7%) patients (9 (1.8%) catheter dislocations
diagnosed in the recovery room, 9 (1.8%) catheter dislocations at home with pain, 2 (0.4%) pain without catheter
dislocation, 1 (0.2%) ‘secondary’ pneumothorax without intervention and 13 (2.6%) other). Twelve (2.4%) patients
were re-admitted to hospital (8 (1.6%) for pain, 2 (0.4%) for dyspnoea and 2 (0.4%) for nausea and vomiting), 9 of
whom had rotator cuff repair. A well-organised infrastructure, optimally trained medical professionals and appropri-
ate patient selection are the main prerequisites for the safe, effective implementation of ambulatory interscalene
catheters in routine clinical practice.
.................................................................................................................................................................
Correspondence to: P. Marhofer
Email: peter.marhofer@meduniwien.ac.at
Accepted: 29 July 2014
Introduction
Interscalene blockade of the brachial plexus for
shoulder surgery is a standard regional anaesthetic
method for peri-operative pain therapy [1–6]. Single
injection interscalene blockade facilitates intra-opera-
tive and short-term postoperative analgesia for these
painful surgical procedures [7–9]. Co-administration
of additive drugs such as dexmedetomidine to local
anaesthetic agents is currently under investigation,
but although the first clinical results are promising
[10, 11], they are not labelled for perineural adminis-
tration, and so continuing analgesia after shoulder
surgery is only currently possible using interscalene
catheterisation [12].
Organised peri-operative facilities are required in
order to facilitate experienced practitioners’ inserting
interscalene catheters without significant time delays to
operating lists, and to avoid the logistical problems of
postoperative management.
Fast-track ambulatory shoulder surgery is econom-
ically and clinically beneficial for hospitals and
patients, reducing the incidence of hospital acquired
infections, and facilitating remobilisation and rehabili-
tation [1–3]. Interscalene catheter usage is an impor-
tant component in such management, providing
optimal postoperative pain therapy, in turn enabling
early physiotherapy, resulting in optimal surgical out-
come. However, clear guidance for catheter care at
© 2014 The Association of Anaesthetists of Great Britain and Ireland 41
Anaesthesia 2015, 70, 41–46 doi:10.1111/anae.12840

2. home is required for safe and effective implementation
of this technique in daily clinical practice.
We conceived a retrospective database analysis of
consecutive patients receiving interscalene catheters for
ambulatory shoulder surgery, in order to ascertain the
prevalence and type of adverse events encountered
with their use and reasons for re-admission to hospital,
with the aim of developing further guidance for the
safe use of this technique.
Methods
Following approval from the local ethical committee of
the St. Vincent Hospital, Vienna, Austria, recorded
data were analysed for all consecutive interscalene
catheter insertions for ambulatory shoulder surgery at
the St. Vincent Hospital between December 2011 and
August 2013 (21 months). Study data were compiled
from several databases: Medlinq anaesthesia recording
system (Medlinq Softwaresystem Corp., Hamburg,
Germany: patient list; sex; secondary dose of local
anaesthetic in the post-anaesthesia care unit; ultra-
sound confirmation of catheter position before hospital
discharge; ultrasound investigation of ipsilateral
hemidiaphragm movement (yes/no); ultrasound inves-
tigation of the ipsilateral lung sliding movement (yes/
no)); SAP patient recording system (SAP Inc.,
Walldorf, Germany: main diagnosis; body mass index
(BMI; ASA physical status; type of surgery; position
during surgery; time of interscalene catheter tip place-
ment; re-admission to hospital within 12 h postopera-
tively); MCC Meierhofer documentation system
(Meierhofer Inc., Munich, Germany: operation time);
and the printed medical record of the individual
patients (visual analogue pain score (VAS), catheter-
related problems, new insertion of catheter in the
post-anaesthesia care unit).
Our routine management protocol for patients
undergoing ambulatory shoulder surgery is as follows.
In addition to general health screening, patients are
scheduled for surgery at their pre-operative visit
10–14 days before admission, provided they are of
ASA physical status 1–3, have a third party to care for
them after discharge, have no contraindications to
interscalene blockade and agree to follow the written
instructions provided to them regarding postoperative
pain management and catheter handling.
Patients are transferred to the post-anaesthesia
care unit 60 min before surgery for interscalene block
insertion, having established venous access and stan-
dard cardiorespiratory monitoring (electrocardiogram,
non-invasive blood pressure, oxygen saturation).
An initial ultrasound scan of the relevant anatomical
structures for interscalene brachial plexus blockade was
performed with a SonoSite M-Turbo transportable ultra-
sound equipment and a 38-mm 13–6 MHz HFL linear
ultrasound transducer (SonoSite Inc., Bothell, WA,
USA). Thereafter, the puncture area and the ultrasound
transducer was prepared in a sterile manner (Safersonic
Conti sterile sonography cover; Safersonic Inc., Ybbs,
Austria) and the nerve roots identified between the ante-
rior and middle scalene muscles in a transverse view.
After raising a skin wheal with 2 ml mepivacaine 1%
(MepinaestTM
purum 1%; Gebro Pharma Inc., Fieberb-
runn, Austria), an 18-G facet tip needle (‘Plexolong Nan-
oline according to Meier’ set for continuous peripheral
nerve blockade; Pajunk Inc., Geisingen, Germany) was
introduced out-of-plane, with caudal needle orientation.
After ultrasound confirmation of extra-epineural
distribution of 5 ml mepivacaine 1% below the superfi-
cial cervical fascia, a 20-G catheter was introduced 4 cm
distally to the tip of the needle and the needle was
withdrawn. Subsequently, 10 ml ropivacaine 0.5% (Rop-
inaestTM
; Gebro Pharma Inc., Fieberbrunn, Austria) was
administered intermittently through the catheter under
direct ultrasound guidance. Correct distribution was
confirmed by local anaesthetic administration adjacent
to the C5–7 nerve roots, with the catheter carefully
withdrawn until this was achieved [13]. The catheter
was fixed using sterile tapes and a perineural catheter
fixation set (BBraun Perifix catheter fixation set; BBraun
Melsungen AG, Melsungen, Germany), with a 0.2-lm
filter was connected at the proximal end of the catheter
to provide sterile administration of local anaesthetics.
After transfer into theatre, general anaesthesia was
introduced with 100 lg fentanyl and 2–4 mg.kgÀ1
propofol. A laryngeal mask airway was inserted and
anaesthesia maintained with 1 MAC sevoflurane in an
oxygen/air mixture, with pressure controlled or spon-
taneous ventilation. The patients were positioned in
the lateral or beach-chair position, depending on the
surgical procedure and the individual surgeons’ prefer-
ence. General anaesthesia was used in preference to
42 © 2014 The Association of Anaesthetists of Great Britain and Ireland
Anaesthesia 2015, 70, 41–46 Marhofer et al. | Ambulatory interscalene catheters

3. sedation for ease of airway management under condi-
tions of limited airway access.
The position of the catheter and the level of pain
were evaluated 90–120 min postoperatively. An
additional bolus of 10 ml ropivacaine 0.5% was admin-
istered if the VAS was > 0. Using the same method
described above, a new interscalene catheter was
inserted if the original catheter had dislocated, or
become kinked/obstructed. A disposable Post-Opera-
tive Pain Control Pump (Beeline Disposable Post-
Operative Pain Control Pump 110 ml, Moog Medical
Devices Group, Salt Lake City, UT, USA) was
connected to the interscalene catheter with a fixed
infusion rate of 4 ml.hÀ1
ropivacaine 0.2%.
An ultrasound investigation was performed in all
patients before discharge, to confirm positive move-
ment of the hemi-diaphragm [14, 15] and to exclude
pneumothorax by observing lung sliding [16–18]. Clear
instructions about catheter management were provided
again before discharge, together with emergency
telephone numbers.
Catheters were removed on the first postoperative
day, when all patients revisited the hospital for surgical
and anaesthesia consultation, during which VAS score
and patient peri-operative satisfaction scores (1, satis-
fied; 6, dissatisfied) were recorded. Further analgesia
was prescribed at the individual physicians’ discretion.
The catheter insertion site was assessed for signs of
infection or haematoma 10 days after surgery when
the surgeon removed cutaneous sutures. R 2.15.1 (R
Foundation for Statistical Computing, Vienna, Austria)
was used for statistical analysis. A p < 0.05 was con-
sidered statistically significant.
Results
We analysed data from 509 consecutive patients
undergoing ambulatory shoulder surgery during the
21-month period. The median (IQR [range]) age of
patients was 54 (46–62 [17–87]) years. Two hundred
and seventy (53%) patients were ASA 1, 234 (46%)
ASA 2 and 5 (1%) ASA 3. The median (IQR [range])
BMI of patients was 27 (24–29 [16–44]) kg.mÀ2
. The
surgical procedures undertaken are shown in Table 1.
Catheter-related adverse events and reasons for
hospital re-admission within 12 h postoperatively are
shown in Tables 2 and 3.
Overall, patients’ satisfaction with peri-operative
care was high, with 473 (93%) describing themselves
‘very satisfied’ or ‘satisfied’, 25 (5%) ‘moderately satis-
fied’ and only 11 (2%) ‘dissatisfied’.
No interscalene catheter-related signs of infection
or haematoma were observed by surgeons 10 days
postoperatively.
Discussion
This is the largest consecutive case series of interscalene
catheters for shoulder surgery in an ambulatory setting,
and reports an uneventful peri-operative course in 93.3%
of cases with 93% of patients describing themselves satis-
fied with their peri-operative care. Among the 6.7% of
patients who had an adverse outcome, most commonly
insufficient analgesia at home with or without catheter
dislocation (2.2%), none suffered more than minor
harm. We identified rotator cuff repair as the procedure
with the highest apparent re-admission rate to hospital.
Shoulder surgery is commonly associated with
severe, unpredictable peri-operative pain and pro-
longed hospital stay [19–26]. Modern anaesthetic man-
agement involves interscalene brachial plexus blockade,
with or without general anaesthesia, the reliability and
safety of which is improved by ultrasound-guided
placement [27, 28] compared with previously described
techniques, such as the perpendicular needle guidance
(Winnie) technique [29]. The safe, correct placement
of perineural catheters is facilitated by ultrasound
guidance [13] and advancement of the catheter in a
medial direction [30].
Table 1 Surgical procedures undertaken (n = 509).
Values are number (proportion).
Rotator cuff repair 190 (37.3%)
Subacromial decompression 99 (19.4%)
Removal of calcification 73 (14.3%)
Acromioclavicular joint resection 49 (9.6%)
Tenotomy or tenodesis 46 (9.0%)
Capsular plication 15 (2.9%)
Capsulotomy 10 (2.0%)
Debridement of the supraspinatus tendon 10 (2.0%)
Labrum refixation 4 (0.8%)
Removal of screw(s) 4 (0.8%)
Arthrolysis 3 (0.6%)
Diagnostic arthroscopy 3 (0.6%)
Shoulder prosthesis 2 (0.4%)
Acromioclavicular stabilisation 1 (0.2%)
© 2014 The Association of Anaesthetists of Great Britain and Ireland 43
Marhofer et al. | Ambulatory interscalene catheters Anaesthesia 2015, 70, 41–46

4. Previous case series have reported the use of inter-
scalene catheters in various settings. Bryan et al. found
a 9.7% prevalence of adverse events in a retrospective
analysis of 144 catheters used for ambulatory shoulder
surgery [1]. Fredrickson et al. performed a prospective
study of 300 interscalene catheters, where 88 of
patients were managed in an ambulatory setting [3],
among which long-term neurological sequelae were
observed in three cases, with one case of infection
relating directly to an interscalene catheter.
We were encouraged to find such a low rate of
adverse events in our study. Although pain and dysp-
noea are of subjective concern to patients, our provi-
sion of well-structured patient follow up allowed rapid
re-assessment and treatment of patients with these,
and other types of event.
The most serious of our events, an apical pneumo-
thorax, was not apparent on ultrasound before patient
discharge, and we can only speculate that catheter
migration after discharge may have been causative
[31].
Catheter dislocation was the most common
adverse event associated with interscalene catheters.
We have previously found a 5% rate of dislocation in
volunteers [13], similar to the 3.6% observed in this
study, half of which occurred in the immediate post-
operative period. We suggest that that the catheter dis-
location rate increases with the length of use, although
further studies are required to confirm this.
We attribute the apparent safety and effectiveness
of interscalene catheter use at our hospital to the com-
prehensive package of patient care that supports their
use, involving structured communication channels
between patients and healthcare professionals, highly
trained anaesthetists, highly trained surgeons capable
of short procedure times, highly trained anaesthesia
nursing staff, effective computer-based data capture, a
protocol for the fast and effective treatment of adverse
events, and a protocol for suitable patient selection.
We justify the relatively short time of catheter use
(24 h) with reference to the time course of pain after
shoulder surgery [32] and our own clinical experience.
A longer duration of catheter use is associated with
more administrative demands, more complications
(e.g. catheter dislocation, catheter disconnection and
obstruction, infections, neurological sequelae) and
more hospital re-admissions consequent to these.
Table 2 Interscalene catheter-related adverse events. Values are number (proportion).
Adverse event Description
Insufficient postoperative analgesia – catheter
re-inserted
9 (1.8%) Mild adverse event after surgery
Insufficient analgesia at home without catheter
dislocation
9 (1.8%) Five patients were re-admitted during the first 12 postoperative
hours
Insufficient analgesia at home with catheter
dislocation
2 (0.4%) Two patients were re-admitted during the first 12 postoperative
hours, one catheter was reinserted
Catheter dislocation at home with no significant
pain
7 (1.4%) Diagnosis of catheter dislocation after 24 h
Pain at catheter insertion site 1 (0.2%)
Distal disconnection of catheter at home 2 (0.4%) In both cases the patients reported mild to moderate pain
Pneumothorax 1 (0.2%) No invasive intervention required
Subjective dyspnoea at home 3 (0.6%) Two patients were re-admitted during the first 12 postoperative
hours and interscalene infusion was stopped
Total 34 (6.7%)
Table 3 Reasons for re-admission within 12 h of hospi-
tal discharge after surgery (n = 509). An apical pneu-
mothorax was diagnosed by ultrasound in one of the
two patients admitted with dyspnoea, but required no
further intervention. Values are number (proportion).
Reason for
re-admission Surgical procedure
Shoulder
pain
7 (1.4%) 6 rotator cuff repair; 1 capsular
plication 1
Hemi-thorax
pain
1 (0.2%) rotator cuff repair 1
Dyspnoea 2 (0.4%) rotator cuff repair; 1
subacromial decompression 1
Nausea and
vomiting
2 (0.4%) rotator cuff repair; 1 biceps
tenotomy
Total 12 (2.4%)
44 © 2014 The Association of Anaesthetists of Great Britain and Ireland
Anaesthesia 2015, 70, 41–46 Marhofer et al. | Ambulatory interscalene catheters

5. Postoperative use of interscalene catheters beyond 24 h
requires further investigation, as does the technique of
catheter fixation on prolonging safe catheter use (such
as tunnelling [33]), patient-controlled bolus augmenta-
tion of background ropivacaine infusion for more
painful surgical procedures (such as rotator cuff repair)
with a possible reduced incidence of re-admissions,
and co-administration effect/side-effect profile of other
analgesics, such as dexmedetomidine [11].
This retrospective consecutive case series has sev-
eral limitations. All procedures were performed in one
hospital with considerable experience of interscalene
catheterisation for shoulder surgery. The techniques
described (needle guidance, catheter fixation, postoper-
ative catheter care etc.) reflect the experience of the
one hospital, limiting extrapolation of the results to
other hospitals using other techniques for ambulatory
shoulder surgery [1, 4, 5, 34]. Nevertheless, the tech-
nique described in this series is associated with a low
hospital re-admission rate and high patient satisfac-
tion, and future prospective studies may seek to
confirm the clinical usefulness of the methodology
described.
In summary, this large retrospective consecutive
case series analysed the management of interscalene
catheters for ambulatory shoulder surgery. The inci-
dence of adverse events was 6.7% and of hospital
re-admission, 2.4%. Most of the adverse events were
pain related. Rotator cuff repair was identified as the
only predictor for unplanned re-admission to hospital.
Patient satisfaction was high. Well-trained staff and a
well-organised infrastructure are the main prerequisites
for the successful and safe implementation of this tech-
nique in the daily clinical practice.
Competing interests
Departmental resources supported this study only. PM
has received honoraria for lectures from SonoSite Inc.
DM has received unrestricted grants from Pajunk Inc.
and Temena Inc.
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Anaesthesia 2015, 70, 41–46 Marhofer et al. | Ambulatory interscalene catheters