Use of magnifying lens to aid neonatal umbilical arterial catheter insertion.
ABSTRACT We conducted this trial to test the hypothesis that use of a magnifying lens would facilitate umbilical arterial catheter (UA C) insertion in neonates. Neonates <33 weeks' gestation requiring a UA C were randomized to conventional method of catheter insertion or an experimental method using a 2.0 X magnifying lens mounted on a headband. A total of 44 neonates (Conventional = 23, Experimental = 21) with comparable demographic characteristics completed the study. The time taken for (primary outcome) and rate of successful UAC insertion (secondary outcome) were not significantly different between the two groups (median times: conventional: 88 seconds,experimental: 70 seconds, P = 0. 734) (Success rate: conventional: 19/23 (83%) vs experimental:13/21 (63%), P = 0. 1791 Thus, our hypothesis was rejected.
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ABSTRACT: This study compared the conventional method of umbilical artery catheter placement with a side-entry method. Criteria for comparison were: (1) frequency of correct placement; (2) time required for placement; and (3) incidence of bleeding. Newborn infants less than 3 hours of age who required placement of a umbilical artery catheter were admitted into the study with parental consent. The sample size was 32 catheter attempts (16 conventional method and 16 side-entry method). The side-entry method resulted in more successful catheter placements and required less time without incidence of bleeding. With the conventional method, there were five failures to place the catheter and three incidents of bleeding, resulting in a total blood loss of 14 cc.American Journal of Perinatology 02/1990; 7(1):8-12. · 1.57 Impact Factor
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Patients and Methods
This study was designed as a randomized
controlled trial in a tertiary neonatal intensive
care unit. Ethics committee approval was
obtained prior to commencement of the study.
All neonates <33 weeks’ gestation
requiring UAC for hemodynamic monitoring
were eligible for enrolment in the study after
informed parental consent was obtained.
Neonates were excluded if there was presence
of congenital malformations (e.g., diaphrag-
matic hernia, exomphalos), known chromoso-
mal aberrations, single umbilical artery,
umbilical infection, or necrotising entero-
In the conventional method of UAC
insertion (without the use of magnifying lens)
Use of Magnifying Lens to Aid Neonatal Umbilical Arterial
L. McGlone, L. Devlin, *D.A. Doherty and S. Patole
From the Department of Neonatal Pediatrics, King Edward Memorial Hospital for Women,
Bagot Rad, Subiaco, Western Australia 6008, and *Women’s and Infant’s Research Foundation
at King Edward Memorial Hospital for Women and School of Women’s and Infant’s Health at
University of Western Australia.
Correspondence to: Sanjay Patole, Department of Neonatal Pediatrics, King Edward Memorial
Hospital for Women, Bagot Road, Subiaco, Western Australia 6008.
Manuscript received: February 5, 2003, Initial review completed: March 10, 2003;
Revision accepted: June 26, 2003.
We conducted this trial to test the hypothesis that use of a magnifying lens would facilitate
umbilical arterial catheter (UAC) insertion in neonates. Neonates <33 weeks’ gestation requiring
a UAC were randomized to conventional method of catheter insertion or an experimental method
using a 2.0 X magnifying lens mounted on a headband. A total of 44 neonates (Conventional = 23,
Experimental = 21) with comparable demographic characteristics completed the study. The time
taken for (primary outcome) and rate of successful UAC insertion (secondary outcome) were not
significantly different between the two groups (median times: conventional: 88 seconds,
experimental: 70 seconds, P = 0.734) (Success rate: conventional: 19/23 (83%) vs experimental:
13/21 (63%), P = 0.179] Thus, our hypothesis was rejected.
Key words: Arterial, Catheter, Lens, Neonates, Umbilical.
Umbilical arterial catheters (UACs) are
frequently used in neonatal intensive care
units (NICU) for continuous monitoring of
blood gases and arterial blood pressure(1-3).
The conventional method of UAC insertion
can be technically challenging and time-
consuming at a time when rapid stabilization
of the neonate is desired(4-5). Most of the
difficulties in the insertion of a UAC in
preterm neonates are due to the narrow vessel
diameter. We therefore conducted a clinical
trial to test the hypothesis that the use of a
magnifying lens will facilitate insertion of
UACs by making the vessel easier to identify
and manipulate. Our aim was to evaluate the
efficacy of a magnifying lens in reducing the
time to insertion of UAC (primary outcome)
and the frequency of successful insertion
VOLUME 4 1_ _MARCH 1 7 , 2 0 0 4
all UACs were inserted under aseptic
conditions with the neonate under a radiant
warmer as per our unit protocol. Oxygen
saturation and heart rate was monitored
continuously throughout the procedure.
Length of catheter insertion was determined
by measuring the shoulder to umbilicus
distance and referral to the graph(6). A size
3.7 or 5.0 French Guage UAC was used
depending on the size of the neonate. All
catheters were primed with normal saline
prior to insertion. After cleaning the skin with
chlorhexidine, the cord was transected
parallel to the abdomen leaving a 1 cm
umbilical stump. The cord stump was
stabilized with artery forceps and the artery
gently probed with the tip of curved iris
forceps. The forceps were allowed to spring
open, dilating the artery. The catheter tip was
then introduced into the artery and advanced
with steady pressure to the predetermined
position. Confirmation of catheter placement
was made by aspiration of free flow of blood
followed by a radiograph. The assisting
midwife timed catheter insertion using a LCD
stopwatch. The watch was started when the
cord was incised and stopped when either a
pulsatile column of blood was aspirated into
the UAC or the procedure abandoned due to
failure of arterial cannulation.
The experimental method of UAC
insertion was identical to the conventional
method of UAC insertion except for the
additional use of a commercially available
power 2.0 × magnifying lens (Megaview-
Easifit) mounted on a head mount loupe. The
mount loupe was a headband, which allows
the operator to manipulate the lens position.
The use of this device ensured sterility of the
Sample size calculations were based on
the previously published data(7) and our own
pilot data generated by monitoring UAC
insertion (n = 5 each) by two registrars with
comparable experience on 10 neonates <33
weeks gestation indicating a 10% rate of failed
insertions and a mean ± SD time of insertion
as 310 ± 132.7 sec. Group sample sizes of 22
each were estimated to achieve 82% power to
detect a 40% reduction in the insertion time
(considered clinically significant) from the
330 sec (without the use of magnifying lens)
to 200 seconds while using a magnifying lens
(common SD =144).
A two-sided Mann-Whitney test or t-test
was planned to be as appropriate depending
on the data normality, at a 0.05 significance
Neonates eligible for enrolment were
randomized into the study (stratifying for
birth weight <1000 g and >1000 g) using a
computer generated sequence of treatment
allocations (conventional or experimental
method of UAC insertion) stored in sealed
opaque envelopes that were opened after the
parental consent was obtained. Two separate
random sequences were generated to allow for
the stratification by birth weight. Four
registrars with comparable experience in level
III neonatal care participated in the study.
The primary endpoint of insertion time
was analyzed using Mann-Whitney test or
t-test, and the secondary endpoint of success
of UAC insertion was compared using Fisher
A total of 44 neonates (conventional
method = 23, experimental method = 21)
completed the study (Table 1). Overall 16
(36%) neonates were born with birth weight
<1000 g conventional: Nine (39%), experi-
mental: 7 (33%). Groups were comparable
with respect to gestational age at delivery,
birth weight, intrauterine growth retardation,
and CRIB scores.
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No significant differences were found
between the median times for successful UAC
insertion between the two study groups.
(conventional: 88 sec (IQR 50 - 192, range 24-
780), Experimental: 70 sec (IQR 55-222,
range 27-642), P = 0.734.
Similarly, there were no significant
(conventional versus experimental method of
UAC insertion) with respect to the frequency
of successful UAC insertion. (Conventional:
the two groups
19/23 (83%) vs Experimental: 13/21 (63%),
P = 0.179). The median insertion times in the
unsuccessful cases were 345 sec (IQR 205-
529, range 163-900), and 900 sec (IQR 370-
900, range 148-900) with no statistically
significant differences (P = 0.683). The
comparisons in this case however were based
on small sample sizes (n = 4 and 8).
Group comparison performed at the
completion of the study indicated that the
median (and mean) times to UAC insertion
were considerably shorter than anticipated
before the study commenced (189.6 vs 167
seconds). This resulted in only 6% power to
detect statistically significant differences
between the study arms. Approximate sample
sizes of 100 neonates per group would be
required to detect a 40% reduction in the
insertion times between median times of 187
sec and 112 sec with 80% power at 5%
significance level using a sequential design
with a single interim analysis. Given that the
insertion times achieved in the two groups
during the trial were very close and
significantly shorter than those before the
study, continuation of the study was
considered unfeasible due to the very low
TABLE I–Characteristics of Infants Requiring
(n = 23)
(n = 21)
CRIB score2 (1-4) 1 (0-6)
*value expressed as medians and interquartile ranges
(IQR = Q25 - Q75).
*SGA = small for gestational age ( <10th centile).
TABLE II–Time and Success of UAC* Insertion
(n = 23)
(n = 21)
All cases19 (83%)13 (63%) 0.179
< 1000 g
³1000g 85 (24-770)62 (27-205)0.181
*Value expressed as medians and interquartile ranges (IQR = Q25 - Q75).
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one of the two registrars whose UAC insertion
timings were used for the pilot data could not
participate in the clinical trial due to un-
expected circumstances. Though considered
comparable (with other three operators)
before the trial, the UAC insertion skills of the
replacement registrar may also have differed
significantly during the trial. The other
possibility could be an improved awareness
(benefits of inclusion in a clinical trial) with
possibly an improved performance in UAC
insertion during the study. The side entry
method described by Squire et al.(7) involves
visual identification of the umbilical arteries
through the cord stump, transection of the
Wharton’s jelly to the artery, followed by
incision only through the upper arterial wall to
expose the lumen. We have found complete
transection of the umbilical artery to be a
significant problem with this method of UAC
insertion especially in extremely low birth
weight neonates (ELBW). Our median times
and frequency of successful UAC insertions
are significantly better than those reported by
Squire et al.(7). The differences again could
be explained by variability in operator skills.
In summary given the importance of speedy
and successful vascular access in stabilization
of ELBW neonates it is important to study
methods to optimize the success of con-
ventional method of UAC insertion. Our
results emphasize the importance of consider-
ing the variability of (inter and intra) operator
skills during the study before undertaking any
We are thankful to Dr. S. Rao for
probability of finding statistically significant
differences between the study groups.
Insertion of the UAC plays a vital role in
the stabilization and management of ill
preterm neonates. Reducing the time to insert
these catheters is desirable to minimize
handling and allow rapid and appropriate
interventions for the altered cardiorespiratory
status at a critical time(4,5). Most of technical
difficulties in the insertion of UACs are
related to the small calibre of the vessel.
Vasospasm, vascular perforation, subintimal
cannulation and tunica intima invagination
have also been proposed as factors respon-
sible for failure of UAC cannulation (3,8).
Mehods to overcome the technical
difficulties in insertion of UACs have
received little attention in the past. Results of a
randomized controlled trial by Squire et al.(7)
have shown that compared with the
conventional method the side-entry method
led to successful UAC insertions more
frequently and the time to successful
insertions was significantly shorter. (Correct
placement (n/N): side entry (15/16) vs
conventional (11/16), P = 0.09), (time) to
insertion in seconds: side entry (143 ± 24) vs
conventional (330 ± 36), P = 0.01).
Our results (comparable but overall signi-
ficantly reduced insertion times compared
with our pilot data) may be explained by a
great variability between the operators which
was probably far more important than the
benefits of using a magnifying glass to aid the
UAC insertion. This was also important, as
• Use of magnifying lens does not help in reducing the insertion time or success rate for
placement of umbilical artery catheter in neonates <33 weeks.
VOLUME 4 1_ _MARCH 1 7 , 2 0 0 4
participation in the study and for obtaining
some of the parental consents.
Contributors: LM was responsible for the first and final
draft, and patient enrolment, LD contributed to the first
draft, DAD was responsible for study design, statistical
analysis, and interpretation. SP was involved in the
concept, design, and supervision of the final draft.
Competing interests: None stated.
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