Remember the saphenous: ultrasound evaluation and intravenous site selection of peripheral veins in young children.

Abstract

The primary objective of this study was to measure the width and depth of peripheral veins using bedside ultrasound in children younger than 3 years. Secondary objectives included the evaluation of other vein and patient characteristics that may affect intravenous (IV) site selection. Assessment of nursing preferences for peripheral IV site selection was performed.
Sixty children aged 0 to 3 years who presented to an urban pediatric emergency department were enrolled. Ultrasound measurements of the transverse diameter (width) and distance from the top of the vein to the skin (depth) were recorded. Upon examination, veins were categorized as visible, palpable, detectable only by ultrasound, or not detectable. Sixteen staff nurses rated the likelihood of successful IV placement among different peripheral veins.
The mean width of saphenous veins was significantly larger than that of hand veins (2.8 vs 1.8 mm, P < 0.0001). When comparing saphenous veins to antecubital veins, no significant difference was measured between the mean width (2.8 vs 2.8 mm). The mean depth of saphenous veins was significantly greater than those of hand veins (1.9 vs 1.4 mm, P < 0.0001) and antecubital veins (1.9 vs 1.6 mm, P = 0.019). Differences in visibility and palpability were observed between different vein types. Hand veins and antecubital veins were rated by the nursing staff as the most likely sites for successful IV placement, whereas saphenous veins were among the least likely (P < 0.0001).
In children younger than 3 years, the saphenous vein is larger than hand veins and is similar in size to antecubital veins, although marginal differences in depth exist. The sonographic findings of the saphenous vein and antecubital vein suggest that either should be considered a superior first choice for IV cannulation in this age group. Knowledge of these differences is important when choosing a site for peripheral IV placement. Future studies should evaluate peripheral IV success rates by vein type with or without ultrasound guidance.

Full text

Page 1

Remember the Saphenous
Ultrasound Evaluation and Intravenous Site Selection of
Peripheral Veins in Young Children
Antonio Riera, MD,* Melissa Langhan, MD,Þ Veronika Northrup, MPH,þ
Karen Santucci, MD,Þ and Lei Chen, MD, MHSÞ
Objectives: The primary objective of this study was to measure the
width and depth of peripheral veins using bedside ultrasound in children
younger than 3 years. Secondary objectives included the evaluation of
other vein and patient characteristics that may affect intravenous (IV) site
selection. Assessment of nursing preferences for peripheral IV site selec-
tion was performed.
Methods: Sixty children aged 0 to 3 years who presented to an urban
pediatric emergency department were enrolled. Ultrasound measure-
ments of the transverse diameter (width) and distance from the top of the
vein to the skin (depth) were recorded. Upon examination, veins were
categorized as visible, palpable, detectable only by ultrasound, or not
detectable. Sixteen staff nurses rated the likelihood of successful IV
placement among different peripheral veins.
Results: The mean width of saphenous veins was significantly larger
than that of hand veins (2.8 vs 1.8 mm, P G 0.0001). When comparing
saphenous veins to antecubital veins, no significant difference was mea-
sured between the mean width (2.8 vs 2.8 mm). The mean depth of sa-
phenous veins was significantly greater than those of hand veins (1.9 vs
1.4 mm, P G 0.0001) and antecubital veins (1.9 vs 1.6 mm, P = 0.019).
Differences in visibility and palpability were observed between different
vein types. Hand veins and antecubital veins were rated by the nursing
staff as the most likely sites for successful IV placement, whereas sa-
phenous veins were among the least likely (P G 0.0001).
Conclusions: In children younger than 3 years, the saphenous vein is
larger than hand veins and is similar in size to antecubital veins, although
marginal differences in depth exist. The sonographic findings of the sa-
phenous vein and antecubital vein suggestthateither should be considered
asuperiorfirstchoiceforIVcannulationinthisagegroup.Knowledgeof
these differences is important when choosing a site for peripheral IV
placement. Future studies should evaluate peripheral IV success rates by
vein type with or without ultrasound guidance.
Key Words: catheterization, peripheral venous, ultrasound, saphenous
vein, antecubital vein, infants
(Pediatr Emer Care 2011;27: 1121Y1125)
I
difficult to perform in small children, because of the combina-
tion of small-caliber veins and poor patient cooperation. Risk
factors for difficult venous access and suggested techniques to
improve success rates have been identified in the nursing liter-
ature.1Peripheral IV success rates in children have been shown
to be around 50% on first attempt and 90% after 4 attempts.2
Young age is a known predictor for difficult IVaccess.3Differ-
ences in physical characteristics of veins, such as size and depth,
may impact success rates.
Peripheral vein selection for initial IV attempt is likely to
vary according to provider preferences. The process of periph-
eral IV site selection by medical providers is not well studied.
One review article on pediatric IVaccess suggests that the dor-
sal veinsof the hand and feet should be considered a ‘‘preferred’’
choice and that antecubital veins are among the easiest to can-
nulate. The saphenous vein is listed as another option for pe-
ripheral cannulation, although the authors imply that it is not
always visible or palpable.4No research to date has investigated
peripheral IV success rates by vein type.
There is a significant body of literature on ultrasound as-
sessment of peripheral veins in adult patients. There is good evi-
dence for improved peripheral venous cannulation rates using an
ultrasound-guided approach.5Y7Pediatric peripheral vein assess-
ment is less well studied. Two recent studies have described the
abilitytoidentifyperipheralveinsusingbedsideultrasonography.8,9
Our primary objective was to measure the width and depth
of peripheral veins using bedside ultrasound in children younger
than 3 years. A secondary aim was to investigate other variables
that may affect IV site selection such as visibility and palpability.
Athird aim was toevaluate nursing preferences for peripheral IV
site selection.
ntravenous (IV) line placement in the pediatric emergency
department (PED) is an important procedural skill. This can be
METHODS
Children aged 0 to 3 years who presented to an urban PED
at a tertiary care children’s hospital were eligible for the study. A
convenience sample of subjects was enrolled between February
and September 2009. Consent was obtained, and an informa-
tion sheet describing the reasons behind the study was provided.
Subjectswere excluded iftheyhad congenitalor limb anomalies,
experienced major trauma, had severe dehydration or shock, had
a central line, or required urgent IV placement or other resus-
citative measures. The study was approved by our institutional
human investigation committee before commencement.
Assessments on each study subject were done on either the
left or right side of the body. This was done to help minimize
potential bias in vein selection. A tourniquet was placed proxi-
mal to the vein of interest. These included the saphenous, ante-
cubital, and dorsal hand veins. A total of 3 veins, one from each
site, were evaluated per subject. Assessment of a vein’s physi-
cal appearance was recorded as one of the following: visible,
ORIGINAL ARTICLE
Pediatric Emergency Care & Volume 27, Number 12, December 2011www.pec-online.com
1121
From the *Pediatric Emergency Medicine, YaleYNew Haven Children’s
Hospital; †Pediatric Emergency Medicine, Yale University School of Medi-
cine; and ‡Biostatistics Support Unit, Yale Center for Clinical Investigation,
New Haven, CT.
Disclosure: The authors have nothing to disclose.
Reprints: Antonio Riera, MD, Pediatric Emergency Medicine, YaleYNew
Haven Children’s Hospital, 840 Howard Ave, 1st Floor, New Haven,
CT 06504 (e-mail: Antonio.riera@yale.edu).
Statistical support for this publication was made possible by CTSA
(grant UL1 RR024139) from the National Center for Research
Resources (NCRR), a component of the National Institutes of Health
(NIH), and NIH Roadmap for Medical Research. Its contents are solely
the responsibility of the authors and do not necessarily represent the
official view of NCRR or NIH. Information on Re-engineering the
Clinical Research Enterprise can be obtained from the NIH Web site.
Copyright * 2011 by Lippincott Williams & Wilkins
ISSN: 0749-5161
Copyright © 2011 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.

Page 2

palpable, seen only on ultrasound, or not detected. This assess-
ment was performed by the principal investigator before the ul-
trasound measurements. If more than 1 vein was visible over a
certain site, then the vein that appeared larger was chosen for
measurements. Visible veins were chosen over palpable veins. If
more than 1 vein was palpable over a certain site, then the easiest
to palpate was chosen. The patient’s age, sex, and weight were
also recorded. Weight was obtained from the patient’s triage
sheet.
Ultrasound Measurements
All measurements were performed with the L38 linear
probe (5Y10 MHz) of a SonoSite MicroMaxx ultrasound system
(Sonosite, Bothell, Wash). Ultrasound depth was standardized to
2.0 cm. The transverse vein diameter (width) and distance from
the top of the vein to the skin (depth) were measured (Fig. 1).
Veins were verified by exerting pressure with the linear probe
and observation of compression. This allows for differentiation
from arteries that are not as easily compressible because of their
higher pressures. After full recoil, a still image was recorded.
Widths and depths were measured on the same still image. Ul-
trasound measurements were performed by the primary inves-
tigator. In preparation for this study, consultation with a pediatric
radiology attending physician was done to corroborate feasibil-
ity and optimize imaging technique. Ultrasound experience was
obtained during a dedicated ultrasound rotation for 1 month in
the adult emergency department at YaleYNew Haven Hospital,
where ultrasound-guided peripheral IV placement is routinely
performed. Images were saved and later reviewed by a pediatric
emergency medicine attending with experience in pediatric ul-
trasound. Review included confirmation that a measurement of
a vascular structure was obtained.
Nursing Preferences
The nursing staff is predominantly responsible for periph-
eral IVaccess at our institution. Therefore, nurses from the PED
were surveyed to assess their preferences for peripheral IV
placement. This was done via a self-administered written survey
before the enrollment of subjects. The survey instrument was
reviewed for face validity by faculty members in our section
of emergency medicine. Surveys were administered to registered
nurses (RNs) while working clinically. This representative sam-
ple of RNs was asked to rank the likelihood of successful IV
placement among different peripheral veins in children younger
than 3 years. The veins to be ranked were listed as hand, ante-
cubital, saphenous, wrist/forearm, and foot. Ranking was done
on an ordinal scale, with a rank of 1 corresponding to the mostly
likely site for successful IV placement and a rank of 5 corre-
sponding to the least likely site for successful IV placement. The
respondents were asked to assume that all other patient varia-
bles were equal.
Statistical Analysis
It was estimated that 30 subjects would be needed to de-
tect a 25% difference in vein size measurements with an > of
0.017 (Bonferroni > adjustment for 3-group comparison) and
80% power, assuming an SD of the difference of 0.8 mm. We
chose to double the sample size, which allowed us to investigate
the effects of other patient characteristics in a multivariate anal-
ysis. Primary comparisons of vein width and depth by type of
vein were done with the repeated-measures analysis of variance
(ANOVA), followed by the post hoc paired t test comparisons.
Adjusted analyses were performed using the repeated-measures
(ANOVA)approach,includingage,sex,andweightinthemodels.
Analysis of the difference in the physical appearance (visible vs
palpable vs ultrasound only) between veins was done using the
nonlinear mixed-effects modeling, controlling for age, sex, and
weight of patients. Adjustment of the observed P values for mul-
tiple comparisons, due to 3 different vein types, was done with
the Tukey approach.
Nursing preferences for vein type were analyzed using the
Friedman test, followed by 10 post hoc pairwise comparisons
with the Wilcoxon signed rank test. The critical > was adjusted
using the Bonferroni correction, resulting in > G 0.005.
All analyses were performed in consultation with a biostat-
istician using SAS 9.2 (SAS, Cary, NC).
RESULTS
Sixty subjects were enrolled. Patient characteristics are listed
in Table 1. There was good patient cooperation for assessment
of all variables, including ultrasound measurements, throughout
the study.
Ultrasound Measurements
The mean width of saphenous veins was larger than hand
veins (2.8 T 0.7 vs 1.8 T 0.5 mm, P G 0.0001). The same was
observed for antecubital veins compared with hand veins (2.8 T
0.8 vs 1.8 T 0.5 mm, P G 0.0001). When saphenous vein widths
were compared with antecubital vein widths, no significant dif-
ference was detected (2.8 T 0.7 vs 2.8 T 0.8 mm, P = 0.904). The
FIGURE 1. Transverse view of a saphenous vein (hypoechoic,
round structure measuring 2.8 mm in width) with bedside
ultrasound.
TABLE 1. Demographics
Study Population N = 60
Median age (range)
Aged G1 y, n (%)
Aged 1Y2 y, n (%)
Aged 2Y3 y, n (%)
Sex, n (%)
Male
Female
Mean weight, kg
Weight G25th percentile, n (%)
Weight25thY75thpercentile,n(%)
Weight 975th percentile, n (%)
15.5 mo (range, 7 wkY36 mo)
24 (40)
24 (40)
12 (20)
31 (52)
29 (48)
10.9 (range, 4.7Y16.2)
6 (10)
28 (47)
26 (43)
Riera et al
Pediatric Emergency Care & Volume 27, Number 12, December 2011
1122
www.pec-online.com
* 2011 Lippincott Williams & Wilkins
Copyright © 2011 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.

Page 3

differences between vein widths remained significant after
adjusting for age, sex, and weight(Table2).Asweight increased,
a trend for an increase in the vein widths was observed (Fig. 2).
The mean depth of saphenous veins was greater than both
antecubital veins (1.9 T0.6 vs1.6 T 0.8mm, P= 0.019)and hand
veins (1.9 T 0.6 vs 1.4 T 0.5 mm, P G 0.0001). No statistically
significant difference was observed between antecubital and
hand veins (1.6 T 0.8 vs 1.4 T 0.5 mm, P = 0.135). The differ-
ences between vein depths remained significant after adjusting
for age, sex, and weight (Table 2). In addition, vein depth de-
creased by 0.03 mm (P = 0.007) for every 1 month of increase in
patient age and increased by 0.1 mm (P = 0.016) for every 1-kg
increase in patient weight.
Physical Characteristics
Table 3 summarizes physical characteristics of each vein.
Saphenous veins were most often identified by palpation. Ante-
cubital veins and hand veins were most often identified by visual
inspection. The comparison of hand vein visibility/palpability
(78.3%/3.3%) was statistically significant when compared with
both antecutbital veins (60%/28.3%, P = 0.002) and saphenous
veins (38.3%/55%, P G 0.001). The vein visibility/palpability
comparison between antecubital and saphenous veins was also
statistically significant with a P = 0.005. Older age was associ-
ated with increased likelihood of a vein being visible, compared
with either being palpable(P= 0.014) orseen onlyon ultrasound
(P = 0.017), regardless of vein type. All 158 veins that were
either visible or palpable were detected by ultrasound. In the
extremity sites that did not have a visible or palpable vein, 20
(91%) of 22 ultrasound attempts were successful in the detec-
tion of a peripheral vein. There was a trend for greater weight
being associated with increased likelihood of veinvisibility only
on ultrasound (P = 0.074), regardless of vein type.
Nursing Preferences
There were 16 total participants (representing 33% of the
nursing staff) with a mean of 15 years of pediatric IV placement
experience. Survey completion rate was 100% for those RNs in-
vited to participate. Significant differences in the nurses’ pref-
erence for IV placement were observed by the type of vein (P G
0.0001). Hand veins and antecubital veins were ranked as the
mostlikelysitesforsuccessfulIVplacement(PG0.001)(Fig.3).
Forearm/wrist veins were ranked third, followed by saphenous
and foot veins.
DISCUSSION
Our study quantifies the measurable physical differences
between 3 common peripheral veins in children younger than
TABLE 2. Width and Depth by Vein Type, Adjusted Analysis
OutcomeCharacteristic
Parameter
Estimate (SE), mm
P*
Vein width, mmHand
j1.1 (0.1)
j0.05 (0.1)
Reference
1.0 (0.1)
0.05 (0.1)
Reference
0.03 (0.1)
0.004 (0.01)
0.1 (0.04)
j0.2 (0.1)
0.3 (0.1)
Reference
j0.5 (0.1)
j0.3 (0.1)
Reference
j0.05 (0.1)
j0.03 (0.01)
0.1 (0.04)
G0.0001
0.859 Saphenous
Antecubital
Hand
Antecubital
Saphenous
Male sex
Age, mo
Weight, kg
Hand
Saphenous
Antecubital
Hand
Antecubital
Saphenous
Male sex
Age, mo
Weight, kg
G0.0001
0.859
0.757
0.736
0.052
0.138
0.015
Vein depth, mm
G0.0001
0.015
0.711
0.007
0.016
*Obtained from repeated-measures ANOVA, using the Tukey ad-
justment approach for multiple comparisons.
FIGURE 2. Peripheral vein width by weight.
TABLE 3. Physical Characteristics by Vein Type
Antecubital Saphenous Hand
Visible
Palpable
Seen only on ultrasound
Not detected
Total detected
36 (60)
17 (28.3)
5 (8.3)
2 (3.3)
58
23 (38.3)
33 (55)
4 (6.7)
V
60
47 (78.3)
2 (3.3)
11 (18.3)
V
60
Values are presented as n (%).
FIGURE 3. Number of times vein ranked as first or second choice
for successful IV placement.
Pediatric Emergency Care & Volume 27, Number 12, December 2011 Ultrasound Evaluation of Peripheral Veins
* 2011 Lippincott Williams & Wilkins
www.pec-online.com
1123
Copyright © 2011 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.

Page 4

3 years. These findings have important implications for pediatric
peripheral IV placement. Vein size and depth are variables that
have the potential to impact success rates. In this study, we have
demonstrated that saphenous and antecubital veins have a larger
caliber than hand veins in children younger than 3 years. Before
our study results, there were no available data to provide evi-
dence for differences in peripheral vein sizes.
The mean difference of 1.0 mm between saphenous vein
width and hand vein width is clinically important. This difference
isgreater thanthecaliberofstandard 24-and22-gaugecatheters,
which are 0.7 and 0.9 mm, respectively. Converting mean width
measurements to mean areas suggest that, on average, saphenous
veins approximate a 2.4 times larger target when compared with
hand veins in children younger than 3. Our data showed that an-
tecubital veins and saphenous veins offer the same size advan-
tage over dorsal hand veins. The measured mean differences in
depth, although statistically significant, were less than 0.6 mm
and thus not likely to generate an important clinical difference.
Although vein visibility likely plays a major role in site selec-
tion before IV placement, larger palpable veins should not be
overlooked for smaller, visible veins.
Inadditiontosizeadvantages,thesaphenousveinmayoffer
additional features that would make it a desirable option for IV
placement for infants and toddlers. The saphenous vein has a
relatively straight course, as depicted by anatomic textbooks.10It
has a reproducible location, as it runs just anterior to the medial
malleolus. We found this anatomic reproducibility to be present
with all of our study subjects. At this level of the body, neither
the dorsalis pedis nor the posterior tibialis artery is in close prox-
imity, which makes an arterial puncture highly unlikely. Finally,
in the case of pediatric resuscitations, obtaining access at the
foot of the bed would allow other providers more room to per-
form simultaneous maneuvers such as chest tube placement or
chest compressions.
Personal preferences impact the choice of IV placement
site. The saphenous vein is often used as an alternate site, after
failed cannulation of other peripheral veins. This is supported by
our survey results where, on average, highly skilled and expe-
rienced RNs ranked the saphenous vein behind hand, ante-
cubital, and forearm veins for IV placement in children younger
than 3 years. We found a high rate of clinically detectable sa-
phenous veins, as 93% were either visible or palpable. Further
research may be useful to obtain a larger sample of nursing pref-
erences and address the inconsistent findings of low saphenous
vein ranks.
Our study has several limitations. The use of a single ultra-
sound operator limits the generalizability of our study findings.
However, prior studies in adults suggest that peripheral venous
visualization by ultrasound is easily performed, and results are
reproducible.5,6Studies in children have replicated the ease by
which to identify peripheral veins via ultrasound.8,9The inter-
rater reliability of ultrasound measurements was not assessed.
A J statistic was not calculated as the saved still images of
venous structures had visible width and depth measurements on
the screen, and a second set of measurements could not be
performed. Compression alone was used as the primary means
to differentiate veins from arteries. The use of color or power
Doppler to confirm venous versus arterial flow would have
improved sensitivity.
The results of nursing preferences for IV site selection are
limited by several factors. First, although the survey was admin-
istered anonymously on separate days to nurses during a typi-
cal clinical shift, we were unable to complete participation from
the entire nursing staff. It is possible that the remaining 67%
of nurses who did not participate in our survey had different site
preferences. That said, a significant proportion of our nursing
staff gave an inferior rank to the saphenous vein. We did not
assess whether this was due to lack of exposure using this site
or lack of prior success. Second, a validated survey instrument
to assess IV site selection preferences does not exist. We devised
a simple, focused survey meant to rank veins on an ordinal scale
from 1 to 5. It is also possible that the survey results of site pref-
erences do not translate into actual clinical practice.
Attempts to objectively measure subjects’ hydration status
were not performed. Although patients with severe dehydra-
tion and/or shock were excluded, those with mild and/or mod-
erate dehydration could potentially have been enrolled as study
subjects. There is evidence that inferior vena cava volume is
affected by hydration status.11We do not know what effect, if
any, these variables had on our peripheral vein assessments
and measurements. On the other hand, comparisons of different
veins in the same individuals, as performed in our study, would
likely have controlled for these variations. Future studies may
attempt to assess the effect of hydration status on peripheral
vein sizes.
We did not compare the success rates of peripheral vein
cannulation in our study population. Further studies are needed
to prospectively evaluate successful peripheral IV cannulation
rates by site, including saphenous veins, in this age group. Ad-
ditional research should analyze the success rates of ultrasound-
guided IVattempts by peripheral vein site.
CONCLUSIONS
In children younger than 3 years, the saphenous vein is
larger than hand veins and is similar in size to antecubital veins,
whereas marginal differences in depth exist. The sonographic
findings of the saphenous vein and antecubital vein suggest that
either should be considered a superior first choice for IV cannu-
lation in this age group. Knowledge of these differences is im-
portant whenchoosing a site for peripheral IV placement. Future
studies should evaluate peripheral IV success rates by vein type
with or without ultrasound guidance.
ACKNOWLEDGMENTS
The authors thank Rob Goodman, MD (associate profes-
sor of Diagnostic Radiology and Chief of Pediatric Imaging at
YaleYNew Haven Children’s Hospital) for his guidance and sup-
port with this project.
REFERENCES
1. Kuensting LL, DeBoer S, Holleran R, et al. Difficult venous access
in children: taking control. J Emerg Nurs. 2009;35(5):
419Y424.
2. Lininger RA. Pediatric peripheral i.v. insertion success rates.
Pediatr Nurs. 2003;9(5):351Y354.
3. Yen K, Riegert A, Gorelick MH. Derivation of the DIVA score: a
clinical prediction rule for the identification of children with difficult
intravenous access. Pediatr Emerg Care. 2008;24(3):
143Y147.
4. Stovroff M, Teague WG. Intravenous access in infants and children.
Pediatr Clin North Am. 1998;45(6):1373Y1393, viii.
5. Costantino TG, Parikh AK, Satz WA, et al. Ultrasonography-guided
peripheral intravenous access versus traditional approaches in
patients with difficult intravenous access. Ann Emerg Med.
2005;46(5):456Y461.
Riera et al
Pediatric Emergency Care & Volume 27, Number 12, December 2011
1124
www.pec-online.com
* 2011 Lippincott Williams & Wilkins
Copyright © 2011 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.

Page 5

6. Keyes LE, Frazee BW, Snoey ER, et al. Ultrasound-guided brachial
and basilic vein cannulation in emergency department patients
with difficult intravenous access. Ann Emerg Med. 1999;34(6):
711Y714.
7. Brannam L, Blaivas M, Lyon M, et al. Emergency nurses’ utilization
of ultrasound guidance for placement of peripheral intravenous
lines in difficult-access patients. Acad Emerg Med. 2004;11(12):
1361Y1363.
8. Doniger SJ, Ishimine P, Fox JC, et al. Randomized controlled trial of
ultrasound-guided peripheral intravenous catheter placement
versus traditional techniques in difficult-access pediatric patients.
Pediatr Emerg Care. 2009;25(3):154Y159.
9. Schnadower D, Lin S, Perera P, et al. A pilot study of ultrasound
analysis before pediatric peripheral vein cannulation attempt.
Acad Emerg Med. 2007;14(5):483Y485.
10. Netter F. Atlas of Human Anatomy. Philadelphia, PA: Saunders Elsevier;
2006.
11. Chen L, Kim Y, Santucci KA. Use of ultrasound measurement of the
inferior vena cava diameter as an objective tool in the assessment of
childrenwithclinicaldehydration. Acad Emerg Med. 2007;14(10):841Y845.
Pediatric Emergency Care & Volume 27, Number 12, December 2011 Ultrasound Evaluation of Peripheral Veins
* 2011 Lippincott Williams & Wilkins
www.pec-online.com
1125
Copyright © 2011 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.