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  1. Sharp, Rebecca BN, BHSc (Hons)
  2. Cummings, Melita BN
  3. Childs, Jessie BHSc, BHSc (Hons), GradDipSon
  4. Fielder, Andrea PhD, BSc, BSc (Hons)
  5. Mikocka-Walus, Antonina PhD, MA (Psych)
  6. Grech, Carol PhD, MN, BN
  7. Esterman, Adrian PhD, MSc, BSc (Hons)


Choosing an appropriately sized vein reduces the risk of venous thromboembolism associated with peripherally inserted central catheters. This observational study described the diameters of the brachial, basilic, and cephalic veins and determined the effect of patient factors on vein size. Ultrasound was used to measure the veins of 176 participants. Vein diameter was similar in both arms regardless of hand dominance and side. Patient factors-including greater age, height, and weight, as well as male gender-were associated with increased vein diameter. The basilic vein tended to have the largest diameter statistically. However, this was the case in only 55% of patients.


Article Content

Peripherally inserted central catheters (PICCs) are non-permanent vascular access devices that are used in a wide range of patient groups for longer-term treatment and the infusion of irritating medications, such as chemotherapy.1 The devices are associated with complications, such as venous thromboembolism (VTE), which interrupts treatment and is associated with morbidity and mortality.2,3 Both patient and insertion factors interact to increase the risk of VTE.4 An important insertion factor is the degree of stasis from the disruption of blood flow due to the presence of the catheter. It is thought that the catheter-to-vein ratio (proportion of the vein taken up by the catheter) is a controllable factor in the reduction of thrombosis rates in patients who have a PICC inserted.5 Current guidelines for PICC insertion recommend that the smallest-diameter catheter that meets the treatment needs of the patient be inserted into the largest-diameter vein.6 For this reason, it is necessary to identify the largest vein to insert the catheter.


Ultrasound is the preferred method for vasculature assessment. Often, however, both arms are not assessed using ultrasound before insertion. Arm and vein choice may be based on inserter or patient preference, as well as institutional guidelines.7,8 Many clinicians prefer right-sided insertion because of an easier anatomical pathway to the superior vena cava.3,9 Other clinicians most frequently insert into a vein on the left side because the patient's nondominant arm is preferred, presumably because of perceived ease of self-care.8 It is not known whether these practices use the largest vein, because there is little published literature to inform which vein might be the most suitable for PICC insertion and patient factors that influence vein diameter.



Literature investigating the effect of hand dominance on vein dimension centers on the measurement of the area of veins in the central circulation. Hand dominance or the preference for the use of 1 arm for most activities exists across the global population, with an estimated 85% identifying the right hand as dominant.10 Conflicting results have been found in research that has investigated the influence of hand dominance on axillary and jugular vein areas. A prospective, observational study by Tan et al11 involving 50 surgical patients used ultrasound to examine the effect of hand dominance on the infraclavicular axillary vein. The authors found that hand dominance did not influence the dimensions of the vein. Conversely, in the same year, a retrospective study that used computed tomography to measure the cross-sectional area of the internal jugular vein (n = 80) found that vein size was correlated with hand dominance.12 Although no research could be identified that investigated the effect of hand dominance on upper arm vein diameter, it could be surmised that hand dominance would have greater effect on the more peripheral basilic, brachial, and cephalic veins of the upper arm and that the dominant arm would have larger-diameter veins as the result of increased use.13


Arm side (right versus left) does not appear to be correlated with vein diameter in the upper arm. When the diameters of the right and left basilic veins were compared in a cadaver study in Brazil (n = 13), commensurate diameters were found on both sides.14 Similarly, in a larger retrospective study (n = 3206) with live subjects examining the diameters of the cephalic vein in a vascular patient population, comparable mean vein diameters were found on each side.15


No published research could be identified that has formally analyzed the diameter of veins used for PICC insertion by vein type. Despite this, the basilic vein is often put forward by clinicians as the largest vein and the cephalic as the smallest. Certainly, previous research indicates that the basilic vein is preferred for insertion.9,16,17 Literature investigating vein diameter for arteriovenous fistula development supports the idea that the basilic and brachial veins have greater diameters than the cephalic vein.15,18 Vein diameters were measured at the midhumeral level, which is close to the PICC insertion point, and the authors found that the brachial and basilic veins were of similar diameter (mean diameter 4.9 and 5 mm, respectively), and the cephalic vein was more than half that diameter (mean diameter 2.4 mm).15,18


To inform clinical practice, there is a need to provide evidence regarding upper arm vein diameters and patient factors that influence vein size. This will enable clinicians to practice from an evidence base to identify the largest vein for PICC insertion to reduce the risk of thrombus.



The aim of this study was to determine the effect of hand dominance, arm side (right versus left), and vein type on vein diameter.




This observational, prospective study was set in a large metropolitan teaching hospital where a nurse-led PICC service operates in the radiology department. Patients who were booked for a PICC or midline catheter insertion were included because vein measurement rather than device type was the focus of the study. PICCs and midline catheters are both inserted peripherally in the basilic, brachial, or cephalic vein approximately 10 cm above the antecubital fossa, but are differing lengths. The tip of the midline catheter sits in the axilla region while the PICC is longer, terminating in the central circulation.1 Midline catheters are inserted predominantly for intravenous (IV) antibiotics for as long as 4 weeks.19



All adult patients 18 years or older who had a PICC or midline catheter inserted between May and December 2013 by the radiology department's lead PICC inserter were approached to participate. Patients were excluded if they were unable to provide informed consent because of neurological or language barriers, if they had factors that prevented the measurement of both arms, or if they reported being ambidextrous.


Power Analysis

A power analysis was conducted using Pass 11 (NCSS). Based on multiple regression with an expected R2 of 0.10 for variability due to hand dominance and R2 of 0.50 for the proportion of variance in arm dominance due to the independent variables of age, gender, arm side, diagnosis type, weight, and height, with 90% power and a .05 significance level, it was determined that 45 participants were required. For multiple linear regression, however, it is recommended that at least 10 subjects be required for each parameter in the model to avoid overfitting. For this reason, we opted for a larger sample of 176 patients.



All measurements were performed by the lead nurse who inserts PICCs and previously had demonstrated the ability to obtain vein diameter measurements reliably and consistently.20 The validity of ultrasound to measure vein diameter had been established previously.21,22 Participants were in a supine position with both arms supported by a platform at a 90-degree angle to the body. The elbow crease of both arms was marked when the arm was bent, and another mark 10 cm proximal from the first was determined using a measuring tape once the arm was straightened. The arms were in a natural state without a tourniquet. A SonoSite S-Series ultrasound with a 13-6 MHz linear probe was used to image the vein. Inbuilt calipers were used to measure the anteroposterior diameter of the vein from the image. This was performed on the basilic, brachial, and cephalic veins in transverse section on both arms. The method has been used to measure vein diameter in previous research and is often used clinically to assess vein diameter for PICC insertion.13,23


The transducer was moved along the second mark until the relevant vein could be visualized and was angled from left to right to obtain the clearest image of the vein. Light transducer pressure was used to reduce vein compression, and gain/depth was optimized for each image. Where 2 brachial veins were present, the larger-diameter vein was measured. Some veins could not be located or could not be measured accurately because of their small size. The superficial nature of the cephalic veins of some participants meant that even minimal transducer pressure caused too much distortion to measure accurately. Further, some could not be compressed because of asymptomatic thrombi. In all of these cases, the individual vein measurements were excluded from analysis.


The nurse who inserted the PICC was blinded to the patient's hand dominance. After vein measurement was completed on both arms, participants were asked to indicate their dominant arm, which was defined as the hand they prefer to write with. Height and weight were obtained from the medical record or the participants themselves.


Data Analysis

Simple frequencies were used to describe demographics and diagnoses of the participants. Univariate and multivariate analysis was conducted using linear mixed effects regression models. Univariate analysis determined the effect of age, gender, weight, height, and diagnosis on mean vein diameter. Multivariate analysis determined the effect of vein type, hand dominance, and arm side on mean vein diameter, which was adjusted for gender, age, height, and weight. Analysis was performed using STATA version 12. The P value was set at < .05.



Approval was granted by the human research ethics committees of the university and the hospital where the study was conducted before the study's commencement (protocol numbers 31301 and 130217, respectively). After the research project was outlined to potential participants they were given a written information sheet by the researcher and allowed time to read it. Written consent was obtained.




Participants were recruited from the waiting area of the radiology department. Of the 296 assessed for eligibility, 59 declined to take part and 61 were excluded. For those excluded, 47 were unable to consent because of confusion, dementia, a low Glasgow Coma Scale score, or the inability to read, write, or understand English; 5 were ambidextrous; and 9 were unable to extend their arms to a 90-degree angle. The veins of 176 participants were measured. The mean age of participants was 58 years (SD 15.62), mean weight was 79 kg (SD 20.86), and mean height was 1.69 m (SD 0.10). Additional information about participants is presented in Table 1.

Table 1 - Click to enlarge in new windowTABLE 1 Participant Demographic Characteristics

A small number of participant veins could not be located or measured at the measurement mark. These included 5 absent basilic veins (5/352; 1.42%) and 8 that could not be measured (8/352; 2.27%). Of the basilic veins that could not be measured, 7 were thrombosed and 1 was scarred. There was 1 absent brachial vein (1/352; 0.28%) and 3 that could not be measured (3/352; 0.85%). Of the brachial veins that could not be measured, 2 were thrombosed and 1 was too small to accurately measure. There were 14 absent cephalic veins (14/352; 3.98%) and 18 that could not be measured (18/352; 5.11%). Of the cephalic veins that could not be measured, 14 were thrombosed and 4 were too small to accurately measure. Vein diameter range was 0.70 to 7.30 mm for the basilic vein, 0.60 to 7.10 mm for the brachial vein, and 0.15 to 6.10 mm for the cephalic vein.


Patient factors and mean vein diameter

Based on univariate analysis, mean vein diameter of the 6 veins combined was greater to a statistically significant degree in male, taller, heavier, and older patients; however, the differences were small for most of these variables (Table 2). The largest difference in vein diameters was observed in male participants who had a mean vein diameter more than half a millimeter larger than females. The diagnoses of participants were not associated with a difference in vein size.

Table 2 - Click to enlarge in new windowTABLE 2 Univariate Analysis of Patient Factors Associated With Vein Size (mm)

Hand dominance and arm side

Of the 3 veins combined, there were no statistically significant differences in mean diameter between the dominant and nondominant arms (Table 3). This did not change markedly after adjustment for age, height, gender, and weight. There was less difference in mean vein diameter when right versus left side was analyzed, which also did not change after adjustment for the same variables.

Table 3 - Click to enlarge in new windowTABLE 3 Association Between Hand Dominance/Arm Side and Mean Vein Diameter (mm)

Vein type

The variables of arm side, hand dominance, diagnosis type, and height were not associated with a difference in the diameter of veins when analyzed by vein type. The effect of other variables differed for each vein type. Male gender (B 0.586; 95% CI, 0.275-0.870; P < .001) and increased weight (B 0.004; 95% CI, 0.001-0.870; P < .001) were associated with increased basilic vein diameter, while age was not. For the brachial vein, male gender (B 0.688; 95% CI, 0.450-0.926; P < .001) and increased age (B 0.183; 95% CI, 0.011-0.026; P < .001) was predictive of larger brachial vein diameter, but increased weight was not. Only increased weight was associated with a difference in cephalic vein diameter, although the actual difference was small (B 0.002; 95% CI, 0.002-0.009; P = .004).


When the mean vein diameters of the different vein types were compared, the diameter of the participants' basilic veins was greater to a statistically significant degree than the diameters of their brachial and cephalic veins. On average, the diameter of the basilic vein was 0.46 mm greater than the brachial vein and 0.89 mm greater than the cephalic vein (Table 4). This difference remained after adjustment for age, gender, weight, and height. Although statistically there were differences between the mean vein diameters according to vein type, the basilic vein did not always have the largest diameter when the location of the largest vein was determined. Notably, when all 6 veins could be measured, the basilic vein was the largest in only 55% of participants, the brachial vein largest in 28%, and the cephalic vein largest in 17%.

Table 4 - Click to enlarge in new windowTABLE 4 Association Between Vein Type and Mean Vein Diameter (mm)


This study found that hand dominance and arm side were not associated with upper arm mean vein diameter. This research is unique in that it specifically examined the upper arm veins used for PICC insertion, but it does support previous research that found that arm side and hand dominance were not correlated with vein diameter.11,14,15


The findings of the present study indicate that either arm could contain the largest vein. For this reason, both arms should be considered for PICC insertion. Yet some authors suggest that left-sided insertion should be avoided because of increased risk of VTE. A higher rate of thrombus was found with left-side insertion in a recent case-control study (n = 400).24 The authors proposed that left-side insertion increases the risk of thrombus because of longer catheter length and, hence, greater thrombogenicity, as well as reduced blood flow of the brachiocephalic vein on that side. But most research has not demonstrated an association between left-side insertion and risk of thrombus.2,3,25,26 Vasculature assessment using ultrasound of both arms should guide insertion-site decisions.


Vein Type

A unique finding of this study was the location of the largest vein. On average, the basilic vein had a greater mean diameter than the brachial and cephalic veins. However, when the largest diameter by vein type was identified, the basilic had the largest diameter in only half the sample. Notably, the cephalic vein was the largest vein in 17% of participants. Previous research suggests that larger catheters are associated with higher rates of deep vein thrombosis.9,16,27 It could be assumed that this is due to increased stasis, hence the need to insert into the largest vein to reduce this risk.28 Clinicians should be cognizant that if they limit vein choice because of ease of insertion or institutional norms, they may not be using the patient's largest vein and may be increasing the risk of VTE. The results of the present study indicate that any of the veins may have the largest diameter. Yet the basilic vein is often preferred for insertion, and the cephalic vein is put forth by some as the "vein of last resort."17 A much-cited study by Allen et al7 supports the avoidance of the cephalic vein for insertion. Participants with a PICC inserted in a cephalic vein were 10 times more likely to develop a thrombus. The authors proposed that higher rates of thrombus associated with cephalic vein insertion were due to smaller vein size; however, they did not measure vein diameter. More recent research has not replicated these findings.24,29


Vein Damage

The veins of some participants in the study could not be measured because of asymptomatic thrombus (noncompressible veins). This was more common in the cephalic veins in which 4% were thrombosed. This is a small but clinically important rate; the damage to these veins meant that they were precluded from PICC insertion. Although not formally recorded in this study, many of the participants who had thrombosed veins stated that they had numerous peripheral intravenous catheters (PIVCs) inserted distally to the measurement point. They had not previously had a PICC or other central access device inserted. For 1 participant, 3 of the 6 veins measured (both cephalic veins and 1 basilic vein) were noncompressible. The participant described multiple hospital admissions, which included numerous surgeries and PIVC insertions. Although the definitive cause of asymptomatic thrombus in this study is unknown, PIVC insertion can lead to thrombotic complications that extend to vasculature in the upper arm. Previous research found that 45% of participants who had not previously had a PICC had asymptomatic superficial thrombosis in veins in the upper arm after PIVC insertion in the forearms.8 However, this study was based on a small sample (n = 29), and a baseline assessment, which would identify preexisting thrombus, was not performed.


The insertion of PIVCs is one of the most common invasive procedures performed in a hospital, yet vasculature assessment is limited to visual assessment and palpation.30 A recent Infusion Nurses Society position paper recommends the use of vein visualization technology, such as ultrasound, to guide difficult PIVC insertion.31 Potentially, ultrasound could be used for all patients to determine vessel health before vascular access device insertion. This would facilitate an individualized and proactive plan of vascular access to protect vessel health.32 This is especially important for those who have chronic health conditions that require repeated vascular access device insertions for infusion therapy.



The study was limited by the inclusion of participants from a single center site; however, it is the major metropolitan trauma and teaching hospital in the region with a wide range of specialties. For this reason, the patient population is likely to be representative of similar hospitals. Any study in which measurement is influenced by the operator clearly has the potential for bias. However, every effort was made to control for this with the use of a consistent approach to measurement.



This study found that hand dominance and arm side were not associated with differences in vein diameter. Patient factors, including age, height, weight, and male gender, are associated with increased vein diameter. The basilic vein tends to have the largest diameter statistically; however, this is not the case in all participants. This research has demonstrated the importance of a full assessment of the basilic, brachial, and cephalic veins of both arms to ensure that the largest and healthiest vein is identified for PICC insertion. Vein measurement using ultrasound should guide practice because each patient's vasculature is unique.



The authors would like to thank the participants who took part in this study, as well as Alicia Turnbull for the support she provided.




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basilic vein; brachial vein; cephalic vein; peripherally inserted central catheter; vein measurement; ultrasound