Femoral vein size in newborns and infants: preliminary investigation

Abstract

The femoral vein is an important site for central venous access in newborns and infants. The objectives of this study are to determine whether age or weight can be used clinically to predict the size of the femoral vein in newborns and infants, and to compare the size of the vein in each individual in both the supine and reverse Trendelenburg positions. < 0.01). Weight is predictive of femoral vein diameter in infants, but not in newborns. In infants, weight might serve as a more sensitive index for estimating size of the femoral vein in order to determine accurately the size of intravascular catheter appropriate for cannulation. The diameter of the femoral vein increases in the reverse Trendelenburg position compared with that in the supine position in both newborns and infants. A large prospective study is required to validate these findings.

Background:

The femoral vein is an important site for central venous access in newborns and infants. The objectives of this study are to determine whether age or weight can be used clinically to predict the size of the femoral vein in newborns and infants, and to compare the size of the vein in each individual in both the supine and reverse Trendelenburg positions.

Results:

< 0.01).

Conclusion:

Weight is predictive of femoral vein diameter in infants, but not in newborns. In infants, weight might serve as a more sensitive index for estimating size of the femoral vein in order to determine accurately the size of intravascular catheter appropriate for cannulation. The diameter of the femoral vein increases in the reverse Trendelenburg position compared with that in the supine position in both newborns and infants. A large prospective study is required to validate these findings.

Introduction

] in the literature that have assessed the diameter of the femoral vein. Most of these studies were carried out in older children and adults. The present study is limited to neonates and infants, and the major thrust of the study is to define the relationship, if any, between such readily ascertainable variables as the individual's age, weight and position (supine or reverse Trendelenburg), and femoral vein diameter.

Patients

Twenty-four patients (12 newborns and 12 neonates) admitted to the nursery, pediatric wards, or pediatric intensive care unit, including patients in the pediatric outpatient clinic in our institution, were recruited into the study. All of the patients recruited were euvolemic and had no history of previous attempts at femoral vein cannulation.

The study was approved by the Institutional Review Board of Tulane University, New Orleans, Louisiana, USA. Written informed consent was obtained from the parents or guardian of each study subject.

II ultrasound device

].

Technique

II; Dymax Corp). A 9.0-MHz transducer was placed approximately 1 cm below the inguinal ligament, medial to the pulsation of the femoral artery in each individual. A copious amount of ultrasound gel was applied to the skin at the site corresponding to the femoral vessels and also on the tip of the transducer. By scanning with the transducer medial to the pulse of the femoral artery, the image of both femoral vessels is displayed on the 2-inch square screen. The vein is identified by its position relative to the artery, absence of pulsatility, and demonstration of collapsibility by applying gentle pressure. Once identified, the image was photographed with an instant camera fitted to the ultrasound device. Care was taken to avoid compression of the vein when the photograph was taken by ensuring that copious amounts of gel interfaced the skin and the tip of the transducer, and by avoiding excessive pressure on the transducer. The internal diameter of the vein was measured from the lateral to the medial wall using a calliper. The ultrasound device is calibrated so that the image projected is magnified at the ratio of 2:1. Accuracy of the measurement is in order of 0.5 cm. This technique was used on each individual and repeated in both supine and reverse Trendelenberg positions. The same femoral vein was measured in both positions for each of the individuals studied.

Statistics

< 0.05 was considered statistically significant.

Results

Twenty-four euvolemic individuals were studied, including 12 newborns and 12 infants. The mean age of the newborns was 1.8 ± 0.83 days (range 1-3 days), and there were eight males and two females in the newborn group (male:female ratio 2:1). The mean age of the infants was 7.3 ± 4.60 months (range 3 months-16 months) and there were 11 males and one female in the infant group.

< 0.01).

< 0.01).

) were 0.10 and 0.03 for age and weight, respectively, in the newborns.

Mean femoral vein diameter in the supine versus reverse Trendelenburg positions.

Scatter diagram showing the relationship between femoral vein diameter and weight in the infant group (♦). The line represents the linear regression equation. This line can be used to estimate the diameter of the femoral vein using a subject's weight. R, Pearson's correlation coefficient.

Discussion

]. This increase reached statistical significance, and might have resulted from venous pooling that occurred when central blood flow was restricted by positional dependency.

]. A study to examine the relationship between body surface area and femoral vein diameter in the newborns is warranted.

, Bloomington, In, USA) or the French Catheter Scale. This information together with a normogram of body weight and femoral vein internal diameter will be invaluable information for the selection of intravascular catheters of appropriate size for femoral vein cannulation in infants.

) has potential implications for clinicians attempting to cannulate femoral vein during hypovolemic states. Positioning of patients in a dependent manner increases the diameter of the femoral vein; this maneuver might increase the chance of successful cannulation during clinical hypovolemia. A comparison of femoral vein diameter in supine and reverse Trendelenburg positions between hypovolemic persons and euvolemic control individuals in a larger study with adequate power will be required to validate this theory. The present observation, although statistically significant, may not achieve clinical significance.

].

In conclusion, the internal diameter of the femoral vein in infants can be estimated using weight. Also, the diameter of the femoral vein can be increased above the resting supine diameter when newborns and infants are put in reverse Trendelenburg positions, a technique that might have useful applications in clinical practice.

Keywords

• femoral vein
• infants
• newborns
• reverse Trendelenburg
• ultrasound