Correlation of VeinViewer and Ultrasound for Peripheral Vein Width

Transcription

1 Correlation of VeinViewer and Ultrasound for Peripheral Vein Width by Christina M. Bahls, SRNA Tanya M. Dierksheide, SRNA Jacob R. Heesch, SRNA Mary E. Shirk Marienau, CRNA, MS Gregory J. Schears, MD Approved: Research Advisor/Date Program Director/Date

2 Correlation of VeinViewer and Ultrasound for Peripheral Vein Width Christina M. Bahls, SRNA* Tanya M. Dierksheide, SRNA* Jacob R. Heesch, SRNA* Darrell Tanya Mary E. Shirk Marienau, CRNA, MS# Gregory J. Schears, M.D.+ *Graduate Participant, Mayo Clinic College of Medicine, School of Health Science, Master of Nurse Anesthesia Program, Mayo Clinic, Rochester, Mayo Medical Center, Rochester, MN +Consultant in Anesthesiology, Mayo Clinic, Associate Professor of Anesthesiology, Mayo Medical School, Rochester, MN #Director, Mayo Clinic College of Medicine, School of Health Science, Master of Nurse Anesthesia Program, Assistant Professor of Anesthesiology, Mayo Medical School, Rochester, MN Mary E. Shirk Marienau, CRNA, MS Mayo Clinic sievens Building st Street SW Rochester, MN marienau.mary@mayo.edu Gregory J. Schears, MD Dept. of Anesthesiology and CCM MB First St. SW Rochester, MN 55905

3 Key words: Peripheral venous access, Near infrared, VeinViewer imaging, Ultrasound imaging

4 Abstract: Correlation of VeinViewer and Ultrasound for Peripheral Vein Width Background and Significance: A new noninvasive vein imaging device using near infrared light has been found useful in gaining peripheral intravenous access. The VeinViewer device created by Luminetx Corp. uses near infrared light which penetrates skin and subcutaneous fat without causing damage to these tissues. This infrared imaging device projects an enhanced image of subcutaneous veins back onto a subject s skin. Little research has been done correlating the accuracy of the VeinViewer image with images of veins from ultrasound. This study aims to provide an accurate correlation of width of subcutaneous vessels between the VeinViewer near infrared device and ultrasound imaging. Hypothesis: Measurement of peripheral vein widths with the Luminetx VeinViewer will agree with width measurements taken of the same vein with two-dimensional ultrasound in healthy human subjects. Specific Aims: Primary aims were to correlate projected VeinViewer venous image size with the ultrasound image, assess for differences in correlation based on anatomical site and width, and assess for differences in correlation based on depth. Methods: Using the VeinViewer device, three measurements of vessel width of one vein in the dorsum of the hand were recorded on 100 healthy subjects and the average measurement was used for statistical analysis. This process was repeated for the wrist and ventral forearm. Images of these same areas were also obtained using the Sonosite Micromaxx Ultrasound device immediately after they are obtained using the VeinViewer device. Measurements were made of the vessel width and depth at the marked point. The agreement of the measurements obtained via ultrasounds and VeinViewer was evaluated using Pearson Product Moment correlation and also using the methods of Bland and Altman. Results: A total of 100 (29 male, 71 female) subjects were studied. The mean ± SD age was 32 ± 10 years (range 18 to 62 years). The ultrasound and VeinViewer results were significantly correlated at all locations with the magnitude of the association strongest at the dorsum and weakest at the forearm (dorsum r=0.64, wrist r=0.57, forearm r=0.42; all p<0.001). There was no significant bias for measurements in the hand. For the wrist and forearm, there was evidence of a significant bias (both p<0.001) with the VeinViewer image being larger than the measured ultrasound width (mean ± SD difference between methods of 0.03 ± 0.06 cm for wrist, 0.04±0.08 cm for forearm). Vein depth did not appear to affect this correlation. Conclusions: The overall correlation of the VeinViewer device with ultrasound was good. From Bland-Altman plots, the variability in agreement between methods was dependent on the width of the vein with better agreement at smaller widths. For veins less than 0.23 cm it tended to display an image of the vein that was larger than the actual size. Veins larger than 0.23 cm tended to be projected equal or slightly smaller than the ultrasound measured size. Clinicians need to take this into account when using this device to make sure they do not try to access a vein too small to accept the chosen catheter size. Key words: Peripheral venous access, Near infrared, VeinViewer imaging, Ultrasound imaging

5 Introduction Peripheral venous access can be difficult to obtain in patients whose veins are not visible or palpable after an appropriate application of a tourniquet. This especially occurs in the very young (less than 7 years of age and especially less than 3 years), the obese, darkly pigmented, and those who have frequent intravenous access attempts due to chronic illness or prolonged hospitalization 1. Therefore techniques to improve the visualization of subcutaneous veins will have important implications for improving the care provided and reducing needle sticks. Several techniques exist to assist in visualization of subcutaneous veins. Transillumination, ultrasound, and near infrared imaging have all been used to visualize subcutaneous structures. The use of these alternative devices may lead to less time spent attempting intravenous access, fewer attempts, and greater patient satisfaction. 2 Transillumination is a technique that has been utilized in the pediatric population since the 1970s for visualization of difficult veins. There are several methods involving transillumination, including fiberoptic light sources and red light emitting diode (LED) sources. Unfortunately, there are some disadvantages to these light sources. The fiberoptic light source tends to be expensive, can be bulky and difficult to transport from bedside to bedside, and requires an AC power source 3. Typically, its use is limited to the smaller pediatric patients in their hands and feet. While the red LED source is more portable and cost efficient, its use is limited by its ability to penetrate through thicker body structures and darker skin pigments. Ultrasound guidance can also be used for establishing venous access in a subcutaneous vein that is invisible to the naked eye. The use of ultrasound for guidance of intravenous catheter placement results in a decreased number of percutaneous punctures, decreased time necessary for the successful cannulation, and increased patient satisfaction with the procedure. 2 A major limitation to ultrasound guidance for obtaining venous access is the expertise and training needed to operate the ultrasound machine and the ability to interpret the resulting ultrasound image while simultaneously cannulating the vein. 1 The veins must also be relatively large in order for the ultrasound machine to be useful for most clinicians. An additional limitation is that ultrasound machines are not readily available at all institutions. A new noninvasive vein imaging device using near infrared light has been found useful in gaining peripheral intravenous access. The VeinViewer device created by Luminetx Corp. uses near infrared light to penetrate the skin and subcutaneous fat without causing damage to these tissues. 4 The camera with IR filter and computer distinguishes areas of near infrared desaturated hemoglobin absorption by near infrared light from remaing tissue. The device then projects an enhanced image of subcutaneous veins back onto a subject s skin. The image reproduces blood in the veins as a dark image and skin/fat as lighter images. 4 For veins invisible to the eye, the device allows the clinician a direct, hands free means of achieving venous access. For those veins partially or completely seen, it provides increased contrast and topography which could help improve venous access success rate and reduce errors. Little research has been done correlating the accuracy of the VeinViewer image with images of veins from ultrasound. The study aim was to correlate projected VeinViewer size with ultrasound image, assess for differences in correlation based on anatomical site and width, and assess for differences in correlation based on depth. Our hypothesis was that the measurement of peripheral vein widths with the Luminetx VeinViewer will agree with width measurements taken of the same vein with two-dimensional ultrasound in healthy human subjects.

6 Methods: This was a prospective, convenience sample study. After Anesthesia Research Committee and IRB approval, 100 adult subjects between ages with no health problems were enrolled in the study and measurements of veins in the dorsum of the hand, wrist, and forearm were taken. Participants were recruited by mass sent to the Mayo School of Health Sciences and posted signs. Participants must be of ASA Class I status. According to the American Society of Anesthesiologists Physical Status Classification System, ASA Class I includes normal, healthy patients without systemic disease 5. Additional exclusion criteria included recent or current steroid treatment, recent or current intravenous antibiotic treatment, recent blood draws, recent intravenous access, and BMI greater than 35 kg/m 2. Recent was defined as within the past 6 months. Demographic information such as date of measurement, age, gender, height, weight, BMI, and skin pigmentation were recorded. Skin pigmentation was assessed using the Fitzpatrick Skin Pigmentation Score and recorded on the data collection tool (appendix). The participant placed his or her dominant upper extremity on the viewing platform to ensure consistent measurements. We used a ball point pen to mark the area of interest to be measured. The quality of vein was assessed using the Vein Quality Assessment Scale (appendix). A digital caliper with an accuracy of millimeters was used to measure the width of the vein projected on the skin. Using the VeinViewer device, three measurements of vessel width of one vein in the dorsum of the hand was recorded and the average measurement was used for statistical analysis. This process was repeated for the wrist and ventral forearm. All measurements were taken using the Fine Detail setting on the VeinViewer device. Images of these same areas were obtained using the Sonosite Micromaxx Ultrasound device with the L-25 transducer immediately after they were obtained using the VeinViewer device. Measurements were made of the vessel width and depth at the marked point. The measurement of the ultrasound tool is accurate to within 2% of the measurement made 6. All measurements made were recorded on data collection tool (appendix). The investigator taking measurements was blinded to the values obtained. A second investigator recorded all data on the collection forms. Study data were managed using REDCap electronic data capture tools hosted at a midwestern teaching institution. Data were analyzed using two different statistical approaches: Bland and Altman 7 and Pearson's product-moment coefficient 8. Separate analyses were performed for each site. Exploratory analyses were performed using linear regression methods to assess whether the agreement between methods was dependent on vessel depth. For this exploratory analysis the difference between width measurements (VeinViewer - Micromaxx Ultrasound) was the response variable and vessel depth was the potential exploratory variable. In all cases, two-tailed p-values were reported and findings were summarized using point-estimates and corresponding 95% confidence intervals. A repeated measures analysis was performed using a mixed linear model (SAS PROC MIXED) to assess whether the difference between VeinViewer and ultrasound measurements was significantly associated with vessel width (average of US and VV measurements), vessel depth, or anatomic site.

7 Results The mean ± SD age was 32 ± 10 years (range 18 to 62 years). The ultrasound and VeinViewer results were significantly correlated at all locations (dorsum r=0.64, wrist r=0.57, forearm r=0.42; all p<0.001). However, for all sites the observed association did not follow the line of identity (Graph 1, left panels). If the ultrasound measurement is assumed to represent the true width of the vessel, then the VeinViewer tends to overestimate the width of small vessels and underestimate the width of large vessels (Graph 1, left panels). For the wrist and forearm, there was overall evidence of a significant bias (both p<0.001) with the VeinViewer image being larger than the measured ultrasound width (Graph 1, right panels; Table 1). From repeated measures analysis the difference between VeinViewer and Ultrasound measurements were found to be significantly associated with both anatomic site (p=0.001) and vessel width (p=0.002), but not vessel depth. These results indicate that VeinViewer measurements of vessel width are larger than ultrasound measurements for small vessels and smaller than ultrasound measurements for large vessels. Discussion In general, ultrasound is utilized as the gold standard for measuring vein size. Overall, the images taken in this study with the VeinViewer device correlated with the images that were obtained with ultrasound. Depth did not appear to be a major factor in this study and did not appear to affect the difference in measurements. This study found that the difference in vessel width measurement between the VeinViewer device and ultrasound is dependent on the width of the vessel. For example, a larger vessel will tend to produce a slightly smaller image using the VeinViewer device. This study found that for vessels that were smaller than 0.23 cm, the VeinViewer device tended to overestimate the size of the vein. For veins that were larger than 0.23 cm, the VeinViewer tended to underestimate the size of the vessel. Regardless of which method was utilized to analyze the data, the clinician should be aware that the image projected on the skin may not be a true reflection of the vessel. While this device may be helpful to identify the location of the vessel, care should be taken not to overestimate or underestimate the size of the actual vessel. This study is valuable to the clinician because it will help the clinician to interpret VeinViewer images, keeping in mind that the exact vessel size may be slightly larger or smaller than what is projected by the VeinVeiwer image. Knowing this information, the clinician should be better able to select appropriate sized intravenous catheters and better judge vessel size with the VeinViewer device prior to obtaining intravenous access. Armed with this information, clinicians will potentially reduce the number of intravenous sticks in patient populations who historically have been difficult to obtain intravenous access. There were some limitations associated with this study. Ultrasound was assumed to represent the true value of vein width. The measurement of the ultrasound tool is accurate to within 2% of the measurement made 6. While ultrasound is currently the industry s gold standard for vessel width and depth determination, the overall accuracy of this device is not completely known. In addition, vessel width is constantly changing. The utilization of room temperature ultrasound gel and other internal (excitement, embarrassment, joy) or external environmental factors (temperature) may have also introduced variability in the vessel size during the measurement process. A third limitation to consider for this study is that the VeinViewer images were at times subject to interpretation due to some images of vein edges that were less

8 well defined than others. This problem may have introduced some error during interpretation of the vein edges while using the digital microcalipers. A final limitation to consider is the variability that could have occurred between data collectors while measuring the vein widths with the digital microcalipers. Obtaining peripheral venous access can be difficult in certain patient populations and is becoming increasingly more common as obesity is on the rise. Patients who are extremely young, obese, darkly pigmented, or those who have chronic illnesses are individuals who are frequently challenging to attain peripheral intravenous access. In recent years devices such as transillumination, ultrasound, and near infrared imaging have been useful in helping to attain access in these patients. With the use of such devices, less time may be spent attempting IV access and fewer attempts may be made, potentially leading to greater patient satisfaction and decreased costs. The device utilized in this study provides several potential advantages to the clinician. The projected image allows a hands free approach to venous access. This will allow the clinician to use the same technique that would be used with visible veins. The projected image may also help improve the sterility of the access site because of a reduced need to touch the site to identify the vein s location. The clear projection of the venous topography may allow better insertion site choice which might help reduce phlebitis and prolong dwell time. Ultimately, the device could also be used to do a pre-assessment of the patient s venous targets and prospectively provide a venous access management plan from the beginning of their entry into the medical system instead of waiting until the options are limited. The ability to see the veins refill may help with judging vein quality and flow which could help reduce thrombosis and choose an optimal catheter size. Extravasations may be able to be picked up earlier as blood outside the vessel is readily recognized. All of these potential advantages will require additional investigation to prove their merit. In summary, the Vein Viewer had good correlation with ultrasound overall. For veins less than 0.23 cm, the veins tended to be projected larger than measured by ultrasound. For veins greater than 0.23 cm the vein tended to be projected at equal to slightly smaller than the ultrasound measured value. The clinician using the device must be made aware of this phenomenon to properly interpret what they are seeing and make optimal use of the image. Future generations of this device will hopefully take advantage of this information provided by this study and adjust the computer projection algorithm to closer match the actual vein size.

9 Graph 1: Pearson Correlation and Bland-Altman Agreement Plots

10 Graph 1 Legend: On the left are the ultrasound measurements of width versus the corresponding VeinViewer measurement with the line of equality included as a reference. On the right are Bland-Altman plots of the difference between measurements (VeinViewer minus ultrasound) versus the mean of the two measurements with reference lines for the mean difference and 95% limits of agreement.

11 Table 1: Vessel Widths (cm) obtained with VeinViewer and Ultrasound (N=100) * Device Dorsum Wrist Forearm VeinViewer 0.22± ± ±0.07 Ultrasound 0.21± ± ±0.07 Delta (VV US) 0.01± ± ±0.08 Paired t-test p=0.232 p<0.001 p<0.001

12 Table 1 Legend: *Data are presented as mean ± SD.

13 References 1 Zharov, V.P., Ferguson, S., Eidt, J.F., Howard, P.C., Fink, L.M., Waner, M. (2004). Infrared imaging of subcutaneous veins. Lasers in Surgery and Medicine, 34, Costantino, T.G., MD, Parikh, A.K., MD, et al. (2005). Ultrasonography-guided peripheral intravenous access versus traditional approaches in patients with difficult intravenous access. Annals of Emergency Medicine, 46(5), John, J.M. (2007). Transillumination for vascular access: old concept, new technology. Pediatric Anesthesia, 17 (2), Miyake, R.K., Zeman, H.D., Duarte, F.H., Kikuchi, R., Ramacciotti, E., Lovhoiden, G., Vrancken, C. (2006). Vein imaging: A new method of near infrared imaging, where a processed image is projected onto the skin for the enhancement of vein treatment. Dermatologic Surgery, 32, American Society of Anesthesiologists. (2008). ASA Physical Status Classification System. Retrieved April 20, 2008 from 6 Micromaxx. (2005). Micromaxx Ultrasound Service Manual. Retrieved November 3, 2008 from 7 Bland JM, Altman DG. (1986). Statistical methods for assessing agreement between two methods of clinical measurement. Lancet, Kleinbaum, D.G., Kupper, L.L., Muller, K.E. Nizam, A. (1998). Applied regression analysis and other multivariable methods. (3 rd.ed.) Duxbury Press: Pacific Grove,