Which, Tourniquet or Inflation of Blood Pressure Cuff, can Dilate Peripheral Vein Adequately for Intravenous Access?

Methods: This was a prospective non-random trail enrolling fifty healthy volunteers. Ultrasound was used to select an antecubital vein as a target vein. Its’ diameter and cross-section area were measured sonograghically at the same position with different maneuvers, that was baseline, elastic tourniquet and blood pressure cuff with different inflation pressure. The blood pressure cuff was inflated with pressure from 30mmHg to 120mmHg, in 30mmHg increments. Time-intervals between each maneuver were longer enough and basic measurements were repeated to ensure the target vein recover to initial state. At the same time, volunteers’ subjective feeling and degrees of tight under different maneuvers were recorded and evaluated by Visual Analogue Scale. Comparisons among different maneuvers were performed by Repeated Measurement test and Bonferroni test. Non-parametric test Kruskal-Wallis One-Way ANOVA was used to pairwise compare differences of volunteers’ scores of Visual Analogue Scale. The differences of diameter and cross-section area between right and left arm were evaluated by Paired-Sample test.

diameter and cross-section area between right and left arm were not statistically significant (P=0.359 and P=0.404 respectively). The diameter and cross-section area of target veins were correlative to different maneuvers (P=0.000), but not to Right-Left side (P=0.828 and P=0.609 respectively). The venodilation effectiveness of different maneuvers on right and left side was similar to their general effectiveness, which not split by right and left side.
Conclusion: Although elastic tourniquet and blood pressure cuff dilated antecubital veins, blood pressure cuff with 60mmHg inflation pressure was the most effective, followed by 90mmHg inflation pressure. And blood pressure cuff was more comfortable and tolerable than elastic tourniquet when dilating vein for successful peripheral vein access establishment. Venodilation effectiveness of different maneuvers was same on right and left side. Right and left antecubital veins were not obvious different for peripheral intravenous access.

Background
Intravenous access (IVA) is one of the most common clinical procedures in healthcare, particularly for patients in emergency department, operating room, intensive care unit, and so on.
However, establishing IVA is a challenge, particularly in pediatric and geriatric patients with fragile or hidden veins [1]. Difficult IVA results in need for multiple needle insertion. Studies have demonstrated that vein filling or vein size is an important predictor of successful peripheral venipuncture and/or cannulation [2,3], especially in patients with difficult access. Although central venous puncture and cannulation is not bad choice to patients with difficult IVA, this procedure requires staff resources and medical cost, the more important is that central venous catheter is with more complication risks [4,5].
How to make peripheral vein dilation to facilitate IV access?
An elastic tube as tourniquet is the most maneuver, which induces venous stasis for cannulation, such as basilica vein on elbow and saphenous vein on ankle. Although effective, elastic tube might cause discomfort and some complications.
Except elastic tourniquet (ET), most monitors used in clinic provide a function of IVA assistance. With a blood pressure cuff (BPC), an exact pressure is set to prevent peripheral vein collapse during puncture and cannulation. But also, the BPC would be deflated automatically after completing venipuncture. Some studies researched this venodilation effectiveness of ET and BPC, but their conclusions are inconsistent [6,7].
The objective of this study is to assess the effectiveness of venous dilation with different clinical maneuvers commonly available in operating room. Meanwhile ultrasound is utilized to evaluate an appropriate pressure range to increase vein filling.

Methods
This was a prospective non-randomized trial, which was approved by the ethics committee of Sanbo Brain Hospital, Capital Medical University. And all methods were performed in accordance with the relevant guidelines and regulations. Healthy volunteers were enrolled over a 2-month period (March to April 2019). Sanbo Brain Hospital is a tertiary care facility, level one neurosurgery center and academic center for training neurosurgeon nationwide.
All volunteers were required to sign written informed consent.
Lower limb deep vein thrombosis has received more attention in public awareness recently, which has been researched and welldescribed as a common condition. But upper limb thrombosis is a less common phenomenon comparing with lower limb. Risk factors for limb thrombosis include any injury to vein intima, venous stasis, and so on [8]. So in our hospital, upper limb is superior to lower limb for IVA, this was why upper limb was researched in our study. Meanwhile, there are several safe and suitable sites on arm for appropriate venipuncture and cannulation, such as cephalic vein, median cubital vein and basilic vein [9]. The exclusive criteria were as follow: history of upper limb thrombosis, history of upper limb surgery, upper extremity malformation and/or fracture, upper limb infection or venipuncture within three months, any acute medical illness, pregnancy, prior intravenous drug abuse. If these exclusive criteria present in only one upper extremity, the unaffected contralateral one could be still included in this study.
Warmer temperature has been well-known to increase peripheral vein size and improve success of IVA [10]. Then all volunteers were observed in a same temperature-humidity-controlled operating room throughout their exposure to all different maneuvers.
Antecubital vein of each volunteers were identified using a high frequency linear probe (4.0~16.0MHz, 10I2 probe on a SonoScape E3, SonoScape Medical Corporation. Shenzhen, Guangdong Province, China.). Detection depth was set at 2cm. If there were more veins on fossa cubitalia, the largest one was selected. After basic diameter of antecubital veins was obtained, putting the image of target vein on the middle of screen, skin marks were made along the middle of two edges of probe. And upper limbs were kept at the level of heart and same posture during every maneuver. All of these attentions ensured measurements under the same condition.
Antecubital vein measurements of each maneuver included anterior-posterior diameter and cross-section area (CSA), using short-axis image of the target vein ( Figure 1). Because veins might not be standard circular, so both diameter and CSA were together observed to identify changes of the target vein under different maneuvers. Each volunteer's measurement was obtained following procedure: firstly, basic diameter and area were measured, followed by measurements of diameter and area with ET. Next, the second and third volunteers would be measured same parameters.
After that, the three volunteers' diameter and area of the target vein under BPC with 30mmHg inflation pressure were measured one by one. After the maneuver of 30mmHg inflation pressure was finished, the strength would be raised to 120mmHg with 30mmHg increments, and the measurement procedure was repeated one by one. The target vein should return to baseline size between each different maneuver. By this procedure, there was enough time to ensure the target vein returning to primitive level, because inadequate recovery time would produce result bias [11]. Meanwhile basic measurement of target vein was repeated before each maneuver to determine its' restoration. The detail BPC inflation pressure was set by a monitor with a function of auxiliary IVA (Mindray BeneView T8, Shenzhen Mindray Bio-Medical Electronics Co., Ltd. Shenzhen, Guangdong Province, China). BPC was single-use disposable ( Figure 2).  to 60 seconds should be strongly suggested [12][13][14].
During the process, all volunteers were asked to complete a questionnaire, which including 4 questions related to volunteers' subjective feeling with different maneuvers (Table 1). Volunteers' degree of comfort was evaluated with Visual Analogue Scale (VAS) because it was convenient and valuable [15]. Ultrasound equipment operation and sonographic measurement were completed by a senior anesthetist, who received ultrasound training more than two years. A senior nurse did tourniquet strapping throughout whole trail of data acquisition. Using the data obtained above, average vein diameters and areas were calculated.  (Figure 3). CSA: Cross-Section Area. ET: Elastic tourniquet. IP: Inflation pressure. * Compared to baseline, all maneuvers increased diameters and CSAs significantly. # The diameter and CSA of ET were significantly larger than those of BPC with 30mmHg and 120mmHg inflation pressure. However, they were significantly less than those of BPC with 60mmHg and 90mmHg inflation pressure. $ Although there were no significantly different dimeter and CSA between BPC with 30mmHg and 120mmHg inflation pressure, venodilation of them was significantly weaker than that of BPC with 60mmHg and 90mmHg inflation pressure. & The diameter and CSA of BPC with 60mmHg inflation pressure were larger than these of BPC with 90mmHg and 120mmHg inflation pressure, but there was no significant difference of diameters between BPC with 60mmHg and 90mmHg. % The diameter and CSA of BPC with 90mmHg were significantly larger than these of 120mmHg inflation pressure.     CSA: Cross-Section Area. ET: Elastic tourniquet. IP: Inflation pressure. * Compared to baseline, all maneuvers increased diameters and CSAs significantly. # The diameter and CSA of ET were significantly larger than those of BPC with 30mmHg and 120mmHg inflation pressure. However, they were significantly less than those of BPC with 60mmHg and 90mmHg inflation pressure. $ Although there were no significantly different dimeter and CSA between BPC with 30mmHg and 120mmHg inflation pressure, venodilation of them was significantly weaker than that of BPC with 60mmHg and 90mmHg inflation pressure. & The diameter and CSA of BPC with 60mmHg and 90mmHg inflation pressure were larger than these of BPC with 120mmHg inflation pressure CSA: Cross-Section Area. ET: Elastic tourniquet. IP: Inflation pressure. * Compared to baseline, all maneuvers increased diameters and CSAs significantly. # The dianmeter and CSA of ET were significantly less than those of BPC with 60mmHg and 90mmHg inflation pressure. Although CSA of ET was significantly larger then that of BPC with 30mmHg and 120mmHg, the diameter was not significantly statistical different between them. $ Although there were no significantly different diameter and CSA between BPC with 30mmHg and 120mmHg inflation pressure, venodilation of them was significantly weaker than that of BPC with 60mmHg and 90mmHg inflation pressure. & The diameter and CSA of BPC with 60mmHg and 90mmHg inflation pressure were larger than these of BPC with 120mmHg inflation pressure. pressure, although volunteers felt the degree of tight was similar to that of ET, they still considered BPC was more comfortable and tolerable than ET. Actually, that VAS score of BPC lower than ET's also verified BPC was more tolerable than ET.
For ET, the more serious complication is tourniquet retention. A tourniquet may be inadvertently left in limbs for long time after an attempt to IVA. Although serious damage is rare, this might cause infiltration, edema, nerve damage, and so on [16]. We have to pay attention to these complications to avoid adverse events, because they were undoubted to produce additional hospital stay and medical expenses. This could not happen as to BPC because of its automatic deflation.
Given tourniquet material and repeated use in clinical setting, these reusable tourniquets are considered as a source of microbiological contamination. If without adequate reprocessing of sterilization, reuse of tourniquet might jeopardize patients' safety [17].
In 2018 Petersen and colleague reported hygiene of venipuncture tourniquets in Denmark. Their investigation indicated that there was lack of standard procedures or guidelines for handling of venipuncture tourniquets in their nation. Thus, these non-sterile tourniquets used on multiple patients was the potential risk of a nosocomial infection [18]. It is unknown whether there are similar guidelines in our nation, but it does exist in our hospital. However, another problem arises because repeated sterilization discounts ET's effectiveness of venous distension.

Contemporary monitors provide auxiliary function for
venipuncture. With BPC inflation, it is able to attain a detail pressure to make veins more visible or palpable. Furthermore, single-use disposable BPC might avoid transmission of pathogenic bacteria as a kind of medium. But when establishing peripheral IVA or cannualtion, inflated BPC is not used as frequently as ET. The detail reason had not been known, perhaps ET might be easy and convenient. Additional most enrolled volunteers did not learn this function of monitor.
In our study BPC was not only increased venodilation, but also its effectiveness was much stronger than ET's. BPC inflating with 60mmHg inflation pressure could increase target vein diameter 1.15mm (30%) and CSA 8.3mm 2 (57%) from baseline respectively.
When inflating with 90mmHg pressure, its' effectiveness was similar to 60mmHg inflation pressure, especially their diameters were no significant statistical different. These results were consistent with the previous study. Mahler indicated that inflated BPC produced the largest increasement in basilica vein size compared to ET. In their study BPC was inflated with a pressure above volunteer's diastolic pressure [11], however authors did not note the detail diastolic pressure. In our study the mean diastolic  [23]. So, given impacts of a peripheral IVA on patients' clinical outcomes and cost implication, reducing the failed attempts should be of high importance [21]. Actually, many factors affect success rate of first IVA. For instance, previous history of a difficult IVA, clinicians' great confidence and experience, IVA site, and so on [20,[24][25]. However, the palpability and diameter of peripheral vein might be more important than others [3,[24][25]. In the present study, whatever ET or BPC increased diameter of these veins larger than 4mm. If diameter of target vein was larger than 4mm, it would improve first peripheral IVA success rate [3]. Except ET and BPC, local IVA site warming is a safe and effective method for venodilation [10]. All in all, healthcare providers should apply alternative techniques or combine these techniques to improve the first success rate of IVA.

Limitation
Because volunteers enrolled were young and healthy, rather than patients with previous history of difficult IVA, so this conclusion should be discreetly promoted in clinic. If patients after long intensive care unit stay or in end-stage renal disease, the condition of their peripheral veins would be much poor. Planken's study indicated that mean diameter of forearm superficial vein was only 1.8mm in patients of end-stage renal disease [26]. Although these diameters were measured under tourniquet or BPC, they were only half of ours. For these patients, there is needed further study.

Conclusion
Both ET and BPC resulted in a statistically significant increase in antecubital vein size. BPC with 60mmHg inflation pressure produced the largest venodilation, followed by 90mmHg inflation pressure. When BPC inflation pressure was more than 120mmHg, its' effectiveness of venodilation would be discounted. The detail reason of this attenuation should be investigated in future. There was no obvious difference for right and left antecubital veins as IVA site due to their similar size and reaction to BPC. Because BPC was much more comfortable and tolerable, it should be recommended in clinic and combined with other venodilation techniques for more successful IVA.

Volunteer Consent
Written informed consent was obtained from all study volunteers.

Authors' Contribution
JX, HJW and YXS were involved in the study design, statistical analysis and manuscript preparation. PFZ and YMD were involved in the study design and carrying out study measurements. YB and CLJ provided statistical support. FM was involved in manuscript preparation. All authors read and approved the manuscript.