Article

Randomized trial of tourniquet vs blood pressure cuff for target vein dilation in ultrasound-guided peripheral intravenous access

a b s t r a c t

Background: Ten percent of the time, peripheral intravenous access (PIV) is not obtained in 2 attempts in the emergency department. Typically, a tourniquet is used to dilate the target vein; but recent research showed that a Blood pressure cuff improves dilation, which may translate to increased PIV success.

Objectives: We sought to determine if there is improved success in obtaining ultrasound-guided PIV using a BP cuff vs a tourniquet in “difficult stick” patients.

Methods: This is a prospective, randomized, single-blinded trial. Adult patients requiring PIV with at least 2 prior failed attempts were enrolled. Patients were assigned to tourniquet or BP cuff for target vein dilation randomly. Nurses prepared the patient for PIV attempt by either placing a BP cuff inflated to 150 mm Hg or placing a tourniquet on the chosen extremity. The extremity was draped to blind the physician to assignment. Physicians then attempted ultrasound-guided PIV. Failures were defined as IVs requiring greater than 3 ultrasound-guided attempts or 30 minutes, or patient intolerance. If failure occurred, the physician was unblinded; and the patient could be crossed over and reattempted.

Results: Thirty-eight patients were enrolled. The success rate for the tourniquet group (n = 17) and BP cuff group (n = 21) was 82.4% and 47.6%, respectively (P = .04). There were no differences between groups for vessel depth, diameter, or procedure time. Six in the BP cuff group were crossed over and had successful PIV obtained with tourniquet.

Conclusions: Tourniquet is superior to BP cuff for target vein dilation in ultrasound-guided PIV.

(C) 2014

1. Introduction

Intravenous access is an essential procedure for emergency department (ED) patients. Prehospital personnel and nursing staff routinely obtain peripheral intravenous access (PIV) for the delivery of intravenous fluids and medications. Up to 10% of the time, PIV access is not obtained in 2 attempts in the ED [1]. If PIV access is not obtained, other delivery methods may be required for medication or fluid therapy, such as via intraosseous lines, Central venous lines, or Endotracheal tubes. These methods are not without complications and are typically not preferred in the ED setting. Many different adjuncts have been used to obtain PIV access in these “difficult stick” patients, including transillumination, infrared devices, and ultrasound. Of these, ultrasound is the most commonly used in the ED [2-4].

Previous studies have demonstrated a 61% to 91% success rate with ultrasound-guided PIV cannulation in “difficult stick” patients (those with 2 unsuccessful PIV attempts) [2,5]. Typically, a tourniquet is used

? The authors have no conflicts of interest to report.

?? Presentations: American Academy of Emergency Medicine, New York, NY, February 2014.

* Corresponding authors. Tel.: +1 610 838 6147.

E-mail addresses: [email protected] (R. Jeanmonod), [email protected] (D. Jeanmonod).

to dilate the target vein; but recent research showed that a blood pressure (BP) cuff improves dilation compared to a tourniquet, which may translate to increased PIV Cannulation success [6]. To our knowledge, there have been no studies examining if this found difference in target vein diameter results in improved success in obtaining ultrasound-guided PIV access.

This study sought to determine if there is a difference between success rates in obtaining ultrasound-guided PIV access using a BP cuff vs a tourniquet in those patients who have failed 2 prior PIV access attempts.

Methods

Study design

This is a prospective, randomized, single-blinded pilot trial.

Study setting and population

The study site is a level 1 community trauma center with an ED census of 60,000. A nonconsecutive, convenience sample of adult (age >=18 years) ED patients requiring PIV access was screened for eligibility over a 1-year period beginning in September 2013. Patients were deemed eligible if the medical provider caring for the patient ordered PIV medications or fluids and the PIV was unable to be placed by experienced

http://dx.doi.org/10.1016/j.ajem.2014.04.020

0735-6757/(C) 2014

762 D. Nelson et al. / American Journal of Emergency Medicine 32 (2014) 761764

ED nursing staff after 2 attempts. Patients triaged to the trauma bay and pediatric patients were excluded. Patients were enrolled after written informed consent was obtained from the patient. The study was approved by the institutional review board at the clinical site.

Study protocol and measurements

Study packets were created using a random number generator to assign patients to tourniquet or BP cuff for target vein dilation for PIV placement. Physicians (both residents and attendings) with prior experience and training in ultrasound-guided PIV access chose the most suitable location for PIV access prior to blinding. Nurses opened the study packets and prepared the patient for PIV access attempt by either placing a BP cuff inflated to 150 mm Hg or placing a tourniquet on the chosen extremity according to packet instructions and then draping the extremity to blind the physician to the patient’s assignment while leaving the access site exposed. Patients undergoing tourniquet attempt had an uninflated BP cuff placed on the extremity in addition to the tourniquet. Patients undergoing BP cuff attempt had an untied tourniquet placed on the extremity. Inflated BP cuffs were clamped with a Kelly to ensure no air leak. Physicians then attempted ultrasound-guided IV placement and recorded success or failure on a standardized data collection form. Failures were defined as those IVs that required greater than 3 ultrasound-guided attempts or 30 minutes of procedure time, or patient intolerance of procedure. If failure occurred, the physician was unblinded; and the patient could be crossed over and reattempted at physician discretion. The primary outcome for our study was success vs failure. Success was defined as Blood drawn from or flush into IV catheter without infiltration. Secondary data points gathered on the data collection sheet included nursing attempts prior to enrollment, number of ultrasound-guided attempts, time to line placement, size of target vessel, and depth of the vessel from skin to anterior wall. Patient demographic information, as well as history of IV drug use, dialysis, chemotherapy, and obesity, was recorded. An area for free-text comments and an area to affix an image of the vessel were also provided on the data collection form. Information provided in the “Comments” section was entirely at the discretion of the physician placing the PIV.

Data analysis

This study was done as a pilot study, as there is a paucity of preliminary data available in the literature from which to do a Power calculation. We sought to enroll 50 patients in this study. Differences in our primary end point were analyzed with Fisher exact test, and the remaining variables were analyzed with descriptive statistics. Free- text areas were explored for themes regarding provider perception of ease of placing the PIV with the 2 methods. Data were analyzed using VassarStats: Website for Statistical Computation (vassarstats.net,

author Richard Lowry, PhD, Professor of Psychology Emeritus, Vassar College, Poughkeepsie, NY, Copyright 1998-2013).

Results

Thirty-eight patients (32% male) with a mean age of 56.3 (SD 17.2) were enrolled (Fig.). Seventeen patients were randomized to receive ultrasound-guided PIV placement with standard tourniquet, and 21 were randomized to receive ultrasound-guided PIV placement with BP cuff. The 2 groups were similar in regard to age, comorbidities, and body mass index (BMI) (Table 1). In categorizing the provider attempting the IV as having done fewer than 5 prior ultrasound- guided IVs, 5 to 10 prior ultrasound-guided IVs, or more than 10 prior ultrasound-guided IVs, there was no difference between the two groups (P = .56). Fifteen different providers placed the IVs.

There was no difference in target vessel diameter or depth between the 2 groups (Table 2). There was no difference in total procedure time (Table 2). The success rate for the tourniquet group (n = 14/17) was 82.4%, and the success rate for the BP cuff group (n = 10/21) was 47.6% (P = .04) (Table 2). In 1 tourniquet success, blood was obtained for laboratory work, the IV subsequently infiltrated, and the provider decided the patient did not require an IV. This was categorized as a success based on our a priori definition. For the 3 tourniquet fails, 2 patients refused further IV attempts, and one underwent central venous access. For the 11 BP cuff fails, 6 were crossed over to tourniquet and were successful, 1 patient refused further IV attempts, 1 had an external jugular IV placed, and 3 had an IV placed by routine methods by another provider.

In the free-text comments, 3 physicians noted that the BP cuff obstructed their ability to perform a PIV proximal enough on the limb to ensure a good site. An additional 3 physicians noted that patients complained of severe pain with BP cuff randomization. One provider noted that it was difficult to distinguish veins from arteries with BP cuff, as the vein was less compressible. Two physicians thought that the BP cuff was responsible for “blowing” the line from increased pressure, and 1 of these providers stated that he aborted the second BP cuff attempt because of difficulty controlling bleeding from the first stick. There were no positive comments listed for BP cuff attempts. There were no comments regarding tourniquet-assisted attempts. Enrollment for the study was stopped early because of provider dissatisfaction with BP cuff-assisted PIV placement as well as concern that patients randomized to BP cuff were having more discomfort and a higher rate of failed attempts as compared to tourniquet attempts.

Discussion

Our results are surprising given what little is known regarding ultrasound-guided PIV placement. A prior study established that

Approached for enrollment n = 41

Refused consent for enrollment n = 3

Randomized to Tourniquet n = 17

Randomized to BP Cuff n = 21

Success n = 14

Failure n = 3

Success n = 10

Failure n = 11

Fig. Consort diagram.

D. Nelson et al. / American Journal of Emergency Medicine 32 (2014) 761764 763

Table 1

Patient demographics

BP cuff (n)

Tourniquet (n)

P value

Diabetes

19% (4)

24% (4)

1

Dialysis

9.5% (2)

5.9% (1)

.58

IVDA

4.8% (1)

11.8% (2)

1

Limb edema

4.8% (1)

0% (0)

.45

Chemotherapy

0% (0)

0% (0)

1

BMI

28.1

28.9

.72

Age

57.6

54.6

.60

vessel diameter is the single most important predictor of success in ultrasound-guided PIVs, with each 1-mm increase in diameter increasing odds of success by 1.79 [7]. This is supported by an additional study in 180 individuals that found that success rates for ultrasound-guided PIV are higher in larger veins [8]. Mahler et al found a 1.6-mm enlargement in target vein diameter with BP cuff compared to tourniquet, which increased to 2 to 3 mm when placed “below the heart,” suggesting that cannulation may be more successful with BP cuff [6]. A British study using Esmarch bandage or commercial exsanguinator also found increased filling in ante- cubital vessels as compared to standard tourniquet [9]. Additionally, there is a theoretical benefit to PIV placement using a BP cuff to dilate the target vein, as the increased pressure should also result in an increase in vessel wall tension (Law of LaPlace), which may reduce the likelihood of failure from piercing through both walls of the vessel due to vessel collapse during venipuncture.

This study examining the difference between tourniquet and BP cuff in ultrasound-guided PIV access in actual patients requiring PIV placement demonstrates superiority of tourniquet over BP cuff using the patient-oriented outcome of successful PIV placement as the primary endpoint. In secondary outcomes such as time to PIV placement and vessel size, there were no differences between the groups.

Anecdotal reports from our physicians participating in this study provide some insight as to why the theoretical benefits of BP cuff- facilitated PIV placement was not borne out in practice. Firstly, the BP cuff is large and cumbersome. The inflated BP cuff obstructs the majority of the upper arm, limiting the potential for accessing the basilic and brachial veins. This was listed as the primary reason for failure in 14% (3/21) of BP cuff attempts, and all three were subsequently successfully cannulated when crossed over to tourniquet. Secondly, the inflated BP cuff creates a greater pressure on the arm than the tourniquet. Though this is likely the reason for increased target vein diameter in other studies, it causes increase in pain to patients. Most patients reported pain with the BP cuff inflation (prior to PIV attempts), with 2 patient refusing attempts entirely. One of these patients was crossed over to tourniquet and successfully cannulated, and the other declined any further PIV attempt. For the BP cuff attempts that infiltrated or were “blown,” 2 providers felt that back pressure on catheter insertion was responsible for PIV failure. Certainly, the increased pressure from the inflated BP cuff is the reason that 1 provider felt it was difficult to distinguish veins from

arteries on ultrasonography.

There was no significant difference in the 6 demographic characteristics recorded (BMI, diabetes, dialysis, intravenous drug use, chemotherapy, upper extremity edema). These characteristics have been shown in previous studies to be underlying etiologies for

Table 2

Compared PIV techniques

BP cuff

Tourniquet

P value

Vessel depth in cm, mean (SD)

0.59 (0.27)

0.79 (0.35)

.10

Vessel diameter in cm, mean (SD)

0.37 (0.12)

0.36 (0.19)

.80

Procedure time in min, mean (SD)

8.7 (10.5)

10.6 (8.3)

.55

Percent success (n)

47.6 (10)

82.4 (14)

.04

difficulty with PIV access. There has been conflicting research regarding whether obesity and BMI play a role in the ability to obtain PIV access. Juvin et al [10] demonstrated that obesity is related to increased difficulty in obtaining PIV access, whereas Lopostolle et al

[1] did not find this relationship. The mean BMI in our study was 29.6, suggesting an overweight but not necessarily obese population. There was no statistically significant difference in the mean BMI when comparing success vs failure groups.

Limitations

There are a limited number of patients enrolled in this study, and our study closed enrollment early because of patient discomfort and provider dissatisfaction. No statistical significance could be found between time of procedure, procedure attempts, vessel diameter, or depth. These end points, however, are not as clinically important as PIV access success. We did see improvement in success using tourni- quets over BP cuffs.

Although all providers who participated in this study have been trained in and are comfortable with ultrasound-guided PIV place- ment, it is possible that the use of the BP cuff may have caused operational difficulties even with experienced providers that might improve with further practice. We did not ascertain whether providers placing ultrasound-guided IV lines had prior experience using BP cuff for target vein dilation.

Although every attempt was made to preserve blinding, it is possible that some operators may have predicted randomization based on patient complaint of pain or other factors, such as decreased compressibility of veins. We did not assess the success of our blinding. There was no control for the specific target vein used, such as the basilic or brachial. This heterogeneity may limit the analysis of secondary end points such as target vein diameter and depth. We felt that limiting physicians to a specific vein may make the study less applicable, may increase cannulation failures, and may increase

patient discomfort (particularly with basilic vein).

The perceived complications of patient discomfort and IV infiltration seen in the group randomized to the BP cuff could be due to the increased intravascular pressure imparted by the BP cuff. No study has determined if there is an optimal insufflation pressure to optimize venous distension while minimizing complications. Our target insufflation pressure of 150 mm Hg was adopted from a previous study [11], whereas the study by Mahler et al [6] used a pressure “above diastolic pressure.” It could be that the optimal pressure is lower than what we applied.

Finally, this study was performed at a single institution and may not be generalizeable to other institutions.

Conclusions

Target vein dilation with tourniquet to facilitate ultrasound- guided PIV placement offers a clear advantage over BP cuff use.

References

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  7. Witting MD, Schenkel SM, Lawner BJ, Euerle BD. Effects of vein width and depth on ultrasound-guided peripheral intravenous success rates. J Emerg Med 2010;39:70-5.
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