American Journal of Emergency Medicine 36 (2018) 669-672

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Brief Report

The effect of application of a distal tourniquet on ultrasound guided Radial artery cannulation in adult patients

Jun Yao, M.D., Hai Yan, M.D., Zhen Zeng, M.D., Ph.D, Li Wang, Ph.D., Wei Jiang, M.D., Ph.D, Quanhong Zhou, M.D., Ph.D, Jie Lu, M.D. ?

Department of Anesthesiology, Shanghai Jiaotong University Affiliated Shanghai No.6 People’s Hospital, China

Keywords:

Radial artery cannulation Ultrasound guidance Tourniquet

Introduction

Radial artery cannulation is used routinely in clinical settings for many purposes, such as for accurate hemodynamic monitoring, repeat- ed blood sampling and as access for percutaneous coronary intervention (PCI) [1]. Thus it is one of the key techniques for doctors in operating rooms, emergency departments (ED), Intensive Care Units , and cardiovascular divisions. However, the radial artery is small, about 2.4 to 2.6 mm in diameter [2,3] and may be flat, collapsible, calcified, mo- bile, or have other anatomic anomalies, which contribute to difficulty in cannulation. Further, multiple attempts may cause risks and compli- cations such as temporary occlusion of the artery, pseudoaneurysm, in- fection, hematoma and bleeding [4]. Additionally, with a weak pulse or without a palpable pulse, arterial access can be challenging. Therefore, an easily applicable and effective adjunctive technique to facilitate radi- al artery cannulation would be helpful in all these conditions and situations.

In recent years, ultrasound (US) devices for vascular access have emerged and are increasingly popular [5,6]. Many studies have reported that US guidance for radial artery insertion increased success rates and decreased complication incidences [7-9,11,13]. However, some scholars have argued against the positive role of US assistance in radial artery ac- cess [6,10].

We found that a distal tightened tourniquet was reported to facili- tate traditional palpation techniques [3]. In that study, the distal tourni- quet could dilate the proximal radial artery in diameters, thereby increasing first-attempt success rates and shortening the Cannulation time. In the present study, we investigated if distal tightened tourni- quets could similarly provide additional benefit for ultrasound guided radial artery cannulation.

* Corresponding author at: 600 Yishan Road, Shanghai 200233, China.

E-mail address: alex1814@126.com (J. Lu).

Materials and methods

Subjects and study design

This study was approved by the institutional review board (IRB) of Shanghai Jiaotong University-affiliated Shanghai No. 6 People’s Hospi- tal. The IRB waived the need for an additional consent form as the rou- tine anesthesia consent form included an explanation of the benefits and risks of radial artery cannulation. The study was registered with Shanghai No. 6 People’s hospital clinical trial ethical committee (ISRCTN60377452).

Patients who were older than 18 years and who were to undergo elective major surgery that requires continuous blood pressure moni- toring during the operation were eligible for recruitment into the study. Patients with abnormal Allen test, peripheral vascular diseases, and scars at the forearm, i.e. insertion site, were excluded. Enrolled pa- tients were randomly allocated into two groups: group T (with tight- ened distal tourniquet) or group L (with loose distal tourniquet) using the sealed opaque envelope technique.

Study procedure

To avoid unnecessary discomfort for patients, all the radial cannula- tion was performed after induction and tracheal intubation of general anesthesia and before the surgery started. The induction of general an- esthesia included 1% propofol 1.5 mg/kg, fentanyl 3 mcg/kg, vecuronium 0.15 mg/kg. Systolic blood pressure was checked before in- duction as the baseline and right before needle insertion as insertion systolic blood pressure. If the insertion systolic blood pressure was lower than 70% of baseline systolic blood pressure, patients were de- fined as having hypotension at insertion. The frequency of hypotension at insertion was documented. All cannulations were performed by at- tending anesthesiologists who were in charge of the surgeries.

Assistants opened the sealed envelopes (0: tightened tourniquet, 1: loose tourniquet) and placed a tourniquet at distal to the ulnar styloid

https://doi.org/10.1016/j.ajem.2017.12.034

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670 J. Yao et al. / American Journal of Emergency Medicine 36 (2018) 669–672

process tightly or loosely. In the tight group, the tourniquet was tied as tight as possible, as the tightened tourniquet could not be pulled by force away from skin, while in the loose group the tourniquet was loose- ly tied on the far-end of the wrist. The skin at the insertion site was ster- ilized and covered by sheet with a hole. By doing so, the attendings could not see the tourniquet (Fig. 1). Patients were under anesthesia, so they were blind to the tight or loose group allocation, as well.

Ultrasound (S-Nerve; SonoSite, Bothell, WA) guidance was used for all the radial artery cannulation. A high-frequency Linear probe (Sonosite Probe 9L, 6 MHz) capable of imaging and displaying at a depth of 1.5 cm was prepared by assistants. Short axis and out of plane technique were used. The performer used ultrasound probing to search for the optimal site for needle insertion and the needle was inserted at the center of the probe. Standard 20-G i.v. cannular (B. Braun, Germany) was used.

After successful cannulation, the cannula hub was then connected to monitor (CARESCAPE, GE) via a pressure sensor (Combitrans Arterial Monitoring Kit B/BRAUN) and successful cannulation was confirmed by assistants when an arterial wave showed in the monitor. The time from needle insertion (it was announced by the operator) to the suc- cessful wave was defined as radial artery cannulation time. posterior wall technique was allowed in this clinical study at the performer’s dis- cretion. Most procedures were performed by 3 attending anesthesiolo- gists who had at least 20 successful ultrasound guided radial cannulation surgeries.

Endpoints and power

The primary endpoint for the study was to compare the first-attempt success rates between the two groups. Secondary outcomes included the number of attempts, the success rates, and the time used for cannulation.

Once a needle was inserted towards the artery, it was regarded as one attempt that ended with withdrawal of the needle. Short needle ad- justment for ultrasound visualization was excluded. The number of at- tempts was announced by the performer and confirmed by the assistant. If the needle reached the artery with escape of blood, while the cannulation was unsuccessful, the case was regarded as a failure.

The tourniquet and cannula were removed and the insertion site was compressed for at least 2 min to avoid any hematoma. If there was a vi- sual swelling N 2 cm, it was recorded as hematoma. The frequencies of hematoma incidence were counted. The attempt was classified as a fail- ure if the whole procedure took longer than 5 min. After registering the failure, the attending anesthesiologist continued the cannulation in ei- ther the same point or changed to a new site.

Previous studies showed that the first-attempt success rate of US guided radial artery cannulation was about 60%, if there is a 15% in- crease of the success rate, with ? = 0.10 and power = 80%, 118 patients in each group (total 236 cases) were needed to obtain meaningful re- sults?? (https://www.sealedenvelope.com/power/binary-superiority). To compensate for any data losses, we enrolled 240 cases, 120 cases in both groups for the study.

Statistical analysis

Baseline demographic, clinical and procedural characteristics were examined between the two groups. The statistical analysis was conduct- ed under the intention-to-treat principle. All the continuous data were expressed as mean +- SD or median (interquartile, IQR) after normality analysis. Unpaired Student’s t-tests were used for normally distributed continuous variables; otherwise non-parametric Mann-Whitney U tests were used. Proportions were analyzed by Chi-square test or Fisher’s exact test. Subgroup analysis included patients with different genders (male/female), patients who were older or younger than 65 years (elderly/young), and patients who had or did not have hypo- tension at the time of cannulation (hypotension/no hypotension). Two-tailed tests of significance were reported and P value b 0.05 were considered statistically significant. Statistical analyses were performed using a/the SPSS statistical software program (version 20.0.0, SPSS, IBM).

Results

Between June 2014 to August 2015, 240 patients who scheduled for major orthopedic or general surgery were enrolled in the study. The or- thopedic procedures included total hip arthrosplasty revision, pelvic

Fig. 1. The position of tourniquet and radial cannulation. A: The tourniquet was wrapped tightly or loosely at the distal end of wrist for tight tourniquet or loose tourniquet group, respectively. B: Assistants prepare the insertion place using a sterile sheet to cover the tourniquet. The performers could not see whether the tourniquet was tight or loose. Short axis and out of plane technique was used for ultrasound guidance.

J. Yao et al. / American Journal of Emergency Medicine 36 (2018) 669–672 671

Table 1 Demographic of patients in the two groups.					Table 3 first attempt success rates in	sub-group analysis.
	Tight group	Loose group	P			Tight group	Loose group	P
	(n = 120)	(n = 120)			Elderly (n, %)	34, 50.7%	31, 43.7%	0.41
Age (yr) (mean +- SD)	64.0 +- 15.6	66.9 +- 16.6	0.17		Young (n, %)	32, 60.4%	28, 57.1%	0.74
Elderly (>= 65 yrs) (n, %)	67, 55.8%	71, 59.2%	0.60		Male (n, %)	32, 62.7%	24, 52.2%	0.29
Male (n, %)	51, 42.5%	46, 38.3%	0.51		Female (n, %)	34, 49.3%	35, 47.3%	0.81
Height (cm, mean +- SD)	163.6 +- 7.6	164.1 +- 8.2	0.59		Hypotension (n, %)	31, 58.5%	20, 38.5%	0.04
Weight (kg, mean +- SD)	64.7 +- 10.9	62.6 +- 10.8	0.09		No hypotension (n, %)	35, 52.2%	39, 57.4%	0.55
ASA I, II, III (n)	5, 112, 3	5, 113, 2	0.90		Overall (n, %)	66, 55.0%	59, 49.2%	0.37
Surgeries			0.67

cannulation times were statistically shorter in male and hypotensive subgroup patients (Table 5).

Orthopedic surgery (n, %)	82, 68.3%	85, 70.8%
General surgery (n, %)	38, 31.7%	35, 29.2%
Baseline SBP mm Hg (mean +- SD)	147.8 +- 20.5	146.8 +- 21.7	0.71

fracture fixation and spinal surgery, while general surgical procedures included those for gastric cancer, liver cancer and Whipple’s surgery.

There were no significant differences in the demographic of the pa- tients (Table 1). The major comorbidity of the patients included hyper- tension and diabetic mellitus. No significant differences were found in the characteristics of the radial artery cannulation procedure between the two groups (Table 2). There were 5 and 4 cases of hematoma in loose and tight tourniquet group, respectively (P N 0.05). The success rates for the three radial artery cannulation performers were 72.6% (53/73), 75.5% (71/94) and 64.4% (47/73), P = 0.27.

The first-attempt success rate was 55.0% in the tight tourniquet group (n = 66) and 49.2% in loose tourniquet group (n = 59) (P = 0.37), with an overall 5.8% improvement in the tight tourniquet group. multivariable regression revealed significant interactions between tour- niquet group and age and hypotensive group for the first-attempt suc- cess (OR for tourniquet group by hypotensive group = 0.49, 95%CI: 0.26-0.93, P = 0.028) (OR for tourniquet group by age group N 65 years = 0.57, 95%CI: 0.33-0.998, P = 0.049). The first-attempt suc- cess rates for the three radial artery cannulation performers were 53.4% (39/73), 55.3% (52/94) and 46.6% (34/73), P = 0.51.

The overall Cannulation success rates were 76.7% in the tight tourni- quet group (n = 92) and 66.7% in the counterpart loose group (n = 80), P = 0.09. Similar to first attempt success, significant interaction be- tween group and age and hypotensive (OR for tourniquet group by hy- potensive group = 0.408, 95%CI: 0.22-0.78, P = 0.006) (OR for tourniquet group by age group N 65 years) = 0.449, 95%CI: 0.25-0.81, P = 0.008 were found in the multivariable regression after ruling out the collinearity between elderly and hypotensive for the overall success. The differences in the median number of attempts were not signifi- cant between the two groups, 1 (IQR: 1-3) in tight tourniquet group and 2 (IQR: 1-4) in loose group (P = 0.24). The overall cannulation

time was statistically shorter in the tight group (P = 0.01) (Table 2).

Subgroup analysis

hypotensive patients tended to have higher First attempt success rates and Overall success rates in the tight tourniquet group (Tables 3 and 4). Among the 172 patients with successful cannulation, the

Table 2

The procedural characteristics.

Discussion

In this prospective, randomized and double-blinded trial, we tested the hypothesis that a tightened distal tourniquet may facilitate radial ar- tery cannulation under ultrasound guidance by measuring First-attempt success rates, overall success rates, cannulation time and the Attempt times. Although there were no clinically significant differences in all measured outcomes between the two groups, the subgroup analysis suggested hypotensive patients gained benefits from the distal tight tourniquet technique by increased first-attempt success rates, overall success rates and shorter cannulation time in successful cases.

Patient systolic blood pressure was found as one of the factors that associated with failed radial artery cannulation in previous studies [12]. Our previous study showed a tightened distal tourniquet could in- flate the proximal radial artery through expansion of the cross-sectional up-forward diameter and the inner cross-over area [3]. This effect could be more profound in hypotensive patients as the Peripheral vessels might be less well distended due to lower cardiac output and/or less fill- ing of artery vessels following administration of Anesthetic agents as well as a lower mean arterial pressure. When a tight tourniquet was used at the distal end, the blood flow was blocked and relatively more blood accumulated at the proximal end of the vessel. This distending ef- fect may facilitate radial artery cannulation in both palpation [3] and ultrasound-guidance techniques.

The expansion of the cross-sectional diameter and the inner cross- over area from the tightened distal tourniquet could be greater in male patients whose vessels are more elastic and relatively larger than those of females [14]. A slight expansion of an initially large artery may contribute to the shorter successful cannulation time in the male subgroup. In this study, we found a shorter cannulation time in the male subgroup than in the female subgroup, but the benefit is clinically marginal.

Hematoma is one of several complications for radial artery cannula- tion. In the study, there were total 9 cases of hematoma, 5 in the loose group and 4 in the tight group. These results were consistent with pre- vious reports in which the hematoma incidence rate was about 14.4% [1]. All of them happened when the posterior wall technique was used and cannulation failed. Blood was observed to leak-from the posterior wall hole when the needle was withdrawn into the vessel. This result may indicate that the tightened tourniquet did not significantly increase complications in terms of hematoma formation.

Table 4

Overall success rates in subgroups.

Tight group Loose group P

	(n = 120)	(n = 120)				Tight group	Loose group	P
Insertion hypotension (n, %)	53, 44.2%	52, 43.3%	0.90		Elderly (n, %)	50, 74.6%	43, 60.6%	0.08
Posterior wall technique (n, %)	22, 18.3%	15, 12.5%	0.21		Young (n, %)	42, 79.2%	37, 75.5%	0.65
Right radial artery (n, %)	118, 98.3%	120, 100%	0.49		Male (n, %)	38, 74.5%	32, 69.6%	0.59
Cannulation time (s) (median,	40.05,	46.85,	0.01		Female (n, %)	54, 78.3%	48, 64.9%	0.08
IQR)	25.00-65.00	33.00-65.10			Hypotension (n, %)	41, 77.4%	30, 57.7%	0.03
Failure cases n (%)	28, 23.3%	40, 33.3%	0.09		No hypotension (n, %)	51, 76.1%	50, 73.5%	0.73
Hematoma (n, %)	4, 3.3%	5, 4.2%	0.73		Overall (n, %)	92, 76.7%	80, 66.7%	0.09

672 J. Yao et al. / American Journal of Emergency Medicine 36 (2018) 669–672

Table 5

Successful cannulation time in subgroups (s).

	Tight group	Loose group	P
Young	36.43 +- 19.63	41.75 +- 19.46	0.231
Elderly	37.38 +- 17.63	40.57 +- 12.11	0.324
Male	34.51 +- 14.82	41.44 +- 10.82	0.031
Female	38.67 +- 20.62	40.91 +- 18.68	0.569
Hypotension	36.25 +- 18.53	46.12 +- 21.27	0.043
No hypotension	37.51 +- 18.60	38.23 +- 10.95	0.812
Overall	36.95 +- 18.47	41.12 +- 15.89	0.118

Study limitations

This study has several limitations. The first was the power of primary endpoint. The mean difference in first attempt success rate was 5.8 in favor of the tight tourniquet method. This small difference means that the actual Power of the study is 22.8%, so the lack of statistical difference may be a result of low statistical power.

Another issue is related to the subgroup analysis. Although the re- sults showed a positive effect among hypotensive patients, there were relatively few cases in each subgroup. So false positives are difficult to rule out. Thirdly, we did not check the blood velocity in radial arteries, which could be a potential confounder for the results, especially in those patients with diabetes. Finally, all the patients were under general anesthesia with no vessel contraction effect from sympathetic excita- tion. The benefits from distal tighten tourniquet in awake patients may need further study.

Conclusion

Distal tightened tourniquets marginally increased first attempt suc- cess rates, overall success rates and cannulation time in anaesthetized adults undergoing elective surgery. Subgroup analysis identified hypo- tensive patients may benefit from tightened tourniquet technique. Ded- icated future research into the effects of low cost tightened tourniquet for radial artery cannulation in hypotensive patients is required in rela- tion to emergency clinical situations.

Conflict of interest disclosures

No disclosures or conflicts of interest were reported.

Funding/support

No funding or support was received to perform the current study.

Author contributions

Study concept: Yao, Jiang, and Lu

Clinical data collection and radial artery cannulation performers: Yao, Lu, Zeng

Analysis of data: Yao, Zhou, Zeng and Lu Interpretation of data: Yao, Lu, Wang and Zhou Drafting of the manuscript: Yao and Lu

Critical revision of the manuscript for important intellectual content: Yao, Lu, Yan, Zeng, Wang, Jiang, and Zhou

Administrative, technical, or material support: Wang, Jiang, Zeng, Zhou

Supervision: Jiang, Lu

Acknowledgements

Assistance with this study: The authors would like to thank the res- idents who were involved in the operation cases for their assistance, and Mr. Rudolph Weitz for editing.

Financial support and sponsorship: None. Conflicts of interest: None.

Presentation: None.

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