Cardiac/Hemodynamics/MonitoringTopical nitroglycerin and lidocaine locally vasodilate the radial artery without affecting systemic blood pressure: A dose-finding phase I study
Introduction
Radial artery cannulation is a commonly performed procedure in the emergency department, intensive care unit, and the operative suite for analysis of arterial blood gases, for invasive monitoring of blood pressure, and as continuous access for frequent blood sampling. In addition, radial artery cannulation for diagnostic coronary angiography and percutaneous intervention (PCI) is rapidly growing in use, with approximately 1.3% of PCIs performed via this technique in the Unites States [1].
In clinical practice, small artery size is a common cause of failure to cannulate the radial artery; and multiple attempts at cannulation can result in hemorrhage, radial artery dissection, vasospasm, pseudoaneurysm formation, pain, and thrombosis of the vessel [2], [3], [4]. Techniques for improving radial artery cannulation have included performing the modified Allen test and/or Barbeau test to assess for patency of the vessel [5], direct visualization of the vessel with ultrasonography at the time of cannulation, and use of a wire-guided cannula [6], [7], [8].
For radial artery catheterization during coronary angiography, the vasodilator nitroglycerin (NTG) has been shown to be effective in treating radial artery spasm when administered from within the artery [9]. Others have used subcutaneously injected NTG to effectively prevent radial artery spasm after it has occurred [10]. Subcutaneous injections of lidocaine combined with dinitrate isosorbide have been shown to improve success rates of radial artery cannulation [11]. The use of transdermal NTG before cannulation has also been described [12]; however, the effectiveness of this technique has not to our knowledge been evaluated. Whether NTG delivered as a transdermal application can increase radial artery diameter (RAD) and prevent spasm before cannulation and whether combining NTG with lidocaine will attenuate this affect are unknown.
Accordingly, we designed the current study to test the hypothesis that topical NTG will act directly and locally on the radial artery to produce vasodilation and that a mixture of topical lidocaine and NTG will lead to significant dilation of the radial artery as compared with topical lidocaine alone.
Section snippets
Study design and participants
The study was a single-center, randomized, double-blind, placebo-controlled, dose-finding, phase 1 study. The University of California, San Francisco, institutional review board approved the study; and all participants provided written informed consent.
Healthy subjects older than 18 years were recruited. Exclusion criteria include the presence of liver, cardiovascular, rheumatologic, or renal disease; current treatment with any vasodilator therapy; a systolic blood pressure of less than 90 mm
Results
A total of 19 subjects were enrolled in the study for a total of 38 radial arteries studied in each study visit. Sixty-eight percent (n = 13) were women, and the mean age was 29 years. Average body mass index was 24.5. Five percent of study subjects (n = 1) were active smokers, and 3 subjects were taking oral contraceptive medications.
Visit 1 was designed to find the appropriate dose of NTG (Fig. 1); the results are given in Table 1. Both the 15- and 30-mg NTG doses resulted in significant
Discussion
Topical NTG produces a statistically and clinically significant increase in RAD that begins as early as 30 minutes, with the effect maintained over 2 hours. Lidocaine, in contrast, did not affect radial artery vasodilation. Importantly, there was no evidence of an effect with NTG on the contralateral radial artery nor was there a significant effect on blood pressure, which may make topical NTG a treatment option in critically ill patients for whom radial artery cannulation is frequently
Conclusion
Topical NTG and lidocaine significantly increase RAD within 30 to 60 minutes with no effect on the contralateral radial artery or blood pressure.
Acknowledgments for research support
UCSF Academic Senate Grant awarded to Dr Andrew Boyle.
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