 Intraarterial vasodilators reduce radial artery spasm. Use of transdermal vasodilators such as nitroglycerine to dilate radial artery prior to vascular access would increase chance for successful arterial access in first attempt and increase radial artery to sheath size ratio both of which should have additive benefit to intraarterial vasodilators in reducing radial artery spasm. Transdermal lidocaine would reduce pain during subcutaneous infiltration of lidocaine, which can further ameliorate the risk of radial artery spasm. Use of transdermal nitroglycerine for this purpose has been shown to safely increase radial artery dimension without any significant effect on blood pressure. 