Comparison of Ultrasound-guided Versus Blind Insertion of Radial Artery Catheters

The study will be conducted in a prospective randomized design on the patient population of the Surgical Intensive Care Unit (SICU) at Yale New Haven Hospital. All SICU patients in whom the indication for arterial catheterization has been established by the attending physician will be eligible for consented randomization to either the "Palpation" or the "Ultrasound" group.

Once consent from the patient or his/her surrogate has been obtained, eligible patients will be randomized to either the "Palpation" or the "Ultrasound" group. Sequentially numbered sealed envelopes will be maintained in the SICU.

Catheter insertion: The side of insertion (left/right arm) is chosen by the operator. The wrist is positioned by the operator, the skin disinfected and the area draped in a sterile fashion. "Palpation" group": The artery is punctured after location by palpation only. "Ultrasound" group": The artery is punctured under real-time ultrasound only with the probe draped in a sterile sheath. The time from the first skin puncture to confirmed intra-arterial position of the catheter by observing blood return from the catheter is measured with a chronometer by a second person. An arterial pressure waveform must be observed on the monitor to validate intra-arterial catheter placement.

Radial artery cannulation will be performed using the "Radial Artery Catheterization Set with Integral Needle Protection" (Ref. RA-04020-SP, Arrows International Inc., Reading PA 19605, USA) containing a 20G catheter on a 22 gauge (22G) puncture needle and a 0.46 mm spring-wire guide.

For ultrasound-guided catheter insertion, operators will use the "Site-Rite 6 Ultrasound System" with a linear vascular access probe (5-10 MHz) (Bard Access Systems Inc., 605 North 5600 West, Salt Lake City, UT 84116, USA).

Operators: RA catheterization is a typical teaching procedure frequently performed in the ICU. In our unit, arterial lines are placed by either post graduate year 2 (PGY-2) residents (surgery \& anesthesia) rotating through the SICU on a monthly basis, or by mid-level providers who are in the unit for indeterminate periods of time. For our study, this will be an important point, as one of our goals will be to demonstrate a learning effect, which is less likely to be observable among the PGY-2 residents who will be present in the unit for a month only.

All operators will get instructions (lecture and hands-on training on vascular phantom at the beginning of their SICU rotation) on the use of ultrasound for vascular access and will at all times have the opportunity to exercise their skills on a vessel phantom. Each successful vessel puncture on the vessel phantom must be recorded by the operator, including time and date. For each operator performing the ultrasound-guided insertion on a patient, one of the investigators will be present for supervision and data collection, but not for assistance with insertion, unless required for failure after having used both methods.

Cross-over: After three failed attempts at catheterization with the allocated first method, the alternative method must be used; the operator can opt to puncture the RA on the opposite arm. Timing of the first method ends when the operator decides to abandon the third attempt. Timing for the new method starts at the new first skin puncture.

Follow up: All catheters will be monitored daily and on days 1 and 3 with clinical and ultrasound examination for the development of complications. The catheter will be followed daily for functional outcomes defined as the quality of the arterial waveform on the monitor and the ability to draw blood from the catheter. The day on which the catheter ceases to function for each of these purposes will be recorded as well as the day of catheter removal.