Target Sign vs Palpation for Radial Arterial Line Placement
Target Sign vs Palpation for Radial Arterial Line Placement
Invasive blood pressure monitoring is achieved by cannulating an artery and transducing the
 pressure. During arterial cannulation the artery can be located by palpation, but use of
 ultrasound has increased the success rate of cannulation. A new ultrasound technique for
 vascular cannulation (dynamic needle tip positioning) has been described. Investigators aim
 to compare this technique to the palpation technique for arterial cannulation. Investigators
 hypothesize that the use of this novel ultrasound technique will result in a higher first
 attempt success rate and overall success compared to palpation.

 Investigators plan to enroll 310 patients in this study. The participants in the study will
 have been deemed by the attending anesthesiologist to require a radial arterial line for the
 operation and thus the research protocol will not involve a deviation from the standard of
 care.
Participants will be brought to the main operating rooms. The patient will not be required to
 do anything different than if they were not enrolled in the study. The anesthesiologist will
 be asked to confirm that the patient still requires an arterial line. The patient will be
 randomized either to palpation or ultrasound group. Patients would be placed in supine
 position on the operating room table and all regular monitors (electrocardiogram, pulse
 oximeter, non-invasive blood pressure) applied. After preoxygenation, the patient would be
 induced and the airway secured. For those requiring an arterial catheter before induction of
 general anesthesia, subcutaneous lidocaine will be used to anesthetize the planned puncture
 site.

 The arms would be abducted and the decision on which side to place the arterial line will be
 determined by the operator after palpation or scanning the wrists with ultrasound. An
 ultrasound image of the radial artery to be cannulated will be obtained. A wrist roll would
 then be placed under the wrist and the hand secured with tape. The wrist would then be
 prepped with chlorhexidine and sterile towels placed around the prepped site. Timing would
 begin once the ultrasound or the operator fingers touch the prepped wrist. For those
 randomized to ultrasound, a Sonosite linear ultrasound probe would then be used to locate the
 radial artery. After satisfactory position is obtained, a 20 ga angiocath 45mm long would be
 used to puncture the artery and then would be advanced until the tip appears on the
 ultrasound view. When this happens the ultrasound is advanced about 2mm proximal along the
 artery. The needle is advanced until the tip is again visualized. This is repeated until the
 needle tip is in the lumen of the radial artery. At this point the needle is sequentially
 advanced in the lumen of the artery in small steps under ultrasound vision and then the
 cannula is advanced over the needle. The needle core is then retracted and the transducer is
 connected to the cannula. If the first attempt is unsuccessful, then more attempts may be
 made until 5 minutes elapse. Success is defined as arterial cannulation as shown by an
 arterial waveform that is obtained within 5 minutes of touching the prepped skin with an
 ultrasound probe or the operator fingers. After that the operator may use the arterial
 cannulation method of choice or decide to change to the other wrist.

 For the palpation method, the radial artery would be palpated and then a 20 ga angiocath used
 to puncture the artery. After a return of blood in the catheter an attempt will be made to
 advance the catheter over the needle core. If this is not successful, the operator can make
 multiple attempts until 5 minutes elapse. After this time, the operator can use any desired
 method to cannulate the artery and may also decide to use the other wrist.

 Investigators will record the successful first pass cannulation, and time to cannulate the
 vessel. Other measures will be number of attempts, number of catheters, radial artery depth,
 radial artery diameter, blood pressure, heart rate, and failure rate. Other data that will be
 recorded will include patient age, gender, weight, height , body mass index, and history of
 peripheral vascular disease, and diabetes.

 Patients will not require any followup for the study.
Inclusion Criteria:

 -  needing radial arterial cannulation intraoperatively

 Exclusion Criteria:

 -  refusal to consent

 -  minors

 -  incarcerated individuals

 -  radial cannulation within past month

 -  negative modified Allen's test

 -  shock

 -  non-English speaking