Oblique versus longitudinal axis/in-plane approaches for ultrasound-guided radial arterial cannulation: A randomised controlled trial.

Abstract

Editor, There are two approaches to ultrasound-guided radial arterial cannulation for catheter placement: longitudinal axis in-plane (LA-IP) and short axis out-of-plane. The optimal approach remains controversial, and both have disadvantages.1–3 In this study, we introduce a novel approach called the oblique axis/in-plane (OA-IP) approach. Our primary purpose was to compare the first-attempt success rate in the OA-IP approach with that of the LA-IP approach. The secondary aim was to compare cannulation time in the OA-IP approach with that of the LA-IP approach. Ethics approval for this study was provided by the institutional ethics committee of Guangdong Provincial Hospital of Chinese Medicine. This clinical trial was registered online (ChiCTR-IOR-16007748). After obtaining written consent, 60 surgical patients (18 to 70 years, ASA I-III) requiring invasive arterial access were selected. We excluded patients with positive Allen tests, those with BMI more than 40 kg/m2, those undergoing emergency surgery and hand/wrist operation, those in haemorrhagic shock and those with infections at the puncture site. Patients were assigned to either of the OA-IP or LA-IP groups, according to a computer-generated randomisation. We induced anaesthesia with sufentanil, propofol and cisatracurium. After tracheal intubation, a radial arterial catheter was inserted. For radial artery cannulation, the wrist was placed on a support in the dorsal position and the angle of wrist joint extended to 45°. A 20-gauge standard arterial cannula (Becton Dickinson Infusion Therapy Systems Inc, Sandy, Utah, USA) was used for all procedures. Ultrasound images were obtained using a Sonosite M-Turbo Ultrasound System with a 13 to 6-MHz linear transducer (Sonosite INC, Bothel, Washington, USA). Radial artery cannulation was performed by one of two experienced anaesthesiologists: both had placed more than 50 radial arterial lines with in-plane approaches before commencing this study. For the LA-IP approach, the radial artery was visualised as an anechoic tube using the ultrasound probe parallel to the longitudinal axis of the radial artery (Fig. 1a). The arterial catheter was then pushed through the skin proximal to the ultrasonic probe under real-time ultrasound guidance. Once the ultrasound image showed the needle tip inside the artery and blood was seen in the needle, the angle was reduced and the needle advanced 1 to 2 mm. The remainder of the catheter was then advanced into the artery without ultrasound guidance. For the OA-IP approach, after a longitudinal axis view of the radial artery was obtained, the probe was rotated 10 to 15° (clockwise on the right hand, or counter-clockwise on the left hand) to orient the longitudinal axis of the probe obliquely to the artery. The resulting image represented the radial artery as an elliptical anechoic structure (Fig. 2). The arterial catheter was pushed through the skin similar to the LA-IP technique.Fig. 1: The oblique axis in-plane approach. (a) Longitudinal section of the radial artery (white rectangle). (b) Ultrasound probe was placed parallel to the radial artery. The needle was inserted into the skin at the midpoint of the short axis of the ultrasonic probe. (c) Needle (red arrow) inserted into the radial artery.Fig. 2: The oblique axis in-plane approach. (a) Oblique section of the radial artery (blue oval). (b) Probe rotated 15° (curved red arrow) so that the longitudinal axis obliquely crossed the radial artery (black arrow). The needle was inserted into the skin at the midpoint of the short axis of the ultrasonic probe. (c) Needle (red arrow) inserted into the radial artery.The success of catheterisation was confirmed by the arterial pressure waveform displayed on the monitor. The first attempt was defined as follows: from the first skin puncture to successful cannulation, or until the needle removal in a failed attempt. Radial artery diameter and depth of the anterior wall were measured on a captured ultrasound image. We recorded total time (the period from the probe touching the skin to the placement of the catheter into the artery), cannulation time (the period from the skin puncture to the placement of the catheter into the artery), number of attempts, number of puncture sites and any complications. To obtain 80% study power and an α error of 0.05, a sample size of 48 patients was required to detect a 35% difference in the first attempt success rate. When considering the dropout rate (probably 10%), the final sample size of each group was determined to be 30 patients. Radial artery diameter and depth of the anterior wall were similar in both groups. Comparing OA-IP with LA-IP, the first-attempt success rate was higher (93.3 vs. 60%, P = 0.005), whereas the cannulation time (21.90 ± 8.59 vs. 38.23 ± 22.05 s, P = 0.001) and total procedure time (75.5 ± 19.7 vs. 104.8 ± 43.1 s, P = 0.002) were shorter. The number of attempts and numbers of punctures were lower for OA-IP compared with LA-IP. Vasospasm or haematoma was found in five LA-IP patients, and none in OA-IP patients (Table 1).Table 1: Comparison of cannulation efficiency index and characteristics between the groupsWe concluded that, compared with the LA-IP approach group, the OA-IP approach group had a higher first-attempt success rate, shorter cannulation time and fewer injuries. Lamperti et al.4 developed recommendations for ultrasound-guided vascular access and promoted the in-plane technique because of improved precision and fewer complications. Nevertheless, LA-IP was not widely adopted. This may be because maintaining three longitudinal axes (probe, needle and radial artery) in the same plane simultaneously throughout the operation is difficult. Another important reason is the ‘section-thickness artefact’ in a two-dimensional ultrasound system.5,6 Objects (such as needles) out of the scanning plane but within the elevation width of the ultrasonic beam are interpreted as if located in the scanning plane, This may lead to a misconception that the needle is inside the vessel, necessitating multiple needle adjustments, thereby, increasing the risk of vessel injury. OA-IP avoids section-thickness artefact. This means that, when ultrasound images show the needle inside the vessel lumen with OA-IP, it is accurate. We believe that this accounts for the higher success rate of OA-IP in this study. Limitations of this study should be considered. Patients in shock and those with morbid obesity were excluded because it is difficult to perform a radial artery cannulation on such patients. The OA-IP technique is new for us; as an initial step, we wanted to validate the efficiency of this technique among relatively healthy patients. These features suggest that the results of this study may not be applicable to all patients. In conclusion, the OA-IP approach to ultrasound-guided radial artery cannulation may significantly improve first-attempt success rates while also reducing cannulation time compared with those of traditional LA-IP.