INTRODUCTION

Central venous cannulation is a widely used technique for critically ill patients and those undergoing major surgery. It is performed for hemodynamic monitoring, infusion of vasoactive drugs, rapid fluid resuscitation, or urgent blood replacement therapy. The primary access routes for this purpose are through the internal jugular vein and subclavian vein. The subclavian vein is often used for ultrasound-guided central vein cannulation in operating rooms and intensive care units, serving as an alternative site to the internal jugular vein. This site offers several advantages, including a lower incidence of thrombosis and central venous catheter related sepsis, improved patient comfort, and more straightforward nursing care compared to other central venous access methods. However, mechanical complications such as artery puncture, pneumothorax, and hemothorax occur more frequently during subclavian vein catheterization compared to internal jugular vein catheterization. Numerous studies have demonstrated that ultrasound guidance enhances success rates and reduces the complication rate associated with central venous catheterization. All guidelines for venous access support this method, although it is not recommended explicitly for the subclavian vein. Only a small number of researchers have investigated the ultrasound-guided subclavian vein cannulation technique, finding that it improves the success rate and decreases the complication rate for both short-axis and long-axis procedures. However, there is limited data available on the use of ultrasound for subclavian vein cannulation in neurosurgical patients.

          Thus, this randomized controlled study aims to compare the use of ultrasound with the traditional landmark technique for infraclavicular approach of right-sided subclavian vein cannulation in adult patients undergoing general anesthesia for neurosurgical procedures.

MATERIALS AND METHODS

Following approval from the Institute Ethics Committee, 110 patients aged 18 to 60 years, admitted for elective neurosurgery at the Neuroscience Center, AIIMS, New Delhi, will be enrolled in this randomized trial. A written informed consent will be obtained from the eligible patient. This study will be registered in the Clinical Trials Registry of India.

Study Design – This will be a prospective, randomized, parallel-group trial.

Inclusion criteria

Adult patients aged 18 to 60 with ASA classification I and II who are undergoing general anesthesia for an elective neurosurgical procedure requiring subclavian vein catheterization will be included in this study.

Exclusion criteria

Patients will be excluded if they are

·         under 18 or over 60 years old

·         hemodynamically unstable or in shock-SBP less than 60 or on vasoactive drugs

·         experiencing an infection, inflammation, trauma, or hematoma at the cannulation site

·         having significant coagulopathy

·         suffering from morbid obesity BMI more than 40 kg per meter square.

Randomisation and grouping

            Randomization will be conducted by an independent individual not involved in the study, utilizing a computer-generated random number table. The allocation assignment will be sealed in an opaque envelope and opened just before the subclavian cannulation. Patients participating in this study will be randomized into two groups the ultrasound-guided technique and the Landmark method, in a 1 by 1 ratio. 

               The operators or anesthesiologists will remain unaware of the study’s aim, although closing their eyes to the method utilized is not feasible. Participants will be blinded to the randomization order and the technique used during the procedure. A separate observer will evaluate the outcome while remaining blinded to the study. A barrier will be placed between the outcome assessor and the operator.

Before the study commences, all participating residents and attending physicians will undergo a 30 minute tutorial on using bedside ultrasound for subclavian vein catheterization through an infraclavicular approach.

Anesthesia techniques

Following the establishment of intravenous access in the operating room, standard monitoring devices, including pulse oximetry, non-invasive blood pressure, and electrocardiography will be utilized. Anesthesia will be induced with propofol, and rocuronium will be administered to achieve neuromuscular blockade. The patient’s head will be turned to the left side while in the supine position. This study utilizes an ultrasound machine Sonosite M-Turbo or Edge II, Bothell, WA, USA equipped with a linear probe 6-13 MHz to capture images of the right subclavian vein SCV at the site of cannulation. The probe will be wrapped in a sterile sheet, and a sterile gel will be applied to it. The procedure site will be disinfected using 2 percent chlorhexidine and draped accordingly. Cannulations will be performed in the right subclavian vein using a 7 F 15 cm triple-lumen catheter by an anesthesiologist with a minimum of 50 USG-guided subclavian vein cannulations.

Ultrasound-guided techniques

We will use a freehand, real-time, single-operator method. The USG group will employ a longitudinal "in-plane" technique for the right-sided infraclavicular approach to subclavian venous cannulation. Preprocedural ultrasound scanning will assess the depth and caliber of the SCV, evaluate its patency, and identify adjacent structures. The subclavian vein can be visualized by placing a linear transducer in the infraclavicular fossa to obtain a short-axis view of both the vein and the artery. A short-axis view of the vein will be acquired initially, followed by rotating the probe while keeping the vessel centred on the screen, until the vein is visualized in the longitudinal view. The vein will be differentiated from the artery by its nonpulsatile nature and compressibility at the clavicular angle.

           The introducer needle will be inserted longitudinally at the midpoint of the transducer, directed at a 45-degree angle to achieve in-plane alignment. During needle insertion, the operator uses their non-dominant hand to stabilize the probe while guiding the needle with their dominant hand, ensuring precise advancement through the tissue and into the vein. The needle will be gradually advanced in real time along the longitudinal axis toward the vein’s lumen. The confirmation of the needle tip entering the vessel will be obtained by aspirating blood into the syringe. Once the needle tip is inserted into the subclavian vein, the operator will release the transducer while stabilizing the needle with their non-dominant hand and advancing the guide wire into the vessel using their dominant hand.  The needle will be removed, and the triple-lumen catheter will be placed using the Seldinger technique. Subsequently, the ipsilateral internal jugular vein and the contralateral subclavian vein will be examined to identify potential misplacements thus, the catheter may be adjusted using ultrasound guidance. The catheter’s position and any mechanical complications will be clinically assessed using chest radiography and, when applicable, ultrasonography.

Landmark techniques

In the Landmark group, an infraclavicular approach will be used, with the landmark points being the clavicle and the sternal notch. The introducer needle will be placed about 1 cm inferior and lateral to the intersection of the middle and medial thirds of the clavicle. The needle will be advanced with consistent aspiration on the attached syringe toward the sternal notch at the shallowest angle to access beneath the clavicle until it enters the subclavian vein. After establishing sufficient venous blood flow, the guidewire will be inserted. The needle will be removed, and the catheter will be inserted using the Seldinger technique, as previously described.

Data collection and Outcome measures

In the study, the prior experience of each participating physician with both traditional methods and ultrasound-guided techniques will be recorded.

The primary outcome will be the first-attempt success rate, defined as successful subclavian cannulation after a single skin pass of the needle.

The secondary outcome will consist of the following parameters

·         Overall success rate - The overall success rate is defined as the operator’s ability to insert the catheter into the subclavian vein within three attempts or 5 minutes. If three attempts at skin puncture fail, SCV catheterization will be considered a failure, and the internal jugular vein will be chosen for cannulation.

·         Number of attempts skin punctures - Defined as needle penetration of the skin.

·         Number of redirections - Described as withdrawing the needle slightly and changing direction without exiting the skin.

·         Cannulation time is defined as the duration from the start of insertion of the introducer needle to the return of venous blood into the attached syringe in both groups.

·         Procedural time refers to the duration from the initiation of the introducer needle insertion to the placement of the catheter in both groups.

·         The incidence of mechanical complications is defined as subclavian artery puncture, hematoma, pneumothorax, hemothorax, and catheter misplacement. A puncture of the subclavian artery will be identified by the strong, pulsating flow of bright red blood from the needle.

·         Technical difficulty score- Following ultrasound-guided catheterization, all physicians will assess the technical difficulty of the procedure using a semiquantitative scale that ranges from 0 to 10, where 0 signifies a simple procedure and 10 represents a complex one.

Statistical analysis

The sample size will be determined based on a randomized controlled trial comparing ultrasound-guided and Landmark methods for SCV cannulation. Kshirsagar et al. reported success rates of 92.5 percentage for the ultrasound group and 70 percentage for the landmark group on the first attempt. Assuming that 70 percentage of the subjects in the reference population possess the factor of interest, and with the application of continuity correction, the study requires a sample size of 55 for each group resulting in a total sample size of 110, given equal group sizes to achieve a power of 80 percentage for detecting a difference in proportions of 0.22 between the two groups test-reference group at a two-sided p-value of 0.05.

Categorical data will be reported as the number of patients and compared using the Pearson chi-square test or the Fisher exact test. Numerical data will be presented as the mean plus minus SD and compared using the independent Student t-test or the Mann-Whitney U test. The Shapiro-Wilk test will be used to assess the normality of continuous data. All analyses will be conducted at a significance level of 0.05. A two-tailed p-value less than 0.05 is considered statistically significant. The statistical analysis will be performed using STATA software.