Comparison of Radial artery cannulation with Ultrasound guided Modified Dynamic Needle Positioning short axis approach versus Ultrasound guided combined axis approach. A Randomized controlled trial

Title

Comparison of Radial artery cannulation with Ultrasound guided Modified Dynamic Needle Positioning short axis approach versus Ultrasound guided combined axis approach. A Randomized controlled trial.

AIMS AND OBJECTIVES

Primary Objective: Comparison of First pass successful cannulation rate

Secondary Objectives : Time taken for cannulation, No. of skin punctures, Incidence of attempt failure, Incidence of “Positional arterial”, Hematoma, ischaemic complications

MATERIALS AND METHODS

Study Type: Prospective Randomized Interventional Study

Study Area: Department of Anaesthesiology, SGPGI

Expected Duration : 6 months

Study will be conducted after approval from the Institute’s ethical committee, CTRI Registration and obtaining written informed consent from the patients

Inclusion Criteria

All consenting ASA grade I, II, III patients aged 18 to 50 yrs. of either sex scheduled to undergo surgery under general anaesthesia requiring Radial artery cannulation for Invasive blood pressure monitoring.

Exclusion Criteria:

·       History of peripheral vascular disease

·       History of radial artery cannulation in past 15 days

·       History of surgery in wrist/ lower forearm area

·       BMI greater than 35

·       Negative Modified Allen’s test

·       Coagulation disorders

·       Awake radial artery cannulation

Randomisation: Computer generated randomisation

Allocation concealment: Opaque Envelope method

Methodology

After approval from IEC and CTRI and getting written and informed consent from all the patients prior to enrolment, a randomized control trial would be conducted. Upon patients’ arrival in operation theatre, standard ASA monitoring will be attached. After ensuring satisfactory vitals and monitor readings, patient will be induced as per routine anaesthesia protocol. Once patient mechanical ventilation is started and patient is hemodynamically stable, Radial artery cannulation will be done. Group allocation will be decided by opaque envelope brought by the patient. All radial artery cannulations will be done by a single anaesthesia consultant who is expert in both palpatory method and ultrasound guided methods. The choice of upper limb will depend upon the discretion of anaesthesia consultant if not dictated by needs of surgery or positioning. The arm will be placed on arm rest which will be abducted from body, a half litre saline bottle will be placed under wrist to ensure adequate dorsiflexion which will be secured by tape. Depending upon on the allocation, patient will be in one of the following groups.

Group USAX (Ultrasound guided Short axis approach) : Under strict aseptic precautions, Radial artery will be located near wrist with linear probe (5-15MHz) of USG Machine in short axis view with Linear probe placed perpendicular to axis of artery and skin at a depth of 1.5 mm. Probe will be manoeuvred with non-dominant hand till artery is in midpoint of sonographic view, which corresponds with black marking on probe. Cannula will be inserted with modified dynamic needle tip positioning technique. A 20 gauge Cannula with needle in situ will be inserted under sonographic guidance at 30 to 40 degree angle. Once the cannula needle tip will reaches centre of artery, the ultrasound probe will be gently moved up the forearm proximally till needle tip inside the artery vanishes. Needle tip would again be advanced in arterial lumen till it appears again in sonographic view. Above process will be repeated till whole cannula length is inside the artery. Stylet would be removed, pressure line will be attached. Cannula will be fixed with transparent dressing after confirming resistance free blood aspiration and proper arterial trace in monitor.

Group USCOM (Ultrasound guided Combined approach) Under strict aseptic precautions, Radial artery will be located near wrist with linear probe (5-15MHz) of USG Machine in short axis view with Linear probe placed perpendicular to axis of artery and skin at 1.5mm. Probe will be manoeuvred with non-dominant hand till artery is in midpoint of sonographic view, which corresponds with black marking on probe. A 20 gauge Cannula with needle in situ will be inserted under sonographic guidance at 30 to 40 degree angle. Once the needle tip reaches just above the artery, Probe will be longitudinally aligned with axis of artery and artery would be imaged in long axis. After confirming the needle tip position above the anterior wall of artery, cannula will be threaded into the artery under long axis sonographic view.

Cannula will be fixed with transparent dressing after confirming resistance free blood aspiration and proper arterial trace in monitor.

Post-surgery all patients will be followed up in postoperative period  for five days for any Hematoma or ischaemic distal limb complications.

Outcome Assessment

Primary Outcome: First pass successful cannulation rate. Successful cannulation will be defined as free aspiration of blood and good arterial trace from arterial line. If artery is cannulated successfully in a single prick it will be defined as Successful first pass cannulation

Secondary Outcomes:

·       Time taken for cannulation. It is defined as time elapsed from first skin prick to adequate arterial line trace

·       No. of skin punctures

·       Incidence of attempt failure. Attempt failure will be recorded if limb of insertion is changed.

·       Incidence of “Positional arterial”. It is defined as arterial line whose trace gets distorted with slight change in wrist position. This is will be assessed immediately post fixation.

·       Hematoma

·       Ischaemic complications

Sample Size Estimation

Since there are no prior similar studies, hence based on our pilot study of 20 patients (10 for each group) , first pass successful cannulation rate was 90 % and 70 % for USAX group and USCOM group respectively. Thus to detect a difference of 20 % in first pass cannulation in two equal sized groups, with 80 % power and 5% type 1 error with two tailed test with sample size of 69 was computed for each group. Thus study will include 150 patients.

Statistical analysis

Normality of the continuous variables will be assessed. Descriptive statistics of the continuous variables will be presented as mean± standard deviation /median (interquartile range) as appropriate while categorical data in frequency and percentage. Students t test or its non- parametric method to be used to compare the means or medians whereas Chi square test/ Fisher exact test will be used to compare the proportions between two groups. Two-way Repeated measures ANOVA or Liner mixed model to be used to test the association of the interventions (study groups) and change in the Measurements . A p value < 0.05 will be considered statistically significant.