Preprocedural ultrasonography versus landmark guided technique for lumbar epidural anaesthesia in geriatric patients : a randomized controlled trial

This study will be conducted in Department of Anesthesiology of Sri Manakula Vinayagar Medical College and Hospital, a tertiary hospital in South India. The study design is a Randomized controlled trial. Patients who meet the inclusion criteria will be included in the study. All the eligible participants will be explained about the nature of the study and procedure. A written informed consent will be taken from them. After obtaining informed consent, pre-anesthetic assessment will be carried out for all participants on the day before surgery. All patients will be premedicated with T.Pantoprazole 40 mg orally on the night before surgery. All participants will be kept nil per oral with 6 hours for solids and 2 hours for liquids before the day of surgery. Patient’s demographic data like age, sex, height, weight, BMI will be recorded. On the day of surgery, patients in both groups are taken to the operating room and underwent standard monitoring like ECG, pulse oximetry, NIBP, and intravenous access is established. In Group B, epidural analgesia is performed using the conventional surface anatomic landmark guided technique. With the patients in sitting position, a line joining the two iliac crests (Tuffier’s line) is palpated and used to determine the vertebral level of L4. And the most appropriate entry site is determined by palpating the spinous process and marked. The landmark identification is confirmed by the attending anesthesiologist and was graded according to the palpation difficulty score as 0, 1, 2 and 3.8 Score 0: Spinous processes can be palpated, and the interspinous spaces are evident. Score 1: Spinous processes can be palpated, and interspinous spaces are not evident. Score 2: Spinous processes cannot be palpated, interspinous spaces arenot evident, and vertebral column can be palpated on the midline or outside the midline, Score 3: Spinous processes cannot be palpated, interspinous spaces are not evident, and vertebral column cannot be palpated. After ensuring sterile conditions, epidural catheter is placed at the marked point using an 18-gauge Tuohy’s needle. In group A, epidural analgesia is performed using the ultrasound guided technique. A curved array low frequency (3-5 MHz) is used for systematic screening of the spine. The ultrasonography is performed in the 9 sitting position for the epidural needle placement. Ultrasound imaging of the lumbar spine is performed by the trained anesthesiologist. And the following points are obtained during pre-procedural ultrasound scanning, • The interspace level. • The midline of the spine. • The puncture point. • The angle of needle insertion. • The depth to the epidural space. The probe is placed longitudinally along the spine parallel to it, 2-3 cm lateral to the midline, at the level of sacrum and directing it towards the center of the spinal canal. With this paramedian longitudinal view, multiple levels can be visualized in one scanned image. The sono-anatomical structures that can be seen in this plane include,

1. sacrum
2. lamina
3. ligamentum flavum and dorsal dura mater- Anterior complex.
4. ventral dura mater, posterior longitudinal ligament and vertebral body – Posterior complex. Then the ultrasound transducer is moved cephalad using the sacral level as a starting point. The upper border of the sacrum can be identified as a hyperechoic flat reflective surface on the ultrasound image at about 3–5 cm under the skin. As the transducer is advanced cephalad, the interspace can be identified as an indentation of the reflective surface, followed by a ‘‘saw-tooth’’ pattern representing the lamina interrupted by interspaces. Each interspace consists of two parallel hyperechoic bands (equal sign), with the anterior complex as the outer band and the posterior complex as the deeper one. The desired interspinous level is identified by counting the alternating laminae and the corresponding interspaces. The midpoint of the interspace is determined by centering a particular interspace on the screen. With the transducer kept still, a line is drawn in the skin at the center of lateral aspects of the transducer. Then the transducer is placed horizontally in the same site centering the interarticular joint in the screen, a vertical line is drawn from the center of upper aspect of the transducer. The transducer is then removed, and lines are drawn to connect these marks. The insertion point is determined by the intersection of these two lines. 10 The angle at which the anterior and posterior complex were best visualized is considered as the optimal angle for needle insertion. The angle of insertion will be measured using a smartphone based digital protractor app. After ensuring sterile conditions, epidural catheter is secured at the intersection point using a 18-gauge Tuohy’s needle. The primary outcome in this study is to calculate and compare the total procedure time required for epidural needle placement in both the groups. The total procedure time is defined as, the time taken from the start of epidural needle contact with the skin to successful placement of the epidural needle, which is confirmed by a feel of sudden loss of resistance as the needle enters the epidural space. Followed by advancement of catheter smoothly without resistance, with free flow of test dose through the catheter, with stable hemodynamic status after giving test dose indicates successful epidural catheter placement.

In addition to this, the number of needle insertion attempts (Number of times the needle is inserted through the skin), number of needle redirections (Number of times needle is redirected without withdrawing fully) and complications like accidental dural puncture, vascular puncture following epidural catheter placement is assessed. Epidural analgesic effect is also assessed, after extubating in case of combined epidural with general anesthesia and after weaning off of spinal anesthetic drug effect in case of combined spinal – epidural anesthesia using Visual analog score ranging between 1 to 10. Patients will be shifted to post operative ward. Postoperative epidural analgesic effect is assessed at 2-hour, 4-hour, 6-hour and 8-hour. All data obtained in the study were analyzed and recorded by an independent observer.