Comparison of ultrasound andlandmark technique for subarachnoid block in caesarean section

The subarachnoid block is asafe and effective alternative to general anaesthesia when the surgical site is on the lower abdomen, perineum, or lower extremities. Spinal anaesthesia is  the preferred regional technique for caesarean sectiondue to its ease of administration with a highsuccess rate and rapid onset of anaesthesia. Spinal anaesthesia for caesareansection is commonly delivered using the traditional landmark technique where we palpate bony anatomical landmarks i.e the iliac crests and spinous processes to locate the L4-L5 intervertebral space.

 Theproposed ideal site for spinal anaesthesia is below the Conus medullaris. Inadults, Conus  medullaris ends at the lower border of the body of L1vertebrae in the majority of the population. It has been reportedthat there is an increased incidence of neurological trauma followingspinal anaesthesia if performed at the vertebral level where conus medullarisends. Neurological trauma is seen more in the obstetric population due tothe variation in normal anatomy that occurs during pregnancy. Variationsin the normal anatomy of thevertebral column in pregnancy can also make it difficult for anaesthesiologists in locating the intervertebral space.The physical changes that occur in pregnancy are-

1)Lumbar lordosis

2)Rotation ofpelvis to the long axis of thespinal column

3)Weight gain

All of the above would leadto difficulty in estimation of intervertebral space via landmark technique. The advantages of ultrasound guidance overconventional techniques include the ability to bothview the targeted structure and visualize, in real-time the distribution of theinjected medication, and thecapacity to control its distribution by readjusting the needle position if needed. USG guidance should plausiblyimprove the success rate of the procedures, their safety and speed. For locating the L4 L5 intervertebral space, USG of the spine appears to help increase the success of the subarachnoid block. It isnon-invasive and hence will be safe for pregnant women, radiation-free and known to her from early on in pregnancy. In this study, we are going toassess if a USG-assisted technique could reduce the time taken for theprocedure, number of needle passes required for identifying subarachnoidspace and if there is any correlation withpost- dural puncture headache using the USG technique when compared to landmark guided  technique inpregnant women.

 After approval from the Institutional Ethics committee and with informed and written consent, pregnant women who willundergo landmark guided technique will be considered as group L and the ones who will undergo ultrasound-guidedtechnique will be considered as groupU.

Procedure-related definitions are given below:

1.Preparation time: thetime taken by the anaesthesiologist from palpation the of iliac crest orplacement of ultrasound probe over the back till the needle insertion.

2.Procedural time: the timetaken from the insertion of the spinal needle until the free flow of CSF

3.Success rate: ObtainingCSF flow.

4.Attempts: insertion of aspinal needle into the skin

5.Passes: redirecting thespinal needle in the same space or different space without exiting the skin.

6. Patientsatisfaction score: At the end of the surgery, patients will be queried forsatisfaction and made to mark intraoperative anaesthetic satisfaction on afour-point Likert scale (1 – Not satisfactory, 2 – Satisfactory, 3 – Good, 4 –Excellent) based on the number of needle pricks, pain at the site of injection,intraoperative analgesia, and sedation

7. Post dural punctureheadache: Bilateral frontal or occipital headache that is worse in theupright position, along with nausea, neck pain, dizziness, visual changes,tinnitus, hearing loss, or radicular symptoms in the arms.

8.Distancefromthe skin to subarachnoid space- measurement of the distance from the skin tothe ventral border posterior complex on the ultrasound or length of the needleinside the body on successful attempt as measured using a scale after spinalanaesthesia

Standardfasting protocols will be followed in all the patients. Intravenous cannulationwill be  established andoral premedication with a tab. Pantoprazole 40mg would be given on the previous day and before the procedure. Patients would then be shifted to the operating room  inthe left lateral position. Inside the operation theatre, standard monitoring inthe form of non-invasive bloodpressure, electrocardiogram, and pulse oximetry will be instituted and the baseline parameters will be recorded.All participants, after noting down baseline parameters, will be made to lie in the left lateral decubitus position,in group L under aseptic precautions L3-L4 or L4-L5intervertebral space will be identified using the landmark technique bypalpating the space thatcorresponds to Tuffier’s line, and in this space, local infiltration will begiven, after this spinalanaesthesia will be administered. In group U, a sterile cover will be appliedto the curvilinear USG probe. A parasagittal view of the spine will be obtained, and then the L3–L4intervertebral space will be identified by moving up from the sacrum below. Atthis selected L3–L4intervertebral space, the probe position will be changed to a transverse viewand brought to the midline.After identifying the L3–L4 space, the best image of the anterior complex and posterior complex will beobtained, and a sterile surgical skin marker will be used to mark the midpoint of the long and short borders ofthe probe in the midline. The point of intersection between the twoperpendicular lines will be identified as the point of entry. Then local infiltration and spinal anaesthesia will be given at the marked point. Conventionallytrained anaesthesiologists who are experienced in identifying posterior cord structures using ultrasound will beperforming the procedure. In both groups, the procedural time, preparation time, numberof attempts in the same space and different spaces,number of passes, distance of subarachnoid space from the skin, patientsatisfaction score will bemeasured. The dosage of localanaesthetic will be kept standard between the groups as 10mg of 0.5% hyperbaric Bupivacaine. In bothgroups, the primary outcome will be the success rate. The secondary outcomes will be thetime taken to administer spinal anaesthesia,the distance from the skin to subarachnoid space, patient satisfaction and occurrence of post-dural puncture headache. At the end of the surgery, patients will be queried for satisfaction and made to mark intraoperative anaesthetic satisfactionon a four-point Likert scale. Patients will be followed up for 7 days, ifpatient is discharged before completion of 7 days, a follow up till the 7th day will be done via telephone.