Cephalic Spread of Block With Head Down Tilt in Spinal Anaesthesia - A Randomised Controlled Study

Subarachnoid block has become an established and reliable method of providing anaesthesia for lower abdominal and lower limb surgeries. A definitive advantage that subarachnoid block provides is the profound nerve block that can be produced in a large part of the body by the relatively simple injection of a small amount of local anaesthetic. Twenty-five factors have been invoked as determinants of the spread of local anaesthetic solutions in CSF. Among them, patient position is an important determining factor.

Operation theatre table tilts have been used to influence the spread of hyperbaric solution to ultimately influence the final height of the block. Studies have shown that a 10 degree head down tilt can result in cephalad spread of analgesia when compared to the horizontal group. So, in cases where the spinal block level was not high enough to perform a given surgery, the Trendelenburg position has been used to extend the level of the block. Hence, it is assumed that a higher level of block can be achieved with a smaller volume of the local anaesthetic agent, thus reducing the side effects. But others have noted that there was no statistically significant increase in the level of block even with 15 degree head down tilt.

In spite of this, anesthesiologists give various degrees of head down tilt which they believe is both safe for the patient and will result in adequate level of block. Often these are arbitrarily done by the operator as most of the operation theatre tables are not equipped with any device to measure the accurate degree of tilt.

An application called clinometer that utilizes the gyroscope sensor and determines the plane of the gadget in vertical as well as horizontal directions has been described. This application can be used to measure the exact degree of tilt given after sub arachnoid block.

As there is no agreement on the effect of Trendelenberg position on height of subarachnoid block, the current clinical study will be undertaken to estimate the effect of operation theatre table tilt at the time of lumbar puncture on the height of subarachnoid block.

Inclusion criteria

• Patients belonging to ASA physical status I and II undergoing lower abdominal and lower limb surgeries under spinal anaesthesia

Exclusion criteria

• Patient refusal
• contraindicated for spinal anaesthesia
• allergy to local anaesthetic agents used
• obesity (body mass index >29 kg/m2)
• Pregnancy