How to achieve optimal position for central neuraxial blocks in patients with lower limb fractures?

Sir,

Central neuraxial blocks (CNBs) are the mainstay in the anesthetic management of lower limb fractures. Optimal position for performing CNBs requires ≥ 90° hip flexion along with flexion of the spine to increase the width of the lumbar interspinous space. When CNB is performed in the sitting position, the patient's thighs are usually at an angle of approximately 90° to the trunk.[1] In patients with lower limb fractures, positioning for CNBs is a difficult task because of pain, deformity and the presence of splint/traction etc. and CNBs are often performed with the patient in sitting position. Systemic analgesia or regional nerve blocks have been successfully used to increase the patient comfort level while performing CNBs in such patients.[2] Some of these patients can be administered CNBs in lateral position with hip flexion only on the non-operative side. In spite of the best efforts, the final position achieved is often suboptimal. The patient's trunk is placed approximately 60° or less to the horizontal. This effectively results in less working space for the anesthesiologist and an acute angle of entry of the needle. This position might result in pain, discomfort, difficulty in maintaining patient position and fatigue in the patient as well as the anesthesiologist, unexpected patient movement and procedure related complications like accidental dural puncture.

A simple manoeuvre of the table can solve these difficulties and increase the comfort level of both, the patient and the anesthesiologist. First, the operating table is inclined to approximately 30° reverse trendelenburg position [Figure 1a]. With the support of an assistant, the patient is made to sit with trunk approximately 60° to the horizontal and buttocks close to the break-point of the table. Now, the cephalad half of the table is broken downwards to about 30-45° to the horizontal [Figure 1b]. This effectively achieves an angle of ≥90° between the patient's back and the table surface, resulting in more working space for the anesthesiologist with less discomfort to the patient. In this final position, the patient's trunk is vertical on the table leading to less fatigue. The skeletal traction can also be maintained during the procedure to increase the comfort level of the patient. An alternative is to pull the patient up to the edge of the head-end of the table after making the patient sit-up. However, this does not take care of the patient comfort while the anesthesiologist's comfort levels are high.

Figure 1

(a) Approximately 30° reverse trendelenburg position of the operating table, (b) cephalad half of the table is broken downwards to about 30-45° to the horizontal, (c) anesthesiologist performing neuraxial anesthesia

However, it should be noted that the positioning technique described here is not a substitute for administration of a nerve block or systemic analgesics prior to positioning the patient to increase the comfort level. An assistant should be holding the patient all the time during the procedure to ensure the patient safety. The anesthesiologist still has to approach the patient from the side or from the head end. The anesthesiologists should also be cautious not to make the reverse trendelenburg tilt of the table too steep lest the patient slide down the table.