Dear Editor,Achieving a level of subarachnoid block (SAB) higher than surgical requirement is not uncommon in the practice of anesthesiology due to the multitude of factors affecting the spread of local anesthetics (LAs) in cerebrospinal fluid. Some of these factors are the characteristics of the injected solution, the technique employed, and patient characteristics.[1] However, a discernible variation in the spread of LA consequent to different characteristics of the needle tip has not been reported often.A 22-year old (weight 63kg, height 154 cm) primigravida at 23 weeks period of gestation had sustained flame burns 2 months back. The patient had sustained 2nd to 3rd degree burns over bilateral lower limbs, involving 25% to 30% of body surface area. After initial evaluation and stabilization, the patient was planned for split skin grafting of the raw area over bilateral lower limbs under SAB. The SAB administered and surgery was uneventful. One week later, the patient developed an abscess over the right lower limb and was given SAB in lateral position. SAB limited to one side of body was planned in the second instance since the surgery was limited to the right leg only. However, this time, the patient developed a high level of block with sensory block till thoracic-2 dermatome level. The high spinal block resulted in severe hypotension with a blood pressure of 74/54 to 60/40 mm Hg that required initiation of intravenous infusion of noradrenaline at 0.1 to 0.2 μg/kg/min (titrated to effect), which was tapered off once sensory level of SAB reached thoracic-12 dermatome level 2h after shifting the patient to post-anesthetic care unit. During both the procedures, the patient received 500 ml of preload with crystalloid and subarachnoid space was accessed via space between lumbar third and fourth vertebrae. Evident differences between the procedure for SAB during first and second occasion were the type of needle used (Quincke needle vs. Whitacre needle), patient positioning during SAB (Sitting vs.rightLateral), drug dose (12.5 mg Bupivacaine heavy vs. 7.5 mg Bupivacaine heavy), drug volume (2.5 ml Bupivacaine heavy vs. 1.5 ml Bupivacaine heavy), and timing of patient positioning to supine after drug injection (immediately vs. 15 min post-SAB injection), respectively.The literature search revealed that the width of pelvis is more than that of shoulder in females, thereby making lateral position practically equivalent to head down, and the same is also aggravated in pregnancy.[2] But Simin et al. reported that cephalic spread of drug with gravity in lateral position is highly unlikely in patient undergoing cesarean section.[3] Another randomized controlled trial by Bhat et al. revealed that position of administration of SAB in elderly patients has no effect on hemodynamic parameters or block characteristics.[4]In light of the above findings, it can be postulated that the use of Whitacre needle during second SAB can possibly be one of the determining factors for achieving unexpected high level of SAB. In a Whitacre needle, the exit stream is at 90°to the shaft of the needle, and if the direction of the orifice is pointing cranially, it can lead to more cephalad spread of LA. Quincke needle has a bevel, the direction of which does not affect the spread of LA as the stream of drug coming out is in the line of shaft of the needle.Technique factors need to be given due diligence, as the direction of an orifice of Whitacre needle can significantly impact the outcome of the SAB in spite of using a low volume of drug, as seen in our patient.
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