Partial Scalp Block in Posterior Fossa Surgery

"Partial scalp blocks will be performed bilaterally after assuming the prone position.The Greater occipital will be blocked by injecting 3ml of local anaesthetic at a point half way between the mastoid process the external occipital protuberance along the superior nuchal line, medial to the occipital artery. The Lesser occipital nerve will be blocked by injecting 3ml of local anaesthetic infiltration along the superior nuchal line, 2.5 cm lateral to the greater occipital nerve block. The greater occipital nerve block also will cover the third occipital nerve due to the close location of the two nerves.~A placebo infusion (normal saline) will be administered at the same rate as fentanyl infusion in the active comparator arm(1 µg/kg/hr.)."

1µg/kg/hr. of intravenous fentanyl infusion will be administered. A syringe filled with 20 ml of normal saline will be prepared and 3 ml of normal saline will be injected at the same points of the partial scalp block previously described