Optimal Positioning of Local Anaesthetic in Femoral Nerve Block Prior to Hip Surgery

Optimal Positioning of Local Anaesthetic in Femoral Nerve Block Prior to Operative Fixation of Fractured Neck of Femur

The aim of the study is to compare patient comfort and analgesic efficacy of ultrasound guided femoral nerve block using the following endpoints: circumferential spread, anterior or posterior local anaesthetic deposition prior to positioning for spinal anaesthesia for operative fixation of fractured neck of femur.

Fractured neck of femur is a common cause of admission to hospital in elderly patients and requires operative fixation. The recommended anaesthetic technique for these cases is spinal anaesthesia, which is performed with the patient in lateral decubitus. Positioning the patient prior to administering spinal anaesthesia is the most painful manouvre due to the movement of the fractured bone.

Regional anaesthesia is effective in alleviating pain due to trauma, and it has the advantage of producing localized but complete pain relief (1). Femoral nerve blockade prior to positioning for spinal anaesthesia provides excellent pain relief and is a well tolerated procedure (2-5).

Using ultrasound guided femoral nerve block is a relative new method to improving the block success rate. It is widely used in our hospital. In a recent study Casati and al. showed a 42 % decrease of ED50% using ultrasound for localization of the femoral nerve (6). In a recent editorial by Brian D. Sites was mentioned that the positioning of the local anaesthetic in ultrasound guided blocks is unclear (7). We currently follow different patterns in relation to injection of the local anaesthetic solution around the femoral nerve. One of them is a circumferencial spread around the nerve. This, however, needs several needle passes which are likely to be painful for the patient. Another option is injecting the local anaesthetic on one side, above or below the nerve without changing the position of the tip of the needle, avoiding patient discomfort. Whether this results in a comparable quality of sensory block is unknown. The femoral nerve is separated in branches at this level and we assume that the spread of local anaesthetic may influence the quality and the distribution of the block. We propose to study the characteristics of femoral nerve block in relation to different patterns of local anaesthetic injection (circumferencial, inferior or superior).

Inclusion Criteria:

• Fractured neck of femur surgical fixation performed under spinal anaesthesia
• ASA I to III

Exclusion Criteria:

• Patient refusal
• Coagulation disorders
• Head injury or other associated injuries
• Previous vascular surgery in the femoral area.
• Loss of consciousness and signs of acute coronary syndrome
• Mini-Mental Score < 25 (see appendix 3)
• Allergy to lignocaine,
• Skin lesions/infection at site of injection
• Sepsis