Minimum Effective Intrathecal Dose of Local Anaesthetic With Fentanyl for Fractured Neck of Femur(Dose Finding Study).

Determination of the Initial Minimum Effective Dose of 0.5% Bupivacaine With 20mcg of Fentanyl Via a Spinal Catheter for Operative Fixation of Fractured Neck of Femur.

Fractured neck of femur (FNF) is a common cause of admission to hospital in elderly patients with multiple comorbidities. Anaesthetic management of this patient group is extremely challenging.Neuraxial anaesthesia with minimum doses of local anaesthetic agents administered via a spinal catheter leads to better cardiovascular stability.The minimum dose of local anaesthetic with intrathecal fentanyl was not established yet.We propose to study and determine the initial minimum local anaesthetic dose (MLAD) of 0.5% bupivacaine with 20 mcg of fentanyl administered via a spinal catheter to achieve a sensory block up to T10 for the operative fixation of FNF.We will use a previously well established Dixon and Massey "up-and-down method" to calculate initial MLAD in this prospective, observational trial.

Objectives: We would like to determine the initial MLAD of 0.5% bupivacaine with 20mcg of fentanyl administered via a spinal catheter required to achieve a sensory block up to T10 on the side of FNF.

Outcomes

Primary outcome:

1. Initial MLAD of 0.5% bupivacaine with 20mcg of fentanyl required for a sensory block up to T10 on the side of FNF.

   Secondary outcomes:

2. Total dose of 0.5% bupivacaine with 20mcg of fentanyl required for the operative fixation of fractured neck of femur.

3. The effect on haemodynamic variables (blood pressure, heart rate).

4. Incidence of side effects

5. The length of postoperative analgesia (the time from the last dose of local anaesthetic administered intrathecally to VAS>3).

6. The time to first rescue analgesic requirement

Study Design Prospective, observational trial.

Study Size Based on the previously well established Dixon and Massey "up-and-down method"(10), we will recruit patients until a successful spinal block has been achieved in six consecutive patients who received a specific dose. This is the requirement to calculate the initial MLAD.

Inclusion Criteria:

• fractured neck of femur
• Above 60 years
• American Society of Anesthetists(ASA) I to III

Exclusion Criteria:

• Patient refusal
• Outside Age Range
• Contraindications to spinal anaesthesia
• Head injury or other associated injuries
• Loss of consciousness and signs of acute coronary syndrome
• Mini-Mental Score < 25 (Appendix 2)
• Allergy to bupivacaine, lignocaine or fentanyl