With the approval of the Clinical Research Ethics Committee of the Cork Teaching Hospitals (ECM 4 (zz) 08/12/09.) and having registered the trial at ClinicalTrials.gov (NCT01527812), a prospective, double blinded, randomized study of patients undergoing operative fixation of FNF at the Cork University Hospital was undertaken between December 2009 and November 2011. The patients were randomly allocated using a random number sequence and sealed envelopes. Written, informed consent was obtained from each patient.
Patients with FNF, American Society of Anesthesiologists grades I to III and aged >50 years, were invited to participate in the study. Exclusion criteria were patient refusal, the presence of more than one fracture; Mini-Mental Score <22 (Additional file 1); coagulation disorders; head injury; history of loss of consciousness; acute heart failure; allergy to lidocaine; skin lesions/infection at block site; and renal dysfunction. Patients with evidence of systemic infections (clinically defined or elevated C-reactive protein levels, leucocytosis, or body temperature higher than 37.8°C) were also excluded.
In all patients, an experienced anesthetist performed the ultrasound guided FNB. A 5 cm, 6–13 MHz linear transducer probe (Sonosite Turbo M, Bothwell WA, USA) was used to locate the nerve. For optimal visualization of the femoral nerve the transducer was applied transversely to the thigh below the inguinal crest. After examination of the anatomy of the femoral artery, the femoral nerve was identified at a level immediately above the deep femoral artery branch bifurcation. A 22 G 50 mm Stimuplex BBraun needle was used. After identification of the nerve and fascia around the nerve, the skin was infiltrated with local anesthetic ( 0.2 ml lidocaine 1%) on the lateral aspect of the thigh, 1 cm lateral to the lateral edge of the transducer. The needle was inserted in-plane from lateral to medial and advanced toward the lateral aspect of the femoral nerve.
For all patients, lidocaine 2% 15 ml was administered to perform ultrasound guided FNB. We used lidocaine, because it had a short onset time and our aim it was to facilitate positioning for performing spinal anesthesia in the shortest time. For patients allocated to the “Above” group (Group A) the LA was injected below (i.e. deep to) the fascia iliaca and above (i.e. superficial to) the femoral nerve; for patients allocated to the “below” group (Group B), the LA was injected below the femoral nerve and above the fascia of the iliopsoas muscle and for those patients allocated to the circumferential group (Group C), circumferential spread was achieved with multiple injections around the nerve (Figure 1).
An independent blinded observer (not present during performance of the block) assessed the extent and degree of sensory blockade using a modified Bromage score (cold, mildly cold and just spray) at 5 minute intervals during the initial 30 minutes after block completion. Sensory perception was assessed using cold (ethyl-chloride spray) spray on the skin in the lateral, frontal, medial side of the thigh and medial side of the leg corresponding to common distributions of the terminal branches of the femoral nerve.
Our primary outcome parameter was pain, evaluated using verbal rating (VRS) pain score (0–10) immediately after positioning the patient (lateral decubitus with operative side superior/independent) for spinal anesthesia.
We recorded each patient’s pain (also using a VRS pain score 0–10) on passive movement of the fractured limb (elevating up to 30 degrees from the supine position or to patient tolerance from the resting position). When the patient reported VRS < 4 during the passive movement of the limb, the sensory block was deemed adequate and the patient was positioned for spinal anesthesia. In the event that cold perception was still present, assessment was continued up to 30 minutes after block completion (if the spinal is not injected until this time). Block failure was defined as failure to achieve a VRS score of < 4 within 30 minutes of FNB completion. In these cases, additional opioid medication and/or sedation were administered in order to optimize positioning for spinal anesthesia and these patients were excluded from further data collection.
We recorded the times at which the patients arrived in the anesthetic induction room, ultrasound-guided FNB started (i.e. skin infiltration with LA) and completion of patient positioning for spinal anesthesia.
Spinal anesthesia was performed using standard aseptic technique; isobaric bupivacaine 0.5% were administered at a dose indicated by the responsible clinician. Patient satisfaction was assessed using a 100 mm linear visual analogue scale (VAS) during the surgical procedure and immediately after arriving to the recovery area. Patients were also asked in the recovery area if, given the option, they would choose the same analgesic modality again.
Untoward or adverse events were recorded by the responsible clinician (anesthetist) on a dedicated data sheet.