Objectives
Effective analgesia after total knee arthroplasty (TKA) improves
patient satisfaction, mobility and expedites discharge. This study
assessed whether continuous femoral nerve infusion (CFNI) was superior
to a single-shot femoral nerve block in primary TKA surgery completed
under subarachnoid blockade including morphine.
Methods
We performed an adequately powered, prospective, randomised,
placebo-controlled trial comparing CFNI of 0.125% bupivacaine versus normal
saline following a single-shot femoral nerve block and subarachnoid
anaesthesia with intrathecal morphine for primary TKA. Patients
were randomised to either treatment (CFNI 0 ml to 10 ml/h 0.125%
bupivacaine) or placebo (CFNI 0 ml to 10 ml/h normal saline). Both
groups received a single-shot femoral nerve block (0.25% 20 ml bupivacaine)
prior to placement of femoral nerve catheter and subarachnoid anaesthesia with
intrathecal morphine. All patients had a standardised analgesic
protocol. The primary end point was post-operative visual analogue
scale (VAS) pain score over 72 hours post-surgery. Secondary outcomes
were morphine equivalent dose, range of movement, side effects,
and length of stay.
